<p>The present study investigated a novel and environmentally friendly method for producing ZnO nanoparticles as a catalyst using extracted citrus bergamia leaf and zinc acetate precursor. Activated carbons (ACs) were also prepared from cassava peel to use as a support for ZnO nanoparticles. The AC preparation method involved impregnation with ZnCl₂ at varying ratios (0.75:1–2.5:1), followed by carbonization for 1–3 h at temperatures ranging from 450 to 650 °C. The findings revealed that the impregnation ratio and carbonization temperature significantly affected the pore characteristics of the carbon, but the activation time had no discernible effect on the pore structure of the activated carbon. The optimized activated carbon exhibited a surface area of 1250 m²/g, a pore volume of 0.195 cm³/g, an average pore size of 0.128 nm, and an average particle size of approximately 107 nm. These results were achieved at a carbonization temperature of 533 °C, a time of 1.82 h, and an impregnation ratio of 1.6. Additionally, the bandgap of the ZnO nanoparticles was measured to be approximately 3.17 eV. The specific surface area of the ZnO-NPs modified by extraction from a citrus bergamia leaf sample was 371m²/g, and the average crystallite size was found to be 35 nm. These measurements corresponded to a hexagonal particle at a temperature of 450 °C and a time of 2 h. The catalyst demonstrated photocatalytic efficiency for degradation of tetracycline of approximately 99% Based on the results, the developed ZnO-NPs impregnated activated carbon exhibit good potential for practical applications such as photocatalysis.</p> Graphical Abstract <p></p>