Study on continuous crystallization and purification of bismuth from Pb-Bi alloy

Abstract

The crude bismuth obtained from the smelting of bismuth concentrate and bismuth-containing by-products contains 5%∼20% lead, which needs to be removed during the refining of crude bismuth. Due to the similar physical and chemical properties and metallurgical behavior of lead and bismuth, it is not easy to perform the separation by conventional methods. Although the conventional process of chlorinating crude bismuth to remove lead can meet the requirements of the refining process, the amount of chlorinated slag produced is large, and the safety of chlorine gas is difficult to control, making it difficult to achieve clean production. In this paper, single-factor experiments and semi-industrial experiments for the separation and purification of bismuth from Pb-Bi alloy were carried out by the continuous crystallization method, and the results showed that the bismuth content of Pb-Bi alloy increased from 90.24% to 98.98%, the direct yield of bismuth was 87.37%, the metal recovery rate was 99.84%, and the slag production rate was 0.62%. In comparison with existing processes and studies, the method is low-cost, clean, and efficient, has a wide treatment range, can be operated continuously, and can be easily industrialized and promoted. Theoretically, this method, combined with the process of vacuum distillation to treat Pb-Bi binary alloys with greater than 55.5% bismuth content, results in a 99.99% bismuth product.