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Study on preparation of manganese–zinc ferrites using spent Zn–Mn batteries
Materials Letters 58 (2004) 1164 – 1167 www.elsevier.com/locate/matlet
Study on preparation of manganese–zinc ferrites using spent Zn–Mn batteries Guoxi Xi *, Yunqing Li, YuMin Liu Department of Chemistry Henan Normal University, Xinxiang, Henan 453002, PR China Received 13 June 2003; accepted 27 August 2003
Abstract Studies on preparing manganese – zinc ferrites by coprecipitation method using spent Zn – Mn batteries have been carried out to determine the influential factors on preparing process, including coprecipitation pH value, coprecipitation temperature and calcining temperature, etc. Results show that the suitable preparing conditions are: coprecipitation pH value, 7 – 7.5; copecipitation temperature, 50 jC and calcining temperature, 1100 – 1150 jC. It also finds that Fe powder is the suitable material to remove Hg existing in spent Zn – Mn batteries completely. D 2003 Elsevier B.V. All rights reserved. Keywords: Zn – Mn batteries; Mn – Zn ferrite; Preparation; Coprecipitation
1. Introduction In recent years, numerous studies have been done on recycling spent Zn –Mn batteries, which can be summarized into two categories: pyrometallurgy and hydrometallurgy. The disadvantages with pyrometallurgy are high cost, much energy and complicated operation, etc.; and those with hydrometallurgy have low purity and low added value of recycling products and easily leading to secondary pollution and so on [1– 8]. The purpose of this work is to find a way to recover used Zn – Mn batteries by combining the advantages with pyrometallurgy and hydrometallurgy. The target product is not a single metal or its oxide but Mn – Zn ferrites with high added value. Mn – Zn ferrites have a cubic structure and belong to an important class of soft magnetic materials, which are widely used in many electronic and magnetic applications, such as in transformers, noise filters, and recording heads, due to their high magnetic permeabilities and low magnetic losses [9– 12]. Analytic results show that spent Zn – Mn batteries have adequate amounts of manganese and zinc and inadequate amount of iron to prepare high-performance Mn – Zn ferrites, which have the composition of 50– 55 mol% Fe2O3, 20– 30 mol% MnO and 15– 30 mol% ZnO [13,14]. Furthermore, Hg is included in spent
* Corresponding author. 0167-577X/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2003.08.029
Zn – Mn batteries, which is toxic. Therefore, the present paper is focused not only on preparing high-performance Mn – Zn ferrites but also on removing Hg existing in spent Zn – Mn batteries completely.
2. Experimental procedure The spent Zn – Mn batteries (Xinxiang Battery Plant, China) used as source materials to prepare Mn – Zn ferrites were first dissolved in 3 mol/l H2SO4 solution containing 2.4 wt.% H2O2. After complete dissolution of spent Zn – Mn batteries, the acid solution was filtered and the filtrate was kept at the boiling point for 1 h to remove the residual H2O2 existing in the filtrate. NaOH solution was added dropwise during stirring of the filtrate to adjust the pH value in the range of 3 – 5. Then, the filtrate was analyzed for the concentrations of Fe, Mn and Zn by atomic absorption spectroscopy (Model Z-5000, HITACHI, Japan). Stoichiometric amounts of the appropriate MnSO4H2O and Fe powder were added to the filtrate aimed to have M2 + (total metal ion) = 1.2 mol/l with the composition of Fe2O3/MnO/ ZnO = 1:0.6:0.4 (in mole). After filtration treatment, Hg existing in spent Zn – Mn batteries could be reduced by Fe powder and reclaimed. The secondary filtrate was analyzed for the concentration of Hg by mercury detector (Model, YYG-3S, The Second Instruments Plant of Xian, China). Subsequently, the precipitants composed of NH3H2O and
