Interfacial activity of benzyloctadecyldimethyl ammonium chloride in a liquid/liquid extraction system

Interfacial tension and interfacial adsorption parameters for benzyloctadecyldimethyl ammonium chloride (BODMAC) in three organic diluents were determined and interpreted. The interfacial activity of BODMAC is affected by the type of the organic diluent and the composition of the aqueous phase. The general order of interfacial activity of BODMAC is n-heptane (5% isobutanol) > carbon tetrachloride > chloroform. The effectiveness of adsorption of BODMAC is not only dependent on the organic diluent, but also on the inorganic electrolytes in the aqueous phase.     

Estimation of trioctylphosphine oxide (TOPO) diffusion coefficients by dynamic adsorption measurements in model extraction systems

Equilibrium interfacial tension and surface excess isotherms for trioctylphosphine oxide (TOPO) were determined and interpreted. Despite its high hydrophobicity, TOPO adsorbs at the hydrocarbon/water interfaces and decreases effectively the interfacial tension. The interfacial activity of TOPO is affected by the type of organic diluent and the composition of the aqueous phase, i.e., the kind (HNO(3), KNO(3)) and the concentration of nonorganic electrolyte present in the system. Significant lowering of TOPO interfacial activity is observed with an increase of the aqueous phase acidity. The dynamic interfacial tension for TOPO was measured by using the drop volume technique. With the aid of the Ward and Tordai equation the values of the diffusion coefficients of TOPO were estimated. The values determined were in the right order of magnitude compared with the literature data.     

Interfacial activity of metal ion extractant

The interfacial activity of metal ion extractants is discussed. The interfacial tension isotherms are processed by matching the Szyszkowski equation, and estimation of selected parameters to discuss the interfacial activity of extractants. Results are presented in comprehensive tables and figures. The interfacial activity depends mainly on three different parameters; type of extractant, acidity of the aqueous phase and organic diluent. Strongly acidic extractants and protonated amine reagents exhibit the highest interfacial activity. The solvating reagents and non-protonated amines are on the opposite side of the scale, while the chelating reagents are somewhere in the middle. The acidity of the aqueous phase affects the interfacial activity of extractants, mainly by the ionisation (protonation and dissociation) of extractant molecules. Solvating diluents always decrease the interfacial activity of extractants.     

The effect of temperature on food emulsifiers at fluid-fluid interfaces

Heat-induced interfacial aggregation of a whey protein isolate (WPI) with a high content of beta-lactoglobulin (>92%), previously adsorbed at the oil-water interface, was studied by means of interfacial dynamic characteristics performed in an automatic drop tensiometer. Protein concentration in aqueous bulk phase ranging between 1x10(-1) and 1x10(-5) % wt/wt was studied as a variable. The experiments were carried out at temperatures ranging from 20-80 degrees C with different thermal regimes. During the heating period, competition exists between the effect of temperature on the film fluidity and the increase in mechanical properties associated with the interfacial gelation process. Interfacial crystallisation of food polar lipids (monopalmitin, monoolein, and monolaurin) previously adsorbed at the oil-water interface, was studied by interfacial dynamic characteristics (interfacial tension and surface dilational properties). The temperature, ranging between 40 and 2 degrees C, and the lipid concentration in aqueous oil phase, ranging between 1x10(-2) and 1x10(-4) % wt/wt, were studied as variables. Significant changes in interfacial dynamic characteristics associated with interfacial lipid crystallisation were observed as a function of lipid concentration in the bulk phase. Interfacial crystallisation of food polar lipids (monopalmitin, monoolein, and monolaurin) at the air-water interface, was studied by pi-A isotherms performed in a Langmuir trough coupled with Brewster angle microscopy (BAM). A condensation in monoglyceride monolayers towards lower molecular area was observed as the temperature decreased. This effect was attributed to lipid crystallisation at lower temperatures. BAM images corroborated the effect of temperature on the monolayer structure, as a function of the monoglyceride type.     

