Paper Title
A Semi-Empirical Model To Predict Adsorption Equilibrium Of Carbon Dioxide On Ammonia Modified Activated Carbon

The adsorption equilibria of carbon dioxide on a commercial granular activated carbon (GAC) and an ammoniamodified GAC (OXA-GAC) were investigated over the temperature and pressure range of 303 to 333 K and up to pressures of 1 atm. To distinguish the contribution of chemisorption and physisorption mechanisms to the overall CO2 adsorption, we developed a semi-empirical equilibrium model. A non-linear regression method was employed to estimate the best fitting parameters corresponding to the isotherm model. An analysis of the calculated statistical parameters indicated that the proposed model successfully fit the experimental data over the entire analyzed ranges of temperature and pressure. The initial isosteric enthalpy of adsorption calculated using the Clausius–Clapeyron equation indicated a sharp increase in CO2– adsorbent interaction after ammonia modification of the untreated adsorbent, consistent with a dramatic uptake of CO2 at low partial pressures. The heats of adsorption calculated using the temperature-dependent parameters of the proposed model for physisorption and chemisorption of CO2 onto the modified adsorbent were in excellent agreement with the heats of adsorption obtained from the experimental data. Keywords- Activated carbon, Ammonia modification, CO2 adsorption, Adsorption isotherm, Toth equation, Isosteric enthalpy.