Industrial dye usage results in substantial wastewater discharge, posing environmental and health hazards. Hence, developing efficient, sustainable, and cost-effective treatment technologies is crucial. Photocatalysis using TiO₂ has emerged as a promising approach for dye degradation. This study explores the photocatalytic removal of methylene blue (MB), a model dye pollutant, using a composite of biomass-derived carbon nanoparticles (CNPs) and nanosized TiO₂ under UV light. The CNPs were synthesized via one-step pyrolysis from waste coffee leaves, offering a sustainable carbon source. The resulting CNPs (CL-10) and the TiO₂-CNP composite (PC@CL-10) were thoroughly characterized using advanced techniques. Incorporating carbon significantly reduces the band gap of TiO₂ from ∼3.2 eV to 2.90 eV, enhancing photocatalytic activity. Degradation studies under varying catalyst doses, dye concentrations, and pH levels demonstrate effective MB removal under UV irradiation. Photocatalytic experiments revealed up to 99% degradation of MB under UV light, while tests conducted in the dark showed negligible activity, confirming the light-dependent efficiency. Kinetic analysis indicated that intra-particle diffusion (IPD) governs the dye degradation process. Moreover, recyclability tests over seven cycles showed consistent performance with minimal decline, highlighting the catalyst's stability and reusability. These findings suggest that PC@CL-10 is a highly effective, low-cost photocatalyst with strong potential for large-scale wastewater treatment applications.
Sharma et al. (Mon,) studied this question.