ABSTRACT: In this study, copper nanoparticles (Cu-NPs) were synthesized through a green and economic technique. The Centaurea cyanus plant extract was used as an appropriate reducing and stabilizing agent in this process. The synthesized nanoparticles were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray Powder Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and N2 adsorption porosimetry analysis. The analysis showed that the average size of spherical nanoparticles was around 11.9 nm, with 74.2 m2 /g and 0.36 cm3 /g mane surface area and pore size, respectively. Then, CuNPs were studied as a low-cost adsorbent to remove methylene blue (MB) dye from aqueous solutions. For this purpose, Central Composite Design (CCD) under the Response Surface Methodology (RSM) was applied to design the experiments, model the data and optimize the operating conditions. The effect of various operating parameters such as pH, MB initial concentration, adsorbent amount and contact time on the MB removal was practiced. Analysis of variance (ANOVA) showed a good agreement between the experimental data and the predicted ones obtained from the quadratic model. The optimum conditions for MB removal (63.20 %) were found at pH of 6.6, MB initial concentration of 30 mg/L, adsorbent amount of 0.15 g and time of 101.5 min. The results showed that the Langmuir isotherm with maximum adoption capacity of 21.9 mg/g and pseudo-second order kinetic models with rate constant of 0.359 (g/mg) (1/min) can properly legitimize the experimental data.
