Photo-Fenton oxidation of phenol with magnetite as iron source

In this work, magnetite-catalyzed Fenton reaction was investigated under UVA irradiation for the degra-dation of phenol as model compound. Four kinds of magnetite were used having different particle size,surface area and FeIIcontent. Different kinetic behaviors were observed, thereby underscoring the strongimplications of surface and chemical properties of magnetite. The size and surface area of the particlesseemed to be less important, while the FeII/FeIIIratio played some role. Despite the link between mag-netite reactivity and its structural FeIIcontent, light-induced reduction of FeIIIto FeIIwas found necessaryto promote the Fenton-based reactions. As surface FeIImay be oxidized or otherwise unavailable, initialphotoactivation may be needed to trigger the Fenton reactivity. Two major driving forces were high-lighted that account for the photoactivity of magnetite at pH 3: (i) the formation of intermediates suchas hydroquinone that are able to reduce FeIIIto FeII, and (ii) the accumulation of dissolved Fe due tomagnetite dissolution, both in dark and under irradiation. Very interestingly, the photo-Fenton degra-dation of phenol was also observed under neutral conditions. In this case, for two out of four samples,the degradation rates were quite near those found at pH 3, which is usually reported as the optimum pHvalue of the process. The magnetite ability to promote photo-Fenton reactions even under circumneutralpH conditions, the limited iron leaching and its easy magnetic separation makes magnetite a promisingcatalyst in wastewater treatment applications.