摘要：

The removal of As(V), one of the most poisonous groundwater pollutants, by synthetic nanoscale zero-valent iron (NZVI) was studied. Batch experiments were performed to investigate the influence of pH, adsorption kinetics, sorption mechanism, and anionic effects. Field emission scanning electron microscopy (FE−SEM), high-resolution transmission electron microscopy (HR−TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Mössbauer spectroscopy were used to characterize the particle size, surface morphology, and corrosion layer formation on pristine NZVI and As(V)-treated NZVI. The HR−TEM study of pristine NZVI showed a core-shell-like structure, where more than 90% of the nanoparticles were under 30 nm in diameter. Mössbauer spectroscopy further confirmed its structure in which 19% were in zero-valent state with a coat of 81% iron oxides. The XRD results showed that As(V)-treated NZVI was gradually converted into magnetite/maghemite corrosion products over 90 days. The XPS study confirmed that 25% As(V) was reduced to As(III) by NZVI after 90 days. As(V) adsorption kinetics were rapid and occurred within minutes following a pseudo-first-order rate expression with observed reaction rate constants (kobs) of 0.02−0.71 min-1 at various NZVI concentrations. Laser light scattering analysis confirmed that NZVI−As(V) forms an inner-sphere surface complexation. The effects of competing anions revealed that HCO3-, H4SiO40, and H2PO42- are potential interfering agents in the As(V) adsorption reaction. Our results suggest that NZVI is a suitable candidate for As(V) remediation.

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