Photodegradation enhancement of 2-chlorophenol using ZnO–CdS@CS nanocomposite under visible light

Abstract

A facile micro-emulsion method used to prepare zinc oxide–cadmium sulfide (ZnO–CdS). Then, chitosan (CS) is utilized as a polymer matrix. Fourier-transform infrared spectroscopy, X-ray diffraction spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, dynamic light scattering, and photoluminescence is applied to evaluate the chemical structure, surface morphology, and the optical properties. Thermal gravimetric analysis is done to estimate the stability of the prepared nanomaterials. The photocatalytic activity of the synthesized nanoparticles was investigated via high-performance liquid chromatography analysis toward 2-chlorophenol degradation under visible light. Obviously, the spectrum of UV–visible for ZnO–CdS@CS nanostructure demonstrates a shift to longer wavelength (red shift) than the other prepared materials with the lowest band gap energy (2.10 eV). Also, the photocatalytic degradation of ZnO, ZnO@CS, ZnO–CdS, and ZnO–CdS@CS is 80%, 84%, 88%, and 98%, consecutively. The pseudo-first-order rate constant (K) for ZnO, ZnO@CS, ZnO–CdS, and ZnO–CdS@CS is 0.0039 min−1, 0.0048 min−1, 0.0058 min−1, and 0.0108 min−1, respectively. The CdS NPs and CS matrix (carbon and nitrogen “C–N”) introduce supplementary energy levels for excitation that causing a decrease in the band gap, increasing the extent of photodegradation in the visible region and assist for electron–hole separation. The reusability studied ZnO–CdS@CS manifested degradation under the same condition.