Forces Involved in Ion Fixation by Vermiculite

The temperature at which vermiculite loses or gains an interlayer of water molecules was compared for a number of interlayer ion saturations. Results indicate the difference between contracting and expanding forces in vermiculite to be dependent upon interlayer ion charge, distance, and hydration energy. Important interlayer forces therefore must be electrostatic attraction between the negatively charged layers and the positive interlayer ions, and expansion due to ion hydration. Basically, ion fixation appears to occur when electrostatic forces of attraction exceed those of hydration