Kinetic modeling and mechanisms of parahalogenated phenols degradation by UV222/H2O2

Advanced oxidation technology of KrCl excimer lamp activated H 2 O 2 (UV 222 /H 2 O 2 ) have been received widespread attention in the field of water treatment recently, due to the higher radical yield and environmentally friendly nature compared to UV 254 /H 2 O 2 . In this investigation, four representative parahalogenated phenols (HPs) degradation kinetic and mechanisms by UV 222 alone and UV 222 /H 2 O 2 were studied, respectively. The results showed that the photolysis rate constants ( k obs ) under UV 222 followed the order of p -Chlorophenol ( p -CP) >  p -Fluorophenol ( p -FP) >  p -Bromophenol ( p -BP) >  p -Iodophenol ( p -IP), and the degradation rate constants ( k obs ) by UV 222 /H 2 O 2 followed the order of p -FP >  p -CP >  p -BP >  p -IP. The molar absorption coefficient ( ε 2 22nm ) and quantum yield ( Φ 222nm ) of HPs photolysis were measured. Kinetic model simulating results are in fair agreement with the experimental results. Through HPLC-MS analysis and DFT calculation, the impact of halogen ions on the degradation kinetics of HPS by UV 222 and UV 222 /H 2 O 2 was found, the possible reaction pathways and mechanisms were proposed. Compared with UV 254 /H 2 O 2 for removing p -CP, UV 222 /H 2 O 2 was much more energy efficient.