Removal of arsenic from smelting wastewater using Fe3O4as an in situFe source: the effect of pre-dissolution and the evolution process of scoroditeElectronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d2ew00333c

Arsenic (As) pollution is a serious worldwide problem that requires urgent attention, as this heavy metal poses a serious threat to both human and environmental health. Here, Fe3O4was used as an in situFe source removal agent to study the effect of pre-dissolution time on arsenic removal by Fe3O4. Fe3O4is uniquely well suited for the treatment of industrial wastewater due to its structural characteristics. Assays were conducted at a Fe/As molar ratio of 3 : 1, and these components were pre-dissolved at 23 °C for 2 h to establish the optimal initial conditions for Fe-mediated arsenic removal at a high temperature. The adsorption capacity of arsenic in the pre-dissolution stage was 143.99 mg g−1. After adjusting the pH value to 2.5 and allowing the Fe and As to react at 90 °C for 24 h, 99.1% of the As was precipitated from the wastewater with an initial arsenic concentration of 8276.1 mg L−1. The leaching of this As-bearing precipitate was as low as 0.3 mg L−1. As a solid iron source, Fe3O4provides a large number of nuclear sites for arsenic precipitation in the pre-dissolution stage and the high-temperature synthesis stage. At the same time, the supersaturation of the system was regulated by controlling the reaction and dissolution characteristics. Upon further characterization, the removal of As by Fe3O4in the pre-dissolution process was attributed to a combination of physical adsorption and chemical precipitation.