Efficient removal of arsenic from copper smelting wastewater in form of scorodite using copper slag

Copper smelting wastewater, one of the typical high arsenic-containing acidic wastewater in the metallurgical extraction process of arsenic-associated minerals, greatly threatens human health and ecological safety due to the possible leakage and diffusion from its secondary pollution. However, the state-of-the-art technologies suffer from the great challenge that the disposal of wastewater emits an enormous amount of arsenic-containing hazardous wastes with the poor long-term stability and the high arsenic leachability. Herein, a novel strategy is proposed to remove and stabilize arsenic from copper smelting wastewater in the form of environmental friendly scorodite using copper slag as a neutralizer and an in situ iron donator. The thermodynamic analysis and the bath experiments were investigated to explore the reaction behavior between wastewater and copper slag. The result shows that 97.86% of arsenic was successfully removed from wastewater with an initial arsenic concentration of 10230 g/L at by using copper slag at an Fe/As molar ratio of 2.0 and 80 °C for 12 h, resulting in a scorodite-SiO2-sulfate composite with an arsenic leached concentration of 3 mg/L in the leaching test. The main phases of Fe2SiO4 and Fe3O4 from copper slag dissolve in wastewater and release abundant Fe ions to synthesize scorodite and secondary minerals (silica gel and sulfate complexes). The initial precipitates from the second minerals are likely to serve as nucleation sites for the formation and growth of scorodite. We demonstrate an inherent arsenic disposal process for the copper smelting industries, and the process allows the removal and stabilization of arsenic from wastewater using solid waste. It might provide an efficient and low-cost solution for the disposal of arsenic-containing wastewater in the nonferrous smelting industry. [Display omitted] •Arsenic removal from wastewater using copper slag for scorodite synthesis.•Dissolution of copper slag and arsenic precipitation drive scorodite growth.•Transformation of fayalite into scorodite-SiO2-sulfate composite in wastewater.•Inherent disposal of arsenic-bearing wastewater in copper smelting plant.