Efficient recovery of copper resources from copper smelting waste acid based on Cu(Ⅱ)/As(Ⅲ) competitive sulfuration mechanism

Currently, domestic and foreign copper smelting waste acid mainly employ sulfuration method to realize the separation of Cu(Ⅱ) and As(Ⅲ), facing the problem of unreasonable sulfidizing agent dosage and sulfidation time. If excessive sulfidizing agent dosage or overly long sulfidation time, it will lead to human health threat and large hazardous waste volume. If insufficient sulfidizing agent dosage or overly short sulfidation time, it will cause the waste of copper resources and substandard treatment solution.In this paper, the competitive sulfuration mechanism of Cu(Ⅱ)/As(Ⅲ) solution (C(As(Ⅲ)) = 10 g/L) with different Cu(Ⅱ) concentrations is revealed, i.e., when C(Cu(Ⅱ))≥7 g/L, the sulfidation sequence of Cu(Ⅱ) and As(Ⅲ) follows the solubility product constant (Ksp); when C(Cu(Ⅱ))≤6 g/L, the precipitation process of Cu(Ⅱ)/As(Ⅲ) is dominated by the liquid-phase mass-transfer mechanism (ion diffusion). The sulfide precipitation of Cu(Ⅱ)/As(Ⅲ) is a co-deposition process. With the increase of sulfidizing agent dosage (S/Cu ratio) and sulfidation time (t), the Cu(Ⅱ) concentration gradually decreases to reach complete removal, while the further increase of S/Cu ratio and t leads to the decrease of copper content in the sulfide precipitates. Finally, the methods are demonstrated that detected accurately Cu(Ⅱ) and As(Ⅲ) concentrations in a rapid and non-destructive manner. This work not only provides a novel perspective on the efficient separation of Cu(Ⅱ)/As(Ⅲ) in copper smelting waste acid, but also opens a unique approach for direct and rapid detection of Cu(Ⅱ)/As(Ⅲ) concentration during the sulfuration process. Hence, this research is a guide for the regulating means (S/Cu and t) in the actual multi-step sulfuration process of copper smelting waste acid treatment and electrorefining solution purification.