全氟烷基表面活性剂吸附特性研究

Investigation on adsorption characteristics of perfluoroalkyl surfactants

针对全氟烷基季铵碘化物(Le-134)、全氟烷基磷酸酯(Le-107)和全氟烷基聚醚(Le-180)三种表面活性剂水溶液的平衡态表面张力和吸附动力特性进行了研究。临界胶束浓度的大小关系为Le-180(15×10^-6)<Le-134(40×10^-6)<Le-107(150×10^-6);饱和吸附量Гmax大小关系为Le-107<Le-134<Le-180。三种表面活性剂降低静态表面张力的效能接近,可将表面张力降低至20 mN/m以下。从亲疏水基、反离子的作用等方面对静态表面张力特性进行了分析。动态表面张力方面,Le-134降低表面张力的速度较快,Le-180次之,Le-107最慢。三种表面活性剂水溶液在低浓度时均属于扩散控制吸附;在高浓度时,吸附过程变化为混合动力控制吸附。研究了不同浓度下三种表面活性剂水溶液的表观扩散系数和吸附势垒的变化。结果表明吸附动力特性的变化主要原因可能是因为分子结构不同和胶束等对吸附过程产生了影响。

Equilibrium surface tension and adsorption dynamic characteristics of perfluoroalkyl quaternary ammonium iodide(Le-134),perfluoroalkyl phosphate(Le-107)and perfluoroalkyl polyether(Le-180)were investigated.The relationship between the critical micelle concentration is Le-180(15×10^-6)<Le-134(40×10^-6)<Le-107(150×10^-6);the saturation adsorption amountΓmax is Le-107<Le-134<Le-180.The effect of three kinds surfactants on reducing surface tension is similar,and the surface tension of surfactant aqueous solution can be reduced below 20 mN/m.Equilibrium surfaces tension characteristics were analyzed from the hydrophilic and hydrophobic groups and counterions.The dynamic surface tension(DST)of Le-134 drops fastest while Le-180 in second and Le-107 is the slowest.When the concentration of surfactant is relatively small,the adsorption is controlled by diffusion.Whereas the adsorption mechanism changes from diffusion controlled to barrier controlled at high concentrations.The variation of apparent diffusion coefficients(Da)and adsorption barriers(Ea)of three aqueous surfactant solutions at different concentrations were investigated.It can be indicated that the variation of adsorption dynamics is mainly due to the difference in molecular structure and the influence of micelles on adsorption process.