G. Xi et al. / Materials Letters 58 (2004) 1164–1167 Table 1 The effect of demercuration by iron powder and iron salts
Table 3 Metal ion concentrations in the filtrate at different temperature after coprecipitation treatment (Conditions: pH = 7.5, Initial Mn2 + = 6593 ppm, Zn2 + = 5231 ppm)
The residual Hg in the filtrate Fe powder FeCl25H2O FeCl36H2O
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below detectability (0.2 ppb) 3.2 mg/l 3.1 mg/l
NH4HCO3 were added during stirring of the secondary filtrate until the desired pH value was obtained. The pH value was varied from 6.0 to 9.5 and the [NH4HCO3]/ [M2 +] = 1.2. After precipitation treatment for 1 h at the desired temperature varied from 25 to 60 jC, the precipitates were filtered, washed, dried and calcined in air. The residue obtained after filtration under various coprecipitation conditions was analyzed for the concentrations of Fe, Mn and Zn by atomic absorption spectroscopy. Individual grains of the resulting product, Manganese – Zinc ferrites, were inspected and analyzed using transmission electron microscopy [Model JEM-100SX, JEOL, Japan] and scanning electron microscopy [Model AMRAY-1000B, AMRAY, US]. The ferrites of solids were identified from XRD (Model BRUKER.axs, BRUKER, Germany) patterns and the spinel ratio (spinel%) is defined by the following equation: IðspinelÞ spinel% ¼ ; IðspinelÞ þ IðFe2 O3 Þ where I is the intensity of the strongest peak for each compound [9].
3. Results and discussion
25 jC 30 jC 35 jC 40 jC 45 jC 50 jC 55 jC 60 jC Mn (ppm) 7.3 Zn (ppm) 4.7
3.8 6.0
3.2 7.0
2.5 10.2
2.0 14.0
1.8 16.0
1.3 23.0
1.3 32.0
3.2. The effect of coprecipitation pH value Table 2 shows metal ion concentrations in the filtrate at different pH value after co-precipitation treatment. It is observed that metal ion concentrations in the filtrate decrease with the increase in pH value when pH value is between 6.0 and 7.0; at high pH value ([7.5), the concentrations of Zn and Mn in the filtrate increase with the increase in pH value while Fe ion is completely precipitated at these pH values (not shown in Table 2). This can be explained as follows. At lower pH value (pH = 6.0– 7.0), the major precipitates in the solution are the carbonates of iron, manganese and zinc. The following reaction occurs: 2 NH4 HCO3 þ OH ¼ NHþ 4 þ CO3 þ H2 O
ð1Þ
2þ ¼ MCO3 # ðM ¼ Fe; Mn; ZnÞ CO2 3 þM
ð2Þ
With the increase in pH, the concentration of CO32 increases, which is advantageous for the precipitation of metal ion. However, at higher pH value (pH>7.5), the precipitated Mn and Zn hydroxides may form a complex with ammonium salts and dissolve .The reaction is as follows: 2þ Mn=ZnðOHÞ2 þ 4NHþ 4 þ 2OH ¼ Mn=ZnðNH3 Þ4
3.1. The effect of demercuration by Fe powder and iron salts Fe powder, FeCl25H2O and FeCl36H2O are used to supplement the inadequate amount of iron existing in spent Zn – Mn batteries, respectively. The residual concentration of Hg in the filtrate is shown in Table 1. Obviously, Fe powder is the suitable material to supplement the inadequate amount of iron on the process of preparing Mn – Zn ferrites, which can remove Hg existing in spent Zn– Mn batteries less than 0.2 ppb.
þ 4H2 O
ð3Þ
To obtain precise metal ion stoichiometry, it is necessary to achieve precipitation yield a>0.995 when the
Table 2 Metal ion concentrations in the filtrate at different pH value after coprecipitation treatment (Conditions: T = 25 jC, Initial Mn2 + = 6593 ppm, Zn2 + = 5231 ppm)
Mn (ppm) Zn (ppm) Fe (ppm)
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
1800 320 6000
650 33.5 2725
6.0 13 0.7
1.8 16
2.9 70
4.1 420
5.2 800
6.1 2350 Fig. 1. XRD patterns of powder calcinated at different temperature for 2 h.
