ENHANCED OXIDATION OF METHOXY PHENOLS AT MICROMOLAR CONCENTRATION PHOTOSENSITIZED BY DISSOLVED NATURAL ORGANIC MATERIAL

The rate coefficients for the photosensitized oxidation of various phe nols in aqueous solutions containing dissolved natural organic materia l increased in some cases with decreasing phenol concentration. For 3, 4-dimethoxyphenol and 4-methoxyphenol at initial concentration going f rom 10 to 1.0 mu M, the rate coefficients increased by a factor of 5 i n a humic acid solution and by a factor of 2 in a fulvic acid solution and a lake water. For 2,4,6-trimethylphenol, 4-methylphenol and pheno l at initial concentration going from 15 to 2.5 mu M, they increased b y a factor < 2 in the humic acid solution and were constant in the ful vic acid solution and the lake water. We suggest that the methoxy phen ols, which are known to easily reduce oxidants, readily react with a c lass of photo-oxidants whose lifetime is expected to be > 100 mu s. Th ereby the long-lived photo-oxidants seem to be scavenged by the phenol s themselves.