Peroxymonosulfate activation by sulfur doped CoFe2O4 rod for arsanilic acid removal: Performance and arsenic enrichment

For a long time, the low toxicity of arsanilic acid (p-ASA) makes people ignore its potential risk. The highly diffusible and fatal arsenic produced from the decomposition of p-ASA has sounded the alarm for humans. In this study, a rod-like sulfur doped CoFe2O4 (S-CoFe2O4) was successfully prepared to activate peroxymonosulfate (PMS) for the p-ASA removal. By adding 40 mg/L S-CoFe2O4 and 0.02 mM PMS, 10 mg/L p-ASA can be thoroughly degraded within 15 min. The pseudo-first-order reaction rate constant was calculated to be 0.37 min−1, which was 7.4 times that of CoFe2O4/PMS system (0.05 min−1). S-CoFe2O4/PMS system achieved satisfactory p-ASA removal under acidic, neutral, and alkalescent situations. In addition to the superior p-ASA degradation efficiency, S-CoFe2O4/PMS system can synchronously immobilize the released arsenic, and 73% of arsenic was adsorbed on S-CoFe2O4 surface. Catalytic mechanism study showed that divalent metal active site, oxygen vacancy, and sulfite were responsible for the generation of reactive oxygen species (ROSs) involving·OH, O2·-, and 1O2. This study proposes a reliable approach for safely removing p-ASA in water, and broadens the application of cobalt ferrite.