Aqueous surfactant solutions which exhibit ultra-low tensions at the oil-water interface

Ultra-low values of the tension at an oil-aqueous electrolyte solution interface can be developed by the addition of water-soluble surfactants of the petroleum sulfonate type. Interfacial tensions in the range of 10⁻³ dyne/cm or lower are readily achieved with surfactant concentrations of the order of 0.1 wt%. For a given oil and aqueous solution, the minimum interfacial tension resulting from the addition of a petroleum sulfonate depends markedly on the average equivalent weight of the sulfonate. Sulfonates having average equivalent weights higher and lower than a previously determined optimum weight, when mixed so as to yield this particular average weight, will also produce ultra-low interfacial tensions. For a given oil, additional control of this unusual type of interfacial activity is accomplished by adjustment of the electrolyte concentration of the aqueous phase.     

Interfacial activity of hydroxyoxime and the reaction order of copper extraction in toluene/water system

Interfacial tension dat for model 2-hydroxy-5-alkylbenzophenone E oximes at toluene/water interfaces was used to discuss different versions of the copper extraction mechanism. It was found that the interfacial tension isotherms are not specific enough to distinguish different interfacial behaviour of more and less hydrophobic hydroxyoximes, but if only the interfacial process is considered then the interfacial tension data demonstrate the extraction limiting step is the reaction between hydroxyoxime molecule present near the interface and the intermediate 1'1 complex. Only in this case are the predicted reaction orders aginst hydroxyoxime in agreement with order determined experimentally.     

Mass transfer model of triethylamine across the n-decane/water interface derived from dynamic interfacial tension experiments

This publication presents a detailed experimental and theoretical study of mass transfer of triethylamine (TEA) across the n-decane/water interface. In preliminary investigations, the partition of TEA between n-decane and water is determined. Based on the experimental finding that the dissociation of TEA takes place in the aqueous and in the organic phase, we assume that the interfacial mass transfer is mainly affected by adsorption and desorption of ionized TEA molecules at the liquid/liquid interface. Due to the amphiphilic structure of the dissociated TEA molecules, a dynamic interfacial tension measurement technique can be used to experimentally determine the interfacial mass transport. A model-based approach, which accounts for diffusive mass transport in the finite liquid bulk phases and for adsorption and desorption of ionized TEA molecules at the interface, is employed to analyze the experimental data. In the equilibrium state, the interfacial tension of dissociated TEA at the n-decane/water interface can be adequately described by the Langmuir isotherm. The comparison between the theoretical and the experimental dynamic interfacial tension data reveals that an additional activation energy barrier for adsorption and desorption at the interface has to be regarded to accurately describe the mass transport of TEA from the n-decane phase into the aqueous phase. Corresponding adsorption rate constants can be obtained by fitting the theoretical predictions to the experimental data. Interfacial tension measurements of mass transfer from the aqueous into the organic phase are characterized by interfacial instabilities caused by Marangoni convection, which result in an enhancement of the transfer rate across the interface.     

THE NATURE OF COLLOID AND INTERFACE OF MISCIBLE PHASE SYSTEM IN ALKALINE-SURFACTANT COMBINATION FLOODING

Several representative systems of surfactant + alkaline combination flooding are chosen to study in this paper, these systems are characterized in two points: The first: oil is miscible with water only by reversing them five to ten times, this miscible process is close to spontaneous. Interfacial tension between oil and aqueous is ultra-low. The second: this type of systems is high dispersion and can be stabilized in a period of time. These systems are observed by inicroscopy, polarizing microscopy, microcalorimetry, laser particles analysis instrument and interfacial tension meter, it is found that small particles are main constituent and special liquid crystals distributed on the surface of small particles exist. Small particles and special liquid crystals are responsible for producing ultra-low interfacial tension. The middle phase microemulsion of sodium dodecylsulfate is studied. By comparing difference and similarity between middle phase microemulsion and miscible system, mechanisms of forming low interfacial tension in miscible system and middle phase microemulsion are discussed initially.     

Revisiting the morphology development of solvent-swollen composite polymer particles at thermodynamic equilibrium

Morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA)/toluene droplets, in which phase separation proceeds, dispersed in SDS aqueous solution was examined. It changed from ex-centered PS-core/PMMA-shell to hemisphere with increasing SDS concentration. At low polymer weight fraction (wp), PS and PMMA phases contained non-negligible amount of PMMA and PS, respectively. The small amount of PS and PMMA in PMMA and PS phases, respectively, affected significantly the interfacial tension between polymer/toluene and aqueous solutions. Interfacial tension between PS and PMMA phases at low wp was measured by the spinning drop method, showing a quite low value ( approximately 10-2 mN/m). Predicted morphology obtained from calculation of minimum total interfacial free energy of the droplets using the interfacial tensions agreed well with the experimental observation.     

