Ultraviolet-induced Photoreduction of rhodamine 6G textile effluent catalyzed by annealed metamorphic Nano-CuO

Abstract

In the present investigation, nano-CuO catalysts with diverse metamorphic nanostructures, such as sphere-like, sponge-like, and flower-like, were scrutinized through a dropwise precipitation approach followed by annealing at various temperatures and durations. XRD analysis indicates that nano-CuO possesses a monoclinic crystalline phase structure (a = 4.691 Å, b = 3.423 Å, c = 5.145 Å, γ = 90^o). The UV–Vis absorbance spectra display an absorption band centered around 450 nm, which becomes stronger as the annealing temperature and duration rise. The FTIR spectra exhibit a prominent infrared band at 515 cm⁻¹ due to the stretching vibration of CuO bonds. Nano-CuO has initiated photoreduction of hazardous rhodamine 6G (R6G) textile effluent under ultraviolet (UV) irradiation. The reaction constant rates comply with pseudo-first-order kinetics, resulting in a 4-fold increase from 1.184 × 10⁻⁴ min⁻¹ to 4.408 × 10⁻⁴ min⁻¹, with the highest R² value of ≈ 0.99. The sponge-like porous nanostructure (<100 nm) with reduced bandgap, increased pore dimensions, and improved crystallinity enhances photocatalytic degradation rate and efficiency. The photocatalytic efficiency of current nano-CuO can still be optimized by increasing the optical source power or combining it with other metal-based catalysts for prospective sustainable wastewater remediation.