Post on 25-Jan-2023
CEJC 2(1) 2004 1633
Aerogel nanoscale magnesium oxides as a destructivesorbent for toxic chemical agents
Vaclav middotStengl1curren Snejana Bakardjieva1 Monika Mamiddotrparasup3kovparaa1 Jan middotSubrt1Frantimiddotsek Oplumiddotstil2 Marcela Olmiddotsanskparaa2
1 Institute of Inorganic ChemistryAS CR
250 68 middotRemiddotz Czech Republic2 Military Technical Institute of Protection Brno
Veslamiddotrskparaa 230 628 00 BrnoCzech Republic
Received 21 August 2003 accepted 16 October 2003
Abstract An autoclave hypercritical drying procedure has been used to prepare precursors of
MgO from Mg(OCH3)2 This material was prepared with a specishy c surface area of 1200 m2g1
The dehydrated materials consisted of much smaller crystallites than conventionally prepared
MgO and were free of OCH3 groups The precursors and samples of magnesium oxide were
taken for experimental evaluation of their reactivity with mustard The largest percentage of
the conversion mustard into non-toxic products after the elapse of the reaction was 77
creg Central European Science Journals All rights reserved
Keywords Nanostructures organometallic compounds chemical synthesis electron microscopy
surface properties
1 Introduction
Nanosized inorganic oxides are regarded as promising non-aggressive reagents useable for
the treatment of sensitive materials contaminated with lethally toxic chemical agents
namely the nerve agents (sarin soman VX agent etc) as well as blistering agents (eg
mustard) The detoximacrcation capability of those highly dispersed oxides (eg MgO CaO
ZnO AlOx(HO)y ZrO TiO2) has been extensively studied and reported [1-5] Products
of corresponding reactions have been investigated and the respective detoximacrcation re-
action mechanisms have already been proposed The detoximacrcation reactions have been
curren E-mail stengliiccascz
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 17
shown to proceed mainly on the surface of the nanoparticles leading to non-toxic products
even at ambient temperature
Reactivity of the nanosized MgO towards the toxic agents has been described more
profoundly by Wagner et al [4] The following basic knowledge has been revealed
All mentioned toxic agents can be detoximacred ie converted into their non-toxic
products within a reasonable time period so that the activity of the reagent is
versatile
The chemical activity of the MgO surface cannot be considered uniform but the
more active centres are preferentially located at activated sites or defects along the
surface of the nanoparticles eg edges corners etc
Heterogeneous reactions of the respective neat toxic agents exhibit two-stage kinetics
when proceeded on the MgO nanoparticle surface The initial fast stage can be
attributed to the reaction of a given agent at highly active reaction centres and
the second stage is explained as a process of slower transport of the agent along
surface from less active site(s) to more reactive one(s) The process of a secondary
redistribution of the neat agent over a surface was convincingly correlated with the
respective evaporation rate (agent vapour pressure) as to be a rate-limiting factor
The main aims of the work were
To investigate the respective method and procedure of preparation of the nanosized
magnesium oxide
Characterise the respective synthesised magnesium oxide samples
Evaluate the prepared oxides for their respective detoximacrcation activities
Assess whether the overall activity of the prepared oxides could be increased utilising
an eregective solvent which is potentially more capable of distributing the toxic agent
over the whole surface of the oxide
Magnesium oxide is commonly obtained by thermal decomposition of magnesium hy-
droxide or carbonate [6] [7] and more recently by a sol-gel process [8] [9] The oxide
morphology particle size and specimacrc surface area depend on the preparation conditions
(pH gelling agent calcinations rate and temperature) It has been documented that
methoxide or alkoxide-based solgel synthesis of metal hydroxides followed by supercrit-
ical drying and vacuum dehydration can lead to the formation of nanoparticles of metal
oxides [10-15]
In considering the ways in how to additionally facilitate the respective detoximacrcation
reaction the two following approaches may be proposed to stimulate the overall course
of the reaction namely
The initial uniform spreading of the agent over the whole surface
A degow of the agent along the surface
Since the capillarity of the toxic agents is limited the agent distribution over the surface
of the solid (powdery) reagent could be enhanced utilising a solvent that is capable of
both dissolving the toxic agent and wetting the powdery reagent surface thus penetrating
its whole deposit and spreading there evenly Moreover if the chosen solvent is volatile
enough it evaporates at the upper layers causing a slow but benemacrcial degux of the solvent
18 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
containing the dissolved toxic agent which passes from bulk up to surface of the reagent
deposit (batch)
The detoximacrcation activities of the prepared samples of magnesium oxides and mag-
nesium hydroxides (ie precursors of macrnal nanosized MgO syntheses were evaluated using
sulphur mustard bis(2-chloroethyl) sulphide The agent was chosen deliberately for the
experiments because it has been reported to be relatively resistant to detoximacrcation [4]
When it is brought together with the nanosized MgO it can yield 2-chlorethyl vinyl sul-
phide and divinyl sulphide both of which are products of an elimination reaction and
the thiodiglycol a product of a nucleophilic substitution reaction
2 Experimental section
21 Preparation of nanoscale magnesium oxide
A modimacred autoclave hypercritical procedure has been developed to prepare nanoscale
MgO particles This method has four steps preparation of Mg(OCH3)2 by the reaction
of magnesium metal with methanol hydrolysis of Mg(OCH3)2 in the presence of toluene
hypercritical drying in an autoclave and thermal activation Commercially available
Mg(OCH3)2 solution (Aldrich 6 wt in methanol) were used in lieu of macrrst step The
experimental conditions are summarised in Table 1 Ultrasound waves [16] were used
for hydrolysis of Mg(OCH3)2 The hydroxide gel solution was transferred into a 100 ml
stainless-steel autoclave After nitrogen gas degushing the autoclave was slowly heated from
room temperature to 265plusmnC at a rate of 3plusmnCmin by the PID controller The temperature
was allowed to equilibrate at 265plusmnC for 15 min The autoclave was vented to release the
pressure which took about 05 1 min The autoclave was immediately removed from
the oven and cooled to room temperature The product was removed from the autoclave
and dried at 120plusmnC The macrnal product was stored in a bottle under normal conditions
On the basis of DTA results (Figure 1) the hydrated MgO precursors obtained from the
autoclave were heated under dynamic vacuum by using a furnace controlled by the PID
controller in a stainless steel tube The temperature ramp was 1plusmnCmin After the heat
treatment the sample was allowed to cool to room temperature
22 Characterization methods
The specimacrc surface area of the samples was determined via nitrogen adsorption-desorptions
isotherms at liquid nitrogen temperature by using a Coulter SA 3100 instrument TEM
micrographs were obtained using Philips 201 transmission electron microscope SEM pho-
tographs were obtained using Philips XL30 CP scanning electron microscope and X-ray
powder diregraction was performed with Siemens D5005 diregractometer Qualitative analy-
sis was performed with Bede ZDS for Windows version 199 and JCPDS PDF-2database
[17] DTA-TG measurements were carried out using NETZSCH STA 409 apparatus
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 19
23 Methodic of disintegrations mustard
Nanosized magnesium samples (precursors Mg(OH)2 as well as magnesium oxides) were
evaluated for their ability to convert sulphur mustard (hereafter also signed as HD) into
non-toxic products Synthesised powdery samples were dried over 24 hours in a vacuum
kiln (at 100 plusmnC 400 Pa) before tests A weighed portion of a given evaluated nanosized
sample was put into a glass vial provided with a solid screw cap (Supelco type CRS-33)
The toxic agent in a solution of a chosen solvent was dosed onto the powder reagent
layer The vial was sealed with a cap and placed into the thermostat All experiments
were performed at 25plusmnC and each run was repeated four to six times An addition of
isopropylalcohol (ca 2 mL) terminated the reaction The suspension was vigorously
agitated and the liquid fraction was separated from the solid using a centrifuge (9 000
cc miniexcl1 for 3 minutes) and subsequently analysed for a residual content of the mus-
tard The respective detoximacrcation capabilities of the evaluated nanosized samples were
expressed as percentages of mustard elimination from the reaction mixture under given
experimental conditions
3 Results and discussion
31 Characterization of samples magnesium aerogels
Figure 1 shows a typical thermal analysis of the precursors used in the synthesis Water
evolution started at a low temperature (sup1 100plusmnC) with a maximum at 139plusmnC Carbon
dioxide and water from the decomposition of residual OCH3 groups was detected in
the gas phase at sup1 300plusmnC and peaked at 396plusmnC The calcination temperature used in the
synthesis was 500plusmnC At this temperature the macrnal solids obtained were found to consist
primarily of particles of MgO without any traces of precursors The specimacrc surface area
and total pore volume are shown in Table 1 and Table 2 The specimacrc surface area de-
creases with increasing temperature of the annealing of precursors Figure 2 shows the
X-ray diregraction patterns of the precursor Mg151 and the samples prepared by their
thermal treatment They are all similar and exhibit three characteristic peaks for MgO
(periclas PDF 45-0496) With increasing annealing temperature the intensity of the
peaks has been evolved No diregraction lines of Mg(OH)2 were detected Electron mi-
crographs of the selected samples are shown in Figure 3 (TEM micrographs) Precursor
particles (sample Mg151) have uniform morphology and particle size as periclase par-
ticles (samples Mg152-156) The particle size from electron micrographs is similar to
that of the calculated size from X-ray diregraction (see Table 2) The Scherrer equation
was applied to estimate a crystallite size and a programme WinFit v12 was used for
calculation of particle size
20 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
32 The reactivity towards sulphur mustard
Two precursors Mg(OH)2 with high specimacrc surface areas (Mg 151 and Mg 252) and
three diregerent samples of magnesium oxide (Mg 151380 Mg 16380 Mg 252380)
were taken for experimental evaluation of their respective reactivities
The eregect of the solvent type used on the course of the detoximacrcation reaction was also
tested Five solvents diregering in their basic chemical properties (eg polarity proticity
