Scavenging of Cr(VI) from aqueous solutions by sulfide-modified nanoscale zero-valent iron supported by biochar

Abstract

Abstract Nano scale zerovalent iron (nZVI) used in waste water treatment can be more effective when modified with sulfur. In this study, we synthesized biochar-supported sulfide-modified nZVI (S-nZVI/BC) and characterized it using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. Our results reveal that sulfidation resulted in the formation of FeS on the surface of S-nZVI/BC. The Cr(VI) removal efficiency and capacity of the above composite were investigated as a function of initial solution pH/Cr(VI) concentration, reaction time, and presence of background ions (Ca2+and SO42–). Batch experiments revealed that solution pH had a significant impact on Cr(VI) removal capacities, with the maximum observed at pH 2.5. From a kinetic viewpoint, Cr(VI) removal was best described by a pseudo-second-order model. Importantly, the scavenger reaction was significantly promoted in the presence of SO42–, being slightly inhibited by Ca2+ and dissolved oxygen. Thus, the sulfidised nanohybrids exhibited excellent Cr(VI) removal performance, being well suited to the remediation of Cr(VI)-polluted water.