UVA-UVB activation of hydrogen peroxide and persulfate for advanced oxidation processes: Efficiency, mechanism and effect of various water constituents

In the present work we investigate the activation efficiency of H2O2 and S2O82- using UVA and UVB radiation. Bisphenol-A (BPA) is used as model pollutants to estimate the oxidative process efficiency in simulated and real sewage treatment plant waters. Particular attention is paid to the BPA removal efficiency and to the radical mechanism involvement considering the effect of typical inorganic water constituents (carbonates and chloride ions) and organic matter. Despite a detrimental effect observed when carbonate ions are in solution using both hydrogen peroxide and persulafate, the presence of high chloride ions concentration was found to improve BPA removal using S2O82- as radical precursor. This enhancement, investigated combining chemical kinetic model approach and laser flash photolysis experiments, is attributed to the formation of hydroxyl radical and chlorine radical species from sulfate radical. Different transformation products are identified by means of GC-MS and HPLC-MS analyses. Moreover, experiments using sewage treatment plant water (STPW) spiked with BPA are performed in order to assess the efficiency of oxidative processes in a simulated treatment systems activated using UVA + UVB radiations.