Photocatalytic Degradation of Synozol Navy Blue Dye by Ni-Cu-Ag Dopped ZnO: An Insight Into Photoluminescence, Scavenging, Mechanism and Kinetic Aspects

Abstract

Cost-effective, sustainable, and eco-friendly strategies are crucial for treating organic pollutants in industrial wastewater. ZnO is a promising photocatalyst due to its affordability, environmentally benign nature, and ability to fully mineralize pollutants. However, its limited effectiveness under visible light is a major drawback. Ni doping helps reduce charge carrier recombination, enhancing the photocatalytic activity of ZnO. Ni-Cu co-doping increases saturation magnetization by creating intrinsic defects, though it can lead to nanocluster formation on the catalyst surface. Ag further improves the performance by preventing nanocluster aggregation and prolonging charge carrier lifetimes. In this study, Ni-Cu-Ag@ZnO nanoparticles were synthesized via the sol-gel method and used as a photocatalyst for the degradation of Synozol navy blue dye. Characterization techniques like FTIR, SEM, XRD, EDX, BET, UV, and PL confirmed the nanocomposite structure and morphology. The Ni-Cu-Ag@ZnO nanocomposite achieved 88% photodegradation efficiency under optimal conditions (a contact time of 50 min, an initial dye concentration of 75 ppm, a catalyst dosage of 0.03 g, and an acidic medium with a pH of 2). The rate constants, k₁ (2 × 10^-2 min^-1) suggest that the degradation of Synozol navy blue by Ni-Cu-Ag@ZnO under ordinary light follows pseudo-first-order kinetics. Scavenging tests further confirmed that the enhanced photocatalytic degradation was driven by the generation of OH^• radicals, with the addition of hydrogen peroxide playing a key role in preventing electron-hole recombination. This indicates that the quantity of hydroxyl radicals and their adsorption on the photocatalyst are crucial in determining the extent of degradation. This study highlights the potential of Ni-Cu-Ag@ZnO nanocomposites for industrial wastewater treatment and opens new avenues for the further enhancement of the photocatalytic efficiency of other catalysts under consideration.

Keywords: Ni‐Cu‐Ag doping; Synozol navy blue; nanoparticles; photocatalytic degradation; sol–gel method.