Colloid and Radionuclide Retardation (CRR) Results : Are Colloids Stable ?

As expected from the study of other groundwater systems, it was confirmed that colloid stability is strongly dependent on the pH and Ionic strength ( I ) of the groundwater type (see evolution of hydrodynamic diameters of colloids below).

Therefore, bentonite colloids show high stability under the experimental groundwater conditions in the experimental site (I = 10-3 M and pH = 9.5). In order to verify this, the colloid size distribution was also investigated for longer time periods with colloids obtained from previously washed bentonite and conditioned in the experimental site groundwater. The concentration of the suspension was approximately at 2000 mg/L. The colloid size distribution was found to be rather constant over a period of approximately five months.

Evolution of the hydrodynamic mean diameter of bentonite colloids in a suspension of
different ionic strengths, pH 8.7 +- 0.5

 Colloid and Radionuclide Retardation Experiment (CRR) are colloids stable ?
Evolution of the hydrodynamic mean diameter of natural bentonite colloids and different pH


Colloid and Radionuclide Retardation Experiment - Results

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.