Vacuum-UV Oxidation (H2O-VUV) with a Xenon Excimer Flow-Trough Lamp at 172 nm: Use of Methanol as Actinometer for VUV Intensity Measurement and as Reference Compound for OH-Radical Competition Kinetics in Aqueous Systems

Abstract During the past decade the intensive development of novel incoherent xenon excimer light sources emitting in the vacuum-UV region of the electromagnetic spectrum at λmax of 172 nm led to a renaissance of investigations that deal with the direct photolysis of water. Upon 172 nm excitation water molecules homolyze with formation of hydroxyl radicals and hydrogen atoms. In the presence of organic substrates and dissolved molecular oxygen a complex series of interrelated radical reactions is initiated leading to the oxidative degradation of the organic compounds and finally to their complete mineralization, i.e. to the diminution of the total organic carbon (TOC) content of the solution. This advanced oxidation process (AOP) is usually designated as H