We report the advances in the principal structural and experimental factors that might influence the carbon dioxide (CO 2 ) adsorption on natural and synthetic zeolites. The CO 2 adsorption is principally govern by the inclusion of exchangeable cations (countercations) within the cavities of zeolites, which induce basicity and an electric field, two key parameters for CO 2 adsorption. More specifically, these two parameters vary with diverse factors including the nature, distribution and number of exchangeable cations. The structure of framework also determines CO 2 adsorption on zeolites by influencing the basicity and electric field in their cavities. In fact, the basicity and electric field usually vary inversely with the Si/Al ratio. Furthermore, the CO 2 adsorption might be limited by the size of pores within zeolites and by the carbonates formation during the CO 2 chemisorption. The polarity of molecules adsorbed on zeolites represents a very important factor that influences their interaction with the electric field. The adsorbates that have the most great quadrupole moment such as the CO 2 , might interact strongly with the electric field of zeolites and this favors their adsorption. The pressure, temperature and presence of water seem to be the most important experimental conditions that influence the adsorption of CO 2 . The CO 2 adsorption increases with the gas phase pressure and decreases with the rise of temperature. The presence of water significantly decreases adsorption capacity of cationic zeolites by decreasing strength and heterogeneity of the electric field and by favoring the formation of bicarbonates. The optimization of the zeolites structural characteristics and the experimental conditions might enhance substantially their CO 2 adsorption capacity and thereby might give rise to the excellent adsorbents that may be used to capturing the industrial emissions of CO 2 .

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A study of carbon dioxide sequestration has been performed in aqueous electric arc furnace (EAF) and ladle furnace (LF) slag suspensions, in leached hydrated-matrixes, and in leachates to estimate their intrinsic sequestration potential at ambient conditions (temperature of 20 ( 1°C and atmospheric pressure). The CO 2 sequestration was tested in aqueous suspensions of steel slags at a liquid-to-solid ratio of 10 kg/kg as well as in leached hydrated-matrixes and leachates isolated from these fresh slag suspensions after three consecutive leachings. The sequestration assays were performed at 20°C with a flow rate of 5 mL/min of a CO 2 concentration of 15.00 vol %. The results have revealed that the CO 2 sequestration capacity of the LF slag suspension (24.7 g of CO 2 /100 g of slag) is 14 times superior to that of the EAF slag suspension. This greater CO 2 sequestration capacity of the LF slag suspension may be associated in large part to its higher content of portlandite, which reacts with CO 2 relative to the EAF slag suspension. Moreover, the separation of hydratedmatrixes and leachates significantly enhanced the CO 2 sequestration capacity of EAF slag while a slight decrease was observed for the LF slags. This may be due to an obstruction of the CO 2 binding sites of LF slag hydrated-matrixes following the accumulation of calcium carbonate. Taken together, these results suggest that EAF and LF slags could be used for the CO 2 sequestration and given a good yield as well in aqueous suspension as in separated matrixes and leachates.

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