Propyl paraben removal using Cu₂O/ZnO-NPs photocatalyst elaborated via green method

The aim of the present work is to investigate the photocatalytic degradation of propyl paraben (propyl para-hydroxybenzoate, PrP) using Cu₂O-ZnO-NPs photocatalyst followed by the identification of the oxidation by-products. The Cu₂O-ZnO-NPs material, synthesized using a green chemistry approach, was used as a photocatalyst for the removal of PrP. The nanoparticles were characterized by XRD, XRF, diffuse reflectance spectroscopy, ATG/DTG, FTIR, SEM-EDX, BET and FRX techniques. The XRD results showed that Cu₂O-ZnO-NPs have a nanometer size of 24.13 nm. The DR-UV analysis showed that Cu₂O-ZnO-NPs has an E_g of 2.35 eV which corresponds to the absorption of visible light. The SEM-EDX analysis showed that the ZnO has a hexagonal structure while the CuO has a monoclinic structure. The effect of variables such as propyl paraben concentration (PrP), hydrogen peroxide concentration (H₂O₂), catalyst dose, and the reaction temperature on the pseudo-first order reaction rate constant (k_app) of the reaction was evaluated. It was found that the degradation of PrP was governed by hydroxyl radical °OH attack and the pathways consisted of a cascade of reactions. The optimum photocatalytic degradation was obtained with an initial catalyst dose of 50 mg, pH 7, and PrP concentration of 10 mg/L. When the photocatalyst was irradiated, a significant PrP degradation was observed after 30 min of irradiation. The results suggest that Cu₂O-ZnO-NPs act as a good photocatalyst for PrP degradation under visible light.