Separation and purification of bismuth from bismuth-lead alloy based on methanesulfonic acid system

The traditional chloride-based treatment of bismuth-lead (Bi-Pb) alloys faces serious challenges, such as low separation efficiency of valuable metals and chlorine gas volatilization. To overcome these limitations, a novel process employing a methanesulfonic acid (MSA) system was developed for Bi extraction from lead smelting by-products. The process involves four main steps: pretreatment, oxidative leaching, purification, and electrowinning. During pretreatment, tellurium (Te) was selectively separated, producing Te-rich slag and water-quenched Bi-Pb alloy slag. Under optimal conditions, including a hydrogen peroxide dosage of 1.2 times the theoretical amount, a temperature of 50 °C, a liquid-solid ratio of 5:1, a reaction time of 2 h, and a MSA concentration of 4 mol/L, Bi and Pb were leached with leaching efficiencies of 96.6% and 98.3%, respectively. Thermodynamic and kinetic analyses confirmed the feasibility of oxidative dissolution and revealed different dissolution behaviors of Bi and Pb in the MSA-H₂O₂ system. To satisfy the impurity requirements for electrowinning, the leaching solution was purified using sulfuric acid and barium carbonate. A high-purity Bi cathode (99.98%) was obtained at a current density of 150 A/m² and a temperature of 35 °C, with a cathodic current efficiency of 97.6% and an electric energy consumption of 693.83 kWh/t. The proposed process demonstrates a promising and sustainable method for recovering Bi from secondary resources, with considerable potential for industrial application in green metallurgy.