The adsorption equilibria of CO 2 on zeolite 13X and zeolite X/activated carbon composite (Zeocarbon) were measured by a static volumetric method. The equilibrium experiments were conducted at (273.15, 293.15, 313.15, 333.15, and 353.15) K and at pressures up to 102.0 kPa for zeolite 13X and 99.7 kPa for Zeocarbon. The experimental data obtained were correlated by the Toth, UNILAN, and Sips models, which are generally used for microporous adsorbents such as zeolites and activated carbon. The isosteric enthalpies of adsorption were calculated for CO 2 on both adsorbents.
IntroductionThe emission of CO 2 from power plants that burn fossil fuels is a major reason for the accumulation of CO 2 in the atmosphere, which causes long-term environmental problems. 1 Recently, much attention has been paid to the global warming effect caused by the excessive emission of CO 2 into the atmosphere. 2 Separation can play a key role in alleviating this problem, and the adsorption of gases and vapors by microporous solids has attracted much attention because of its great practical importance in the fields of gas separation, gas purification, and environmental problems. Therefore, adsorption is one of the most effective methods for the separation of emitted CO 2 .Information concerning the relevant adsorption equilibria is generally an essential requirement for the analysis and design of an adsorption separation process. 3 For practical applications, the adsorption equilibria must be known over a broad range of operation temperatures. Also, the isotherms of pure species are fundamental information for the dynamic simulation of adsorbers. 4 Furthermore, it is important to select the proper adsorbent for the design of an efficient adsorption process.Whereas fossil resources are limited, biomass as an adsorbent is an inexpensive, renewable, and environmentally friendly additional resource that can be found readily all over the world. 5 Recently, a zeolite X/activated carbon composite (Zeocarbon) was synthesized from rice hulls that can be used in packed beds in pelletized form. However, little information is available in the literature concerning the adsorption of any components on Zeocarbon at various temperatures.Zeocarbon was selected as an adsorbent in this study, and adsorption isotherms for CO 2 on Zeocarbon were measured and compared with those for CO 2 on zeolite 13X, which were measured previously. 6,7 In this study, commercial adsorbent pellets of zeolite 13X and Zeocarbon were used instead of crystals. The experimental data obtained at various temperatures were correlated with existing adsorption isotherm models such as the Toth, UNILAN, and Sips models.
