Journal of Alloys and Compounds 645 (2015) 398–404

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Journal of Alloys and Compounds

journal homepage: www.elsevier .com/locate / ja lcom

Synthesis of magnetite nanoparticles from mineral waste

http://dx.doi.org/10.1016/j.jallcom.2015.05.0890925-8388/� 2015 Elsevier B.V. All rights reserved.

⇑ Corresponding author.E-mail addresses: velsak_r@yahoo.com, rsakthivel@immt.res.in (R. Sakthivel).

Rohit Kumar a, R. Sakthivel a,⇑, Reshma Behura a, B.K. Mishra a, D. Das b

a CSIR – Institute of Minerals and Materials Technology, Bhubaneswar 751 013, Indiab UGC-DAE Consortium, Kolkata, India

a r t i c l e i n f o

Article history:Received 24 November 2014Received in revised form 28 April 2015Accepted 11 May 2015Available online 16 May 2015

Keywords:Mineral wasteIron ore tailingsMagnetite nanoparticlesSaturation magnetizationAntibacterial property

a b s t r a c t

Magnetite nanoparticles were synthesized from iron ore tailings – a mineral waste collected from theiron ore processing plant. Mechanical milling followed by chemical route is employed to obtain themagnetite nanoparticles from the waste. The magnetite nanoparticles were characterized by X-raydiffractometer, Field Emission Scanning Electron Microscope, Fourier Transform Infrared Spectrometerand Vibrating Sample Magnetometer. X-ray diffraction pattern confirms the existence of a magnetitephase. Field Emission Scanning Electron Microscopic (FE-SEM) pictures reveal that the particle size isbelow 100 nm. Fourier Transform Infrared (FTIR) spectrum shows a band at 570 cm�1 for the Fe–O bondvibration. Vibrating Sample Magnetometric (VSM) study shows high saturation magnetization value of60 emu/g at low applied magnetic field. Silver coated magnetite nanoparticles exhibits antibacterialproperty whereas bare magnetite does not.

� 2015 Elsevier B.V. All rights reserved.

1. Introduction

Enormous quantity of iron ore tailings is disposed off as a min-eral waste from the iron ore processing industries due to rapidlyincreasing demand and growth of iron and steel industries inIndia. It has been reported that �18–20 million tons of tailingsper year in India [1]. Since it does not have direct or indirect com-mercial use, it gradually keeps on accumulating. Safe disposal ofthis waste is most essential as it occupies a larger area that resultsin land pollution. Due to the fine nature of its particles, it easilycontaminates the ground water as well as various water bodiesthrough rain and by wind; it ultimately affects the human beingsand aquatic animals [2]. Therefore, more efforts are needed to uti-lize this waste for its possible applications. Indian iron ore tailingsgenerally contain 26.8% Fe2O3, 72.4% SiO2 and 0.7% Al2O3. As it con-tains high amount of SiO2 (>80%), it is suggested as a raw materialfor construction, ceramics, glass, and to make a new class of silicate[3,4]. Effort has been made to prepare försterite from iron ore tail-ings due to its wider applications as it has good creep stability, highrefractory temperature and also it provides better thermal insula-tion [5]. This observation has given the scope for effective utiliza-tion of tailings for the preparation of value added materials.Extraction of iron from tailings and converting that into productsthat are more valuable can find wider applications. If the hematitecontent of iron ore tailings is converted into magnetite

