Abstract
Caproic acid and acetic acid contained in water as aliphatic mono-carboxylic acids were investigated for the decomposition level caused by UV irradiation alone with low presser mercury lump, ozone alone or ozone-UV irradiation. The buffer solutions for preparing sample solutions were studied. Decomposition of 5 mM caproic acid was much slower in the 0.2 M KCl-HCl buffer solution (pH 2.0). The delay of the decomposition thus detected seemed to be due to the consumption of ozone by chloride ion. Therefore, the 0.05 M phosphate buffer (pH 7.0) solution as a medium was most appropriate. Caproic acid contained in water was not decomposed at all by the treatment with UV alone and was decomposed very slowly by the treatment with ozone alone, and the decrease of total organic carbon (TOC) was very low. On the other hand, it was found that caproic acid was very rapidly decomposed by the simultaneous treatment with ozone and UV irradiation, and the removal of TOC was also high. Though acetic acid was particularly difficult to be decomposed, it was almost perfectly decomposed by the simultaneous treatment with ozone and UV irradiation.
