Hydroxy interlayers in smectites

Sorption of molecular amines by montmorillonite involves protonation of the amine group and hydrolysis of the interlayer cation. Sorption and subsequent desorption of amines may render some of the interlayer cations non-exchangeable, thus causing partial 'chloritization' of the montmorillonite. The effect is stronger with interlayer A1 than Ca ions and depends upon the amine sorbed. I N T R O D U C T I O N Smectites partially interlayered by hydroxy-cation associations, particularly those of A1, have frequently been found in nature. According to Rich (1968) who reviewed the literature, the optimum conditions for interlayer development are not clear, but probably moderately active weathering is required to provide the A1 ions, the pH should be acid and there should be frequent wetting and drying of the clay. In addition he postulates that organic matter should be scarce. Recent studies (Heller-Kallai, Yariv & Riemer, 1972; Yariv & Heller, 1970; Bodenheimer, Heller & Yariv, 1966) suggested that sorption of organic materials by clays rather than impeding 'chloritization' may, under specific conditions even cause it. ('Chloritization' is here used in its broadest sense to include any hydroxy interlayering.) The present study was designed to investigate the possibility of hydroxy interlayering in smectites under the influence of amines. E X P E R I M E N T A L Approximately monoionic samples of A1and Ca-montmorillonite were obtained by repeated saturation of a sample of Wyoming montmorillonite with 0.1 N solution of the appropriate nitrate. They were washed and stored in the form of 1-2% aqueous suspensions. 36 L. Heller-Kallai, S. Yariv and M. Riemer Aliquots of these suspensions, containing 50 mg portions of clay, were placed in glass tubes and the volume made up to 6 ml with distilled water. The suspension was mixed with a magnetic stirrer for 10 min, 3 ml of a 0.025 M solution of the base were then added and the suspension was stirred for a further 1 hr. The supernatant solution was analysed and duplicated samples of the residue, washed with distilled water, were subjected either to carbon analyses or to cation exchange with 1N LiC1 solution. The amounts of exchangeable cations of the original monoionic clay samples were determined by the same method. The concentration of the various cations in solution was estimated by atomic absorption spectrophotometry and the carbon content of the clay samples with a Leco carbon analyser. IR spectra of self-supporting discs and X-ray patterns of oriented aggregates under ambient conditions were recorded as previously described (Heller-Kallai, Yariv & Riemer, 1972).