A Comparison of the Exchange Behaviour of Tris-triethylene Diamine Cobalt (III) by Tetraalkylammonium, Alkanediammonium and Surface Active Ions on Laponite and Vermiculite

The release of Co(tn)³⁺₃ from its laponite complexes by organic ions reveals that in general the extent of desorption increases with the size of the latter. At higher level of exchange, (CH₃)N⁺ becomes more effective than (C₂H₅)N⁺, which is perhaps due to the collapse of the silicate layers in suspension when a critical level of exchange is attained. In contrast, the exchangeability of the tetraalkylammonium ions in vermiculite is inversely related to ionic size. The displacement efficiency of the long-chain surfactants and alkanediammonium ions was found to increase as usual with chain length in vermiculite. The selectivity coefficients of the long-chain monovalent ions are higher than the bivalent short-chained ones or tetraalkylammonium ions for both the minerals. The desorption data also show that Co(tn)³⁺₃ is more strongly bound in the virmiculite, which may be related to its higher charge density compared to laponite.