Leaching Of Gold And Silver From Nickelic Copper Anodic Slime

Different copper anode slime has different generation, sources and compositions, so the treatment process to anode slimes are not the same. Nickelic copper anode slime is one of stubborn anode slimes, apart from high nickel to the slimes, It contains a mass of precious and scattered metals. To reclaim precious metals from high nickel anode slime, by pretreating to remove copper, selenium and tellurium is a must. Predecessors have been developed for craft to preprocessing,by adding soda to oxidation roasting-alkaline leaching to remove selenium-acid leaching to get rid of copper and tellurium achieved better effects. the acid leaching residue which come from the process of adding soda roasting, alkaline leaching, acid leaching analyzed by XRD in this thesis.and use the quantitative analysis of the gold and silver in acid leaching residue, then, leaching gold and silver by using the thiourea method, thiosulfate technology and iodine-iodide craft, the test results are as follows:Adopting thiourea leaching method deal with acid leaching residue to extract gold and silver, choosing the single factor experiment to optimize the leaching conditions, the optimum conditions of leaching:the ratio of liquid to solid50:1, sulfuric acid concentration0.4mol/L, Fe3+concentration3g/L, thiourea concentration19g/L, leaching temperature35℃, leaching time2h, the gold leaching rate can reach up to97.56%and the silver leaching rate can obtain89.08%, but the solution which is obtained after thiourea leaching is unstable, so dealing with the acid leaching residue by thiourea leaching method is not suitable for extracting Au, Ag.Employing iodine-iodide craft dispose to acid leaching residue, choosing the single factor experiment to optimize the leaching conditions, the optimum conditions of leaching: the ratio of liquid to solid30:1, the molar ratio of iodide ion and iodine n(I-):n(I2)=2:1, the initial concentration of iodine17.5g/L,leaching temperature25℃Reaching time1h. This optimum condition condition was testified by experiment, the average gold leaching rate can get to96.62%, while silver leaching rate only obtain below0.5%.leaching solution obtained in this way is sable, at the same time, gold leaching can achieve good results, but this way is not fit for leaching silver. Utilizing sodium thiosulfate conduct acid leaching residue, using orthogonal experiments, obtaining the primary and secondary factors order of silver leaching rate:Cu2+concentration>sodium thiosulfate concentration>ammonia concentration>leaching time, optimal conditions are sodium thiosulfate concentration0.18mol/L, Cu2+concentration0.015mol/L, ammonia concentration0.2mol/L, leaching time2h. Experiments found that the silver leaching rate is relatively high, meanwhile, the solution is stable, therefore sodium thiosulfate technology is suitable to leach silver contained in acid leaching residue. Collecting the first stage residue after iodine-iodide leaching and conduct second stage gold leaching, the conditions are the same to the first stage leaching by iodine-iodide reagents. This way can make the leaching rate of gold reach up to98.69%, while silver leaching rate is below0.5%. gathering the second stage residue leach silver experiments by sodium thiosulfate, the optimum conditions are as follows:sodium thiosulfate concentration0.18mol/L, Cu2+concentration0.015mol/L, ammonia concentration0.2mol/L, sodium thiosulfate0.4g/L leaching time1.5h. In this condition silver leaching rate can obtain97.97%.Leaching gold by two stage iodine-iodide method, then dissolving silver by sodium thiosulfate technology, not only gold and silver can reach up to high extraction rate but also gold and silver can separate very well.