Experimental and DFT study of Cu(II) removed by Na-montmorillonite

Abstract

The experimental and theoretical studies on the adsorption of Cu(II) on the surface of Na-montmorillonite (Na-Mt) were reported. Effects of batch adsorption experimental parameters were studied. Density functional theory and molecular dynamics simulations were used to study the adsorption of Cu(II) on montmorillonite (001) surface. The adsorption reached equilibrium within 80 min and the adsorption capacity was 35.23 mg·g−1 at 25 °C. The adsorption data of Cu(II) were consistent with pseudo-second-order kinetics and Langmuir isotherm models. The adsorption process was dominated by physical adsorption (Ea was 37.08 kJ·mol−1) with spontaneous endothermic behavior. The influence of coexisting cations on the adsorption capacity of Cu(II) was Mg(II) > Co(II) > Ca(II) > Na(I). The simulation results demonstrated that there were no significant differences in the adsorption energy of Cu(II) at the four adsorption sites on the montmorillonite (001) surface. Cu(II) had more electron transfer than Na(I). The diffusion coefficient of Cu(II) in the aqueous solution system containing montmorillonite was 0.85×10−10 m2·s−1. Considerable amounts of Cu(II) ions were adsorbed at a distance of 0.26 and 2.25 Å from the montmorillonite (001) surface. The simulation results provided strong supporting evidence for experimental conclusions. HIGHLIGHTS The experimental and theoretical studies were used to study the mechanism of Cu(II) adsorption by Na-Mt.; Adsorption of Cu(II) by Na-Mt was a monomolecular process and spontaneous process.; Hirshfeld group analysis revealed a strong electrostatic attraction between Cu(II) and the surface of montmorillonite(001).; The mechanism of adsorption of Cu(II) by Na-Mt was confirmed as ion exchange and electrostatic attraction.;

Keywords

• adsorption
• cu(ii)
• molecular dynamics simulation
• montmorillonite