Fluorimetric investigation of reactions between ozone and excited state aromatic compounds on silica gel

A new fluorimetric method has been developed to study the kinetics involved in the ozonation of aromatic compounds. The experimental design utilizes an oxygen-free ozone-nitrogen gas stream during dark- and photo-ozonolysis measurements. Specifically, the decomposition of three aromatic compounds (naphthalene, α-aminonaphthalene, and α-bromonaphthalene) adsorbed on silica gel particles has been investigated. The rates of dark-ozonolysis, photo-ozonolysis, and photo-oxygenation of these compounds were measured separately. This is the first documented direct measurement of photoinduced ozonolysis of an aromatic compound. Unlike previous studies, the measurements of the dark-ozonolysis and photo-ozonolysis are free from the influence of oxygen. The photo-ozonolysis was found to be several orders of magnitude faster than its corresponding photo-oxygenation reaction. The applications of this on-line fluorescence monitoring system may provide valuable kinetic and mechanistic information on the photoinduced degradation of aromatic compounds in the atmospheric environment as well as in wastewater treatment.