Analysis of interactions between colloidal wood pitch and various mineral particles by flow cytometry

The interactions between colloidal wood pitch and various commercially available mineral particles were assessed. The experiments were conducted by adding PCC, GCC, kaolin, and bentonite particles to laboratory-made pitch emulsions, and the mixtures were analyzed using flow cytometry. The results showed that most of the tested minerals were quite hydrophilic. The hydrophobicity of the mineral particles increased significantly in the presence of colloidal pitch, which showed that interactions between the pitch and the mineral surfaces occurred. The charge of the mineral particles was very important; the pitch–mineral populations formed with cationic minerals were more hydrophobic than those formed with anionic minerals. Water-soluble galactoglucomannans from spruce diminished the adsorption of pitch onto cationic minerals, while they had no significant effect on the adsorption of pitch onto anionic minerals.