Comparative study on the photocatalytic efficiency of ZnO nanoparticles synthesized via chemical and eco-friendly coprecipitation methods

This study compares ZnO nanoparticles (NPs) synthesized via eco-friendly coprecipitation (ZnOE) using cactus juice and chemical coprecipitation (ZnOC). XRD analysis confirmed the high purity of ZnOC with a crystallite size of 18 nm, while ZnOE consisted mainly of zincite (ZnO) with an amorphous organic phase and trace amounts of albite (NaAlSi3O8) and calcite (CaCO3), with a smaller crystallite size than ZnOC: 15 nm. FTIR spectroscopy confirmed ZnO NPs formation in both methods and identified organic residues in ZnOE. The optical band gap of ZnO nanoparticles, calculated from the diffuse reflectance, was observed to be 3.2 eV for ZnOC and 3.14 eV for ZnOE, respectively. SEM and EDX analyses were conducted for further investigation. Both ZnOE and ZnOC were applied to the photocatalytic degradation of Basic Yellow 28 textile dye (BY28) under solar and artificial UV light. ZnOE exhibited superior photocatalytic performance in removing BY28 compared to ZnOC under both irradiation sources. Under optimal conditions (1 g L- 1 semiconductor, 10 mg/L BY28), ZnOE showed superior degradation rates: 100 % and 94.71 % under solar and UV light, respectively (rate constants: 0.0169 min-1 and 0.0127 min-1). ZnOC achieved 73.68 % and 42.61 % degradation under solar and UV light (rate constants: 0.007 min-1 and 0.0037 min-1). The treated BY28 solution demonstrated improved biodegradability and no phytotoxicity, indicating its environmental safety.