Enhancement in reactivity via sulfidation of FeNi@BC for efficient removal of trichloroethylene: Insight mechanism and the role of reactive oxygen species.

A novel catalyst of sulfidated iron-nickel supported on biochar (S-FeNi@BC) was synthesized to activate persulfate (PS) for the removal of trichloroethylene (TCE). A number of techniques including XRD, SEM, TEM, FTIR, BET and EDS were employed to characterize S-FeNi@BC. The influence of sulfur to iron ratio (S/F) on TCE removal was investigated by batch experiments and a higher TCE removal (98.4%) was achieved at 0.22/1 ratio of S/F in the PS/S-FeNi@BC oxidation system. A dominant role in iron species conversion was noticed by the addition of sulfur in FeNi@BC system. Significant enhancement in recycling of the dissolved and surface Fe(II) was confirmed which contributed to the generation of free and surface-bound active radical species (OH, O, O, SO). Further, the presence and contribution of these radicals were validated by the electron paramagnetic resonance (EPR) and quenching study. In addition, XPS results demonstrated the dominant role of S(-II) with the increase of Fe(II) from 36.3% to 58.6% and decrease of Fe(III) from 52.1% to 39.8% in the PS/S-FeNi@BC system. In crux, the influence of initial pH, catalyst dosage, oxidant dosage, and inorganic ions (HCO, Cl, NO and SO) on TCE removal was also investigated. The findings obtained from this study suggest that S-FeNi@BC is an appropriate catalyst to activate PS for TCE contaminated groundwater remediation.