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

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.