Modeling the effects of mixed surfactants on the behaviors and properties of the oil-water interface with molecular dynamics

doi:10.11949/0438-1157.20220511

Abstract

Abstract:

Oilfield wastewater containing compound surfactants is a multi-component complex system, and the study of molecular interaction is helpful to determine the subsequent wastewater treatment plan. An interface model was established by using molecular dynamics (MD) simulation method. A series of calculations of interfacial properties and the experiment of interfacial tension were performed to examine the effects of two types of anionic/cationic surfactant mixtures on oil/water interfacial property with this model. In particular, this paper defines the concepts of the twist points of surfactants, molecular angles and synergistic energy. The results demonstrated that, compared with the single-component surfactant, the electrostatic attraction between the polar head groups with opposite charges present in mixed surfactants could induce these mixtures to improve the oil/water interface stability. In oil-water systems consisting of mixed surfactants, the intermolecular synergy of sodium dodecyl sulfate/cetyltrimethyl ammonium bromide (SDS/CTAB) mixtures can better enhance the stability of the system compared to sodium dodecyl sulfonate/cetyltrimethyl ammonium bromide (SLS/CTAB) mixtures. The compounding ratio range of SDS/CTAB mixtures that could better stabilize the oil-water interface was from 8/10 to 12/6, with 12/6 being the best. The results could provide programmatic guidance for crude oil extraction and oily wastewater treatment.

Key words: emulsion, surfactant, mixed system, molecular simulation, interface behavior, oil-water separation

摘要：

含复配表面活性剂的油田废水是一种多组分复杂体系，研究其中的分子作用关系有助于后续废水处理方案的确定。采用分子动力学(MD)模拟方法建立界面模型，通过定义表面活性剂的关键扭转点及相应的分子夹角、定义协同作用能，结合界面处的密度分布函数等性能模拟和界面张力测试结果，多角度分析两类阴阳离子表面活性剂复配对油水界面特性的影响。结果表明，与含单组分表面活性剂的油水体系相比，复配表面活性剂的相反电荷极性头基间静电吸引作用提高了油水界面稳定性；相较于十二烷基磺酸钠/十六烷基三甲基溴化铵(SLS/CTAB)复配体系，十二烷基硫酸钠/十六烷基三甲基溴化铵(SDS/CTAB)中分子间的协同作用可更好地提高体系的稳定性；当复配表面活性剂的配比为8/10~12/6时的油/水界面稳定效果较优、12/6时稳定性最好。研究结果可为石油开采及油水分离方案的确定提供依据。

关键词: 乳液, 表面活性剂, 复配体系, 分子模拟, 界面行为, 油水分离

CLC Number:

TQ 423.1

Yi LIAO, Yabin NIU, Yanqiu PAN, Lu YU. Modeling the effects of mixed surfactants on the behaviors and properties of the oil-water interface with molecular dynamics[J]. CIESC Journal, 2022, 73(9): 4003-4014.

廖艺, 牛亚宾, 潘艳秋, 俞路. 复配表面活性剂对油水界面行为和性质影响的模拟研究[J]. 化工学报, 2022, 73(9): 4003-4014.

Figures/Tables 15

Fig.1 Schematic diagram of the initial state of the model

Table 1 The number of molecules in simulated system

体系分类	n₁(ASAA)	n₂(CSAA)	水	油
单一体系(CSAA)	0	16	2000	50
复配体系(Mix)	4	13	2000	50
	8	10	2000	50
	9	9	2000	50
	12	6	2000	50
	16	3	2000	50
单一体系(ASAA)	20	0	2000	50
纯油水体系(Oil/Water)	—	—	2000	50

Fig.2 Energy variation of ASAA/CSAA system with time

Fig.3 Equilibrium diagram of SLS/CTAB system in YZ plane [SLS(purple), CTAB(blue); Anti-ion: Na+(orange), Br–(green)]

Table 2 Reduction of adsorption cross-sectional area at the oil-water interface of ASAA/CSAA system

