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Particuology 7 (2009) 491–495

Contents lists available at ScienceDirect

Particuology

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ydrothermal synthesis of Mn–Zn ferrites from spent alkaline Zn–Mn batteries

u Xiao, Tao Zhou ∗, Jia Mengnstitute of Chemical & Chemical Engineering, Central South University, Changsha 410083, Hunan, China

r t i c l e i n f o

rticle history:eceived 10 February 2009eceived in revised form 31 March 2009

a b s t r a c t

Nanocrystalline Mn–Zn ferrites (Mn0.6Zn0.4Fe2O4) with particle size of 12 nm were synthesized hydrother-mally using spent alkaline Zn–Mn batteries, and accompanied by a study of the influencing factors.

ccepted 6 April 2009

eywords:pent alkaline batterieserritesydrothermal method

The nanocrystals were examined by powder X-ray diffraction (XRD) for crystalline phase identification,and scanning electron microscopy (SEM) for grain morphology. The relationship between concentra-tion of Fe(II), Mn(II), and Zn(II) and pH value was obtained through thermodynamic analysis of theFe(II)–Mn(II)–Zn(II)–NaOH–H2O system. The results showed that all ions were precipitated completelyat a pH value of 10–11. The optimal preparation conditions are: co-precipitation pH of 10.5, temperatureof 200 ◦C and time of 9 h.

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reparation © 2009 Chinese So

. Introduction

The Mn–Zn ferrites are ceramic materials employed exten-ively in transformers, magnetic recording heads, choke coils,oise filters, electromagnetic gadgets, information storage systems,edical diagnostics and biomedicine (Jordan et al., 1997; Rath et

l., 1999; Zheng, Zhong, Zhang, Yu, & Zeng, 2008), on account ofheir excellent properties such as high magnetic permeability, highaturation magnetization, high dielectric resistivity and relativelyower eddy current loss, as compared to alloy cores (Sugimoto,999). Modern science and technology call for higher performancend smaller size of Mn–Zn ferrites. Interest in soft magnetic mate-ials has therefore turned to their nanocrystallization and ionubstitution for improving their properties (Qureshi, 2006). Vari-us preparation techniques such as high-energy ball milling (Arcos,alenzuela, Vazquez, & Vallet-Regi, 1998; Zheng et al., 2008),o-precipitation (Arulmurugan, Vaidyanathan, Sendhilnathan, &eyadevan, 2006), sol–gel (Yue, Guo, Zhou, Gui, & Li, 2004),ydrothermal synthesis (Upadhyah et al., 2001), micro-emulsionechnique (Kosak, Makovec, Znidarsic, & Drofenik, 2004), andeverse micelle synthesis (Reddy, Satyanarayana, Sunkara, & Misra,004) have been used for preparing these particles. Hydrothermalrocessing consists of heterogeneous reaction in the presence of

queous solvents under high pressure and temperature to dissolvend re-crystallize materials that are relatively insoluble under ordi-ary conditions. Such processing can be used to give high producturity and homogeneity, crystal symmetry, metastable compounds

∗ Corresponding author. Tel.: +86 731 8876605.E-mail address: zhoutao@mail.csu.edu.cn (T. Zhou).

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674-2001/$ – see front matter © 2009 Chinese Society of Particuology and Institute of Process Eoi:10.1016/j.partic.2009.04.012

of Particuology and Institute of Process Engineering, Chinese Academy ofSciences. Published by Elsevier B.V. All rights reserved.

ith unique properties, narrow particle size distribution, usingimple equipment, low energy requirement, fast reaction, lowesidence time, especially for the growth of crystals with poly-orphic modifications or with low solubility (Byrappa & Adschiri,

007).Traditional recycle processing of spent batteries include tedious

yrometallurgical and hydrometallurgical methods, most of whichause serious pollution. Among the new green methods, Du andi (2005) recovered manganese from waste batteries using aioreduction process; Lin, Wang, & Li (2005) produced a liquidicro-element fertilizer using scrap alkaline zinc-manganese bat-

ery; as well as using the waste battery as building material (Wang,998). Spent Zn–Mn alkaline batteries are composed of ZnO, MnO,n2O3, Mn3O4, MnO2 within an Fe shell, as well as remnant Zn

fter battery discharging. Metallic ions are the main contents ofanganese zinc ferrites, hence recovering the metallic ion with

cid leaching of spent batteries as manganese zinc ferrites rawaterials, not only effectively converts spent batteries into sec-

ndary resource, but also reduces pollution caused by abandoninghe batteries.