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G. Xi et al. / Materials Letters 58 (2004) 1164–1167
Table 4 The spinel ratio at different calcining temperature Calcining temperature (jC) Spinel ratio %
1000 70.5
1050 74.2
1080 82.4
1100
1130
1150
100
100
100
metal ions are precipitated [15]. The precipitation yield is defined as a¼
Ci Cf ; Ci
where Ci is the initial concentration of individual metal ion, and Cf is the concentration of individual metal ion in the filtrate. Thus, pH value between 7.0 and 7.5 was found to be the ideal pH value to maintain the initial stoichiometry (Mn0.6Zn0.4Fe2O4) in the precipitates. 3.3. The effect of coprecipitation temperature Table 3 shows that the coprecipitation temperature has different influence on the precipitates of Mn and Zn (Fe ion is completely precipitated and not shown in Table 3). With the increase in temperature, the concentration of Mn2 + in the filtrate decreases, and the concentration of Zn2 + in the filtrate increases. But at high temperature, aqueous ammonium is easy to evaporate and it is hard to control the pH value; at low temperature (below 40 jC), penetration phenomenon occurs when the precipitates are filtered, which indicates that low temperature is disadvantageous for the growth of precipitated particles. Therefore, the suitable temperature for coprecipitation is around 50 jC.
Fig. 3. SEM photograph of powder calcined at 1130 jC for 2 h.
phase and a-Fe2O3 peaks for X = 1000 – 1080, but only spinel phase peaks for X = 1100 – 1150. This can be explained as follows. In low temperature(1000 –1080 jC), the consolidation reaction of Fe2O3, MnO and ZnO forming Mn – Zn ferrites is incomplete and it would have free Fe2O3 existing in powders without consolidation with MnO and ZnO. Therefore, XRD patterns show spinel phase and a-Fe2O3 peaks for powders calcined at 1000– 1080 jC. With the increase in temperature (1100 – 1150 jC), the consolidation reaction is gradually complete and the amount of free a-Fe2O3 gradually decreases. Therefore, XRD patterns show only spinel phase for powders calcined at 1100– 1150 jC. It is also observed in Table 4 that the spinel ratio increases with increasing calcining temperature, which is consistent with the decreasing amount of free a-Fe2O3. The mean crystallite size of the sample calcined at 1130 jC for 2 h has been estimated from XRD linewidth of the(311) peak using the Scherrer equation:
3.4. The effect of calcining temperature The precipitates, conducted at pH value 7.5, temperature 50 jC, are used to study the effect of calcining temperature. Calcined powders are denoted as CX, where X = 1000 f 1150 standing for calcining temperature (jC). XRD patterns of calcined powders (Fig. 1) show spinel
d¼
0:9k ðBM BS Þcosh
where d is the mean crystallite size, BM and BS are the half width of the relevant diffraction peak and the instrumental broadening, respectively. k is the X-ray wave length and h, the angle of diffraction. The mean crystallite size estimated from the (311) peak was approximately 22.4 nm. TEM micrograph of the sample (C1130) is shown in Fig. 2 and the maximum crystallite size was estimated to be about 30 nm. SEM photograph of the sample (C1130) is shown in Fig. 3, the particle size estimated from the photograph is below 30 Am with almost spherical shape.
4. Conclusion
Fig. 2. TEM micrograph of powder calcined at 1130 jC for 2 h.
1. Fe powder is the suitable material to supplement insufficient amount of Fe on the process of preparing Mn – Zn ferrites using spent Zn – Mn batteries, which can remove Hg existing in spent Zn – Mn batteries completely.
