Removing impurities and enrichment of rare and precious metals of copper anode slime by hydrometallurical pretreatment
Efficient pretreatment for removing impurities of copper anode slime is a crucial pre-requisite step in the separating and refining of rare and precious metals.In this paper,based on the physical and chemical characteristics of copper anode slime,a novel process of selective autocatalytic oxidation impurity removal and efficient enrichment of rare and precious metals in H2SO4-H2O2 system was proposed.The effects of various factors on the leaching rates of Cu,As,Se and Te were investigated.The results show that the main phases of copper anode slime are PbSO4,CuSO4,Ag2Se,Cu2Te,Cu2Se and Cu.Under the optimum conditions of H2SO4 dosage of 120 mL/kg,H2O2 dosage of 260 mL/kg,liquid-solid mass ratio of 5∶1 reaction temperature of 35℃and reaction time of 1 h,the leaching rates of Cu and As are 98.33%and 58.22%,respectively;the leaching rates of Se and Te are only 7.49%and 23.97%,respectively,while Au and Ag are not leached.The microstructure of the leaching residue is shown as mosaic agglomerate particles with 50-100 nm in size,mainly composed of PbSO4,Se,Ag2Te and Ag phases.The phases of Cu2Te,Cu2Se and Ag2Se in the raw materials disappear obviously.The contents of enriched Ag and Au in leaching residue are 9.33%and 0.293%,respectively.The enrichment ratio is 1.5,and Cu content decreases from 14.30%to 0.39%,which achieves the requirements of subsequent precious metal separation and refining.The process achieves efficient separation of impurities and targeted enrichment of rare and precious metals at room temperature and atmospheric pressure of copper anode slime.
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