As strong dependence exists between the Zn content and mag-etic moment, Mn1−xZnxFe2O4 is a kind of solid solution whoseagnetic moment changes with its Zn content. For Zn content

ower than 40%, magnetization increases with Zn content, that is,art of the Fe ions in the tetrahedral site is pushed to octahedral Bite by the zinc ion, thus increasing magnetization. However, when

he Zn content further increases beyond 40%, antiparallel Fea ionnd Feb ions can no longer prevail, and magnetization declines.herefore, for Zn content of 40%, Mn1−xZnxFe2O4 reaches the high-st magnetization (Arshak, Ajina, & Egan, 2001). This study aims atynthesizing nanocrystalline Mn1−xZnxFe2O4 (x = 0.4) hydrother-

ngineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

4 uology 7 (2009) 491–495

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92 L. Xiao et al. / Partic

ally by using spent batteries together with an investigation onhe factors which influence the preparing process.

. Experimental

.1. Sample preparation

The Mn–Zn ferrites are obtained through a multi-step processncluding acid leaching, co-precipitation and hydrothermal treat-

ent. First, spent Zn–Mn batteries (NANFU Battery Plant, China)sed as raw materials to prepare Mn–Zn ferrites were weighed,ismantled, milled, and then leached with water for 1 h, and thenissolved, with magnetic stirring, in a 150 mL 3 mol/L H2SO4 solu-ion containing 50 mL 2 wt% H2O2. After complete dissolution, thecid solution was filtered and the concentrations of Fe, Mn andn in the filtrate were determined by atomic absorption spec-roscopy. Stoichiometric amounts of MnSO4·H2O, FeSO4·7H2O andnO were added into the filtrate to assure the composition toeach Fe2O3:MnO:ZnO = 1:0.6:0.4. Then, NaOH solution was addedt selected speed and under constant stirring to adjust the pH torequired value. The slurry was subsequently transferred to an

utoclave having an automatic temperature controller to completehe hydrothermal treatment. The reaction temperature was con-rolled in the range of 110–200 ◦C, and the reaction might lastrom 3 to 12 h. The precipitates were washed several times withnhydrous ethanol and distilled water, and then dried at 105 ◦C forh.

.2. Sample characterization

The produced materials were examined by powder X-rayiffraction (XRD) (Siemens D-500) with Cu K� radiation (� = 1.5418) operating at 40 kV and 50 mA for crystalline phase identifica-

ion, and by scanning electron microscopy (SEM) (JEOL JSM-6360LVapan Electron Company) using an acceleration voltage of 20 kV forrain morphology. The SEM micrograph of the sample shown inig. 1, at 105 times magnification, displays the spheriform shapef the particles, as well as slight agglomeration of the very finearticles due to intrinsic ferrite magnetism. Fig. 2 shows XRD pat-

◦

ern of sample prepared at T = 200 C for t = 8 h, clearly exhibitinghat all the observed diffraction peaks and Miller indices (h k l)f this sample match well with the diffractions of the standardattern of manganese ferrite with no extra lines, indicating thathe sample has perfectly crystallized in the single-phase cubic-

Fig. 1. SEM micrograph of the sample.

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Fig. 2. XRD pattern of Mn0.4Zn0.6Fe2O4.

pinel structure, has no unreacted constituents, has no other phasesnd has no crystal deformation. The crystal size of the sampleas estimated from the broadening of the XRD peaks using the

cherrer equation (Huang, Li, & Lan, 1994): d = R�/ˇ cos �, whereis the grain diameter, ˇ is the half intensity width of the rel-

vant diffraction peak, � is the X-ray wave length and � is thengle of diffraction. The grain size estimated from the most intenseeaks (3 1 1) was approximately 12 nm and the lattice constant was.4151 nm.

. Results and discussion

.1. Main metal contents of spent battery

The solution obtained after acid leaching was examined bytomic absorption spectrophotometry (AAS), showing 25.76% Mnas MnO2), 23.38% Zn (as ZnO), and 13.41% Fe (as Fe2O3) in thepent alkaline batteries. The amount of the useful metals was up to2.55% of the total battery weight. To abandon these metals mayause serious environmental pollution and represent tremendousaste. Hence, spent batteries are treated as an important secondary

esource, and novel methods of utilizing spent batteries would beeaningful.