viscosity capillarity and volatility) were taken for the experiment as follows
deg petrolether - non-polar distinct capillarity highly volatile
deg diethylether - non-polar aprotic oxygen-containing distinct capillarity highly volatile
deg acetone - weakly polar aprotic distinct capillarity volatile
deg N N-dimethylpyrrolidone - polar aprotic
deg methylalcohol - protic
The eregect of the solvent type on detoximacrcation reaction was only tested with the MgO
sample Mg 252380
Mustard was dissolved in the solvents in order to dose approximately the same
amounts of the toxic agent onto a layer of the solid tested The initial concentrations
of the mustard in the used solvents are shown in the Table 3 A 30 mg sample of the
Mg 252380 was weighed into each lockable glass vial where subsequently 10 sup1L of HD
dissolved in the respective solvents was pipetted onto the magnesium sample The vials
were immediately sealed and put into a thermostat for two hours Stoichiometric ratios
of MgO to HD were ca (20 - 30) to 1 so that the MgO samples were in excess in all
experimental cases Residual content of the HD in the reaction medium was estimated
analytically after macrnishing the reaction The results are summarised in Table 3
From the obtained data it is obvious that the extent of the HD conversion is appre-
ciably dependent on the kind of the solvent used under the given reaction conditions
Diethylether seems to be the most convenient solvent which might mainly be attributed
to its pronounced capillarity (based on its low surface tension and viscosity) Except for
NN-dimethyl-pyrrolidone the observed eregects of the other solvents on the HD distribu-
tion and reaction course do not direger too much and within an experimental error they
can be considered equally eregective
Since diethylether is not practical for use since it is narcotic (as well as its other
hazardous properties) it was decided that petrolether was a suitable solvent for all further
experimental work
Two common factors should also be considered which can adversely aregect the repro-
ducibility of the experiments for when HD is dissolved in certain solvents and is dosed
onto a layer of a powder reagent
The structure of the powder layer in a vial can hardly be standardised since the
magnesium samples are lumpy (granulated) and the individual lumps do not have a
reproducible macrt thus the penetration of the reagent with a solvent can somewhat
direger in the individual experiments
The extent of wetting the surface of the powder can hardly be controlled or checked
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 21
so far so that the actual extent of loading the surface with toxic agent with mustard
is unknown
Also taking into consideration the fact that the observed reactivity of nanosized reagents
is proportionally related to the area of their accessible surface (although diregering in
their respective specimacrc reactivity) then such a parameter as the extent of wetting
should play an important role The surface of the nanosized reagents are moistened as
evenly and reproducibly as possible however this may not be attainable in all replicated
experiments Only when the solvent is dosed in excess can it wet the whole surface
reliably However in such a case the (local) concentration of the dissolved toxic agent by
the surface of the powdered reagent should be appreciably diminished and consequently
the appeared reactivity would be lowered These circumstances may account for the
observed diregerences within a series of the replicated experiments
The importance of the extent of loading the nanosized reagent with the toxic agent
was investigated Using the same volume of the solvent as well as the charge of powder
reagents two extents of loading the nanosized reagent were decided for evaluation namely
the mass ratios of the respective magnesium samples vs the HD and were chosen as
follows 1001 or 2001 (ie a stoichiometry where the MgO exceeded the HD by a factor
of ca 50 or 100) The reaction time was 1 hour The results obtained are summarised in
the tables below (Table 4 and Table 5) At least two conclusions can be made redegecting
these results
a) the yield of the observed reaction can be increased as the loading of the magnesium
reagent surface is decreased under given experimental conditions and
b) magnesium oxides commonly exhibit higher reactivity towards the HD compared
with the related magnesium hydroxides although their respective dispersities (thus
specimacrc surface area) of the hydroxides (precursors) are comparatively greater namely
by a factor of two or three Therefore the observed lower capability of magnesium
hydroxides to convert the HD into non-toxic products might be attributed either
to their lower inherent reactivity (more likely) or lower ability of the solvent to
penetrate into a macrne-grained structure of those reagents
The kinetic promacrles that characterise the course of surface heterogeneous reaction of the
neat mustard on nanosized magnesium oxides were reported by Wagner et al [4] to have
two stages The reaction is relatively fast during the initial stage while its subsequent
course is comparatively slow since being controlled by the redistribution of HD over the
surface It was of interest to investigate the overall course of the reaction if the toxic agent
is spread over the nanosized sample being dissolved in petrolether The Mg 252380
sample was prepared in larger quantity and the current sample was chosen for a kinetic
study of the reaction A sample of 500 mg was weighed and put into six sealable vials
Mustard was dissolved in petrolether to contain 42 mg in 1 mL of the solvent Aliquots
of 01 ml were pipetted onto a layer of the magnesium sample the vials were immediately
sealed and put into a thermostat for a certain time Then the reaction mixtures were
analysed for the HD residual content Each experiment was repeated four times Results
are summarised in Table 6 The results of the kinetics evaluations are illustrated in Figure
22 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
4 The conversion of the HD by the evaluated reagent is not very fast the conversion
can reach up to ca 40 during a three-hour reaction Logarithmic kinetic data gave a
smooth curve showing that the course of the observed heterogeneous reaction does not
exhibit two stages Conversely itrsquos apparent from the graph that the reaction proceeds
quickly at the beginning and as time of the reaction elapses the reaction rate continuously
slows down This behaviour might be attributed to the gradual depletion of the mustard
at the active centers of the magnesium reagent followed by a diregusion-controlled process
of the HD redistribution over the reagent surface Another explanation for the kinetic
curve can be based on the concept of a gradual consumption of the magnesium sample
since it is present as the stoichiometric reagent whose surface is considered uniformly
(evenly) reactive In any case the observed course of the reaction can be considered to
be faster compared to that of a reaction performed without solvent
4 Conclusion
The following conclusions can be made from the reactivity experiments The observed
reaction rate of the toxic agent with the powdered nanosized reagent can be accelerated
when the agent dissolved in a suitable solvent is spread over the powdered reagent
making sure that wetting is even over the whole reagent surface Among the solvents
tested petrolether was the most suitable both for eplusmnciency and safety reasons
Acknowledgements
This work was supported by the Ministry of Education of the Czech Republic in the
frame of the Project No LN00A028
References
[1] O Koper E Lucas and KJ Klabunde Development of reactive topical skinprotectants against sulfur mustard and nerve agents Journal of Applied ToxicologyVol 19 (1999) pp 59 70
[2] O Koper E Lucas and KJ Klabunde Oxide Nano particles as Countermeasuresagainst Chemical and Biological Threats In Proceedings of the Joint ServiceChemical and Biological Decontamination Conference Salt Lake City (USA) May2000
[3] GW Wagner and OW Bartram Reactions of the nerve agent simulant diisopropyldeguorophosphate with self-decontaminating adsorbents A P-31 MAS NMR studyJournal of Molecular Catalysis A Chemical Vol 144 (1999) pp 419 424
[4] GW Wagner OW Bartram O Koper and KJ Klabunde Reactions of VX GDand HD with nanosize Mgo Journal Phys Chem B Vol 103 (1999) pp 3225 3228
[5] GWWagner O Koper E Lucas S Decker and KJ Klabunde Reactions ofVX GD and HD with nanosize CaO Autocatalytic dehydrohalogenation of HD Journal of Physical Chemistry B Vol 104 (2000) pp 5118 5123
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 17
shown to proceed mainly on the surface of the nanoparticles leading to non-toxic products
even at ambient temperature
Reactivity of the nanosized MgO towards the toxic agents has been described more
profoundly by Wagner et al [4] The following basic knowledge has been revealed
All mentioned toxic agents can be detoximacred ie converted into their non-toxic
products within a reasonable time period so that the activity of the reagent is
versatile
The chemical activity of the MgO surface cannot be considered uniform but the
more active centres are preferentially located at activated sites or defects along the
surface of the nanoparticles eg edges corners etc
Heterogeneous reactions of the respective neat toxic agents exhibit two-stage kinetics
when proceeded on the MgO nanoparticle surface The initial fast stage can be
attributed to the reaction of a given agent at highly active reaction centres and
the second stage is explained as a process of slower transport of the agent along
surface from less active site(s) to more reactive one(s) The process of a secondary
redistribution of the neat agent over a surface was convincingly correlated with the
respective evaporation rate (agent vapour pressure) as to be a rate-limiting factor
The main aims of the work were
To investigate the respective method and procedure of preparation of the nanosized
magnesium oxide
Characterise the respective synthesised magnesium oxide samples
Evaluate the prepared oxides for their respective detoximacrcation activities
Assess whether the overall activity of the prepared oxides could be increased utilising
an eregective solvent which is potentially more capable of distributing the toxic agent
over the whole surface of the oxide
Magnesium oxide is commonly obtained by thermal decomposition of magnesium hy-
droxide or carbonate [6] [7] and more recently by a sol-gel process [8] [9] The oxide
morphology particle size and specimacrc surface area depend on the preparation conditions
(pH gelling agent calcinations rate and temperature) It has been documented that
methoxide or alkoxide-based solgel synthesis of metal hydroxides followed by supercrit-
ical drying and vacuum dehydration can lead to the formation of nanoparticles of metal
oxides [10-15]
In considering the ways in how to additionally facilitate the respective detoximacrcation
reaction the two following approaches may be proposed to stimulate the overall course
