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The photocatalytic degradation of textile effluent was investigated using TiO, ZnO, and NbO catalysts under solar irradiation. The procedures were carried out at ambient conditions in April 2014, with pH 3.0 and catalyst concentration of 0.250 g L. The photocatalytic activity of the oxides was evaluated by means of kinetic efficiency (rate constant and half-life time), chemical oxygen demand reduction, and absorbance reduction at 228, 254, 284, 310, 350, 500, and 660 nm (λ). Mineralization in terms of the formation of inorganic ions and toxicity reduction using bioassays with Artemia salina were performed. TiO reduced the absorbance at 660 nm (λ) after 300 min of solar irradiation around 94 and 93%; and 68 and 60% of COD, respectively. ZnO showed lower photocatalytic activity giving 64 and 42% of absorbance and COD reduction, respectively. The photocatalytic activity of NbO was very close to TiO-P25. In this sense, NbO becomes a promising alternative to replace the commercial TiO-P25. Bioassays confirmed the efficacy of treatment, increasing the lethal concentration of 27.59 (in natura) to 131.95% in the presence of NbO.

The present work investigated the degradation of a dyeing factory effluent by advanced oxidative process under UV irradiation. TiO and ZnO were used as catalysts and the influence of different concentrations of HO added to the system was studied. The catalysts were characterized in terms of crystal structure (X-ray diffraction), textural properties (Brunauer-Emmett-Teller area and pore volume) and point of zero charge, which indicated the semiconductors had a positively charged surface in an acidic medium. After 8 h of irradiation at pH 3.0 and catalyst concentration of 0.0625 g L, the effect of HO was evaluated by means of kinetic efficiency (rate constants), absorbance reduction (at 284, 621 e 669 nm), total organic carbon reduction and mineralization (in terms of the formation of ions such as [Formula: see text] and [Formula: see text]). Adding HO to the photocatalytic system significantly increased pollutants' removal, highlighting tests with 1.0 × 10 mol L, showing higher absorbance reduction and rate constants at 621 and 669 nm for TiO and best mineralization rates for ZnO. Ecotoxicity bioassays using Artemia salina L confirmed the treatment efficacy, with effluent lethal concentration (LC) increasing from 65.68% (in natura) to over 100% after photocatalysis treatment.