| 表面活性剂对气-液界面纳米颗粒吸附规律的影响 |
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| 引用本文： | 张旋,张天赐,葛际江,蒋平,张贵才.表面活性剂对气-液界面纳米颗粒吸附规律的影响[J].物理学报,2020(2):211-218. |
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| 作者姓名： | 张旋 张天赐 葛际江 蒋平 张贵才 |
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| 作者单位： | 中国石油大学（华东）石油工程学院 |
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| 基金项目： | 国家自然科学基金(批准号:51574266);中央高校基本科研业务费(批准号:17CX06012)资助的课题~~ |
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| 摘 要： | 通过测定及分析纳米颗粒和表面活性剂-纳米颗粒复配体系在自由吸附过程与动态收缩过程中表面张力的变化,总结了纳米颗粒在气-液界面的吸附排布规律以及表面活性剂对其吸附规律的影响.实验结果表明,自由吸附过程中,随矿化度增加、阳离子活性剂浓度增加,平衡表面张力降低,这与颗粒吸附密度增加及颗粒润湿性改变有关.浓度低于临界胶束浓度(CMC)时,阳离子活性剂体系与混合体系的表面张力差异证明了阳离子活性剂可以通过静电作用吸附于纳米颗粒表面,进而部分溶解于水相;而阴离子活性剂与纳米颗粒相互作用力较弱,对表面张力影响较小.纳米颗粒体系在液滴收缩过程中,表面张力从自由吸附平衡态进一步降低大约9 m N/m,说明自由吸附过程中纳米颗粒不能达到紧密排布;同时表面张力呈现为缓慢降低、快速降低和达到平衡三部分,表面压缩模量可达70 m N/m,满足了液膜Gibbs稳定准则,这将有助于提高泡沫或者乳液稳定性.纳米颗粒-表面活性剂体系在液滴收缩过程中表面张力降低值随活性剂浓度增加而减小;表面压缩模量由高到低依次为:纳米颗粒>阳离子活性剂-纳米颗粒>阴离子-纳米颗粒>表面活性剂.
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| 关 键 词： | 纳米颗粒 界面吸附 表面张力 表面扩张/压缩模量 |
Effect of surfactants on adsorption behavior of nanoparicles at gas-liquid surface |
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| Zhang Xuan,Zhang Tian-Ci,Ge Ji-Jiang,Jiang Ping,Zhang Gui-Cai.Effect of surfactants on adsorption behavior of nanoparicles at gas-liquid surface[J].Acta Physica Sinica,2020(2):211-218. |
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| Authors: | Zhang Xuan Zhang Tian-Ci Ge Ji-Jiang Jiang Ping Zhang Gui-Cai |
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| Affiliation: | (College of Petroleum Engineering,China University of Petroleum,Qingdao 266580,China) |
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| Abstract: | Silica nanoparticles(NPs) are more and more useful in many engineering areas, but the dynamic behaviors of adsorption of NPs at surface are not clear, especially when there exist surfactants on the surface. The modified NPs with the nonionic dimethyl silane are partially hydrophobic, and in this paper, the surface behavior is investigated which is determined by interfacial tension and surface compression modulus. It is concluded that the dimethyl silane coverage, the brine salinity and the surfactant would affect the NPs’ adsorption. Higher salinity in brine or higher dimethyl silane coverage causes lower steady state surface tension,which is related to the hydrophobicity and adsorption amount of NPs at the surface. When the cationic surfactant concentration is lower than critical micelle concentration(CMC), the surface tension of mixture system is a little bit higher than cationic surfactant’s. Cationic surfactant can be adsorbed at NPs’ surface to change the hydrophobicity based on the electrostatic attraction, and then some surfactants are dissolved in liquid phase together with NPs, while the anionic surfactant will not do so. In the shrinking droplet process, the surface tension of the NPs with 1.5 μmol/m^2 dimethyl silane decreases from ~59 m N/m at the steady state to^50 m N/m, which proves that the NPs’ adsorption density can be higher even after infinite long time equilibrium due to the repulsive force between the NPs. Besides, the curve of interfacial tension(IFT) versus surface area shows three parts with different declining slopes. In the first part, the relatively low adsorption of NPs at the surface means weak interaction between NPs. Then in the second part, due to the irreversible adsorption, the spacing between NPs decreases with adsorption amount increasing and surface area lowering, so the increasing of NPs’ interaction leads to high surface compression modulus. After that, the IFT curve keeps flat since the NPs assembly reaches to the closest peck. With the increase of NPs’ hydrophobicity, the compression modulus increases up to ~70 m N/m, which satisfies the Gibbs criterion to resist coarsening of the foam or emulsion. However, for the mixing system, increasing surfactant concentration leads to a lower surface tension at steady state, then the surface tension difference or compression modulus decreases too. Finally, we find that the compression modulus order from high to low is as follows: NPs, cationic surfactant-NPs, anionic surfactant-NPs, surfactants. This investigation is meaningful for accounting for the enhancement of foam or emulsion stability with NPs affected by salinity and surfactant. |
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| Keywords: | nanoparticles adsorption at interface surface tension surface dilatational modulus and compression modulus |
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