An Optical‐Transmission Study of the Interaction Between Montmorillonite and Humic Acids

Abstract
The interaction between montmorillonite and kaolinite clay minerals and humic acid (HA) was studied in suspensions by absorbance measurements. Changes in absorbance as a result of the interaction were interpreted as an indication of changes in the size of clay tactoids. Na‐humate caused dissociation of montmorillonite tactoids in suspension. Drying‐wetting cycles increased the effect of Na‐humate and resulted in tactoids similar in their size to those of the Li‐saturated montmorillonite. Na‐humate had no effect on the absorbance of kaolinite suspensions.