Adsorptive removal of chlorophenols from water by bituminous shale

ADSORPTIVE REMOVAL OF CHLOROPHENOLS FROM

WATER BY BITUMINOUS SHALE

ESMA TUÈ TEM*, RES°AT APAK and C°AGÏ ATAY F. UÈ NAL

Department of Chemistry, Faculty of Engineering, IÇstanbul University, Avc|lar 34850, IÇstanbul,Turkey

(First received April 1996; accepted in revised form November 1997)

AbstractÐChlorophenols are among priority water pollutants which are taken up by aquatic fauna and¯ora and enriched in the food chains. Acid-activated bituminous shale has been used as an adsorbentfor the removal of 2-chlorophenol (MCP) and 2,4-dichlorophenol (DCP) from water and the relatedprocess parameters were investigated. Kinetic analysis showed that the adsorption reaction could be ap-proximated by a ®rst-order rate equation for which pore-di�usion was the essential rate-controllingstep. Adsorption was endothermic and basically of a physical character. Equilibrium modelling by line-arized adsorption isotherms revealed that a Langmuir equation could well represent the observed data.The entropy change of adsorption was more positive for DCP due to its higher polarity. The saturationcapacity of the sorbent for both chlorophenols were determined by dynamic column tests, this exper-imental capacity being lower than the theoretical monolayer capacity envisaged by the Langmuirequation. Adsorption was completely reversible as the retained DCP could be completely desorbedfrom the column with distilled water as eluant. The results were evaluated within the scope of utiliz-ation of cost-e�ective unconventional sorbents to remove chlorinated organics as possible substitutesfor activated carbon. # 1998 Elsevier Science Ltd. All rights reserved

Key wordsÐ2-chlorophenol, 2,4-dichlorophenol, adsorption, bituminous shale

INTRODUCTION

Chlorinated organic compounds, speci®cally chloro-

phenols, are among priority water pollutants whose

ecological risks and toxicity to aquatic ¯ora and

fauna are biomagni®ed through various food chains

(Riley and Skirrow, 1975). Their sources are waste-

waters coming from petroleum re®neries, plastics,

rubber, pharmaceuticals, disinfectants, wood-preser-

ving and steel industries (Haribabu et al., 1993). In

addition, 2,4-dichlorophenol is used in large

volumes in the manufacture of 2,4-dichlorophenox-

yacetic acid (2,4-D), i.e. a major pesticide (Freiter,

1979). Since chlorophenols are rather persistent in

the environment, they should be removed from

industrial plant wastewater before discharge to mu-

nicipal sewage systems.

Although a number of processes have been devel-

oped for chlorophenol removal (Freeman, 1989),

the leading ones from an economical standpoint are

probably adsorption by activated carbon (Giusti et

al., 1974; Su�et and McGuire, 1980) and by orga-

nophilic clays (Mortland et al., 1986; La Grega et

al., 1994). Due to the high cost of activated carbon,

a number of commonly available cheap materials

like ¯y ash, bottom ash, saw dust, etc., have been

investigated for their possible use as substitutes for

carbon (Haribabu et al., 1993). Extensive e�ortshave been undertaken in our department for the

cost-e�ective utilization of unconventional sorbentsfor the removal of various contaminants such asheavy metals, radionuclides and organics (Apak,1991; Apak et al., 1993, 1995, 1996, 1998) in place

of the more expensive standard adsorbents.This study is concerned with 2-chloro- and 2,4-

dichlorophenol removal from water using bitumi-

nous shale (resembling activated carbon) as anunconventional sorbent. Thermodynamic and kin-etic analysis have been performed on the adsorption

of these contaminants by means of thermostaticbatch experiments.

MATERIALS AND METHODS

Chemical substances, solutions and sorbents

2-Chlorophenol, 2,4-dichlorophenol, NaOH and HCl(analytical reagent grade) were supplied by Merck. Thebituminous shale was collected from GoÈ ynuÈ k, Bolu andkindly supplied by Professor E. Ekinci from the ChemicalEngineering Department of IÇstanbul Technical University.The raw shale contained 8.1% bitumen and its ash con-sisted of 52.5% (carbonate + sulfate), 23.1% silicate,1.1% pyrite, 1.1% bitumen and 21.4% kerogen (the latteris a bitumen-like solid composed of a mixture of aliphaticand aromatic compounds of humic and algal origin)which cannot be extracted by organic solvents (Uysal andTamimi, 1990). The chemical analysis of the shale wasreported as follows: moisture, 5.7%; ash, 24.4%; volatilematter, 56.3%; ®xed carbon, 13.6%; C, 49.92%; H,

Wat. Res. Vol. 32, No. 8, pp. 2315±2324, 1998# 1998 Elsevier Science Ltd. All rights reserved

Printed in Great Britain0043-1354/98 $19.00+0.00PII: S0043-1354(97)00476-4

*Author to whom all correspondence should be addressed.[Tel: +90-212-591-1998; Fax: +90-212-591-1997].

