Comparative study of the UV and UV/VUV-induced photolysis of phenol in aqueous solution

The UV (254 nm) and UV/VUV (254/185 nm) photolysis of phenol and the distribution of the products in solutions saturated with oxygen or nitrogen were investigated and compared. The initial rate of degradation of phenol in UV/VUV-irradiated solutions exceeded that determined in UV-irradiated solutions, but the difference decreased dramatically with increase of the initial phenol concentration. The effects of methanol as HO scavenger demonstrated that the relative contribution of the HO-based reactions to the decomposition of phenol in UV/VUV-irradiated solutions decreased strongly with increase of the initial phenol concentration. The same aromatic (1,2- and 1,4-dihydroxybenzene) and aliphatic (maleic, malic, tartaric and oxalic acids) intermediates were detected in UV- and UV/VUV-irradiated solutions saturated with oxygen. The decompositions of 1,2- and 1,4-dihydroxybenzene, 1,4-benzoquinone and oxalic acid were also investigated both in UV/VUV- and in UV-irradiated solutions.