Ultraviolet Irradiation of Permanganate Enhanced the Oxidation of Micropollutants by Producing HO^• and Reactive Manganese Species

Permanganate was activated by ultraviolet (UV) photolysis at 254 nm, resulting in the efficient degradation of micropollutants. The degradation of four probe molecules (i.e., nitrobenzene, benzoic acid, terephthalic acid, and p-chlorobenzoic acid) and two micropollutants (i.e., gemfibrozil and nalidixic acid) resistant to permanganate oxidation was enhanced by the UV/permanganate system, with pseudo-first-order rate constants (k′) of 0.065-0.678 min^-1 under the experimental conditions. Hydroxyl radicals (HO^•) and Mn(V) peroxide, which were produced during the activation of permanganate by UV irradiation, were responsible for the enhancement. The quantum yield of HO^• was 0.025 ± 0.001 mol Einstein^-1 (mol Es^-1) in the system. HO^• oxidation primarily accounted for the degradation of nitrobenzene and gemfibrozil, while both HO^• and Mn(V) were responsible for the degradation of benzoic acid, terephthalic acid, p-chlorobenzoic acid, and nalidixic acid. This study is the first report on the activation of permanganate by UV irradiation for the abatement of micropollutants in water treatment, which may lead to a new advanced oxidation process relying on both HO^• and reactive manganese species.