.2. Cation distribution

As is well-known, the spine1 structure can be viewed as a cubiclose-packed array of anions in which one-eighth of the tetrahe-ral and one-half of the octahedral sites are occupied by cations.he two extreme types in cation distribution are normal-spinelX)[Y]2O4 and inverse-spinel (Y)[XY]O4, where X and Y are dif-erent kinds of cations and the parentheses and brackets refer toations occupying the tetrahedral A sites and the octahedral B sites,espectively. It is assumed that Mn2+, Zn2+ and Fe3+ ions occupy thesites in the spinel structure, while Mn3+, Fe2+ and Fe3+ ions prefer

he B sites. Cation distribution varies with hydrothermal condition,specially temperature. (Zn2+Mn2+Fe3+Fe2+)[Fe3+Fe2+Mn3+]O4 isescribed for cation distribution of the Mn–Zn ferrite pre-ared. Regarding spine1 ferrite which has such structure asex1

1Mex22. . .Mexn

n[Mey11Mey2

2. . .Meynn]O4

2−, we can calcu-

ate the lattice constant a according to the Yunus et al. (2008)ormula:

= 8√

39

dA–O + 83

dB–O,

L. Xiao et al. / Particuology 7 (2009) 491–495 493

Table 1Possible cation distribution.

Distribution Lattice constant, a

Zn0.42+Fex

3+[Fe2−x2+Mn2x−2−y

2+Mn2−x3+Mny

4+]O42− (0 ≤ x ≤ 2, 0 ≤ y ≤ 2x − 2 ≤ 2) 0.5427 ≤ a ≤ 1.2854

Zn0.42+Fex

3+Mn0.6−x2+[Fe2−x

2+Mnx−y3+Mny

4+]O42− (0 ≤ y ≤ x ≤0.6) 0.8384 ≤ a ≤ 0.8784

Zn0.42+Fex

3+Mn0.6−x2+[Fe2−x

2+Mny2+Mnz

3+Mnx−y−z4+]O4

2− (0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.6, 0 ≤ z ≤ 0.6) 0.8384 ≤ a ≤ 0.9247

Zn0.42+Fex

3+Mn0.6−x2+[Fey

2+Fe2−x−y3+Mnx

3+]O42− (0 ≤ x ≤ 0.6, 0 ≤ y ≤ 2) 0.8336 ≤ a ≤ 0.8784

2+ 3+ 2+ 2+ 3+ 4+ 2− ≤ 2) 0.8174 ≤ a ≤ 0.8784

≤ 0.6, 0 ≤ y ≤2) 0.8377 ≤ a ≤ 0.8715

≤ 0.6, 0 ≤ y ≤ 2) 0.8174 ≤ a ≤ 0.9085

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Zn0.4 Fex Mn0.6−x [Fey Fe2−x−y Mnx ]O4 (0 ≤ x ≤ 0.6, 0 ≤ y

Zn0.42+Fex

3+Mn0.6−x2+[Fey

2+Fe2−y−z3+Mnz

2+Mnx−z3+]O4

2− (0 ≤ z ≤ x

Zn0.42+Fex

3+Mn0.6−x2+[Fey

2+Fe2−y−z3+Mnz

2+Mnx−z4+]O4

2− (0 ≤ z ≤ x

n which

A–O =n∑

i=1

xi(Mei–O)tetra and dB–O = 12

n∑i=1

yi(Mei–O)octa.

Regarding the different cation distributions we predicted, weave calculated the scope of the lattice constants as shown inable 1, though the accuracy may need further research in theuture.

According to the following Smith and Martell equation (1976),he cation distribution also depends on temperature:

x(1 + x)

(1 − x)2= exp

(− (1/N)(∂U/∂x)

kT

)= exp

(− E

kT

),

here activation energy E = (1/N)(∂U/∂x) expresses change of innernergy caused by Me2+ ion entering A site from B site and an Fe3+

on entering B site at the same time. The metallic ion distribu-ion parameter x is determined by the right hand side exponentialunction, that is, cation distribution is also closely related to tem-erature.

.3. Effect of pH value on precipitation

The pH value has significant influence on metallic ion precip-tation, thus calling for strict control during processing. Table 2hows the possible reactions in co-precipitation in accordance toheir equilibrium constants. The total concentrations of Zn(II), Fe(II)nd Mn(II) are expressed as [Zn]T, [Fe]T and [Mn]T, respectively and

alculated as follows:

Zn]T = [Zn2] + [Zn(OH)+][Zn(OH)2] + [Zn(OH)3−] + [Zn(OH)4

2−]

+ [Zn2(OH)3+],

able 2ossible reaction in co-precipitation system and corresponding equilibriumonstant.

