Calcium self-exchange

The work presented here addresses this question for a laboratory ion-exchange system that is relatively simple. Effluent concentration histories were obtained for calcium and chloride ions during miscible displacement of calcium chloride solutions through vertical columns containing homogeneous, repacked sandy soil that was water-saturated. Calcium self-exchange was the... 

One-dimensional transport through soils of calcium affected by equilibrium-controlled self-exchange is described by ... 

The self-bound LSX is readily converted to other ion forms using standard ion exchange techniques. The calcium form was prepared in most cases directly from the mixed Na/K adsorbents. Four 2-hr. exchanges, with at least a fourfold excess of 1 H CaCl2 at temperatures between 90 and 100°C, generally produced samples having >98% of their exchange capacity in the calcium form. 

Figure 1 shows the overall scheme for the preparation of a self-bound LSX adsorbent, from metakaolin pellets which after calcium exchange have Improved performance as adsorbents for air separation. We have made self-bound LSX by contacting the porous metakaolin pellet with a mixture of sodium and potassium hydroxides at relatively low temperatures and pressures. 

Bulk elemental analysis confirmed that the calcium form of self-bound LSX pellets has a Si/Al ratio of 0.99 and a calcium exchange capacity of 7.03 mequiv./g on a dry basis. The calcium... 

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