Surface activity of lysozyme and dipalmitoyl phosphatidylcholine vesicles at compressed and supercritical fluid interfaces

The surface activities of lysozyme and dipalmitoyl phosphatidylcholine (DPPC) vesicles at aqueous/compressed fluid interfaces are examined via high-pressure interfacial tension measurements using the pendant drop technique. The density and interfacial tension in compressible fluid systems vary significantly with pressure, providing a versatile medium for elucidating interactions between biomolecules and fluid interfaces and a method to elicit pressure-dependent interfacial morphological responses. The effects of lysozyme concentration (0.0008, 0.01, and 1 mg/mL) and pressure (> or = 7 MPa) on the dynamic surface response in the presence of ethane, propane, N2, and CO2 at 298 K were examined. Interfacial lysozyme adsorption reduced the induction phase and quickly led to interfacial tensions consistent with protein conformational changes and monolayer saturation at the compressed fluid interfaces. Protein adsorption, as indicated by surface pressure, correlated with calculated Hamaker constants for the compressed gases, denoting the importance of dispersion interactions. For DPPC at aqueous/compressed or aqueous/supercritical CO2 interfaces (1.8-20.7 MPa, 308 K), 2-3-fold reductions in interfacial tension were observed relative to the pure binary fluid system. The resulting surface pressures infer pressure-dependent morphological changes within the DPPC monolayer.     

Interfacial behavior of Cyanex 302 and kinetics of lanthanum extraction

In this paper, interfacial tension of Cyanex 302 is measured by a Sigma-701 tensiometer and the adsorption parameters are calculated according to the Gibbs and Szyszkowski adsorption isotherms. The interfacial adsorbed behavior of Cyanex 302 is investigated. The results demonstrate that the dimer is the predominant species in the bulk organic phase; however, the monomer is adsorbed at the interface and more interfacially active. The effects of aqueous pH, ion strength, and temperature on the interfacial activity of Cyanex 302 in heptane are discussed and explained in detail. The lower interfacial activity of Cyanex 302 in aromatic hydrocarbon than in aliphatic hydrocarbon has also been determined. The values of interfacial excess at the saturated interface increase in the order n-heptane>cyclohexane>toluene>benzene, which is consistent with the order of extractability of lanthanum by Cyanex 302 in these diluents. The interfacial activity data are used to discuss the kinetic mechanism of lanthanum(III) extraction. It is shown that an interfacial mechanism is very probable, and the extraction limiting step is the reaction between the Cyanex 302 molecules in the organic phase sublayer and the adsorbed intermediate complex.     

Interfacial tension in aqueous biopolymer-surfactant mixtures

The current study offers a first insight into the interfacial properties of pullulan-sodium dodecyl sulphate (SDS) aqueous two-phase systems (ATPS) in the presence of sodium chloride (NaCl). The effect of composition on the interfacial tension (sigma) in these ATPS was investigated over a wide range of pullulan, SDS and NaCl concentrations. An increase in the interfacial tension was observed with increasing pullulan and SDS concentrations and a small increase was also observed as the NaCl concentration was increased. In both cases the interfacial tension increases were closely related to the phase behaviour of these systems; as a consequence of increasing the pullulan, SDS and/or NaCl concentrations, the system moves further away from the critical point. In all systems interfacial tensions (of the order of muN/m) were comparable with those reported for polymer-polymer ATPS. Interfacial tensions sigma can be well correlated with the difference in pullulan and SDS concentrations between the phases (DeltaC pul and DeltaC SDS) and also the tie-line length (TLL); all yield straight lines on a log-log scale.     

