Structural, sorption and thermodynamic correlations from a layered barium phenylarsonate/n-alkyldiamine system Original Research Article

The barium phenylarsonate compound, Ba(HO3AsC6H5)2·2H2O, has the ability to intercalate n-alkyldiamine molecules, H2N(CH2)nNH2 (n=2–5). The amount intercalated (nf) from a batchwise procedure and the variation of the original basal distance (d) of 1245 ppm determined through X-ray diffractions, gave linear correlations as a function of the number of carbon atoms in the aliphatic chain (nc): nf=(2.66±0.06)−(0.13±0.02)nc and d=(2168±65)+(114±14)nc. The intercalation process was calorimetrically followed to give exothermic enthalpy and negative Gibbs energy, reflecting spontaneous intercalation reactions at the solid/liquid interface. The displacement of solvent molecules bonded to amine and of those on the matrix during the intercalation increases the disorder to result in positive entropy, giving a favorable set of thermodynamic data for this system.