Characterization and technical properties of a Mg-rich bentonite

Abstract

Mg-rich bentonites occur in the Tertiary basin of the Tajo (central Spain), as a result of a chemical sedimentation process. Mg-smectite of saponite type is the principal component of these bentonites, which also contain minor illite, sepiolite, quartz, feldspars, calcite and goethite. The average smectite content is 65%, but it may be as high as 85% in certain bentonitic beds. Na-activated bentonite was prepared to test the main rheological and foundry molding sand properties. Among the most interesting technical characteristics should be noted the high liquid limit (685) and the plasticity index (615), the swelling capacity (40 cm 3/2g) and the yield point (76 lb/100 sq. ft.) for a 6% suspension in water, and the permeability (140) and green strengths enable it to be regarded at least as suitable as the usual montmorillonitic bentonites to be used in foundry sands, pelletizing, ceramics, drilling muds, paints, fertilizers, adhesives, thickening agent for organic media, pesticides, pharmaceuticals, and so on.