nanoparticles, it can find its suitability in various applications.Magnetite nanoparticles find applications in the field of catalysis[6], information storage [7], adsorption [8], medicine [9],nano-tagging [10], ferrofluids [11], removal of heavy ions likearsenic from water [12] and even in the field of biomedicalapplications like magnetic separation [13], drug delivery [14],hyperthermia treatments [15] and magnetic resonance imaging(MRI) contrast enhancements [16]. In the literature, variousmethods such as sol–gel [17], thermal decomposition [18],co-precipitation [19,20], reverse micelles [21,22], and hydrother-mal synthesis [23] are reported for the synthesis of magnetitenanoparticles. However, the main challenges lie in obtainingdesired shape and narrow size distribution of particles as they playa critical role in their practical applications [24]. Some control onthese parameters could be achieved by optimizing the parameters[25,26] such as reaction temperature, pH, reaction time and theenvironment maintained for synthesis. Other than chemical meth-ods, mechanical milling approach is also suggested by de Carvalhoet al. [27] and Zhang et al. [28], in which they reported that themilling of metallic iron powder with distilled water at variablemilling times results in formation of a variable size range(12–20 nm) of magnetite nanoparticles; reaction involved in thismethod is given below.

3Feþ 4H2O! Fe3O4 þ 4H2 ð1Þ

Alcalá et al. [29] demonstrated that hematite could betransformed into magnetite by milling it with iron according tothe following reaction scheme:

R. Kumar et al. / Journal of Alloys and Compounds 645 (2015) 398–404 399

4Fe2O3 þ Fe! 3Fe3O4 ð2Þ

Mechanical milling is a very simple technique unlike chemicalmethods that involve optimizing parameters like pH, reaction tem-perature, filtration, washing, etc. In that direction, in our previousstudy, we attempted to prepare magnetite out of iron ore tailingsthrough mechanical milling with iron powder as a reductant.Unfortunately, we failed to obtain the desired magnetite product;instead ended up obtaining undesired fayalite (Fe2SiO4) phasedue to the interference of the high amount of silica (SiO2) in thetailings during mechanochemical reaction [30]. Inhibition of thisside reaction of silica becomes very difficult since the mechanicalmilling is not under thermodynamic equilibrium condition. Toovercome this issue, in this investigation, we adopted a suitablemethod involving both physical and chemical approaches fortransforming hematite portion of tailings into magnetite nanopar-ticles. It has been reported that magnetite is used in cancer therapydue to its good biocompatible nature and also used as a support formetal nanoparticles [31]. Silver nanoparticles exhibit excellentantimicrobial and antibacterial activity without light. Its antibacte-rial activity increases with the size reduction, but there is a greatrisk in using these finer nanoparticles because of removal difficul-ties after their use. Its persistence in the mammiferous cells causesargyrosis and argyria [32,33]. It can also cause clinical toxicity inhuman even at lower concentration of 100 ppb [34]. Hence, inthe water purification process, use of silver nanoparticles toremove bacteria is restricted. So there is a need to develop suitablemethod to eradicate this practical difficulty. Here, we demonstratethe synthesis of magnetite nanoparticles from mineral waste andusing it as a support for silver nanoparticles for its application inremoval of bacteria from water.

2. Materials and methods

Iron ore tailings collected from the iron ore processing plant contain about26.8% Fe2O3, 72.4% SiO2 and 0.7% Al2O3. In order to convert hematite (Fe2O3) portionof tailings into magnetite, an appropriate amount of iron was added. The molar con-centration ratio of added Fe to Fe2O3 content of tailings was maintained at 1:4. Thenthis mixed sample was subjected to ball milling for 2 h for uniform mixing/distribu-tion of iron in the tailings. The sample obtained after milling was transferred into around bottom flask, subjected to acid digestion at 95 �C for 4–5 h with addition ofrequired amount of hydrochloric acid solution and cooled down to room tempera-ture. During acid digestion, iron (III) leached out from the tailings as iron (III) chlo-ride and a portion of it reacted with metallic Fe mixed in the tailings to form iron (II)chloride solution. These two processes happened simultaneously and resulted inthe formation of 2:1 M ratio of iron (III) and iron (II) chloride solution. Then, thissolution was separated out from the acid insoluble residue by filtration. After sep-aration, the obtained solution was quantified for both Fe (III) and Fe (II) by standardwet chemical analysis and was found that they are in the 2:1 M ratio. This solutionwas transferred into a round bottom flask and sufficient amount of urea was addedto it. It was refluxed at 95 �C until black colored fine particles of magnetite wasobtained. During this process, color of the solution was changed from brown toblack due to changes in the pH by slow release of NH3 by the decomposition of urea.Then, it was cooled down to room temperature and fine magnetite particles wereseparated out from aqueous solution by magnetic separation and washed withde-oxygenated distilled water to remove chloride followed by alcohol to removemoisture and dried in a vacuum desiccator at room temperature. A schematic rep-resentation for preparation of magnetite nanoparticles from tailings is given above.

