Development of Metal Recovery Process from Alkaline Manganese Batteries in Sulfuric Acid Solutions

Transcription

1 Materials Transactions, Vol. 48, No. 2 (27) pp. 244 to 248 #27 The Japan Institute of Metals Development of Metal Recovery Process from Alkaline Manganese Batteries in Sulfuric Acid Solutions Shun-Myung Shin, Jin-Gu Kang, Dong-Hyo Yang and Jeong-Soo Sohn* Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources, 3, Gajeong-dong, Yuseong-gu, Daejoen, 35-35, Korea A process for the recovery of from a waste of spent alkaline batteries using sulfuric acid and hydrogen peroxide has been investigated. The proposed procedure consisted of mechanical separation of metal-containing particles and a leaching process. The effects of leaching agent, reaction temperature, time and pulp density for the leaching were also examined. Crushing and sieving of the spent batteries resulted in satisfactory separation of particle size from the waste. 99% and 97% were successfully extracted from the spent battery powder by the leaching at 6 C for 6 min with the addition of hydrogen peroxide as a reducing agent. The hydrogen peroxide addition led to almost doubling extraction compared to without it. [doi:.232/matertrans ] (Received August 21, 26; Accepted November 2, 26; Published January 25, 27) Keywords: spent alkaline batteries, hydrogen peroxide, leaching, manganese, zinc 1. Introduction Over 15 thousand tons of spent batteries a year have been generated in Korea. The spent mercury batteries including mercury and/or silver oxide were treated according to the practice of the deposit-refund system until 22, but uncollected silver oxide and mercury batteries have had a bad effect on the environment. Zinc carbon batteries and alkaline manganese batteries accounting for over 9% of spent batteries can be made to green batteries without mercury. Then, green batteries are treated as a general waste that is simply incinerated and buried at landfill site. However, in case of incinerated and reclaimed battery waste, the metals contained in spent batteries usually leak out in leachate. It can pollute the environment. Therefore, it is necessary to prevent the environment from pollution and contamination, and develop technology for recovering valuable metals from spent batteries. Spent alkaline manganese batteries are composed of approximately 3%, 2%, some magnetic material, and small amount of carbon, plastics and electrolyte. Some of zinc metal in a spent battery are oxidized to zinc oxides and some of O 2 reduced to 2 O 3 after being discharged. An addition of a reducing agent in the acid leaching of chemically stable manganese oxide can contribute to the increase of leaching efficiency. 1 5) Hydrogen peroxide is generally known as an oxidant, but it acts as an amphoteric agent when it is coexisting with a stronger oxidant such as manganese dioxide. To increase the extraction of manganese compound from crushed spent battery powder mixed with zinc and manganese compound, some leaching experiments were conducted with an addition of hydrogen peroxide. Leaching behavior of and in a sulfuric acid solution with and without hydrogen peroxide as a reducing agent was examined in various conditions such as sulfuric acid concentration, reaction temperature, reaction time and amount of reducing agent. 2. Experimental 2.1 Sample Preparation Spent alkaline batteries in an amount of kg were collected from a Seoul city. A series of mechanical processing is conducted in the following sequence to yield enriched and particles: crushing, magnetic separation, sieving and classification. After spent alkaline batteries were crushed and separated by magnetic separation, the non-magnetic material was subjected to screening with a 8 mesh sieve as shown in Fig. 1. Thus, the physical treatment applied herein yielded 3 kinds of fraction, namely, magnetic material, nonmagnetic 8 mesh oversize and undersize. The 8 mesh undersize was used as a feedstock for leaching experiment. The composition of the 8 mesh undersize was determined to be 21.3% and 3.1% by atomic absorption spectrometry (SpectrAA-4, Varian). In this experiment, two reagent grade chemicals were used: sulfuric acid (Junsei chemical Co., Japan) and hydrogen peroxide (Junsei chemical Co., Japan). Spent alkaline batteries Magnetic material Crushing Magnetic separation Non magnetic material 8 mesh Oversize 8 mesh Undersize Plastics, etc Chemical treatment *Corresponding author, jss@kigam.re.kr Fig. 1 Process diagram of physical treatment.

