CHARACTERIZATION OF COPPER(II)-SUBSTITUTED SYNTHETIC FLUOROHECTORITE CLAY AND INTERACTION WITH ADSORBATES BY ELECTRON-SPIN-RESONANCE, ELECTRON-SPIN ECHO MODULATION, AND INFRARED SPECTROSCOPIES

Fluorohectorite containing lattice Cu(II) is synthesized and characterized by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies. Three Cu(II) species are identified in the ESR spectrum of this Cu(II)-substituted fluorohectorite. Species A and B have hyperfine splitting constants of 118 x 10(-4) and 50 x 10(-4) cm-1, respectively, while species C gives spectra that are not well resolved from the g perpendicular-to region of species A and B. On the basis of ESEM measurements, species B is assigned to Cu(II) in octahedral sites with Li(I) in a neighboring octahedral site and species A is assigned to Cu(II) in octahedral sites with no Li(I) in a neighboring octahedral site. Species C is assigned to coordinatively unsaturated Cu(II) sites that are part of the octahedral sheet but that are at the termination of the crystallites, i.e., edge lattice sites. At activation temperatures of 400-degrees-C, species C sites interact strongly with Lewis bases such as pyridine and ammonia. Infrared measurements show that species C sites have moderate Lewis acid strength and also apparently coordinate water molecules but not benzene.