2315

6.42%; S, 3.32%; N, 1.07% and O, 9.4%. Mineralogicalanalysis revealed that the inorganic minerals accompany-ing kerogen were matrix-bound, had a particle sizeR20 mm and consisted of plagioclase (type of feldspar hav-ing the general formula (Na, Ca) Al (Si, Al) Si2O8), pyriteand gypsum to a lesser proportion. Since these matrix-bound inorganic minerals were essentially insoluble in di-lute acid, acid-washing of the sorbent did not cause a sig-ni®cant change in the matrix composition except for thefact that dissolution of new material from the shale duringadsorption tests carried out at acidic-to-neutral pH wasprevented with this measure.

All working solutions of chlorophenols were preparedfrom 100 ppm (mg/ml) aqueous stock solutions without pHadjustment.

Instruments

A Hitachi 220 A UV-visible spectrophotometerequipped with quartz cells of 10 mm light path was usedfor spectrophotometric determination of chlorophenols.Batch sorption tests were carried out on a NuÈ ve (Turkey)thermostatic water bath/shaker. After contact, the super-nates were separated by using a MSE Mistral 2000 centri-fuge. The pH of solutions was measured and adjusted (ifnecessary) with a Metrohm E-512 pH-meter using a glasselectrode. Column experiments were carried out in thermo-static glass columns (h= 25 cm, b= 1.5 cm). Bituminousshale was analyzed mineralogically by using an electronmicroscope (Jeol 733 Superprobe), DTA (Netzsch GmbHProgrammer 410 Model) and TG (Thermobalance STA409 Model) apparatus.

Procedures

The shales were ground and classi®ed with respect tosize through a ÿ20/50+ mesh sieve. For acid activation ofthe adsorbent, 100 g bituminous shale was treated with 1 lof 15% (w/w) HCl solution at 808C for 2 h in an agitatedbeaker. After decantation and removal of the aqueousacid solution, the solid was collected, washed with water

to a ®nal extract pH of 5.5±6.0 and dried at 1308C to beused as sorbent in further experiments.Batch adsorption experiments were conducted by con-

tacting 1.0 g of sorbent with 50 ml of chlorophenol sol-utions of di�erent concentrations at preselectedtemperatures in a thermostatic shaker/water bath agitatedat a rate of 100 rpm. After agitation, the mixtures werecentrifuged and the corresponding chlorophenol concen-tration in the supernate was determined spectrophotome-trically at 274 and 282 nm for 2-chlorophenol and 2,4-dichlorophenol, respectively, with molar absorptivities of2.15� 103 and 2.25�103 l molÿ1 cmÿ1. The pH of ®nal sol-utions were brought to their initial pH where necessaryusing 0.1 N HCl and 0.1 N NaOH solutions.The chlorophenol concentration in the sorbent phase (q

in mg/g) was calculated from:

q � �C0 ÿ Cf �V=m �1�where C0 and Cf are the initial and ®nal concentrations ofthe adsorbate in solution (in mg/l), V is volume of sol-ution (in l) and m is the mass of sorbent (in g).Adsorption capacities of the sorbents for chlorophenols

were determined at room temperature via dynamic columntests by passing the adsorbate solution through 6 g sorbent®lled in a column of diameter 1.5 cm and height 25 cm.Constant throughput rates were maintained by adjustingthe hydrostatic head over the columns. The e�uents wereanalyzed in portions for the corresponding phenols, andthe area over the breakthrough curves were mathemat-ically integrated to ®nd the dynamic adsorption capacities.

RESULTS AND DISCUSSION

E�ect of contact time and concentration

The e�ect of contact time on adsorption of chloro-phenols for varying initial concentrations at roomtemperature (2520.18C) are shown in Fig. 1 and 2

Fig. 1. The sorbent phase concentration of MCP (mg/g) as a function of time (h) for varying initialaqueous concentrations (25, .; 50, Q; 75, + and 100, R ppm MCP). pHi=6.3±5.9; temp. = 2520.18C;

madsorbent=1.0 g/50 ml.

