Photocatalytic performance of ZnO immobilized on bentonite for catalytic degradation of malachite green under sunlight irradiation

Malachite green (MG) is a cationic triphenylmethane dye widely used for its bright colour and antimicrobial properties. Despite its utility of MG poses significant environmental and health concerns due to its persistence, toxicity, and potential carcinogenicity, particularly affecting the aquatic ecosystem. This study presents the eco-friendly hydrothermal synthesis of zinc oxide/bentonite nanocomposite using Millettia ferruginea leaf extract as a natural reducing and stabilizing agent. The photocatalytic performance of the nanocomposite was evaluated for the degradation of MG dye in aqueous solutions under sunlight irradiation. The synthesized nanocomposite was characterized by XRD, Uv–Vis, SEM, FTIR, TGA, and EDS. Photocatalytic activity was evaluated under natural sunlight, with various operational parameters examined, including dye concentration, catalyst dosage, temperature, and pH. Under Optimal conditions (20 mg/L MG concentration, 20 mg catalyst load, 50 °C, and pH 6), a maximum removal efficiency of 98 % was achieved. Reusability studies confirmed the catalyst's stability with degradation efficiencies of 98 %, 96 %, 95 % and 84 % across four successive cycles. XRD analysis confirmed the presence of the crystalline wurtzite hexagonal phase(spacegroupP63mc) of ZnO with an average particle size of 14.6 nm. TGA analysis exhibits excellent thermal stability, with minimal mass loss of 3.07 %. To identify the dominant reactive species involved in the photocatalytic process, radical scavenging experiments were also performed. Overall, the synthesized nanocomposite reveals strong potential as a sustainable and reusable photocatalyst for the effective treatment of dye-containing wastewater.