of the reaction namely
The initial uniform spreading of the agent over the whole surface
A degow of the agent along the surface
Since the capillarity of the toxic agents is limited the agent distribution over the surface
of the solid (powdery) reagent could be enhanced utilising a solvent that is capable of
both dissolving the toxic agent and wetting the powdery reagent surface thus penetrating
its whole deposit and spreading there evenly Moreover if the chosen solvent is volatile
enough it evaporates at the upper layers causing a slow but benemacrcial degux of the solvent
18 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
containing the dissolved toxic agent which passes from bulk up to surface of the reagent
deposit (batch)
The detoximacrcation activities of the prepared samples of magnesium oxides and mag-
nesium hydroxides (ie precursors of macrnal nanosized MgO syntheses were evaluated using
sulphur mustard bis(2-chloroethyl) sulphide The agent was chosen deliberately for the
experiments because it has been reported to be relatively resistant to detoximacrcation [4]
When it is brought together with the nanosized MgO it can yield 2-chlorethyl vinyl sul-
phide and divinyl sulphide both of which are products of an elimination reaction and
the thiodiglycol a product of a nucleophilic substitution reaction
2 Experimental section
21 Preparation of nanoscale magnesium oxide
A modimacred autoclave hypercritical procedure has been developed to prepare nanoscale
MgO particles This method has four steps preparation of Mg(OCH3)2 by the reaction
of magnesium metal with methanol hydrolysis of Mg(OCH3)2 in the presence of toluene
hypercritical drying in an autoclave and thermal activation Commercially available
Mg(OCH3)2 solution (Aldrich 6 wt in methanol) were used in lieu of macrrst step The
experimental conditions are summarised in Table 1 Ultrasound waves [16] were used
for hydrolysis of Mg(OCH3)2 The hydroxide gel solution was transferred into a 100 ml
stainless-steel autoclave After nitrogen gas degushing the autoclave was slowly heated from
room temperature to 265plusmnC at a rate of 3plusmnCmin by the PID controller The temperature
was allowed to equilibrate at 265plusmnC for 15 min The autoclave was vented to release the
pressure which took about 05 1 min The autoclave was immediately removed from
the oven and cooled to room temperature The product was removed from the autoclave
and dried at 120plusmnC The macrnal product was stored in a bottle under normal conditions
On the basis of DTA results (Figure 1) the hydrated MgO precursors obtained from the
autoclave were heated under dynamic vacuum by using a furnace controlled by the PID
controller in a stainless steel tube The temperature ramp was 1plusmnCmin After the heat
treatment the sample was allowed to cool to room temperature
22 Characterization methods
The specimacrc surface area of the samples was determined via nitrogen adsorption-desorptions
isotherms at liquid nitrogen temperature by using a Coulter SA 3100 instrument TEM
micrographs were obtained using Philips 201 transmission electron microscope SEM pho-
tographs were obtained using Philips XL30 CP scanning electron microscope and X-ray
powder diregraction was performed with Siemens D5005 diregractometer Qualitative analy-
sis was performed with Bede ZDS for Windows version 199 and JCPDS PDF-2database
[17] DTA-TG measurements were carried out using NETZSCH STA 409 apparatus
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 19
23 Methodic of disintegrations mustard
Nanosized magnesium samples (precursors Mg(OH)2 as well as magnesium oxides) were
evaluated for their ability to convert sulphur mustard (hereafter also signed as HD) into
non-toxic products Synthesised powdery samples were dried over 24 hours in a vacuum
kiln (at 100 plusmnC 400 Pa) before tests A weighed portion of a given evaluated nanosized
sample was put into a glass vial provided with a solid screw cap (Supelco type CRS-33)
The toxic agent in a solution of a chosen solvent was dosed onto the powder reagent
layer The vial was sealed with a cap and placed into the thermostat All experiments
were performed at 25plusmnC and each run was repeated four to six times An addition of
isopropylalcohol (ca 2 mL) terminated the reaction The suspension was vigorously
agitated and the liquid fraction was separated from the solid using a centrifuge (9 000
cc miniexcl1 for 3 minutes) and subsequently analysed for a residual content of the mus-
tard The respective detoximacrcation capabilities of the evaluated nanosized samples were
expressed as percentages of mustard elimination from the reaction mixture under given
experimental conditions
3 Results and discussion
31 Characterization of samples magnesium aerogels
Figure 1 shows a typical thermal analysis of the precursors used in the synthesis Water
evolution started at a low temperature (sup1 100plusmnC) with a maximum at 139plusmnC Carbon
dioxide and water from the decomposition of residual OCH3 groups was detected in
the gas phase at sup1 300plusmnC and peaked at 396plusmnC The calcination temperature used in the
synthesis was 500plusmnC At this temperature the macrnal solids obtained were found to consist
primarily of particles of MgO without any traces of precursors The specimacrc surface area
and total pore volume are shown in Table 1 and Table 2 The specimacrc surface area de-
creases with increasing temperature of the annealing of precursors Figure 2 shows the
X-ray diregraction patterns of the precursor Mg151 and the samples prepared by their
thermal treatment They are all similar and exhibit three characteristic peaks for MgO
(periclas PDF 45-0496) With increasing annealing temperature the intensity of the
peaks has been evolved No diregraction lines of Mg(OH)2 were detected Electron mi-
crographs of the selected samples are shown in Figure 3 (TEM micrographs) Precursor
particles (sample Mg151) have uniform morphology and particle size as periclase par-
ticles (samples Mg152-156) The particle size from electron micrographs is similar to
that of the calculated size from X-ray diregraction (see Table 2) The Scherrer equation
was applied to estimate a crystallite size and a programme WinFit v12 was used for
calculation of particle size
20 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
32 The reactivity towards sulphur mustard
Two precursors Mg(OH)2 with high specimacrc surface areas (Mg 151 and Mg 252) and
three diregerent samples of magnesium oxide (Mg 151380 Mg 16380 Mg 252380)
were taken for experimental evaluation of their respective reactivities
The eregect of the solvent type used on the course of the detoximacrcation reaction was also
tested Five solvents diregering in their basic chemical properties (eg polarity proticity
viscosity capillarity and volatility) were taken for the experiment as follows
deg petrolether - non-polar distinct capillarity highly volatile
deg diethylether - non-polar aprotic oxygen-containing distinct capillarity highly volatile
deg acetone - weakly polar aprotic distinct capillarity volatile
deg N N-dimethylpyrrolidone - polar aprotic
deg methylalcohol - protic
The eregect of the solvent type on detoximacrcation reaction was only tested with the MgO
sample Mg 252380
Mustard was dissolved in the solvents in order to dose approximately the same
amounts of the toxic agent onto a layer of the solid tested The initial concentrations
of the mustard in the used solvents are shown in the Table 3 A 30 mg sample of the
Mg 252380 was weighed into each lockable glass vial where subsequently 10 sup1L of HD
dissolved in the respective solvents was pipetted onto the magnesium sample The vials
were immediately sealed and put into a thermostat for two hours Stoichiometric ratios
of MgO to HD were ca (20 - 30) to 1 so that the MgO samples were in excess in all
experimental cases Residual content of the HD in the reaction medium was estimated
analytically after macrnishing the reaction The results are summarised in Table 3
From the obtained data it is obvious that the extent of the HD conversion is appre-
ciably dependent on the kind of the solvent used under the given reaction conditions
Diethylether seems to be the most convenient solvent which might mainly be attributed
to its pronounced capillarity (based on its low surface tension and viscosity) Except for
NN-dimethyl-pyrrolidone the observed eregects of the other solvents on the HD distribu-
tion and reaction course do not direger too much and within an experimental error they
can be considered equally eregective
Since diethylether is not practical for use since it is narcotic (as well as its other
hazardous properties) it was decided that petrolether was a suitable solvent for all further
experimental work
Two common factors should also be considered which can adversely aregect the repro-
ducibility of the experiments for when HD is dissolved in certain solvents and is dosed
onto a layer of a powder reagent
The structure of the powder layer in a vial can hardly be standardised since the
magnesium samples are lumpy (granulated) and the individual lumps do not have a
reproducible macrt thus the penetration of the reagent with a solvent can somewhat
direger in the individual experiments
The extent of wetting the surface of the powder can hardly be controlled or checked
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 21
so far so that the actual extent of loading the surface with toxic agent with mustard
is unknown
Also taking into consideration the fact that the observed reactivity of nanosized reagents
is proportionally related to the area of their accessible surface (although diregering in
their respective specimacrc reactivity) then such a parameter as the extent of wetting
should play an important role The surface of the nanosized reagents are moistened as
evenly and reproducibly as possible however this may not be attainable in all replicated
experiments Only when the solvent is dosed in excess can it wet the whole surface
reliably However in such a case the (local) concentration of the dissolved toxic agent by
the surface of the powdered reagent should be appreciably diminished and consequently
the appeared reactivity would be lowered These circumstances may account for the
observed diregerences within a series of the replicated experiments
The importance of the extent of loading the nanosized reagent with the toxic agent
was investigated Using the same volume of the solvent as well as the charge of powder
reagents two extents of loading the nanosized reagent were decided for evaluation namely
the mass ratios of the respective magnesium samples vs the HD and were chosen as
follows 1001 or 2001 (ie a stoichiometry where the MgO exceeded the HD by a factor
of ca 50 or 100) The reaction time was 1 hour The results obtained are summarised in
the tables below (Table 4 and Table 5) At least two conclusions can be made redegecting
these results
a) the yield of the observed reaction can be increased as the loading of the magnesium
reagent surface is decreased under given experimental conditions and
