Mechanisms of arsenite (As(III)) fixation regulated by jarosite biomineralization induced by Acidithiobacillus ferrooxidans

Jarosite, a common mineral in acid mine drainage (AMD), influences arsenic mobility, yet its role in arsenite (As(III)) transport remains unclear. This study investigated biogenic jarosite formation and intermediate-phase transformation in an Fe(II)-As(III)-SO₄²⁻ environment using Acidithiobacillus ferrooxidans (Fe(II), 8.96 g·L⁻¹; As(III), 10 − 200 mg · L⁻¹). The results show that bacteria first facilitated the crystallization of an As-rich schwertmannite precursor by oxidizing Fe(II) to Fe(III), and then drove its transformation into jarosite as pH declined. Combined analysis of XRD, FTIR, SEM, and elemental composition showed that Fe(III) and As(III) coprecipitated into biogenic jarosite with substituted arsenic. After 72 hours, the highest arsenic removal efficiency, about 62%, was achieved at initial pH 3.0. XPS analysis of the intermediate precipitate detected only As(III) on the schwertmannite surface. A two-step mechanism governed the process: initial As-rich schwertmannite formation (pH > 2.5) enabled high arsenic uptake, followed by its conversion to jarosite, enhancing As(III) stability. Regulation of pH and competing anions (e. g., phosphate, nitrate) is essential to optimize sequestration and stability during mineral transformation.