Synthesis, Characterization and, the Heavy MetalRemoval Efficiency of MFe2O4 (M=Ni, Cu)Nanoparticles

AbstractThe purpose of the study described in this paper was to compare the removal of the heavy metals zinc,nickel, and copper from synthetic wastewater by using nanoparticles of CuFe2O4 and NiFe2O4. Thenanoparticles of nickel and copper ferrite (CuFe2O4 and NiFe2O4) were produced by the PEG assistedhydrothermal method. The structural and morphological characterizations were determined using XRD,FT-IR, and SEM. These nanoparticles were dispersed into synthetic wastewater contaminated with zinc,nickel, and copper. Once they had bound to the heavy metals, they were removed from the water solutionusing a strong magnet. The metal concentrations of the filtered samples were determined by using atomicabsorption spectrophotometry (AAS). Then the heavy metal removal efficiencies and adsorption capacitiesof the nanoparticles (CuFe2O4 and NiFe2O4) were calculated. The removal efficiencies of Cu(II), Ni(II)and Zn(II) by using CuFe2O4 nanoparticles was calculated as 83.50%, 98.85%, and 99.80%, respectively.The removal efficiencies of Cu(II), Ni(II), and Zn(II) by using NiFe2O4 nanoparticles were calculated as92.55%, 36.56 %, and 99.91%, respectively. The measurements were repeated several times with the samesample and almost the same results were obtained each time. Keywords: Adsorption, adsorption capacity, copper ferrite, heavy metal, nanoparticles, nickel ferrite.

MFe2O4 (M=Ni, Cu) Nanopartiküllerinin Sentezi, Karakterizasyonu ve Ağır Metal GiderimVerimliliği ÖzetBu makalede anlatılan çalışmanın amacı sentetik atıksulardan çinko, nikel ve bakır gibi ağır metalleringiderimini CuFe2O4 ve NiFe2O4 nanopartikülleri kullanarak incelemektir. Nikel ve bakır ferritnanopartiküller (CuFe2O4 ve NiFe2O4) PEG-destekli hidrotermal metod kullanılarak sentezlenmiştir.Nanopartiküllerin yapısal ve morfolojik karakterizasyonu için XRD, FT-IR ve SEM kullanılmıştır.Karakterize edilen nanopartiküller çinko, nikel ve bakır içeren sentetik atıksuyun içerisine bırakılmıştır. Ağırmetallerin nanopartiküllerle adsorpsiyonunun ardından güçlü bir mıknatıs ile nanopartiküller atıksudanayrılmıştır. Süzülen atıksu içerisindeki ağır metal konsantrasyonları atomik absorpsiyon spektrofotometresi(AAS) ile belirlenmiştir. Daha sonra kullanılan nanopartiküllerin (CuFe2O4 ve NiFe2O4) ağır metalgiderim verimleri ile adsorpsiyon kapasiteleri hesaplanmıştır. CuFe2O4 nanopartikülünün Cu(II), Ni(II) veZn(II) giderim verimleri sırasıyla %83,50, %98,85 ve %99,80 olarak belirlenmiştir. NiFe2O4nanopartikülünün Cu(II), Ni(II) ve Zn(II) giderim verimleri ise sırasıyla %92.55, %36.56 ve %99.91 olarakhesaplanmıştır. Deneyler aynı örnekle birçok kez tekrar edilmiş ve benzer sonuçlar elde edilmiştir. Anahtar Kelimeler: ağır metaller, adsorpsiyon, adsorpsiyon kapasitesi, bakır ferrit, nanopartiküller, nikelferrit.

Sezgin N, Sahin M, Yalcin A, Koseoglu Y (2013) Synthesis, Characterization and, the Heavy Metal RemovalEfficiency of MFe2O4 (M=Ni, Cu) Nanoparticles. Ekoloji 22(89): 89-96.

No: 89, 2013 89

Ekoloji 22, 89, 89-96 (2013)doi: 10.5053/ekoloji.2013.8911

Received: 17.01.2013 / Accepted: 14.06.2013

Naim SEZGIN1*, Musa SAHIN2, Arzu YALCIN1, Yuksel KOSEOGLU3,4

1 Istanbul University, Faculty of Engineering, Department of Environmental Engineering,34320, Avcilar, Istanbul-TURKEY2 Istanbul University, Faculty of Engineering, Department of Chemistry, 34320, Avcilar,Istanbul-TURKEY3 Fatih University, Department of Physics, Buyukcekmece 34500 Istanbul- TURKEY4 Suleyman Demirel University, Faculty of Engineering and Natural Sciences, Almaty-KAZAKHSTAN

