EMF和电导率法对SDS胶束体系热力学性质研究  

Investigation of thermodynamic properties of SDS micellar system by EMF and conductivity methods

作　　者：吕建晓[1] 王栋[1] 周集体[1] 郑攀峰[1] 

机构地区：[1]大连理工大学环境科学与工程系,辽宁大连116024

出　　处：《大连理工大学学报》2006年第5期661-666,共6页Journal of Dalian University of Technology

摘　　要：为深入了解表面活性剂溶液的性质，对其在使用和处理过程中的行为加以控制，在298K恒温下，用Na^＋选择性电极法测量了不同浓度的阴离子表面活性剂十二烷基硫酸钠（SDS）溶液的电动势（EMF），求出了其临界胶束浓度（Cmc）及反离子结合度，进而获得了反离子与胶束结合的经验平衡常数Kass,实验数据表明，随表面活性剂浓度增大，Kass降低，反离子与胶束表面的结合逐渐弱化，在289～328K测量了SDS溶液的电导率随浓度的变化，求出了不同温度下的Cmc值，发现随温度的变化Cmc曲线存在一个最低点．由Cmc与温度T的关系，计算了胶束化热力学参数△micG^0、△micH^0和△micS^0．结果表明，△micG^0在整个实验范围内均为负值，胶束化过程可以自发进行；△micH^0的值相对于T△micS^0小很多，胶束化过程为熵驱动过程．以上特征参数的确定，可为研究表面活性剂溶液的各种应用以及处理技术提供重要参考．To understand the properties of surfactant solutions in detail, and control their behaviors in use and disposal processes, EMF values of a series of various concentrations of anion surfactant SDS solutions are measured by Na^＋ selective electrode at 298 K. According to these values, the critical micelle concentration and counterion association degree are calculated, and in turn the empirical equilibrium constants Kass for association between counterions and micelles are calculated, too. Experimental data suggest that Kass decreases with the increase of surfactant concentration. It is shown that the association between counterions and micelles becomes more and more difficult. Then the conductivity of SDS aqueous solutions versus concentration in the temperature region of 289 ～ 328 K are measured, and cmc of SDS at different temperatures are calculated accordingly. It is found that the cmc-T curve exhibits a local minimum. According to the relationship between cmc and T, the micellization thermodynamic parameters △micG^0, △misH^0and △micS^0 are calculated. △micG^0 values are negative in the whole experimental region, which shows that micellization process can happen spontaneously. Values of △micH^0 are very small compared with those of T△micS^0, so the micellization process is entropy-driven one. The determination of the above parameters can serve as an important reference to the researches on various kinds of use and disposal techniques of surfactants.

关 键 词：SDS EMF 临界胶束浓度 反离子结合度 电导率 胶束化热力学参数 

分 类 号：O647.2[理学—物理化学]