The oxidation of organic compounds by Fe(II)/H 2 0 2 (known as Fenton's reagent) has been known for nearly a century. Recently, this reagent has been used in wastewater treatment technology. The scope and the range of applicability of Fenton and Fenton like [Fe(ni)/H 2 0 2 ] reagents in advanced oxidation technology is reviewed and selected examples of their application are presented. The rate of oxidation and the extent of mineralization of organic pollutants with these reagents is improved significantly by irradiation with UV-visible light. The usefulness of UV-visible/ Fe(II)/H 2 0 2 and UV-visible/Fe(III)/H 2 0 2 processes are exemplified through specific applications. Still, much higher improvement in the rate of destruction of organic pollutants is achieved by replacement of Fe(II)/Fe(III) with ferrioxalate.

Methyl tert-butyl ether (MTBE) is a pollutant often found in groundwaters contaminated by gasoline spills or from leaking underground storage tanks. The common techniques often used for the remediation of contaminated water are not very effective for MTBE. This study examines the UV/ H 2 O 2 advanced oxidation technology to determine its effectiveness in the treatment of MTBE. The degradation of MTBE was found to follow pseudo-first-order kinetics, and hence the figure-of-merit electrical energy per order (E EO ) is appropriate for estimating the electrical energy efficiency. The E EO values were found to depend on the concentrations of MTBE, H 2 O 2 , and other components, such as benzene, toluene, and xylenes (BTX). This study shows that MTBE can be treated easily and effectively with the UV/H 2 O 2 process with E EO values between 0.2 and 7.5 kWh/m 3 /order, depending on the initial concentrations of MTBE and H 2 O 2 . The treatment efficiency of 10 mg L -1 MTBE is not adversely affected by the presence of low concentrations of BTX (<2 mg L -1 ). However, the degradation efficiency is significantly decreased at BTX levels greater than 2 mg L -1 . A kinetic model, based on the initial rates of degradation, provides good predictions of the E EO values for a variety of conditions.

Second excited singlet state (S2) fluorescence quantum yields and lifetimes of six aromatic thiones have been measured in solution at room temperature. Intramolecular S2 S, internal conversion dominates S2 decay in inert perfluoroalkane solvents, but intermolecular photochemical and photophysical processes dominate in more strongly interacting solvents. Stern-Volmer quenching is observed when perfluoroalkane solutions of 2,2,3,3-tetramethylindanthione, a model thione, are spiked with addends at concentrations up to ca. 0.3 M. Measurements of the rate constants for the bimolecular quenching of S2 fluorescence by 26 different addends reveal that the thione S2 state is highly reactive and that the initial intermolecular interaction path divides into physical and chemical branches, the branching ratio being a function of the nature of the quencher.

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