Kaolinite-Based Hybrid Photocatalysts: TiO2/Reduced Graphene Oxide System for Degradation of Dyes and Pharmaceuticals

The persistent presence of dyes and pharmaceuticals in water presents significant environmental and health risks, as these pollutants are often resistant to conventional treatment methods. Photocatalysis with Titanium Dioxide (TiO₂) has been extensively used for the degradation of these pollutants; however, its narrow band gap and fast charge recombination limit its practical use. In recent years, several studies have focused on the use of kaolinite, a low-cost and abundant type of clay, for synthesising composite photocatalysts to enhance their performance. This paper highlights the recent development of kaolinite-based photocatalytic materials in terms of structure, preparation, and working principles. Kaolinite’s layered structure, abundant hydroxyl groups, and surface charge facilitate efficient charge transfer and adsorption of pollutants. The review also highlights how kaolinite composites can be modified to improve their responsiveness to visible light. Hybrid materials have demonstrated increased effectiveness in pollutant degradation, hydrogen production, and bacterial disinfection, outperforming single-component semiconductors. While laboratory studies show promising results, challenges remain in scaling up production, understanding charge transfer at interfaces, and developing more environmentally friendly methods. The review suggests that further research is needed to optimise the development of cost-effective, durable kaolinite-based photocatalysts for large-scale contamination remediation. Hybrid photocatalysts composed of kaolinite, particularly those incorporating TiO₂ and Reduced Graphene Oxide (rGO), have shown great promise in degrading dyes, pharmaceuticals, and other recalcitrant water pollutants. The unique layered structure and surface chemistry of kaolinite enable efficient pollutant adsorption and uniform dispersion of semiconductor nanoparticles, leading to enhanced charge separation and photocatalytic activity under visible light.