Eco-Friendly Synthesis of Copper Nanoparticles for Efficient Congo Red Dye Removal from Wastewater

Abstract

Water pollution, exacerbated by industrialization and agricultural practices, necessitates effective and sustainable treatment solutions. Conventional wastewater treatment methods often fall short due to high costs and inefficiencies. Nanotechnology, particularly copper-based nanoparticles (Cu and CuO NPs), has emerged as a promising alternative due to their high surface area, catalytic properties, and antimicrobial effects. This study explores the biosynthesis of Cu and CuO NPs using Citrus aurantium extract and evaluates their efficiency in removing Congo Red dye from wastewater. Cu and CuO NPs were synthesized using an aqueous extract of Citrus aurantium as a reducing and stabilizing agent. Characterization was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), zeta potential measurements, and Brunauer-Emmett-Teller (BET) surface area analysis. The dye removal efficiency was assessed using spectrophotometry, and adsorption behavior was analyzed through isotherm models and kinetic studies under varying experimental conditions. XRD confirmed the formation of crystalline Cu and CuO NPs. SEM images revealed aggregation, while FTIR confirmed organic capping agents. CuO NPs exhibited a higher surface area (7.34 m²/g) than Cu NPs (3.19 m²/g), leading to superior initial dye removal efficiency. Adsorption followed the pseudo-second-order kinetic model and was thermodynamically favorable. This study demonstrates the potential of Citrus aurantium-derived Cu and CuO NPs as eco-friendly and effective agents for wastewater treatment. CuO NPs excel in single-use applications, whereas Cu NPs offer better stability over multiple reuse cycles, providing a sustainable approach for environmental remediation.