Extracellular polymeric substances altered ferrihydrite (trans)formation and induced arsenic mobilization

The behavior of As is closely related to trans(formation) of ferrihydrite, which often coprecipitates with extracellular polymeric substances (EPS), forming EPS-mineral aggregates in natural environments. While the effect of EPS on ferrihydrite properity, mineralogy reductive transformation, and associated As fate in sulfate-reducing bacteria (SRB)-rich environments remains unclear. In this research, ferrihydrite-EPS aggregates were synthesized and batch experiments combined with spectroscopic, microscopic, and geochemical analyses were conducted to address these knowledge gaps. Results indicated that EPS blocked micropores in ferrihydrite, and altered mineral surface area and susceptibility. Although EPS enhanced Fe(III) reduction, it retarded ferrihydrite transformation to magnetite by inhibiting Fe atom exchange in systems with low SO