The influence of cations of particle interactions and particle release from aqueous bentonite gels

• Published in: Powder technology 1980-01, Vol.26 (1), p.17-27
• Main Authors: Le Bell, Jean C., Stenius, Per
• Format: Article
• Language: English
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/0032-5910(80)85003-0

The aim of this study is to relate the influence of ground water to the properties of bentonite gels. It has been proposed that compacted bentonite could be used as a buffer substance around canisters containing nuclear waste deposited about 500 m down in the bedrock. The bentonite shield is thought to provide a zone of low permeability which on contact with ground water will swell into cracks formed in the rock. Visual inspection and measurements of the amount of particles released from a bentonite gel by light-scattering showed that while particles are released in distilled water, they are coagulated when in contact with ground water with composition varying within reasonable limits, with the result that the release of particles is negligibly small. Studies of sedimentation volumes after ultracentrifugation also clearly indicated that the bentonite in contact with ground water in the repository forms a completely coagulated gel. It was shown that calcium ions diffuse rapidly into the gel that is in contact with ground water. This implies that bentonite gel which is initially partially in its sodium form will be completely exchanged to its calcium form when brought into contact with ground water. This ensures that it remains coagulated and does not release any particles.