Ferrous sulfide supported on modified diatomite for the removal of Cr(VI): Performance and mechanism

How to remove hexavalent chromium (Cr(VI)) from aqueous solution has always been a challenging problem in the environmental field. In this study, a novel composite of oxalic acid modified diatomite (DT) supported ferrous sulfide (FeS) was prepared by hydrothermal synthesis. The experiment results showed that the oxalic acid modified diatomite retained its original porous structure and possessed rougher surface, which could be used as a good loading/dispersing material to provide more adsorption sites. The composite material FeS/DT (the mass ratio of ferrous sulfide to modified diatomite is 1:1) can reduce more than 99 % of Cr(VI) to Cr(III) within 20 min, and Cr(III) can be adsorbed to the surface of diatomite. FeS/DT had a good adsorption and reduction effect at initial pH 3.0–9.0. The experimental results were in agreement with pseudo-second-order kinetic model and Langmuir isotherm adsorption model. Maximum adsorption capacity of FeS/DT for Cr(VI) can reach 141.6 mg/g. The reasons for the excellent reduction and adsorption ability of the FeS/DT were the reducibility of ferrous sulfide and porous structure of modified DT. This study revealed the reaction mechanisms of FeS/DT with Cr(VI), and demonstrated the feasibility of FeS/DT in the removal of Cr(VI) from water environment.