Decolorization of a binary azo dyes mixture using CuO incorporated nanozeolite-X as a heterogeneous catalyst and solar irradiation

The photodecolorization of a mixture of the methylene blue and rhodamine B cationic dyes was studied using CuO/nano-zeolite X catalyst under solar irradiation. Nano-zeolite crystals were synthesized by hydrothermal crystallization. The photocatalyst was prepared by the calcinations process at 450 °C for 12 h followed by anion exchange process of the parent nano-zeolite NaX in a copper(II) sulfate aqueous solution (0.2 M) for 24 h. All samples were characterized by X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), BET and diffuse reflectance spectroscopy (DRS) methods. The particles sizes of the nano-zeolite NaX crystals were calculated in the ranges of 7-10 nm and 75-85 nm by XRD and SEM, respectively. The decolorization extent of the dyes in their mixture was measured spectrophotometrically at their respective λmax values. The decolorization kinetics was fitted well to the Langmuire-Hinselwood first order rate law. The effects of various operating parameters including pH, the amount of the catalyst, the amount of loaded CuO, the initial dyes concentrations, H2O2 and KBrO3 doses on the photodecolorization efficiency were studied at atmospheric conditions. The chemical oxygen demand (COD) experiments were performed at regular intervals to confirm the mineralization extent of the dyes.