Photodegradation of 2,3,4,5-tetrachlorophenol in water/methanol mixture

The photodegradation of 2,3,4,5-tetrachlorophenol in water/methanol mixture using a low pressure 16 W mercury lamp was examined. The rate constants and quantum yields of the reaction were determined. The effect of pH on rate constants was also studied. The estimated first-order rate constants k for the phototransformation of 2,3,4,5-TeCP were found to be 6.48 × 10−3 min−1 (pH 2), 9.51 × 10−3 min−1 (pH 4.5) and 18.31 × 10−3 min−1 (pH 11). The determined quantum yield of TeCP reaction was 0.194 at pH 4.5.The kinetic curves for formation of less chlorinated photodecomposition products are also presented. Analysis of the intermediates showed that hydroxylation of chlorophenols (CP) was involved in the oxidation during photodegradation. Finally, the pathway of photodecomposition of these compounds is proposed.