Adsorption and oxidation of aniline and p-chloroaniline by montmorillonite

ABSTRACT: The adsorption of aniline (ANL) and p-chloroaniline (PCA) from 0.02 M meth-anol and chloroform solution on air-dried montmorillonite s determined by the conjunction of several factors: (i) basicity of the solute, (ii) complexing ability, Br6nsted and Lewis acidity of the exchangeable cation, (iii) polarity and Lewis basicity of the solvent. The principal adsorption mechanisms, inferred from infrared ata, are direct or indirect coordination and protonation of the adsorbate. They take place simultaneously and to a relative extent depending mainly on the exchange cation. On Fe-, A1- and H(A1)-montmorillonite ANL and PCA give rise to type II complexes, characterised byan intense charge-transfer band in the infrared region and by the formation of radical cations, evidenced by ESR spectroscopy. This oxidation process occurs on heating in air, but with Fe 3+ in vacuo also and even at ambient emperature in methanol solution. On Cu-montmorillonite ANL, contrary to PCA, does not give a type II complex; however, adical species are produced in air and in vacuo and their production isenhanced by heating