A portion of magnetite nanoparticles was coated with silver nanoparticles byincipient wet impregnation of aqueous silver acetate followed by sonication, wash-ing and drying. Since the obtained Ag-functionalized magnetite (Ag/Fe3O4) ishydrophobic in nature, it was converted into hydrophilic by mixing it with 10wt.% aqueous tetra methyl ammonium hydroxide up on stirring, sonication andwashed with a mixed solution containing 8:1:1 of acetone, ethanol and distilledwater respectively [35]. Amount of silver on magnetite nanoparticles was main-tained at 1 wt.% and the same was used for antibacterial activity.

Antibacterial activity of Fe3O4, hydrophobic and hydrophilic Ag–Fe3O4 nanoma-terials was tested against Escherichia coli (reference bacterial strain MTCC-739).Qualitative antibacterial investigation was carried out by using spot inoculationmethod in which sample was placed as a spot on the petri dish containing E. colicultured in agar media. After its incubation period of 24 h at 37 �C, the zone of inhi-bition area indicating E. coli destruction was measured. For quantitative estimationof antibacterial property, a test solution was prepared by dispersing 1 mg/ml of

sample in 25 ml sterilized tap water containing initial E. coli concentration of 107

CFU/ml. 1 ml of this test solution was drawn at various time intervals and dilutedserially up to 10�4 dilution. Then 0.1 ml of this diluted solution was spread evenlyover an agar plate with the help of a sterile L-shaped glass rod. These agar plateswere allowed to undergo incubation at 37 �C for 24 h. Then the number of bacterialcolonies formed was counted. All antibacterial tests were carried out under darkcondition at ambient atmosphere.

X-ray diffraction (XRD) studies were performed using X-ray powder diffrac-tometer (Panalytical Instrument-Model: X’ pert Pro, Netherland) using Co Ka radi-ation (k = 1.78901 Å) having programmable divergence slit. The diffractometer wasoperated at 40 kV and 30 mA. Diffractograms were recorded from 10� to 80� 2h witha scan speed of 2.15 s/step and step size of 0.05� (2h). The diffraction lines were ana-lyzed for different phases present in the sample using Highscore™ software avail-able with the instrument. For identification of functional groups present in thesample, Fourier Transform Infrared (FTIR) spectrometer (spectrum GX PerkinElmer, resolution 4 cm�1) was used to record the spectrum from 400 to4000 cm�1. Before recording the spectrum, KBr spectrum was taken as a referenceand then sample mixed with KBr was measured. Thermogravimetry analysis ofsample was carried out with Mettler Toledo (TGS/SDTA851e) instrument at a heat-ing rate of 20 �C/min. About 15 mg of sample was used for TGA measurement.Further confirmation of phases present in the sample, room temperatureMössbauer spectrum was recorded with Mössbauer spectrometer using a 57Cosource in a constant-acceleration transmission. The spectrometer was calibratedwith a standard a-Fe foil. The morphology and elemental characterization of vari-ous samples were carried out through Field Emission Scanning ElectronMicroscope (Zeiss Supra55). The samples for FE-SEM studies were prepared by dis-persing the sample in ethanol by sonication and this homogenous solution was dis-persed on an aluminum foil support. Magnetic property of the sample wasevaluated through a Vibrating Sample Magnetometer (PAR 155) at roomtemperature.

