Nano modified kaolin-based materials and their application: A review

Kaolin, a natural clay mineral characterized by its kaolinite layers and silicate structure, exhibits high adsorbent properties, a low specific surface area, exceptional stability, and environmental friendliness. These attributes make kaolinite suitable for a wide range of applications. Conversely, the limited surface hydroxyl groups, low ion exchange capacity, and inability to absorb visible light indicate that pure kaolin or kaolinite is not an effective material for photocatalysis and performs inadequately in other applications. Fortunately, the unique physical and chemical properties of kaolinite render it as a suitable semiconductor carrier. By utilizing kaolin as a carrier, the poor activity, narrow spectral response, and limited electron transport of pure photocatalysts can be addressed, while also restricting the aggregation of nanoparticles. Thus, the usage of pure kaolin/kaolinite as a catalyst and adsorbent demonstrates to improve adsorption and catalytic performance, many modification techniques are now used, such as heat treatment (increases its surface area and porosity), acid modification (boosts the availability of active sites for improved adsorption and catalytic reactions), metal modification (introduces additional active sites), inorganic modification (improve thermal stability and photocatalytic performance), and organic modification (increase hydrophobicity). This review paper offers a structured overview of the use of kaolinite-supported nanocomposites across various applications, including adsorption, photocatalytic pollutant degradation, catalytic degradation, and antibacterial and antioxidant activities. The review also demonstrates the effectiveness and methods of combining nanomaterials with naturally occurring or modified kaolinite, as well as the limitations of kaolinite's present application and the mechanics underlying adsorption, catalytic, photocatalytic techniques and pollutant removal.