Study On The Technology Of Resourceful Utilization And Innocent Treatment Of Lead-Rich Residue

In the hydrometallurgical extraction process of silver, some by-product of residue, with the lead content more than 60%, deposited on the bottom of extraction pot, is one of the hazardous solid waste, which called lead-rich residue. At present, lead-rich residue is stockpiled according to the national standards. However, stockpiling exists serious environmental pollution risks and waste of lead resources in the long-term. In order to improve the utilization of resource, eliminate environmental pollution risks. In this study, calcium chloride leaching-recovery-cycling-stabilization process was chosen. The aim is to separate lead from the lead-rich residue, realize the resourceful utilization of residue and conduct stabilization treatment of residual lead, converting it into a general solid waste. The processes of leaching lead with calcium chloride, recovering of lead chloride, recycling of lead leaching solution and stabilization of lead leaching residue were studied in this study, and the results are as follows:（1） In the process of lead leaching with chloride, the optimum conditions were as follows:the mechanical stirring speed was 500 r·min^-1, the concentration of chlorine ion was 10 mol·L^-1, the ratio of liquid-solid was 8:1, the reaction temperature was 80℃, the concentration of hydrochloric acid was 1 mol·L^-1, the reaction time was 20 minutes. Influence of chlorine ion concentration and the ratio of liquid to solid on leaching rate of lead were more significant than other factors. Under the above conditions, the leaching rate of lead can reach 93.54%.（2） In the process of lead recovering, the optimum conditions were as follows:the precipitation temperature was 30 ℃, the precipitation time was 20 min and the dilution rate was 1:1.75. Under the optimum conditions, the recovering rate of lead was above 90%. The leaching rate of lead was 86.61% and the recovering rate of lead was more than 85% after cycling the lead leaching solution four times.（3） In the process of stabilization of lead leaching residue, the molar ratio of Pb-S is the main factor affecting the stabilization. The optimum conditions were as follows:the molar ratio of Pb-S was 1:1.25, the reaction temperature was 30℃, the reaction time was 20 minutes, the ratio of liquid-solid was 3:1 and the stirring speed was 300 r·min^-1. Under this condition, the leaching toxicity of lead residue is 2.71 mg·L^-1, lower than the national standard limit 5 mg·L^-1.（4） After the above process, lead in lead-rich residue is extracted efficiently and made into qualified lead chloride product, turning the lead leaching residue into a general solid waste, and realizing the resourceful utilization and innocent treatment of lead-rich residue finally.