The weathering of arsenopyrite is closely related to the generation of acid mine drainage (AMD) and arsenic (As) pollution. Solar radiation can accelerate arsenopyrite oxidation, but little is known about the further effect of SO₄²⁻ on the photochemical process. Here, the photooxidation of arsenopyrite was investigated in the presence of SO₄²⁻ in simulated AMD environments, and the effects of SO₄²⁻ concentration, pH and dissolved oxygen on arsenopyrite oxidation were studied as well. SO₄²⁻ could accelerate the photooxidation of arsenopyrite and As(III) through complexation between nascent schwertmannite and As(III). Fe(II) released from arsenopyrite was oxidized to form schwertmannite in the presence of SO₄^2–, and the photooxidation of arsenopyrite occurred through the ligand-to-metal charge-transfer process in schwertmannite–As(III) complex along with the formation of reactive oxygen species in the presence of O₂. The photooxidation rate of arsenopyrite first rose and then fell with increasing SO₄²⁻ concentration. In the pH range of 2.0–4.0, the photooxidation rate of arsenopyrite progressively increased in the presence of SO₄²⁻. This study reveals how SO₄²⁻ promotes the photooxidation of arsenopyrite and As release in the AMD environment, and improves the understanding of the transformation and migration of As in mining areas.

毒砂的风化与酸性矿山排水（AMD）和砷（As）污染的产生密切相关。_{太阳辐射可以加速毒砂氧化，但对于 SO 4} ^2-对光化学过程的进一步影响知之甚少。在这里，在模拟 AMD 环境中研究了在 SO ₄ ^2-存在下毒砂的光氧化，并研究了 SO ₄ ^2-浓度、pH 和溶解氧对毒砂氧化的影响。SO ₄ ²⁻可以通过新生施韦特曼石和 As(III) 之间的络合来加速毒砂和 As(III) 的光氧化。_{毒砂释放的 Fe(II) 在 SO 4} ^2-存在下被氧化生成施韦特曼石，毒砂通过施韦特曼石-As(III) 络合物中的配体-金属电荷转移过程发生光氧化，同时形成在 O ₂存在下的活性氧。随着SO ₄ ^2-浓度的增加，毒砂的光氧化速率先上升后下降。在 2.0-4.0 的 pH 值范围内，毒砂的光氧化速率在 SO ₄ ^2-存在下逐渐增加。本研究揭示了 SO ₄²⁻促进毒砂光氧化和在 AMD 环境中释放砷，提高对矿区砷转化和迁移的认识。