Technology For High Bismuth And Lead Anode Slime Electrolysis Recovered Bismuth

Lead Anode is a byproduct of lead smelting process which is one of the important raw material of the bismuth production. The extraction of bismuth and enrichment of other valuable metals such as gold and silver elements from lead anode slime that was important to improve the comprehensive utilization of metallurgical secondary resources. In this paper, the new process of high-bismuth lead anode slime was proposed. The main steps were that removing arsenic firstly, then the lead anode slime of arsenic removal was cast into the crude bismuth which as anode on electrolyte system. The effective separation of bismuth with other impurities and the enrichment of gold and silver were realized by this treatment of lead anode.In this paper high-bismuth lead anode slime of arsenic removal was used. Firstly, the process of the lead anode slime of arsenic removal casted into anode plate was studied, the influences of melting temperature, added amount of sodium tetraborate, added amount of toner and melting time on fusion casting process were discussed. In addition, the process of removing antimony by oxide was explored. Purity of the crude bismuth alloy anode, rate of recovering bismuth and rate of removing antimony were analysed. The optimum conditions of anode slime smelting reduction were determined as follows: temperature of750-850℃, added amount of sodium of material weight was15%, added amount of toner of material weight was5%, the reduction time of1h. Under the optimum conditions, purity of the crude bismuth alloy anode reached about80%and rate of recovering bismuth reached above99%. During the process of oxidation and removing antimony, oxidation refining temperature was700℃, refining time was2h, antimony content from6.20%down to0.54%, antimony removal rate reached91.64%, bismuth loss rate lower than0.5%.In the process of electrolysis, the influences of temperature, current density, acidity, Bi3+concentration, the addition level of NaCl on the electrolysis process were discussed. The results showed that composition of crude bismuth anode had an important influence to the process of electrolysis. The anode passivation which caused by elevated levels of antimony was solved effectively by increasing the acidity of the electrolyte solution. antimony content of crude bismuth anode plate was controlled under5.50%can meet the requirement of electrolysis. The optimum conditions of the electrolysis were determined as follows:temperature of30℃, current density of150A/m2, acidity of80g/L, Bi3+concentration of120g/L, the addition level of NaCl of80g/L. Under the optimum conditions, electrolytic24h,48h,72h, respectively, current efficiency reached above98%, purity of bismuth cathode reached99%, and silver and gold of anode mud enriched about5-fold. As the extension of electrolysis time, the current efficiency is reduced, power consumption increased to a certain extent, but the magnitude is not large, purity of bismuth cathode dropped slightly.Above experiments show that:using the new process of removing arsenic-cast anode plate-electrolytic to treat high-bismuth lead anode slime was feasible.