ZnO nanocomposites supported by acid-activated kaolinite as photocatalysts for the enhanced photodegradation of an organic dye

Nanocomposite photocatalysts have attracted considerable attention for their enhanced photocatalytic ability compared to single metal oxide photocatalysts. The matrix in a nanocomposite plays a vital role in determining the efficiency of a photocatalyst. Acid-activated kaolinite (AAK) provides an excellent matrix owing to its higher surface area. In the present study, two nanocomposites were prepared with varying compositions of ZnO and acid-activated kaolinite (AAK) for use as photocatalysts. The ZnO/AAK nanocomposites were prepared in a wet chemical precipitation method and characterized using a range of techniques. The photocatalysts were then used for the photocatalytic degradation of MB in an aqueous solution under UV irradiation. The reaction parameters affecting the photocatalytic efficiency, such as the pH of the solution, initial concentration of dye, and catalyst dose, were optimized. The recyclability of the nanocomposites was also evaluated. ZnO was synthesized and dispersed over the AAK matrix. The particle size of ZnO in nanocomposites was similar to 50 nm, and the optical bandgap of the nanocomposites was reduced significantly compared to single ZnO. Both AAK/ZnO nanocomposites exhibited high degradation efficiency. In particular, the ZK-30 nanocomposite, containing only 30 wt% ZnO, removed 98 % of MB from an aqueous solution. The recyclability test of the nanocomposites exhibited 80-99 % dye removal for up to three consecutive photocatalytic cycles.