Abstract:

Coal gasification slag is a solid waste generated during coal chemical production and accounts for a notable proportion of solid wastes. Leveraging the natural properties (e.g., high specific surface area and pore volume) and compositional characteristics (rich in carbon) of coal gasification slag, this study used the mechanical ball milling method to composite coal gasification slag using a conventional photocatalyst titanium dioxide (TiO₂) for broadening the photocatalytic response range of TiO₂. Dye wastewater was used as the treatment object to evaluate the photocatalytic performance of the resulting composite material. Characterization techniques such as X-ray diffraction, Fourier Transform infrared spectroscopy, and scanning electron microscopy were used to investigate the optimal process conditions for the catalytic degradation of a methylene blue (MB) solution by the TiO₂/coal gasification slag composite material. Results show that under visible-light conditions, the degradation efficiency of the developed composite material (TiO₂∶slag ratio of 90∶10) is higher than those of anatase TiO₂, P25, and the coal gasification slag/P25 composite material. Infrared characterization and free-radical quenching experiments indicated that coal gasification slag and TiO₂ effectively bonded through Ti—O—Si bonds, expanding the photocatalytic response range of TiO₂ and increasing the photocatalytic reaction contact area. In addition, hydroxyl radicals were identified as the primary active substances responsible for degrading MB. Compared with anatase TiO₂, the catalytic efficiency of the composite material increased by 4.96 times. Furthermore, its catalytic degradation efficiency remained above 90% after three cycles, indicating that the TiO₂/coal gasification slag composite material has excellent degradation efficiency and stability.

Key words: coal gasification slag, titanium dioxide (TiO₂), visible light, photocatalysis, dye wastewater