Esma TuÈ tem et al.2316

for monochlorophenol (MCP) and dichlorophenol

(DCP), respectively. The sorbent phase concen-

tration for a 25 ppm solution increased from 0.51 to

0.81 mg/g for MCP and from 0.78 to 1.05 mg/g for

DCP from a time period of 1 to 24 h. The lower the

concentration, the higher was the adsorption percen-

tage. Since the plateau region of adsorption vs time

curves (see Figs 1 and 2) started at a contact period

Fig. 2. The sorbent phase concentration of DCP (mg/g) as a function of time (h) for varying initial aqu-eous concentrations (25, .; 50, Q; 75, + and 100, R ppm MCP). pHi=6.0±5.7; temp. = 2520.18C;


Fig. 3. Lagergren's ®rst order rate equation of MCP adsorption on bituminous shale for varying initialconcentrations (25, .; 50, Q; 75, + and 100, R ppm of MCP). pHi=6.3±5.9; temp. = 2520.18C;


Removal of chlorophenols by bituminous shale 2317

of 8 h and prolonged standing of phenol solutions

may cause turbidity to build up at the liquid±solid

interface (McKay et al., 1985), an equilibration

period of 8 h was adapted for all practical purposes

and used in further experiments.

Evaluation of kinetic data and the rate equation

The sorbent phase concentrations of the chloro-

phenols (q) vs time (t) data at room temperature

(Figs 1 and 2) were further processed for deriving

the rate equation and for testing the role of di�u-

Fig. 4. Lagergen's ®rst order rate equation of DCP adsorption on bituminous shale for varying initialconcentrations (25, .; 50, Q; 75, + and 100, R ppm of DCP). pHi=6.0±5.7; temp. = 2520.18C;


Fig. 5. Bangham's plot of log log(C0'/C0'ÿ q'm') vs log t for MCP adsorption. Temp. = 2520.18C;m' = 20.0 g/l.


sion (as the rate-controlling step) on the adsorption

process.

Dynamic modelling of chlorophenols uptake on

bituminous shale showed that Lagergren's ®rst-

order rate equation (Haribabu et al., 1993):

ln�qe ÿ q�

qe� ÿkads � t �2�

[where qe and q are the equilibrium and instan-

taneous adsorbate concentrations in the sorbent

(mg/g), respectively, t is the time (h) and kads is the

1st order rate constant (hÿ1)] was applicable yield-

ing an almost constant slope for the semilogarith-

mic linear curve (see Fig. 3 and 4). The calculated

rate constants were nearly independent from and

slightly dependent on the initial solution concen-

trations (C0), for MCP and DCP, respectively. The

pseudo-®rst order rate constants computed at 95%

con®dence level were kads=(0.21120.008) hÿ1 for

MCP and kads=(0.31320.024) hÿ1 for DCP. The

linear plots drawn according to equation 2 did not

strictly pass through the origin possibly because the

qe values dependent on the initial concentration

(C0) of the adsorbate were well below the mono-

layer capacities found by equilibrium modelling and

the slight dependence of kads on C0 for DCP may

be indicative of a more complex reaction which

may be approximated by a pseudo-®rst order rate

expression.

Since the initially rapid reaction slowed down

during the later stages of adsorption, Bangham's

equation as suggested by Aharoni et al. (1979) of

the form:

log log

�C00

C00 ÿ q 0m 0

�� log

k0m0

2:303V� a log t �3�

[where C0' is the initial concentration of adsorbate

in solution (mmol/l), V is the volume of solution

(ml), m' is the weight of sorbent used per liter of

solution (g/l), q' is the amount of adsorbate retained

at time t (mmol/g), a(<1) and k0 are constants] was

tested for its applicability to chlorophenols adsorp-

tion. The double logarithmic plot according to

equation 3 yielded perfectly linear curves (see Fig. 5

and 6) showing that the di�usion of adsorbate into

the pores of the sorbent basically controls the

adsorption process.

However when the role of pore-di�usion as the

single rate-controlling step was tested by the aid of

Weber and Morris' method (Weber and Morris,

1963);

q � kd � t1=2 �4�[where kd is a constant], the curved plots covering

the initial phase of adsorption (not shown) did not

pass through the origin hinting that pore di�usion

may not be the only rate-controlling step in the

removal of the adsorbate, especially for the early

stages of adsorption (Singh et al., 1988). This was

particularly true for DCP adsorption for which the

intercept values were higher and the linearity coe�-

cients were lower than those of MCP. This may be

attributed to the structural features, e.g. relative po-

larity, of DCP.

