Photocatalytic degradation of brilliant red dye and textile wastewater.

The degradation of textile wastewater and brilliant red dye solutions in a coil photoreactor provided with recirculation, assisted by powdered TiO2 and medium-pressure mercury lamp irradiation, was investigated. Factorial design was used for the attainment of the best conditions for COD and color abatement. pH and TiO2 loading showed to be critical variables for the photocatalytic degradation process for both textile wastewater and aqueous reactive dye solutions (25 mg L(-1)). For both substrates, the optimized process conditions by factorial design were almost the same (pH 2-3, 444 mg TiO2 L(-1) loading, 5 L h(-1) recirculation flow-rate). A 41% COD abatement for textile wastewater was obtained with a 120 min treatment. For the Brilliant Red dye solutions, a 20 min treatment resulted in about 90% decolorization (517 nm, pH 5), as well as in a reduction of 66% of the integrated absorbance (200-600 nm, pH 5).