PARAMETERS AFFECTING THE HOMOGENEOUS AND HETEROGENEOUS DEGRADATION OFQUINOLINE SOLUTIONS IN LIGHT-ACTIVATED PROCESSES

The light-activated degradation kinetics of quinoline were studied in detail on Hg lamp and Suntest solar-simulated irradiation. Fenton-phot oassisted mineralization in homogeneous solution with a peroxide to qu inoline ratio of approximately 50 (quinoline, approximately 1 mM) was complete in about 30 min on Hg lamp irradiation. Reactions activated b y a solar simulator led to 80% mineralization of the same quinoline so lutions within the same time period due to a lack of a strong UV compo nent. Heterogeneous photocatalytic TiO2-mediated degradation proceeded at a slower rate than the homogeneous reaction. The influence of a nu mber of factors, such as the substrate concentration, solution pH, gas atmosphere and dynamics of H2O2 addition, was investigated. The stoic hiometry of the mineralization reaction was analysed as a function of the gas atmosphere used. Quinoline degradation was possible via dark a nd light-activated reactions. Quinoline did not affect the H2O2 consum ption rate in the presence of Fe3+ ions. This suggests that, during de gradation, the reaction of Fe3+ ions with H2O2 is the rate-determining step. Quinoline did not complex with Fe3+ ions in the dark. However, complex formation occurred during photodegradation with Fenton-like re agents, such as Cr6+ or CU2+ ions and combinations of Cu2+ + Fe3+ ions , in the presence of H2O2. The latter systems were compared with the c lassical Fenton reagent leading to quinoline mineralization. (C) 1997 Elsevier Science S.A.