Fig. 6. Bangham's plot of log log(C0'/C0'ÿ q'm') vs log t for DCP adsorption. Temp. = 2520.18C;m' = 20.0 g/l.


E�ect of pH

While an acidic-to-neutral solution has no e�ect

on the phenols adsorption capacity of spent oil

shale, a highly basic solution reduces the adsorb-

ability (Darwish et al., 1996). The bituminous shale

of this study approximately showed 58 and 75%

adsorption for MCP and DCP, respectively, (from

a 25 ppm solution of the phenol at a liquid-to-solid

ratio of 50) at pH < pKa of the corresponding phe-

nols [the pKa values are 8.48 for MCP and 7.85 for

DCP (Lee and Ku, 1996)], i.e. the relative abun-

dances of the phenolates (conjugate bases of the

phenols) were negligible in the weakly acidic-neutral

region. However, starting from a pH of 9.0, the

aqueous mixtures containing the sorbent showed

turbidity and colour, whereas in strongly basic sol-

ution, no phenol adsorption occurred probably due

to the dissolution of phenolates in the aqueous

phase. It may be concluded that the reported

adsorption values apply for a wide pH range into

which most wastewater samples fall and the distri-

bution coe�cients of the phenols are fairly constantin this pH range.

E�ect of temperature

The percentage adsorption at equilibriumincreased with temperature for both chlorophenols(See Table 1) indicating the endothermic nature of

adsorption.First the adsorption isotherms (qe vs Ce, repre-

senting the sorbent and solution concentrations of

the adsorbate at equilibrium, respectively) weredrawn for 5 di�erent temperatures (25, 35, 45, 55and 658C) from which the corresponding Ce values

for a ®xed qe were extracted. The enthalpy changeof adsorption (DH0) may be found by the relation-ship (Namasivayam and Ranganathan, 1993)

ln Ce ��ln qe ÿ DS 0

R

�� DH 0

R� 1T

�5�

where DS0 and DH0 are the entropy (in

J Kÿ1 molÿ1) and enthalpy change (in J molÿ1) ofadsorption, respectively; T is the absolute tempera-

Table 1. The variation of equilibrium adsorption percentages of chlorophenols with temperature. pHi=6.3±5.9(6.0±5.7) for MCP (andDCP) depending on initial concentrations; t = 8 h; madsorbent=1 g/50 ml

Adsorption percentage of MCP (and DCP) at temperature (8C)

Initial concentration of phenol(ppm) 25 45 65

25 58% (75%) 63% (82%) 65% (86%)50 55% (73%) 61% (79%) 63% (82%)75 53% (70%) 58% (76%) 60% (81%)100 51% (68%) 57% (75%) 58% (78%)

Fig. 7. ln Ce vs 1/T plots of chlorophenol adsorption at three constant qe values (1.5, *, w; 2.0, Q, q;2.5, R, r mg/g) to compute the thermodynamic parameters, DH0 and DS0. t = 8 h; madsorbent=1.0 g/

50 ml (the ®lled and empty symbols belong to MCP and DCP data, respectively).


ture (in K) and R is the universal gas constant(equal to 8.314 J Kÿ1 molÿ1 ). Thus, ln Ce values for

a ®xed qe were plotted against 1/T values for both

chlorophenols (See Fig. 7) with linearity coe�cientsr>0.997, enabling the calculation of thermodyn-

amic parameters with reasonable precision as

described for calculating the standard deviation ofthe slope and intercept of a linear regression

equation (Miller and Miller, 1994). The mean DH0

values were calculated as (6.520.5) kJ molÿ1 for

MCP and (12.620.6) kJ molÿ1 for DCP. The DS0

values, though less reliable, were found to liebetween (ÿ1 and ÿ3) J Kÿ1 molÿ1 for MCP and

(23±30) J Kÿ1 molÿ1 for DCP (see Table 2). The

enthalpy change (DH0) for both adsorbates werepositive, con®rming the endothermic nature of the

process. Due to the relatively weak adsorbent±ad-sorbate interactions (Haribabu et al., 1993), both

chlorophenols adsorption processes should be

regarded as physical adsorption rather than chemi-sorption since the heat of adsorption was less than

