Photocatalytic degradation of phenol by the heterogeneous Fe3O4 nanoparticles and oxalate complex system

Abstract

A novel approach for the removal of phenol by an advanced oxidation process using Fe₃O₄ nanoparticles (NPs) and oxalate was proposed and investigated, and the influences of oxalate, Fe₃O₄ NPs and H₂O₂ dosage on the photodegradation of phenol were reported. No obvious difference is found between ultraviolet light and visible light exposure, confirmed potential photoactinic roles of Fe₃O₄ NPs in the presence of oxalate under visible light. Furthermore, relatively high dependence of oxalate depletion was observed due to the initiation of the formation of the Fe(III)-carboxylate complexes for photodegradation via a photo-Fenton-like system. Our results also demonstrated that the photodegradation of phenol occurred by a radical mechanism accompanied with the formation of O₂˙⁻ and ˙OH radicals, which was further accelerated by the exogenous addition of H₂O₂. All reactions followed the pseudo-first-order reaction kinetics. The half-life (t_1/2) of Fe₃O₄–oxalate and Fe₃O₄–oxalate–H₂O₂ in the system showed higher efficiencies of photo-Fenton-like degradation routes for phenol. The photo-Fenton-like systems showed a relatively high catalytic ability (>99.9%) in the removal of phenol at low phenol concentrations below 50 mg L⁻¹, indicating its potential application in the treatment of low concentration wastewater. The results have demonstrated the feasibility of Fe₃O₄ NPs as potential heterogeneous photo-Fenton photocatalysts for organic contaminants decontamination in industrial wastewater.