CAJ | 학술논문

利用MPTC型气泡压力张仪研究了十二烷基硫酸钠(SDS)溶液在不同NaCl浓度下的动态表面吸附性质,分析了离子型表面活性剂在表面吸附层和胶束中形成双电层结构产生表面电荷对动态表面扩散过程和胶束性质的影响.结果表明, SDS在表面吸附过程中,表面电荷的存在会产生5.5 kJ·mol-1的吸附势垒(Ea),显著降低十二烷基硫酸根离子(DS-)的有效扩散系数(Def ).十二烷基硫酸根离子的有效扩散系数与自扩散系数(D)的比值(Def/D)仅为0.013,这表明SDS与非离子型表面活性剂不同,在吸附初期为混合动力控制吸附机制.加入NaCl可以降低吸附势垒.当加入不小于80 mmol·L-1 NaCl后, Ea小于0.3 kJ·mol-1, Def/D在0.8-1.2之间,表现出与非离子型表面活性剂相同的扩散控制吸附机制.同时,通过分析SDS胶束溶液的动态表面张力获得了表征胶束解体速度的常数(k2).发现随着NaCl浓度的增大, k2减小,表明SDS胶束表面电荷的存在会增加十二烷基硫酸根离子间的排斥力,促进胶束解体.
이용MPTC형기포압력장의연구료십이완기류산납(SDS)용액재불동NaCl농도하적동태표면흡부성질,분석료리자형표면활성제재표면흡부층화효속중형성쌍전층결구산생표면전하대동태표면확산과정화효속성질적영향.결과표명, SDS재표면흡부과정중,표면전하적존재회산생5.5 kJ·mol-1적흡부세루(Ea),현저강저십이완기류산근리자(DS-)적유효확산계수(Def ).십이완기류산근리자적유효확산계수여자확산계수(D)적비치(Def/D)부위0.013,저표명SDS여비리자형표면활성제불동,재흡부초기위혼합동력공제흡부궤제.가입NaCl가이강저흡부세루.당가입불소우80 mmol·L-1 NaCl후, Ea소우0.3 kJ·mol-1, Def/D재0.8-1.2지간,표현출여비리자형표면활성제상동적확산공제흡부궤제.동시,통과분석SDS효속용액적동태표면장력획득료표정효속해체속도적상수(k2).발현수착NaCl농도적증대, k2감소,표명SDS효속표면전하적존재회증가십이완기류산근리자간적배척력,촉진효속해체.
The dynamic surface adsorption properties of aqueous sodium dodecyl sulfate (SDS) solutions were investigated at different concentrations of NaCl using bubble pressure tensiometry MPTC. In the case of ionic surfactants, the existence of a diffuse electric double layer on the surface adsorption layer and around the micel e produces a surface charge. Here, we discuss the influence of the surface charge on the dynamic surface diffusion processes and the micel e properties. It was found that the SDS adsorption process occurred in the presence of a 5.5 kJ·mol-1 adsorption barrier (Ea) that was generated by the surface charge; this barrier significantly decreased the effective diffusion coefficient (Def ) of the dodecyl sulfate ions (DS-). The ratio of the effective diffusion coefficient to the monomer self-diffusion coefficient (D) (Def/D) was only 0.013. This indicated that at the beginning, the adsorption of SDS fol owed the mixed kinetic-diffusion control ed model; this is different from the behavior observed for nonionic surfactants. The adsorption barrier was reduced when NaCl was added. Ea was less than 0.3 kJ·mol-1 after the addition of 80 mmol·L-1 of NaCl. This resulted in values of between 0.8 and 1.2 for Def/D, which was consistent with the diffusion-control ed model that describes the behavior of nonionic surfactants. The characteristic constants for the micel e dissociation rate (k2) were determined from the dynamic surface tension of the SDS micel e solutions. The calculated k values decreased as the NaCl concentration was increased, which demonstrated the existence of surface charge on the SDS micel es; this surface charge increased the repulsive forces between the dodecyl sulfate ions, and promoted the dispersion of the micel es.