3. Results and discussions

X-ray diffraction pattern of iron ore tailings shown in Fig. 1reveals that the sample is crystalline and shows diffraction peakscorresponding to hematite (Fe2O3) and quartz (SiO2) phases.Presence of these phases is confirmed by matching the observeddiffraction peaks with standard powder diffraction patterns ofhematite (JCPDS F. No. 85-0599) and quartz (JCPDS F. No.86-1630). It is noticed that the intensity of diffraction peaks ofquartz is more prominent than hematite indicating that quartzexists as major phase and hematite as minor. Acid leached residueobtained after acid digestion of mixed iron ore tailings and ironpowder followed by solid–liquid separation shows diffractionpeaks only for quartz phase (Fig. 1). It reveals that both mixed ironand hematite phase in the tailings are leached out completely dur-ing acid digestion. X-ray diffraction pattern of magnetite

Fig. 2. X-ray powder diffraction pattern of magnetite nanoparticles.

400 R. Kumar et al. / Journal of Alloys and Compounds 645 (2015) 398–404

nanoparticles synthesized from acid leached solution is shown inFig. 2. It shows very prominent diffraction peaks, which are wellmatched with the standard powder diffraction pattern of mag-netite (JCPDS F. No. 19-0629) as a single phase. Broadness ofdiffraction peaks indicates the nano-crystalline nature of the sam-ple. The average crystallite size calculated from the diffractionpeaks using the following Debye–Scherrer formula is found to be14 nm.

D ¼ Kkb � cos h

where K = 0.94, k is the wavelength of X-ray, b is full width halfmaximum (FWHM) of the peak, h is the diffraction angle.

Lattice parameter calculated from the X-ray powder diffractiondata using the following equation shows the value 8.394 Å and thisis in good agreement with the values reported in the standardJCPDS F. No. 19-0629.

a ¼ dffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffih2 þ k2 þ l2

q

FE-SEM images of uncoated and Ag coated magnetite nanopar-ticles are shown in Fig. 3. It shows that particles are well dis-tributed and has nearly spherical morphology with narrowparticle size range from 50 to 60 nm [36]. Since capping reagentis not used during the synthesis, the particles show a high ten-dency for agglomeration due to its fineness. The size of the parti-cles seen from FE-SEM corresponds to the overall polycrystallinematerial, while that determined from XRD is related to the crystal-lite size. Evidence for coating of Ag on magnetite nanoparticles arewell noticed in Fig. 3a. Fig. 3b shows the EDS spectra of Fe3O4 andAg–Fe3O4 nanoparticles. It reveals peaks for Fe, Al, and O in boththe samples whereas an additional peak for Ag confirms the pres-ence of Ag in Ag–Fe3O4 composite. Peak observed for Al is due toaluminum foil support used in the sample preparation beforeFE-SEM study. The FTIR spectra (Fig. 4) show a distinct absorptionband at 608 cm�1 corresponding to intrinsic stretching vibrationsof Fe–O bond at the tetrahedral site (Fetetra M O) of magnetite.Similar observation has been reported for magnetite nanoparticles[37,38]. Whereas bands observed at around 3650 cm�1 and1660 cm�1 corresponds to OH stretching and OH bending ofadsorbed water molecule in the lattice respectively. Whereas otherbands observed at 3750 and 1023 cm�1 are for OH stretching andbending mode of hydroxyl group in akaganéite. The characteristic

Fig. 1. X-ray powder diffraction pattern of iron ore tailings mixed with iron powderand its acid insoluble residue after acid digestion.

bands of akaganéite are observed at around 670 and 880 cm�1

which are correspond to OH� � �Cl hydrogen bond and OH respec-tively [39,40]. The translational stretching of Fe–O bond vibrationin akaganéite is noticed at 464 cm�1 [41]. The bands observed inthe region 1430 cm�1 are attributed to adsorbed anionic specieslike carbonates on the surface of magnetite. The adsorbed carbon-ate species could have come from the decomposition of urea

Fig. 3a. FE-SEM micrographs of (a) uncoated Fe3O4 and (b) Ag coated magnetitenanoparticles.

