谷氨酸在Span80-AOT-APS体系中的迁移行为

报道了谷氨酸在乳状液膜体系中的迁移行为,采用失水山梨醇单油酸酯(span80)-乙基己基琥珀酸酯磺酸钠(AOT)为表面活性剂,对氨基苯磺酸(APS)为载体,煤油为膜溶剂,氯化钾为内相试剂.讨论了制乳时间和乳液与外相混合时间、表面活性剂和流动载体浓度、内相试剂浓度、水乳比和油内比对分离效果的影响.确定了最佳分离条件为制乳...     

Spontaneous emulsification at oil–water interface by tetraalkylammonium chloride

Water droplets were formed spontaneously at the interface of the 2-nitrophenyloctyl ether and aqueous phases on the oil phase side when the oil contained tetraalkylammonium chloride without surfactants. The droplets, less than some micrometers in diameter, gathered at the interface. The number density of the droplets was proportional to the concentration of tetraethylammonium chloride, and hence this salt should be responsible for the formation of the droplets as a surfactant. When positive voltage was applied to the aqueous phase against the oil, the droplets departed from the interface toward the oil bulk. The droplets should be negatively charged by chloride. The adsorption model of the salt was suggested, in which chloride is immobilized at the interface on the aqueous side electrostatically with tetraethylammonium ion on the oil side.     

Anion influence on extraction and transport of amino acid methyl esters by functionalised calix[4]arene

The liquid–liquid extraction of a series of amino acid methyl esters has been carried out with functionalised calix[4]arene (5,11,17,23-tetrakis(N-methylpiperazino)-25,26,27,28-tetrahydroxycalix[4]arene) from an aqueous phase into a chloroform phase as ion pairs in the presence of picrate ion or tropaeolin 00 as counter ion in order to study the molecular recognition properties of this receptor. The active transport assisted by pH gradient of amino acids as ion pairs through liquid membrane employing the functionalised calix[4]arene as carrier has been investigated. The results showed that the receptor exhibits good extractability towards amino acids and it can also act as carrier through liquid membrane aiming to the separation of amino acids. It was highlighted that the anion nature used as counter ion, the structure of calix[4]arene, and the structure of amino acids are responsible for the experimental results obtained. High yields in both amino acids extraction and transport were obtained for picrate ion used as counter ion.     

FT-IR and 2D-IR spectroscopic studies on the effect of ions on the phase separation behavior of PVME aqueous solution.

Thermosensitive phase transition behavior of poly(vinyl methyl ether) (PVME) in an aqueous solution and the effect of inorganic ions on the coil-globule transition have been investigated by Fourier transform infrared (FT-IR) spectroscopy with attenuated total reflection (ATR) accessory. ATR-IR spectra of PVME aqueous solution indicate that in water-PVME-inorganic salts system, the phase separation temperature of PVME aqueous solution decreased with the increase of ion concentration and the increase of anion electronegativity. Meanwhile, two-dimensional infrared (2D-IR) measurements have been made to clarify the microcosmic conformational changes of PVME during the coil-globule transition. Results show that the conformation changes of main chains occur earlier than those of ether groups during heating. Furthermore, the 2D correlation spectroscopy of PVME aqueous solution during heating and the increase of concentration of potassium chloride have been studied. The features of 2D-IR spectra during heating did not change compared to the features of PVME aqueous solution during the increase of concentration of potassium chloride. This result implies that, although the addition of inorganic ions shifts the phase separation temperature, it does not alter the internal mechanism of the coil-globule transition of PVME.     

Highly selective transport of silver ion through a supported liquid membrane using calix[4]pyrroles as suitable ion carriers

Facilitated transport of silver ion across a supported liquid membrane (SLM) by calix[4]pyrroles, as selective ion carriers, dissolved in kerosene has been investigated. The influences of fundamental parameters affecting the transport of silver ion including ion carrier concentration in the membrane phase, thiosulfate concentration in strip phase, picric acid concentration in the feed phase, stirring speed of aqueous phases, type of membrane solvent and time of transport have been studied. In the presence of thiosulfate as a suitable metal ion acceptor in the strip phase and picrate ion as ion pairing agent in the source phase, transport of silver occurs almost quantitatively after 75 min. The selectivity and efficiency of silver transport from aqueous solution containing Cu²⁺, Mg²⁺, Ni²⁺, Ca²⁺, Zn²⁺, Pb²⁺, Co²⁺, Al³⁺, Hg²⁺, Cd²⁺, Fe³⁺, Fe²⁺ and Cr³⁺ were investigated.     