No. Reaction log K

1 ML Zn2+ + OH− = Zn(OH)+ 5.02 ML2 Zn2+ + 2OH− = Zn(OH)2 11.13 ML3 Zn2+ + 3OH− = Zn(OH)3

− 13.64 ML4 Zn2+ + 4OH− = Zn(OH)4

2− 14.85 M2L 2Zn2+ + OH− = Zn2(OH)3+ 5.06 ML2(S,�1) Zn2+ + 2OH− = Zn(OH)2(S)(�1) 16.247 ML Fe2+ + OH− = Fe(OH)+ 4.58 ML2 Fe2+ + 2OH− = Fe(OH)2 7.49 ML3 Fe2+ + 3OH− = Fe(OH)3

− 10.010 ML4 Fe2+ + 4OH− = Fe(OH)4

2− 9.611 ML2(S) Fe2+ + 2OH− = Fe(OH)2(S) 15.112 ML Mn2+ + OH− = Mn(OH)+ 3.413 ML4 Mn2+ + 4OH− = Mn(OH)4

2− 7.714 M2L 2Mn2+ + OH− = Mn2(OH)3+ 3.415 M2L3 2Mn2+ + 3OH− = Mn2(OH)3

+ 18.116 ML2(S) Mn2+ + 2OH− = Mn(OH)2(S) 12.8

toe

Fig. 3. Relationship between log[Me]T and pH value.

Fe]T = [Fe2+] +[Fe(OH)+] +[Fe(OH)2] +[Fe(OH)3−] +[Fe(OH)4

2−],

Mn]T = [Mn2+] + [Mn(OH)+] + [Mn(OH)42−] + [Mn2(OH)3+]

+[Mn2(OH)3+].

Calculation according to Table 2, resulted in Fig. 3, which showshat [Zn]T, [Fe]T and [Mn]T have minimal values in the pH rangef 10–11, implying that controlling pH between 10 and 11 maynsure their complete co-precipitation. Fe2+, Mn2+ will be oxi-

Fig. 4. XRD patterns of samples synthesized at different temperatures.

494 L. Xiao et al. / Particuology

Fig. 5. XRD patterns of samples synthesized at different time.

Fig. 6. SEM micrographs of the samples without (a) and with (b) additives.

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7 (2009) 491–495

ized inevitably since the closed system includes oxygen and theydrothermal treatment is a high-temperature and high-pressurerocess. This process will influence the system pH value. Therefore,ushion solution should be added in the hydrothermal process toeep the pH value to be 10–11.

.4. Effect of reaction temperature

From the above discussion, a pH value of 10.5 was chosen as ourxperimental condition. The reaction temperature was chosen toary from 110 to 200 ◦C and the reaction time was set to be 6 h.s shown by the XRD patterns in Fig. 4, the relative broad shapef the diffraction peaks reflects the formation of the disorderedtructure at 110 ◦C. The peak intensity is quite weak, and moreover,here is no peak corresponding to the positions of (2 2 0) and (4 0 0).owever, for temperatures higher than 140 ◦C, the intensity of the

pinel peaks increases remarkably with increasing hydrothermalemperature.

.5. Effect of reaction time

In order to estimate the effect of reaction time, a series ofxperiments corresponding to different times (3, 6, 9, 12 h) wereonducted at 160 ◦C. As shown in Fig. 5, at 3 h, there is no obvi-us prominent peak to reflect the formation of any disorderedtructure. But the intensity of the major spinel peak increases aseaction time increases. For time longer than 9 h, the product XRDiffraction peak intensity has increased considerably. Therefore, inonsideration of technology, economy and energy consumption,ydrothermal processing time of t = 9 h was chosen.

.6. Effect of additives

Acetic acid contributes to co-precipitation through homoge-eous mixing of the various elements on an atomic or molecularcale as a co-precipitation precursor in reducing crystal surfacenergy and weakening or even eliminating agglomeration betweenanoparticles, thus leading to even dispersion of Mn–Zn ferriteanoparticles. Fig. 6 shows how organic acid additives improvedhe co-precipitation process and reduced the size of the synthesizedarticles.

. Conclusions

Spent battery is used as raw materials to prepare 12-nmanocrystalline Mn–Zn ferrite (Mn0.6Zn0.4Fe2O4) particles via aulti-step process consisting of acid leaching, co-precipitation and

ydrothermal processing.A relationship between Fe(II), Mn(II), Zn(II) concentration and

he pH value was obtained through thermodynamic analysis of thee(II)–Mn(II)–Zn(II)–NaOH–H2O system, to show that all ions coulde precipitated completely at pH value of 10–11.

Experiments showed that longer reaction time and higher pro-essing temperature might contribute to better crystallization ofhe ferrite particles. The recommended optimal conditions are:00 ◦C and 9 h.

