Energy-Efficient and Green Extraction of Bismuth Metal in Methanesulfonic Acid-Based Membrane Electrochemical Systems

As the mainstream hydrometallurgical medium of bismuth sulfide concentrate, chloride/hydrochloric acid suffers from high volatility, strong corrosiveness, and inferior deposit quality. In this paper, methanesulfonic acid (MSA) with low volatility and high stability was adopted as the bismuth hydro-metallurgical system, and the membrane electrochemical deposi-tion method was proposed to extract bismuth metal from a bismuth-containing solution. The effects of additives, such as calcium lignosulfonate (CL), tetrabutylammonium chloride, beta-naphthol, and lugalvan NES, on the morphology of bismuth deposits and electric energy consumption (EEC) were investigated in detail. The addition of CL as an additive could produce dense and flat bismuth deposits while the EEC is reduced simultaneously. Cyclic voltammetry and chronoamperometry analysis reveal the electrochemical behavior of bismuth deposition in the CL-assisted MSA medium, and the nucleation and growth of bismuth grains follow a 3D "nucleation/growth" mechanism. Under a cathode current density of 180 A/m(2), a flat metallic bismuth deposit (purity > 99.96%) is produced in the presence of 0.5 g/L CL. The cathodic current efficiency (CCE) and EEC of membrane electrodeposition are 98.25% and 705 kWh/t Bi, respectively. Compared with chloride/hydrochloric acid, the bismuth membrane electrodeposition process in the CL-assisted MSA system has the advantages of being energy-saving, green, and safe, and it has a good application prospect in the field of bismuth hydrometallurgy.