Conditions for selective photocatalytic degradation of naphthalene in triton X-100 water solutions

Naphthalene is degraded selectively in surfactant Triton X-100 water solutions when treated with disperse TiO2 catalyst and UV-B simulated solar light. After complete degradation of the naphthalene, degradation of the Triton X-100 commences. The pseudo-first-order k(obs) values obtained for both naphthalene and Triton X-100 decrease with increasing Triton X-100 concentration. Experimental rate values fit the Langmuir-Hinshelwood equations. An apparent rate constant for naphthalene degradation k(N) = 17.3 ppm min(-1) and an adsorption equilibrium constant K-N = 0.009ppm(-1) are obtained from a plot of 1/k(obs) vs. naphthalene concentration. An apparent rate constant for Triton X-100 degradation k(T), calculated from a 1/k(obs) vs. Triton X-100 concentration plot of 1.1 ppm/min, was obtained. Therefore, the selectivity observed in naphthalene vs. Triton X-100 degradation is then due to the favorable naphthalene rate constant degradation that more than balances its unfavorable adsorption equilibrium on the TiO2 surface. This result is quite important to establish actual experimental conditions for treatment of sites contaminated with polyaromatic hydrocarbons (PAH). (c) 2005 Wiley Periodicals, Inc.