Bioremoval of antimony from contaminated waters by a mixed batch culture of sulfate-reducing bacteria

Abstract

Bioremediation of metal(loid)-contaminated water could be a cost-effective process. In this work, Sb-polluted water was treated by application of a mixed batch culture of sulfate-reducing bacteria (SRB). Aqueous Sb could be efficiently removed by the SRB over an initial pH range 5–8. The SRB was tolerant of at least 50 mg L−1 Sb in solution. With an initial pentavalent Sb (Sb(V)) concentration of 5 mg L−1, batch kinetic variations of the treatment were studied over a 11 d period at an initial pH 7 at 30 °C. A high removal (93%) of the aqueous Sb was achieved. The final products were identified microscopically. Before removal of Sb from solution in this treatment, Sb(V) was first reduced to trivalent Sb (Sb(III)). Hydrogen sulfide was proven to be the reducing agent in this reaction. The SRB were not able to reduce Sb(V) enzymatically. Following the chemical reduction of Sb(V) to Sb(III), the latter reacted with excess sulfide, resulting in the formation of insoluble antimony sulfide (Sb2S3). Studies on the sorption of Sb species by dead SRB indicated that, in the batch treatment, sorption by bacteria made a relatively small contribution to the removal of Sb.