Anionic and Cationic Surfactant Synergism: Minimizing Precipitation,Microemulsion Formation,and Enhanced Solubilization and Surface Modification

Anionic–cationic surfactant mixtures are known to exhibit synergistic effects (e.g., low critical micelle concentration, ultralow interfacial tension, middle phase microemulsion formulation, and increased solubilization and adsolubilization). However, the anionic–cationic surfactant mixtures are also prone to form other unique phases such as precipitates, gels, and coacervates in place of middle-phase microemulsions. Research summarized in this article demonstrates that asymmetric anionic–cationic surfactant mixtures have been shown to promote middle-phase microemulsions instead of these other phases, albeit with a slight decrease in synergism when using these asymmetric mixtures. The use of anionic–cationic surfactant mixtures also is shown to enhance or decrease surfactant adsorption depending on anionic–cationic surfactant ratios. Middle-phase microemulsion formation is demonstrated using anionic-rich or cationic-rich alcohol-free microemulsions by anionic–cationic ratio scans while also reducing or eliminating electrolyte requirement. Solubilization and adsolubilization are shown to increase for mixed anionic–cationic surfactant systems, especially for hydrophobic solutes. Thus, by exploiting these synergisms while avoiding phase separation, properly designed anionic–cationic surfactant mixtures can be advantageous for a wide range of applications.     

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.     

A test method for analyzing anionic or cationic surfactants in industrial water

A general 2-phase titration method is introduced for the quantitative identification of either anionic or cationic surface active agents commonly used in the domestic and industrial applications. Initially, an appropriate amount of quaternary ammonium compound is added to an unknown water sample to be analyzed and to ensure the treated sample contains excess amount of quaternary ammonium compound, and thus, is cationic in nature. The amount of excess quaternary ammonium compound is then quantitatively determined by titration with a standard anionic surfactant in the presence of methyl orange dye, buffer reagent, and chloroform. If the original surfactant in the tested sample is anionic, the anionic surfactant content (μM) is equal to the known amount (μM) of the added cationic quaternary ammonium compound minus the amount (μM) of standard anionic titrant spent in the neutralization reaction. If the original surfactant in the tested sample is cationic, the cationic surfactant content (μM) is equal to the amount (μM) of standard anionic titrant spent in the titration minus the known amount (μM) of the added cationic quaternary ammonium compound. The test procedure is simple and can be successfully completed within 5–7 min by a laboratory technician. For research or industrial application, a specific anionic or cationic surfactant to be used should be selected for the surfactant calibration. For the water quality control of unknown samples, the most common anionic surfactant, linear alkylate sulfonate, and the most common cationic surfactant, quaternary ammonium chloride, are selected as surfactant standards. The anionic surfactant concentration of a sample can be reported to be mg/liter as linear alkylate sulfonate while the cationic surfactant concentration of a sample can be reported to be mg/liter as cetyldimethylbenzylammonium chloride. Other alternatives for the use of the proposed general 2-phase titration method are suggested. Effective elimination of the interference caused by the presence of oil in an industrial water is also discussed. The proposed method is limited in application to the measurement of free ionic surface active agents only.     

Synergism and Performance for Systems Containing Binary Mixtures of Anionic/Cationic Surfactants for Enhanced Oil Recovery

The surfactant structure–performance relationship and application properties in enhanced oil recovery (EOR) for binary mixtures of anionic and cationic surfactants are presented and discussed. A polyoxyethylene ether carboxylate anionic surfactant was blended with a quaternary ammonium chloride cationic surfactant and tested for a high-temperature, low-salinity, and high-hardness condition as found in an oil reservoir. These mixtures were tailored by phase behavior tests to form optimal microemulsions with normal octane (n-C8) and crude oil having an API gravity of 48.05°. The ethoxy number of the polyoxyethylene carboxylate anionic surfactant and the chain length of the cationic surfactant were tuned to find an optimal surfactant blend. Interfacial tensions with n-C8 and with crude oil were measured. Synergism between anionic and cationic surfactants was indicated by surface tension measurement, CMC determination, calculation of surface excess concentrations and area per molecule of individual surfactants and their mixtures. Molecular interactions of anionic and cationic surfactants in mixed monolayers and aggregates were calculated by using regular solution theory to find molecular interaction parameters β ^σ and β ^M . Morphologies of surfactant solutions were studied by cryogenic TEM. The use of binary mixtures of anionic/cationic surfactants significantly broadens the scope of application for conventional chemical EOR methods.     

