Oxidative Degradation of Allura Red Azo Dye in Aqueous Solution Catalyzed by Nb₂O₅

The degradation of Allura Red azo dye using niobium pentoxide (Nb2O5) as a catalyst and hydrogen peroxide (H2O2) as an oxidant was studied in a slurry batch reactor at 30°C. The effects of H2O2 concentration (45–180 mM), catalyst loading (0.25–0.75 wt%), and pH (3–11) were analyzed for 2 h. The highest color removal (81%) was achieved with 0.5 wt% Nb2O5, 180 mM H2O2, and pH 11. At pH 5, suitable for real effluents, removal efficiency reached 68% after 6 h. Hydroxyl radicals, responsible for degradation, were confirmed using a 2-propanol quenching test. The apparent activation energy was 56.3 kJ∙mol−1, and the data followed a pseudo-first-order kinetic model. The catalyst remained active after three cycles. Nb2O5 with H2O2 appears to be a promising system for azo dye removal in aqueous solutions.