STUDY OF THE ADSORPTIVE PROPERTIES OF A P ILLARED CLAY TOWARDS CU2+ AND CD2+ AS A FUNCTION OF PH

On the basis of both macroscopic and microscopic data (adsorption isot herms at variable pi-Is, NMR spectroscopy for Cd2+ and EPR for Cu2+), we propose a chemical model of the interface reactions between metal c ations and a clay pillared by hydroxyaluminic polycations. The pillars may be considered as an ultradispersed aluminic phase situated betwee n the layers and are responsible for its adsorptive properties, which are similar, but not identical, to those of an alumina surface. The ex istence of ionisable acid sites on the pillars favors the adsorption o f M(2+) cations at pH values inferior to those reported for Al oxides and hydroxides.