Interfacial behavior of ACORGA CLX-50 and surface kinetics of copper extraction

Interfacial tension isotherms were determined and interpreted for ACORGA CLX-50. The hydration of extractant molecules in aqueous solution and at hydrocarbon/water interfaces was studied by molecular modelling. The usefulness of this technique to interpret the adsorption behavior was demonstrated. The interfacial kinetics was considered and relationships for various models of interfacial mechanism were derived and discussed. Despite its high hydrophobicity, ACORGA CLX 50 strongly adsorbs at the hydrocarbon/water interfaces and thus decreases effectively the interfacial tension. This high interfacial activity of ACORGA CLX 50 can be explained by the formation of hydrates. The interfacial tension isotherm can be well matched with the Szyszkowski equation. Molecular modelling suggests that ACORGA CLX 50 adsorbs at the hydrocarbon/water interface probably as a tetrahydrate containing two water molecules bonded to the same carbonyl oxygen atom (e.g., at position 3), one water molecule bonded to the oxygen atom of the second alkoxyl group (i.e., at position 5 when the hydration of carbonyl oxygen at position 3 is previously considered) and, finally, one water molecule bonded with the pyridine nitrogen atom. Positions 3 and 5 are equivalent. It is also shown that when the extraction of copper takes place in the kinetic regime, the reaction order with respect to ACORGA CLX 50 can change depending on the limiting step and the range of extractant concentration considered. Thus, a decrease of the extractant concentration from 10^?5M to 3·10^?3M causes a fall of the order with respect to ACORGA CLX 50 from 1 to 0 and 2 to 1 when the formation of the intermediate 1∶1 and final 2∶1 complexes are considered to be the limiting step, respectively.     

DTAB降低饱和烷烃与水的界面张力的研究

判断一种表面活性剂降低油-水界面张力性能的优劣,就需要对界面张力进行准确有效的测量。文章就不同浓度的十二烷基三甲基溴化铵(DTAB)水溶液分别与正庚烷(n-Heptane)和正十六烷(n-Hexadecane)之间的界面张力进行定量的测量,分别得到了在30℃下水-正庚烷和水-正十六烷体系的界面张力随DTAB浓度变化的曲线。结果表明,在DTAB浓度达到其所在体系中的CMC值时,水-正庚烷体系界面张力小于水-十六烷体系界面张力。DTAB具有较强的抗矿盐能力,界面张力随温度升高有所下降。     

Interfacial tension in phase-separated aqueous cationic/anionic surfactant mixtures

Interfacial tensions in two aqueous phase-separated cationic/anionic surfactant mixtures, CTAB/AS and 12-3-12/AS, without and with NaBr added were determined by the spinning drop method at 318.15 K. CTAB, 12-3-12 and AS are the abbreviations for cetyltrimethylammonium bromide, 1,3-propanediyl-bis(dodecyldimethylammonium bromide) and sodium dodecyl sulfonate, respectively. The interfacial tension sigma was found to be in the range of 0.06-21 microNm(-1). Toward a better understanding of the influence of the concentration difference between the separated phases in aqueous two-phase systems (ATPS) to interfacial tension, compositions of equilibrium phases were determined by elemental analysis coupled with material balance and electroneutrality. The investigation indicates that the concentration differences of surfactant ions between the separated phases and the adsorption of surfactant ions at the interface are the decisive factors determining the magnitude of interfacial tension.     

Partition and water/oil adsorption of some surfactants

Adsorption isotherms have been determined at the water/oil interface for five biphasic systems involving surfactants (non-ionic and ionic) present in both phases at partition equilibrium. The systems studied were polyoxyethylene(23)lauryl ether (Brij35) in water/hexane and four ionic surfactants, hexadecyltrimethylammonium bromide (CTAB), and a series of three tetraalkylammonium dodecylsulfate (TEADS, TPADS, and TBADS) in water/CH 2Cl 2. Interfacial tension measurements performed at the water/air and water/oil interfaces provided all the necessary information for the determination of the adsorption parameters by taking partition into account. These measurements also allowed the comparison of the adsorption properties at both interfaces which showed an increase of the adsorption equilibrium constant and a decrease of the maximum surface concentration at the water/oil interface compared to water/air. The values of the critical aggregation concentration showed, in all cases, that only the surfactant dissolved in the aqueous phase contribute to the decrease of the water/oil interfacial tension. In the case of the four ionic surfactants, the critical aggregation concentration obtained in biphasic conditions were lowered because of the formation of mixed surfactant-CH 2Cl 2 aggregates.     

