Remediation of Organic Arsenic Contaminants with Heterogeneous Fenton Process Mediated by SiO-coated Nano Zero-valent Iron

Given their considerable solubility in water and potentially high toxicity to human health, organoarsenic compounds have become an emerging contaminant. Herein, a heterogeneous Fenton process mediated by SiO-coated nano zero-valent iron (SiO-nZVI) was employed to simultaneously remove the p-arsanilic acid (p-ASA, a typical organoarsenic compound) and the released arsenic. The initial pH value significantly influenced on the degradation of p-ASA and at the optimal pH (3.0), p-ASA (10 mg L) could be completely oxidized to As(V), NH, and plentiful phenolic compounds such as phenol and p-hydroquinone via the cleavage of C-N and C-As bonds within 60 min in pure water. Meanwhile, although the formed lepidocrocite and magnetite on the surface of SiO-nZVI significantly limited the reutilization, they played a vital role in the adsorption of the released As(V) and the residual arsenic levels in the effluent were as low as 0.031 mg L, meeting both the drinking water standard of the World Health Organization (WHO) and the surface water standard of China (0.05 mg L). Furthermore, high-level dissolved organic matters (DOM) (> 2 mg C L) exhibited strong interference with both the oxidation of p-ASA and adsorption of arsenic, but the interference could be eliminated by increasing the SiO-nZVI dosage or adding HO. Importantly, this system could completely remediate p-ASA in a short time and simultaneously avoid the secondary pollution caused by inorganic arsenic, which was significant for the remediation of organoarsenic pollutants in swine wastewater.