A STUDY OF ACIDITY AND STRUCTURE OF HYDROXY-CR INTERCALATED BENTONITES

Hydroxychromium bentonites were prepared using hydroxychromium solutio ns with a OH/Cr content of about 1 and 2. The samples were heated in a ir and vacuum to study the influence of temperature and atmosphere on their final properties, Structural characteristics were obtained using X-ray diffraction and sorption of nitrogen, The surface chemistry was evaluated by means of infrared spectroscopy and potentiometric titrat ion, The results obtained demonstrate the influence of the content of intercalating solutions on the properties of clays, Intercalation caus ed a fourfold increase in the surface area compared to the initial ben tonite, Potentiometric titration and IR provides the evidence of inner -sphere complexation of the interlayer Cr with siloxane oxygen. The pK (a) distributions revealed peaks characteristic of chromium polymers ( Cr-III). Heat treatment of intercalated samples in air caused oxidatio n of Cr species resulting in Cr-VI. (C) 1996 Academic Press, Inc.