G. Xi et al. / Materials Letters 58 (2004) 1164–1167
2. The suitable preparing conditions are: coprecipitation pH value, 7.0 –7.5; coprecipitation temperature, 50 jC and calcining temperature, 1100 –1150 jC. Under the above mentioned preparing conditions, it can maintain precise metal ion stoichiometry (Mn0.6Zn0.4Fe2O4) and resulting powders show only spinel phase peaks in XRD patterns. 3. The maximum crystallite size of the Mn – Zn ferrites calcined at 1130 jC for 2 h is below 30 nm, and the mean crystallite size is 22.4 nm. Acknowledgements The authors are grateful to Prof. Dingxi Cheng for the measurement of the concentration of metal ion. References [1] M.A. Rabah, M.A. Barakat, Y.Sh. Mahrous, JOM 12 (1999) 41. [2] H. Abbas, M.A. Askar, E.M. Abd-Elaziz, J. Egypt. Chem. 42 (4) (1999) 361.
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[3] P. Giuseppe, B. Adriano, M. Antonio, J. Environ. Chem. Technol. 1 (1995) 16. [4] I. Takamasa, M. Minoru, K. Takashi, JP: 11191439, 1999. [5] K. Tatsuyuki, K. Yoshimass, S. Hidetoshi, JP: 05247554, 1993. [6] K. Takashi, I. Takamasa, S. Toshio, S. Shigeadi, K. Takeo, JP: 0781941, 1995. [7] G. Xi, Y. Li, Chem. World 11 (2001) 563. [8] G. Xi, Y. Li, Chem. Res. Appl. 6 (2001) 706. [9] W.-H. Lin, S.-K. Jang Jean, C.-S. Hwang, J. Mater. Res. 14 (1) (1999) 205. [10] K. Mandal, S. Pan Mandal, P. Agudo, M. Pal, Appl. Surf. Sci. 182 (2001) 386. [11] B. Li, G. Yin, Z. Zha, C. Zheng, J. Han, Nonferr. Metals 51 (3) (1999) 87. [12] C. Rath, K.K. Sahu, S. Anand, S.K. Date, N.C. Mishra, R.P. Das, J. Magn. Magn. Mater. 202 (1999) 77. [13] N. Shinji, JP: 09156929, 1997. [14] N. Shinji, JP: 05198418, 1993. [15] M. Bremer, St. Fischer, H. Langbein, W. Topelmann, H. Scheler, Thermochim. Acta 209 (1992) 325.
Study on preparation of manganese–zinc ferrites using spent Zn–Mn batteries Guoxi Xi *, Yunqing Li, YuMin Liu Department of Chemistry Henan Normal University, Xinxiang, Henan 453002, PR China Received 13 June 2003; accepted 27 August 2003
Abstract Studies on preparing manganese – zinc ferrites by coprecipitation method using spent Zn – Mn batteries have been carried out to determine the influential factors on preparing process, including coprecipitation pH value, coprecipitation temperature and calcining temperature, etc. Results show that the suitable preparing conditions are: coprecipitation pH value, 7 – 7.5; copecipitation temperature, 50 jC and calcining temperature, 1100 – 1150 jC. It also finds that Fe powder is the suitable material to remove Hg existing in spent Zn – Mn batteries completely. D 2003 Elsevier B.V. All rights reserved. Keywords: Zn – Mn batteries; Mn – Zn ferrite; Preparation; Coprecipitation
1. Introduction In recent years, numerous studies have been done on recycling spent Zn –Mn batteries, which can be summarized into two categories: pyrometallurgy and hydrometallurgy. The disadvantages with pyrometallurgy are high cost, much energy and complicated operation, etc.; and those with hydrometallurgy have low purity and low added value of recycling products and easily leading to secondary pollution and so on [1– 8]. The purpose of this work is to find a way to recover used Zn – Mn batteries by combining the advantages with pyrometallurgy and hydrometallurgy. The target product is not a single metal or its oxide but Mn – Zn ferrites with high added value. Mn – Zn ferrites have a cubic structure and belong to an important class of soft magnetic materials, which are widely used in many electronic and magnetic applications, such as in transformers, noise filters, and recording heads, due to their high magnetic permeabilities and low magnetic losses [9– 12]. Analytic results show that spent Zn – Mn batteries have adequate amounts of manganese and zinc and inadequate amount of iron to prepare high-performance Mn – Zn ferrites, which have the composition of 50– 55 mol% Fe2O3, 20– 30 mol% MnO and 15– 30 mol% ZnO [13,14]. Furthermore, Hg is included in spent
* Corresponding author. 0167-577X/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2003.08.029
Zn – Mn batteries, which is toxic. Therefore, the present paper is focused not only on preparing high-performance Mn – Zn ferrites but also on removing Hg existing in spent Zn – Mn batteries completely.
