Chibowski Emil, Wiacek Agnieszka, Holysz Lucyna, Terpilowski Konrad
Department of Physical Chemistry-Interfacial Phenomena, Faculty of Chemistry, Maria Curie-Sklodowska University, 20031 Lublin, Poland.
Langmuir. 2005 Aug 16;21(17):7662-71. doi: 10.1021/la0505871.
Electrical phenomena at nonionogenic hydrophobic surfaces (solid or liquid) in water, electrolyte, and/or surfactant solutions still attract research. In part 1 of this paper we described the electrokinetic behavior of paraffin wax suspension in water and electrolyte solutions (NaCl or LaCl3). On the basis of the latest data of water structure near hydrophobic surfaces it was concluded that immobilized water dipoles at the interface can play an essential role in the zeta potential formation. In this paper were investigated the zeta potentials of paraffin wax in cationic surfactants cetyltrimethylammonium bromide, C16H33(CH3)3NBr, and octadecyltrimethylammonium chloride, C18H37(CH3)3NCl, and anionic surfactant sodium dodecyl sulfate, C12H25SO4Na. Also changes in wettability of the paraffin surface due to the surfactant's adsorption were studied via wetting contact angle measurements and calculation of the surface free energy. It was concluded that at a low surfactant concentration (10(-6) M) the water dipole structure still contributes to the zeta potential, but at a higher one the zeta potential is determined by the surfactant molecules' adsorption. A special role of OH- ions is also clearly seen. Moreover, a functional relationship was found between the surface free energy of the surfactant-covered paraffin surface and the zeta potential.
水、电解质和/或表面活性剂溶液中，非离子型疏水表面（固体或液体）的电现象仍然吸引着研究。在本文的第1部分，我们描述了石蜡蜡悬浮液在水和电解质溶液（NaCl或LaCl3）中的电动行为。基于疏水表面附近水结构的最新数据，得出结论：界面处固定的水偶极在ζ电位形成中可发挥重要作用。本文研究了石蜡在阳离子表面活性剂十六烷基三甲基溴化铵（C16H33(CH3)3NBr）、十八烷基三甲基氯化铵（C18H37(CH3)3NCl）以及阴离子表面活性剂十二烷基基烷基硫酸钠（C12H25SO4Na）中的ζ电位。还通过测量润湿接触角和计算表面自由能，研究了由于表面活性剂吸附导致的石蜡表面润湿性变化。得出的结论是，在低表面活性剂浓度（10(-6) M）下，水偶极结构仍对ζ电位有贡献，但在较高浓度下，ζ电位由表面活性剂分子的吸附决定。OH-离子的特殊作用也清晰可见。此外，还发现了表面活性剂覆盖的石蜡表面的表面自由能与ζ电位之间的函数关系。