020 kJ molÿ1, a critical value for distinguishing the

two mechanisms (Gu et al., 1994). However,entropy de®nitely increased (DS0>0) with DCP

adsorption probably owing to the more polar

nature of this compound. The dipole±dipole inter-actions between the adsorbent and adsorbate may

e�ectively reduce the hydration numbers of both,

increasing DS as water molecules are released intoaqueous solution. The increased a�nity of the sor-

bent to the more polar DCP may arise from theslightly polar bituminous shale surface which may

contain some carbon±oxygen complexes as those of

activated carbons (Yenkie and Natarajan, 1991).The shale matrix-bound aluminosilicates, e.g. plagi-

oclase, which may not be removed by acid-washing,

as revealed by electron microscopy of this work,may also be responsible for the solute±sorbent in-

teractions of dipolar nature. A similar di�erencewas observed between the adsorption behaviour of

phenol and chlorophenol on carbon (McKay et al.,

1985) where the presence of the chloro-substituenton phenol was assumed to produce a more polar

charge over the molecule and enhance its a�nity

Table 2. Thermodynamic parameters, DH0 (enthalpy) and DS0 (entropy change) of adsorption. t = 8 h; madsorbent=1 g/50 ml

Equilibrium concentrationof the sorbent, qe (mg/g)

Thermodynamic parameters

MCP DCP

DH0 (kJ molÿ1) DS0 (J Kÿ1 molÿ1) DH0 (kJ molÿ1) DS0 (J Kÿ1 molÿ1)

1.5 6.720.4 ÿ0.920.3 13.820.8 29.822.32.0 6.520.5 ÿ2.020.8 12.620.6 24.921.52.5 6.220.5 ÿ3.220.9 12.320.6 23.221.2

Fig. 8. Linearized Langmuir adsorption isotherms for MCP at varying temperatures (25, *; 45, Q and65, R 8C). t = 8 h; madsorbent=1 g/50 ml.


for adsorption at the sorbent surface. A similar case

reported in literature was the increase in the parti-tioning coe�cients of chlorophenols onto organo-philic clays with increasing number of Clÿsubstituents to the phenolic ring (Mortland et al.,1986).

Equilibrium modelling

The qe vs Ce data were correlated with linearizedadsorption isotherms, the highest correlation being

obtained with the Langmuir isotherm which is typi-cal for the adsorption of most organic compoundsfrom dilute aqueous solutions (McKay et al., 1985).

The Langmuir equation is expressed as (Panday etal., 1985; Diamadopoulos et al., 1993):

qe � Q0bCe

1� bCe�6�

where the Langmuir parameters, Q0 and b, relatingto monolayer adsorption capacity and energy ofadsorption, respectively (Periasamy and

Namasivayam, 1994), can be calculated from the

Ce/qe vs Ce plot;

Ce

qe��

1

Q0

�Ce � 1

�Q0b� �7�

by the relationships:

Q0 � slopeÿ1 and b � Interceptÿ1 � slope �8�The linearized Langmuir plots according to

equation 7 are shown in Fig. 8 and 9. The

Langmuir parameters were calculated by the aid of

equation 8 and depicted in Table 3.

The adsorption capacity due to monolayer cover-

age (Q0) was 9.221.4 mg/g for MCP and

9.220.8 mg/g for DCP at 258C. The Langmuir

parameter (b), related to energy of adsorption,

increased with temperature for both adsorbates,

though much more e�ectively for DCP probably

due to enhanced solute±sorbent interactions of

dipolar nature (see Table 3).

The favourable nature of adsorption can be

expressed in terms of a dimensionless separation

factor of equilibrium parameter, which is de®ned

by:

RL � 1

�1� bC0� �9�

where b is the Langmuir constant introduced in

equation 6 and C0 is the initial concentration of the

adsorbate in solution (McKay et al., 1982). All RL

Fig. 9. Linearized Langmuir adsorption isotherms for DCP at varying temperatures (25, *; 45, Q and65, R 8C). t = 8 h; madsorbent=1 g/50 ml.

