Evaluation of soluble and insoluble xanthate process for the removal of heavy metals from wastewaters

Abstract

The effectiveness of xanthate (water soluble and water insoluble) process for hexavalent chromium removal has been evaluated. Insoluble xanthates were synthesized in the laboratory from corn starch (ICSX), potato starch (IPSX) and cellulose powder (ICX), and their removal efficiency for Cr(VI) is compared with soluble starch xanthate (SSX). In preliminary experiments various insoluble xanthates were tested for their effectiveness in removal of both metallic cation [Cd(II)] and metallic anion (chromate). The results indicated that the metal binding capacity followed the sequence q e( ICSX) > q e( IPSX) ⋍ q e( ICX) . Comparison between ICSX and SSX revealed that ICSX has better removal capacity for Cr(VI) on unit weight basis. However, based on chemical requirements for the synthesis of ICSX and SSX, SSX appears to be better than ICSX. The removal of Cr(VI) decreased with increase in pH while ionic composition of the aqueous phase had little effect on the removal for both soluble and insoluble xanthates. The removal mechanism for Cr(VI) appears to be reduction and complexation of the reduced chromium with xanthate groups. A comparative analysis of the traditional reduction-precipitation process and xanthate process for hypothetical waste containing hexavalent chromium revealed that xanthate process would be a worthwhile alternative.