Enhancement of CO2 adsorption performance with the chitosan-modified activated carbon by different methods

Carbon dioxide (CO2) has almost become synonymous with greenhouse gases. Neither improvement of energy efficiency nor the application of alternative energy can reduce the concentration of CO2 to the allowable concentration. Therefore, CO2 must be captured to prevent its escape into the atmosphere. CO2 is commonly adsorbed by activated carbon because of the good affinity between them. In this study, to enhance the CO2 adsorption performance of this material, activated carbon was modified by two ways, synthesis and grafting with chitosan, to examine how the adsorption performance was affected by the different modifications. The experimental results showed that the adsorption performances of activated carbon with grafted chitosan and synthesized with chitosan were better than that of activated carbon. Although the nitrogen content was higher in the activated carbon synthesized with chitosan than in the carbon grafted with chitosan, the adsorption enhancements were similar due to the reduced surface area of the former. In addition, the results of the multi adsorption-desorption processes showed that the adsorption performance of the activated carbon grafted with chitosan slightly decreased, while that of the activated carbon synthesized with chitosan was almost unchanged. As the heterogeneous adsorption was modeled well by the Toth adsorption isotherm model, this isotherm model was used to model the experimental data for comparison with the Freundlich adsorption isotherm model. The average deviation of adsorption uptake fitted by the Toth adsorption isotherm model was about 3.07%, in comparison with 12.71% fitted by the Freundlich adsorption isotherm model.