Formulating middle-phase microemulsions using mixed anionic and cationic surfactant systems

Although mixtures of anionic and cationic surfactants can show great synergism, their potential to precipitate and form liquid crystals has limited their use. Previous studies have shown that alcohol addition can prevent liquid crystal formation, thereby allowing formation of middle-phase microemulsions with mixed anionic-cationic systems. This research investigates the role of surfactant selection in designing alcohol-free anionic-cationic microemulsions. Microemulsion phase behavior was studied for three anionic-cationic surfactant systems and three oils of widely varying hydrophobicity [trichloroethylene (TCE), hexane, and n-hexadecane]. Consistent with our hypothesis, using a branched surfactant and surfactants with varying tail length allowed us to form alcohol-free middle-phase microemulsion using mixed anionic-cationic systems (i.e., liquid crystals did not form). The anionic to cationic molar ratio required to form middle-phase microemulsions approached 1∶1 for univalent surfactants as oil hydrophobicity increased (i.e., TCE to hexane to n-hexadecane); even for these equimolar systems, liquid crystal formation was avoided. To test the use of these anionic-cationic surfactant mixtures in surfactant-enhanced subsurface remediation, we performed soil column studies: Greater than 95% of the oil was extracted in 2.5 pore volumes using an anionic-rich surfactant system. By contrast, cationic-rich systems performed very poorly (<1% oil removal), reflecting significant losses of the cationic-rich surfactant system in the porous media. The results thus suggest that, when properly designed, anionic-rich mixtures of anionic and cationic surfactants can be efficient for environmental remediation. By corollary, other industrial applications and consumer products should also find these mixtures advantageous.     

纳米二氧化钛的微乳液制法

介绍了影响微乳液法制备纳米二氧化钛微粒的因素、国内外的研究动态和进展以及最新的研究热点。     

农药新剂型--微乳剂

随着人们对保护环境的重视,国内外农药的剂型正朝着绿色化的方向发展。目前,我国的农药剂型研究比较落后,老剂型乳油(EC)和可湿性粉剂(WP)两者占主要,而且剂型比较单一。本文首先介绍了我国农药剂型加工使用现状及其发展方向,然后介绍了一种以水为介质的新剂型———微乳剂,对其特性、结构类型、研究方法、形成理论、质量指标及优缺点进行了介绍。同时,还简述了国内微乳剂型的现状和发展趋势。     

微乳技术在食品化学中的应用

介绍了微乳的概念、形成理论、组成以及微乳液制备过程中的一些关键问题,由于微乳液的特殊理化性质,使得这种新技术在食品化学领域具有相当潜在的应用前景。     

Phase behavior and structural properties for the triton X-100/<Emphasis Type="Italic">n</Emphasis>-C<Subscript>n</Subscript>H<Subscript>2n+1</Subscript>COOH/H<Subscript>2</Subscript>O system

In the Triton X-100/n-C_nH_2n+1COOH/H₂O system, n-C_nH_2n+1COOH can be used as a cosurfactant. As its chain length increases, the regions of the microemulsions showing oil-in-water (O/W), water-in-oil (W/O), and bicontinuous structures decrease and at the same time, the region of the lamellar liquid crystal increases. In the O/W region, the distribution coefficient K of n-C_nH_2n+1COOH between Triton X-100 micellar phase and water phase increases with the chain length of saturated unbranched monocarboxylic acid. The relationship between the standard solubilization Gibbs free energy of saturated unbranched monocarboxylic acid and the number of methylene groups in the saturated unbranched monocarboxylic acid is given by the equation: ΔG _m ⁰=−2.364−2.818 n(CH₂) kJ·mol⁻¹ in the Triton X-100 micellar system. In the lamellar liquid crystal region, small-angle X-ray diffraction shows that the thickness of the bilayer d ₀ is independent of the weight ratio of n-C_nH_2n+1COOH to Triton X-100, but the volume of the solvent penetrating from the solvent layer to the amphiphilic bilayer increases with the weight ratio of n-C_nH_2n+1COOH to Triton X-100. Furthermore, the d ₀ value increases with the chain length of saturated unbranched monocarboxylic acid, which will contribute to the formation and stabilization of the lamellar liquid crystal.     

