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^-, SO₄^2-, and HCO₃^-). 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, UV₂₅₄, 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, HCO₃^- shows the strongest inhibition for DOC, UV₂₅₄ 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 UV₂₅₄. 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.