Fig. 3b. EDS spectra of Fe3O4 (left) Ag–Fe3O4 (right) nanoparticles.

Fig. 4. FTIR spectra of (a) bare magnetite, (b) hydrophobic Ag coated magnetite and(c) hydrophilic Ag coated magnetite nanoparticles.

Fig. 5. TGA curve of uncoated magnetite nanoparticles.

R. Kumar et al. / Journal of Alloys and Compounds 645 (2015) 398–404 401

during hydrolysis. It is observed that the band at 1023 cm�1 in caseof magnetite sample gets disappeared in case of Ag/Fe3O4 samplesand it might be due to Ag coating and conversion of hydrophobic tohydrophilic nature brought by tetra methyl ammonium hydroxidetreatment. TGA curve of magnetite sample is shown in Fig. 5. Itindicates the two stages of weight loss up to 375 �C, one up to150 �C and another between 200 and 375 �C. The first stage ofweight loss accounts for removal of physically adsorbed watermolecules whereas second stage for dehydration of b-FeOOH phasepresent as an impurity phase in the sample. The percentage ofweight loss found to be 0.62% at second stage and it accounts for6.12% quantity of b-FeOOH in the magnetite sample.

4. Magnetic property

To find out qualitative determination of its magnetic property,the synthesized magnetite nanoparticles dispersed in hexane andplaced near the magnet. Fig. 6a shows that the dispersion of mag-netite nanoparticles in the absence and presence of magnetic field.

It clearly demonstrates that the well dispersed particles in hexanein the absence of magnetic field get attracted after application ofmagnetic field. Quantitative magnetic property of magnetitenanoparticles is shown as M–H curve in Fig. 6b. It shows the satu-ration magnetization value of 60 emu/g. This saturation magneti-zation is very much sensitive to the particle size. Usually, whenthe size of particles reduced to nanometer range, its magneticproperties reduce drastically and they exhibit super paramagneticbehavior [42]. When we deal with fine particles, magnetization isgenerally characterized by two parameters viz., remanence andcoercivity. Between them, coercivity is more important as it isstrongly dependent on the particle size. Initially, when the particlesize reduces to a critical value from larger size, coercivity increasesup to a certain maximum value, after that it starts decreasingrapidly as it becomes a single domain system and it completelyvanishes to exhibit super-paramagnetic behavior [43]. The coerciv-ity and remanence of the magnetite nanoparticles studied in thisinvestigation are 23 Oe and 4 emu/g respectively and these obser-vations indicate that the sample approaches towards superparam-agnetic behavior. Magnetic property and particle morphology of

Fig. 6a. Magnetite nanoparticles dispersed in hexane before (left) and after (right)application of magnetic field.

Fig. 6c. Comparative VSM curve of magnetite and Ag coated magnetitenanoparticles.

402 R. Kumar et al. / Journal of Alloys and Compounds 645 (2015) 398–404

magnetite nanoparticles obtained from the tailings is very muchsimilar to those synthesized from hydrothermal method [44]. Thesaturation magnetization value of 65 emu/g is reported for themagnetite having an average particle size of 70 nm with sphericalshape, whereas magnetite particles studied in this investigationshow 60 emu/g for the particle size range of 50–60 nm with thesame morphology. A comparative VSM curve of uncoated and sil-ver coated magnetite is shown in Fig. 6c. It shows that silver coat-ing of magnetite reduces the saturation magnetization value from65 to 55 emu/g but this trend becomes reverse in case of coercivityvalues. Bare magnetite has coercivity value of 23 Oe, whereasAg/Fe3O4 has 74.3 Oe. This reduction in the saturation magnetiza-tion and increased coercivity values brought by silver coating couldbe due to the reduction in overall magnetic phase concentrationand also by the interaction of nonmagnetic silver with magneticphase. These observations are in good agreement with literaturereported for Ag/Fe3O4 [45,46]. Hence, the synthetic procedureadopted in this investigation is comparatively more facile in natureand requires less temperature compared to hydrothermal methodreported in the literature [44] to generate good quality magnetitenanoparticles from the mineral waste, which follows the conceptof waste to wealth.