复配比	ΔA_SDS/CTAB/nm²	ΔA_SLS/CTAB/nm²
4/13	0.42	0.38
8/10	0.52	0.48
9/9	0.45	0.38
12/6	0.43	0.37
16/3	0.26	0.23

Fig.4 Density distribution of different components and ions along Z-axis in ASAA/CSAA system

Fig.5 Schematic diagram of each angle of SDS

Fig.6 Distribution of the tilt angle of ASAA/CSAA system

Fig.7 Average of head base and tail base tilt angles of ASAA/CSAA system

Fig.8 The θHT distribution probability of each molecules in ASAA/CSAA system

Fig.9 The radial distribution function between S and N in head group of surfactants and O in water

Fig.10 Diffusion coefficients of water molecules in different interface regions

Fig.11 Schematic diagram of interfacial thickness

Fig.12 Interfacial thickness of each phase in ASAA/CSAA

Fig.13 Interfacial tension and synergistic energy of ASAA/CSAA system

References 39

1	Kamal M S, Hussein I A, Sultan A S. Review on surfactant flooding: phase behavior, retention, IFT, and field applications[J]. Energy & Fuels, 2017, 31(8): 7701-7720.
2	Sun Q, Zhang N, Fadlelmula M, et al. Structural regeneration of fracture-vug network in naturally fractured vuggy reservoirs[J]. Journal of Petroleum Science and Engineering, 2018, 165: 28-41.
3	La Mesa C, Risuleo G. Surface activity and efficiency of cat-anionic surfactant mixtures[J]. Frontiers in Chemistry, 2021, 9: 790873.
4	Guo H, Li Y Q, Kong D B, et al. Lessons learned from alkali/surfactant/polymer-flooding field tests in China[J]. SPE Reservoir Evaluation & Engineering, 2019, 22(1): 78-99.
5	陈勇. 丙烯酰胺/甲基丙烯酰氧乙基三甲基氯化铵反相乳液聚合[D]. 杭州: 浙江大学, 2018.
	Chen Y. Inverse emulsion polymerization of acrylamide/methylacryloylxyethyl trimethylammonium chloride[D]. Hangzhou: Zhejiang University, 2018.
6	吴中杰, 刘则艳, 谢连科, 等. 聚偏氟乙烯膜亲水改性及其乳液分离与重金属吸附应用[J]. 化工学报, 2021, 72: 421-429.
	Wu Z J, Liu Z Y, Xie L K, et al. Preparation of hydrophilic poly(vinylidene fluoride) membrane for oil/water emulsion separation and heavy metal ions adsorption[J]. CIESC Journal, 2021, 72: 421-429.
7	黄翔峰, 程航, 陆丽君, 等. 利用稳定性分析仪研究化学破乳过程[J]. 化工进展, 2010, 29(5): 825-830.
	Huang X F, Cheng H, Lu L J, et al. Investigation of chemical demulsification process by stability analyzer[J]. Chemical Industry and Engineering Progress, 2010, 29(5): 825-830.
8	Zhang G H, Chen Y, Sui X Y, et al. Nonionic surfactant stabilized polytetrafluoroethylene dispersion: effect of molecular structure and topology[J]. Journal of Molecular Liquids, 2022, 345: 116988.
9	Hjartnes T N, Mhatre S, Gao B C, et al. Demulsification of crude oil emulsions tracked by pulsed field gradient NMR (Ⅱ): Influence of chemical demulsifiers in external AC electric field[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2020, 586: 124188.
10	Sachin K M, Karpe S A, Singh M, et al. Self-assembly of sodium dodecylsulfate and dodecyltrimethylammonium bromide mixed surfactants with dyes in aqueous mixtures[J]. Royal Society Open Science, 2019, 6(3): 181979.
11	Okunade O A, Yekeen N, Padmanabhan E, et al. Shale core wettability alteration, foam and emulsion stabilization by surfactant: impact of surfactant concentration, rock surface roughness and nanoparticles[J]. Journal of Petroleum Science and Engineering, 2021, 207: 109139.
