Arsenic sequestration by metallic iron under strongly reducing conditions

摘要

The objective of this study was to elucidate the mechanism of arsenic sequestration by metallic iron in strongly reducing conditions. Contacting arsenic with metallic iron in anaerobic batch systems showed considerable reduction in dissolved arsenic concentration. Scanning electron micrographs of the metallic iron surface after contact with arsenic showed evidence of surface depositions. X-ray diffraction patterns of such surfaces showed evidence for the presence of iron arsenide (FeAs and FeAs2) phases, and arsenopyrite (FeAsS) and oripment (As2S3) phases respectively, in the absence and presence of dissolved sulphate. Theoretical chemical speciation studies supported the above experimental results. It was thus concluded that strong reducing conditions produced in the vicinity of the anaerobically corroding metallic iron surface result in arsenic sequestration.