Fig. 6b. VSM curve of magnetite nanoparticles.

Fig. 7. Mössbauer spectrum of magnetite nanoparticles.

Mössbauer spectrum of magnetite nanoparticles obtained atroom temperature is shown in Fig. 7. It shows mainly two sextetscorresponding to the various oxidation states of Fe in magnetite.These observed peaks are in good accordance with the reported lit-erature [47]. Magnetite (Fe3O4) has inverse spinel structure withfcc close packed oxygen anions and Fe cations occupying at inter-stitial tetrahedral and octahedral sites [48]. The magnetite is repre-sented with the formula [Fe3+]A [Fe2+

1 �3x Fe3+1+2x hx]B O4 with x = 0, h

for vacancies, where A and B designate tetrahedral and octahedralsites respectively. Two sextets observed in the spectrum can beresolved into one for high spin Fe3+ ion on the tetrahedral sites(Bhf = 487.66 kOe) and the other one for Fe2+ ion on the octahedralsite (Bhf = 455.67 kOe). The rapid electron hopping between Fe2+

and Fe3+ ions in the octahedral site at room temperature is account-able for good thermal conductivity which makes magnetite animportant class of semi-metallic materials [49]. The isomer shift(IS) value of 0.37 mm s�1 observed from the Mössbauer spectrumconfirms the presence of Fe3+ ions in A and B-sites, whereas otherIS value, 0.56 mm s�1 is the characteristic for Fe2+ ions in B-site.

Table 1Mössbauer parameters of magnetite nanoparticles measured at room temperatures(isomer shift, IS given in mm/s, quadrupole splitting De given in mm/s, Hhf is thehyperfine magnetic field given in kOe, and RAA is relative absorption area of variouscomponents of the spectrum given as percentages).

Sample Components RAA(%)

IS(mm/s)

De(mm/s)

Hhf (kOe)

Magnetite(Fe3O4)

Fe3+

(tetrahedral site)46.08 0.37 0.05 487.66

Fe2+, Fe3+

(octahedral site)45.25 0.56 �0.05 455.67

Akaganéite(b-FeOOH)

Fe3+ 5.66 0.35 0.66

Fig. 9. Quantitative antibacterial activity of various samples.

R. Kumar et al. / Journal of Alloys and Compounds 645 (2015) 398–404 403

These IS values (Table 1) are very much close to the reported valuefor magnetite [50]. However, weak features observed in the middleof the spectrum are the indications for the presence of trace amountsof other phase which might be akaganéite (b-FeOOH) as its IS value,0.35 mm s�1 matches for the Fe3+ of b-FeOOH [51]. Formation of aka-ganéite/goethite is quite possible due to magnetically induced oxida-tion of Fe2+ on the octahedral site (from a low spin state Fe2+ to ahigh spin state Fe3+) during magnetic separation of magnetitenanoparticles from aqueous solution [52]. Existence of b-FeOOHphase confirmed from TGA and FTIR studies is well supporting theMössbauer results. Further, it can be stated that the concentrationof b-FeOOH phase determined from TGA and Mössbauer spectrumare almost identical.

