Ascorbic Acid Mediated Ecofriendly Synthesis of Copper Nanoparticles for Statistically Optimized Adsorptive Removal of Reactive Navy Blue 19 Dye

Abstract

This study focuses on the green synthesis of copper nanoparticles (CuNPs) using L-ascorbic acid as a reducing and stabilizing agent. The synthesized nanoparticles were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). The point of zero charge (pHₚzc) was determined to assess the surface neutrality of the nanoparticles. These CuNPs were applied as efficient adsorbents for the removal of Reactive Navy Blue (RNB) dye from aqueous solutions. The adsorption process was optimized using Response Surface Methodology (RSM) based on a four-factor, five-level Central Composite Design (CCD). Under optimized conditions, a maximum dye removal efficiency of 99.79% was achieved. Experimental validation of the model, replicated six times, yielded a relative standard deviation (%RSD) of 0.0652 and a mean error of 0.1441%, confirming the model’s accuracy. Analysis of variance (ANOVA) demonstrated the statistical significance of both the overall model and individual parameters. Error analysis revealed that the Freundlich isotherm and pseudo-second-order kinetic models best described the adsorption process. Thermodynamic studies confirmed the spontaneous and feasible nature of dye adsorption onto CuNPs. The results suggest that this green and cost-effective approach offers a promising solution for the treatment of dye-contaminated industrial wastewater.