复配表面活性剂对油水界面行为和性质影响的模拟研究

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。     

复配表面活性剂对油水界面行为和性质影响的模拟研究

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。     

烷基三甲基溴化铵添加剂对十二烷基硫酸钠水溶液表面活性的影响

研究了烷基三甲基溴化铵（Ｃ１２ＴＡＢ或Ｃ１４ＴＡＢ）作为添加剂对十二烷基硫酸钠（ＳＤＳ）水溶液表面活性的影响。实验结果表明,复配体系胶束生成和表面张力降低效率的局部增效均发生在Ｃ１２ＴＡＢ或Ｃ１４ＴＡＢ加入量仅约为ＳＤＳ的１／１００（Ｘ１≈０．０１）时。对于以ＳＤＳ为主成分的二元复配应用体系,当要求具有较高胶束生成能力或较高表面张力降低能力时,以添加烷基链长对称匹配的Ｃ１２ＴＡＢ为好;若希望具有良好的表面张力降低效率,则应加入单组分表面活性较高的Ｃ１４ＴＡＢ。     

Interfacial Dynamic Properties and Dilational Rheology of Sulfonate Gemini Surfactant and its Mixtures with Quaternary Ammonium Bromides at the Air–Water Interface

The dynamic interfacial properties and dilational rheology of gemini sulfonate surfactant (SGS) and its mixtures with quaternary ammonium bromides (DTAB, CTAB) at the air–water interface were investigated using drop shape analysis. Results suggest that the adsorption process of these surfactants is diffusion-controlled at dilute concentrations, whereas the adsorption mechanism gradually shifts to a mixed kinetic-diffusion control with increasing surfactant concentration. The mixed surfactant system possesses the best surface activity when the molar ratios of SGS/DTAB and SGS/CTAB mixtures are 9:10. The formation of catanionic complexes shields the electrostatic repulsion between surfactant molecules and lowers the electrostatic adsorption barrier. Therefore, SGS/DTAB and SGS/CTAB mixtures exhibit higher adsorption rates than either component alone. The effects of oscillating frequency and surfactant concentration on the surface dilational properties of SGS, DTAB, CTAB, SGS/DTAB, and SGS/CTAB mixtures were also determined. As the oscillating frequency increases, the dilational elasticity of these surfactants gradually increases. The dilational elasticity peaks at a certain concentration, which is less than the critical micelle concentration (CMC). Results show that the dilational elasticity of SGS/DTAB and SGS/CTAB mixtures is higher than that of either component, resulting from the formation of a denser monomolecular adsorption layer at the air–water interface. Our study provides a basis for understanding the interaction mechanism of catanionic surfactant mixtures containing Gemini surfactant at the air–water interface.     

1-丁基-3-甲基咪唑表面活性离子液体的界面膨胀流变行为研究

研究了1-丁基-3-甲基咪唑十二烷基硫酸盐([bmim][DS])和1-丁基-3-甲基咪唑二(2-乙基己基)磺基琥珀酸酯盐([bmin][AOT]两种表面活性离子液体在正庚烷/水界面的动态界面张力和膨胀特性。比较了[bmim][DS]或[bmin][AOT]和传统表面活性剂十二烷基硫酸钠(SDS)或二(2-乙基己基)磺基琥珀酸酯钠(Na[AOT])之间的膨胀弹性,并且考察了1-丁基-3-甲基咪唑阳离子之间静电相互作用对界面膜特性的影响。另外,通过对比[bmim][DS]和[bmim][AOT]在不同浓度下的膨胀弹性,验证了烷基链数量的改变对界面膨胀流变行为的影响。     

Influence of breakup and reformation of micelles on surfactant diffusion in pure and mixed micellar systems

Pulsed field gradient (PFG) NMR technique was used to study diffusion of surfactant ions in the following two micellar systems: (i) aqueous solution of an anionic surfactant sodium dodecyl sulfate (SDS), and (ii) aqueous solution of a mixture of SDS and a small amount of the cationic surfactant N-dodecyltrimethylammonium bromide (C₁₂TAB). PFG NMR measurements provided separate sets of data on diffusion of SDS and C₁₂TAB surfactant ions for a broad range of diffusion times. For each type of surfactants at least two components with different effective diffusivities were observed at sufficiently small diffusion times. The faster component was assigned to the surfactants that experience breakup or reformation of micelles during the diffusion time of the PFG NMR measurement, while the slower component was assigned to the surfactants that did not participate in such events during the diffusion time. The observed changes of the fractions and diffusivities of these components with increasing diffusion time were found to be in a qualitative agreement with such assignment. Fundamental understanding of surfactant diffusion in micellar system is important due to an increasing use of such systems for synthesis of porous materials where micelles are used as templates as well as for many other applications.     

