Location and migration of cations in Cu2+-adsorbed montmorillonite

Locations of Cu2+ ion in Cu2+ -adsorbed montmorillonite have been studied b y electron paramagnetic resonance (EPR), supplemented by X-ray diffraction (XRD) and differential thermal analysis (DTA). In the EPR spectra of Cu2+ - adsorbed montmorillonite, three signals, corresponding to Cu2+ ion, have be en simultaneously recorded. Some Cu2+ ions seemed to replace the original i nterlayer metal cations and some entered into the hexagonal cavities. A sma ll fraction of Cu2+ ions penetrated into the octahedral vacancies. There we re two ways for the adsorption of Cu2+ ion by montmorillonite - exchangeabl e and specific. On heating, the hydrated Cu2+ ion in the interlayer loses t he coordinating water and then enters into the hexagonal cavities. When the heating temperature further increased, dehydroxylation occurs, which facil itates Cu2+ ion in the hexagonal cavities to penetrate into the octahedral vacancies. (C) 2001 Elsevier Science Ltd. All rights reserved.