*Corresponding author: nsezgin@istanbul.edu.tr

INTRODUCTIONThe removal of heavy metals as a pollutant in

water has been under intense research due to their

potential toxicity which causes heavier exposure forsome organism and the ecology even at very lowconcentration. The presence of heavy metals like

RESEARCH NOTE

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zinc, nickel, and copper may exhibit toxicity andcarcinogenicity for the human body. Although zincand copper are essential in small quantities, theexcess of them is hazardous to the human body(Mishra and Patel 2009). Copper in even a lowamount causes toxic effects in living cells due to thefact that copper produces oxygen species which candamage lipids, nucleic acids, and proteins (Halliwelland Gutteridge 1992). The excess of nickel maycause some health problems such as paralysis,diarrhea, low blood pressure, lung irritation, andbone defects (Kudesia 1990). The maximumconcentration limits (MCL) for some hazardousheavy metals, were constituted by the USEPA andare given in Table 1 (Babel and Kurniawan 2003).

What is needed is materials capable of effectiveadsorption. Therefore, it is also very important todevelop some processes to remove heavy metalsfrom discharged waters as a result of their release byindustry, chemical plants, mining, electroplating,paints, pesticides, agriculture, combustion of fossilfuels, and traffic (Yılmaz et al. 2006, Osma et al.2012). Various techniques currently used for heavymetal removal from discharged water are physico-chemical precipitation (Meunier et al. 2006, Djedidiet al. 2009), ion exchange (Lacour et al. 2001),solvent extraction (Li and Chen et al. 2008),adsorbents (Cokadar et al. 2003, Li and Tang et al.2008, Shahwan et al. 2010, Goren et al. 2010),reverse osmosis (Bakalar et al. 2009, Aljendeel2011), ultrafiltration (Juang and Shiau 2000),biosorption (İleri and Cakir 2006, Senturk andBuyukgungor 2013), and electrodialysis(Dermentzis 2010) along with polymeric structureslike hydrogels (Essawy and Ibrahim 2004, Sezgin2012). While there are ways to remove heavy metals,they are expensive and require extensive hardwareand high-pressure pumps that run on electricity.Nonmaterials recently have been studied for waterand wastewater treatment (Köseoğlu 2010, Ozmenet al. 2010, Mahdavi et al. 2013, Mueller et al. 2013).Nanoparticulate metal oxides are among the mostused nanoparticles (Nowack et al. 2007). Theferrospinels are interesting sorbents for the removalof heavy metals contaminants (Dixit and Hering2003). Ferrospinels have the general formula ofAFe2O4 (where A: Fe, Co, Ni, Zn, etc.) and the unitcell contains 32 O-atoms in cubic close packing with8 Td (tetra-hedral) and 16 Oh (octahedral) occupiedsites. When magnetic ferrospinels are made as

nanoparticles, the smaller particle size and highsurface area enhances its capacity for As removal(Yavuz et al. 2006). By using NiFe2O4, it obtained a90 % removal efficiency of arsenic from wastewater(Koseoglu 2010). In a study by Ozmen at al. (2010),copper(II) was removed from water by using amodified Fe3O4. The experimental results showedthat the removal efficiency of copper(II) in thepresences of co-existing ions (Pb(II), Zn(II), Ni(II),Co(II), Cr(III) etc.) were in the range of 31.6-39.6%, as a result of the competition with copper(II) foradsorption. Thus, they found that it was lower thanthat (75.3 %) with only the presence of copper(II) inthe solution.

Generally, it is known that heavy metals can beseparated from nanoparticles by desorption in aninorganic acid or alkaline medium (Afkhami andMoosavi 2010, Hao et al. 2010, Tang and Lo 2013).Thus, the heavy metals are recovered and thenanoparticles can be reused many times fordesorption. It should also be remembered thatdesorption of heavy metals from nanoparticles instrong acid or an alkaline medium may lead tonanoparticle dissolution (Yantase et al. 2007).Therefore, a weak acid medium must be used fordesorption.

Nanophase materials with an average grain sizein the range of 1 to 50 nm have attracted researchinterest for more than a decade since their physicalproperties are quite different from that of their bulkmicron-sized counterparts because of the largevolume fraction of atoms that occupies the grainboundary area (Gleiter 1989, Koseoglu and Kavas2008). The surface area of the nanostructuredmaterials is large as the grain sizes are small. Theincrease in the interfacial energy due to defects,dislocations, and lattice imperfections leads tochanges in various physical properties and henceone can tailor the materials with specific properties.Almost 50 % of the atoms reside in the grainboundary area when the grain size is reduced to lessthan 10 nm, whereas, it is only 1-3 % when the grain

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Table 1. The MCL standards for the most hazardous heavy metals.