New Interfacial Rheology Characteristics Measured Using a Spinning Drop Rheometer at the Optimum Formulation. Part 2. Surfactant–Oil–Water Systems with a High Volume of Middle-Phase Microemulsion

This article is a continuation of our first study on dilational interfacial rheology properties at optimum formulation for surfactant-oil–water systems at low surfactant concentration just above the cμc. Here, we have investigated a high content of middle-phase microemulsion with an optimum WIII phase behavior for a system containing sodium dodecyl sulfate, n-pentanol, and kerosene. A new oscillating spinning drop interfacial rheometer was used to measure the interfacial properties. The very low dilational elasticity moduli and phase angle found at or near hydrophilic–lipophilic deviation (HLD) = 0 are related to the presence of the bicontinuous phase microemulsion and to the fast surfactant exchanges between the bulk and the interface, regardless of the phases involved in the measurement using the spinning drop apparatus, i.e., the two-phase excess oil and excess water (O-W) or the bicontinuous microemulsion and excess water (M-W). We show that at or near optimum formulation, the interfacial tension and the dilational modulus for the M-W case almost instantly reach equilibrium, because of the high surfactant content in the microemulsion and the fast exchanges between the bulk and the interface. In contrast, when both excess phases (O-W) are measured, the changes in these properties are slower, due to the scarce presence of surfactants in both phases. The possibility of having almost all the surfactants trapped in the middle-phase bicontinuous microemulsion could explain the emulsion instability in all the WIII range. This is behaving as if there were no surfactant available in the oil and water phases to stabilize the oil or water droplets thus formed.     

Mixtures of anionic and cationic surfactants with single and twin head groups: Adsorption and precipitation studies

This research reports on the adsorption and precipitation of mixtures of anionic and cationic surfactants having single and twin head groups. The surfactant mixtures investigated were: (i) a single-head anionic surfactant, sodium dodecyl sulfate (SDS), in a mixture with the twin-head cationic surfactant pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD)—adsorption was studied on negatively charged silica; and (ii) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfonate (SHDPDS), and the single-head cationic surfactant dodecylpyridinium chloride (DPCI)—adsorption was studied on positively charged alumina. Whereas the mixed surfactant system of SHDPDS/DPCI showed adsorption on alumina that was comparable to the of SHDPDS alone, the mixed surfactant system of SDS/PODD showed increased adsorption on silica as compared with PODD alone. The adsorption of the SDS/PODD mixture increased as the anionic and cationic system approached an equimolar ratio. Precipitation diagrams for mixtures of single- and twin-head surfactant systems showed smaller precipitation areas than for single-head-only surfactant mixtures. Thus, the combination of single- and double-head surfactants helps reduce the precipitation region and can increase the adsorption levels, although the magnitude of the effect is a function of the specific surfactants used.     

油水界面上阴/阳离子型复配表面活性剂体系的分子动力学模拟

采油过程中阴/阳离子型表面活性剂复配使用可显著增强驱油效果,对其微观机理的深入研究有助于驱油用表面活性剂的结构优化设计及使用。采用分子动力学方法研究了不同摩尔比的阴离子表面活性剂聚醚羧酸钠(PECNa)和阳离子表面活性剂十八烷基三甲基氯化铵(OTAC)复配体系在油水界面上的分子行为和物理性质。结果表明,复配体系比单种表面活性剂体系更有利于降低油水界面张力。不同复配比体系中,两种表面活性剂头基相反电荷间的吸引作用使表面活性剂之间对各自反离子的静电吸引作用减弱,且等摩尔比体系尤为明显。阴离子表面活性剂的亲水头基对阳离子表面活性剂亲水头基形成的水化层内水分子的结构取向无显著影响,反之亦然。通过调节两种离子型表面活性剂的复配比例,可调整油水界面吸附层微观结构,有望降低油水界面张力,提高采收率。     

Amido-Amine-Based Cationic Gemini Surfactants: Thermal and Interfacial Properties and Interactions with Cationic Polyacrylamide

