油水界面上表面活性剂的脱附动力学及其离子调控  

Kinetics and ionic regulation of surfactants desorption at the oil-water interfaces

作　　者：温伯尧[1] 杨海中[2] 姚秀田[3] 骆政园[1] 白博峰[1] Boyao Wen;Haizhong Yang;Xiutian Yao;Zhengyuan Luo;Bofeng Bai(State Key Laboratory of Maliphase Flow in Power Engineering,Xian Jiaotong Universiy,Xian 710049,China;Gudong Oil Production Plant,Shengli Oilfield Company,SINOPEC,Dongying 257237,China;Gudao Oil Production Plant,Shengli Oifield Company,SINOPEC,Dongying 257231,China)

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,西安710049 [2]中石化胜利油田分公司孤东采油厂,东营257237 [3]中石化胜利油田分公司孤岛采油厂,东营257231

出　　处：《科学通报》2022年第25期3088-3096,共9页Chinese Science Bulletin

基　　金：国家自然科学基金(51976160)资助。

摘　　要：界面吸附/脱附过程是油水界面上表面活性剂聚集行为的关键限速步骤,探明其动力学特性对于揭示表面活性剂界面吸附及调控机制具有重要意义.本文采用耦合伞状采样的粗粒度分子动力学方法研究了癸烷-水界面上十二烷基硫酸钠(sodium dodecyl sulfate,SDS)分子的脱附过程,揭示了离子影响SDS分子界面脱附动力学及界面张力的微观机制.基于伞状采样模拟和Smoluchowski方程,获得了表面活性剂界面脱附自由能和脱附时间,实现了表面活性剂界面脱附动力学的定量描述;发现了离子对表面活性剂界面脱附具有抑制作用,表面活性剂的脱附自由能和脱附时间均随离子浓度增加而增大,揭示了其主要机制为离子静电屏蔽引起的表面活性剂分子间相互作用减弱,静电屏蔽更强的钙离子具有更显著的抑制效果;通过分析表面活性剂界面脱附和界面张力变化可知,SDS分子脱附能力与其降低界面张力的能力呈负相关关系,离子通过抑制SDS分子脱附减弱了其降低界面张力的能力,钙离子的影响更为显著.The oil-water interface plays a crucial role in daily life and many industrial processes(such as oil extraction, emulsion preparation, material assembly, drug transportation, etc.). With the development of scientific research and engineering applications, the structures and properties of the oil-water interfaces are becoming the focus and the advanced subjects of multiphase flow, colloid and interface chemistry, microfluidics, material assembly and many other fields, and are more difficult to be predicted and described via the existing methods and theories. Surfactants, which are amphiphilic molecules,can spontaneously adsorb at the oil-water interfaces and have been proved to be effective materials for regulating the structures, mass transfer and mechanics of the oil-water interface. It is of great significance to investigate the surfactant kinetics at the oil-water interface for revealing the interfacial adsorption and regulation mechanisms of surfactants. The adsorption/desorption process is the rate-limiting step of surfactant kinetics at the oil-water interface. However, many studies focus on the relaxation process of surfactant adsorption, and the effects of ions in the aqueous phase on the surfactant adsorption/desorption kinetics are scarcely investigated. In this paper, by combing the coarse-grained molecular dynamics simulations and the umbrella sampling method, we study the desorption process of SDS surfactants from the decane-water interface and reveal the mechanisms of ions affecting the desorption kinetics and interfacial tension by analyzing the surfactant desorption kinetics via the desorption free energy and desorption time. The results show that ionic species and concentration have great influence on the ionic number density and SDS-ion interaction near the interface, but show little effects on the number density and molecular conformation of surfactants at the interfaces. Based on the umbrella sampling simulation and Smoluchowski equation, we give an accurate and quantitative description of the

关 键 词：油水界面 表面活性剂脱附 离子调控 分子动力学 自由能 

分 类 号：TE357.46[石油与天然气工程—油气田开发工程]