Evenly distribution of amorphous iron sulfides on reconstructed Mg-Al hydrotalcites for improving Cr(VI) removal efficiency

Hexavalent Chromium (Cr(VI)) in water is a public health concern and has been a challenging research subject in environmental field for many years. Herein, a novel composite material consisting of amorphous iron sulfides supported on hydrotalcites (FeS/HTs) was synthesized by "calcination-reconstruction-calcination" process, which enables homogeneous distribution of iron and sulfur on the surface of hydrotalcites (HT). The composite (mass ratio of FeS/HT was 1/2) could effectively remove over 98% of Cr(VI) within 10 min. A pseudo-second-order kinetic model and a Langmuir isotherm model were well fitted the sorption data with a maximum removal capacity of 206.2 mg/g. The superior adsorption capacity of FeS/HTs could be attributed to the combination of the advantages of abundant adsorption sites on HT and powerful reduction properties of iron sulfides. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis suggested the adsorbed Cr(VI) on the surface and interlayer of FeS/HTs had been reduced to Cr(III) by reductant iron and sulfur. This study demonstrated that FeS/HTs has potential application prospects in Cr(VI) removal.