2. Experimental procedure The spent Zn – Mn batteries (Xinxiang Battery Plant, China) used as source materials to prepare Mn – Zn ferrites were first dissolved in 3 mol/l H2SO4 solution containing 2.4 wt.% H2O2. After complete dissolution of spent Zn – Mn batteries, the acid solution was filtered and the filtrate was kept at the boiling point for 1 h to remove the residual H2O2 existing in the filtrate. NaOH solution was added dropwise during stirring of the filtrate to adjust the pH value in the range of 3 – 5. Then, the filtrate was analyzed for the concentrations of Fe, Mn and Zn by atomic absorption spectroscopy (Model Z-5000, HITACHI, Japan). Stoichiometric amounts of the appropriate MnSO4H2O and Fe powder were added to the filtrate aimed to have M2 + (total metal ion) = 1.2 mol/l with the composition of Fe2O3/MnO/ ZnO = 1:0.6:0.4 (in mole). After filtration treatment, Hg existing in spent Zn – Mn batteries could be reduced by Fe powder and reclaimed. The secondary filtrate was analyzed for the concentration of Hg by mercury detector (Model, YYG-3S, The Second Instruments Plant of Xian, China). Subsequently, the precipitants composed of NH3H2O and
G. Xi et al. / Materials Letters 58 (2004) 1164–1167 Table 1 The effect of demercuration by iron powder and iron salts
Table 3 Metal ion concentrations in the filtrate at different temperature after coprecipitation treatment (Conditions: pH = 7.5, Initial Mn2 + = 6593 ppm, Zn2 + = 5231 ppm)
The residual Hg in the filtrate Fe powder FeCl25H2O FeCl36H2O
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below detectability (0.2 ppb) 3.2 mg/l 3.1 mg/l
NH4HCO3 were added during stirring of the secondary filtrate until the desired pH value was obtained. The pH value was varied from 6.0 to 9.5 and the [NH4HCO3]/ [M2 +] = 1.2. After precipitation treatment for 1 h at the desired temperature varied from 25 to 60 jC, the precipitates were filtered, washed, dried and calcined in air. The residue obtained after filtration under various coprecipitation conditions was analyzed for the concentrations of Fe, Mn and Zn by atomic absorption spectroscopy. Individual grains of the resulting product, Manganese – Zinc ferrites, were inspected and analyzed using transmission electron microscopy [Model JEM-100SX, JEOL, Japan] and scanning electron microscopy [Model AMRAY-1000B, AMRAY, US]. The ferrites of solids were identified from XRD (Model BRUKER.axs, BRUKER, Germany) patterns and the spinel ratio (spinel%) is defined by the following equation: IðspinelÞ spinel% ¼ ; IðspinelÞ þ IðFe2 O3 Þ where I is the intensity of the strongest peak for each compound [9].