Ionic Behavior Assessment of Surface-Active Compounds from Corn Steep Liquor by Exchange Resins

Depending on their ionic nature, biosurfactants can be classified as nonionic, anionic, cationic, or amphoteric. The ionic behavior of biosurfactants is an important characteristic that dictates their use in industrial applications. In this work, a biosurfactant extract obtained from corn steep liquor was subjected to anionic or cationic resins, in order to study the ionic behavior under different operational conditions using response surface methodology. The independent variables included in the study are the dilution of biosurfactant solution, the amount of cationic or anionic resin, and the extraction time, whereas the dependent variables studied consisted of the surface tension of biosurfactant aqueous solution, after contacting with anionic or cationic resin. The results showed that biosurfactant extracted from corn steep liquor is amphoteric, since both resins were able to entrap this biosurfactant, making it particularly suited for use in personal care preparations for sensitive skin.     

Constant-temperature Dyeing Process for Nylon Fibres I—A Study of the Mechanisms

The various interactions that can occur in a dyebath containing nylon, an anionic dye, an anionic agent (Lissapol D) and a mildly cationic agent (Dispersol CWL) are described and discussed. A mechanism by which these agents influence the dyeing of nylon is postulated. The importance of considering the individual behaviour of anionic dyes in such a dyeing system is emphasised, since it is demonstrated that the strengths of the complexes formed between dye and cationic agent vary from dye to dye, in some instances being more stable and in others less stable than that between the anionic and the cationic agents.     

Flotation Mechanisms of Boron Minerals

Abstract

The development of reagent strategies for the flotation of boron minerals requires an understanding of flotation chemistry of reagent/mineral interactions. The floatability of a typical boron mineral, colemanite, was investigated in a microflotation cell by using anionic and cationic surfactants as collectors and tannic acid as a depressant. The results obtained with zeta potential measurements together with flotation tests reveal that colemanite is floatable with both anionic and cationic surfactants at its natural pH of 9.3. While the floatability of colemanite with anionic surfactants decreases with increasing pH, that with a cationic surfactant exhibits a maximum at pH 10.2, indicating the major role of electrostatic interactions in the system.     

合成型两性水凝胶研究进展

两性水凝胶因其良好的环境响应特性,而成为吸水保水材料领域的研究热点。以阴离子单体与阳离子单体共聚制备两性聚电解质水凝胶和内盐型两性离子单体聚合制备聚甜菜碱型水凝胶为重点,介绍了两性水凝胶的制备、溶胀特性以及性能改进等方面的国内外研究现状及发展趋势。     

Ionic graft copolymerization. VI. Graft copolymerization of β-propiolactone and N-vinylcarbazole onto trunk polymer containing carboxylic acid,sulfonic acid,and their salts

It was pointed out in previous papers that both cationic and anionic polymerization might be involved simultaneously in grafting onto trunk polymers containing ? COOH or ? SO₃Na. The graft copolymerization of β-Propiolactone (βPL)–N-vinylcarbazole (NVCZ) onto styrene-divinylbenzene copolymers containing carboxylic acid, sulfonic acid, and their salts was carried out in order to distinguish between the polymers produced by anionic and cationic mechanisms. The polymer obtained by the polymerization of βPL–NVCZ with BF₃·OEt₂, a typical cationic catalyst, consisted mainly of NVCZ units, but the polymer obtained with BuLi, a typical anionic catalyst, consisted mainly of βPL units. In the graft copolymerization of NVCZ–βPL onto trunk polymer containing ? COOH, the NVCZ contents of the branch polymer and the tolueneinsoluble fraction were estimated to be ca. 50 mole-%; therefore these polymers were produced by both cationic and anionic mechanisms. In the case of graft copolymerization onto the trunk polymer containing SO₃Na, it was found that both cationic and anionic polymerization also occurred simultaneously.     

Adsorption, Desorption and Adsolubilization Properties of Mixed Anionic Extended Surfactants and a Cationic Surfactant

