Adsorption of Co(II) on nanobentonite surface:Kinetic and equilibrium studies

Abstract

The ability of selected adsorbents such as nano bentonite to remove Co (II) ions from wastewater at different conditions as contact time, amount of adsorbent, temperature, initial concentration, and pH has been studied and reported. In order to find out thermodynamic and kinetic parameters, equilibrium adsorption models have been applied. Although experimental datais confirmed with both Langmuir and Freundlich isotherm models. Adsorption rate constant has been determined from Lagergren Equation and pseudo-second order  Equations.
Freundlich model has a better correlation coefficient (R²) than the Langmuir model for the studied concentrations at 25°C also Tempkin isotherm is applied. Another important result withdrawn from the values of thermodynamic parameters can be stated as, negative value of ΔG° and positive value of the ΔS° show that the adsorption of Co(II) ions onto both adsorbents is a spontaneous process and positive value of ΔH° indicates that the adsorption is endothermic in nature. Finally, it can be seen that the pseudo-second order equation provide the best correlation coefficient (R²) for the adsorption data.