The Effect of Cation Exchange of Tris(Ethylenediamine)Cobalt (III) for Sodium on Nitrogen Sorption by Montmorillonite

Abstract

Abstract--The cation exchange process between tris(ethylenediamine)cobalt(llI) and Na + on montmoriUonite was studied by atomic absorption spectrophotometry, X-ray diffraction, differential thermal analysis, and nitrogen sorption at 78~ The exchange of Co(en)33+ for Na § was found to be extremely favorable, with a tendency toward segregation of the two kinds of cations in the mixed clays studied. Small amounts of Co(en)a § were found to lower the nitrogen sorption capacity of Na § montmorillonite while clays with high Co(en)3 +a content had greatly enhanced sorption. An explanation is offered in terms of a dual role of the Co(en)3 +~ in determining the kind and amount of nitrogen sorption in the exchanged montmorillonite. INTRODUCTION THE~E have been many studies of nitrogen sorption by homoionic montmorillonite clay minerals. Some recent examples are Aylmore (1970); Barter (1967);Slabaugh (1971) and Thomas (1968). However, relatively little has been reported on nitrogen sorption by clays containing varying ratios of two different kinds of exchangeable cations. Barrer et al. (1963) showed that a study of the change in nitrogen sorption as a function of degree of exchange between two kinds of cations on a montmorillonite can give some information on the exchange process. This technique is most useful when the two cations involved give homoionic clays of. greatly different sorption characteristics. Barrer's study did not cover a wide range of cation ratios and his data implied a linear change in nitrogen sorption with change in mixed cation ratios.In the present study it was found that by preparing a Co(en)3 +3 montmorillonite from a Na + montmorillonite, the nitrogen sorption capacity of the clay was increased by over 500 percent. Also, the sorption isotherm in the partial pressure range studied (P/Po = 0.05-0.25) changed from B.E.T. for the Na § clay to Langmuir for the Co(en)z +3 clay. Since the sorption capacities and isotherm characteristics of these two clays were so different, nitrogen sorption was used to study various mixed

Interlamellar and Multilayer Nitrogen Sorption by Homoionic Montmorillonites

“…For their respective situations they concluded that the observed variation in nitrogen sorption capacities was due to a variation in the degree of interlamellar nitrogen penetration. Knudson and McAtee (1973) have also observed that interlamellar nitrogen penetration readily occurs for a tris(ethylenediamine) cobalt (III) montmorillonite. The purpose of this work was to study nitrogen sorption by various homoionic montmorillonites in an attempt to find a simple way of distinguishing interlamellar from external nitrogen sorption.…”

“…The details of the procedure used have been described previously (Knudson and McAtee, 1973). Samples of the Na § Cs § and (CH3)~NH~ clays were sent to Baroid Division, NL Industries for nitrogen adsorption isotherms for comparison with the Sorptometer results.…”

“…It has been shown by Knudson and McAtee (1973) that the nitrogen sorption isotherm for tris(ethylenediamine) cobalt(Ill), Co(en)3L montmorillonite was Type I in the classification of Brunauer, Emmett, and Teller (see, for example Gregg and Sing, 1967), while Na § montmorillonite was Type II. The difference in isotherm types was attributed to predominance of interlamellar sorption for the Co(en) ] + clay and to predominance of external or multilayer sorption for the Na+-clay.…”

Surface Properties of Smectites Exchanged with Mono- and Biprotonated 1,4-Diazobicyclo(2,2,2)-Octane

“…For Na-Dabcol+-OT (and eventually Na-Dabco~+-MO) a slight decrease in So was observed from the Na-clay to a minimum value, which corresponded to the "threshold" Dabco 1 § contents which initiated interlamellar swelling, as seen from d(001) values (Figure 2). These observations can be explained by the decrease in the external part of the So due to the surface occupied by organic cations (McBride and Mortland, 1975) or cationic complexes (Knudson and McAtee, 1973). Alternatively, the increased c-dimensions of Dabco 1+ clays may be invoked to explain the decreasing external surface area.…”

“…Permanent intracrystalline porosity can be obtained in layer silicates by exchange with organic cations such as (CH3)4N +, (C2Hs)4N + (Barrer and McLeod, 1955;Barrer and Brummer, 1963;McBride and Mortland, 1975) or l-4-diazobicyclo(2,2,2)-octane (Dabco) (Mortland and Berkheiser, 1976;Shabtai et al, 1977), or cationic complexes such as trisethylenediaminecobalt(III) (Barrer and Jones, 1971;Knudson and McAtee, 1973). The available interlamellar space can be modulated (1) by varying the size and the charge of the "pillars" that control the lateral cation-cation distance as well as the free interlayer distance; (2) by varying the charge density of the clay mineral; and (3) by partial exchange of the inorganic cations.…”