Biogenic iron mineral formation and the fate of arsenic driven by its coupling with ferrous iron in acid mine drainage environment

Acid mine drainage (AMD) containing arsenic produced during coal mining is a global environmental problem. However, the coupled driving process of the key element Fe and the associated element As in the AMD environment has received little attention. Therefore, in this study, we investigated the A. ferrooxidans-mediated ferrous iron–arsenic interaction in a simulated AMD system. We reveal that in As-rich AMD the co-existing element As can regulate the metabolic activity of A. ferrooxidans to accelerate the oxidation of Fe²⁺ and the subsequent formation of Fe³⁺ minerals, thereby altering the pH and ORP of the system. XRD, SEM, and XPS analyses showed that the synthesized Fe mineral mainly consisted of As-containing schwertmannite (Sch). As in an AMD system could be efficiently removed (98.7% after 72 h) through the formation of Fe minerals, thereby reducing its own environmental risk. SO₄^2- plays an important role in As precipitation on the surface and in crystal tunnels of Sch. As-containing Sch is not only beneficial for the precipitation of As, but also for long-term reduction in As toxicity in AMD systems. Our results provide new insight for evaluating the fates of Fe and As, and the environmental and ecological risks of As in AMD produced from natural coal mines.