Experimental studies were conducted to investigate thermal and interfacial properties of two in‐house synthesized amido‐amine‐based cationic gemini surfactants namely: dodecanoic acid [3‐({4‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐butyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐4‐12 ) and dodecanoic acid [3‐({6‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐hexyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐6‐12 ). Thermogravimetric analysis showed the excellent thermal stability of surfactants and no structural degradation was observed at temperatures up to 250 °C. The long‐term thermal stability of the surfactants was investigated with the aid of spectroscopic techniques such as nuclear magnetic resonance (NMR (¹H and ¹³C) and Fourier transform infrared (FTIR) spectroscopy. Both surfactants were found to be thermally stable, and no changes in structure were observed after aging for 10 days at 90 °C. The interfacial tension of the surfactants was measured at three different temperatures (30, 60, and 80 °C), and the results showed a decrease in interfacial tension with increasing temperature and increasing spacer length of the surfactants. Rheological measurements were used to assess the interactions between the cationic gemini surfactant and cationic polyacrylamide. The addition of cationic surfactant reduced the viscosity and storage modulus of the polymer at low shear rate and frequency due to surfactant–polymer interactions and charge screening. The investigated surfactant–polymer system has great potential in high‐temperature carbonate reservoirs, where conventional anionic surfactants are not recommended due to high adsorption.     

New Interfacial Rheology Characteristics Measured using a Spinning‐Drop Rheometer at the Optimum Formulation of a Simple Surfactant–Oil–Water System

A new spinning‐drop tensiometer with an oscillating rotation velocity was used to measure the interfacial rheological properties of systems with very low interfacial tensions in the zone close to the so‐called optimum formulation of surfactant–oil–water systems. 2 simple formulation scans were selected: One with an extended anionic surfactant using a salinity variation in the water phase, and another with a mixture of 2 nonionic surfactants in a scan produced by changing their proportion. With both systems it was corroborated that at optimum formulation (i.e., at hydrophilic–lipophilic deviation (HLD) = 0), both the interfacial tension and the emulsion stability exhibit a deep minimum. A clear relationship was also found between the phase behavior and the interfacial rheological properties (dilational elasticity and viscosity). For the very first time and in both kinds of scans (salinity or average ethylene oxide number), it was found that the interfacial elastic modulus E and the interfacial viscosity, as well as the phase angle also exhibit a minimum at optimum formulation. These groundbreaking findings could be applied to emulsion instability at optimum formulation and to its applications in emulsion breaking.     

The Effects of Dynamic Noncovalent Interaction between Surfactants and Additional Salt on the pH-Switchable Interfacial Tension Variations

The dynamic noncovalent interaction between the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and 1,3-diphenylguanidine (DPG) was employed to control the interfacial activity of the surfactant. At high HCl concentration (1000 mg L⁻¹), the SDBS/DPGⁿ⁺ system could reduce the water/oil interfacial tension (IFT) to 10⁻⁴ mN m⁻¹ order of magnitude, which was much lower than the IFT values in the SDBS/DPG⁺ system with a low HCl concentration (100 mg L⁻¹) and the individual SDBS system by three and four orders of magnitude, respectively. The pH-switchable protonation of amido groups in DPG molecules determines the SDBS/DPG molecular interaction and the amplitude of IFT reduction, which was confirmed by control experiments using two other surfactants (sodium dodecyl sulfate [SDS] and dodecyl trimethylammonium bromide [DTAB]). Moreover, the investigation of the NaCl and temperature effects on the IFT indicated the intensity of mixed SDBS/DPGⁿ⁺ adsorption layers at the water/oil interface.     

