As part of its program in mineral waste management, the Bureau of Mines has investigated the effect of ion exchange on the dewatering potential of clay minerals. Clays of the smectite group possess exchangeable cations to compensate for the overall net negative charge of the clay lattice. The ratio of the valence of the exchange cation to its ionic radius, referred to as the ionic potential, is indicative of the electrostatic influence that a given cation can exert on adjacent molecules. Differential scanning calorimetry and thermogravimetric analyses were performed on eight ion-exchanged montmorillonites (li+, na+, k+, nh4+, ca2+, ba2+, mg2+, and sr2+). Results of these analyses indicate that the energy required to dehydrate the ion-exchanged montmorillonites and the associated dehydration water loss are directly related to the ionic potential of the exchange cation. Furthermore, the ordering influence of the exchange ion is responsible for different hydration states within the interlayer water.
Part. Sci. and Technol., V. 4, No. 4, Oct. 1986, PP. 131-142