Triclosan removal by heterogeneous Fenton-like process: Studying the kinetics and surface chemistry of Fe3O4 as catalyst

Abstract

Fe3O4 was used as a recoverable catalyst in heterogeneous Fenton-like process for Triclosan (TCS) degradation in this study. The kinetics and surface chemistry of the catalyst were investigated in detail. Peroxymonosulfate (PMS) was used to generate radicals and found to be an effective oxidant used with Fe3O4. The effects of Fe3O4 and PMS dosage, adsorption, pH and catalyst surface charges were studied. The system is at optimum at [TCS:PMS] at 1:25 and increases linearly with Fe3O4 dosage from 0.125 to 0.750 g/L. Under the optimum condition, TCS was removed in less than 60 min. It is concluded that Fe3O4 has the role of both adsorbent and catalyst. TCS and PMS are adsorbed near or onto Fe3O4 surface for catalytic reactions. The pH level has a critical effect on the reaction as it changes the form of active sites of Fe3O4. The active site of Fe3O4 is positive ( Fe−OH2+) in acidic and negative ( Fe–O−) in alkaline solution, leading to different adsorbility of PMS and TCS. The optimum pH for this reaction is in pH 6–9, in which the low surface charges on Fe3O4 allow both PMS and TCS to access active sites and form inner-sphere complex for reaction.