Co-precipitation precursors, such as some organic acid addi-ives, could provide the precondition of preparing pure Mn–Znerrite nanoparticles, through improving the hydrothermal co-recipitation process for better crystallite formation.

eferences

rcos, D., Valenzuela, R., Vazquez, M., & Vallet-Regi, M. (1998). Chemical homo-geneity of nanocrystalline Zn–Mn spinel ferrites obtained by high-energy ballmilling. Journal of Solid State Chemistry, 141, 10–16.

uology

A

A

B

D

H

J

K

L

Q

R

R

S

S

U

W

Y

Y

nary spinel system MgxCo1−xCrxFe2−xO4. Journal of Alloys and Compounds, 454,10–15.

L. Xiao et al. / Partic

rulmurugan, R., Vaidyanathan, G., Sendhilnathan, S., & Jeyadevan, B. (2006). Mn–Znferrite nanoparticles for ferrofluid preparation: Study on thermal–magneticproperties. Journal of Magnetism and Magnetic Materials, 298, 83–94.

rshak, K. I., Ajina, A., & Egan, D. (2001). Development of screen-printed polymerthick film planner transformer using Mn–Zn ferrite as core material. Microelec-tronics Journal, 32(2), 113–116.

yrappa, K., & Adschiri, T. (2007). Hydrothermal technology for nanotechnology.Progress in Crystal Growth and Characterization of Materials, 53, 117–166.

u, Z., & Li, H. (2005). Recovery of manganese from waste batteries using microbeand organic waste through bioreduction process. Techniques and Equipment forEnvironmental Pollution Control, 6(9), 62–64 (in Chinese).

uang, Y., Li, S., & Lan, Z. (1994). Magnetic materials. Beijing: Publishing House ofElectronic Industry. (in Chinese).

ordan, A., Scholz, R., Wust, P., Fähling, H., Krause, J., Wlodarczyk, W., et al. (1997).Effects of magnetic fluid hyperthermia (MFH) on C3H mammary carcinoma invivo. International Journal of Hyperthermia, 13(6), 587–605.

osak, A., Makovec, D., Znidarsic, A., & Drofenik, M. (2004). Preparation of MnZn-ferrite with microemulsion technique. Journal of the European Ceramic Society,24, 959–962.

in, H., Wang, D., & Li, H. (2005). Production of liquid micro-element fertilizer usingscrap alkaline zinc–manganese battery and its effect on corn. Journal of Agro-

environmental Science, 24(4), 825–828 (in Chinese).

ureshi, A. H. (2006). The influence of hafnia and impurities (CaO/SiO2) on themicrostructure and magnetic properties of Mn–Zn ferrites. Journal of CrystalGrowth, 286, 365–370.

eddy, K. M., Satyanarayana, L., Sunkara, V., & Misra, R. D. K. (2004). A comparativestudy of the gas sensing behavior of nanostructured nickel ferrite synthesized

Z

7 (2009) 491–495 495

by hydrothermal and reverse micelle techniques. Materials Research Bulletin,39(10), 1491–1498.

ath, C., Sahu, K. K., Anand, S., Date, S. K., Mishra, N. C., & Das, R. P. (1999). Prepara-tion and characterization of nanosize Mn–Zn ferrite. Journal of Magnetism andMagnetic Materials, 202, 77–84.

mith, R., & Martell, A. E. (1976). Critical stability constants. Inorganic complexes NewYork: Plenum Press.

ugimoto, M. (1999). The past, present and future of ferrites. Journal of the AmericanCeramic Society, 82(2), 269–280.

padhyah, C., Verma, H. C., Rath, C., Sahub, K. K., Anand, S., Das, R. P., et al. (2001).Mössbauer studies of nanosize Mn1−xZnxFe2O4. Journal of Alloys and Compounds,326, 94–97.

ang, J. W. (1998). Comprehensive utilization of waste battery. CN Patent No.1194252.

ue, Z., Guo, W., Zhou, J., Gui, Z., & Li, L. (2004). Synthesis of nanocrystalline ferritesby sol–gel combustion process: The influence of pH value of solution. Journal ofMagnetism and Magnetic Materials, 270, 216–223.

unus, S. M., Yamauchi, H., Zakaria, A. K. M., Igawa, N., Hoshikawa, A., & Ishii, Y.(2008). Cation distribution and crystallographic characterization of the quater-

heng, Z. G., Zhong, X. C., Zhang, Y. H., Yu, H. Y., & Zeng, D. C. (2008). Synthe-sis, structure and magnetic properties of nanocrystalline ZnxMn1−xFe2O4

prepared by ball milling. Journal of Alloys and Compounds, 466,377–382.