Simultaneous decolorization and detoxification of black reactive 5 using TiO₂ deposited over borosilicate glass

Objective. Removal and detoxification of azo dye by photocatalysis with TiO₂. Materials and methods. TiO₂ films were prepared by sedimentation at pH 1.3, using as support a borosilicate glass, annealed for 1 hour at 450 °C. Physical characterization was performed by Scanning Electron Microscopy, X-ray diffraction and UV/VIS spectrometry. Dye Black Reactive 5 removal was carried-out in a quartz photo-reactor. Results. Optical characterization revealed the films displayed evident TiO₂ spherical particles of various irregular sizes, porous, and without fractures. The average crystal size was 77.5 nm and 77.7 nm for 50 °C (dried temperature) and 450 °C (annealed temperature) respectively. The energy of the band gap (GAP) was 3.02 and 2.68 eV respectively. Maximum concentration of dye that negatively affected color removal was 80 mg/L (17%). At lower dye's concentrations (10, 50 and 70mg/L) decolorization was greater than 80%. TiO₂ films were reused for five consecutive cycles of 6 hours at 10 mg/L (>80%), and three cycles of 10 hours at 70 mg/L (> 80%). Toxicity results demonstrate that Daphnia magna was more sensitive than Lactuca sativa. Conclusions. TiO₂ films obtained by sedimentation demonstrated a high reactive black 5 decolorization and COD removal (86% and 100%), as well as toxicity reduction.