Synthesis, Characterization and, the Heavy Metal Removal... Eko lo ji

size is 100 nm (Gleiter 1989, Mutschele andKircheim 1987).

In this paper we report the synthesis of copperand nickel ferrite nanoparticles (CuFe2O4 andNiFe2O4) by using the polyethylene glycol (PEG)assisted hydrothermal method and the removalstudies for zinc, copper, and nickel ions fromsynthetic wastewater with these spinel ferritenanoparticles. The experiments involvedsuspending pure samples of uniform-sized nickeland copper ferrite nanoparticles in water.

MATERIAL AND METHODSSynthesis of NanoparticlesThe synthesis of the nanoparticles was done by

using the PEG assisted hydrothermal method usedfor the synthesis of different ferrite nanoparticles(Gozuak et al. 2009, Koseoglu et al. 2011, Koseogluet al. 2012). All the reagents used in the experimentswere analytically pure and were purchased fromMerck Chemicals Company, and were used withoutfurther purification. To form a clear solution 0.725gNi(NO3)2•6H2O and 2.02g of Fe(NO3)3•9H2Owere each dissolved in 10 mL of distilled water andmixed with a magnetic stirrer. These mixtures ofNi(NO3)2•6H2O and Fe(NO3)3•9H2O weresuccessively dissolved. The reaction molar ratio ofNi and Fe has to be 1:2. After reaching the properratio, 20 mL of polyethylene glycol (PEG) wasadded to the solution and then the solution wasstirred again with a magnetic stirrer until thereactants were dissolved completely, approximately30 min. The aim of the PEG addition is to preventan increase in the size of the nanoparticles. The pHof the solution was adjusted to 11.0 by adding 0.2 MNaOH dropwise during stirring. After continuousstirring at 400 rpm for half an hour, a homogeneoussolution was obtained. Then the solution waspoured in to a Teflon lined stainless autoclave. Theautoclave was kept at 180°C in an oven for 24h andthen cooled to room temperature naturally. Theproducts were centrifuged and washed several timeswith de-ionized water, acetone, and absoluteethanol. Then the samples were put again in an ovenat 70°C to dry. After drying the solid phase sampleswere ground in a mortar to make them powder. Theobtained powders were used for all of themeasurements. The same procedure was followedfor the synthesis of CuFe2O4 nanoparticles bychanging nickel nitrate with copper nitrate.

Characterization of NanoparticlesThe X-ray powder diffraction analysis was

conducted with a Huber JSO-DEBYEFLEX 1001Diffractometer (XRD) using Cu Kα (operated at 40kV and 35 mA). The FT-IR transmission spectrawere taken with a Mattson Satellite InfraredSpectrometer from 4000 to 400 cm-1. The structuraland morphological characterizations of the sampleswere accomplished using a field emission scanningelectron microscopy (FE-SEM JEOL 7001 FE).The samples were coated with carbon prior to SEMmeasurements.

Heavy Metal Removal ExperimentsHere we report the synthesis of copper and

nickel ferrite (CuFe2O4 and NiFe2O4) nanoparticlesand the potential uses of these nanocomposites forCu(II), Ni(II), and Zn(II) removal from thesynthetic wastewater. For this purpose, we preparedthe synthetic waste water by dissolving salts ofNi(NO3)2•6H2O, Cu(NO3)2•3H2O, and N2O6Zn•6H2O in distilled water by using measuredamounts. An 0.1 g of nanoparticles were used andmixed with the wastewater which is a compositemetal mix consisting of Cu(II), Ni(II), and Zn(II)metal ions. The concentrations of Cu(II), Ni(II),and Zn(II) in the synthetic wastewater were 18.94,42.42, and 42.73 mg/L, respectively. The samples of25 ml of wastewater in 100 ml schliff-erlenmeyerswere prepared in two groups; 0.1 g of CuFe2O4 wasadded to the first group and 0.1 g of NiFe2O4 wasadded to the second group. The samples were mixedin a shaker (Gallenkamp orbital incubator, 25°C) at120 rpm for 24 hours and then filtered with an 0.5micron paper filter. The samples were thenacidulated with 0.2% nitric acid. The amounts ofCu(II), Ni(II), and Zn(II) were determined byatomic absorption spectrometry (AAS) with a VarianSpectra instrument model 220 spectrometer. Astandard solution containing the same matrix as thesamples was made up at the appropriateconcentrations for each element and used to draw acalibration curve in AAS.

The removal efficiencies and adsorptioncapacities of nanoparticles (CuFe2O4 and NiFe2O4)were calculated using equations 1 and 2.