12	单晨旭, 曹绪龙, 祝仰文, 等. 辛基酚聚氧乙烯醚磺酸盐界面行为的分子动力学模拟[J]. 化工学报, 2016, 67(4): 1416-1423.
	Shan C X, Cao X L, Zhu Y W, et al. Molecular dynamics simulation for interface behavior of octylphenol polyoxyethylene ether sulfonate[J]. CIESC Journal, 2016, 67(4): 1416-1423.
13	贾海鹏, 苏勋家, 侯根良, 等. 石墨烯/聚苯胺纳米复合材料界面相互作用的分子动力学模拟[J]. 化工学报, 2013, 64(5): 1862-1868.
	Jia H P, Su X J, Hou G L, et al. Molecular dynamics simulation of interactions on graphene/polyaniline nanocomposites interface[J]. CIESC Journal, 2013, 64(5): 1862-1868.
14	Smit B, Hilbers P A J, Esselink K, et al. Computer simulations of a water/oil interface in the presence of micelles[J]. Nature, 1990, 348(6302): 624-625.
15	Smit B, Hilbers P A J, Esselink K, et al. Structure of a water/oil interface in the presence of micelles: a computer simulation study[J]. The Journal of Physical Chemistry, 1991, 95(16): 6361-6368.
16	Telo da Gama M M, Gubbins K E. Adsorption and orientation of amphiphilic molecules at a liquid-liquid interface[J]. Molecular Physics, 1986, 59(2): 227-239.
17	Ríos-López M, Mendez-Bermúdez J G, Vázquez-Sánchez M I, et al. Surface tension calculations of the cationic (CTAB) and the zwitterionic (SB₃-12) surfactants using new force field models: a computational study[J]. Molecular Physics, 2019, 117(23/24): 3632-3641.
18	Jia H, Lian P, Leng X, et al. Mechanism studies on the application of the mixed cationic/anionic surfactant systems to enhance oil recovery[J]. Fuel, 2019, 258: 116156.
19	Li J, Han Y, Qu G M, et al. Molecular dynamics simulation of the aggregation behavior of N-Dodecyl-N, N-dimethyl-3-ammonio-1-propanesulfonate/sodium dodecyl benzene sulfonate surfactant mixed system at oil/water interface[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017, 531: 73-80.
20	丛玉凤, 廖克俭, 翟玉春. 分子模拟在SBS改性沥青中的应用[J]. 化工学报, 2005, 56(5): 769-773.
	Cong Y F, Liao K J, Zhai Y C. Application of molecular simulation for study of SBS modified asphalt[J]. Journal of Chemical Industry and Engineering (China), 2005, 56(5): 769-773.
21	Liu H J, Liu Y, Shang Y Z, et al. Molecular simulation and experimental studies on the interfacial properties of a mixed surfactant SDS/C₄ mimBr[J]. Molecular Simulation, 2019, 45(3): 223-229.
22	Gan Y F, Cheng Q L, Wang Z H, et al. Molecular dynamics simulation of the microscopic mechanisms of the dissolution, diffusion and aggregation processes for waxy crystals in crude oil mixtures[J]. Journal of Petroleum Science and Engineering, 2019, 179: 56-69.
23	Dudek M, Kancir E, Øye G. Influence of the crude oil and water compositions on the quality of synthetic produced water[J]. Energy & Fuels, 2017, 31(4): 3708-3716.
24	谷莹露, 刘会娥, 陈爽, 等. 油水比对阴离子型微乳液相行为的影响[J]. 化工学报, 2019, 70(7): 2626-2635.
	Gu Y L, Liu H E, Chen S, et al. Effect of oil/water ratio on phase behavior of anionic micro-emulsion[J]. CIESC Journal, 2019, 70(7): 2626-2635.
25	张雪芳, 潘艳秋, 陈鹏鹏, 等. 乳化剂对动态膜分离油水乳化液过程的影响[J]. 化工进展, 2019, 38(2): 790-797.
