Photocatalytic degradation of chlorazol yellow dye under sunlight irradiation using Ce, Bi, and N co-doped TiO₂ photocatalyst in neutral medium

Abstract

Chlorazol yellow (CY) is a commonly used anionic, toxic, mutagenic, and potentially carcinogenic azo dye, which is menacing to the environment, aquatic system, food chain, and human health as well. To remove CY dye molecules from an aqueous medium, a series of Ce, Bi, and N co-doped TiO₂ photocatalysts were prepared by varying the composition of the dopants. Under sunlight irradiation, the resultant 5 wt% (Ce-Bi-N) co-doped TiO₂ composite catalyst was found to show the best catalytic activity. Hence, the required characterization of this catalyst was performed systematically using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. From the thorough investigation, it is revealed that the CY molecules reached adsorption–desorption equilibrium onto the surface of the catalyst within 30 min following second-order kinetics. Herein, the catalyst attained 97% degradation when exposed to sunlight at neutral (pH ~ 7, [CY] = 5 mg L⁻¹) medium. The developed catalyst can destruct CY molecules with a maximum rate of 23.1 µg CY g⁻¹ min⁻¹ and the photodegradation kinetics follows first-order kinetics below 23.5 mg L⁻¹, a fractional order between 23.5 and 35.0 mg L⁻¹, and a zeroth order above 35.0 mg L⁻¹ of CY concentration. Finding from scavenging effect implies that ${\mathrm{O}}_{2}^{-}$ and ${\mathrm{OH}}^{\bullet }$ radicals have significant influence on the degradation. A suitable mechanism has been proposed with excellent stability and verified reusability of the proposed photocatalyst.