Removal of Copper and Nickel Ions from Aqueous Solution by Adsorption on Nanobentonite: Equilibrium, Kinetics, and Thermodynamics

Nanobentonite particles were used to investigate the elimination of nickel-(II) and copper-(II) at concentrations between 50 and 300 mg L^-1. Batch adsorption tests were conducted to examine the impacts of several factors, including pH, contact time, initial metal ions concentration, adsorbent dose, and temperatures. It was found that the first 20 min of metal ion removal was very fast, and the majority of the reaction was completed. The contact time was 30 min. The optimum pH was found to be 5.0 and 6.0 for copper-(II) and nickel-(II). We carefully evaluated how temperature affected the kinetics and equilibrium of adsorption on nanobentonite particles. The adsorption rate increased as the temperature rose, which is consistent with an exothermic process. The data were subjected to Langmuir, Freundlich, and Dubinin-Radushkevich isotherms at various temperatures. The best explanation for the data was found to be the Langmuir adsorption model. Adsorption kinetics has been investigated using pseudo-first and pseudo-second orders. The data fit best with a pseudo-second-order mechanism. Studies have been done on thermodynamic parameters including Δ<i>H</i>°, Δ<i>G</i>°, and Δ<i>S</i>°. FTIR spectra were used to study the role of functional groups on the surface of nanobentonite in removing heavy metal ions.