Exchangeability of Potassium in Heated Fine-Grained Micaceous Minerals

S. J. Smith* and A. D. Scott
Agronomy Department, Iowa State University, Ames, Iowa, 50010, U.S.A.
* Present Address: Water Quality Management Laboratory, Agricultural Research Service, Durant, Oklahoma 74701, U.S.A.

Abstract: Samples of several naturally fine-grained micaceous minerals were heated at 450°C for 24 hr (after the effects of other temperatures and heating periods were evaluated with the < 2 µm fraction of Grundite) and then characterized in terms of their release of K to NaCl-NaTPB (sodium tetraphenylboron) solutions and other potentially related properties.

This heat treatment produced a substantial increase in the amount of K that each mineral released when first placed in the NaCl-NaTPB solution (the greatest increase being 22 m-equiv K/100 g in Marblehead illite). Depending upon the mineral heated, the subsequent rate of K release was increased, decreased or unchanged. Also, all the minerals except glauconite exhibited an increase (ranging from 4 to 38 m-equiv K/100 g) in their maximum degree of K release if they were heated. Thus, it was established that the K release behavior of these minerals is not only subject to appreciable alteration by heat treatments but is altered in a manner that varies with the mineral. The nature of these alterations, however, did not clearly identify an involvement of the other mineral properties that were examined. An increase in NH4- and Cs-exchangeable K occurred when these minerals were heated—presumably as a result of exfoliation. With Morris illite samples, this increase was nearly 28 m-equiv 100 g. Thus, heated samples of these minerals may be useful sinks for the removal of NH4 and Cs in various wastes.

Clays and Clay Minerals; June 1974 v. 22; no. 3; p. 263-270; DOI: 10.1346/CCMN.1974.0220308
© 1974, The Clay Minerals Society
Clay Minerals Society (www.clays.org)