CEC of the Boom Clay - a review

The cation exchange capacity (CEC) is an important physico-chemical parameter of clays studied as potential host rocks and engineered barriers for radioactive waste confinement. The CEC controls the adsorption of cations on clays thus affecting the fate of a number of radionuclides in the clay environment. This study tries to review all the historical data on the CEC parameter of Boom Clay and provides new CEC data as determined by the most advanced currently available techniques for CEC measurements. The new CEC measurements are based on Boom Clay samples collected in the Mol-Dessel reference site, the Essen-1 borehole and various outcrop areas along the Rupel river. The CEC was found to vary in the range of 13 ± 3.33 to 27 ± 1.99 meq/100g at the Mol site, 7 ± 3.2 to 27 ± 2.0 meq/100g at the Essen site and 10 ± 0.64 to 30 ± 0.46 meq/100g in the outcrop Boom Clay samples. In general, the maximum CEC values coincide with the silty clay layers of the Putte Member while the CEC’s are lower in the siltier parts of Boom Clay adjacent to overlying and underlying aquifers.