b) magnesium oxides commonly exhibit higher reactivity towards the HD compared
with the related magnesium hydroxides although their respective dispersities (thus
specimacrc surface area) of the hydroxides (precursors) are comparatively greater namely
by a factor of two or three Therefore the observed lower capability of magnesium
hydroxides to convert the HD into non-toxic products might be attributed either
to their lower inherent reactivity (more likely) or lower ability of the solvent to
penetrate into a macrne-grained structure of those reagents
The kinetic promacrles that characterise the course of surface heterogeneous reaction of the
neat mustard on nanosized magnesium oxides were reported by Wagner et al [4] to have
two stages The reaction is relatively fast during the initial stage while its subsequent
course is comparatively slow since being controlled by the redistribution of HD over the
surface It was of interest to investigate the overall course of the reaction if the toxic agent
is spread over the nanosized sample being dissolved in petrolether The Mg 252380
sample was prepared in larger quantity and the current sample was chosen for a kinetic
study of the reaction A sample of 500 mg was weighed and put into six sealable vials
Mustard was dissolved in petrolether to contain 42 mg in 1 mL of the solvent Aliquots
of 01 ml were pipetted onto a layer of the magnesium sample the vials were immediately
sealed and put into a thermostat for a certain time Then the reaction mixtures were
analysed for the HD residual content Each experiment was repeated four times Results
are summarised in Table 6 The results of the kinetics evaluations are illustrated in Figure
22 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
4 The conversion of the HD by the evaluated reagent is not very fast the conversion
can reach up to ca 40 during a three-hour reaction Logarithmic kinetic data gave a
smooth curve showing that the course of the observed heterogeneous reaction does not
exhibit two stages Conversely itrsquos apparent from the graph that the reaction proceeds
quickly at the beginning and as time of the reaction elapses the reaction rate continuously
slows down This behaviour might be attributed to the gradual depletion of the mustard
at the active centers of the magnesium reagent followed by a diregusion-controlled process
of the HD redistribution over the reagent surface Another explanation for the kinetic
curve can be based on the concept of a gradual consumption of the magnesium sample
since it is present as the stoichiometric reagent whose surface is considered uniformly
(evenly) reactive In any case the observed course of the reaction can be considered to
be faster compared to that of a reaction performed without solvent
4 Conclusion
The following conclusions can be made from the reactivity experiments The observed
reaction rate of the toxic agent with the powdered nanosized reagent can be accelerated
when the agent dissolved in a suitable solvent is spread over the powdered reagent
making sure that wetting is even over the whole reagent surface Among the solvents
tested petrolether was the most suitable both for eplusmnciency and safety reasons
Acknowledgements
This work was supported by the Ministry of Education of the Czech Republic in the
frame of the Project No LN00A028
References
[1] O Koper E Lucas and KJ Klabunde Development of reactive topical skinprotectants against sulfur mustard and nerve agents Journal of Applied ToxicologyVol 19 (1999) pp 59 70
[2] O Koper E Lucas and KJ Klabunde Oxide Nano particles as Countermeasuresagainst Chemical and Biological Threats In Proceedings of the Joint ServiceChemical and Biological Decontamination Conference Salt Lake City (USA) May2000
[3] GW Wagner and OW Bartram Reactions of the nerve agent simulant diisopropyldeguorophosphate with self-decontaminating adsorbents A P-31 MAS NMR studyJournal of Molecular Catalysis A Chemical Vol 144 (1999) pp 419 424
[4] GW Wagner OW Bartram O Koper and KJ Klabunde Reactions of VX GDand HD with nanosize Mgo Journal Phys Chem B Vol 103 (1999) pp 3225 3228
[5] GWWagner O Koper E Lucas S Decker and KJ Klabunde Reactions ofVX GD and HD with nanosize CaO Autocatalytic dehydrohalogenation of HD Journal of Physical Chemistry B Vol 104 (2000) pp 5118 5123
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
18 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
containing the dissolved toxic agent which passes from bulk up to surface of the reagent
deposit (batch)
The detoximacrcation activities of the prepared samples of magnesium oxides and mag-
nesium hydroxides (ie precursors of macrnal nanosized MgO syntheses were evaluated using
sulphur mustard bis(2-chloroethyl) sulphide The agent was chosen deliberately for the
experiments because it has been reported to be relatively resistant to detoximacrcation [4]
When it is brought together with the nanosized MgO it can yield 2-chlorethyl vinyl sul-
phide and divinyl sulphide both of which are products of an elimination reaction and
the thiodiglycol a product of a nucleophilic substitution reaction
2 Experimental section
21 Preparation of nanoscale magnesium oxide
A modimacred autoclave hypercritical procedure has been developed to prepare nanoscale
MgO particles This method has four steps preparation of Mg(OCH3)2 by the reaction
of magnesium metal with methanol hydrolysis of Mg(OCH3)2 in the presence of toluene
hypercritical drying in an autoclave and thermal activation Commercially available
Mg(OCH3)2 solution (Aldrich 6 wt in methanol) were used in lieu of macrrst step The
experimental conditions are summarised in Table 1 Ultrasound waves [16] were used
for hydrolysis of Mg(OCH3)2 The hydroxide gel solution was transferred into a 100 ml
stainless-steel autoclave After nitrogen gas degushing the autoclave was slowly heated from
room temperature to 265plusmnC at a rate of 3plusmnCmin by the PID controller The temperature
was allowed to equilibrate at 265plusmnC for 15 min The autoclave was vented to release the
pressure which took about 05 1 min The autoclave was immediately removed from
the oven and cooled to room temperature The product was removed from the autoclave
and dried at 120plusmnC The macrnal product was stored in a bottle under normal conditions
On the basis of DTA results (Figure 1) the hydrated MgO precursors obtained from the
autoclave were heated under dynamic vacuum by using a furnace controlled by the PID
controller in a stainless steel tube The temperature ramp was 1plusmnCmin After the heat
treatment the sample was allowed to cool to room temperature
22 Characterization methods
The specimacrc surface area of the samples was determined via nitrogen adsorption-desorptions
isotherms at liquid nitrogen temperature by using a Coulter SA 3100 instrument TEM
micrographs were obtained using Philips 201 transmission electron microscope SEM pho-
tographs were obtained using Philips XL30 CP scanning electron microscope and X-ray
powder diregraction was performed with Siemens D5005 diregractometer Qualitative analy-
sis was performed with Bede ZDS for Windows version 199 and JCPDS PDF-2database
[17] DTA-TG measurements were carried out using NETZSCH STA 409 apparatus
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 19
23 Methodic of disintegrations mustard
Nanosized magnesium samples (precursors Mg(OH)2 as well as magnesium oxides) were
evaluated for their ability to convert sulphur mustard (hereafter also signed as HD) into
non-toxic products Synthesised powdery samples were dried over 24 hours in a vacuum
kiln (at 100 plusmnC 400 Pa) before tests A weighed portion of a given evaluated nanosized
sample was put into a glass vial provided with a solid screw cap (Supelco type CRS-33)
The toxic agent in a solution of a chosen solvent was dosed onto the powder reagent
layer The vial was sealed with a cap and placed into the thermostat All experiments
were performed at 25plusmnC and each run was repeated four to six times An addition of
isopropylalcohol (ca 2 mL) terminated the reaction The suspension was vigorously
agitated and the liquid fraction was separated from the solid using a centrifuge (9 000
cc miniexcl1 for 3 minutes) and subsequently analysed for a residual content of the mus-
tard The respective detoximacrcation capabilities of the evaluated nanosized samples were
expressed as percentages of mustard elimination from the reaction mixture under given
experimental conditions
3 Results and discussion
31 Characterization of samples magnesium aerogels
Figure 1 shows a typical thermal analysis of the precursors used in the synthesis Water
evolution started at a low temperature (sup1 100plusmnC) with a maximum at 139plusmnC Carbon
dioxide and water from the decomposition of residual OCH3 groups was detected in
the gas phase at sup1 300plusmnC and peaked at 396plusmnC The calcination temperature used in the
synthesis was 500plusmnC At this temperature the macrnal solids obtained were found to consist
primarily of particles of MgO without any traces of precursors The specimacrc surface area
and total pore volume are shown in Table 1 and Table 2 The specimacrc surface area de-
creases with increasing temperature of the annealing of precursors Figure 2 shows the
X-ray diregraction patterns of the precursor Mg151 and the samples prepared by their
thermal treatment They are all similar and exhibit three characteristic peaks for MgO
(periclas PDF 45-0496) With increasing annealing temperature the intensity of the
peaks has been evolved No diregraction lines of Mg(OH)2 were detected Electron mi-
crographs of the selected samples are shown in Figure 3 (TEM micrographs) Precursor
particles (sample Mg151) have uniform morphology and particle size as periclase par-
ticles (samples Mg152-156) The particle size from electron micrographs is similar to
that of the calculated size from X-ray diregraction (see Table 2) The Scherrer equation
was applied to estimate a crystallite size and a programme WinFit v12 was used for
calculation of particle size
20 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
32 The reactivity towards sulphur mustard
Two precursors Mg(OH)2 with high specimacrc surface areas (Mg 151 and Mg 252) and
three diregerent samples of magnesium oxide (Mg 151380 Mg 16380 Mg 252380)
were taken for experimental evaluation of their respective reactivities
The eregect of the solvent type used on the course of the detoximacrcation reaction was also
tested Five solvents diregering in their basic chemical properties (eg polarity proticity
viscosity capillarity and volatility) were taken for the experiment as follows
deg petrolether - non-polar distinct capillarity highly volatile
deg diethylether - non-polar aprotic oxygen-containing distinct capillarity highly volatile
deg acetone - weakly polar aprotic distinct capillarity volatile
deg N N-dimethylpyrrolidone - polar aprotic
deg methylalcohol - protic
The eregect of the solvent type on detoximacrcation reaction was only tested with the MgO
sample Mg 252380
