Oxidation of polynuclear aromatic hydrocarbons in water .3. UV radiation combined with hydrogen peroxide

Oxidation in water of three polynuclear aromatic hydrocarbons (PAHs), fluorene, phenanthrene, and acenaphthene, with UV radiation combined with hydrogen peroxide has been studied. The effect of hydrogen peroxide concentration, pH, and bicarbonate ion has been investigated. Disappearance rates of PAHs are substantially increased with respect to those from UV radiation alone if proper conditions of hydrogen peroxide concentration and pH arc!established. Direct photolysis contribution decreases with the increasing hydrogen peroxide concentration and is the main way of degradation at acid pH (76% at pH 2 with 10(-3) M hydrogen peroxide concentration, for fluorene oxidation). Rate constants of reactions between the hydroxyl radical and PAHs were found to be 9.9 x 10(9), 8.8 x 10(9), and 13.4 x 10(9) M(-1) s(-1), for fluorene, acenaphthene, and phenanthrene, respectively. Both UV radiation and UV/H2O2 oxidation of PAHs yield numerous intermediate compounds. Most of these compounds disappear as oxidation time is increased.