E. coli, a gram-negative bacterium, is used to investigate the rel-ative antibacterial activity of Fe3O4, hydrophobic Ag–Fe3O4 andhydrophilic Ag–Fe3O4 nanomaterials. Qualitative insight on the rel-ative antibacterial property of these samples made with spot inoc-ulation method is shown in Fig. 8. It reveals that Fe3O4 does notshow any zone of inhibition area, whereas hydrophobic Ag–Fe3O4

and hydrophilic Ag–Fe3O4 exhibit significant zone of inhibitionarea confirming the role of Ag on Fe3O4. However, hydrophobicAg–Fe3O4 exhibits relatively less activity than hydrophilic Ag–Fe3O4. The quantitative antibacterial activity of these samplesexamined with respect to various time intervals up to 120 min(Fig. 9) shows that bare Fe3O4 does not show any antibacterialactivity up to 120 min. However, hydrophobic Ag–Fe3O4 andhydrophilic Ag–Fe3O4 show significantly improved antibacterialactivity, particularly from 60 to 120 min. Among hydrophobicand hydrophilic Ag–Fe3O4 nano-composites, hydrophilic Ag–Fe3O4 shows superior activity indicating its preferred affinitytowards E. coli. These observations support the fact that theincrease in the hydrophobicity of the nanoparticle surface leads

Fig. 8. Relative antibacterial activity of uncoated magnetite, hydrophobic Ag coatedmagnetite and hydrophilic Ag coated magnetite nanoparticles observed throughspot inoculation method.

to a decrease in nanoparticle dispersibility in aqueous solutionswhereas the hydrophilic nanoparticles overcome this barrier dueto the high dispersibility in aqueous solutions [53]. Therefore, con-version of nanoparticle surface from hydrophobic to hydrophilic bya suitable method widens their possible potential applications[54,55]. It is reported that silver and its compounds are shown tobe effective against both aerobic and anaerobic bacteria by precip-itating bacterial cellular proteins and by blocking the microbialrespiratory chain system. There are some other possible mecha-nisms for antibacterial property of silver nanoparticles reportedare: (i) attachment of silver nanoparticles to the cell membraneand its penetration inside the bacteria, (ii) its attack on the respira-tory chain in bacterial mitochondria and leading to cell death and(iii) its sustained release of Ag + inside the bacterial cells inducingoxidative stress by generating free radicals [56 and referencestherein]. Although Ag nanoparticles exhibit excellent antibacterialactivity, it has severe limitation due to difficulty in removing themfrom the system causing nanotoxicity to human. However, this canbe overcome by anchoring it on magnetite nanoparticles thatbrings the change for easy separation by a suitable magnet in orderto reuse them for a number of times. Hydrophilic Ag–Fe3O4

nano-composite studied in this investigation could be used in theremoval of bacteria from water. Hence, magnetite nanoparticlesderived from iron ore tailings can act as a good support for silvernanoparticles to use it effectively in the water disinfection.

5. Conclusions

Iron ore tailings considered as waste from a mineral industry isused effectively as a prime raw material for the synthesis of mag-netite nanoparticles. This study demonstrates the origin of a nano-material from mineral waste. Mechanical milling followed bychemical route is employed for the facile synthesis of magnetitenanoparticles. Magnetite nanoparticles derived from waste exhibitvery prominent magnetism by showing saturation magnetizationvalue of 60 emu/g. Its surface modification with silver (Ag–Fe3O4)induces the antibacterial property, which provides a scope of itsutilization in water treatment. Therefore, Ag–Fe3O4 can become abetter option in water treatment process compared to bare silver.Overall, this paper shows the path to convert waste into wealthand also provides a possible application of the end product inwater treatment.

404 R. Kumar et al. / Journal of Alloys and Compounds 645 (2015) 398–404

Acknowledgements

Science and Engineering Research Board, New Delhi is acknowl-edged for financial support and Council of scientific and IndustrialResearch, New Delhi is acknowledged for providing infrastructuralfacilities. Diptipriya Sethi, RJNRF is acknowledged for antibacterialstudy.

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