CESIUM SORPTION REACTIONS AS INDICATOR OF CLAY MINERAL STRUCTURES

At low cesium ion concentrat ions extremely h igh selectivities for cesium arc exhib i ted by layer lattice sil icates wi th uncxpanded 10A c-spacing. The total amount of ces ium which can be sorbed by these minerals depends on the edge area and the exchange capacity. At a concentrat ion of 10-5 meq of cesium and 5 meq of sodium, a sample of biotite represent ing less than 0.025 meq of exchange capacity sorbed over 90 per cent of the cesium and a hydrobiot i te with 50 percent vermicul i te and representing 1.0 meq of exchange capacity sorbed 80 percent of the cesium. After heat ing bentoni tes to 500-700 ~ C more cesium is sorbed from solutions conta in ing h igh sodium concentrat ions by the heated bentonite than the original material. The change in the amount of cesium sorbed as a result of heat ing may be a useful property for detect ing the presence of montmori l loni te in mixed or inter layered mineral systems. Latt ice expansion of biot ite results in improved cesium sorption; th is behavior is due to generat ion of sufficient favorable exchange sites to offset the loss of edges with favorable 10A spacing