Mechanism and performance evaluation of spent-coffee grounds-derived nanocomposite materials for highly efficient photocatalytic degradation of organic pollutant.

[Display omitted] • Hydrothermal carbonization of spent coffee grounds to prepare hydrochar samples. • Titania-based hydrochar-derived photocatalyst using a simple sol–gel method. • Effective degradation and mineralization of methylene blue dye in aqueous phase. • Superior performance of our photocatalytic system based on the metrics tools. The study demonstrates a facile and environmentally friendly method for synthesizing crystalline TiO 2 nanoparticles on the surface of hydrochar generated from readily available biomass waste, i.e., spent coffee grounds (SCGs), using a simple sol–gel process. The hydrochar served as a support for TiO 2 , reducing the rate at which electrons and holes recombine during photocatalysis, thereby facilitating the effective binding of TiO 2 , enhancing its adsorption capacity, and the convenient separation of the photocatalyst after usage. The materials were tested in the photocatalytic degradation of an organic pollutant, methylene blue (MB) dye. TiO 2 -hydrochar obtained at 210 ⁰C has the best performance, giving a degradation efficiency of 98.5 % and a mineralization efficiency of 87.1 % in 90 min at neutral pH. Radical trapping experiments showed O 2. - andh + being the dominant species, followed by HO.. Besides, it showed superior stability with an activity loss of ∼ 9.2 % after five runs. The superior performance of the HCT210 was ascribed to the enhanced interfacial charge transfer kinetics between the TiO 2 and hydrochar through Ti - O - C bond formation, better light absorption, and the high surface area of the materials. Performance metrics show that synthesized nanocomposites are promising photocatalysts, providing a biomass-assisted method for robust photocatalytic wastewater treatment. [ABSTRACT FROM AUTHOR]