温度对等摩尔CTAB-SDS复配体系表面张力及乳化性能的影响

测定了十六烷基三甲基溴化铵(CTAB),十二烷基硫酸钠(SDS)及它们等摩尔复配体系在不同温度下的表面张力及乳化性能。复配体系的γCMC从10℃的63.67 mN/m下降到90℃的36.38 mN/m,比相应单一体系的γCMC还略低,表现出高温下较高的表面活性。相应的单一体系的CMC值变化不明显,而CTAB-SDS体系的CMC却减少近一半。这些表面活性剂形成的乳液稳定性随温度升高而下降,与表面活性无关。90℃时复配体系的乳液分出10 mL水层的时间只需0.37 m in,使中和电荷加高温有可能成为一种较好的破乳方法,高温时等摩尔CTAB-SDS的高表面活性与所形成乳液的不稳定性使其有可能较好地应用于催化一些两相反应。

Surface Tension and Emulsifiability of Aqueous Equimolar CTAB-SDS Mixture at Different Temperatures

The surface tension and emulsifiability of cetyltrimethylammonium bromide(CTAB),sodium dodecyl sulfate(SDS) and their equimolar mixture were determined at different temperatures.The γ_(CMC) of this mixture decreased from 63.67 mN/m at 10 ℃ to 36.38 mN/m at 90 ℃,a little lower than that of either CTAB or SDS at 90 ℃.Correspondingly,the CMC of CTAB and SDS decreased slightly,while the CMC of their equimolar mixture decreased almost a half.The surface activitiy of this mixture is slightly higher than that of those two individual surfactants at 90 ℃.The emulsion stability of CTAB,SDS and their equimolar mixture decreased as the temperature increased and is irrelevant to surface activity.The very short separating time(0.37 min) of 10 mL water for equimolar CTAB-SDS mixture offers a good way for demulsification by neutralizing the charge of ionic surfactant at high temperature.The high surface activity and unstability of equimolar CTAB-SDS mixture at high temperature offer a good application in catalysis of some reactions in two phases.