3. Results and discussion
25 jC 30 jC 35 jC 40 jC 45 jC 50 jC 55 jC 60 jC Mn (ppm) 7.3 Zn (ppm) 4.7
3.8 6.0
3.2 7.0
2.5 10.2
2.0 14.0
1.8 16.0
1.3 23.0
1.3 32.0
3.2. The effect of coprecipitation pH value Table 2 shows metal ion concentrations in the filtrate at different pH value after co-precipitation treatment. It is observed that metal ion concentrations in the filtrate decrease with the increase in pH value when pH value is between 6.0 and 7.0; at high pH value ([7.5), the concentrations of Zn and Mn in the filtrate increase with the increase in pH value while Fe ion is completely precipitated at these pH values (not shown in Table 2). This can be explained as follows. At lower pH value (pH = 6.0– 7.0), the major precipitates in the solution are the carbonates of iron, manganese and zinc. The following reaction occurs: 2 NH4 HCO3 þ OH ¼ NHþ 4 þ CO3 þ H2 O
ð1Þ
2þ ¼ MCO3 # ðM ¼ Fe; Mn; ZnÞ CO2 3 þM
ð2Þ
With the increase in pH, the concentration of CO32 increases, which is advantageous for the precipitation of metal ion. However, at higher pH value (pH>7.5), the precipitated Mn and Zn hydroxides may form a complex with ammonium salts and dissolve .The reaction is as follows: 2þ Mn=ZnðOHÞ2 þ 4NHþ 4 þ 2OH ¼ Mn=ZnðNH3 Þ4
3.1. The effect of demercuration by Fe powder and iron salts Fe powder, FeCl25H2O and FeCl36H2O are used to supplement the inadequate amount of iron existing in spent Zn – Mn batteries, respectively. The residual concentration of Hg in the filtrate is shown in Table 1. Obviously, Fe powder is the suitable material to supplement the inadequate amount of iron on the process of preparing Mn – Zn ferrites, which can remove Hg existing in spent Zn– Mn batteries less than 0.2 ppb.
þ 4H2 O
ð3Þ
To obtain precise metal ion stoichiometry, it is necessary to achieve precipitation yield a>0.995 when the
Table 2 Metal ion concentrations in the filtrate at different pH value after coprecipitation treatment (Conditions: T = 25 jC, Initial Mn2 + = 6593 ppm, Zn2 + = 5231 ppm)
Mn (ppm) Zn (ppm) Fe (ppm)
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
1800 320 6000
650 33.5 2725
6.0 13 0.7
1.8 16
2.9 70
4.1 420
5.2 800
6.1 2350 Fig. 1. XRD patterns of powder calcinated at different temperature for 2 h.
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G. Xi et al. / Materials Letters 58 (2004) 1164–1167
Table 4 The spinel ratio at different calcining temperature Calcining temperature (jC) Spinel ratio %
1000 70.5
1050 74.2
1080 82.4
1100
1130
1150
100
100
100
metal ions are precipitated [15]. The precipitation yield is defined as a¼
Ci Cf ; Ci
where Ci is the initial concentration of individual metal ion, and Cf is the concentration of individual metal ion in the filtrate. Thus, pH value between 7.0 and 7.5 was found to be the ideal pH value to maintain the initial stoichiometry (Mn0.6Zn0.4Fe2O4) in the precipitates. 3.3. The effect of coprecipitation temperature Table 3 shows that the coprecipitation temperature has different influence on the precipitates of Mn and Zn (Fe ion is completely precipitated and not shown in Table 3). With the increase in temperature, the concentration of Mn2 + in the filtrate decreases, and the concentration of Zn2 + in the filtrate increases. But at high temperature, aqueous ammonium is easy to evaporate and it is hard to control the pH value; at low temperature (below 40 jC), penetration phenomenon occurs when the precipitates are filtered, which indicates that low temperature is disadvantageous for the growth of precipitated particles. Therefore, the suitable temperature for coprecipitation is around 50 jC.
Fig. 3. SEM photograph of powder calcined at 1130 jC for 2 h.
