The Ordering of Cetylpyridinium Bromide on Vermiculite

Abstract--Adsorption of cetylpyridinium chloride (CPC) onto kaolinite can be followed using the electroacoustic effect. The dynamic mobility, measured at a frequency of l MHz, varies from about -2 to +I x 10 s m E V-i s-J in a number of steps, reflecting the adsorption of two separate layers, with the bilayer being more obvious, especially at pH 5-8. The behaviour at different pHs reflects the different charge characteristics of the basal cleavage planes and the crystal edges. When the amount of added CPC is equal to the cation exchange capacity of the clay, the kinetic charge changes from negative to positive and there is a pronounced break in the conductivity curve. It is also possible to estimate the edge to face area from such measurements and so obtain a measure of the aspect ratio of the clay crystallites. The (minimum) value for this clay is about 5: I.

Section: Introductionsupporting

confidence: 60%

Electroacoustic Study of Adsorption of Cetylpyridinium Chloride on Kaolinite

Rowlands

Hunter

1992

“…Previous workers have chiefly been concerned with the various charged species and radicals formed by benzidine when it is intercalated between clay layers, however, the structures of such intercalates are generally not known. As part of a program concerned with the structures of clay-organic intercalates (Slade et al, 1978;Raupach et al, 1979), we report here the partial structure of a black intercalate formed by vermiculite with benzidine hydrochloride in an aqueous solution at pH 1.6.…”

Section: Introductionmentioning

confidence: 98%

Structural Model for Benzidine-Vermiculite

Slade

1982

Self Cite

A combination of X-ray diffraction, infrared, and chemical data has established that the ion exchange of vermiculite with singly charged benzidine cations in an aqueous solution at pH 1.6 results in a black, highly ordered benzidine-vermiculite intercalate. The intercalate has a basal spacing of 19.25/~ and a primitive unit cell with "a" and "b" edges parallel and equal to those of vermiculite. The number of benzidine molecules per cell is equal to its electric charge. In this structure the benzidine molecules are steeply inclined to the silicate surfaces and close-packed within domains. The domains contain alternating rows of benzidine cations; from row to row the planes are either approximately parallel or perpendicular to the (120) plane, but along any one row the planes of the aromatic rings are parallel to each other. Hydrogen bonding operates between amine nitrogens and surface oxygens.

“…The application of the polarized ATR technique has been shown to be useful for deducing the orientation of intercalated species on phyllosilicates, including cetylpyridinium cations, which have also been used for surface area measurements (Slade et al, 1978), amino acids (Raupach et al, 1975;Raupach and Janik, 1976), and paraquat (Raupach et al, 1979).…”

Section: Introductionmentioning

confidence: 99%

Fourier-Transform Infrared Study of Ethylene Glycol Monoethyl Ether Adsorbed on Montmorillonite: Implications for Surface Area Measurements of Clays

Nguyen

1987

Abstract-Infrared spectra of 2-ethoxyethanol (ethylene glycol monoethyl ether, EGME) adsorbed on Camontmorillonite were obtained using diffuse-reflectance infrared-Fourier-transform (DRIFT) and attenuated total-reflectance (ATR) spectroscopy. The molecular conformation of adsorbed EGME shows predominantly a gauche configuration for the CH2-CH2 linkage as originally present in the liquid. The orientation of the adsorbed EGME molecule in the interlamellar region of the clay was deduced from measurements of the polarized ATR spectra. The planar zig-zag skeleton of the molecule appears to have its long axis tilted at an angle of 44 ~ to the clay surface; the molecule is in van der Waals contact with both adjacent surfaces. Further, the plane of the skeleton of the molecule is tilted at an angle of 69 ~ to the clay surface. This orientation leads to estimates of the d-value of the clay-EGME complex and of the surface area occupied by each molecule. These values are in excellent agreement with independent measurements of both parameters. The full surface coverage on montmorillonite is represented by a single layer of tilted EGME molecules shared by two adjacent clay sheets; each molecule occupies a total surface area consisting of one portion (25.4 A2) on the lower surface of the interlayer plus another portion (14.8 ,~z) on the upper surface. The implication of this model for materials such as kaolinite, where adsorption takes place on the external surface only, is that on these materials each EGME molecule occupies 20/~2 at full surface coverage.