Study Of New Technique Of Lead Recovery From Lead Paste In Spent Lead Acid Battery By Hydrometallurgical Desulfurization And Electrodeposition

An important way for the sustainable development of the lead industry is to recycle and clean the lead paste.Lead-acid battery paste is classified as hazardous waste in most countries,and it is also an important secondary resource for recycling lead industry.At present,the pyrometallurgy recycling processes usually involves a series of high temperature reaction processes along with SO₂ and lead flue dust were unintentionally released into the atmosphere,and tremendously caused unfavorable effect to environment.Therefore,it is of great significance to develop the hydrometallurgical process with high recovery and low environmental pollution to realize the recycling development of lead resources.Under such a circumstance,the objective of this work is to seek a more efficient method to obtain lead product.There are three typical technologies as follows:hydrometallurgical conversion desulfurization with carbonate,the desulfurization precursor calcination and lead recovery by alkaline system electrodeposition.Finally,the optimum parameter conditions for each stage of the process are obtained.The main research content and experimental results of this paper are as follows:?1?The effect of carbonate solution on the desulfurization efficiency of lead paste from lead-acid battery was studied firstly.Based on the analysis of chemical components of lead paste from the spent lead acid battery,the desulfurization efficiencies of different conversion agent in the same condition was determined as:Na₂CO₃ and?NH₄?₂CO₃ had better desulfurization effect than NH₄HCO₃.And the XRD characterization results showed that the lead sulfate can be transformed into pure lead carbonate using two kinds of ammonium salt carbonate,however,the double phase NaPb₂?CO₃?₂OH was produced when desulfurized by sodium carbonate.The optimum processing conditions using ammonium carbonate as transforming agent were also detected and determined as follows:ammonium carbonate concentration is 0.5mol/L,leaching temperature is 50?,reaction time is 60min,stirring speed is 500r/min and liquid-solid ratio is 5:1,more than 98.43%of lead sulfate was transformed with the above conditions.The kinetics results indicated that the reaction obeyed shrinking-core model controlled by diffusion,and the general equation of kinetics of the desulfurization process was established as 1-?2/3??-?1-??^2/3=0.2286c^3.38v^0.809exp{-16470.53/?RT?}t.?2?The thermal analysis results of desulfurization precursors in different atmospheres were analyzed and the optimum atmosphere and temperature conditions for the preparation of?-PbO,?-PbO and Pb₃O₄ were determined.The results suggested that the decomposition process of the precursor is relatively simple due to the inert gas suppressing the formation of intermediate lead oxide in argon.When the temperature is450?,?-PbO is the only phase in calcination product.In the air atmosphere,when the roasting temperature is 480?,Pb₃O₄ was identified as the only phase in calcination product,as the temperature rise to 620?,the final calcination product?-PbO was produced.?3?The dissolution behavior of lead oxide in an alkaline xylitol system was investigated.The possibility of dissolving lead in alkaline system was demonstrated from the view point of thermodynamics,and the effect of different leaching parameters on lead dissolution was studied.The results showed that lead exsit in the alkaline solution in the form of Pb?OH?₃^–and the addition of xylitol could significantly increase the solubility of lead oxide.The optimized process conditions are as follows:sodium hydroxide concentration is 100g?L^-1,xylitol concentration is 150g?L^-1,dissolving temperature is 50?,reaction time is 90min,liquid-solid ratio is 5:1,stirring speed is600r/min,the obtained dissolved concentration of PbO is 151g?L^-11 with the above dissolving conditions.?4?The electrodeposition behavior of lead in alkaline solution containing xylitol solution was studied by cyclic voltammetry and linear sweep voltammetry.Electrochemical results showed that the deposition of lead on the platinum electrode is an irreversible process,and the deposition process of lead under different electrolysis parameters is discussed.