Mustard was dissolved in the solvents in order to dose approximately the same
amounts of the toxic agent onto a layer of the solid tested The initial concentrations
of the mustard in the used solvents are shown in the Table 3 A 30 mg sample of the
Mg 252380 was weighed into each lockable glass vial where subsequently 10 sup1L of HD
dissolved in the respective solvents was pipetted onto the magnesium sample The vials
were immediately sealed and put into a thermostat for two hours Stoichiometric ratios
of MgO to HD were ca (20 - 30) to 1 so that the MgO samples were in excess in all
experimental cases Residual content of the HD in the reaction medium was estimated
analytically after macrnishing the reaction The results are summarised in Table 3
From the obtained data it is obvious that the extent of the HD conversion is appre-
ciably dependent on the kind of the solvent used under the given reaction conditions
Diethylether seems to be the most convenient solvent which might mainly be attributed
to its pronounced capillarity (based on its low surface tension and viscosity) Except for
NN-dimethyl-pyrrolidone the observed eregects of the other solvents on the HD distribu-
tion and reaction course do not direger too much and within an experimental error they
can be considered equally eregective
Since diethylether is not practical for use since it is narcotic (as well as its other
hazardous properties) it was decided that petrolether was a suitable solvent for all further
experimental work
Two common factors should also be considered which can adversely aregect the repro-
ducibility of the experiments for when HD is dissolved in certain solvents and is dosed
onto a layer of a powder reagent
The structure of the powder layer in a vial can hardly be standardised since the
magnesium samples are lumpy (granulated) and the individual lumps do not have a
reproducible macrt thus the penetration of the reagent with a solvent can somewhat
direger in the individual experiments
The extent of wetting the surface of the powder can hardly be controlled or checked
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 21
so far so that the actual extent of loading the surface with toxic agent with mustard
is unknown
Also taking into consideration the fact that the observed reactivity of nanosized reagents
is proportionally related to the area of their accessible surface (although diregering in
their respective specimacrc reactivity) then such a parameter as the extent of wetting
should play an important role The surface of the nanosized reagents are moistened as
evenly and reproducibly as possible however this may not be attainable in all replicated
experiments Only when the solvent is dosed in excess can it wet the whole surface
reliably However in such a case the (local) concentration of the dissolved toxic agent by
the surface of the powdered reagent should be appreciably diminished and consequently
the appeared reactivity would be lowered These circumstances may account for the
observed diregerences within a series of the replicated experiments
The importance of the extent of loading the nanosized reagent with the toxic agent
was investigated Using the same volume of the solvent as well as the charge of powder
reagents two extents of loading the nanosized reagent were decided for evaluation namely
the mass ratios of the respective magnesium samples vs the HD and were chosen as
follows 1001 or 2001 (ie a stoichiometry where the MgO exceeded the HD by a factor
of ca 50 or 100) The reaction time was 1 hour The results obtained are summarised in
the tables below (Table 4 and Table 5) At least two conclusions can be made redegecting
these results
a) the yield of the observed reaction can be increased as the loading of the magnesium
reagent surface is decreased under given experimental conditions and
b) magnesium oxides commonly exhibit higher reactivity towards the HD compared
with the related magnesium hydroxides although their respective dispersities (thus
specimacrc surface area) of the hydroxides (precursors) are comparatively greater namely
by a factor of two or three Therefore the observed lower capability of magnesium
hydroxides to convert the HD into non-toxic products might be attributed either
to their lower inherent reactivity (more likely) or lower ability of the solvent to
penetrate into a macrne-grained structure of those reagents
The kinetic promacrles that characterise the course of surface heterogeneous reaction of the
neat mustard on nanosized magnesium oxides were reported by Wagner et al [4] to have
two stages The reaction is relatively fast during the initial stage while its subsequent
course is comparatively slow since being controlled by the redistribution of HD over the
surface It was of interest to investigate the overall course of the reaction if the toxic agent
is spread over the nanosized sample being dissolved in petrolether The Mg 252380
sample was prepared in larger quantity and the current sample was chosen for a kinetic
study of the reaction A sample of 500 mg was weighed and put into six sealable vials
Mustard was dissolved in petrolether to contain 42 mg in 1 mL of the solvent Aliquots
of 01 ml were pipetted onto a layer of the magnesium sample the vials were immediately
sealed and put into a thermostat for a certain time Then the reaction mixtures were
analysed for the HD residual content Each experiment was repeated four times Results
are summarised in Table 6 The results of the kinetics evaluations are illustrated in Figure
22 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
4 The conversion of the HD by the evaluated reagent is not very fast the conversion
can reach up to ca 40 during a three-hour reaction Logarithmic kinetic data gave a
smooth curve showing that the course of the observed heterogeneous reaction does not
exhibit two stages Conversely itrsquos apparent from the graph that the reaction proceeds
quickly at the beginning and as time of the reaction elapses the reaction rate continuously
slows down This behaviour might be attributed to the gradual depletion of the mustard
at the active centers of the magnesium reagent followed by a diregusion-controlled process
of the HD redistribution over the reagent surface Another explanation for the kinetic
curve can be based on the concept of a gradual consumption of the magnesium sample
since it is present as the stoichiometric reagent whose surface is considered uniformly
(evenly) reactive In any case the observed course of the reaction can be considered to
be faster compared to that of a reaction performed without solvent
4 Conclusion
The following conclusions can be made from the reactivity experiments The observed
reaction rate of the toxic agent with the powdered nanosized reagent can be accelerated
when the agent dissolved in a suitable solvent is spread over the powdered reagent
making sure that wetting is even over the whole reagent surface Among the solvents
tested petrolether was the most suitable both for eplusmnciency and safety reasons
Acknowledgements
This work was supported by the Ministry of Education of the Czech Republic in the
frame of the Project No LN00A028
References
[1] O Koper E Lucas and KJ Klabunde Development of reactive topical skinprotectants against sulfur mustard and nerve agents Journal of Applied ToxicologyVol 19 (1999) pp 59 70
[2] O Koper E Lucas and KJ Klabunde Oxide Nano particles as Countermeasuresagainst Chemical and Biological Threats In Proceedings of the Joint ServiceChemical and Biological Decontamination Conference Salt Lake City (USA) May2000
[3] GW Wagner and OW Bartram Reactions of the nerve agent simulant diisopropyldeguorophosphate with self-decontaminating adsorbents A P-31 MAS NMR studyJournal of Molecular Catalysis A Chemical Vol 144 (1999) pp 419 424
[4] GW Wagner OW Bartram O Koper and KJ Klabunde Reactions of VX GDand HD with nanosize Mgo Journal Phys Chem B Vol 103 (1999) pp 3225 3228
[5] GWWagner O Koper E Lucas S Decker and KJ Klabunde Reactions ofVX GD and HD with nanosize CaO Autocatalytic dehydrohalogenation of HD Journal of Physical Chemistry B Vol 104 (2000) pp 5118 5123
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 19
23 Methodic of disintegrations mustard
Nanosized magnesium samples (precursors Mg(OH)2 as well as magnesium oxides) were
evaluated for their ability to convert sulphur mustard (hereafter also signed as HD) into
non-toxic products Synthesised powdery samples were dried over 24 hours in a vacuum
kiln (at 100 plusmnC 400 Pa) before tests A weighed portion of a given evaluated nanosized
sample was put into a glass vial provided with a solid screw cap (Supelco type CRS-33)
The toxic agent in a solution of a chosen solvent was dosed onto the powder reagent
layer The vial was sealed with a cap and placed into the thermostat All experiments
were performed at 25plusmnC and each run was repeated four to six times An addition of
isopropylalcohol (ca 2 mL) terminated the reaction The suspension was vigorously
agitated and the liquid fraction was separated from the solid using a centrifuge (9 000
cc miniexcl1 for 3 minutes) and subsequently analysed for a residual content of the mus-
tard The respective detoximacrcation capabilities of the evaluated nanosized samples were
expressed as percentages of mustard elimination from the reaction mixture under given
experimental conditions
3 Results and discussion
31 Characterization of samples magnesium aerogels
Figure 1 shows a typical thermal analysis of the precursors used in the synthesis Water
evolution started at a low temperature (sup1 100plusmnC) with a maximum at 139plusmnC Carbon
dioxide and water from the decomposition of residual OCH3 groups was detected in
the gas phase at sup1 300plusmnC and peaked at 396plusmnC The calcination temperature used in the
synthesis was 500plusmnC At this temperature the macrnal solids obtained were found to consist
primarily of particles of MgO without any traces of precursors The specimacrc surface area
and total pore volume are shown in Table 1 and Table 2 The specimacrc surface area de-
creases with increasing temperature of the annealing of precursors Figure 2 shows the
X-ray diregraction patterns of the precursor Mg151 and the samples prepared by their
thermal treatment They are all similar and exhibit three characteristic peaks for MgO
(periclas PDF 45-0496) With increasing annealing temperature the intensity of the
peaks has been evolved No diregraction lines of Mg(OH)2 were detected Electron mi-
crographs of the selected samples are shown in Figure 3 (TEM micrographs) Precursor
particles (sample Mg151) have uniform morphology and particle size as periclase par-
ticles (samples Mg152-156) The particle size from electron micrographs is similar to
that of the calculated size from X-ray diregraction (see Table 2) The Scherrer equation
was applied to estimate a crystallite size and a programme WinFit v12 was used for
calculation of particle size
20 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
32 The reactivity towards sulphur mustard
Two precursors Mg(OH)2 with high specimacrc surface areas (Mg 151 and Mg 252) and
