Study On New Recovery Technology And Electrochemical Performance Of High Purity Lead And α-PbO From The Spent Lead Acid Batteries

Lead acid batteries become largest output secondary batteries and are widely used in engine vehicles,communication equipment,energy storage in the world wide for their good reliability,long cycle life,low price,high-current charge-discharge and safety advantages.However,the accumulation of large amount of spent lead acid batteries caused severe problems of lead recovery,which are the focus of research throughout whole lead industries.In order to overcome high energy consumption and secondary contamination by lead vapor and lead dust of pyrometallurgical recovery processes,lead recovery mode with the center of "metallic lead"was provided,including the following processes:spent lead pastes are smelted into crude lead by smelting;the crude lead is refined by electrolytic or pyro-refining method to obtain refined lead;the refined lead is oxidized into PbO.But this lead recovery mode still has a series of problems,including complex process,high energy consumption and low utilization rate,many researchers started to pay great attention to the direct recovery of PbO from spent lead-acid batteries.In this paper,aiming to the problems of high-power,low efficiency and electrolyte pollution of electrolytic refining process of the wet recovery of metallic lead,we develop a clean,energy-saving and high efficient electrolytic refining process in a novel perchloric acid（HClO4）system.To solve the serious problems of the existing process of PbO recovery,incluidng the waste leady solutions are hard to recycle,desulfurization is incomplete and the purity of PbO is not up to the standard of the battery grade,we design a novel recovery method to obtain high purity of a-PbO from spent lead-acid batteries via the desulphurization-recrystallization processes in sodium hydroxide（NaOH）solution or the leaching-carbonization-thermal decomposition processes in conjugated solution of ROH-R₂SO₄ of crude PbSo4 obtained by catalytic sulfation of spent lead pastes and spent lead grids.1 Electrolytic Refining of Crude Lead in HClO4 SystemIn this process,the mixed solution of perchloric acid and lead perchlorate（HClO4-Pb（ClO₄）₂）with the additives of gelatin and sodium lignin sulfonate are employed as the new electrolyte.By studying the stability and feasibility of HClO₄ as the electrolyte,it is proved that the HClO₄ solution is stable without the reduction reactions of the ClO4-ions in 1-5 mol L-1 HClO₄ below 65 ℃.The effects of concentrations of HClO₄ and Pb²⁺,temperature and current density on the energy consumption and electrodeposition of the electrolytic refining process are systematically studied.Under the optimum conditions of 2.8 mol L-1 HClO₄,0.4 mol L-1 Pb（ClO₄）₂,and electrolysis temperature of 45 ℃,the scale-up experiments are carried out.Under the same current density of 20 mA cm-2,the energy consumption of electrolysis refining of our new process is about 1/3 of that of Betts method,and the purity of the refined lead comes up to 99.9992%.2 Catalytic Sulfation Process of Spent Lead Pastes and Spent Lead GridsBy using spent lead pastes,spent lead girds and spent sulfuric acid（H₂SO₄）as raw materials,the effects of concentration of H₂SO₄,reaction temperature,composite catalyst and reaction time on sulfation conversion are systematically studied and the catalytic mechanism of Fe²⁺ for Pb-PbO₂ solid phase reaction is studied emphatically.Under the optimum conditions of H₂SO₄ 2.0 mol L-1,temperature 65 ℃,0.10 mol L-1 Fe²⁺,0.10 mol L-1 ethylenediamine,0.10 mol L-1 Ammonium chloride（NH₄Cl）reaction time of 4 h,the conversion rate keeps between 99.2%and 99.6%for the first 8 cycles.3 The Desulphurization-Recrystallization Process of Crude PbSO₄ in NaOH SolutionCrude PbSO₄ is desulfurized with the ratio of amount of substance o to NaOH 1:2.8 in 10 wt.%NaOH solution for 10 min,the desulfurization rate reaches 98%.By-product Na₂SO₄·10H₂O is obtained from the desulfurization solution.The masses of Pb²⁺ and SO42-keep material balance during the desulfurization process.During the recrystallization process,the flake-like β-PbO are obtained in the NaOH with low concentrations,the granular,high purity α-PbO are obtained in the NaOH with high concentrations,and time,temperature and agitation speed are controlled to obtain PbO crystals with the suitable particle size.The tests of initial capacity,large current discharge,low temperature acceptance performance and cycle life of batteries produced by recovery a-PbO are carried out,indicating that the electrochemical performance was better than that of traditional batteries in the previous 350 cycles.4 The Leaching-Carbonation-Thermal Decomposition processes of Crude PbSO₄ in The Conjugated Solution of ROH-R₂SO₄.This process consists of leaching,carbonation,and thermal decomposition processes.in sequence to recover high-purity a-PbO and recycle the conjugated solution and carbon dioxide（CO₂）.During the leaching process,we systematically studied the dissolution and separation of Crude PbSO₄ in conjugated solution,and under the optimum conditions of 2.0 mol L-1 R₂SO₄,12.5 mol L-1 ROH and reaction time 20 min,the solubility of lead sulfate was up to 113 g L-1.During the carbonation process,the impact of temperature,stirring speed,aging time,and concentration of Pb²⁺ on the morphology of PbCO₃ were optimized.At the optimal thermal decomposition temperature of 450 ℃,a-PbO is obtained with a high purity of 99.992%.The leaching rate of PbSO₄ from lead paste is up to 99.8 ± 0.15%,and the recovery rate of lead is 99.85%.The recovered a-PbO exhibits a better performance than the a-PbO obtained by the conventional Shimadzu ball-milling method during the first 350 cycles.