Fixing of heavy metals in montmorillonite and the effects on physical properties

摘要

The present work reports the (irreversible) fixing of heavy metals in the crystal structure of montmorillonite and its effects on the clay characteristics and rheological behavior. Heavy metal exchanged montmorillonites were steam-treated under various temperature, pressure and time conditions (up to 300℃ and 6 months). Such studies are relevant to time-lapsing models in barriers at surface conditions and in waste deposits and to hydrothermal conditions in geologic barriers. Investigations with X-ray diffraction and electron microscopy indicate the formation and transformation of phases. Results of spectroscopic measurements (EPR) show the structural position of incorporated ions. Measurements of the rheological behavior characterize changes in mechanical properties. Reasons for changes in the macroscopic chemical and physical properties (rheological behavior, swellability) in relationship to the structural changes of the clay minerals during alteration were discussed.