Electrolytic Processing of Pb-Bi Alloy

Metal bismuth is mainly produced as a by-product in the production of lead, tungsten, copper, silver, gold, tin and zinc. Approximately 90 % of all extracted bismuth is obtained from lead, copper and other concentrates. The main source of bismuth is lead concentrates obtained during the processing of lead, as well as lead-zinc and other polymetallic ores. During the processing of these concentrates, bismuth almost completely enters the rough lead, from which it is removed during its refining. The most common technologies for the recovery of bismuth from lead ingots are the Kroll-Betterton process and the Betts electrolytic process. During the electrolysis of the Bi-Pb alloy, the separation of three products has been established, they are anode and cathode alloys, as well as salt melt. The complexity of pyroelectrometallurgical processing of a bismuth-poor alloy with the production of rough bismuth in one stage is confirmed, which necessitates the use of two stages of electrolysis. At the first stage of electrolysis, the anode product‑1 (17.3–48.5 % of the initial Pb-Bi alloy) of the composition has been isolated,%: 16.6–48.4 Bi; 51.4–83.2 Pb; operational extraction,%: 92.2–96.6 Bi; 9.8–44.4 Pb; main phases Bi0,3Pb0,7 and Bi0,95Pb0,05. A six-fold bismuth enrichment is achieved in the anode product. At the second stage of electrolysis of the previously isolated anode product of the composition,%: 26.7 Bi; 73.1 Pb; 0.13 Cu; 0.08 Zn, the anode product‑2 (28.1 % of the enriched Pb-Bi alloy) of the composition has been separated,%: 93.6 Bi; 4.1 Pb; 0.086 Ag; 0.0066 As; 0.006 Sb; 0.0013 Cu; 0.001 Sn; 0.0014 Zn; stage extraction,%: 98.6 Bi; 1.6 Pb; main phase Bi0,95Pb0,05. As a result of pyroelectrometallurgical processing of a Pb-Bi alloy (~10 % Bi) with anode polarization in two stages, an anode product (8.7 % of the initial alloy) of the composition has been isolated,%: ≥ 93.6 Bi; 4.1 Pb; extraction from the initial alloy,%: 93.0 Bi; 0.4 Pb has been obtained. The following modes are recommended for pyroelectrometallurgical processing in two stages of Pb-Bi alloy: process temperature 550–600 °C; anode current density: 0.5 A/cm2 at the first stage; 0.2–0.3 A/cm2 at the second stage; cathode current density: 1.5 A/cm2 at the first stage; 1.0 A/cm2 at the second stage; operating voltage on the tub: at the first stage 8–12 V; at the second stage 5–8 V; the composition of the electrolyte at both stages,%: 7 NaCl; 35 KCl; 18 PbCl2; 40 ZnCl2; the amount of electrolyte output for processing: at the first stage – 10 % of the mass of the Pb-Bi alloy after alkaline treatment; at the second stage – 10 % of the mass of the anode product of the first stage