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

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 (Ca 2+ and SO 4 2– ). 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 SO 4 2– , being slightly inhibited by Ca 2+ and dissolved oxygen. Thus, the sulfidised nanohybrids exhibited excellent Cr(VI) removal performance, being well suited to the remediation of Cr(VI)-polluted water.