Microbial reductive dissolution of schwertmannite leading to antimony release

Schwertmannite, an iron hydroxysulfate mineral, significantly influences the mobility of antimony. While schwertmannite can effectively sequester antimony through adsorption or coprecipitation, the subsequent release of antimony from schwertmannite via microbial activities remains poorly understood. This study revealed that up to 40% of the Sb(V) coprecipitated by schwertmannite can be released by the iron-reducing bacterium Shewanella piezotolerans WP3 through dissimilatory iron reduction, Over 50% of crystalline Fe(III) in schwertmannite was reduced by WP3, facilitating the dissolution of schwertmannite and the release of Sb(V), accompanied by partial Sb(V) reduction to mobile Sb(III) (3.10–3.34% of total Sb). Vivianite emerged as the predominant secondary mineral in the presence of WP3 as confirmed by XRD spectra. In contrast, under the pH around 6.8 (mimicking the circumneutral condition during antimony remediation) in abiotic control, Sb(V)-loaded schwertmannite remanded relatively stable with 2.13–3.04% Sb(V) released. These findings underscore the critical role of microbial Fe(III) reduction in mobilizing antimony from Sb-bearing minerals, thereby highlighting potential contamination risks associated with microbial activity.