Extraction Of Lead And Zinc From Leaching Residue By Vacuum Carbothermal Reduction

Zinc hydrometallurgy is the main way to extract zinc from sphalerite,and neutral leaching-electrodeposition process is generally used to extract metallic zinc.During the leaching process,a large amount of leaching residue will be generated,the yield of the residue is about 0.4-0.5 tons /t-Zn,the zinc content in the residue is about 20%,and at the same time it also contains valuable metals such as lead,silver,indium,etc.Therefore,it is of great significance for the comprehensive recovery of valuable metals in the leaching residue.In this paper,the extraction of lead and zinc from zinc leaching residue was studied by vacuum carbothermic reduction method,and the behaviors of sulfur,indium and silver in the extraction process of lead and zinc were studied.Thermodynamic analysis of the reduction process of lead,zinc and other metals in residue can effectively reduce the reduction temperature of lead and zinc under vacuum conditions.The metal extraction process can be shortened by directly obtaining metals such as metallic lead,zinc,silver,indium and the like.The results show that the volatilization rates of lead and zinc reach 99% and 99.82% respectively,the volatilization rate of silver reaches 74.62%,the volatilization rate of indium reaches more than 95%,and the sulfur fixation rate reaches 68.49% when the temperature is kept at 1100? for 30 min,the carbon content is 18.5%,and the Ca O content is 5.5%.Fe2O3 and Ca O can promote the reduction and volatilization of metals such as lead and zinc in residue,Fe2O3 is partially reduced to metallic iron,and iron can reduce sulfide of lead and zinc;Ca O not only increases the melting point of residue,but also produces displacement reaction with lead-zinc sulfide.The reduction process of lead in residue is as follows: part of lead is directly reduced to metallic lead,the other part is converted to Pb S,Pb S is reduced to metallic lead by iron,and Pb SO4 also reacts with Pb S to generate metallic lead.The reduction process of zinc in residue is as follows: zinc oxide generated by thermal decomposition of Zn O·Fe2O3 during vacuum carbothermic reduction is partially converted into Zn S by reduced Zn SO4,Zn S is promoted by Fe and Ca O,and partially reduced into metallic zinc vapor.