Interlamellar and Multilayer Nitrogen Sorption by Homoionic Montmorillonites

Abstract

Abstrac~Nitrogen sorption by various homoionic montmorillonites was studied at 78~ The adsorption isotherms in the relative pressure range P/Po = 0.05-0.25 were found to be either Type I or Type II in the BET classification. The nitrogen sorption process was considered to be predominantly interlamellar when described by a Type I isotherm. With a Type II isotherm, the adsorption was assumed to be predominantly on those surfaces not in the interlamellar regions.It was concluded that only cations within a certain size range promote significant interlamellar nitrogen penetration in montmorillonites. The role of the smaller cations in nitrogen sorption by montmorillonites seems to be their influence on the external aggregate structures, Very large cations tend to clog up the interlamellar pores as well as some of the external voids.

Microporosity in Montmorillonite from Nitrogen and Carbon Dioxide Sorption

“…Figure 4(a) for Cs + Wyoming bentonite] support the consistent agreement of the sorption process for nitrogen on these homoionic montmorillonites with the multilayer theory, as observed by Knudson and McAtee (1974), rather than with the monolayer equation. In each case, the BET plots provide good straight lines whilst the Langmuir plots show marked negative curvature, indicating that considerably more sorption is occurring than corresponds to monolayer formation.…”

“…Such plots are not particularly sensitive to small variations but should be adequate to judge the predominant process. Knudson and McAtee (1974) reported that for montmorillonite saturated with large dimethylammonium or Co(en) ] + ions, comparative plots of the BET and Langmuir functions indicated that significant interlamellar sorption of nitrogen did occur. In Figure 3, Vn plots for nitrogen sorption on Redhill montmorillonite saturated with hexane diammonium ions and outgassed at temperatures of 50~ 100~ and 250~ respectively, are given.…”

“…evidence supporting the interlamellar penetration of carbon dioxide in homoionic smectites although, once again, using a relatively mild outgassing procedure. Knudson and McAtee (1974) by classifying nitrogen sorption isotherms on homoionic montmorillonite into Type I or Type II plots of the Brunauer classification, concluded that no significant interlamellar sorption occurred in the case of the sodium, barium and caesium clays. Significant interlametlar sorption of nitrogen occurred only for a narrow size range of larger exchangeable cations such as the dimethylammonium and Co(en)~ + ions.…”

The Relationship between Structural Properties of Metal-Tris (Ethylenediamine) Montmorillonite and Their Behavior as Gas Chromatographic Packing Materials

“…is either quite small or partially offset by true interlamellar exchange within the clay platelets even at low exchange values. A more thorough discussion on this area of cation exchange and its surface area effects carried out on a similar cation (Co(en) 3+) has been published recently by Knudson (1974).…”

CO2 Storage in Shallow Underground and Surface Coal Mines: Challenges and Opportunities

“…A corollary of this structure is that clays can expand for better pore accessibility and then contract to trap small molecules into a "sandwich" between the phyllosilicate micelles, or lamellae. Cations of medium size that would not clog the interstices between the strata can play a significant role in promoting the interlamellar sorption in dry clays (9). Also, small amounts of residual water have been shown (8) to have a profound effect on accessibility to the areas between the lamellae, forming pseudocrystals.…”