J. Ortiga

Selective gas adsorption by amorphous clay mineral derivatives

Amorphous derivates prepared by aqueous reaction of various aluminosilicate clay minerals with concentrated KF solution at 80–110°C were studied for their gas adsorption properties. The four clay minerals studied are halloysite, a well-crystallized kaolinite, a poorly crystallized kaolinite, and a montmorillonite. The gases tested are N2, O2, CH4, CO, CO2, and C2H2. The kaolin-group mineral derivatives are characterized by substantial reduction in particle size, high specific surface, and significant selectivity towards CO2 and C2H2 relative to the other gases. The montmorillonite derivative shows no increase in adsorption over the starting material, however, for all the materials high adsorption of CO2 and C2H2 was observed. Levels of gas adsorption and gas adsorption ratios are comparable to pillared clays.

Selective gas adsorption by metal exchanged amorphous kaolinite derivatives

Metal exchanged amorphous kaolinite derivates are studied for their gas adsorption properties. The kaolinite derivatives were prepared by aqueous reaction of the clay with concentrated KF solution at 80–110°C. The K+ ions were then exchanged by Cs+, Sr2+, La3+, Fe3+ or Cu2+. Fe(II)- and Cu(I)-containing derivatives were prepared by reduction under H2. The gases tested were N2, O2, CH4, CO, CO2, and C2H2. Correlations between gas retention and various physical and chemical variables are investigated. Gas retention levels normalised against BET surface show that level of adsorption is at least partly determined by surface chemical composition. The highest gas retention levels per unit area are achieved for alkali metal exchanged derivatives or alternately for exchange cations with the largest ionic radius.

SO2 gas adsorption by modified kaolin clays: Influence of previous heating and time acid treatments

Modified kaolin clays were used as adsorbents for SO(2) gas adsorptions. The clays were heated up to 900 °C previous to acid treatments with 0.5 N sulfuric acid solutions at boiling temperature during different times up to 1440 min. Equilibrium adsorption at 25 °C and 0.1 MPa was carried out by using a volumetric apparatus. The samples were characterized by chemical analysis, X-ray diffraction and infrared analysis. The heating of the clays followed by acid treatment improved the adsorption capacity of the kaolin clays. The presence of amorphous silica and hydroxyl in the final products improved SO(2) adsorption capacity. Better properties for SO(2) adsorption were found in kaolin rich in not well ordered kaolinite clay mineral.

Swelling of TMA(tetramethylammonium)- and HDP(hexadecylpyridinium)-montmorillonites in water and toluene media: influence of the type montmorillonites

Organo-clays were prepared by exchange cations of the montmorillonite with tetramethylammonium (TMA)- and hexadecylpyridinium (HDP)-chloride. Two different montmorillonite types were studied. Two amounts of each organic substances (1 and 4 cation exchange capacity times of montmorillonite) were contacted with each montmorillonite clay for 1 and 24 h. The solids were characterized by X-ray diffraction and swelling index. The swelling was measured in water and toluene media. The structural characteristics of montmorillonites changed after organo treatment and showed different behaviour in water and toluene media. The type of montmorillonite, the organic cation intercalates (TMA, HDP) and condition of treatment influenced in the different swelling in water and toluene media.