2.4. Static adsorption
The experimental apparatus used the static volumetric method previously reported in Khunpolgrang et al. [31]. The main components of the apparatus were an adsorption cell and a
loading cell. Approximately 1 g of each adsorbent was placed in the adsorption cell. The adsorbate (e.g. CO2) was introduced into the loading cell, and after the pressure and temperature in the loading cell stabilized, the adsorption step was carried out by allowing the
gas to expand to the adsorption cell. Pressure measurements were made in the range of 20–500 kPa and temperature measurements in the range of 40–70 C. The adsorption equilibrium state was
considered to have been achieved when the temperature and the pressure of the system were constant.