	Zhang X F, Pan Y Q, Chen P P, et al. Impact of emulsifier on separation of oil-in-water emulsion by dynamic membrane[J]. Chemical Industry and Engineering Progress, 2019, 38(2): 790-797.
26	周家华, 崔英德. 表面活性剂HLB值的分析测定与计算(Ⅰ):HLB值的分析测定[J]. 精细石油化工, 2001, 18(2): 11-14.
	Zhou J H, Cui Y D. Measurement and calculation of HLB value of surfactants (Ⅰ): The measurement of HLB value[J]. Speciality Petrochemicals, 2001, 18(2): 11-14.
27	Jang S S, Lin S T, Maiti P K, et al. Molecular dynamics study of a surfactant-mediated decane-water interface: effect of molecular architecture of alkyl benzene sulfonate[J]. The Journal of Physical Chemistry B, 2004, 108(32): 12130-12140.
28	Chanda J, Chakraborty S, Bandyopadhyay S. Monolayer of aerosol-OT surfactants adsorbed at the air/water interface: an atomistic computer simulation study[J]. The Journal of Physical Chemistry B, 2005, 109(1): 471-479.
29	江蓉君, 罗健辉, 白瑞兵, 等. 多元体系油水界面上常见表面活性剂行为的分子动力学模拟[J]. 高等学校化学学报, 2017, 38(10): 1804-1812.
	Jiang R J, Luo J H, Bai R B, et al. Molecular dynamics simulation on behavior of common surfactants at the oil/water interface in complex systems[J]. Chemical Journal of Chinese Universities, 2017, 38(10): 1804-1812.
30	Rehman N, Haq Z U, Ullah H, et al. Interactions of cationic surfactant cetyl-trimethyl ammonium bromide with ammonium nitrate: surface and thermodynamic studies[J]. Chinese Journal of Chemical Physics, 2021, 34(4): 480-486.
31	崔正刚. 表面活性剂, 胶体与界面化学基础[M]. 北京: 化学工业出版社, 2003: 327-330.
	Cui Z G. Fundamentals of Surfactants, Colloids, and Interface Chemistry[M]. Beijing: Chemical Industry Press, 2003: 327-330.
32	Liao X J, Wang Y Q, Liao Y, et al. Effects of different surfactant properties on anti-wetting behaviours of an omniphobic membrane in membrane distillation[J]. Journal of Membrane Science, 2021, 634: 119433.
33	Sohrabi B, Gharibi H, Tajik B, et al. Molecular interactions of cationic and anionic surfactants in mixed monolayers and aggregates[J]. The Journal of Physical Chemistry. B, 2008, 112(47): 14869-14876.
34	Chen L, Xiao J X, Ruan K, et al. Homogeneous solutions of equimolar mixed cationic-anionic surfactants[J]. Langmuir, 2002, 18(20): 7250-7252.
35	Tah B, Pal P, Mahato M, et al. Aggregation behavior of SDS/CTAB catanionic surfactant mixture in aqueous solution and at the air/water interface[J]. The Journal of Physical Chemistry. B, 2011, 115(26): 8493-8499.
36	Afrin T, Karobi S N, Rahman M M, et al. Water structure modification by sugars and its consequence on micellization behavior of cetyltrimethylammonium bromide in aqueous solution[J]. Journal of Solution Chemistry, 2013, 42(7): 1488-1499.
37	Sarangi D, Samantaray A C, Sahu R, et al. Interactions of cetyltrimethylammonium bromide with 1, 3-dioxolane in water: a study of viscosity and volumetric properties[J]. Asian Journal of Chemistry, 2019, 32(1): 53-58.
38	Bruździak P, Panuszko A, Kaczkowska E, et al. Taurine as a water structure breaker and protein stabilizer[J]. Amino Acids, 2018, 50(1): 125-140.
39	Alejandre J, Tildesley D J, Chapela G A. Molecular dynamics simulation of the orthobaric densities and surface tension of water[J]. The Journal of Chemical Physics, 1995, 102(11): 4574-4583.