Anionic and cationic surfactant mixtures exhibit desirable synergism, but are limited by their tendency to form precipitates. This research evaluates the adsorption, adsolubilization and desorption of mixtures of carboxylate-based anionic extended surfactants and a pyridinium-based cationic surfactant. The mixture of cetylpyridinium chloride (CPC), selected as the cationic surfactant, with four anionic extended surfactants were studied. The anionic surfactants studied were alkyl propoxylated ethoxylated carboxylate with average number of carbon chain length of 16 and 17 or 16 and 18 with 4?mol of propylene oxide groups and either 2 or 5?mol of ethylene oxide groups. The adsorption of anionic extended and cationic surfactant mixtures onto a negatively charged metal oxide surface (silica dioxide) was evaluated. The adsolubilization of phenylethanol, styrene and ethylcyclohexane were evaluated for these mixed surfactant systems. The desorption potential of individual and mixed surfactant systems was also evaluated by varying the number of washing (desorption) steps. It was found that the plateau adsorption of mixed anionic extended surfactant and cationic surfactant occurred at lower surfactant concentration than that of the CPC alone, although the maximum adsorption capacity of CPC was not enhanced in our mixed surfactant systems. Adsolubilization capacities of these mixed surfactant systems are higher than that of the individual surfactant system. For desorption studies, these mixed surfactant systems showed lower stability than the individual surfactant system.     

Water-soluble polymers as retention aids in a model papermaking system. III. Modified polyacrylamides

The pigment retention efficiency, in a model papermaking system, of anionically and cationically modified polyacrylamides was compared to that of the unmodified homopolymer. The anionic polyacrylamide is a much less efficient retention aid, especially at high pH's; the nonionic and cationic polymers perform similarly and without any marked pH dependence. However, it is the nonionic and anionic polyacrylamides which are similarly poor at fiber flocculation, at pH's between 4.5 and 7.5, whereas the cationic polymer is a good fiber flocculant. All three polymers stabilize pigment suspensions. The anionic polymer is not effective in heteroflocculation of mixed dispersions of fibers and pigment, whereas both the nonionic and cationic are good flocculants, the latter being less susceptible to overdosing. Equilibrium adsorption isotherms were determined; the cationic polymers is, unlike the other modified polyacrylamide, very well adsorbed by cellulose fibers. Onto titanium dioxide, polymers adsorbed in the order anionic < nonionic < cationic. A further differentiation of the cationic polymer is that it gives high pigment retention in sheet formation without markedly increasing the resistance to fluid flow through the forming sheet. Although a process of heteroflocculation is postulated for both nonionic and cationic polymers, in the former case it is thought that the primary adsorption is onto titanium dioxide, whereas with the latter it is onto cellulose.     

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。     

The effect of surfactants on peat dewatering

The effect of cationic, anionic and neutral surfactants on the mechanical dewatering of a highly decomposed fuelgrade peat has been examined. Surfactant adsorption and zeta potential of the peat particles correlated with dewatering of peat samples. The cationic surfactants had large positive effects on dewatering, the anionic surfactants had a negative effect while the neutral surfactant had no effect. The effects of the surfactants could be explained by charge neutralization and double layer suppression. The cationic surfactants were superior to analogous organic salts because of enhanced interaction by the hydrophobic effect.     

Adsorption of Anionic–Cationic Surfactant Mixtures on Metal oxide Surfaces

This research evaluates the adsorption of anionic and cationic surfactant mixtures on charged metal oxide surfaces (i.e., alumina and silica). For an anionic-rich surfactant mixture below the CMC, the adsorption of anionic surfactant was found to substantially increase with the addition of low mole fractions of cationic surfactant. Two anionic surfactants (sodium dodecyl sulfate and sodium dihexyl sulfosuccinate) and two cationic surfactants (dodecyl pyridinium chloride and benzethonium chloride) were studied to evaluate the effect of surfactant tail branching. While cationic surfactants were observed to co-adsorb with anionic surfactants onto positively charged surfaces, the plateau level of anionic surfactant adsorption (i.e., at or above the CMC) did not change significantly for anionic–cationic surfactant mixtures. At the same time, the adsorption of anionic surfactants onto alumina was dramatically reduced when present in cationic-rich micelles and the adsorption of cationic surfactants on silica was substantially reduced in the presence of anionic-rich micelles. This demonstrates that mixed micelle formation can effectively reduce the activity of the highly adsorbing surfactant and thus inhibit the adsorption of the surfactant, especially when the highly adsorbing surfactant is present at a low mole fraction in the mixed surfactant system. Thus surfactant adsorption can be either enhanced or inhibited using mixed anionic–cationic surfactant systems by varying the concentration and composition.