three diregerent samples of magnesium oxide (Mg 151380 Mg 16380 Mg 252380)
were taken for experimental evaluation of their respective reactivities
The eregect of the solvent type used on the course of the detoximacrcation reaction was also
tested Five solvents diregering in their basic chemical properties (eg polarity proticity
viscosity capillarity and volatility) were taken for the experiment as follows
deg petrolether - non-polar distinct capillarity highly volatile
deg diethylether - non-polar aprotic oxygen-containing distinct capillarity highly volatile
deg acetone - weakly polar aprotic distinct capillarity volatile
deg N N-dimethylpyrrolidone - polar aprotic
deg methylalcohol - protic
The eregect of the solvent type on detoximacrcation reaction was only tested with the MgO
sample Mg 252380
Mustard was dissolved in the solvents in order to dose approximately the same
amounts of the toxic agent onto a layer of the solid tested The initial concentrations
of the mustard in the used solvents are shown in the Table 3 A 30 mg sample of the
Mg 252380 was weighed into each lockable glass vial where subsequently 10 sup1L of HD
dissolved in the respective solvents was pipetted onto the magnesium sample The vials
were immediately sealed and put into a thermostat for two hours Stoichiometric ratios
of MgO to HD were ca (20 - 30) to 1 so that the MgO samples were in excess in all
experimental cases Residual content of the HD in the reaction medium was estimated
analytically after macrnishing the reaction The results are summarised in Table 3
From the obtained data it is obvious that the extent of the HD conversion is appre-
ciably dependent on the kind of the solvent used under the given reaction conditions
Diethylether seems to be the most convenient solvent which might mainly be attributed
to its pronounced capillarity (based on its low surface tension and viscosity) Except for
NN-dimethyl-pyrrolidone the observed eregects of the other solvents on the HD distribu-
tion and reaction course do not direger too much and within an experimental error they
can be considered equally eregective
Since diethylether is not practical for use since it is narcotic (as well as its other
hazardous properties) it was decided that petrolether was a suitable solvent for all further
experimental work
Two common factors should also be considered which can adversely aregect the repro-
ducibility of the experiments for when HD is dissolved in certain solvents and is dosed
onto a layer of a powder reagent
The structure of the powder layer in a vial can hardly be standardised since the
magnesium samples are lumpy (granulated) and the individual lumps do not have a
reproducible macrt thus the penetration of the reagent with a solvent can somewhat
direger in the individual experiments
The extent of wetting the surface of the powder can hardly be controlled or checked
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 21
so far so that the actual extent of loading the surface with toxic agent with mustard
is unknown
Also taking into consideration the fact that the observed reactivity of nanosized reagents
is proportionally related to the area of their accessible surface (although diregering in
their respective specimacrc reactivity) then such a parameter as the extent of wetting
should play an important role The surface of the nanosized reagents are moistened as
evenly and reproducibly as possible however this may not be attainable in all replicated
experiments Only when the solvent is dosed in excess can it wet the whole surface
reliably However in such a case the (local) concentration of the dissolved toxic agent by
the surface of the powdered reagent should be appreciably diminished and consequently
the appeared reactivity would be lowered These circumstances may account for the
observed diregerences within a series of the replicated experiments
The importance of the extent of loading the nanosized reagent with the toxic agent
was investigated Using the same volume of the solvent as well as the charge of powder
reagents two extents of loading the nanosized reagent were decided for evaluation namely
the mass ratios of the respective magnesium samples vs the HD and were chosen as
follows 1001 or 2001 (ie a stoichiometry where the MgO exceeded the HD by a factor
of ca 50 or 100) The reaction time was 1 hour The results obtained are summarised in
the tables below (Table 4 and Table 5) At least two conclusions can be made redegecting
these results
a) the yield of the observed reaction can be increased as the loading of the magnesium
reagent surface is decreased under given experimental conditions and
b) magnesium oxides commonly exhibit higher reactivity towards the HD compared
with the related magnesium hydroxides although their respective dispersities (thus
specimacrc surface area) of the hydroxides (precursors) are comparatively greater namely
by a factor of two or three Therefore the observed lower capability of magnesium
hydroxides to convert the HD into non-toxic products might be attributed either
to their lower inherent reactivity (more likely) or lower ability of the solvent to
penetrate into a macrne-grained structure of those reagents
The kinetic promacrles that characterise the course of surface heterogeneous reaction of the
neat mustard on nanosized magnesium oxides were reported by Wagner et al [4] to have
two stages The reaction is relatively fast during the initial stage while its subsequent
course is comparatively slow since being controlled by the redistribution of HD over the
surface It was of interest to investigate the overall course of the reaction if the toxic agent
is spread over the nanosized sample being dissolved in petrolether The Mg 252380
sample was prepared in larger quantity and the current sample was chosen for a kinetic
study of the reaction A sample of 500 mg was weighed and put into six sealable vials
Mustard was dissolved in petrolether to contain 42 mg in 1 mL of the solvent Aliquots
of 01 ml were pipetted onto a layer of the magnesium sample the vials were immediately
sealed and put into a thermostat for a certain time Then the reaction mixtures were
analysed for the HD residual content Each experiment was repeated four times Results
are summarised in Table 6 The results of the kinetics evaluations are illustrated in Figure
22 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
4 The conversion of the HD by the evaluated reagent is not very fast the conversion
can reach up to ca 40 during a three-hour reaction Logarithmic kinetic data gave a
smooth curve showing that the course of the observed heterogeneous reaction does not
exhibit two stages Conversely itrsquos apparent from the graph that the reaction proceeds
quickly at the beginning and as time of the reaction elapses the reaction rate continuously
slows down This behaviour might be attributed to the gradual depletion of the mustard
at the active centers of the magnesium reagent followed by a diregusion-controlled process
of the HD redistribution over the reagent surface Another explanation for the kinetic
curve can be based on the concept of a gradual consumption of the magnesium sample
since it is present as the stoichiometric reagent whose surface is considered uniformly
(evenly) reactive In any case the observed course of the reaction can be considered to
be faster compared to that of a reaction performed without solvent
4 Conclusion
The following conclusions can be made from the reactivity experiments The observed
reaction rate of the toxic agent with the powdered nanosized reagent can be accelerated
when the agent dissolved in a suitable solvent is spread over the powdered reagent
making sure that wetting is even over the whole reagent surface Among the solvents
tested petrolether was the most suitable both for eplusmnciency and safety reasons
Acknowledgements
This work was supported by the Ministry of Education of the Czech Republic in the
frame of the Project No LN00A028
References
[1] O Koper E Lucas and KJ Klabunde Development of reactive topical skinprotectants against sulfur mustard and nerve agents Journal of Applied ToxicologyVol 19 (1999) pp 59 70
[2] O Koper E Lucas and KJ Klabunde Oxide Nano particles as Countermeasuresagainst Chemical and Biological Threats In Proceedings of the Joint ServiceChemical and Biological Decontamination Conference Salt Lake City (USA) May2000
[3] GW Wagner and OW Bartram Reactions of the nerve agent simulant diisopropyldeguorophosphate with self-decontaminating adsorbents A P-31 MAS NMR studyJournal of Molecular Catalysis A Chemical Vol 144 (1999) pp 419 424
[4] GW Wagner OW Bartram O Koper and KJ Klabunde Reactions of VX GDand HD with nanosize Mgo Journal Phys Chem B Vol 103 (1999) pp 3225 3228
[5] GWWagner O Koper E Lucas S Decker and KJ Klabunde Reactions ofVX GD and HD with nanosize CaO Autocatalytic dehydrohalogenation of HD Journal of Physical Chemistry B Vol 104 (2000) pp 5118 5123
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
20 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
32 The reactivity towards sulphur mustard
Two precursors Mg(OH)2 with high specimacrc surface areas (Mg 151 and Mg 252) and
three diregerent samples of magnesium oxide (Mg 151380 Mg 16380 Mg 252380)
were taken for experimental evaluation of their respective reactivities
The eregect of the solvent type used on the course of the detoximacrcation reaction was also
tested Five solvents diregering in their basic chemical properties (eg polarity proticity
viscosity capillarity and volatility) were taken for the experiment as follows
deg petrolether - non-polar distinct capillarity highly volatile
deg diethylether - non-polar aprotic oxygen-containing distinct capillarity highly volatile
deg acetone - weakly polar aprotic distinct capillarity volatile
deg N N-dimethylpyrrolidone - polar aprotic
deg methylalcohol - protic
The eregect of the solvent type on detoximacrcation reaction was only tested with the MgO
sample Mg 252380
Mustard was dissolved in the solvents in order to dose approximately the same
amounts of the toxic agent onto a layer of the solid tested The initial concentrations
of the mustard in the used solvents are shown in the Table 3 A 30 mg sample of the
Mg 252380 was weighed into each lockable glass vial where subsequently 10 sup1L of HD
dissolved in the respective solvents was pipetted onto the magnesium sample The vials
were immediately sealed and put into a thermostat for two hours Stoichiometric ratios
of MgO to HD were ca (20 - 30) to 1 so that the MgO samples were in excess in all
experimental cases Residual content of the HD in the reaction medium was estimated
analytically after macrnishing the reaction The results are summarised in Table 3
From the obtained data it is obvious that the extent of the HD conversion is appre-
ciably dependent on the kind of the solvent used under the given reaction conditions
Diethylether seems to be the most convenient solvent which might mainly be attributed
to its pronounced capillarity (based on its low surface tension and viscosity) Except for
