High-Efficiency Simultaneous Oxidation of Organoarsenic and Immobilization of Arsenic in Fenton Enhanced Plasma System

Roxarsone (ROX), an organoarsenic compound serving as a common feeding additive, is heavily utilized in the agricultural field and brings about the potential risks of toxic inorganic arsenic contamination in the ambient environment. In this study, the applicability of glow discharge plasma (GDP) for simultaneous oxidation of organoarsenic and immobilization of arsenic is unprecedentedly evaluated. The results show that ROX can be effectively oxidized to inorganic arsenic, and this performance is evidently dependent on energy input. Adding Fe­(II) can significantly enhance the oxidation of ROX mainly because of the additional production of ^•OH via Fenton reaction in GDP, accompanied by which the generated arsenic can be simultaneously immobilized in one process. The immobilization of arsenic can be favorably obtained at pH 4.0–6.0 and Fe­(II) concentration ranging from 500 to 1000 μM. On the basis of the mineral compositions and analysis (XRD/FTIR/XPS) of precipitate, a mechanism can be proposed that the oxidation of Fe­(II) by H₂O₂ generated in situ in GDP significantly accelerates ROX transformation to the ionic As­(V), which can immediately precipitate with Fe­(III) ions or be adsorbed on the ferric oxyhydroxides, forming amorphous ferric arsenate-bearing ferric oxyhydroxides. As such, the present study offer a new recipe for rapid decontamination of organoarsenic pollutants, in which the hypertoxic species can be effectively removed from the wastewater.