Study On Removal Of Arsenic And Antimony From High Bismuth Lead Anode

High-bismuth lead anode slime is a byproduct from crude lead electrolytic refining process and contains a lot of valuable elements, such as Bi、As、Sb、Pb、Sn、Au、Ag and which is one of the important raw material of the bismuth production. Arsenic and arsenic compounds are harmful substances, which not only bring pollution to the environment, but also affect the quality and yield of other valuable metal. Antimony can affect the quality of cathode bismuth when extracting bismuth by electrolysis, because antimony is close to bismuth in electrode potential. In this paper, some new processes on arsenic and antimony removal for high-bismuth lead anode slime was proposed,which are roasting oxidation alkaline leaching on arsenic removal and alkaline pressure oxidative leaching process on arsenic and antimony removal. This lay the foundation for the enrichment and extract of bismuth and other precious metal.In this study, the raw material is high-bismuth lead anode slime and the bismuth content is over 45%, the Bi/As is 4.9 and the Bi/Sb is 4.3 respectively. Firstly, some explored experiments on arsenic removal for high-bismuth lead anode slime were conducted, include atmospheric pressure oxidative leaching solution and pre-oxidation leaching solution, the influences of the kinds of oxidizing and leaching agent and pre-oxidizing mode were studied and the technology of the roasting pre-oxidizing and alkaline leaching on arsenic removal were determined.Secondly, the effects of various paramenters,such as roasting temperature, ratio of liquid to solid, sodium carbonate dosage, oxidant dosage and the concentration of sodium in pre-roasting oxiding alkaline leaching of high-bismuth lead anode slime were studied and the optimum conditions were determined as follows:the roasting temperature is 400℃, the roasting time is 2h, the ratio of liquid to solid is 5:1, the sodium carbonate dosage is 15%, the concentration of sodium is 120g/L, the leaching temperature is 80℃ and the leaching time is 1h. Under this condition, the leaching ratio of arsenic is over 95% and a good effect on arsenic removal is obtained, but the leaching ratio of antimony is about 4% and the further study was needed.A treatment method on arsenic and antimony removal by one step was studied and the arsenic and antimony were removed from bismuth-rich lead anode slime by alkaline pressure oxidation leaching. The influence of those factors including oxidant dosage, NaOH concentration, ratio of liquid to solid, leaching temperature and leaching time on arsenic and antimony removal were investigated, and the optimal process conditions were determined by means of experiments and the optimum conditions were determined as follows:the oxidant dosage is 15%, the concentration of NaOH is 150g/L, the ratio of liquid to solid is 7:1, the leaching temperature is 180℃, the leaching time is 2h and the results show that the leaching rate of arsenic and antimony can reach 95.16% and 80.51% and Bi/As and Bi/Sb of the residue are 72 and 25 respectively, gold and silver content vary from 24,30 g/t and 3408 g/t to 38.20 g/t and 5878 g/t respectively.The alkaline leaching solution were purified by standing and cooling on arsenic removal and adding hydrogen peroxide solution to crystallization mother liquor on antimony removal and arsenic、antimony and lead were recycled in the form of NaAsO4、0H2O、NaSb(OH)6、Pb2Sb2O7 at last.The alkaline leaching solution is returned to leaching process after adding quantitative sodium hydroxide, which achieve the recycling of alkaline solution and the effective separation of arsenic and antimony from other metals. Based on the experiments, the expand experimentation were carried out, the repetition of experiment is good and the slag ratio, leaching ratio, purification effect of alkaline leaching liquid and the cyclic utilization rate were stability and reliability.