Optimization of photocatalytic degradation of methyl orange using immobilized scoria-Ni/TiO2 nanoparticles

Abstract

In this study, the photocatalytic efficiency of scoria-Ni/TiO2 nanoparticles is evaluated for methyl orange removal under both the ultraviolet (UV) and sunlight irradiations. The synthesized catalysts are characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectra (DRS), scanning electron microscope (SEM), and energy dispersive X-ray analysis (EDAX) analysis. According to the results, the absorption edge of TiO2 alternated to visible light successfully, and the SEM and EDAX analysis approved that the particles, which are in nano-size, doped on the scoria. The effect of pH, catalyst dosage, methyl orange concentration, and contact time on efficiency was assessed. The initial experiment revealed that 0.05% and 0.1% of nickel have more efficiency while using the sun and UV light sources, respectively. In a 50-ml lab-scale reactor, methyl orange removal efficiency by scoria-Ni/TiO2 was 95.89 and 93.97% under UV and sunlight irradiation, respectively, within 45 min contact time while it was 26.7 and 45.9% under the sun and UV light irradiation, respectively, for commercial TiO2. In addition, the reaction kinetics followed the Langmuir–Hinshelwood model. Finally, radical production and catalytic activity of Ni/TiO2 verified by significant decrease in removal efficiency due to surface and solution radical scavengers addition.