Sulfidation of nano zero-valent iron (S-nZVI) for enhanced hexavalent chromium (Cr(VI)) removal performances

Abstract Nano zero-valent iron (nZVI) and sulfidation modified nZVI (S-nZVI) were synthesized and employed for hexavalent chromium (Cr(VI)) removal in wastewater. Characterizations of products showed that the sulfidation process could significantly change the morphologies, and the degree of crystallinity was also enhanced. The effects of S/Fe ratio, pH value and reaction temperature were studied, the most appropriate parameter was considered of S/Fe ratio = 0.5, and removal efficiency could reach up to the 98% in the condition of pH = 2. The influences of anions (Cl−, NO3−, CO32−, and SO42−) and cations (Ca2+ and Mg2+) on the Cr(VI) removal efficiency were investigated and the mechanisms were discussed. The Cr(VI) removal efficiency of S-nZVI was obviously better than that of nZVI, mainly owing to the existence of FeS layers that could protect Fe0 cores and prompt electron transfer. The aging and cycling experiments showed that S-nZVI products could maintain its reactivity facing the corrosion of water, and showed satisfying cycling stability. Thus, the prepared S-nZVI was an effective and feasible agent for the remediation of Cr(VI)-contained wastewater.