NN-dimethyl-pyrrolidone the observed eregects of the other solvents on the HD distribu-
tion and reaction course do not direger too much and within an experimental error they
can be considered equally eregective
Since diethylether is not practical for use since it is narcotic (as well as its other
hazardous properties) it was decided that petrolether was a suitable solvent for all further
experimental work
Two common factors should also be considered which can adversely aregect the repro-
ducibility of the experiments for when HD is dissolved in certain solvents and is dosed
onto a layer of a powder reagent
The structure of the powder layer in a vial can hardly be standardised since the
magnesium samples are lumpy (granulated) and the individual lumps do not have a
reproducible macrt thus the penetration of the reagent with a solvent can somewhat
direger in the individual experiments
The extent of wetting the surface of the powder can hardly be controlled or checked
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 21
so far so that the actual extent of loading the surface with toxic agent with mustard
is unknown
Also taking into consideration the fact that the observed reactivity of nanosized reagents
is proportionally related to the area of their accessible surface (although diregering in
their respective specimacrc reactivity) then such a parameter as the extent of wetting
should play an important role The surface of the nanosized reagents are moistened as
evenly and reproducibly as possible however this may not be attainable in all replicated
experiments Only when the solvent is dosed in excess can it wet the whole surface
reliably However in such a case the (local) concentration of the dissolved toxic agent by
the surface of the powdered reagent should be appreciably diminished and consequently
the appeared reactivity would be lowered These circumstances may account for the
observed diregerences within a series of the replicated experiments
The importance of the extent of loading the nanosized reagent with the toxic agent
was investigated Using the same volume of the solvent as well as the charge of powder
reagents two extents of loading the nanosized reagent were decided for evaluation namely
the mass ratios of the respective magnesium samples vs the HD and were chosen as
follows 1001 or 2001 (ie a stoichiometry where the MgO exceeded the HD by a factor
of ca 50 or 100) The reaction time was 1 hour The results obtained are summarised in
the tables below (Table 4 and Table 5) At least two conclusions can be made redegecting
these results
a) the yield of the observed reaction can be increased as the loading of the magnesium
reagent surface is decreased under given experimental conditions and
b) magnesium oxides commonly exhibit higher reactivity towards the HD compared
with the related magnesium hydroxides although their respective dispersities (thus
specimacrc surface area) of the hydroxides (precursors) are comparatively greater namely
by a factor of two or three Therefore the observed lower capability of magnesium
hydroxides to convert the HD into non-toxic products might be attributed either
to their lower inherent reactivity (more likely) or lower ability of the solvent to
penetrate into a macrne-grained structure of those reagents
The kinetic promacrles that characterise the course of surface heterogeneous reaction of the
neat mustard on nanosized magnesium oxides were reported by Wagner et al [4] to have
two stages The reaction is relatively fast during the initial stage while its subsequent
course is comparatively slow since being controlled by the redistribution of HD over the
surface It was of interest to investigate the overall course of the reaction if the toxic agent
is spread over the nanosized sample being dissolved in petrolether The Mg 252380
sample was prepared in larger quantity and the current sample was chosen for a kinetic
study of the reaction A sample of 500 mg was weighed and put into six sealable vials
Mustard was dissolved in petrolether to contain 42 mg in 1 mL of the solvent Aliquots
of 01 ml were pipetted onto a layer of the magnesium sample the vials were immediately
sealed and put into a thermostat for a certain time Then the reaction mixtures were
analysed for the HD residual content Each experiment was repeated four times Results
are summarised in Table 6 The results of the kinetics evaluations are illustrated in Figure
22 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
4 The conversion of the HD by the evaluated reagent is not very fast the conversion
can reach up to ca 40 during a three-hour reaction Logarithmic kinetic data gave a
smooth curve showing that the course of the observed heterogeneous reaction does not
exhibit two stages Conversely itrsquos apparent from the graph that the reaction proceeds
quickly at the beginning and as time of the reaction elapses the reaction rate continuously
slows down This behaviour might be attributed to the gradual depletion of the mustard
at the active centers of the magnesium reagent followed by a diregusion-controlled process
of the HD redistribution over the reagent surface Another explanation for the kinetic
curve can be based on the concept of a gradual consumption of the magnesium sample
since it is present as the stoichiometric reagent whose surface is considered uniformly
(evenly) reactive In any case the observed course of the reaction can be considered to
be faster compared to that of a reaction performed without solvent
4 Conclusion
The following conclusions can be made from the reactivity experiments The observed
reaction rate of the toxic agent with the powdered nanosized reagent can be accelerated
when the agent dissolved in a suitable solvent is spread over the powdered reagent
making sure that wetting is even over the whole reagent surface Among the solvents
tested petrolether was the most suitable both for eplusmnciency and safety reasons
Acknowledgements
This work was supported by the Ministry of Education of the Czech Republic in the
frame of the Project No LN00A028
References
[1] O Koper E Lucas and KJ Klabunde Development of reactive topical skinprotectants against sulfur mustard and nerve agents Journal of Applied ToxicologyVol 19 (1999) pp 59 70
[2] O Koper E Lucas and KJ Klabunde Oxide Nano particles as Countermeasuresagainst Chemical and Biological Threats In Proceedings of the Joint ServiceChemical and Biological Decontamination Conference Salt Lake City (USA) May2000
[3] GW Wagner and OW Bartram Reactions of the nerve agent simulant diisopropyldeguorophosphate with self-decontaminating adsorbents A P-31 MAS NMR studyJournal of Molecular Catalysis A Chemical Vol 144 (1999) pp 419 424
[4] GW Wagner OW Bartram O Koper and KJ Klabunde Reactions of VX GDand HD with nanosize Mgo Journal Phys Chem B Vol 103 (1999) pp 3225 3228
[5] GWWagner O Koper E Lucas S Decker and KJ Klabunde Reactions ofVX GD and HD with nanosize CaO Autocatalytic dehydrohalogenation of HD Journal of Physical Chemistry B Vol 104 (2000) pp 5118 5123
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 21
so far so that the actual extent of loading the surface with toxic agent with mustard
is unknown
Also taking into consideration the fact that the observed reactivity of nanosized reagents
is proportionally related to the area of their accessible surface (although diregering in
their respective specimacrc reactivity) then such a parameter as the extent of wetting
should play an important role The surface of the nanosized reagents are moistened as
evenly and reproducibly as possible however this may not be attainable in all replicated
experiments Only when the solvent is dosed in excess can it wet the whole surface
reliably However in such a case the (local) concentration of the dissolved toxic agent by
the surface of the powdered reagent should be appreciably diminished and consequently
the appeared reactivity would be lowered These circumstances may account for the
observed diregerences within a series of the replicated experiments
The importance of the extent of loading the nanosized reagent with the toxic agent
was investigated Using the same volume of the solvent as well as the charge of powder
reagents two extents of loading the nanosized reagent were decided for evaluation namely
the mass ratios of the respective magnesium samples vs the HD and were chosen as
follows 1001 or 2001 (ie a stoichiometry where the MgO exceeded the HD by a factor
of ca 50 or 100) The reaction time was 1 hour The results obtained are summarised in
the tables below (Table 4 and Table 5) At least two conclusions can be made redegecting
these results
a) the yield of the observed reaction can be increased as the loading of the magnesium
reagent surface is decreased under given experimental conditions and
b) magnesium oxides commonly exhibit higher reactivity towards the HD compared
with the related magnesium hydroxides although their respective dispersities (thus
specimacrc surface area) of the hydroxides (precursors) are comparatively greater namely
by a factor of two or three Therefore the observed lower capability of magnesium
hydroxides to convert the HD into non-toxic products might be attributed either
to their lower inherent reactivity (more likely) or lower ability of the solvent to
penetrate into a macrne-grained structure of those reagents
The kinetic promacrles that characterise the course of surface heterogeneous reaction of the
neat mustard on nanosized magnesium oxides were reported by Wagner et al [4] to have
two stages The reaction is relatively fast during the initial stage while its subsequent
course is comparatively slow since being controlled by the redistribution of HD over the
surface It was of interest to investigate the overall course of the reaction if the toxic agent
is spread over the nanosized sample being dissolved in petrolether The Mg 252380
sample was prepared in larger quantity and the current sample was chosen for a kinetic
study of the reaction A sample of 500 mg was weighed and put into six sealable vials
Mustard was dissolved in petrolether to contain 42 mg in 1 mL of the solvent Aliquots
of 01 ml were pipetted onto a layer of the magnesium sample the vials were immediately
sealed and put into a thermostat for a certain time Then the reaction mixtures were
analysed for the HD residual content Each experiment was repeated four times Results
are summarised in Table 6 The results of the kinetics evaluations are illustrated in Figure
22 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
4 The conversion of the HD by the evaluated reagent is not very fast the conversion
can reach up to ca 40 during a three-hour reaction Logarithmic kinetic data gave a
smooth curve showing that the course of the observed heterogeneous reaction does not
exhibit two stages Conversely itrsquos apparent from the graph that the reaction proceeds
quickly at the beginning and as time of the reaction elapses the reaction rate continuously
slows down This behaviour might be attributed to the gradual depletion of the mustard
