Mechanochemical dolomite accurately modulating the activity of newly formed Fe-hydroxide for superior and stable arsenic removal

Arsenic (As) contamination in industrial wastewater on a large scale has posed a enormous threat to ecological security in recent decades. However, a key challenge at present is the efficient and cost-effective removal of As contamination, as Fe in the As removal process cannot quickly and stably form an active phase with high activity for arsenic removal. Here, we propose a strategy to use mechanical activation of dolomite to regulate the formation of newly formed Fe-hydroxide from Fe(II) with high arsenic-removal activity, while stably regulating the pH of water in the near-neutral range, thereby substantially improving the removal efficiency as well as the stability of Fe(II) for As. Activated dolomite can significantly enhance the oxidation rate of Fe(II) in water, and synergistically remove As contamination over 99.5 % of water with an initial concentration of 50 mg/L within 2 h, far superior to the performance of single Fe(II) or dolomite&Fe(II). The simulation and characterisation results reveal that in the presence of activated dolomite, the solution pH as well as the oxidation rate of Fe(II) are effectively regulated, which promotes the As in the solution to be significantly immobilised on the surface of activated dolomite as a ternary precipitate of Ca/Mg-Fe-As, conducive to the stability of the enhanced As removal precipitation. This study provides new insights into the role of carbonate mineral materials in As transformation, which is important for the efficient and cost-effective purification of As contamination in water.