battery aaa alkaline.Research progress on metallurgical treatment of waste nickel-cadmium batteries II

China Battery Network ZXue [11] and others burn the crushed raw materials at a temperature of 600 to 700°C to oxidize the metals and burn away the organic matter. The burned powder is leached with H2SO4. The leaching solution is added with MnO2 and the pH value is adjusted to 4 to 6 to precipitate iron ions. After filtering the solution, add ZXue [11], etc. to burn the crushed raw materials at a temperature of 600 to 700°C to oxidize the metals and burn off the organic matter. The burned powder is leached with H2SO4. The leaching solution is added with MnO2 and the pH value is adjusted to 4 to 6 to precipitate iron ions. After filtering the solution, add


ZXue[11] and others burned the crushed raw materials at a temperature of 600 to 700°C to oxidize the metals and burn off the organic matter. The burned powder is leached with H2SO4. The leaching solution is added with MnO2 and the pH value is adjusted to 4 to 6 to precipitate iron ions. After filtering the solution, add (NH4)2SO4 to precipitate nickel ions in the form of (NH4)2•Ni(SO4)2•H2O crystals, then add NH4HCO3 and adjust the temperature to 70°C and the pH value to 6~6.5. Cadmium precipitates out as CdCO3. Further processing includes dissolving the (NH4)2•Ni(SO4)2•H2O crystals and reprecipitating the nickel ions in the form of Ni(OH)2 and burning the precipitated CdCO3 to decompose it into CdO. Ni(OH)2 and CdO can be used directly as battery raw materials. The recovery rate of nickel is greater than 95%, and the recovery rate of cadmium is greater than 99.66%. In pilot experiments, cadmium metal was recovered through electrolytic reduction, and the purity of the recovered cadmium was greater than 99.82%. You Hong et al. [12] used H2SO4 solution to leach waste batteries to obtain a mother liquor containing nickel and cadmium, and added hydrogen peroxide to dissolve the iron ions in it. Oxidize to Fe3+, adjust the pH value at 70°C to precipitate iron as hydroxide, and then use a rotating disk electrode electrolytic cell to recover cadmium. Add sodium carbonate solution to the electrolyzed solution to adjust the pH value, so that nickel ions are precipitated in the form of nickel carbonate crystals, and the nickel recovery rate can reach 99.5%. 2.3 Electrochemical deposition method The electrochemical deposition method utilizes the difference in electrode potential between nickel and cadmium to directly recover cadmium from the solution through electrolysis to achieve separation of cadmium and nickel. This method can obtain high-purity cadmium, with a purity of more than 99%. The potentials of nickel and cadmium in acidic solutions are -0.246V and -0.403V respectively. In order to prevent the electrodeposition of nickel, the current density must be controlled at a small level to electrolyze cadmium. The separation efficiency is low and the cost is slightly higher. The commonly used electrochemical deposition method first crushes the nickel-cadmium battery, screens out the active materials, and dissolves them with H2SO4 solution. The solution recovers cadmium at the cathode through electrolysis. The purity of the recovered cadmium is 99.5%. After the remaining electrolyte is concentrated, a residue with NiSO4 as the main component is formed. Dissolve the residue with water, then add air or oxidant to oxidize it, then neutralize it with lime, adjust the pH value to 6, filter it, and after the solution is cooled, NiSO4 crystallizes and precipitates. M. Bartolozzi et al. [13] used a mixed solution containing H2SO4 and H2O2 to dissolve waste battery active materials. The solution was adjusted to pH 5 with NaOH and ammonia to precipitate iron ions. After filtration, it was used for electrolytic reduction to recover cadmium. Add NaOH to the remaining electrolyte to adjust the pH to 7, and then add Na2CO3 to precipitate nickel in the form of nickel carbonate. 2.4 Solvent extraction method Solvent extraction method is used to recover metals from waste nickel-cadmium batteries. The extraction agents used include TBP (tri-n-butylphosphonic acid), Lix64 (hydroxyoxime), Kelex120 (hydroxyquinoline), etc. Choosing the appropriate extractant is the key to solvent extraction. Research by CANogueira et al. [14] showed that by controlling the appropriate pH value, DEHPA bis(2-ethylhexyl)phosphonic acid) can well separate cadmium from nickel and cobalt, while Cyanex272 (bis(2,4,4- Trimethylpentyl)phosphonic acid) can effectively separate cobalt and nickel. The separation process is to use H2SO4 solution to dissolve the waste battery, first use DEHPA as the extraction agent to separate cadmium from the solution, and then use Cyanex272 to separate cobalt and nickel. This method has high selectivity and efficiency. The recovery rate of cadmium is as high as 99.7%, and the recovery rate of cobalt is 99.5%. P507 (2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester) can also be used as an extractant to extract cadmium and cobalt at the same time to achieve the purpose of separation from nickel [15]. Under the conditions of pH 4.0, P507 volume fraction 25%, saponification rate 60%, and a ratio of 1:1, through one-stage extraction, the extraction rate of cadmium and cobalt reaches 93.7%, and the extraction rate of two-stage extraction can reach 99.86 %above. The chelating agent Lix64 (hydroxyoxime) or Kelex120 (hydroxyquinoline) can be used to extract nickel from its ammonia complex solution, and the ammonia in the remaining solution is expelled to obtain CdCO3 precipitation. The solution is then heated at 100°C to expel the remaining ammonia and the cobalt precipitates out in the form of hydroxide. C.A.Nogueira and F.Delmas[14] proposed a solvent extraction process for recovering cadmium, cobalt, and nickel from sulfate leachate. The solution used in the test is equivalent to the expected leachate obtained from sulfuric acid leaching of residues containing cadmium, cobalt, nickel and waste rechargeable batteries. The solvent extraction process consists of two loops. One is a cadmium separation circuit, using 1 mol/L organic phosphoric acid DEHPA as the extraction agent, and the other is a cobalt separation circuit, using 0.5 mol/L organic phosphinic acid Cyanex272 as the extraction agent. Under optimal conditions, 99.7% of cadmium is extracted in the cadmium separation loop, and pure cadmium solution can effectively strip the cadmium in the loaded organic phase into the aqueous phase. Metal cadmium with higher purity can be recovered from this aqueous solution. Separate the remaining liquid of cadmium. In the cobalt separation loop, use 0.5 mol/L organic phosphinic acid Cyanex272 to extract cobalt. The cobalt extraction rate reaches 99.5%. The loaded organic phase is washed with pure cobalt solution and the cobalt is recovered through back-extraction. 3 Conclusion The wet treatment process is long, and the discharge of sewage may cause secondary pollution to the environment. How to treat sewage is the key to this technology. Although there is no concern about waste water in pyrometallurgy, attention should be paid to the treatment of waste gas and waste residue. Vacuum metallurgy has the smallest impact on the environment, but the investment in equipment is relatively large, so it should be a better choice in the long run. There are already mature processing technologies for used nickel-cadmium batteries abroad. Domestic research on the processing and recycling technologies for used nickel-cadmium batteries is mostly at the laboratory stage, so this type of technology should be developed into practical applications. Research on the recycling technology of used nickel-cadmium batteries should receive economic support from the state. Publicity and education should be strengthened to promote the recycling of used nickel-cadmium batteries and the clean production and production technology update of nickel-cadmium batteries, so as to minimize or avoid secondary pollution to the environment. .