TOXICITY CHANGES DURING THE UV TREATMENT OF PENTACHLOROPHENOL IN DILUTE AQUEOUS-SOLUTION

Pentachlorophenol (PCP) was photolysed using a 1 kW photochemical reac tor. The degradation of PCP (0.15 mM) was carried out using both direc t UV photolysis and photolysis in the presence of H2O2 (3.0, 6.7, 18.0 and 37.2 mM). The decay of PCP and the formation of photoproducts wer e followed by high performance liquid chromatography, ion chromatograp hy and UV absorbance detection. The first-order rate constants k(1) fo r the decay of PCP were estimated under various conditions: for direct UV photolysis, k(1) = 0.115 min(-1); for photolysis in the presence o f various concentrations of H2O2, the rate constant increased to a pla teau (k(1) approximate to 0.7 min(-1)) at H2O2 concentrations greater than 6 mM. The correlation between photodegradation and toxicity was s tudied using a bacterial toxicity test and a 96 h Fathead Minnow toxic ity test. In both cases. the toxicity decreased as the concentration o f PCP or the total organic chlorine concentration fell. These results indicate that the W treatment of PCP either does not generate signific ant levels of acutely toxic intermediates, or any toxic intermediates are rapidly degraded under the specific conditions used in these studi es. (C) 1998 Elsevier Science Ltd. All rights reserved.