HEAT OF IMMERSION OF SOIL ALLOPHANIC CLAYS WITH ORGANIC LIQUIDS

Abstract

The heat of immersion of allophane and imogolite with a number of organic liquids was measured in order to investigate their interaction. The same measurement was carried out for layer-silicate clay minerals as reference.
The heat-of-immersion values decreased in the order: methyl alcohol>ethyl alcohol>n-propyl to n-decyl alcohols. This order was common to both allophane and layer-silicate clay minerals. The higher values for methyl and ethyl alcohols were ascribed to their greater energy and amount of adsorption. These two alcohols were considered to be adsorbed mainly by the hydrogen bond, whereas the alcohols containing more than three carbon atoms by the van der Waals force. The heatof-immersion values for allophane were higher than those for layer-silicate clay minerals, suggesting that the former has larger number of surface OH groups than have the latter. The difference in the heat-of-immersion values between ethyl alcohol and ethylene glycol was interpreted in terms of the difference in their energy of adsorption due to the difference in their polarity. The differences were also found in the heatof-immersion values for the isomers of butyl alcohol, probably reflecting the effect of the shape of molecules on their adsorption.
There was no noticeable difference between the heat-of-immersion values of allophane for polar and nonpolar aromatic liquids. From this were inferred the similarity in the amount and energy of adsorption of both the groups of aromatic compounds, and the van der Waals interaction between them and allophane. The heat-of-immersion values for montmorillonite were notably higher with a polar aromatic liquid than with a nonpolar one. The heat-of-immersion values for nonpolar liquids decreased from benzene to n-hexane through carbon tetrachloride. The heat-of-immersion values in nonpolar liquids were remarkably higher for allophane and imogolite than for montmorillonite. This difference was correlated with the difference in their surface area, determined by N₂ gas adsorption.