Enhanced performance for total Cr removal using a novel h-BN supported nanoscale iron sulfide composite: stabilization effects and removal mechanism

In this study, a novel nanocomposite (FeS@h-BN) that FeS nanoparticles anchored onto h-BN nanosheets was synthesized for chromium (Cr(VI)) removal in aqueous solutions and characterized by SEM, TEM, XRD, FTIR, Zeta, and XPS. The effect of removal parameters including initial pH, temperature, FeS@h-BN dosage, the initial concentration of Cr(VI) and contact time were investigated. Experiment results revealed that h-BN as a stabilizer for FeS had good stability and effectively reduced FeS agglomeration. The remarkable performance of removing total Cr in aqueous solution was obtained by effectively converting Cr(VI) to Cr(III) on FeS and simultaneously adsorbing Cr(III) on h-BN. The adsorption capacity of FeS@h-BN for Cr(VI) was extremely sensitive to the pH and the optimum adsorption was 399.72 mg/g at pH of 1.0. In addition, the efficiency of removing Cr(VI) by FeS@hBN increased with the increase of adsorbent dosage and Cr(VI) concentration, and the efficiency reached 100% at an adsorbent dosage of 0.30 g/L. The pseudo-second-order kinetic model can fully explain the experimental rate data. The mechanism of FeS@h-BN to remove Cr(VI) was adsorption and chemical reduction, of which chemical adsorption was the main one. These results revealed that h-BN as a stabilizer can improve the FeS stability and reactivity for the rapid removal of Cr(VI) contamination in water solution.