Solar photocatalytic degradation of textile effluent with TiO 2 , ZnO, and Nb 2 O 5 catalysts: assessment of photocatalytic activity and mineralization

Abstract

The photocatalytic degradation of textile effluent was investigated using TiO₂, ZnO, and Nb₂O₅ 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⁻¹. 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_máx). Mineralization in terms of the formation of inorganic ions and toxicity reduction using bioassays with Artemia salina were performed. TiO₂ reduced the absorbance at 660 nm (λ_max) 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 Nb₂O₅ was very close to TiO₂-P25. In this sense, Nb₂O₅ becomes a promising alternative to replace the commercial TiO₂-P25. Bioassays confirmed the efficacy of treatment, increasing the lethal concentration of 27.59 (in natura) to 131.95% in the presence of Nb₂O₅.

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