Feasibility of UVC laser-activated persulfate with concentrated beam for micropollutant degradation in water

• A novel UVC laser-activated persulfate AOP was developed. • The effect of UVC laser beam type on BPA degradation was investigated. • The effect of reactor depth-to-diameter ratio on BPA degradation was evaluated. • Laser produce more photons at high depth-to-diameter. A novel UV light, UVC laser, was used to activate persulfate (PS) for degrading bisphenol A (BPA) in this study. This new light source can emit concentrated beam, and achieve 74.5% of BPA removal within only 60 s when activating PS. Sulfate radicals (SO 4 − ) and hydroxyl radicals (OH ) were identified in the UVC laser/PS system. In the case of the same total irradiance energy, the concentrated beam performed a better removal efficiency of BPA than the diffused beam. Compared with the diffused beam, the steady-state concentrations of SO 4 − and OH under concentrated beam increased by 26.21% and 361.25%, respectively. In addition, the depth-to-diameter ratio (h/D) of the reaction vessels also had a significant effect on the removal efficiency of BPA and the highest degradation rate obtained at h/D = 0.65. High UVC laser intensity, high PS dosage, and circumneutral pH conditions could promote BPA degradation, whereas the presence of water matrix (including chloride, bromide, bicarbonate, and natural organic matter) exhibited opposite effects. The BPA degradation intermediates in the UVC laser/PS system were identified by LCMS and the BPA degradation pathways were proposed accordingly. This study is the first one illustrating the influence of laser beam types, h/D ratio of the reactor vessel, and water matrix on UVC laser/PS application in water treatment process, which can provide essential knowledge for removing micropollutants in water using the novel UVC laser/PS AOP.