Interfacial tension in a lower critical solution temperature blend: Effect of temperature,blend composition,and deformation of the interphase

Interfacial tension is a very important material parameter in two‐phase polymer blends. It determines the morphology development during processing, which is crucial for the end‐use properties of the material. Although different techniques for interfacial tension measurement give comparable results for immiscible polymers, the determination of the interfacial tension in lower critical solution temperature blends is not straightforward. This is illustrated for poly(α‐methyl styrene acrylonitrile)/poly(methyl methacrylate)(PαMSAN/PMMA), a slightly incompatible polymer pair. Interfacial tension has been measured with three different techniques: small‐amplitude oscillatory shear, recovery after elongation, and elongation of a multilayer sample. The large differences in these results can be attributed to the fact that most experimental techniques determine an apparent value, rather than the thermodynamic equilibrium value, of the interfacial tension. The latter is only obtained if the measurement is performed under quiescent conditions on a system that is composed of the coexisting PαMSAN‐rich and PMMA‐rich phases. The apparent interfacial tension depends on the actual composition of the phases and on the deformation of the interface. An order of magnitude approximation for such effects has been derived from theoretical considerations. Finally, each of these apparent values can be of practical importance. If a blend is prepared by melt mixing of the pure polymers, a high apparent value of interfacial tension should be considered. If, however, a blend is prepared by phase separation of a homogeneous mixture, the thermodynamic value is important. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 679–690, 2002     

正负离子混合表面活性剂双水相界面张力的研究

用旋转滴法测定了正负离子混合表面活性剂形成的双水相界面张力, 研究了双水相界面张力与表面活性剂的分子结构、正负离子表面活性剂的摩尔比、总浓度、外加无机盐及温度的关系. 结果表明, 双水相界面张力在一定正、负离子表面活性剂的摩尔比时属于超低界面张力范围. 观察到三种界面张力曲线类型, 第一类为摩尔比1:1 的两边的两条曲线, 界面张力随过剩表面活性剂组分的比例增加而降低; 第二类为一条跨过摩尔比1:1的马鞍型曲线; 第三类为位于摩尔比1:1的一边的一条马鞍型曲线. 界面张力曲线的类型主要取决于表面活性剂的分子结构, 包括亲水基类型、疏水链长度及对称性.     

Interfacial tension of the aqueous two-phase systems of cationic-anionic surfactant mixtures

Interfacial tensions of the aqueous two-phase systems formed by cationic-anionic surfactant mixtures were measured using spinning drop method. The effects of surfactant structure, molar ratio of cationic to anionic surfactants, surfactant concentration, salt, and temperature on the interfacial tensions were investigated. It was shown that the values of the interfacial tensions of the aqueous two-phase were in the scale of ultra-low interfacial tensions at certain molar ratios of cationic to anionic surfactants. Three types of interfacial tension curves were observed. The first curve comprised two curves that were located on either side of 1:1 molar ratio, and the interfacial tension decreased with the increase of excessive surfactant components. The second one was a saddle-shaped curve that strode over the 1:1 molar ratio. The third type was a saddle-shaped curve that was located beside the 1:1 molar ratio. The types of interfacial tensions depended on the molecular structure of the surfactants such as the hydrophilic groups and the lengths and symmetry of hydrophobic chains.     

Interfacial dilational behaviour of adsorbed β-lactoglobulin layers at the different fluid interfaces

β-Lactoglobulin adsorption layers at the interfaces solution/air, /tetradecan and /sunflower oil were characterised by dynamic interfacial tension measurements and harmonic drop oscillation experiments in a time scale of some seconds. Axialsymmetric drop shape analysis (ADSA) was used to calculate drop volume, area and interfacial tension. Within a definite range of drop volume amplitude, the oscillation of the surface tension is harmonic and interfacial dilation parameters can be determined. Dependence of the dilational parameters on the amplitude and frequency of drop volume oscillation were determined and methodical demands are given for this special kind of ADSA application. The concentration of interfacial saturation is minimal at the interface with sunflower oil. Interfacial dilational elasticities, and viscosities are maximal at the saturation concentration of all systems investigated. The dilational viscosities are maximal in the frequency range 0.007–0.011 Hz and characterise molecular rearrangement processes in the adsorption layer. Interfacial dilational elasticity and viscosity are the largest at the interface with air. They are the smallest at the interface with sunflower oil. Similarities and differences of the systems investigated are discussed by taking into account the adsorption behaviour and the solvatation of different apolar and polar parts of the protein molecules in the neighbouring phase.