Degrading arsanilic acid and adsorbing the released inorganic arsenic simultaneously in aqueous media with CuFe2O4 activating peroxymonosulfate system: Factors, performance, and mechanism

Abstract

Arsanilic acid (ASA) is widely used as a feed additive in poultry production that tends to convert to highly toxic inorganic arsenic species in the natural environment. Herein, one-step process by CuFe2O4 activating peroxymonosulfate (PMS) was employed for ASA degradation and released inorganic arsenic absorption from aqueous media. The effect of some key parameters including catalyst dosage (0–0.5 g/L), PMS concentration (0–500 μM), initial pH (3.4–10.5) and water matrices (Cl-, HCO3-, NO3-, Fe2+, Fe3+, Mg2+, Ca2+, NH4+ and humic acid) on ASA degradation were investigated. More than 99% of ASA (26.72 μM, 2 mg-As/L) was converted to As(V), and 84.65% of it was adsorbed on CuFe2O4 simultaneously within 90 min at 0.3 g/L CuFe2O4, 200 μM PMS at initial pH 7. Specifically, the presence of humic acid significantly inhibited ASA degradation. Cl- had a dual effect, HCO3- and Fe2+ had a promoting effect and some common cations (Fe3+, Mg2+, Ca2+, and NH4+) had negligible effect on ASA conversion. FTIR and XPS analyses indicated the removal of inorganic arsenic followed the mechanism of inner-sphere complex. Radicals analyses showed that O2∙-, OH and SO4·- (free and surface-bound) accounted for arsenic species oxidation in the CuFe2O4/PMS system. Besides, ASA could also be oxidized to the nitrated product (nitarsone) through a non-radical pathway by PMS alone. The degradation products of ASA were identified by LC/MS/MS and the degradation pathways were proposed, and their toxicity was assessed using luminescent bacteria Vibrio fischeri. Moreover, the recovered catalyst exhibited high stability and reusability tested by SEM, TEM, XRD and leaching ions experiments.