Photodegradation of Orange II under Visible Light Using Cu–Ni/TiO2: Influence of Cu:Ni Mass Composition, Preparation, and Calcination Temperature

Bimetallic Cu–Ni/TiO2 photocatalysts were prepared at different temperatures with varying Cu:Ni mass compositions. The photocatalysts were further calcined at selected temperatures. Characterization procedures were carried out on the photocatalysts to understand the correlation between the photocatalytic activity and the physicochemical and morphological properties. Results from the XRD, FESEM-EDX mapping, and HRTEM analyses were in favor of the metal particles existing in the form of well-dispersed oxides on TiO2 surface. The surface area of the photocatalysts was almost similar to the bare TiO2 ∼43 m2 g–1 except for 1Cu:9Ni-200-b observed with a higher surface area (53.8 m2 g–1) as compared to other photocatalysts. The photocatalyst performance of the bimetallic system is promising as compared to bare TiO2 and the monometallic photocatalysts. Results for photodegradation studies showed that 1:9 Cu:Ni mass composition was observed with 100% Orange II removal as compared to other Cu:Ni mass compositions. The 1Cu:9Ni-200-a photocatalyst prepared at lower temperature (8–10 °C) displayed 100% Orange II decolorization as compared to 1Cu:9Ni-200-b (prepared at higher temperature of 25 °C) with 65.1% dye removal. Although the results from UV–vis spectra showed the disappearance of the visible band (indicating 100% Orange II removal), TOC analysis indicated the presence of organic compounds derived from the dye degradation process. Therefore, longer irradiation time is required to break the chromophore groups in the degradation intermediates to obtain 100% TOC removal.