---

Modification and evaluation of membranes for vanadium redox battery applications

Several commercial ion exchange membranes were evaluated for application in the vanadium redox battery. The polyether membrane, DF120 cationic exchange membrane, showed the highest permeability to vanadium ions and the worst chemical stability in V(V) solution, while the divinylbenzene membrane, JAM anionic exchange membrane, showed the lowest permeability to vanadium ions and the best chemical stability in V(V) solution. In order to impart some cationic exchange capacity to the JAM anionic exchange membrane, sodium 4-styrenesulfonate was used to modify the anionic membrane by in situ polymerization. Measurements by infrared spectroscopy (IR) and cationic ion exchange capacity (IEC) verified that the modification procedure imparts cationic exchange capability to the membrane. Incorporation of cationic exchange groups to the anionic exchange membrane further results in a reduction in permeability to vanadium ions. The current and energy efficiencies averaged over 8 charge/discharge cycles of the cell with the treated JAM membrane were higher than that with the untreated JAM membrane. The current and energy efficiencies of the cell with the treated JAM membrane did not change over several charge/discharge cycles, which indicates good chemical stability of the treated membrane in the vanadium redox cell. The average efficiencies of the cell with the treated JAM membrane are higher than that with Nafion 117 over 8 charge/discharge cycles.     

Microemulsion phase behavior of anionic-cationic surfactant mixtures: Effect of tail branching

This research evaluated middle-phase microemulsion formation by varying the mole ratio of anionic and cationic surfactants in mixtures with four different oils (trichloroethylene, n-hexane, limonene, and n-hexadecane). Mixtures of a double-tailed anionic surfactant (sodium dihexyl sulfosuccinate, SDHS) and an unbalanced-tail (i.e., doubletailed with tails of different length) cationic surfactant (benzethonium chloride, BCl) were able to form microemulsions without alcohol addition. The amount of NaCl required to form the middle-phase microemulsion decreased dramatically as an equimolar anionic-cationic surfactant mixture was approached. Although the mixture of anionic and cationic surfactants demonstrated a higher critical microemulsion concentration (cμc) compared to the anionic surfactant alone, the Winsor Type IV single-phase microemulsion started at lower surfactant concentrations for the anionic-cationic mixture than for the anionic surfactant alone. Under optimum middlephase microemulsion conditions, mixed anionic-cationic surfactant systems solubilized more oil than the anionic surfactant alone. Pretreatment detergency studies were conducted to test the capacity of these mixed surfactant systems to remove oil form fabrics. It was found that anionic-rich mixed surfactant formulations yielded the largest oil removal, followed by cationic-rich systems.     

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.     

Sorption and diffusion of ionic dyes in anionic cellophane membranes

Experimental steady-state permeability studies have been made with non-ionic, anionic and cationic dyes using carboxy cellulose membranes as anionic substrates. The experimental results show that with increasing bulk ionic strength the diffusion velocities of anionic and cationic compounds increase and decrease, respectively. The diffusion behavior of non-ionic compounds is independent of the ionic strength. Empirical relationships have been deduced which fit the permeation data of the anionic compounds. A new concept is introduced which postulates that the diffusion behavior of colons within an anionic membrane is dependent on the basicity of the fixed ionic groups. In substrates with matrix-bound anionic groups of high basicity, such as carboxy cellulose, the permeability behavior is described in terms of a new diffusion mechanism referred to as the “fluctuating” charge mechanism. This concept can provide a semi-quantitative understanding of the different electrostatic obstruction effects which matrix-bound carboxylate and sulfonate groups have on the permeability of colons. The measured permeability of the counter ions is in qualitative agreement with the proposed diffusion model.     

阴离子表面活性剂与阳离子表面活性剂的相互作用(Ⅳ)——应用性能

介绍了阴/阳离子表面活性剂混合溶液在实际应用中的几个典型例子,包括在合成纳米材料中的应用、在萃取分离中的应用、作为药物传输载体的可能性、在乳化沥青中的应用等。最后指出,对阴离子/阳离子混合体系的研究迄今仍偏重于理论或基本性质以及一些实验室方面的应用研究,对该体系的实际工业产品中的使用研究总体较少,远远落后于基础研究,需要进一步深入。     

两性聚电解质在黄河高浊度水中的应用

本文合成了一系列不同阴、阳离子度的强碱弱酸型的两性聚电解质[丙烯酰胺(AM)-二甲基二烯丙基氯化铵(DMDAAC)-丙烯酸(AA)共聚物]。研究了阴、阳离子单体的配比对两性聚电解质分子量的影响;以及两性聚电解质阴、阳离子度对絮凝效果的影响。并将所合成的两性聚电解质作为絮凝剂,首次应用到黄河高浊度水的处理中。填补了国内两性聚电解质高分子絮凝剂应用于上水的空白。研究结果表明:在等电点范围内的两性聚电解质对黄河高浊度水的絮凝效果明显优于传统的非离子型、阳离子型及阴离子型絮凝剂。