Theoretical evaluation of pillared clay adsorbents: Part I. The microporosity of Al- and Ti-pillared montmorillonite

Maes, N.; Heylen, I.; Cool, Pegie; Bock, Maarten De; Vanhoof, Christine; Vansant, Etienne F.

doi:10.1007/bf01135361

Cited by 15 publications

(9 citation statements)

References 25 publications

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“…These amounts are very large, if it is considered that the maximum number of Al 13 pillars permitted by steric contraints when pillaring saponite has been calculated as 0.17 pillars per unit cell (one pillar per 5.9 cells) (Bergaoui et al, 1995a,b). We found no estimates for the size of the [(TiO) 8 (OH) 12 ] 4+ polycations (Maes et al (1996) have approximated them to cubes of TiO 2 ), and although these polycations may be smaller than the Al 13 units, the amounts reported here are still very large. Besides, if all Ti is present as the proposed [(TiO) 8 (OH) 12 ] 4+ units, the charge of such polycations would compensate four times the charge of the CEC of the clay.…”

Section: R E S U L T S a N D Discussioncontrasting

confidence: 57%

“…The polymerization of Ti has been carried out using different Ti precursors, the most extended being TiCl 4 (Sterte, 1986;Bernier et al, 1991;Khalfallah Boudali et al, 1994;Maes et al, 1996;Bahranowski et al, 1996;Cheng et al, 1996). Hydrolysis of this species is carried out in a highly acidic medium (usually 5 M HCl), and heating the solutions to 50 608C or to re ux conditions is usually necessary to obtain clear solutions.…”

Section: Introductionmentioning

confidence: 99%

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Influence of the Ti precursor on the properties of Ti–pillared smectites

et al. 2001

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The pillaring of smectites (two saponites and a montmorillonite) with various Ti precursors was studied. The minerals were intercalated with ‘classical ’ Ti precursors, such as titanium tetrachloride and titanium tetraethoxide, and also with new precursors, such as solutions of titanium tetraisopropoxide in acetic acid, or titanium (bis (ethylacetoacetato) diisopropoxide) in acetone. A complete characterization of the intercalated solids was carried out and a comparison of the properties of the solids as a function of the precursors used in the intercalation established. The influence of the severe conditions in which the intercalation with Ti oligomers is usually carried out (low pH and/or high temperature) on the properties of the intercalated solids was analysed. Intercalation with TiCl4 and Ti(EtO)4 strongly affected the structure of the clays, not by acid attack on the octahedral sheet, but mainly by disaggregation of particles. Ti(isop)4 was found to be less aggressive for the clays, while Ti(etacet)2(isop)2 did not form pillared solids but organo-clays, and therefore was of no use as a pillaring agent. The solids were thermally stable up to 300°C, showing a high specific surface area.

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Section: R E S U L T S a N D Discussioncontrasting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Influence of the Ti precursor on the properties of Ti–pillared smectites

et al. 2001

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“…Here, the most important results in terms of porosity have been found for samples synthesized using 0. 29 1 and 2, respectively).…”

Section: Resultsmentioning

confidence: 94%

Influence of water on the pillaring of montmorillonite with aminopropyltriethoxysilane

Ahenach¹,

Cool²,

Vansant³

et al. 1999

Phys. Chem. Chem. Phys.

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Silica pillaring of montmorillonite has been carried out using aminopropyltriethoxysilane (APTS) as pillaring precursor. Several synthesis parameters, i.e. reaction temperature, reaction time, concentration of components, etc., are of importance in this synthesis. However, the concentrations of APTS and under which the H 2 O hydrolysis is performed have a paramount e †ect on the molecular structure and the degree of polymerization of the pillaring precursors, and therefore, also on the porosity of the obtained silica intercalated clay. X-ray di †raction (XRD) analysis and di †use reÑectance infrared Fourier transform (DRIFT) spectra reveal that the presence of water in the system is one of the most important parameters in the reaction sequence. These results are reÐned and conÐrmed by transmission electron microscopy (TEM). Combining the results of all the applied techniques, two types of APTS interaction with the clay can be observed : internal and external adsorption depending on the conditions used. Besides the inÑuence of the water concentration, the inÑuence of the use of templating ions (cetyltrimethylammonium) on the synthesis is also studied. In the case of the templated approach, in which the alkylammonium ions are pre-adsorbed on the clay prior to the pillaring with APTS, a surface area and a pore volume as high as 487 m2 g~1 and 0.45 cm3 g~1 have been obtained.

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“…Some important factors in the clay pillarings include the size and amount of pillars and their configuration in the interlayer space, which are highly sensitive to the clay characteristics (e.g., the layer charge and its location) and hydrolysis conditions under which the polyoxycations are formed. 108,109 The resulting pillared clays also inherit properties specific to the chemical nature of the pillaring species, in addition to their improved permanent porosity. Karamanis et al studied the application of Al-pillared montmorillonite for the fast uptake of strontium and caesium ions from aqueous solutions.…”

Section: Pillaring Grafting and Intercalation Techniquesmentioning

confidence: 98%