Sorption of arsenic onto Vindhyan shales: Role of pyrite and organic carbon

Abstract

Batch isotherms: for arsenic sorption on Vindhyan shales were compared with arsenic sorption on black cotton soil. High sorption was observed on pyrite-rich shales and the Freundlich capacity constant K-F yielded a good correlation with sediment pyrite content. Shales with high organic carbon sorbed more arsenic; however, the organic carbon-rich soil demonstrated significantly lower sorption. This difference may be due to the condensed nature of organic carbon in shale, which may have facilitated formation of organo-arsenic complexes. The pyrite content was also strongly correlated with the organic carbon content, possibly due to microbial synthesis during shale diagenesis.