Abstract: In the cationic surfactant hexadecyl trimethylammonium bromide (CTAB) solution, the changes of interactions between the silica surfaces were detected by atomic force microscopy in situ. The results showed that there were significant impacts of concentration of CTAB, electrolytes and incubation time on both the long-range interactions and adhesion forces between silica surfaces, and the wettability of the sand surfaces. In the solution without electrolyte KCl, with the increase of CTAB concentration, the adsorption amount of CTAB on the surface of silicon dioxide increases continuously, and the long-range force between the surfaces of silicon dioxide changes from attractive force to repulsive force. It was further observed that addition of KCl (10mmol/L) in CTAB solutions would enhance the colloidal interactions with the concentration of CTAB and incubation time. At 1.00 mmol/L and 10.00 mmol/L of concentration of CTAB, the long-range force became repulsive. The effect of electrolyte and stabilization time on the colloidal forces between SiO2 surfaces can reflect the changes of adsorption morphology of CTAB on SiO2 surfaces, thus reflecting the electrical properties and wettability of SiO2 surfaces.

Key words: AFM, CTAB, wettability, interaction