(1)

(2)

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where E (%) is the removal efficiency, q (mg/g) isadsorption capacity, C0 (mg/L) and Ce (mg/L) arethe initial and equilibrated metal concentrations,respectively, V(L) is the volume of added solution,and m (g) is the mass of the adsorbent (dry).

The Apparatus UsedThe following materials and equipment were

used during the proposed validation study.Materials: Cu standard stock solution (1000 μg

Cu/L), Ni standard stock solution (1000 μg Ni/L),Zn standard stock solution (1000 μg Zn/mL), Nitricacid solution(65%), and distillated water.

Equipment: Varian Spectra instrument model220 Atomic absorption spectrometer, and a Gallen-kamp orbital incubator.

RESULTSStructural Characterization of Nanopar-

ticlesThe phase identification, of the as-prepared

NiFe2O4 and CuFe2O4 samples, was determined byX-ray diffraction (XRD). Figures 1 and 2 show theXRD patterns of the as prepared samples ofNiFe2O4 and CuFe2O4 and they indicate that bothsamples have a single spinel phase with a goodcrystallinity. By comparing XRD patterns of presentinvestigations with the standard data (JCPDS: 00-010-0325 for NiFe2O4 and JCPDS: 77-10 forCuFe2O4), it has been concluded that both samplescan be perfectly indexed to the cubic spinelstructure indicated in the reflecting planes (111),(220), (311), (222), (400), (422), (511), and (440) inthe patterns. Using Scherrer's equation: D=0.9 λ / βcos θ where D is the average crystalline size, λ is thewavelength of Cu Kα, β is the full width at halfmaximum (FWHM) of most intense diffractionpeak (311), and θ is the Bragg's angle, the averageparticle sizes are estimated to be around 25.6 nm forNiFe2O4 and 11.3 nm for CuFe2O4.

FT-IR SpectroscopyFigure 3 shows the representative IR spectra of

the as prepared ferrites of CuFe2O4 and NiFe2O4.The two main broad metal-oxygen bands areimportant in the IR spectra of all spinels, especiallyin ferrites. The highest IR band, V1, is generallyobserved in the higher frequency range of 600-550cm-1, corresponding to the intrinsic stretchingvibrations of the metal-oxygen bond at thetetrahedral site, Mtetra-O. The lowest IR band, V2, isusually observed in the frequency range of 450-385cm-1, assigned to stretching vibrations of the metal-

oxygen bond at the octahedral site, Mocta-O. As seenin the Figure 3, both the V1 and V2 stretchingvibrations were observed with the normal mode ofvibration of the tetrahedral cluster and is higher thanthat of the octahedral cluster. This can be attributedto the shortness of the tetrahedral bond and thelength of the octahedral bond. Since both Cu2+ andNi2+ ions preferentially occupy the octahedral sitesand Fe3+ ions can occupy both octahedral andtetrahedral sites, both of the V1 and V2 bandsobserved are the characteristics of the prepared Cuand Ni ferrites (Koseoglu et al. 2011, Marinca et al.2012). In the FT-IR spectra, V1 (540 cm-1) ) and V2

(427 cm-1) for CuFe2O4 shifted slightly to higherfrequencies as V1 (550 cm-1)) and V2 (460 cm-1)values by replacing the Cu2+ ion with an Ni2+ ion.Slight shifts of the V1 and V2 peak positions indicatethat changes due to the Ni2+ substitution has

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Fig 1. The XRD pattern for NiFe2O4 nanoparticles synthesized by the PEG assisted hydrothermal method.

Fig 2. The XRD pattern for CuFe2O4 nanoparticles synthesized by the PEG assisted hydrothermal method.

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slightly affected the metal-oxygen force constants inthe tetrahedral and octahedral sites. This can beexplained by the very small difference in both theatomic mass and ionic radii of the Cu and Ni ions(Faraz et al. 2012).

SEM MeasurementsFigure 4 shows the field emission scanning

electron micro-graphs (FE-SEM) of the CuFe2O4

and NiFe2O4 nanoparticles. The SEM images showthat the samples consist of spherical shapednanoparticles with small agglomeration. As seen inthe SEM pictures the nanoparticles have sizes ofmore than 100 nm and they are dense anddistributed regularly with-in the whole area (see Fig.4(a – b)). In addition to this, although these smallercrystallites are so closely arranged together, a clearboundary between neighboring particles can also beobserved. The larger particle sizes of thenanoparticles can be attributed to the PEG coatingwhich doesn’t count in crystallite sizes obtainedfrom XRD since PEG is amorphous.

