Prolonged persulfate activation by UV irradiation of green rust for the degradation of organic pollutants

Metal-activated persulfate is an efficient reagent for the oxidative degradation of organic contaminants. However, homogenous catalytic activation of persulfate has the drawbacks of narrow pH range and metal ion contamination. Here, we designed a heterogeneous system for persulfate activation by green rust irradiated withultraviolet light-emitting diode for the removal of organic pollutants. Generated radicals were identified through radical quenching experiments. Results show that benzoic acid can be degraded. Although structural Fe-II in green rust can activate persulfate, the rapid oxidation of Fe-II-Fe-III by persulfate quickly ceases further persulfate activation in the absence of UV irradiation. Here, UV irradiation reduces the generated Fe-III on the surface of green rust to Fe-II for prolonged persulfate activation. The highest benzoic acid degradation was obtained with 1.0mM persulfate and 0.5mM green rust, expressed as Fe-II concentration. HO is the main oxidative species responsible for benzoic acid degradation.