Removal of copper ions from wastewater by adsorption onto a green adsorbent from winemaking wastes

Copper ion adsorption was studied using an activated carbon from winemaking wastes. The pH, temperature, activated carbon amount, and initial copper concentration were varied based on a full factorial 2 experimental design. Kinetic and thermodynamic studies were also performed. The adsorption kinetics followed a pseudo-second-order model. The adsorption data fit best to the Langmuir isotherm, compared with the Freundlich and Temkin models. The analysis of variance demonstrated that the pH and the activated carbon dosage had the greatest influences on the copper adsorption. The obtained activation energy suggested that the copper adsorption was physisorption. The best fit to a linear correlation was the moving boundary equation, which controls the kinetics of the adsorption of copper ions onto the activated carbon. X-ray photoelectron spectroscopy revealed the existence of different copper species (Cu, and Cu and/or Cu) on the surface of the carbonaceous adsorbent after the adsorption, which could suggest a simultaneous reduction process.
The authors would like to like to thank Dr. Irene Llorente of the National Center for Metallurgical Research, Spanish National Research Council (CENIM-CSIC), for performing the XPS measurements.