Reduction Remediation Of Hexavalent Chromium By Pyrite And Limonite In The Aqueous Phase

Hexavalent chromium (Cr(VI)) has wide spread, long-term use in industry for its ability to inhibit the formation of rust. Cr(VI) is a known human carcinogen. The aim of this research was to use pyrite (FeS₂) and limonite (FeO(OH).nH₂O) particles for reduction remediation of Cr(VI) in the water. The main objective of this work was to investigate the reaction mechanisms by emphasizing the role of ferrous Fe(II).The results of groping experiments are as following:1. The effect factors of Cr(VI) removal contain ironstone addition, initial Cr(VI) concentration, pH, temperature and the size of ironstone particles. The removal efficiency increased with the increasing of ironstone addition, reduced with the increasing of initial Cr(VI) concentration. low pH value could accelerate the rate of Cr(VI) removal. The smaller the ironstone particles, the higher the surface area, the faster the reaction rate. The rate of chromium reduction by pyrite increased with increased temperature and no temperature dependence in the reduction of Cr (VI) by limonite.2. The reduction capacity of pyrite (D<100mesh) was found to be 1.53 mgCr(VI)/g, and the reduction of capacity of limonite (D<100mesh) was found to be 7.77mgCr(VI)/g.3. The surface morphology of pyrite was characterized by some cracks and the surface of limonite is rough before the reaction, but after the reaction, the surface of two ironstone deposit was smooth uniform coating. The removal efficiency of ironstone reduced due to the precipitation, from which we can know that the reaction take place in the surface of the ironstone.4. The results show that pyrite reduction capacity finishes for approximately seven steps and the reduction capacity of limonite finishes for approximately ten steps.This study has shown that the use of pyrite (FeS₂) and limonite (FeO(OH).nH₂O) for the removal of Cr(VI) through reduction reaction is applicable to Cr(VI) contaminated solutions. The rapid reduction of Cr(VI) suggests that abiotic reduction of Cr(VI) may be an important transformation process in natural systems and engineered remediation technologies based on iron metal. The chemical reduction of Cr(VI) to Cr(III) by pyrite(FeS2) and limonite (FeO(OH).nH₂O) may provide a less costly approach remediation.