Enhanced oxidative and adsorptive removal of arsenite by the heterogeneous interfacial reaction of sulfidated nanoscale zerovalent iron

Sulfidated nanoscale zero valent iron (S-nZVI) synthesized using a one-step approach is used to remove As(iii) in anoxic water. The reaction between S-nZVI and As(iii) follows pseudo-second-order kinetics, and the rate constant is 0.28015 g mg(-1) min(-1), which is 14 times higher than that of pristine nZVI 0.02005 g mg(-1) min(-1). The rapid reactive rate is attributed to the sulfur dopant in the metallic iron crystal lattice forming polysulfide iron (FeSx). Electrochemical impedance spectroscopy of S-nZVI reacted with As(iii) in water and demonstrated a smaller ohm resistance and super electron transfer efficiency. Interfacial goethite (& alpha;-FeOOH) in S-nZVI can oxidize As(iii) to As(v). Synergistic effects of FeSx and & alpha;-FeOOH enhance the oxidization of As(iii) to As(v) from & SIM;10% to & SIM;45% compared with nZVI, as evaluated by X-ray photoelectron spectroscopy (XPS). Arsenic atoms diffuse the inner area of S-nZVI based on atomic scale transmission electron microscopy - energy dispersive spectroscopy mapping and XPS with ion etching technique and can be tightly immobilized as hardly soluble As2S3 and As2S5 precipitates by sulfur owing to its high affinity of arsenic. This study provides a facile strategy to sequestrate toxic metals from aquatic environments and highlights the vital properties determined by the structure.