Abstract
This work investigates the effect of UV-LED on the persulfate (PS) activation with natural ilmenite (FeTiO3) in the oxidation of azo dye Disperse Blue 3 (DB3). The high induction period and the scarce ability of this mineral to activate PS can be overcome by using UV irradiation to increase the SO4− generation via photoreduction of Fe(III) to Fe(II) on the ilmenite surface, main responsible of SO4− formation in iron-based catalysis. The effect of several operating conditions such as persulfate dose (20–100% of the theoretical stoichiometric amount), reaction temperature (30–70°C) and mineral concentration 320mgL−1 has been studied. Under optimum conditions (320mgL−1of ilmenite, pH0: 3, using 100% of stoichiometric amount of PS at 70°C under UV-LED radiation) more than 95% TOC reduction and 92% PS decomposition were reached after 180min. The progressive deactivation of FeTiO3 through successive experiments can be explained, according to density functional theory (DFT) calculations, by the formation of a passivation layer due to adsorption of SO42− on the FeTiO3 surface.
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