Rates and products of arsenojarosite dis

Batch dissolution experiments were conducted on synthetic arsenojarosites at different pH levels and in ultra-pure water to investigate the effects of arsenic incorporation on the kinetics and reaction products of jarosite dissolution. The experiments revealed incongruent jarosite dissolution across all conditions. Notably, arsenojarosite exhibited a lack of pH dependency in contrast to K-jarosite dissolution, likely due to the formation of surface arsenate–iron complexes that hinder protonation at low pH and discourage hydroxyl repulsion at high pH. The stronger interaction between arsenate and iron, when compared to sulfate, results in a surface enriched with arsenate–iron complex sites, which inhibits dissolution over time. Secondary products arising from the dissolution process included maghemite, goethite, and hematite in ultra-pure water, while ferrihydrite formed in a pH 8 Tris buffered solution. Observations indicated that maghemite transforms into hematite over time in ultra-pure water, a transition that is slowed by increased arsenic concentrations. In open systems with a constant fresh solution influx, the incorporation of arsenic in jarosite enhances dissolution rates, whereas in closed systems, it hinders further dissolution, thereby decreasing the rates as arsenic content increases.