表面活性剂和四烷基溴化铵的复配 Ⅱ.四乙基溴化铵对离子型表面活性剂在气/液表面吸附行为的影响

用表面张力法研究了有机电解质四乙基溴化铵（（Ｅｔ）４ＮＢｒ）对离子型表面活性剂十二烷基硫酸钠（ＳＤＳ）和十二烷基三甲基溴化铵（ＤＴＡＢ）在气／液表面吸附行为的影响。表明（Ｅｔ）４ＮＢｒ提高了ＳＤＳ和ＤＴＡＢ降低水溶液表面张力的效率。但（Ｅｔ）４ＮＢｒ仅提高ＤＴＡＢ降低水溶液表面张力的能力,却反而削弱了ＳＤＳ降低水溶液表面张力的能力。通常电解质对离子表面活性剂表面吸附层的影响主要来自与表面活性离子电性相反的反离子,它们屏蔽了表面活性剂离子头基间的电荷,致使表面活性剂在气／液表面层排列紧密。有机电解质离子（Ｅｔ）４Ｎ＋作为反离子时,除了具有电解质离子的通常性能外,其乙基和表面活性剂碳氢链间还有一定程度的弱疏水相互作用,使部分（Ｅｔ）４Ｎ＋离子嵌入ＳＤＳ吸附层的离子头基区中,较大（Ｅｔ）４Ｎ＋离子的嵌入使周围的ＳＤＳ碳氢链排列疏松,改变了朝向空气面的表面碳氢链覆盖层结构,从而削弱了其降低表面张力的能力。     

Aqueous dispersion of surfactant-modified multiwalled carbon nanotubes and their application as an antibacterial agent

The dispersing power of different surfactant-modified multiwalled carbon nanotubes (MWCNTs) and their effect on the antibacterial activity were examined. Three surfactants, including hexadecyltrimethylammonium bromide (CTAB), triton X-100 (TX-100) and sodium dodecyl sulfate (SDS) were tested. UV–vis absorbance, transmission electron microscopy and Fourier transform infrared spectroscopy were used to characterize the dispersion of MWCNTs in the aqueous phase, showing that the surfactant molecules had been adsorbed onto the MWCNTs’ surface. Among the three surfactants, TX-100 and CTAB provided maximum and minimum dispersion, respectively. The surfactant-modified MWCNTs exhibited different antibacterial activities to Streptococcus mutans. The fluorescence images showed that the surfactant-modified MWCNTs were not only capable of capturing bacteria and forming cell aggregates, but also killing them. Under the same concentration and treatment time, the CTAB-modified MWCNTs exhibited the strongest antibacterial activity compared to the TX-100 and SDS-modified MWCNTs. The optical density growth curves and viable cell number determined by the plating method suggested that the antibacterial activity of all surfactant-modified MWCNTs was both concentration- and treatment time-dependent.     

Physicochemical Properties of Novel Phosphobetaine Zwitterionic Surfactants and Mixed Systems with an Anionic Surfactant

A series of novel zwitterionic phosphobetaine (PPBT) surfactants were synthesized using long chain fatty alcohol, epichlorohydrin, dimethylamine and sodium dihydrogen phosphate as raw materials. The physicochemical properties of the phosphobetaine surfactants such as isoelectric point, foaming, surface tension, critical micelle concentration (CMC) and Krafft point were measured. Low CMC and surface tension values indicated the surface activities of the phosphobetaine surfactants were quite excellent. The CMC and surface tension values of PPBT/SDS mixed systems were determined. It was found both of CMC and surface tension values decreased compared with single surfactant system because of the association between dodecyl sulfate anions and cationic groups in phosphobetaine by electrostatic attraction.     

阴/阳离子表面活性剂复配微乳液体系的ε-β“鱼状”相图研究

用ε-β“鱼状”相图法研究了离子液体表面活性剂溴化1-十二烷基-3-甲基咪唑（C12mimBr）与十二烷基硫酸钠（SDS）复配形成的SDS-C12mimBr/正丁醇/正辛烷/5%NaCl水溶液微乳液体系的相行为和增溶性能。阴、阳离子表面活性剂以不等摩尔比复配,由于强烈的静电作用,产生显著的协同作用,使复配体系的增溶性能比单一表面活性剂得到了显著的提高。     

Influence of surfactants on flocculation and dewatering of kaolin suspensions by cationic polyacrylamide (PAM-C) flocculant

