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Kinetic studies on adsorption and desorption of surfactants

表面活性剂吸附与解吸动力学研究

基本信息

批准号：
61470155
负责人：
TAGAWA Mieko
金额：
$ 4.1万
依托单位：
Nara Women's University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1988
项目状态：
已结题

项目摘要

The desorption kinetics of surfactant ions at solid/liquid interfaces was investigated by applying the stopped-flow method. A mixing cell of stopped-flow spectrophotometer was modified with platinum electrodes for electric conductivity detection. The change in electric conductivity with time in the desorption process was monitored by a memory-recorder system. Surfactants used were sodium alkyl sultates (C_<10>-C_<16>). The desorption rate of surfactat ions from nylon particles was independent of the surfactant concentration and the rate constants were obtained by applying the first-order reaction scheme, at the concentrations below cmc.Equilibrium adsorption isotherms of the surfactants on nylon particles were obtained from electrokinetic potentials of the particles dispersed in aqueous surfactant solutions at different temperatures. The equilibrium constants of adsorption, K, and the saturated adsorption amount, Ts, were determined from langmuir plots. The values of K and Ts obtained … More by the electro-kinetic method were compared with those by the electiric conductivity method. The values of K by the both agreed with each other. The difference in values of Ts provided information on the slipping plane and the dissociation degree of adsorbed surfactants.Adsorption rate constants were estimated from the desorption rate and equilibrium constants assuming the second-order kinetics. The desorption rate constants were determined in the range of 1 - 6 sec^<-1> and the adsorption rate constants to be in 2 - 8 x 10^4 mol^<-1>dm^3sec^<-1>, the former decreased and the latter increased with increasing number of carbon atoms in akkyl chain of the surfactants.The temperature dependence of desorption rate in the early stage of the process was investigated by an electric conductivity stopped-flow system newly developed. Activation energy of desorption was calculated to be 65.5 kJ/mol form Arrhenius plot, which was almost equal to the enthalpy of adsorption estimated in the same system. Less

采用停流法研究了表面活性离子在固/液界面上的解吸动力学。用铂电极改装了停流分光光度计的混合室，用于电导检测。用记忆-记录系统监测了解吸过程中电导率随时间的变化。使用的表面活性剂是烷基硫酸钠(C_&lt；10&gt；-C_&lt；16&gt；)。尼龙颗粒对表面活性剂离子的解吸速率与表面活性剂浓度无关，在浓度低于cmm时，用一级反应模型求出速率常数，并由不同温度下分散在表面活性剂水溶液中的粒子的动电动势得到尼龙颗粒在尼龙颗粒上的平衡吸附等温线。由Langmuir图确定了吸附平衡常数K和饱和吸附量Ts。得到…的K值和Ts值电动法和电导法的结果进行了比较。两者的K值基本一致。Ts值的差异提供了有关滑动面和吸附表面活性剂解离程度的信息。根据解吸速率和平衡常数估算了吸附速率常数，并假定为二级动力学。在1-6s；-1&gt；和2-8×10^4mol^-1&gt；dm^3秒-1&gt；范围内测定了脱附速率常数，前者随表面活性剂烷基链碳原子数的增加而减小，后者随碳原子数的增加而增大。由Arrhenius图计算出的脱附活化能为65.5kJ/mol，与同一体系的吸附热值基本一致。较少