Research On The Extraction And Separation Of Copper, Cadmium And Zinc From Coper-cadmium Residue

In this study, the particle size analysis and XRD analysis of the copper-cadmium residue produced by Huludao Zinc Plant have been conducted, Results showed that the average particle size of the residue is17.241μm, Cadmium exists mainly in the state of cadmium sulfate, and zinc exists mainly in the forms of sulfate and oxide, the form of copper is a little complicated, consist of copper metal, copper oxide and copper sulfate.Leaching of copper, cadmium and zinc from the residue have also been researched by direct leaching with dilute sulfuric acid and followed by manganese dioxide oxidating leaching, The separation of copper from direct leaching solution were also studied. Test results show that, in the first stage leaching, the optimal conditions of acid leaching is as following, the liquid-to-solid ratio of3:1,6%sulfuric acid concentration, stirring speed300rpm,30minutes of reaction time, reaction temperature25℃, the leaching rate of Cu, Cd, Zn are21.68%,97.89%and97.96%separately. In the second stage of leaching, the optimal conditions of oxidative leaching is at15:1of liquid-to-solid ratio, the sulfuric acid concentration of7%, MnO2consumption is at0.85times of the theoretical amount, stirring speed300rpm., reaction time of60minutes.The leaching rate of Cu, Cd, Zn were99.6%,97.5%and79.1%separately under this condition. After two stages of leaching, leaching rate of Cu, Cd, Zn amount up to99.6%,99.95%and99.57%.We tested the extraction of copper with20%LIX973-kerosene system under different phase ratio (O/A) conditions from the first stage leaching solution, which containing1.715g/1of H2SO4,12.6g/1of Cu2+and high concentration of Zn2+.The results show that when phase ratio (O/A) was kept at1:1, the copper concentration in raffinate can be decreased to about0.2g/1through threee stages of countercurrent extraction. It means a high efficient extraction recovery of copper can be reached from zinc sulfate solution. The copper loaded organic phase was stripped with180g/l of sulfuric acid solution with and without14.9g/1Cu2+separately, Results showed that both stripping solution can reach high stripping recovery although Cu2+has a adverse efffect on the stripping of copper.When we separate zinc from the oxidizing leaching solution at pH1.9by solvent extraction with6.8%P204-kerosene under1:1phase ratio, zinc recovery reach33.92%. Under the same time, the separating coefficients of Zn/Cu, Zn/Cd and Zn/Mn are37.55,31.91and14.07separately. But when the concentration of P204in organic phase increases to25%, The recovery of zinc reach up to55.41%.And the the separating coefficients of Zn/Cu, Zn/Cd and Zn/Mn are33.86,24.61and31.00separately. The results of solvent extraction of zinc by P204showed that the increase of initial solution pH, P204concentration in organic phase and phase ratio are all advantageous to the recovery of zinc and the separation of zinc from other metals in solution.