Removal of Heavy MetalsThe graphs of the removal efficiencies of Cu(II),

Ni(II), and Zn(II) from synthetic wastewater are

shown in Fig. 5 for 0.1 g CuFe2O4 and Fig. 6 for 0.1g NiFe2O4.

The removal efficiencies of Cu(II), Ni(II), andZn(II) by using CuFe2O4 nanoparticles arecalculated as 83.50%, 98.85%, and 99.80%,respectively. It was found that the higher efficiencywas obtained for the removal of Zn(II) and thelower efficiency was obtained for the removal ofCu(II) as shown in Figure 5. The removalefficiencies of Cu(II), Ni(II), and Zn(II) by usingNiFe2O4 nanoparticles are calculated as 92.55%,36.56%, and 99.91%, respectively. It was found thatthe higher efficiency is again in the removal ofZn(II) and the lower efficiency is in the removal ofNi(II) as shown in Figure 6. As compared with theliterature, Ozmen et al. (2010) found 75.3% valuefor Cu(II) removal efficiency from an aqueousmedia with the modified Fe3O4 nanoparticles (pHof the solution 4, contact time 1 h, and the amountof adsorbent 1.25 g/L) and Mahdavi et al. (2012)found the removal efficiencies of Cd, Cu, Ni, andPb, in which Fe3O4, ZnO, and CuO nanoparticleswere used, between 9.2% and 81.5%.

It is also calculated as the adsorption capacities(q) of CuFe2O4 and NiFe2O4 nanoparticles forCu(II), Ni(II), and Zn(II). The adsorptioncapacities (q) are shown in Figures. 7 and 8 forCuFe2O4 and NiFe2O4, respectively. The amountsadsorbed by CuFe2O4 nanoparticles were calculatedas 3.95, 10.48, and 10.66 mg/g for Cu(II), Ni(II),and Zn(II), respectively. By using NiFe2O4

nanoparticles, the adsorption amounts were foundas 4.38, 3.88, and 10.67 mg/g for Cu(II), Ni(II), andZn(II), respectively. Zn(II) has the highest valuewhen examining the metal adsorption capacities ofCuFe2O4 and NiFe2O4 nanoparticles.

DISCUSSIONThe synthesis of copper and nickel ferrite

(CuFe2O4 and NiFe2O4) nanoparticles using thePEG assisted hydrothermal method and thepotential uses of these nanocomposites as adsorbentfor the removal of heavy metals from syntheticwastewater was investigated. The FT-IR and XRDspectra indicated that the samples have single phasespinel structure with sizes 25.6 nm for NiFe2O4 and11.3 nm for CuFe2O4. The SEM pictures show thatthe nanoparticles have spherical shapes with smallagglomeration.

It was seen that these spinel ferrites are veryefficient for the removal of heavy metals (zinc,

Fig 3. The FT-IR spectra of both adsorbents.

Fig 4. SEM pictures taken from (a) CuFe2O4 and (b) NiFe2O4 nanoparticles synthesized by PEG assisted hydrothermal method.

copper, and nickel) from synthetic wastewater byadsorption by magnetic nanoparticles and asubsequent simple magnetic separation process.

In this paper, the removal efficiencies of Cu(II),Ni(II), and Zn(II) by using CuFe2O4 nanoparticleswas calculated as 83.50 %, 98.85%, and 99.80%,respectively. It was found that the higher efficiencyis for the removal of Zn(II) and the lower efficiencyis for the removal of Cu(II). The removalefficiencies of Cu(II), Ni(II), and Zn(II) by usingNiFe2O4 nanoparticles were calculated as 92.55%,

36.56%, and 99.91%, respectively. It was found thatthe higher efficiency is again for the removal ofZn(II) and the lower efficiency is for the removal ofNi(II).

The results indicate that CuFe2O4 and NiFe2O4

nanoferrites synthesized by the PEG assistedhydrothermal method are useful for heavy metalremoval from wastewater and they have high heavymetal removal efficiencies.

ACKNOWLEDGEMENTSThis work was supported ny Scientific Research

Projects Coordination Unit of Istanbul University.Project number 28461

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Fig 5. The removal Efficiencies (%) of Cu(II), Ni(II), and Zn(II) by using 0.1 g CuFe2O4 nanoparticles.

Fig 6. The removal Efficiencies (%) of Cu(II), Ni(II), and Zn(II) by using NiFe2O4 nanoparticles.

Fig 7. The adsorption capacities (q) of 0.1 g CuFe2O4nanoparticles for Cu(II), Ni(II), and Zn(II)

Fig 8. The adsorption capacities (q) of 0.1 g NiFe2O4nanoparticles for Cu(II), Ni(II), and Zn(II)

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