[1]	Minghao SONG, Fei ZHAO, Shuqing LIU, Guoxuan LI, Sheng YANG, Zhigang LEI. Multi-scale simulation and study of volatile phenols removal from simulated oil by ionic liquids [J]. CIESC Journal, 2023, 74(9): 3654-3664.
[2]	Jianbo HU, Hongchao LIU, Qi HU, Meiying HUANG, Xianyu SONG, Shuangliang ZHAO. Molecular dynamics simulation insight into translocation behavior of organic cage across the cellular membrane [J]. CIESC Journal, 2023, 74(9): 3756-3765.
[3]	Jiajia ZHAO, Shixiang TIAN, Peng LI, Honggao XIE. Microscopic mechanism of SiO₂-H₂O nanofluids to enhance the wettability of coal dust [J]. CIESC Journal, 2023, 74(9): 3931-3945.
[4]	Xin YANG, Xiao PENG, Kairu XUE, Mengwei SU, Yan WU. Preparation of molecularly imprinted-TiO₂ and its properties of photoelectrocatalytic degradation of solubilized PHE [J]. CIESC Journal, 2023, 74(8): 3564-3571.
[5]	Linzheng WANG, Yubing LU, Ruizhi ZHANG, Yonghao LUO. Analysis on thermal oxidation characteristics of VOCs based on molecular dynamics simulation [J]. CIESC Journal, 2023, 74(8): 3242-3255.
[6]	Ji CHEN, Ze HONG, Zhao LEI, Qiang LING, Zhigang ZHAO, Chenhui PENG, Ping CUI. Study on coke dissolution loss reaction and its mechanism based on molecular dynamics simulations [J]. CIESC Journal, 2023, 74(7): 2935-2946.
[7]	Xiaoling TANG, Jiarui WANG, Xuanye ZHU, Renchao ZHENG. Biosynthesis of chiral epichlorohydrin by halohydrin dehalogenase based on Pickering emulsion system [J]. CIESC Journal, 2023, 74(7): 2926-2934.
[8]	Ming DONG, Jinliang XU, Guanglin LIU. Molecular dynamics study on heterogeneous characteristics of supercritical water [J]. CIESC Journal, 2023, 74(7): 2836-2847.
[9]	Ao ZHANG, Yingwu LUO. Low modulus, high elasticity and high peel adhesion acrylate pressure sensitive adhesives [J]. CIESC Journal, 2023, 74(7): 3079-3092.
[10]	Yuanchao LIU, Xuhao JIANG, Ke SHAO, Yifan XU, Jianbin ZHONG, Zhuan LI. Influence of geometrical dimensions and defects on the thermal transport properties of graphyne nanoribbons [J]. CIESC Journal, 2023, 74(6): 2708-2716.
[11]	Wenchao XU, Zhigao SUN, Cuimin LI, Juan LI, Haifeng HUANG. Effect of surfactant E-1310 on the formation of HCFC-141b hydrate under static conditions [J]. CIESC Journal, 2023, 74(5): 2179-2185.
[12]	Hao GU, Fujian ZHANG, Zhen LIU, Wenxuan ZHOU, Peng ZHANG, Zhongqiang ZHANG. Desalination performance and mechanism of porous graphene membrane in temporal dimension under mechanical-electrical coupling [J]. CIESC Journal, 2023, 74(5): 2067-2074.
[13]	Chenxin LI, Yanqiu PAN, Liu HE, Yabin NIU, Lu YU. Carbon membrane model based on carbon microcrystal structure and its gas separation simulation [J]. CIESC Journal, 2023, 74(5): 2057-2066.
[14]	Yuntong GE, Wei WANG, Kai LI, Fan XIAO, Zhipeng YU, Jing GONG. AFM study of the interaction forces between micro-oil droplets and modified silica surfaces in multiphase dispersion systems [J]. CIESC Journal, 2023, 74(4): 1651-1659.
[15]	Xianxian RAO, Miao DU, Guorong SHAN, Pengju PAN. Effect of different metal salt demulsifiers on vulcanization behavior of isobutylene isoprene rubber [J]. CIESC Journal, 2023, 74(2): 756-765.