Degradation of Acetaminophen via UVA-induced advanced oxidation processes (AOPs). Involvement of different radical species: HO, SO and HO/O.

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO and HO/O) are generated through activation of hydrogen peroxide (HO), sodium persulfate (NaSO) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/HO and UVA/NaSO systems whatever the solution's pH. To explain these results, second order reaction rate constant (k) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO/O radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and NaSO exhibits synergistic effects rather than antagonism effects with HO. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.