This paper reports the result of studies on flocculation and dewatering of kaolin suspensions by cationic polyacrylamide (PAM-C) flocculants in presence of surfactants. The surfactants used were namely anionic sodium dodecyl sulphate (SDS), cationic cetyl trimethyl ammonium bromide (CTAB) and non-ionic TritonX 100, which is a polyoxyethylenic ether compound. The unflocculated kaolin has a very slow settling rate of about 0.03 cm/s and can be improved by more than ten times using PAM-C as a flocculating agent. PAM-C adsorbs on kaolin primarily through electrostatic attraction and the flocculation is governed mainly by charge neutralisation and bridging. Partial pre-coating of kaolin with all three surfactants leads to both physical adsorption as well as chemisorption at PAM-C. Pretreating the kaolin with surfactants can further increase or decrease settling rate depending on the type of surfactant used. However, the flocs thus formed shows better filtration and dewatering behaviour estimated in terms of reduction in specific resistance to filtration (SRF) and cake moisture. The minimum SRF occurs under conditions corresponding to far lower adsorption of PAM-C than that for best flocculation. Simultaneous addition of PAM-C and each of the three surfactants decreases settling rate and sediment volume markedly and does not reduce SRF any further but they all reduce cake moisture substantially. The reduction in cake moisture for different PAM-C: surfactant mixture is in the following order: PAM-C: SDS (1:1)>PAM-C: TX 100(1:1)>PAM-C: CTAB(1:1). Low cake moisture in comparison with PAM-C alone, may be a result of reduction in entrapment of excess water in the smaller flocs formed by simultaneous addition with surfactants and to some extent due to hydrophobicity caused by adsorption of surfactants.     

Formation and characterization of liposomes from lipid/proteic material extracted from pig stratum corneum

The formation and physicochemical properties of liposomes prepared from a mixture of lipids and proteins extracted from pig stratum corneum have been investigated. The extraction of this material was carried out with chloroform/methanol mixtures. The sonication of these mixtures at 80°C in water that contained piperazine-1,4-bis(2-ethanesulfonic acid) led to the formation of bilayered structures (vesicle size of about 150 nm), which were stable to aggregation for more than 24 h. The interaction of these liposome suspensions (proteoliposomes) at a subsolubilizing level with surfactants indicates that the nonionic surfactant Triton X-100 had the largest capacity for altering liposome permeability, whereas the amphoteric surfactant dodecyl betaine exhibited the smallest. The anionic surfactant sodium dodecyl sulfate showed an intermediate activity relative to that shown by the other surfactants tested. Despite the fact that the proteoliposomes showed negligible permeability in the absence of surfactants, compared with that of phosphatidylcholine liposomes, addition of identical amounts of surfactants resulted after 45 min in similar permeability effects for both. However, the proteoliposomes appeared to be more resistant to the action of surfactants in the initial interaction period.     

温度及无机盐对LMEE和SDS混合溶液表面张力的影响

通过表面张力的测定,研究了温度和不同无机盐对月桂酸甲酯乙氧基化物(laurylmethylesterethoxylate,简称LMEE)与十二烷基硫酸钠(SDS)复配物表面张力及临界胶束浓度(CMC)的影响。研究表明:混合体系的CMC在很宽的复配比例内出现最低值,25℃、未加无机盐时可使CMC最低降至3 8×10-5mol/L;温度对复配体系表面张力的影响较小,温度上升复配物的CMC略有降低。3种价态无机盐的加入均可使复配物的CMC有所降低,但与单一表面活性剂相比,温度和无机盐对复配物的CMC影响均不大,说明复配体系的抗温变及抗盐能力均有增强。     

Mixtures of anionic and cationic surfactants with single and twin head groups: Solubilization and adsolubilization of styrene and ethylcyclohexane

Mixtures of anionic and cationic surfactants with single and twin head groups were used to solubilized styrene and ethylcyclohexane into mixed micelles and adsolubilize them into mixed admicelles on silica and alumina surfaces. Two combinations of anionic and cationic surfactants were studied: (i) a single-head anionic surfactant, sodium dodecyl sulfate (SDS), with a twin-head cationic surfactant, pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD), and (ii) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfonate (SHDPDS), with a single-head cationic surfactant, dodecylpyridinium chloride (DPCl). Mixtures of SDS/PODD showed solubilization synergism (increased oil solubilization capacity) when mixed at a molar ratio of 1∶3; however, the SHD-PDS/DPCl mixture at a ratio of 3∶1 did not show solubilization enhancement over SHDPDS alone. Adsolubilization studies of SDS/PODD (enriched in PODD) adsorbed on negatively charged silica and SHDPDS/DPCl adsorbed on positively charged alumina showed that while mixtures of anionic and cationic surfactants had little effect on the adsolubilization of styrene, the adsolubilization of ethylcyclohexane was greater in mixed SHPDS/DPCl systems than for SHDPDS alone. Finally, it was concluded that whereas mixing anionic and cationic surfactants with single and double head groups can improve the solubilization capacity of micelles or admicelles, the magnitude of the solubilization enhancement depends on the molecular structure of the surfactant and the ratio of anionic surfactant to cationic surfactant in the micelle or admicelle.