Study on the sulfidation kinetics of copper smelting waste acid and electrolytic refining purification solution for efficient Cu/As separation

The sulfidation is widely adopted for treatment of arsenic-contained solution. Within the copper smelting industry, multivalent arsenic hazards primarily arise from copper smelting waste acid (CSWA) and electrolytic refining purification solution (ERPS), also containing valuable copper resources. Due to the diversified competitive sulfidations of multivalent arsenic, the conventional mixed treatment process of Cu(Ⅱ)-As(Ⅲ) and Cu(Ⅱ)-As(Ⅴ) solutions is difficult to achieve efficient copper recovery and arsenic removal. According to Avrami kinetics, the sulfidation reaction rates for Cu(Ⅱ), As(Ⅲ), and As(Ⅴ) are 35.0339 M −1  s −1 , 34.7333 M −1  s −1 , and 0.05551 M −1  s −1 , respectively. Thus, Cu/As separation causes 72.02% arsenic content in the Cu(Ⅱ)-As(Ⅲ) sulfide precipitates, and less than 6.45% arsenic content in the Cu(Ⅱ)-As(Ⅴ) sulfide precipitates. Interestingly, the rapid nucleation of As(Ⅲ) sulfide provides a heterogeneous nucleation and secondary growth platform for As(Ⅴ) sulfide, facilitating rapid settling of As(Ⅲ)-As(Ⅴ) sulfide. Therefore, based on the difference in sulfidation rates, a novel process for Cu/As separation in CSWA and ERPS is proposed, involving copper split recovery and arsenic mixed removal. Value assessment of this process suggests that arsenic reuse can be diminished by approximately 645 tons annually through copper split recovery, and the particle size of As(Ⅲ)-As(Ⅴ) sulfide increases at least 44.3% via arsenic mixed removal. This study improves the sulfidation process of Cu/As separation in the copper smelting industry, which is significant for environmental protection and resource recovery.