Promotion effect of ZnO on the photocatalytic activity of coupled Al2O3-Nd2O3-ZnO composites prepared by the sol − gel method in the degradation of phenol

Abstract The photocatalytic activity of coupled Al 2 O 3 -Nd 2 O 3 -ZnO composites (Al-Nd-Zn- x ; where x  = 0.8, 1.2, 2.0, 5.0, and 15.0 wt% of ZnO) prepared by the sol-gel method was studied in the photo-degradation of phenol in aqueous medium. The Al-Nd-Zn- x composites were characterized by physical adsorption of N 2 , XRD, TEM, SEM, Raman, UV–vis, XPS and fluorescence spectroscopies. Al-Nd-Zn- x composites with ZnO concentration in the range 0.8–2.0 wt% showed high efficiency to photo-convert phenol and mineralize dissolved organic carbon to CO 2 with UV light irradiation. The Al-Nd-Zn-1.2 composite was the material with the highest efficacy to photodegradate phenol in aqueous medium photo-converting about 90.0% of phenol and mineralizing 75.0% of dissolved organic carbon after 3 h of UV light. It is proposed that the intimate contact between Al 2 O 3 , Nd 2 O 3 and ZnO phases of the coupled Al-Nd-Zn- x composites are beneficial characteristics for the separation of the photogenerated charge carriers in order to decrease the recombination rate of photogenerated electron-hole pairs. These Al-Nd-Zn- x composites are characterized by a high BET specific surface area and a bimodal pore size distribution which are excellent characteristics for the adsorption and diffusion of phenol molecules to the active sites resulting in enhanced photocatalytic properties for the degradation of phenol in aqueous medium.