Photocatalytic wet peroxide assisted degradation of Orange II dye by reduced graphene oxide and zeolites

Background Photocatalytic degradation of Orange II (OII) dye has been carried out with commercially available materials, namely sodium Y zeolite (NaY), ammonium Y zeolite (NH4Y), and reduced graphene oxide (RGO). The catalysts were characterized by N2 adsorption at −196 °C, pH at the point of zero charge (pHpzc), and ultraviolet/visible (UV/Vis) diffuse reflectance absorbance. The initial screening of processes like adsorption, oxidation with hydrogen peroxide alone, direct photolysis, combination of H2O2 with the catalyst, and/or with UV/Vis radiation has been done. For the process with better performance (radiation combined with the oxidant and using the materials as photocatalysts), a parametric study was carried out to evaluate the effect of pH, H2O2 concentration, catalyst dose, radiation intensity, and radiation type (UV/Vis or visible radiation) in OII degradation and mineralization. Results The screening demonstrated that radiation plays an important role in the hydroxyl radical formation and, inherently, in the oxidation of OII and in the mineralization of the organic compounds formed. Still, for all catalysts tested, the existence of optima in terms of pH (2.0), catalyst dose (100 mg L−1), and H2O2 concentration (6 mM) was found, while the maximum radiation intensity (500 W m−2) and UV/Vis radiation incidence benefits the oxidation process. However, the best process performance was achieved when using the catalyst that absorbs more radiation (RGO), yielding OII and TOC removals of 97.7% and 87.9%, respectively, after 90 min of reaction time. Conclusion Taking into account the great performance reached, a possible application of such catalysts in the treatment of textile dyeing effluents is anticipated. © 2020 Society of Chemical Industry (SCI)