Association of adsorption and heterogeneous photocatalysis in the degradation of Tartrazine yellow dye with CuNb2O6 synthesized and immobilized on chitosan membranes

This work presents the synthesis and characterization of the CuNb2O6 photocatalyst by the self-combustion method, in addition to its immobilization on chitosan polymeric membrane, and the optimized investigation of the association between the adsorption and heterogeneous photocatalysis processes over visible light radiation in the degradation of the Tartrazine yellow dye. Industries use the tartrazine yellow dye extensively, which remains in large quantities in their wastewater, a potential environmental contaminant. This study enabled an interdisciplinary analysis and the development of a promising methodology for the degradation of this substance in industrial effluents. The characterization process of the synthesized CuNb2O6 allowed the verification of an alternative synthesis route for this photocatalyst with high purity, high crystallinity, and good crystalline homogeneity. The characterization of the immobilized CuNb2O6 allowed us to verify an excellent immobilization morphology on the chitosan membrane by the casting method with a bandgap equal to 1.45 eV, which enables the use of visible radiation in the activation of the photocatalyst. Performed the statistical analysis with the support of the Doehlert matrix to study the influence of pH and CuNb2O6 concentration during the photocatalytic reaction; the optimization results point to pH conditions equal to 7.34 and CuNb2O6 concentration equivalent to 2.27 g L−1. The immobilized photocatalyst was efficient and promising in the degradation of Tartrazine yellow dye by using an associative process between adsorption/photodegradation, with a reduction of 94% of chromophore compounds (430 nm) and a reduction of 86% of aromatic compounds (260 nm), and a similar percentage after six cycles of reuse, in the central regions of UV–Vis electronic transitions of the Azo dye under study.