UV-Responsive Er-Doped NiAl2O4/Mn/GO Nanocomposites: Green Synthesis and Photocatalytic Degradation of Organic Pollutants via Fluorescent Behavior for Water Purification

Synthetic dye-induced water pollution poses considerable environmental challenges, underscoring the urgent demand for novel and sustainable remediation strategies. In this context, the present study introduces an eco-friendly synthesis approach for Er-doped NiAl₂O₄/Mn/GO nanocomposites, employing rhubarb extract as a natural capping agent to enhance the process's sustainability. Various synthesis techniques, including microwave irradiation, co-precipitation, ultrasonic treatment, and hydrothermal processes, were rigorously investigated to determine their impact on the morphological features, physicochemical attributes, and fluorescence behavior of the resulting nanocomposites. Comprehensive characterization was performed using advanced analytical methods such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) surface area analysis. The photophysical characteristics of the nanocomposites were investigated, emphasizing their fluorescence response under UV irradiation. A band gap value of 3.2 eV highlighted their promising photocatalytic activity under ultraviolet light exposure. The photocatalytic efficiency, assessed against Acid Black 1 dye, demonstrated effective degradation capabilities. Radical scavenger experiments utilizing p-benzoquinone, benzoic acid, and EDTA offered valuable insights into the underlying degradation mechanisms. The ultrasound-assisted synthesis technique exhibited superior photocatalytic efficiency, achieving a remarkable 94.59% degradation of dye within 60 min utilizing 40 mg of the nanocatalyst. These findings underscore the significant potential of Er-doped NiAl₂O₄/Mn/GO nanocomposites, characterized by their enhanced fluorescence properties, as efficient and sustainable photocatalysts for the effective elimination of organic pollutants from wastewater.