DMCA
KINET ICS OF DECOMPOSIT ION OF COBALT COORDINAT ION COMPLEXES ON MONTMORILLONITE SURFACES by
BibTeX
@MISC{Fripiat_kinetics,
author = {J J. Fripiat and J. Hels},
title = {KINET ICS OF DECOMPOSIT ION OF COBALT COORDINAT ION COMPLEXES ON MONTMORILLONITE SURFACES by},
year = {}
}
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Abstract
MO~TTMOm~LLONrrE may adsorb cobalt(III)hexammine a d cobalt(III)chloropentammine cations, and the C.E.C. determined for these complex cations is of the order of magnitude of that obtained with ammonium. The infrared spectra of these coordination complexes adsorbed by the clay are similar to those observed for the corresponding chloride salts. However, when montmoriUonite treated with these coordination complexes is de-hydrated in vacuum or under moderate t~mperature conditions (~100 ~ in a dry atmosphere, the infrared spectra re deeply modified. The complex cations decompose with NH 3 evolution and ammonium formation. Cobalt(II)hydroxide is produced and ammonium cations balance the lattice electrical charge. The true decomposition rate was followed by IR absorbance of NH ~ which showed that the complex decomposition followed that for the homothetic decomposition f solid particles. The apparent activa-tion energy of the decomposition was 20.5 and 43 kcal/molo for the {CoCI(NH3)~) 2+. and {Co(NHs)e)8+-montmoriUonite complexes respectively. An analysis of the combined chemical and IR data on the hexammine complex permitted calculation of the NH 3 diffusion rate between collapsed montmorillonitc sheets. When the interplanar gap approaches IX the diffusion coefficient is approximately 7 • 10-l ~ cm~/see. In contra-diction to their stability in solutions, the cobalt(III)hexammine cation is less stable than the cobalt(III)chloropentammino cati n when absorbed on montmorillonite.
Keyphrases
complex cation coordination complex ammonium cation chloropentammino cati mo ttmom llonrre montmoriuonite complex ir data dry atmosphere diffusion coefficient chloropentammine cation kcal molo interplanar gap approach montmorillonitc sheet apparent activa-tion energy hexammine cation hexammine complex lattice electrical charge ammonium formation combined chemical infrared spectrum re complex decomposition homothetic decomposition solid particle 10-l cm see diffusion rate ir absorbance moderate mperature condition corresponding chloride salt infrared spectrum true decomposition rate
