Efficient removal of Cr(VI) by sulfide nanoscale zero-valent iron: characterization, aging and mechanism

In the research, sulfide nanoscale zero-valent iron (S-nZVI) was synthesized, characterized and further applied to remove hexavalent chromium Cr(VI) from water. The results showed that a maximum adsorption (81 mg/g) and repeatability was reached at a sulfur/iron molar ratio of 0.1. Sulfide modification could form amorphous FeS on the surface of nZVI, which enhanced the antioxidant activity and hydrophobicity of S-nZVI0.1. The removal of Cr(VI) by S-nZVI0.1 was in accordance with the pseudo-second-order and Langmuir model with the theoretical removal capacity of 83.51 mg/g. After aging 45 d, 60 mg/g of Cr(VI) still was adsorbed by S-nZVI0.1, suggesting that S-nZVI0.1 exhibited a better stability. 84.1% of Cr(VI) was reduced to Cr(III) on the surface of S-nZVI0.1, Fe0, FeS, Fe2+ and S2− were involved in the reduction reaction. This study provided guidance for synthesizing well stability and high reaction of S-nZVI to remove Cr(VI).