The CdS/g-C3N4 nano-photocatalyst: Brief characterization and kinetic study of photodegradation and mineralization of methyl orange

Abstract

The CdS/g-C3N4 hybrid was prepared mechanically and characterized by different techniques including XRD, SEM, DRS, FTIR, and cyclic voltammetry (CV). The SEM study showed that CdS nanoparticles (NPs) have been randomly dispersed on the surface of graphitic carbon nitride (g-C3N4). The CV results showed better charge carriers' transfer for the modified carbon paste electrode (CPE) by the CdS/g-C3N4 system concerning the modified CPE by single CdS or g-C3N4 modifier. The band gap (Bg) energies of 1.7, 2.7, and 1.9 eV were obtained from DRS results for CdS, g-C3N4, and CdS/g-C3N4 systems, respectively. The photocatalytic activity of the single and hybrid systems was tested towards methyl orange (MO). The degradation extents of 16%, 22%, and 34% were respectively obtained for CdS NPs, g-C3N4, and CdS/g-C3N4 systems at initial steps. To enhance the degradation efficiency, the mole ratio of the component was changed in the second step. The work was then focused on the kinetic study of both photodegradation and mineralization processes. For this goal, the degradation extents of the photodegraded MO solutions were calculated based on the recorded absorbance of the solutions in the visible-light and the results were then subjected to the Hinshelwood equation. Then the solutions were subjected to COD experiment to follow the mineralization extent of MO. Form the slopes of the Hinshelwood plots, the rate constants of 0.024 and 0.025 min−1 were obtained for the degradation and mineralization of MO molecules, respectively. TOC results confirmed the mineralization of 187.5 μmoles of MO molecules in a 50 ppm MO solution.