Surface Photochemistry: on the Search of Efficient Photodegradation Methods for Indigo Dyes Through Advanced Oxidative Processes

Abstract

PP-29-115 Background/Aims: Immobilization of TiO2 layers on glass and Modified Fenton test of the effect of advance oxidative processes on photocatalytic degradation of indigo blue. Particularly TiO2 photocatalysis and Fenton are known for being nonselective processes able to mineralize recalcitrant chemicals. Methods: A TiO2 emulsion was prepared, mixing 12 g TiO2, 4 mL H2O and 0.4 mL acethylketone for 10 minutes. Then, 25 mL H2O and 0.2 mL Triton X-100 were added. After proving that TiO2 deposited on glass effectively enhances the photodegradation of adsorbed indigo, we test various continuous flow and batch reactors, with and without TiO2 adsorbed on internal reactor wall, using different irradiation sources. Modified Fenton approaches are also being tested. Results: TiO2-coated glass enhances photodegradation of adsorbed indigo and dye absorption totally disappears after 6 hours irradiation with 125 watts Hg lamp; approximately 40% of color disappears in the first 1 hour. We tested continuous flow and batch reactors also on treatment of dye liquid streams (with or without TiO2 on internal reactor wall) using lamps. In TiO2 absence, there is no indigo degradation. Irrespective reactor or irradiation source used, very low % of degradations (<10%) with TiO2 introduction in the system. Fenton-based processes gave more promising results, with more than 50% color removed in about 0.5 hour. The problem of iron residue removal remains to be solved. Conclusion: To date, only Fenton-based methodologies seem to be able to remove the indigo blue color from those model waters.