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The Adsorption of Carbohydrates and Related Compounds on Clay Minerals¹

ABSTRACT

Studies were made with the adsorption of carbohydrates on clay minerals. The carbohydrates utilized were ethyl cellulose, methylcellulose 15 cps, cellulose dextrin, starch dextrin, inulin, glycogen, corn polysaccharide, hydroxyethylcellulose, carboxy-methylcellulose, corn starch, and sucrose.

These carbohydrates were adsorbed on both a calcium and hydrogen saturated montmorillonitic type clay. A calcium saturated kaolinitic type clay was also used.

Increasing increments of carbohydrates, ranging from 26 mg. to as much as 450 mg. in certain cases, were added to 1-g. samples of the clays. Twenty ml. of water was added, and the materials were thoroughly mixed by mechanical shaking for 48 hours. The clays were allowed to stand 96 hours to attain equilibrium and were centrifuged. The clear supernatant liquid was then tested for carbohydrate by the anthrone reaction. The difference between the amount of carbohydrate added and the amount in the supernatant liquid was taken as the amount adsorbed on the clay.

Adsorption on the calcium saturated kaolinitic clay ranged from 0.0% to 3.7%. The greatest amount of adsorption on bentonite, the montmorillonitic type clay, was with ethyl cellulose, starch, and cellulose dextrin, 20.5%, 21.6%, and 12.4% respectively. Little difference was noticed between the calcium and hydrogen saturated clays.

X-ray diffraction analyses demonstrated that the carbohydrate materials were adsorbed between the interplanar spacings of the montmorillonitic clay. Infrared spectra analysis suggests that hydrogen bonding plays a role in the adsorptive mechanism. Extractions with bases, acids, and salts suggest that cation and anion exchange are not involved in the adsorption of these carbohydrates.

¹ Published as Miscellaneous Paper No. 209 with the approval of the Director of the Delaware Agr. Exp. Sta. Contribution of the Department of Agronomy. Funds for this research were provided by Andelot Inc. through the Haskell Research Foundation.

² Assistant Professor, Graduate Assistant, and Associate Professor of Agronomy, University of Delaware, respectively.

Received for publication October 25, 1954.