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Under Contract No. 11V-13619V March 1980 NOTICE. This document contains information of a preliminary nature. It is subject to revision or correction and therefore does not represent a final report.

Selectivity for cesium was improved by heating montmorillonites to temperatures in the range offrom 600 to 700°C. The optimum temperature depends on the saturating cation and bentonite type. For montmorillonites heated in this temperature range and a t higher temperatures, clay-solution contact time was an important consideration. Sorption characteristics over a wide range of cesium concentration were investigated; the results suggested a multifunctional exchange reaction for the 600°C calcium-montmorillonite and a simple mass action reaction for the oven-dried calcium-montmorillonite. The study of the influence of heating periods a t 600°C for calcium-montmorillonite showed that longer heating periods resulted in a decreasing degree of initial sorption; however, cesium sorption gradually increased with solution-clay contact time and eventually exceeded the cesium sorption of ovendried samples.These findings are significant for the understanding of clay mineral genesis and for applications in ground disposal of radioactive waste.