Comparison between O₃/VUV, O₃/H₂O₂, VUV and O₃ processes for the decomposition of organophosphoric acid triesters

O₃/vacuum ultraviolet (VUV, ultraviolet radiation by a low pressure mercury lamp at 185 and 254 nm), O₃/H₂O₂ and VUV processes rapidly decomposed organophosphoric acid triesters (OPEs) dissolved in distilled water as compared to simple ozonation. The O₃/VUV process was the fastest of the three advanced oxidation processes (AOPs) for the decomposition of 1 mg/l of OPEs in pH 7.5 phosphate buffer solution (0.5 mM). However the difference between the pseudo-first-order rate constants of the O₃/VUV and O₃/H₂O₂ processes decreased in the condition of increasing OPEsw concentration, and the efficiencies of the two processes were almost the same at an initial concentration of 20 mg/l. Contrary to results in distilled water, in an effluent from a solid waste landfill site, the O₃/H₂O₂ process was the fastest. This is manily due to the absorption of VUV radiation by nitrate ion. WE confirmed that nitrate ion of more than a few mg/l strongly interfered with the generation of hydroxyl (OH) radicals from VUV radiation while the O₃/H₂O₂ process was not affected. The use of an ESR-spin trapping technique revealed that AOPs generated more OH radicals than ozonation alone, and the detection of hydrogen atom confirmed that VUV radiation directly generated OH radicals from water.