Application of diatomite as a renewable natural carrier for TiO2 and (Ti,Ru)O2 photocatalysts for synergistic adsorption-photocatalytic elimination of Rhodamine B dye

The development of sustainable photocatalytic systems for wastewater treatment remains a key challenge in environmental engineering. In this study, natural diatomite was utilized as a green, porous biogenic silica support for TiO 2 and (Ti,Ru)O 2 photocatalysts, enabling the design of hybrid materials that integrate adsorption and photocatalytic degradation in a single platform. The hierarchical structure of diatomite promotes efficient adsorption of Rhodamine B (RhB), while the deposited TiO 2 phases provide strong oxidative capability under UV irradiation, resulting in a pronounced synergistic adsorption–photocatalysis effect. Structural and surface characterization (XRD, SEM-EDX, BET, FTIR) revealed that the amorphous SiO 2 framework of diatomite stabilizes nanoscale TiO 2 domains and inhibits excessive anatase-to-rutile transformation, leading to favourable catalytic properties. Photocatalytic experiments demonstrated efficient RhB removal, with the highest degradation efficiency achieved at an optimal catalyst loading of 10 mg for the TiO 2 system. Kinetic analysis based on the Langmuir-Hinshelwood model confirmed pseudo-first-order behaviour, with a maximum apparent rate constant of k = 0.0335 min -1 . The incorporation of Ru further modified the catalytic performance, highlighting the role of doping on charge separation and interfacial processes. The results demonstrate that catalyst performance is governed by the interplay between adsorption capacity, crystallite size, pore structure, and catalyst loading. The proposed diatomite-supported system represents a promising option of photocatalytic platform for the removal and decomposition of dye pollutants from water under controlled conditions.