Efeito do suporte na degradação fotocatalítica de efluente têxtil

Abstract

Textile effluents are potential polluting agents. These effluents contain toxic organic compounds, with characteristic color, which are recalcitrant and difficult to remove by conventional treatment. Due to the large volume of textile effluents, to their diverse composition, and to the peculiarity of their treatment techniques, Advanced Oxidation Processes (AOPs) have become a promising alternative for the treatment of these effluents, particularly heterogeneous photocatalysis. This work aimed at applying heterogeneous photocatalysis in the treatment of synthetic (Reactive Blue 222 dye solution, at concentrations of 10 and 100 mg.L-1) and raw textile effluents, using artificial UV-Vis radiation (250 W for 5h) and catalysts: 5 and 10% (m/m) Nb2O5 and ZnO, supported on activated carbon and zeolite NaX, and TiO2 (with and without thermal treatment), ZnO, and Nb2O5, immobilized on glass slides. The supported and immobilized catalysts were first characterized to identify the structural, textural, and morphological properties. The catalysts were then used in the photocatalytic degradation of synthetic dye solution at different concentrations (10 and 100 mg.L-1). The photocatalysts that presented better performance were used in the treatment of raw textile effluent from industrial laundry. Among the studied oxides, ZnO/NaX was the most efficient photocatalyst. 10% ZnO/NaX reached 99% decolorization and 81% degradation of the 10 mg.L-1 synthetic dye solution after 5 h of reaction. The photocatalyst with 10% Nb2O5/NaX reduced color by 96% and the 10 mg.L-1 dye solution was 44% mineralized. Diluted solutions were more easily degraded, following pseudo-first order kinetics, whereas the degradation of concentrated solutions was lower, with apparent zero order kinetics. The photocatalysts 5% and 10% ZnO/NaX and 10% Nb2O5/NaX also showed good results in the degradation of raw effluent from industrial laundry. Among these, 10% ZnO/NaX decolorized the textile effluent by 89% and mineralization reached 80%. The tests with catalysts impregnated on glass slides showed similar photocatalytic performance for ZnO, TiO2 without heat treatment, and TiO2 calcined at 1000°C for 10 hours. However, ZnO was more effective than TiO2 in decolorizing the dye: about 93% and 63% for 10 and 100 mg.L-1, respectively.