Hydrophobic agglomeration of colloidal kaolinite in aqueous suspensions with dodecylamine

• Found out that DDA induced a much stronger aggregation in aqueous kaolinite suspensions.
• Presented a good correlation of kaolinite aggregation with DDA adsorption and surface hydrophobicity.
• DDA induced hydrophobic agglomeration of colloidal kaolinite was negatively affected by NaCl addition.

The stability of colloidal kaolinite dispersions in the presence of dodecylamine (DDA) has been studied in this work through the measurements of aggregation degree, zeta potential and adsorption. The experimental results show that DDA can induce a strong aggregation of colloidal kaolinite in aqueous suspensions even though the particles are highly negatively charged. This aggregation closely correlated to the adsorption of DDA cation on kaolinite surfaces and the hydrophobicity, so that it should belong to hydrophobic agglomeration. The adsorption isotherm of DDA on kaolinite surfaces showed two regions in which the adsorption density sharply increased, which might correspond to the hemi-micelle and bilayer adsorption of DDA cation on the surfaces. In addition, the hydrophobic agglomeration could be weakened by the addition of NaCl, which was due to the decrease of DDA adsorption on kaolinite surfaces.

The DDA adsorption isotherm curve on kaolinite in aqueous solutions could be divided as three regions. The adsorption in the region I and III were attributed to the hemi-micelle and bilayer adsorption of DDA cation, respectively. They well corresponded with the curves of aggregation degree and zeta potential of kaolinite particles in aqueous suspensions.Figure optionsDownload as PowerPoint slide