ION-EXCHANGE PROPERTIES OF RETORTED RUNDLE OIL-SHALE

The inorganic exchange properties of Rundle oil shale, which has been retorted and partially combusted via the Lurgi-Ruhrgas process, were determined so that exchange effects might be incorporated into a model for predicting the generation of leachate. Experiments to measure the pH dependence of such properties showed that a significant cation exchange capacity exists in the buffered pH range of leachate (7. 0-8. 5). Other experiments were performed to measure selectivity coefficients which describe the competitive exchange of the major cations (Ca, Mg, Na and K) in leachate. Selectivity coefficients showed some variation with solution composition. However, the use of average values is proposed for incorporation into an overall model describing the formation and transport of leachate. Cation exchange reactions are shown to be a major controlling mechanism in the leaching of cations from spent oil shale.