Fenton/Fenton-like processes with in-situ production of hydrogen peroxide/hydroxyl radical for degradation of emerging contaminants: Advances and prospects

Fenton processes based on the reaction between Fe2+ and H2O2 to produce hydroxyl radicals, have been widely studied and applied for the degradation of toxic organic contaminants in wastewater due to its high efficiency, mild condition and simple operation. However, H2O2 is usually added by bulk feeding, which suffers from the potential risks during the storage and transportation of H2O2 as well as its low utilization efficiency. Therefore, Fenton/Fenton-like processes with in-situ production of H2O2 have received increasing attention, in which H2O2 was in-situ produced through O2 activation, then decomposed into hydroxyl radicals by Fenton catalysts. In this review, the in situ production of H2O2 for Fenton oxidation was introduced, the strategies for activation of O2 to generate H2O2 were summarized, including chemical reduction, electro-catalysis and photo-catalysis, the influencing factors and the mechanisms of the in situ production and utilization of H2O2 in various Fenton/Fenton-like processes were analyzed and discussed, and the applications of these processes for the degradation of toxic organic contaminants were summarized. This review will deepen the understanding of the tacit cooperation between the in situ production and utilization of H2O2 in Fenton process, and provide the further insight into this promising process for degradation of emerging contaminants in industrial wastewater.