Several textural properties of compacted and cation-exchanged bentonite

Abstract

Abstract One of the principal applications for bentonite is in drilling muds. Moreover it is widely used as a suspending and stabilizing agent, and as an adsorbent or clarifying agent, in many industries. Recently the bentonites have been proposed as engineered barriers for radioactive waste repository because these materials are supposed to build up a better impermeable zone around wastes by swelling. For these reasons, a textural characterization of bentonites in the laboratory is very important. The aim in this study was to estimate several textural properties of compacted and cation-exchanged bentonite by using Hg-porosimetry, N 2 -adsorption, water vapour adsorption, scanning electron microscopy (SEM) observations and environmental scanning electron microscopy-digital images analysis measurements. For that, bulk samples were mechanically compressed at atmospheric conditions by using a uniaxial system at four different pressures (21, 35, 49, and 63 MPa) in order to obtain four physical densities. On the other hand, the bulk samples of bentonite were treated separately with four concentrated solutions (1N concentration) of sodium, potassium, magnesium and calcium chlorides in order to obtain a homoionic interlayer cation in the clay phase. The results showed that the macro-porosity (porous size>50 nm) and eventually the mesoporosity (porous size 2–50 nm) are affected by the uniaxial compaction. In this case, a transformation of the shape of the macro-pores network from tube to crack was observed. On the other hand, the swelling potential and water content are governed by the relative humidity and by the nature of interlayer cation.