Rapid degradation of p-arsanilic acid and simultaneous removal of the released arsenic species by Co-Fe@C activated peroxydisulfate process

Abstract

In this study, a bimetallic composite catalyst (Co-Fe@C) was fabricated with calcination at high temperature (800 °C) by using Co-MIL-101 (Fe) as the precursor. The characterization results showed that the resulted Co-Fe@C composite mainly consisted of carbon, FeCo alloys, Fe₃O₄, Co₃O₄ and FeO, and owned evident magnetism. In addition, the Co-Fe@C was employed to activate the peroxydisulfate (PDS) to degrade a representative organic pollutant (p-arsanilic acid, p-ASA) and the main factors were optimized, which involved 0.2 g L^-1 of catalyst dosage, 1.0 g L^-1 of PDS dosage and 5.0 of initial pH. Under the optimal condition, Co-Fe@C/PDS system could completely degrade p-ASA (20 mg L^-1) in 5 min. In the Co-Fe@C/PDS system, SO₄^-·, Fe(IV) and ·OH were the main species during p-ASA degradation. Under the attack of these species, p-ASA was first decomposed into phenols and then transformed into the organics acids and finally mineralized into CO₂ and H₂O through a series of reactions like hydroxylation, dearsenification, deamination and benzene ring opening. Importantly, most of the released inorganic arsenic species (93.40%) could be efficiently adsorbed by the catalyst.

Keywords: Degradation; Fe-based catalyst; MOF; Persulfate activation; Phenylarsonic acid pollutant.