Hydrophobic agglomeration of colloidal kaolinite in aqueous suspensions with dodecylamine

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.