Photocatalytic degradation of dissolved organic matter under ZnO-catalyzed artificial sunlight irradiation system

This study investigates the photocatalytic degradation of dissolved organic matter (DOM) under ZnO-assisted artificial sunlight system at various conditions (ZnO dosage, pH, and the presence of Cl(−), SO(4)(2−), and HCO(3)(−)). The results show that the degradation of DOM follows a pseudo-first-order kinetics. Fluorescence excitation–emission matrices coupled with parallel factor (EEM-PARAFAC) analysis decomposes DOM into two fluorophores (C1 and C2). The total removals and photodegradation rates calculated with DOC, UV(254), and the F(max) of C1 are similar, increasing with higher ZnO dosages and being highest in pH 7 and lowest in pH 4. ZnO dosage has a similar effect on DOM degradation when assessed using C2, as with C1, but pH effect is not consistent. As for the anions, HCO(3)(−) shows the strongest inhibition for DOC, UV(254) and C1 while Cl(−) has the strongest facilitation effect for C2. The total removal and photodegradation rates calculated with the F(max) of C1 and C2 are higher than those calculated using DOC and UV(254). This study demonstrates that the successful application of EEM-PARAFAC analysis in addition to traditional parameters can provide further insight into the photocatalytic degradation mechanisms associated with DOM in conjunction with a ZnO catalyst under artificial sunlight.