ABSTRACT
The ion exchange reaction between Ca-montmorillonite in a Nano form and copper ions is studied by the potentiometric methods using a glass electrode specific for copper ion determination at three different temperatures (20, 30 and 40°C).
Ca-Clay + Cu2+ ⇌ Cu- Clay + Ca2+
Enhancement of the copper on the nano-montmorillonite was recorded with increasing the Cu ion fraction in the solution. Increasing the reaction temperature had a negative effect on the concentration of Cu fraction on the solid phase.The isotherms results pointed out that adsorption of Cu2+ ions are preferred as indicated by the negatively charged free energy (ΔGo). The preference for the Cu2+ ions and their influence on the nano-montmorillonite as well as the high binding strength are elucidated by the negativity of the entropy (∆S◦) and ∆Sclay as well as the enthalpy (∆H◦) values. The adsorption reactions of Cu2+ onto the clay surfaces were exothermic in nature as indicated by the negative value of ∆H◦. The activity coefficient of the exchanged ions at different ionic fractions Ca:Cu in the solution are affected mainly by two factors included the distribution of the ions in the Gouy and Stern layers and the differences in the interlayer spacing according the solution composition.