چكيده به لاتين
Today, the tendency to use metal-organic frameworks (MOFs) has increased due to their high surface area and variable structure in adsorbing flue gas from fossil fuel power plants. The aim of this work is to synthesize MOF adsorbent based on zirconium and its composite with graphene oxide (GO) in order to adsorb CO2 in a batch reactor and to optimize the adsorbent through post-synthesis modification to improve the adsorption capacity. The structural characteristics of the adsorbents have been presented by various techniques such as FTIR, XRD, FE-SEM, TGA and BET. Then, for optimization, the experiment design method was used with three factors of temperature, pressure and mass percentage of composite composition as input variables and adsorption percentage (mmol/g) as response. After determining the optimal conditions by calculating the mean square deviation and analysis of variance (temperature 27.183 ˚C, pressure 8.719 bar and mass percentage 15.394, adsorption capacity 12.287 mmol/g as the answer), the optimal sample was synthesized. In addition, experiments have been conducted to investigate the isothermal, kinetic and thermodynamic models of adsorption by the optimal adsorbent. For the optimal adsorbent, the isotherm model is in accordance with the Freundlich isotherm model, which indicates multilayer adsorption on the heterogeneous sites of the adsorbent surface. The study of kinetic models showed that in the optimal adsorber, fractional order and second order kinetic models at selected temperatures of 298, 318 and 338 K provide the best fit to CO2 absorption data, which indicates the simultaneous existence of physical and chemical absorption in the process. Finally, the feasibility of the adsorption process has been checked using thermodynamic modeling, and the values of Enthalpy, Entropy and Gibbs free energy are equal to -19.903 Kj/mol, -0.034 Kj/mol, and Kj /mol was obtained from -9.692 to -8.321 in the entire selected temperature range and 5 bar, which indicates that the adsorption process is exothermic and spontaneous. And finally, for the optimal adsorbent, the results related to the calculation of the selectivity factor of IAST showed that the selectivity factor of 119 was obtained in the combination of 85:15 CO2/N2, pressure of 1 bar and temperature of 298 K.
