The Novel Process Study On Comprehensive Recovery Of Silver Separated Residue From Copper Anodic Mud

Silver separated residue (SSR) is an important by-product after which the copper anode mud had been extracted silver, which contains lead (Pb), bismuth (Bi), tin (Sn), antimony (Sb), tellurium (Te), gold (Au), silver (Ag) and other valuable metals. For the Daye Nonferrous Metals Company rare and precious metal Plant can not handle the SSR. With analysis of the SSR’s composition and the presence of metal form, after theoretical analysis and practical investigation, a suitable process was selected.To the question of valuable metals can not be comprehensive recovery in SSR, this paper presented the process, firstly the precious metals and other valuable metals in SSR was selectively separated by molten salt system of NaOH/Na2S, following the preparing of chemical product antimony and tin by oxide and double decomposition precipitation, finally lead、bismuth、gold、silver, in leaching residue, formed precious lead in low temperature alkaline smelting procedure. The research in the laboratory scale and extensive plant tests had been carried out in this paper. The main content and conclusions were as follows:(1) The research in the laboratory scale was carried out:the optimum conditions of the low-temperature alkaline smelting leaching in molten salt system of NaOH/Na2S of SSR were determined. When the ratio of NaOH to SSR was0.4and Na2S·9H2O to SSR was2.0, smelting temperature was500℃, smelting time was60min, leaching temperature was80℃, leaching time was60min, liquid to solid ratio was5:1～6:1, the stirring speed was300rpm, the leaching rate of antimony, tin and arsenic was87.7%,95.5%and63.0%respectively, the main phases of elements in the leaching residue were PbS and Bi2S3; the sodium antimonate was precipitated by adding the hydrogen peroxide into the leaching solution, thus, the antimony and the tin were well separated. The results showed that the optimum conditions were as follows, when the dosage of the hydrogen peroxide was three times of the theoretical amount, the concentration of the hydrogen peroxide was10%and the reaction time was2hours for the oxidation process, the rate of antimony was above99%, and arsenic isnot precipitated. The main specific diffractive peak of the product was cubic NaSb(OH)6; Then, according to exploratory experimental research by adjusting the pH of solution after which antimony had been precipitated, when the optimum pH conditions for the tin precipitation process was8-9, the rate of tin precipitation was about87%, while by adding Ca(OH)2into the solution after which antimony had been precipitated, the rate of tin precipitation was about84.53%, the main phases of the precipitation was CaSn(OH)6; according to the research that produce precious lead by low temperature alkaline smelting, when smelting temperature was700℃, smelting time was120min, leaching residue was20g, the dosage of NaOH was60%of the leaching residue, coke powder was2g, the recovery rate of Pb, Bi, Au, Ag was95%,82%,100%and100%, respectively. About80%of Te was left in the residue;(2) The research in industry scale was carried out:the conclusions of previous research in the laboratory scale are verified, the recovery rate of Sn, Sb, Pb, Bi, Au and Ag was89.52%,98.34%,94.63%,99%,98.34%and96%, respectively. While the recovery rate of Te was97.8%, according to industrial design and benefit analysis, a remarkable environmental benefit and economic benefit could be achieved by recovering2000tons of SSR.All the results show that the low temperature alkaline smelting-leaching-selective precipitation-producing precious lead by low-temperature alkaline smelting process of SSR is feasible. However, there are no any other papers about the process. The study of recycling SSR and secondary materials has a great practical and promotive meaning in China.