Study on preparation of UV-CDs/Zeolite-4A/TiO2 composite photocatalyst coupled with ultraviolet-irradiation and their application of photocatalytic degradation of dyes.

In this work, ultraviolet irradiation was employed to assist in the preparation of a novel photocatalyst composite in the form of carbon dots/zeolite-4A/TiO 2 , using coal tailings as the source of silicon-aluminum and carbon. The composite was designed for the degradation of methylene blue under 500 W of UV light irradiation. Zeolite-4A was used as a support for the well-dispersed carbon dots and TiO 2 nanoparticles. The as-prepared composites were subjected to thorough characterization, confirming the successful formation of zeolite-4A with a cube structure, along with the loading of TiO 2 and coal-based CDs in the composites. The experimental results demonstrated that the UV-CZTs nanocomposites exhibited a remarkable removal efficiency of 90.63% within 90 min for MB. The corresponding rate constant was exceptionally high at 0.0331 min−1, surpassing that of the Dark-CZTs and pure TiO 2. This significant enhancement was possibly due to the synergistic effect of adsorption photocatalysis of the UV-CZTs, combined with the excellent electron-accepting capabilities of the coal-based CDs, which led to highly improved charge separation. An investigation of the spent photocatalyst's recyclability revealed that it retained a remarkable 82.94% MB removal efficiency after five consecutive cycles, signifying the stability of the composite. Trapping experiments also elucidated the primary reactive species responsible for MB degradation, which were identified as photo-generated holes and ⸱O 2 − species. By this process, the hydroxyl radicals generated in the system successfully promoted the transformation of coal tailings to coal-based zeolite and coal-based CDs. Coal-based zeolite served as an excellent carrier of titanium dioxide, which improved its dispersibility. The inhibition of e−-h+ recombination of titanium dioxide by introducing coal-based CDs improved the photocatalytic ability of titanium dioxide. Through this study, coal tailings, as a coal processing waste, were transformed into high-value materials, and relevant photocatalytic composite materials could be prepared with broad application prospects. • A novel preparation method of the composite photocatalysts assisted with ultraviolet-irradiation were proposed. • UV-CDs/Zeolite-4A/TiO 2 composite photocatalysts were prepared using coal tailings as silicon-aluminum source and carbon source. • UV-CDs/Zeolite-4A/TiO 2 were the most stable and reusable because zeolite-4A confined TiO 2 on its surface. • The ternary structure of CDs-Zeolite-TiO 2 enhanced the photocatalytic performance of UV-CDs/Zeolite-4A/TiO 2. [ABSTRACT FROM AUTHOR]