Remediation Of Arsanilic Acid Polluted Water By CuFe₂O₄ Catalyzed Peroxymonosulfate

As an organoarsenic feed additive,arsanilic acid（ASA）is widely used in livestock and poultry production to prevent disease and promote growth.However,more than 90%of the ASA ingested by animals is not assimilated but is excreted in their urine and feces.Usually,the waste is transported to the fields as fertilizer.Because of the high water-solubility of ASA,it is easy to be leached into the water environment by rainwater or irrigation water,resulting in the increase of total arsenic content in nearby water bodies.In nature,ASA can be easily converted into highly toxic inorganic arsenic passively absorbed by plants through anaerobic biodegradation or natural light degradation,and eventually threatens human health through the food chain.In this study,an oxidation-adsorption method was used,namely,CuFe₂O₄activated peroxymonosulfate（PMS）to degrade ASA and the released inorganic arsenic was removed by catalyst from aqueous media.The effect of some key parameters including catalyst dose（0-0.5g/L）,PMS concentration（0-500μM）,initial p H（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（26.72μM）was converted to As（V）,and 84.65%of it was adsorbed on CuFe₂O₄simultaneously within 90 min at 0.3 g/L CuFe₂O₄,200μM PMS at initial p H 7.Specifically,the presence of humic acid significantly inhibited ASA degradation.However,Cl^-had a dual effect,inhibiting effect at 0-10 m M and promoting effect at10-50 m M);HCO₃^-（0-50 m M）and 1 m M Fe²⁺had a promoting effect and 1 m M of other cations(e.g.Fe³⁺,Mg²⁺,Ca²⁺,and NH₄⁺)and anion 0-50 m M NO₃^-had negligible effect on ASA conversion.FTIR and XPS analyses indicated the removal of inorganic arsenic followed the mechanism of inner-sphere complex.Electron paramagnetic resonance test and radicals analyses showed that O₂^·-·OH and SO₄^·-（free and surface-bound）.The formation of these free radicals is mainly dependent on the Cu（II）/Cu（III）and Fe（III）/Fe（II）cycles and thsy all accounted for arsenic species oxidation in the CuFe₂O₄/PMS system.Besides,the use of PMS alone can also oxidize ASA to nitrophenylarsonic acid via a non-radical pathway.Eight possible degradation products were identified by LC/MS/MS analysis,and two degradation pathways of ASA were proposed based on this analysis.And their toxicity was assessed using luminescent bacteria Vibrio fischeri.Moreover,the recovered catalyst exhibited high stability and reusability tested by XRD and leaching ions experiments.This study shows that CuFe₂O₄/PMS oxidation-adsorption system provides a new insight for reducing the potential environmental risks of organic arsenic in water,and provides an effective strategy for improving the overall arsenic removal.