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The distribution of amino groups on amino-functionalized SBA-15 materials for CO 2 adsorption was studied by Transmission Electron Microscopy (TEM) in combination with a staining technique using RuO 4 in order to analyse the influence of the aminated organic chains location on the CO 2 adsorption properties. Mesostructured aminofunctionalized SBA-15 materials were obtained by co-condensation, grafting and impregnation using aminopropyl, AP (N), ethylene-diamine, ED (NN), diethylenetriamine, DT (NNN) and polyethyleneimine, PEI, as functionalizing agents. CO 2 adsorption isotherms of functionalized samples at 45 ºC showed that both the adsorption capacity (mg CO 2 /g ads) and the efficiency of amino groups (mol CO 2 /mol N) depend on the functionalization technique and the amount of organic compound used. While samples synthesized by co-condensation showed negligible CO 2 uptake and efficiency, adsorbents prepared by grafting and impregnation presented significant CO 2 adsorption capacities but a dissimilar efficiency. Key differences in the location of aminated chains explained the performance of CO 2 capture for every adsorbent, being grafted samples the adsorbents where amino groups were better distributed, favouring the CO 2 diffusion trough the whole structure.

Adsorption of inorganic mercury(II) from an aqueous solution on mercaptopropyl-functionalized SBA-15 mesoporous silicas has been investigated. Adsorbents were prepared by the cocondensation method using tetraethoxysilane and different quantities of (mercaptopropyl)trimethoxysilane. Pluronic P123 was employed as a structure-directing agent. Mercury adsorption isotherms at 20 °C are reported for every synthesized material. The maximum mercury loading has been obtained from Langmuir fitting. Stoichiometric ratios of 1:1 S-Hg have been observed in all cases. Adsorbents were extremely efficient in removing inorganic mercury from an aqueous solution with a maximum in mercury loading of ca. 2.9 mmol of Hg g -1 for the material with the higher organic content. The effect of the pH on mercury adsorption has been studied. The efficiency of the adsorbents has been found to remain almost constant from neutral pH up to 3 M nitric acid concentration.

Adsorption of pure CO 2 on amine-functionalized SBA-15 mesoporous silica materials has been studied. Adsorbent materials were prepared by grafting the silica surface with aminopropyl (AP), ethylene-diamine (ED) and diethylene-triamine (DT) organosilane molecules. Materials so obtained were dried under air atmosphere at 110°C and at room temperature. CO 2 adsorption isotherms were carried out at 45°C, showing that grafted materials are very efficient for CO 2 removal at atmospheric pressure when samples are dried at 20 8 C. However, when the drying step is carried out at 110°C in air, CO 2 adsorption capacity is low. DRIFTS analysis has shown that amino groups can undergo oxidation to oxime or imine species during drying. Adsorption capacity of the materials was found to be unchanged after some consecutive adsorptiondesorption cycles, being the regeneration step performed at 110°C under vacuum.

A functionalization method based on the impregnation of previously grafted pore-expanded SBA-15 is presented. The combination of tethered and mobile amino groups has led to a synergic effect, yielding samples with CO 2 uptakes up to 235 mg CO 2 per g (5.34 mmol CO 2 per g) at 45 C and 0.15 bar CO 2 and high adsorption efficiencies.

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