Oxygen vacancy induced peroxymonosulfate activation by Mg-doped Fe2O3 composites for advanced oxidation of organic pollutants.

Oxygen vacancy engineering has emerged as an effective approach to improve the performance of catalysts for peroxymonosulfate (PMS) activation. Herein, we report a facile precipitation method followed by calcination to synthesize cost-effective and environmentally friendly magnesium-doped hematite (Mg/Fe2O3) composites. Multiple characterization results reveal that the incorporation of Mg can significantly increase the oxygen vacancies and specific surface area of 5%Mg/Fe2O3, leading to a significantly enhanced performance in degrading Rhodamine B (RhB) through PMS activation. In a typical reaction, almost complete RhB (10 mg/L) removal can be achieved by the activation of PMS (0.2 g/L) using 5%Mg/Fe2O3 (0.5 g/L). Moreover, the as-synthesized catalyst exhibits a broad pH working range (3.96-10.69), high stability, and recyclability. The effects of several parameters (e.g., catalyst amount, PMS dosage, solution pH and temperature, and coexisting inorganic anions) on the removal of RhB in the 5%Mg/Fe2O3/PMS system are investigated. A plausible PMS activation mechanism is proposed, and 1O2 and O2- are identified as the predominant reactive species in RhB degradation instead of SO4- and OH. This study provides new insights into the development of highly efficient iron-based catalysts and highlights their potential applications in environmental purification.