Removal of hexavalent chromium pollutant and mechanism by heat-treated natural pyrite as an efficiency reactive media for permeable reactive barrier

Chromium pollution in ground water is already very serious and needs to be solved urgently. In the present work, the products of natural pyrite after heat treatment were used as the reactive media for permeable reactive barrier. It found that natural pyrite can progressively convert to pyrrhotite with mixed monoclinic and hexagonal structures or pure hexagonal structure at different heat temperatures in argon atmosphere. The products heated at 600 °C had the highest removal of Cr 6+ as compared to pristine pyrite and other heated products. The column experiment showed the service life of the column was 480 PVs. The removal of Cr 6+ mechanisms under the batch and column conditions were also investigated in detail and both of them were redox reactions. The present work suggested that heat-treated natural pyrite has good application prospect as an efficient and low-cost reactive media material in permeable reactive barrier for chromium pollution control.