Fabrication of a novel ZnO/MMO/CNT nanohybrid derived from multi-cationic layered double hydroxide for photocatalytic degradation of azo dye under visible light

Abstract

With the purpose of the enhancement of photocatalytic performance in the visible region and efficient electron–hole separation, we reported a facile method for the synthesis of a mixed metal oxide/ZnO/CNT (MMO/ZnO/CNT) nanohybrid derived from ZnO/Co-Ni-Al layered double hydroxide (LDH) precursor. The structural and morphological aspects of the synthesized products were characterized by X-ray diffraction, scanning electron microscopy, UV/vis diffuse reflectance spectra, and FT-IR spectroscopy. The photocatalytic activity of the synthesized ZnO/MMO/CNT nanohybrid was investigated by photocatalytic degradation of C.I. Acid Red 14, as a model pollutant, under visible light irradiation. The photocatalytic activity of ZnO/MMO/CNT was also compared with TiO₂–P25, ZnO, and ZnO/Co-Ni-Al-LDH/CNT. The experimental results revealed that in comparison with other used photocatalysts, ZnO/MMO/CNT nanohybrid was an efficient photocatalyst under visible light irradiation. The effect of operational parameters including photocatalyst content, dye concentration, pH, and irradiation time on the photocatalytic removal efficiency of dye was investigated and optimized using response surface methodology approach. The photocatalyst dosage of 0.009 g, initial dye concentration of 20 mg L⁻¹, pH of 4.12, and irradiation time of 150 min were obtained as the optimum condition. In the proposed optimum condition, the catalyst reusability tests were carried out for five runs. Negligible decrease in degradation efficiency confirmed high potential of stability and reusability for the ZnO/MMO/CNT photocatalyst.