Interactions of ammonium smectite with low molecular weight carboxylic acids.

Abstract : This study aims at better understanding the interaction between an ammonium smectite and carboxylic acids. The SWy-2 (Wyoming smectites) has been exchanged with NH4 + and then batched with carboxylic acids (acetic, formic, chloroacetic and oxalic) in concentrations between 0,01M and 1M. The obtained solid phases have been chemically analyzed and characterized by infrared absorption spectroscopy and X-ray powder diffraction. The ionic chromatography has been used for the quantitative measurement of ammonium in the solution after interaction. For the four acids, the interaction is characterized by a cationic exchange of NH4+ to H3O+. A partial exchange to Al3+ due to a partial dissolution of the sample in strong acidic medium is observed with chloroacetic and oxalic acids. For these two last acids, the adsorption of molecules on the clay sample occurs, mainly through H-bonding with the cation. Moreover, the intercalation of oxalic acid in the interlayer space has been highlighted.