Effect of goethite on pyrite biooxidation and its environmental implications

• Goethite promoted pyrite biooxidation by A. ferrooxidans . • The synergistic effect of goethite and A. ferrooxidans enhanced the Fe 2+ /Fe 3+ cycling. • Goethite altered the surface wettability and electrochemical reactivity of pyrite. Acid mine drainage (AMD) is mainly caused by the dissolution of sulfide minerals, with pyrite being one of the primary contributors. During AMD evolution, secondary iron minerals such as goethite are commonly formed and may influence subsequent pyrite oxidation; however, their roles and underlying mechanisms remain unclear. In this study, the effect of goethite on pyrite biooxidation by Acidithiobacillus ferrooxidans was systematically investigated through bioleaching experiments combined with surface characterization and electrochemical analyses. The results showed that goethite significantly enhanced pyrite biooxidation, increasing iron extraction from 11.81% to 29.86% at a goethite dosage of 0.2 g. Surface analyses revealed that goethite promoted the oxidation of Fe-S species and the formation of iron oxyhydroxide/oxide products, and altered the surface wettability of pyrite residues, thereby facilitating surface reactions. Electrochemical results further indicated that goethite enhanced electron-transfer activity and accelerated pyrite oxidation kinetics. The catalytic effect was attributed to the synergistic interaction between goethite and Acidithiobacillus ferrooxidans , which promoted Fe 2+ /Fe 3+ cycling and strengthened the oxidation of pyrite. This study highlights the active role of secondary iron minerals in regulating sulfide mineral oxidation and provides new insights into AMD evolution and bioleaching optimization.