Wettability of quartz by aqueous solution of cationic surfactants and short chain alcohols mixtures

Abstract

Advancing contact angle measurements for aqueous solution mixtures of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPyB) with methanol, ethanol and propanol on quartz surface were carried out. From the obtained results it appeared that quartz wettability by these mixtures depends on the kind of alcohol and cationic surfactant and that there is linear dependence between the adhesion and surface tension of aqueous solution of the mixtures of CTAB and CPyB with alcohols at constant CTAB or CPyB concentration. This dependence can be described by linear equations which constants depend on CTAB and CPyB concentration and the kind of alcohol. The slope of all linear dependences between the adhesion and surface tension is positive. The critical surface tension of quartz wetting determined from these dependences by extrapolating the adhesion tension to the value corresponding to the surface tension of solution at which should be observed the contact angle strictly equal zero depends on the kind of alcohol and constant CTAB or CPyB concentration and is lying in the range from 25.9 to 33.3 mN m −1. The minimal value of the critical surface tension of wetting is somewhat lower, and the maximal is higher than the apolar component of the surface tension of quartz covered with monomolecular film of water. The dependence between the adhesion and surface tension at constant alcohol concentration is not linear, and it is difficult to determine the critical surface tension of quartz surface wetting from this dependence. A positive slope of the adhesion tension against the surface tension curves at constant CTAB or CPyB concentration indicates that alcohol molecules probably do not penetrate to the “bare” quartz surface and are adsorbed rather at quartz/monomolecular CTAB or CPyB film–solution interface because CTAB and CPyB molecules interact more strongly with quartz surface than those of water. In the presence of alcohol rather a monolayer of CTAB or CPyB is formed at quartz–water interface. However, in the absence of CTAB or CPyB alcohol molecules are probably adsorbed at quartz/monomolecular water film–solution interface. This conclusion is confirmed by the calculations of the adhesion work of aqueous solution of alcohols to the quartz surface. For the calculations of the adhesion work the surface tension of the quartz covered with a water film and alcohol surface tension components was taken into consideration.