Table 3. Langmuir parameters, Q0 (mg/g) and b (l/mg). t = 8 h;madsorbent=1 g/50 ml

T (8C) MCP DCP

259.221.4 and

(8.220.4)� 10ÿ39.220.8 and

(18.820.6)� 10ÿ3

4510.621.3 and

(8.520.3)� 10ÿ39.221.2 and

(27.421.7)� 10ÿ3

659.521.2 and

(10.820.4)�10ÿ39.222.3 and

(37.924.9)� 10ÿ3


values for chlorophenol uptake were less than 1 in-dicating favourable adsorption.The magnitude of the enthalpy change of adsorp-

tion (DH0) found by equation 5 may be con®rmed

by plotting ln b vs 1/T which should yield a straightline of slope (ÿDH/R) according to the relationship(Haribabu et al., 1993; Leyva-Ramos et al., 1995):

ln b � ln b 0 ÿ DH�RT � �10�

The variation of b values (in Table 3) with tem-perature has been evaluated with respect toequation 10 yielding positive DH values of 5.6 and

14.6 kJ molÿ1 for MCP and DCP, respectively, inagreement (within 10%) with previously foundvalues by the aid of equation 5. These ®ndings

recon®rm the stronger a�nity of DCP to the activesites of the adsorbent surface than MCP, probablydue to increased polarity of the DCP molecule

(McKay et al., 1985; Yenkie and Natarajan, 1991).

Adsorption capacities and desorption

The adsorption capacities were determined usingcolumn experiments data by integrating the upperpart of concentration vs throughput volume curves

(See Fig. 10 for the breakthrough curves of DCP)obtained at an elution rate varying between 1±3 ml minÿ1. The total integrated amount of adsor-

bate was divided by the weight of the sorbentplaced in the column to yield the adsorption ca-pacities of 3.1 and 4.2 mg/g for MCP and DCP, re-spectively. Since these capacities were quite lower

than the Langmuir monolayer capacities presentedin Table 3, it may be inferred that full saturation ofthe sorbent active sites was not achieved due to thelimited time of equilibration achieved under

dynamic column conditions (normally equilibrationwould take a relatively long time as observed inFigs 1 and 2). Another factor causing the discre-

pancy may be the partial invalidity of the Langmuirassumption, i.e. envisaging monoenergetic adsorp-tion on a homogeneous surface, on the inhomo-

geneous surface of the bituminous shale as acomposite sorbent.The retained adsorbate (DCP) was completely

desorbable with water as in the case of trichloro-benzene adsorption by natural sediments (Wu andGschwend, 1986), i.e. 6 g of DCP-loaded sorbentwas subjected to desorption to elute all the retained

adsorbate with 1100 ml of distilled water. Thus,adsorption was completely reversible, recon®rmingthe physical character of adsorption.

CONCLUSIONS

(i) The adsorption of 2-chlorophenol and 2,4-

dichlorophenol from aqueous solution on to bitumi-nous shale conforms to a Langmuir equation basedon the formation of a monomolecular layer.

(ii) The adsorption of both chlorophenols on tobituminous shale follows ®rst-order kinetics withpore-di�usion being the essential rate-controllingstep.

Fig. 10. The breakthrough curves of DCP for a bituminous shale-®lled column at various ¯owrates(1.0, *; 2.0, Q and 3.0, R ml/min). Temp. = 2520.18C); madsorbent=6.0 g. Ci=in¯uent concentration;

Ce=e�uent concentration; Ve=e�uent volume; Ce/Ci=relative concentration of e�uent.


(iii) Acid-activated bituminous shale is a highera�nity adsorbent for 2,4-dichlorophenol due to the

polarity of the DCP molecule giving rise to strongerattraction to the sorbent surface.(iv) Adsorption is endothermic as DH values are

positive. Since DH is relatively small in magnitude,the forces of uptake are weak, i.e. adsorption is pre-dominantly of physical character.

(v) The fact that 2,4-dichlorophenol adsorption isreversible has been con®rmed by column desorptiontests. Thus, bituminous shale may serve as an ana-

lytical preconcentration material for DCP.(vi) The dynamic adsorption capacity of bitumi-

nous shale for 2-chlorophenol and 2,4-dichlorophe-nol has been found as 3.1 and 4.2 mg/g, respectively

(these values are appreciably below the Q0 par-ameters-related to monolayer capacity- calculatedby Langmuir modelling of adsorption).

AcknowledgementsÐThe authors wish to thank ProfessorEkrem Ekinci et al. from the Chemical EngineeringDepartment of IÇstanbul Technical University for provid-ing the bituminous shale samples. Thanks are also due toDr BuÈ lent Arman from S° is° e-Cam Research Laboratorieswho performed the mineralogical characterization of thesorbent.

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Adsorptive removal of chlorophenols from water by bituminous shale

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