Therefore, the calculated ΔHo which is about 20 kJ/mol suggests that the CO2 adsorption is physisorption, and consistent with the reduction in amount of CO2 adsorbed at an elevated temperature (as shown in Figure 4). On the other hand, the ΔGo values are divided into two regions, in which one at low temperature (25-50 oC) with a negative value and the other one is at high temperature range (75-120 oC) with a positive value. The negative sign of ΔGo at low temperature indicates an occurrence of the favorable and spontaneous adsorption, whilst positive value at an elevated temperature implies a non-spontaneous adsorption reaction [30, 34]. In addition, decreased in negative ΔGo value with increasing temperature implies that the CO2 adsorption process is more favorable at 25oC rather than at 50oC [32].