Characteristics of clay minerals of montmorillonites in the wet state

The characteristics of five clay minerals of montmorillonites in the wet state were investigated and compared with those in the dry state. The grain size and surface structure were examined with an electron microscope. The clays of Ca and H forms remained as porus particles of several μm in the wet state, but the clays of Na form were dissociated into very fine crystalline particles below several hundred Å. Results of X-ray diffraction studies showed that the basal spacings of all the samples increased from 9.6A in the dry state to about 18.8Å or 19.6Å in the wet state. Pore size distributions and specific surface areas in the dry and wet state were determined by nitrogen and water vapor adsorption techniques and calculated by cylindrical pore and parallel plate models. The micro pore volumes of various montmorillonites increased from 25-160 mm3/g to 240-340 mm3/g, and the specific areas increased from 10-150 m2/g to 300-450 m2/g, in going from the dry to wet state.