2 Development of Metal Recovery Process from Alkaline Manganese Batteries in Sulfuric Acid Solutions 245 Contents of valuable metals(%) 3 2 Fe Ni A B C Total Fig. 3 Content of valuable metals in spent alkaline batteries. (in kg). (A: magnetic material, B: non-magnetic material +8 mesh, C: nonmagnetic material 8 mesh) Fig. 2 Schematic diagram of leaching apparatus. motor, reactor, fi heat mantle, fl controller, impeller, condenser, thermometer, burette, sampler. Table 1 The Size fractions of spent alkaline batteries. Battery Magnetic Non magnetic material (%) size Material (%) Total þ8 mesh 8 mesh Loss (%) AAA AA C, D Ave Leaching procedure An experimental equipment shown in Fig. 2 was used for all leaching tests. A 5 ml sulfuric acid solution was poured into a five-neck glass flask wrapped with a heating mantle. After the solution temperature was stabilized, hydrogen peroxide was poured first and the spent battery powder was added next, and the solution was agitated with a teflon paddle at a constant agitation speed 2 rpm for one hr. A ml solution was sampled for analysis at a fixed interval during a leaching experiment. 3. Results and Discussion 3.1 Content of valuable metals in spent alkaline batteries The amount of each fraction in spent alkaline batteries was investigated and shown in Table 1. The spent alkaline batteries were separated into 23.8% magnetic material and 73.1% non-magnetic material consisting of 12.5% 8-mesh oversize and 6.6% 8-mesh undersize, being a loss of 3.1%. The selected elemental analysis of the spent alkaline batteries and their fractions are shown in Fig. 3. The batteries Concentration of H 2 SO 4 (kmol/m 3 ) Fig. 4 The effect of sulfuric acid concentration on the leaching of and without a reducing agent. (6 C, 2 rpm and 6 min). contain 2.3% Fe, 2.9%, 17.7% and 1.% Ni. However, the fractions indicate quite different results. The magnetic material contains 19.6% Fe whereas the nonmagnetic material for the 8 mesh oversize and 8 mesh undersize only.1% and.5% Fe each. Therefore, most of Fe in the batteries can be readily recovered by magnetic separation. It is interesting to note that the non-magnetic 8-mesh undersize contains most of (91%) and a large portion of (76%) available in the feed. 3.2 Leaching behavior of and without a reducing agent Figure 4 shows the extractions of and at different

3 246 S.-M. Shin, J.-G. Kang, D.-H. Yang and J.-S. Sohn Temperature( o C) Fig. 5 The effect of temperature on the leaching of and. (1. kmol/m 3 H 2 SO 4, 2 rpm and 6 min). sulfuric acid concentrations from the 8 mesh undersize by leaching at 6 C, mass% pulp density (5 g feed in 5 ml solution) and 2 rpm for 6 min without a reducing agent. The extraction increased from 76 to 98% as the sulfuric acid concentration increased from.5 to 2. kmol/ m 3. On the other hand, less than 45% was extracted over the entire range of the acid concentration although the extraction gradually increased with increasing the acid concentration. Also the effect of reaction temperature on the leaching experiment without a reducing agent was investigated. Figure 5 shows the leaching efficiency of and according to reaction temperature at g/l pulp density, 1. kmol/m 3 H 2 SO 4, 6 min As shown in the figure, The extraction increased with increasing reaction temperature, reaching 96% at 8 C. However, the extraction remained low between 31% and 39% throughout the temperature range of 4 to 8 C. 3.3 Leaching Behavior of and with Hydrogen Peroxide Hydrogen peroxide can reduce hardly-soluble O 2 to (II) in sulfuric acid solution (Reaction 1). 6) O 2 þ H 2 SO 4 þ H 2 O 2! SO 4 þ 2H 2 O þ O 2 : ð1þ Hence, the addition of H 2 O 2 as a reducing agent has a possibility to increase the extraction of from the battery powder. Figure 6 shows the effect of leaching time on and extractions at 3. kmol/m 3 H 2 SO 4 with a 3 ml H 2 O 2 addition (refer to Section 3.4 and Fig. 7) at a pulp density of wt% and 6 C. Apart from Figure 4, the leaching of the spent battery powder with the peroxide addition was very fast. The extraction reached instantaneously up to 81%, 97% in 5 min and near completion in min. The leaching efficiency of was similar to the extraction, reaching 78% at the beginning, 94% in 5 min and 97% thereafter Time (min.) Fig. 6 The effect of reaction time on the leaching ratio of and with H 2 O 2 as a reducing agent. ( mass% Pulp Density, 3. kmol/m 3 H 2 SO 4, 3 ml H 2 O 2,6 C and 2 rpm) Amount of H 2 O 2 (ml) Fig. 7 The effect of amount of H 2 O 2 on the leaching ratio of and. ( mass% Pulp Density, 3. kmol/m 3 H 2 SO 4,6 C and 2 rpm). Hydrogen peroxide was proven to be a strong reducing agent, nearly completing the extraction of from the spent alkaline battery powder in min. 3.4 Effect of H 2 O 2 amount Figure 7 shows the effects of H 2 O 2 amount on and extractions during leaching the spent batteries for 6 min at wt% pulp density, 3. kmol/m 3 H 2 SO 4 and 6 C. was extracted almost completely regardless of the H 2 O 2 amount tested, but the extraction increased from 89.8% to 97.1% to 99.7% as the H 2 O 2 addition increased from 2 to 3 to

