Efficient Electrolytic Refining of Crude Solder Assisted by Additives in a Fluosilicic Acid System
Yuantao Yang1,2, Zhaoyi Wang1,2, Xuanbing Wang1,2
1State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, China.
Abstract:
Current electrolytic refining processes for crude solder commonly employ fluosilicic acid (H2SiF6) as the electrolyte with bone glue and β-naphthol additives yet suffer from poor electrolyte stability, coarse cathode crystallization, low current efficiency, and high energy consumption, adversely affecting product quality and economic viability. In order to solve these limitations, electrochemical techniques, XRD, SEM, and ICP-OES were used to study the effects of gelatin and sodium lignosulfonate on the deposition overpotential and cathode morphology, as well as the effects of process parameters on current efficiency and energy consumption. A novel approach was developed using an H2SiF6 system enhanced by gelatin and sodium lignosulfonate for crude solder refining. After optimization, 120 h electrolysis achieved a current efficiency >97.8%, smooth/dense cathode surface, average cell voltage of 0.24 V, and energy consumption of 98.15 kWh/t. Efficient deposition of 81.2% Sn and 75.2% Pb on the cathode was realized, while >93.3% of Sb, Bi, Ag, Cu, and As were enriched in anode slime to facilitate valuable metal recovery, and >90.6% of In/Al concentrated in the electrolyte enabled effective Sn-Pb impurity separation. This study provides theoretical and technical foundations for advancing sustainable and economical electrolytic refining of crude solder.
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