Extraction Of Bismuth From Copper Converter Flue Dusts By Hydrometallurgical Process

In china, sixty percent of bismuth is extracted from the byproducts and intermediate products that produced in the smelting process of other metals (lead, copper, tin, etc.) productions. These kinds of bismuth resources including complex grade of valuable metal contents. One of these is white ash, namely the copper converter flue dust produced in the copper smelting method, which is also a kind of raw material containing bismuth. A variety of valuable heavy metals can be recovered by leaching from white ash, which makes it a valuable resource.In this paper, the recovery of bismuth from white ash offered by a copper metallurgy company was studied. In the mature industrial production, most of the valuable metals such as copper, cadmium, zinc, indium has been effectively recovered. However, the content of bismuth in the leaching residue remains as high as3%, which means a loss of high economic value if it is discharged without further treatment. At present, cycled economy and environmental protection are attracting increasing focus by industries and our country. From these aspects, research on recovery of bismuth from white ash still has vital significance. According to the characteristic of low bismuth content and high lead, copper, arsenic contents in the white ash, a hydrometallurgical process were employed for the extraction of bismuth from the copper converter flue dust.The leaching process of copper converter flue dusts was studied. Dilute sulfuric acid and H2SO4-NaCl solution was used as leaching agents for twice leaching process, and the operation conditions of the second leaching process were optimized. The results show that most solubility element such as Zn、Cd、Cu、Fe can be separated and Bi, Sb can be enriched by the first leaching, when the leaching agent was0.5mol·L-H2SO4. The optimized results show that a counter-current circulation leaching of the first leached residue under the conditions of60℃,2mol·L-1H2SO4,2.5mol·L-1NaCl, and the liquid-solid ratio2:1, is feasible. Under these conditions, an average extraction rate of95.08%can be obtained, when the leaching solution concentration of bismuth is16.00g·L-1.The separation process of bismuth from the leaching solution was studied. The lg[Bi3+]T-pH diagram of Bi(Ⅲ)-Cl-H2O system and1g[Sb3+]T-pH diagram of Bi(Ⅲ)-Cl-H2O system were characterized when [Cl-] was2.5mol·L-1. Analysis comes to a theoretical conclusion that bismuth can be separated from antimony by adjusting the pH value in the leaching solution. Ammonia (15%) was used as neutralizing agent, and the impact of pH value on precipitation rate of the five elements (Bi、 Sb、As、Pb、Cu) was examined respectively. The optimized results show that by adjusting pH value of leaching solution from0.5to3.0, over96%of bismuth can be recovered as rich bismuth precipitation, meanwhile, rich antimony precipitation is also obtained. Then thermodynamic analysis was carried out on the Bi-As-H2O system, and the ε-pH diagram under the standard conditions is drawn. The operation conditions of alkali leaching process were optimized. The results show that under the optimal condition of25℃,2mol·L-1NaOH, and the liquid-solid ratio5:1, is feasible, and the leaching rate of arsenic was97.05%, while bismuth was enriched to57.48%.12H2O·Na3AS04was recovered from alkali leaching solution, and with purity of79.18%antimony sponge was prepared from rich antimony precipitation.In the preparation of sponge bismuth from removing arsenic rich bismuth material by the process of "dissolve-replacement", the influence of preparation dosage of iron powder and replacement time on the bismuth recovery and the purity of sponge bismuth was examined. The results show that the replacement rate of bismuth was98.1%and the purity of obtained sponge bismuth reach up to90.55%under the optimal conditions of1.5times stoichiometric amount of iron powders and20min.With the sponge bismuth as a raw material, high-purity bismuth oxide, which meet the requirements of the electronics industry with bismuth oxide standard(SJ/T10678-1995), was prepared by twice " dissolve-replacement", three times of "dissolving-neutralizing hydrolysis", and calcinations at last.