phase and a-Fe2O3 peaks for X = 1000 – 1080, but only spinel phase peaks for X = 1100 – 1150. This can be explained as follows. In low temperature(1000 –1080 jC), the consolidation reaction of Fe2O3, MnO and ZnO forming Mn – Zn ferrites is incomplete and it would have free Fe2O3 existing in powders without consolidation with MnO and ZnO. Therefore, XRD patterns show spinel phase and a-Fe2O3 peaks for powders calcined at 1000– 1080 jC. With the increase in temperature (1100 – 1150 jC), the consolidation reaction is gradually complete and the amount of free a-Fe2O3 gradually decreases. Therefore, XRD patterns show only spinel phase for powders calcined at 1100– 1150 jC. It is also observed in Table 4 that the spinel ratio increases with increasing calcining temperature, which is consistent with the decreasing amount of free a-Fe2O3. The mean crystallite size of the sample calcined at 1130 jC for 2 h has been estimated from XRD linewidth of the(311) peak using the Scherrer equation:
3.4. The effect of calcining temperature The precipitates, conducted at pH value 7.5, temperature 50 jC, are used to study the effect of calcining temperature. Calcined powders are denoted as CX, where X = 1000 f 1150 standing for calcining temperature (jC). XRD patterns of calcined powders (Fig. 1) show spinel
d¼
0:9k ðBM BS Þcosh
where d is the mean crystallite size, BM and BS are the half width of the relevant diffraction peak and the instrumental broadening, respectively. k is the X-ray wave length and h, the angle of diffraction. The mean crystallite size estimated from the (311) peak was approximately 22.4 nm. TEM micrograph of the sample (C1130) is shown in Fig. 2 and the maximum crystallite size was estimated to be about 30 nm. SEM photograph of the sample (C1130) is shown in Fig. 3, the particle size estimated from the photograph is below 30 Am with almost spherical shape.
4. Conclusion
Fig. 2. TEM micrograph of powder calcined at 1130 jC for 2 h.
1. Fe powder is the suitable material to supplement insufficient amount of Fe on the process of preparing Mn – Zn ferrites using spent Zn – Mn batteries, which can remove Hg existing in spent Zn – Mn batteries completely.
G. Xi et al. / Materials Letters 58 (2004) 1164–1167
2. The suitable preparing conditions are: coprecipitation pH value, 7.0 –7.5; coprecipitation temperature, 50 jC and calcining temperature, 1100 –1150 jC. Under the above mentioned preparing conditions, it can maintain precise metal ion stoichiometry (Mn0.6Zn0.4Fe2O4) and resulting powders show only spinel phase peaks in XRD patterns. 3. The maximum crystallite size of the Mn – Zn ferrites calcined at 1130 jC for 2 h is below 30 nm, and the mean crystallite size is 22.4 nm. Acknowledgements The authors are grateful to Prof. Dingxi Cheng for the measurement of the concentration of metal ion. References [1] M.A. Rabah, M.A. Barakat, Y.Sh. Mahrous, JOM 12 (1999) 41. [2] H. Abbas, M.A. Askar, E.M. Abd-Elaziz, J. Egypt. Chem. 42 (4) (1999) 361.
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[3] P. Giuseppe, B. Adriano, M. Antonio, J. Environ. Chem. Technol. 1 (1995) 16. [4] I. Takamasa, M. Minoru, K. Takashi, JP: 11191439, 1999. [5] K. Tatsuyuki, K. Yoshimass, S. Hidetoshi, JP: 05247554, 1993. [6] K. Takashi, I. Takamasa, S. Toshio, S. Shigeadi, K. Takeo, JP: 0781941, 1995. [7] G. Xi, Y. Li, Chem. World 11 (2001) 563. [8] G. Xi, Y. Li, Chem. Res. Appl. 6 (2001) 706. [9] W.-H. Lin, S.-K. Jang Jean, C.-S. Hwang, J. Mater. Res. 14 (1) (1999) 205. [10] K. Mandal, S. Pan Mandal, P. Agudo, M. Pal, Appl. Surf. Sci. 182 (2001) 386. [11] B. Li, G. Yin, Z. Zha, C. Zheng, J. Han, Nonferr. Metals 51 (3) (1999) 87. [12] C. Rath, K.K. Sahu, S. Anand, S.K. Date, N.C. Mishra, R.P. Das, J. Magn. Magn. Mater. 202 (1999) 77. [13] N. Shinji, JP: 09156929, 1997. [14] N. Shinji, JP: 05198418, 1993. [15] M. Bremer, St. Fischer, H. Langbein, W. Topelmann, H. Scheler, Thermochim. Acta 209 (1992) 325.