Natural zeolite supported g-C3N4/ZnO/Ag3PO4 composite: A tandem n-n heterojunction for simultaneous photodegradation of dyes under visible and solar irradiation

Abstract

Various zinc-based ternary composite photocatalysts with variable weight percent ratios of g-C3N4:ZnO/Ag3PO4 in pristine and natural zeolite supportedform were prepared using precipitation and solid-state methods, respectively. X-ray diffraction (XRD), Brunauer, Emmett, and Teller (BET), Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX), Thermogravimetric analysis (TGA/DTA), Fourier Transform Infrared (FTIR), Ultraviolet–Visible Diffuse Reflectance (UV–Vis DRS), and Photoluminescence (PL) techniques were used to investigate the as-produced composites. The photocatalytic efficacy of the developed materials was studied considering methyl orange dye (MeO) and laboratory-prepared mixed dyes as target pollutants. The photodegradation (MeO) performance of the natural zeolite-supported (NZGZA-1) ternary system was found to be 87.1% under optimal working circumstances. The primary active species engaged in MeO decolorization were the holes. The photodegradation efficiency under outdoor experiment yielded 98.2 and 78.9 %, for MeO and mixture of dyes respectively. After five consecutive cycles, the reusability of the supported catalyst was examined, and a 47.2 % decline was recorded at the end of the fifth cycle showing the fairly well stability of the catalyst. The photocatalytic degradation of the studied model pollutant follows pseudo-1st-order kinetics. The present work evidenced beneficial use of natural zeolite as support to ternary photocatalyst systems with enhanced efficiency apart from meeting the criteria for circular economy. Thus, reusing of spent natural zeolite as a support for composite photocatalysts could be considered viable alternative to disposing the same to the environment.