E RADICATION of heavy metals from water and wastewater is vital in relation of public health. Copper is discharged to the environment through the unwise use of the agrochemicals and the industrial activities such as the dying and mining industry. Recently clay and nanoclay exhibited efficacy as sorbent of heavy metals. This study was conducted to analyze the thermodynamic characters of the Cu(II)/Ca(II) interactions on Ca-nano-montmorillonite to elucidate and enhance the viability of using nanoclay minerals as an effective sorbent material in reducing the bioavailable of copper, thus, reducing their environment risk. 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 Cu 2+ ions are preferred as indicated by the negatively charged free energy (ΔG o). The preference for the Cu 2+ 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 ∆S clay as well as the enthalpy (∆H •) values. The adsorption reactions of Cu 2+ 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.