Biogenic iron mineralization of polyferric sulfate by dissimilatory iron reducing bacteria: Effects of medium composition and electric field stimulation

Polyferric sulfate (PFS) is a coagulant widely used for removing contaminants from the aqueous phase: however, PFS destabilizes and recrystallizes in the solid phase in the presence of dissimilatory iron reducing bacteria (DIRB), which has a profound influence on the cyde of Fe and the fate of the associated pollutants. Our objective is to investigate the combined effects of medium composition and electric field stimulation on the biomineralization of PFS. Batch experiments were conducted with PFS and the DIRB Shewartella oneidensis MR-1 under anoxic conditions to examine the microbial reduction of PFS to Fe(II) and its subsequent biotransformation. The high concentration of phosphorous in phosphate buffer solution (PBS) is responsible for slower and less extensive Fe(11) generation compared to the lower concentration of phosphorous in a medium of 1,4-piperazinediethanesulfonic acid (PIPES). The PBS system induces the formation of green rust (SO42-) and vivianite as the major minerals; in contrast, magnetite is the predominant end product in the PIPES system. The application of an anodic potential of 0.2 V significantly stimulates Fe(II) release from PFS, leading to precipitation and transformation of more crystalline minerals in increased quantities. The results demonstrate that Fe (II) catalyzes biomineralization of PFS to a variety of secondary products; this electron transfer process is highly dependent on the rate and magnitude of PFS reduction and the surface reaction with the host compound and adsorbed ions. (C) 2019 Published by Elsevier B.V.