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

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, Fe 3 O 4 , Co 3 O 4 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, SO 4 − · , 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 CO 2 and H 2 O 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.