at the active centers of the magnesium reagent followed by a diregusion-controlled process
of the HD redistribution over the reagent surface Another explanation for the kinetic
curve can be based on the concept of a gradual consumption of the magnesium sample
since it is present as the stoichiometric reagent whose surface is considered uniformly
(evenly) reactive In any case the observed course of the reaction can be considered to
be faster compared to that of a reaction performed without solvent
4 Conclusion
The following conclusions can be made from the reactivity experiments The observed
reaction rate of the toxic agent with the powdered nanosized reagent can be accelerated
when the agent dissolved in a suitable solvent is spread over the powdered reagent
making sure that wetting is even over the whole reagent surface Among the solvents
tested petrolether was the most suitable both for eplusmnciency and safety reasons
Acknowledgements
This work was supported by the Ministry of Education of the Czech Republic in the
frame of the Project No LN00A028
References
[1] O Koper E Lucas and KJ Klabunde Development of reactive topical skinprotectants against sulfur mustard and nerve agents Journal of Applied ToxicologyVol 19 (1999) pp 59 70
[2] O Koper E Lucas and KJ Klabunde Oxide Nano particles as Countermeasuresagainst Chemical and Biological Threats In Proceedings of the Joint ServiceChemical and Biological Decontamination Conference Salt Lake City (USA) May2000
[3] GW Wagner and OW Bartram Reactions of the nerve agent simulant diisopropyldeguorophosphate with self-decontaminating adsorbents A P-31 MAS NMR studyJournal of Molecular Catalysis A Chemical Vol 144 (1999) pp 419 424
[4] GW Wagner OW Bartram O Koper and KJ Klabunde Reactions of VX GDand HD with nanosize Mgo Journal Phys Chem B Vol 103 (1999) pp 3225 3228
[5] GWWagner O Koper E Lucas S Decker and KJ Klabunde Reactions ofVX GD and HD with nanosize CaO Autocatalytic dehydrohalogenation of HD Journal of Physical Chemistry B Vol 104 (2000) pp 5118 5123
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
22 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
4 The conversion of the HD by the evaluated reagent is not very fast the conversion
can reach up to ca 40 during a three-hour reaction Logarithmic kinetic data gave a
smooth curve showing that the course of the observed heterogeneous reaction does not
exhibit two stages Conversely itrsquos apparent from the graph that the reaction proceeds
quickly at the beginning and as time of the reaction elapses the reaction rate continuously
slows down This behaviour might be attributed to the gradual depletion of the mustard
at the active centers of the magnesium reagent followed by a diregusion-controlled process
of the HD redistribution over the reagent surface Another explanation for the kinetic
curve can be based on the concept of a gradual consumption of the magnesium sample
since it is present as the stoichiometric reagent whose surface is considered uniformly
(evenly) reactive In any case the observed course of the reaction can be considered to
be faster compared to that of a reaction performed without solvent
4 Conclusion
The following conclusions can be made from the reactivity experiments The observed
reaction rate of the toxic agent with the powdered nanosized reagent can be accelerated
when the agent dissolved in a suitable solvent is spread over the powdered reagent
making sure that wetting is even over the whole reagent surface Among the solvents
tested petrolether was the most suitable both for eplusmnciency and safety reasons
Acknowledgements
This work was supported by the Ministry of Education of the Czech Republic in the
frame of the Project No LN00A028
References
[1] O Koper E Lucas and KJ Klabunde Development of reactive topical skinprotectants against sulfur mustard and nerve agents Journal of Applied ToxicologyVol 19 (1999) pp 59 70
[2] O Koper E Lucas and KJ Klabunde Oxide Nano particles as Countermeasuresagainst Chemical and Biological Threats In Proceedings of the Joint ServiceChemical and Biological Decontamination Conference Salt Lake City (USA) May2000
[3] GW Wagner and OW Bartram Reactions of the nerve agent simulant diisopropyldeguorophosphate with self-decontaminating adsorbents A P-31 MAS NMR studyJournal of Molecular Catalysis A Chemical Vol 144 (1999) pp 419 424
[4] GW Wagner OW Bartram O Koper and KJ Klabunde Reactions of VX GDand HD with nanosize Mgo Journal Phys Chem B Vol 103 (1999) pp 3225 3228
[5] GWWagner O Koper E Lucas S Decker and KJ Klabunde Reactions ofVX GD and HD with nanosize CaO Autocatalytic dehydrohalogenation of HD Journal of Physical Chemistry B Vol 104 (2000) pp 5118 5123
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 23
[6] DR Lide (Ed) CRC Handbook of Chemistry and Physics A Ready-Reference Bookof Chemical and Physical Data 77th Edition CRC Press Boca Raton New York London Tokyo
[7] MA Aramendia V Borau and CJimenez Synthesis and characterization of variousmgo and related systems J Mater Chem Vol 6(12) (1996) pp 1943 1949
[8] BQ Xu JM Wei and HY Wang Nano-MgO Novel preparation and applicationas support of Ni catalyst for CO2 reforming of methane Catalysis Today Vol 68(1-3) (2001) pp 217 225
[9] HS Choi and ST Hwang Sol-gel-derived magnesium oxide precursor for thin-macrlmfabrication J Mat Res Vol 15 (2000) pp 842 845
[10] T Lopez RGomez J Navarrete and E Lopez-Salinas Evidence for Lewis andBronsted acid sites on MgO obtained by sol-gel Journal of Sol-Gel Science andTechnology Vol 13 (1998) pp 1043 1047
[11] S Utamapanya KJ Klabunde and JR Schlup Nanoscale metal-oxide particlesclusters as chemical reagents - synthesis and properties of ultrahigh surface-areamagnesium-hydroxide and magnesium-oxide ChemMater Vol 3 (1991) pp 175 181
[12] JV Stark and KJ Klabunde Nanoscale metal oxide particlesclusters as chemicalreagents Adsorption of hydrogen halides nitric oxide and sulfur trioxide onmagnesium oxide nanocrystals and compared with microcrystals Chem Mater Vol8(8) (1996) pp1913 1918
[13] JV Stark DG Park and I Lagadic Nanoscale metal oxide particlesclustersas chemical reagents Unique surface chemistry on magnesium oxide as shown byenhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressuredependence Chem Mater Vol 8(8) (1996) pp 1904 1912
[14] L Znaidi KChhor and C Pommier Batch and semi-continuous synthesisof magnesium oxide powders from hydrolysis and supercritical treatment ofMg(OCH3)2 MatResBull Vol 31 (1996) pp 1527 1535
[15] OB Koper I Lagadic AVolodin and KJ Klabunde Alkaline-earth oxidenanoparticles obtained by aerogel methods Characterization and rational forunexpectedly high surface chemical reactivities Chem Mater Vol 9 (1997) pp2468 2480
[16] V middotStengl S Bakardjieva M Mamiddotrparasup3kovparaa PBezdimiddotcka and J middotSubrt Magnesium oxidenanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides MatLett Vol 57(24-25) (2003) pp 3998 4003
[17] JCPDS PDF 2 database Release 2001 International Centre for Diregraction DataNewton Square PA USA
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
24 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Sample Mg-methoxide Methanol+water Toluene SBET Vp
[mL] [mL] [mL] [m2giexcl1] [ccgiexcl1]
Mg151 834 0 + 21 4166 1047 141
Mg16 102 0 + 21 510 754 078
Mg251 94 42 + 028 68 1099 138
Mg252 94 42 + 028 68 1236 142
6 solution of magnesium methoxide other 868 solution
Table 1 Experimental conditions and resulting specishy c surface areas SBET and total porevolume Vp of Mgaerogels prepared from magnesium methoxide
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 25
Sample T SBET Vp Phase L442micro
[plusmnC] [m2giexcl1] [ccgiexcl1] identishy ed by [nm]
XRD
Mg151360 360 537 035 Periclase 17
Mg152380 380 497 038 Periclase 20
Mg153400 400 377 042 Periclase 29
Mg154450 450 328 047 Periclase 36
Mg155500 500 288 056 Periclase 42
Mg16380 380 327 039 Periclase 19
Mg251380 380 246 038 Periclase 21
Mg252380 380 358 039 Periclase 20
Table 2 Specishy c surface areas and crystallite sizes of nanoscale dehydrated MgO samples
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
26 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Solvent
Diethyl-
etherAcetone
Methyl
alcohol
NN-
Dimethyl-
pyrrolidone
Petrol-
ether
Surface tension at 25plusmnC (reg )
[mNmiexcl1]
167 235 220 - 177
Viscosity at 25plusmnC ( sup2 ) [mPas] 02 03 08 - 03
Initial content of the HD (mg HD
per 30 mg charge of Mg reagent)
0511 0392 0471 0487 0530
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0207 0260 0298 0420 0295
Standard deviation of the aver-
age
1523 659 1367 336 458
Percentage of the HD conversion
after the reaction []
595 336 366 138 442
Table 3 Residual content of the HD after reaction on the magnesium sample Mg 151380(reaction time 2 h temperature 25macrC charge of the reagent 30 mg the HD dissolved in 002mlof solvent)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 27
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0303 0290 0235 0156 0286
Standard deviation of the average 11 16 84 27 16
Percentage of the HD conversion
after the elapse of the reaction []
392 419 529 688 427
Table 4 Residual content of HD after reaction on the magnesium samples (reaction time 1 htemperature 25macrC charge of the respective samples in the reaction 30 mg 05 mg of HD dissolvedin 01 ml of petrolether)
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
28 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Characteristics Precursors MgO
Mg151 Mg252Mg151
380
Mg16
380
Mg252
380
Average residual content of the
HD (mg HD per 30 mg charge of
Mg reagent)
0132 0144 0100 0057 0132
Standard deviation of the average 36 26 02 17 43
Percentage of the HD conversion
after the elapse of the reaction []
469 424 599 770 471
Table 5 The residual content of HD after its reaction on the magnesium samples (reaction time1 hour temperature 25macrC charge of the respective samples in the reaction 30 mg 025mg HDdissolved in 01 ml petrolether)
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 29
Time of reaction (ie the HD
conversion) [min]
0 15 30 60 120 180
Average residual content of HD
(mg HD per 500 mg charge of Mg
reagent)
0422 0363 0327 0299 0272 0261
Standard deviation of the average 94 349 17 71 61 50
Percentage of the HD conversion
after the elapse of the reaction []
00 139 224 291 355 382
Table 6 Time dependence of the mustard conversion on Mg 252380 sample (the Mg reagentcharge of 500 mg 042 mg of HD in 01 ml of petrolether temperature of 25macrC)
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
30 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 1 DTA - TG of sample Mg151
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 31
Fig 2 XRD spectra sample Mg15 1 and samples Mg151360 - Mg151500
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent
32 V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633
Fig 3 TEM micrographs of precursor Mg15 and heated samples Mg151360-151500
V microStengl et al Central European Journal of Chemistry 2(1) 2004 1633 33
Fig 4 Time dependence of the HD conversion on the Mg 252380 reagent