Comparative photocatalytic degradation of Eosin Yellow and Orange II dyes using Ag–NiO/ZnO nanocomposite: Extending catalyst applicability to azo pollutants

The widespread release of synthetic dyes like Eosin Y and Orange II into water bodies from industrial processes presents significant environmental and health concerns, primarily due to their chemical stability, persistence, and resistance to standard wastewater treatment techniques. In our previous study, a silver nickel oxide modified zinc oxide (Ag-NiO/ZnO) nanocomposite synthesized via hydrothermal technique demonstrated outstanding photocatalytic degradation of Eosin Y under ultraviolet light, achieving 95 % removal with a pseudo-first-order rate constant of 0.0160 min⁻¹. Building upon this, the present work investigates the same nanocomposite (previously examined using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and ultraviolet visible diffuse reflectance spectroscopy) for the degradation of Orange II, a structurally distinct azo dye. Under visible light irradiation, the catalyst achieved 94.4 % degradation of Orange II within 60 min, with a comparable rate constant of 0.0161 min⁻¹. The enhanced photocatalytic activity across both dye systems is attributed to the synergistic effects of silver surface plasmon resonance, nickel oxide zinc oxide heterojunction formation, and efficient charge separation. This comparative approach illustrates the broad-spectrum pollutant removal capability of Ag– NiO/ZnO, highlighting its potential for azo dye remediation.