Sedimentation in micellar solutions of tetradecyltrimethylammonium bromide

In the paper the results of experimental studies on the sedimentation process of barium carbonate (of mean particles diameter of 25 [μm]) in aqueous solutions of tetradecyltrimethylammonium bromide, have been presented. As the additives assisting in micellar association the sodium bromide and sodium salicylate, have been used. The sedimentation tests were carried out in the transparent cylinder of 1 dm volume and height of 34 [cm]. It has been shown that in tetradecyltrimethylammonium bromide solutions of concentrations of 1⋅CMC and 2⋅CMC, the sedimentation process proceeds faster than in clear water. The reason of that observation can be a fact that the cationic surfactants are adsorbed on the barium carbonate molecule surface. As the result it causes the both, reduced surface charge and decreased repulsion between particles. Aggregation is induced by the hydrophobic interactions between particles. It will facilitate the approach of molecules to each other and the greater agglomerates are formed. For the sake of bigger mass, the molecules fall faster. Growth of the TTAB concentration to 10⋅CMC level and addition of sodium bromide into a solution causes slowing down the sedimentation process. It is the result of the growth in fluid density and viscosity. The sedimentation velocity for barium carbonate falling in TTAB/NaSal system was lower than this one in the clear solvent observed. Density of this solution was comparable with water density, whereas the growth of the viscosity of solution has been observed. It can be the result of the decrease of sedimentation velocity.