The influence mechanism of pyrite on the biodissolution of stibnite under light/darkness conditions.

Stibnite (Sb2S3) dissolution is an important pathway for antimony release in mining environments. This study investigated how pyrite (FeS2), acidophilic microorganisms, and light affect stibnite (Sb2S3) biodissolution. A 42-day 2 × 2 × 2 factorial experiment was conducted by varying the mineral composition, light conditions, and microbial presence. Solution chemistry, mineral surface composition, microbial community structure, electrochemical behavior, and hydroxyl radical (·OH) signals were analyzed. The results showed that pyrite was the dominant factor controlling stibnite biodissolution. Electrochemical analyses confirmed galvanic coupling between pyrite and stibnite, with pyrite acting as the cathode and stibnite acting as the anode, thereby promoting anodic dissolution of stibnite. Under biotic conditions, pyrite-derived Fe and S species sustained microbial Fe/S cycling and Fe3+ regeneration, maintaining an oxidizing environment that supported continued stibnite dissolution. XPS analysis showed that the relative proportion of surface sulfate increased from 29.80% in the dark to 63.89% under light, whereas residual sulfide decreased from 50.33 to 15.55%. Overall, pyrite-stibnite galvanic coupling was the primary electrochemical process driving stibnite biodissolution, whereas microbial Fe/S cycling maintained favorable oxidizing conditions. Light mainly affected interfacial electron transfer, accompanied by stronger ·OH signals and greater surface oxidation in the pyrite-bearing biotic system.