Application Basic Research On The Preparation Of High-purity Lead Oxide From Waste Lead Paste Of Lead-acid Batterie

Lead-acid battery is the most widely used battery in the world with the largest production and market share.It has many advantages such as stable voltage,safe operation,long life and high cost performance.Based on these advantages,lead-acid batteries have been widely used in many applications.However,with the scarcity of lead resources,the recycling of lead resources in spent lead-acid batteries has become particularly important.In addition,if spent lead-acid batteries are not treated properly,they can also cause serious harm to the environment and human body.Therefore,the treatment of spent lead-acid batteries has a high economic and environmental value.The most valuable part of the spent lead-acid batteries is the spent lead paste,and the basic research on the conversion of the spent lead paste into high purity lead oxide is carried out in this project with the spent lead paste as the raw material.（1）The spent lead-acid batteries were manually disassembled to obtain the spent lead paste.The composition of the spent lead paste was determined by chemical titration and inductively coupled plasma-atomic emission spectrometry.The composition determination showed that the main components of the spent lead paste were Pb SO₄,Pb O,Pb O₂ and Pb.In addition,there were many other metal impurities in the spent Pb paste,such as Ca,Al,Ba,Sn,Sb and Fe,etc.,which needed to be removed by some subsequent means.（2）A mixture of sulfuric acid,hydrogen peroxide and sodium chloride was used to sulfate the spent lead paste,and the sulfated lead paste was obtained by filtration.The optimum conditions for the sulfation of spent lead paste were:solid-liquid ratio of100 g·L^-1,sulfuric acid concentration of 2.5 mol·L^-1,molar ratio of H₂O₂/Pb O₂ of 2.0,reaction temperature of 60°C and sodium chloride concentration of 100 g-L-1.Under these conditions,all the spent lead paste could be converted into lead sulfate and a large amount of metal impurities in the spent lead paste could be effectively removed.（3）Conversion of sulfated lead paste to high purity lead oxide by the process of desulfurization of ammonium acetate and carbonization.The ammonium acetate solution is used to desulfurize the sulfated lead paste to obtain the mother liquor.After adding glycerol to the mother liquor and distilling,the glycerol solution of lead acetate is obtained.After obtaining,adding a carbonizing agent to the glycerin solution of lead acetate for carbonization,and calcining the carbonized product after carbonization can obtain high-purity lead oxide.The optimum conditions for desulfurization leaching from ammonium acetate solution were:a solid-liquid ratio of 50 g·L^-1,an ammonium acetate concentration of 30 wt%,a reaction temperature of 40°C and a reaction time of7.5 min.Under these conditions,complete leaching of lead from sulfated lead paste could be achieved.In the carbonization process,ammonium carbonate solution was chosen as the carbonizing agent,and a high purity lead carbonate product could be obtained by reacting at a molar ratio of CO₃^2-/Pb of 1.10 for 20 min.Calcination of high-purity lead carbonate products can obtain high-purityα-Pb O.（4）Conversion of sulfated lead paste to high purity lead oxide by sodium chloride desulfurization crystallization method.High-purity lead chloride products can be obtained by using sodium chloride solution for desulfurization leaching of sulfated lead paste and low-temperature crystallization of the leachate.high-purity lead oxide can be obtained by using sodium hydroxide solution for dechlorination of lead chloride products and low-temperature crystallization after dissolution.The optimum conditions for desulfurization leaching from sodium chloride solution are:solid-liquid ratio of 40g·L^-1,Na Cl solution concentration of 250 g·L^-1,reaction temperature of 80°C and leaching time of 20 min.Under these conditions,the lead in sulfated lead paste can reach complete leaching.In the low-temperature crystallization process,the leachate was diluted 1.6 times and placed at a temperature of 0°C for crystallization to obtain a high-purity lead chloride product with a recovery of 99.18%.The dechlorination of lead chloride was carried out by sodium hydroxide solution,and the dechlorination crystallization conditions were optimized by response surface methodology.The lead chloride product was dechlorinated by dissolution at a solid-liquid ratio of 136.09 g·L^-1 and the concentration of sodium hydroxide solution was 11.51 mo·L^-1 and crystallized at 0℃to obtainα-Pb O with a lead recovery of 85.66%.In the dechlorination process,different crystalline forms of lead oxide can be obtained by controlling the concentration of sodium hydroxide solution.（5）The recovered lead oxide was assembled into lead-acid batteries for testing.The initial discharge performance showed that the initial capacity of the lead oxide recovered by the process of desulfurization of ammonium acetate and carbonization was 85.7 m Ah/g,and the initial capacity of the lead oxide recovered by the process of desulfurization of sodium chloride and crystallization was 84.3 m Ah/g,both of which were higher than the initial capacity of commercial lead oxide powder of 81.4 m Ah/g.The cycling performance showed that after 200 cycles of the battery,the capacity of the lead oxide recovered by the process the process of desulfurization of ammonium acetate and carbonization was 79.7%of the initial discharge capacity,and the capacity of the lead oxide recovered by the process of desulfurization of sodium chloride and crystallization was 81.3%of the initial discharge capacity,while the capacity of commercial lead oxide powder was 62.6%of the initial discharge capacity.