4 Development of Metal Recovery Process from Alkaline Manganese Batteries in Sulfuric Acid Solutions Concetration of H 2 SO 4 (kmol/m 3 ) Fig. 8 The effect of sulfuric acid concentration on the leaching ratio of and with H 2 O 2 as a reducing agent. ( mass% Pulp Density, 3 ml H 2 O 2,6 C and 2 rpm) Temperature( o C) Fig. 9 The effect of temperature on the leaching ratio of and with H 2 O 2 as a reducing agent. ( mass% Pulp Density, 3. kmol/m 3 H 2 SO 4, 3 ml H 2 O 2 and 2 rpm). 4 ml. An addition of 3 ml H 2 O 2 seems to be sufficient for satisfactory recovery under the leaching conditions tested. 3.5 Effect of sulfuric acid concentration Figure 8 shows and extractions as a function of sulfuric acid concentration in the.5 to 3 kmol/m 3 range under the leaching conditions of wt% pulp density, 6 C, 3 ml H 2 O 2 and 6 min. The extraction gradually increased with increasing acid concentration from 96% to 99%, however, the extraction was more sensitive to the H 2 SO 4 concentration, increasing from 54% to 96%. 3.6 Effect of reaction temperature Figure 9 shows the and extractions as a function of leaching temperature in the range of 5 to 8 C under the conditions of 6 min, 3 ml H 2 O 2, mass% pulp density and 3. kmol/m 3 H 2 SO 4. Both the and extractions were found to be insensitive to the leaching temperature, reaching over 9% throughout the temperature range applied. 3.7 Effect of pulp density The and extractions as a function of pulp density under the conditions of 3 ml H 2 O 2, 3. kmol/m 3 H 2 SO 4, 6 C and 6 min are shown in Fig.. As expected, the extraction gradually decreased, but the extraction dropped sharply from 97.1% to 7.% more sharply as the pulp density increased from to 3 wt%. Although higher pulp density leads to a some drop in the metal extraction, there is a benefit of obtaining a higher metal concentration in the leach liquor. 4. Conclusions In this study, leaching behavior of the spent alkaline Pulp Density (wt%) Fig. The effect of pulp density on the leaching rate of and with H 2 O 2 as a reducing agent. (3. kmol/m 3 H 2 SO 4,3mLH 2 O 2,6 C and 2 rpm). battery powder was investigated for developing a process recycling manganese value in the batteries. We can conclude in the following based on the important results of this study: (1) 99% of and 97% of can be successfully extracted from the spent batteries at 6 C, wt% pulp density for 6 min and 3 kmol/m 3 H 2 SO 4 and 3 ml H 2 O 2. The presence of the reducing agent enhances the extraction almost two times, compared to without it. (2) As the H 2 O 2 addition increases from 2 to 4 ml under the above conditions, is extracted almost completely regardless of the H 2 O 2 amount, but the extraction increases from 89.8% to completion.

5 248 S.-M. Shin, J.-G. Kang, D.-H. Yang and J.-S. Sohn (3) As the H 2 SO 4 concentration increases from.5 to 3 kmol/m 3 under the above conditions, the extraction gradually increases from 96% to 99% with increasing acid concentration. however, the H 2 SO 4 concentration leads to the extraction, increasing from 54% to 96%. (4) The optimum leaching conditions for the successful recovery of from the spent alkaline batteries seem to be 6 C, wt% pulp density, 6 min, 3 kmol/m 3 H 2 SO 4 and 3 ml H 2 O 2. Acknowledgement This study was supported by a grant operated by the Resource Recycling R&D Center, a 21C Frontier R&D Program of the Ministry of Science and Technology (MOST) of Korea. The authors would like to thank MOST for the financial support. REFERENCES 1) S. M. Shin, J. S. Sohn, D. H. Yang, J. G. Ahn, S. K. Kim and H. T. Sohn: J. of Korean Inst. of Resources Recycling 41 (24) ) J. S. Sohn: Proceeding of International Congress for Battery Recycling, (23). 3) H. T. Sohn, J. G. Ahn, J. S. Sohn, K. H. Park and I. Y. Park: J. of Korean Inst. of Resources Recycling 11 (22) 44. 4) K. H. Park, J. S. Sohn and J. S. Kim: Geosystem Eng. 5 (22) 8. 5) M. Kawahara and T. Mitsuo: J. of The Mining and Material Processing Inst. of Japan 8 (1992) ) T. Jiang, Y. Yang, Z. Huang, B. Zhang and G. Qiu: Hydrometallurgy 72 (24)