水相和特殊介质中有序聚集体的结构、性质和应用(VI)——反相胶束/微乳液、反相溶致液晶和囊泡

主要介绍了表面活性剂在非水溶剂中形成的各种反相结构体系,其中包括反相胶束/微乳液、溶致液晶以及传统和一些有特殊结构的囊泡体系。同时介绍了用近代测试手段对相应有序聚集体的性能和结构的表征。最后对它们的重要应用也做了介绍,如应用于合成纳米材料的模板,药物载体以及在萃取提纯等方面。     

Ag@SiO_2核壳纳米粒子的制备与表征

以NaBH4作还原剂,TEOS为前体,采用反相微乳液法制得粒径50～100nm的Ag@SiO2核壳纳米粒子,其中Ag核为面心立方结构,壳层为无定形SiO2。考察催化剂加入的先后和微乳液R值(R=n水/n表面活性剂)对Ag@SiO2核壳纳米粒子形成的影响。用TEM、UV-Vis、XRD对纳米粒子的形貌及性质进行表征。结果表明:催化剂若先于TEOS加入,易得到Ag@SiO2核壳纳米粒子,随着R值的增加,Ag核的粒径变大,纳米粒子逐渐由单核变成多核。催化剂若后于TEOS加入,则形成负载型Ag/SiO2复合物。Ag核被SiO2壳包覆后的等离子共振吸收峰发生了微弱红移。而当壳厚80nm时,由于SiO2的散射作用,吸收峰会发生蓝移。     

医药剂型在农药中的应用及发展趋向

医药剂型与农药剂犁有许多相通的地方,许多医药剂型已经渗入到农药领域并得到了成功的应用.综述了新剂型及新技术在医药和农药中的应用情况及发展趋向,主要介绍了医药缓控释制剂、片剂、水乳剂、微乳剂以及混悬剂(悬浮剂)在农药中的应用,并对医药新制剂中的分散片、速溶片及渗透泵片在农药领域的应用做了展望,同时指出需审慎对待微乳剂等农药纳米制剂的研发和审批.     

Formulation for chemical EOR: Development and evaluation of an ASP formulation In customer field conditions

Alkali surfactant polymer (ASP) flooding is an enhanced oil recovery (EOR) technology with an impressive potential for increasing incremental oil production from conventional hydrocarbon bearing reservoirs. A challenge to ASP application is the complexity of determining an effective formulation, typically requiring extensive laboratory screening of nearly countless combinations of surfactants and cosolvents. This paper focuses on demonstrating the utility of the hydrophilic–lipophilic deviation (HLD) concept for EOR application to simplify surfactant formulation workstreams seeking an economically viable ASP formulation for field application. In describing work performed for EOR application of ASP under customer conditions using crude oil, the discussion covers the initial evaluation of the promising surfactant formulation (interfacial tension and solubility), the improvement upon the formulation via HLD principles, and the evaluation of the improved surfactant formulation (coreflood studies). The final ASP formulation identified consisted of a 9 to 1 mixture of alkyl propoxy sulfate sodium salt (APS) to alkyl ethoxy sulfate sodium salt (AES) totaling 2000 ppm active surfactant content, 2.0 wt% Na₂CO₃, and 3000 ppm polyacrylamide polymer (all commercially available products). This formulation had ultra-low interfacial tension and favorable mixing behavior under reservoir conditions. In coreflood studies, the final formulation reproducibly achieved cumulative oil recovery of 96.4%–98.5% of original oil in place with only 0.3 PV of ASP injection with a chase alkali polymer injection.