Research On The Degradation Of Halogenated Organic Compounds Under Vacuum-UV Irradiation

This study was focus on the possibility on the halogenated disinfection by-products during disinfection, and research the efficiency of 2-CP degradation under VUV treatment. The effects of main influential factors on the degradation of 2-chlorophenol by VUV, which was chosen as a probe hereinafter, and kinetic analysis was carried out.The degradation mechanism of 2-CP was also investigated. Modeling of the degradation of 2-CP under VUV and a new method of the measurement of the photon flux of VUV was proposed. Finally, HPs and MCAA degradation under VUV was investigated and monochlorophenols were selected as probes to investigate the removal in real surface water matrix.The results shows that, the degradation efficiency of 2-CP under VUV increased along with the temperature. And the HA existence in water inhibitded the degradation. p H had little impact on 2-CP degradation in the range of 5-10. Other water matrix, such as ferrous ion, chloride ion, ammonium, bicarbonate also had little impact. The degradation of 2-CP under VUV system agreed well with pseudo-first order kinetics and the apparent activation energy was calculated to be(17.18±1.61) KJ·mol-1.The investigation on the reason of the degradation of 2-CP under VUV showed that the contribution of hydroxyl radicals was far more than that of reductive speicies. Also, the oxygen accelerated the mineralization of 2-CP under VUV irradiation.To measure the formation rate of hydroxyl radicals under VUV irradiation, the rate constant of hydroxyl radicals between 2-CP was calculated via a competitive kinetic method. And the photon flux of the VUV irradiation at 185 nm was calculated to be(1.68±0.03) ×10-7Einstein·s-1The degradation rate of HPs under VUV irradiation decreased in the descending order C-Cl>C-Br>C-Cl substitution, para-> meta- ≈ ortho- substitution position and halogenation degree. MCAA also had an excellent degradation efficiency under VUV irradiation. HPs had a great degradation efficiency in different water matrix. The result show that the compounds in water had a great influence on the efficiency of the organic compound removal under VUV irradiation.Though the cost of the VUV system was higher than that of UV/H2O2, the EE/O value of VUV system was still under the standard. And the VUV system had a high efficiency, without adding any chemicals during the treatment, which can be potentially applied. Additionally, the reactor design has a great influence on the cost of VUV systems.