UV/TiO2 photocatalytic degradation of xanthene dyes

摘要

UV/titanium dioxide (TiO2) degradation of two xanthenedyes, erythrosine B (Ery) and eosin Y (Eos), was studied in aphotocatalytic reactor. Photocatalysis was able to degrade98% of Ery and 73% of Eos and led to 65% of chemicaloxygen demand removal. Experiments in buffered solutionsat different initial pH values reveal the pH dependence of theprocess, with better results obtained under acidic conditionsdue to the electrostatic attraction caused by the oppositecharges of TiO2 (positive) and of anionic dyes (negative).Batch activity tests under methanogenic conditions showedthe high toxicity exerted by the dyes even at low concentrations(~85% with initial concentration of 0.3 mmol L 1), butthe end products of photocatalytic treatment were much lesstoxic toward methanogenic bacteria, as detoxification of85 ± 5% for Eos and 64 ± 7% for Ery were obtained. Incontrast, the dyes had no inhibitory effect on the biogeniccarbonbiodegradation activity of aerobic biomass, obtainedby respirometry. The results demonstrate that photocatalysiscombining UV/TiO2 as a pretreatment followed by an anaerobicbiological process may be promising for the treatment ofwastewaters produced by many industries.