Photocatalytic degradation of real textile wastewater using carbon black-Nb2O5 composite catalyst under UV/Vis irradiation.

This work investigated the impregnation of Nb2O5 into carbon black (CB) in different ratios and its effect in photocatalytic degradation of real wastewater from a dyeing factory by advanced oxidative processes (AOP). Synthesized catalysts were characterized regarding their crystalline structure (DRX, micro-Raman), morphology (MEV), textural (BET area) and optical properties (bandgap energy by diffuse reflectance) and pH at the point of zero charge (pHpzc). Preliminary tests showed better photodegradation results in the acidic medium after 5 h of irradiation with NCB-0.5 (Nb2O5:CB 0.5:1). Treatment parameters optimization was carried out using response surface methodology based on Box-Behnken experimental design. Catalyst concentration, solution pH and irradiation time were varied, analysing absorbance reduction (285 and 574 nm), COD and TOC removal after treatment as responses. The composite catalyst showed improved photocatalytic activity, attributed to an increase in adsorption capacity and the bandgap narrowing, redshifting the absorption edge wavelength to the visible region, brought by CB impregnation. Optimal conditions were found at 0.250 g L-1 of catalyst, pH 2.0 and 5 h of irradiation, removing 72.19% and 93.52% of absorbance in 285 and 574 nm, respectively, 51.29% of COD and 70.70% of TOC using NCB-0.5.