Extraction of Cr (VI) by pickering emulsion liquid membrane using amphiphilic silica nanowires (ASNWs) as a surfactant

Pickering emulsion is the replacement of surfactants with solid, often nano-sized particles. The particle-stabilized emulsions have good thermodynamic and kinetic stability. Pickering emulsion liquid membrane (PELM) was prepared using mahua oil as a diluent, aliquat 336 (Trioctyl methylammonium chloride) as a carrier and amphiphilic silica nanowires (ASNWs) (10–40?ml ethanol addition) as a surfactant. Sodium hydroxide (NaOH) was used as stripping phase in the concentration range from 0.1 to 0.5?M for the extraction of hexavalent chromium [Cr (VI)] from aqueous solution. The variety of edible and non-edible oils was investigated for the stability of water in oil emulsion. Factors that influence silica-stabilized Pickering emulsions are pH, agitation speed, stripping phase concentration, the volume ratio of membrane to stripping phase (M/S), initial feed concentration, treat ratio(feed to emulsion volume ratio) and surfactant concentration for better PELM stability. And also, the extraction efficiency of Cr (VI) was investigated using aliquat as a carrier. The physicochemical properties of ASNWs were studied using Scanning Electron Microscopy (SEM), Fourier Transforms Infrared Spectroscopy (FTIR) and Dynamic Light Scattering (DLS) techniques. At an optimum condition, 99.69% of Cr (VI) removal from aqueous solution was obtained.     

Mechanism of a four-phase liquid membrane oscillator containing hexadecyltrimethylammonium bromide

The oscillatory behavior of a nitromethane based liquid membrane oscillator was investigated to contribute to the oscillation mechanism at the molecular level. At the beginning the system contains three phases: the aqueous donor phase in which the cationic surfactant, hexadecyltrimethylammonium bromide and ethanol are present and the aqueous acceptor phase made up by sucrose solution separated by the liquid membrane containing a constant amount of picric acid. During experiment a new phase x is created between the liquid membrane and acceptor phase. It was established that the oscillations take place at the membrane/phase x and the phase x/acceptor phase interfaces. Five basic regions can be distinguished in the oscillation pattern. The molecular events provoking the oscillations of electric potential difference between the two aqueous phases involve essentially the diffusion of hexadecyltrimethylammonium bromide and ion pairs formed by the cation of the surfactant and the picrate anion to the vicinity of the membrane/phase x interface, sudden adsorption of these ion pairs at this interface in noncatalytic and autocatalytic steps, desorption of ion pairs from the membrane/phase x interface into phase x, diffusion of ion pairs to the vicinity of phase x/acceptor phase interface, and sudden adsorption at this interface followed by desorption to the aqueous acceptor phase. It is shown by numerical simulations that the proposed mechanism may account for the observed oscillations and for the species distribution throughout the system as found experimentally. This four-phase system behaves like two coupled oscillators.     

Thermally stable,highly fluorinated stationary phases for gas chromatography

The chromatographic properties of three highly fluorinated stationary phases namely Fomblin YR [a poly(perfluoroalkyl) ether], PPF-20 [a poly(perfluorphenylene) ether], and Fluorad FC-430 [a fluoroalkyl ester], are compared with those of conventional phases. The importance of phase structure, coating solvent, and surface chemistry of the support for the preparation of efficient and stable column packings is outlined. The retention of solutes of different structures is shown to occur by a combination of gas—liquid partitioning and interfacial adsorption. The relative importance of partitioning compared to adsorption is influence by the degree of fluorination and the measurement temperature. From accurately determined gas—liquid partition coefficients, corrected McReynolds phase constants and partial molar free energies of solution for a methylene group (ΔG) were determined for the highly fluorinated phases. In the case of Fomblin YR, the very low value for ΔG(CH₂) compared to conventional phases provides a quantitative indication of the weak intermolecular forces operating in the chromatographic system. Higher values for PPF-20 indicate stronger dispersive interactions for the perfluroaromatic phase compared to the perfluoroalkyl phases.     

Recovery of zinc from chloride media by batch pertraction in a rotating film contactor

A liquid membrane (pertraction) process of zinc recovery from acidic chloride solutions was studied applying a pertraction in a rotating film contactor (RFC). Tri-n-octylamine (TOA or R₃N) dissolved in n-octane was used as a carrier. The influence of the main process parameters, such as disc rotation velocity, hydrochloric acid concentration in the aqueous phases and carrier concentration in the membrane was investigated. Assuming the existence of two thin reaction layers in the feed and stripping solutions, adjacent to both water–oil interfaces, a mathematical model was developed to describe the zinc transport. On the basis of the experimental data obtained under various conditions and the model proposed, it was found that the extraction step is controlled mainly by the mass transfer resistance, whereas the stripping rate of zinc is controlled predominantly by the rate of zinc–carrier complex decomposition in the stripping side reaction layer.     

Liquid–liquid equilibria of water/1-propanol/methyl ethyl ketone/potassium chloride

The liquid–liquid equilibrium of water/1-propanol/methyl ethyl ketone (MEK) at 25°C was significantly modified by the presence of dissolved potassium chloride. Water is salted out of the organic phase while MEK is more preferentially salted out of the aqueous phase than 1-propanol. These results in considerable enlargement of the two-phase region and enhancement of the extractive efficiency of MEK for the separation of 1-propanol from its aqueous mixture. Good correlation of the liquid–liquid equilibria (LLE) of the system in the presence of potassium chloride up to saturation was obtained with Tan’s modified NRTL phase model for multicomponent solute–solvent mixtures with the solute–solvent interaction parameters expressed as a third-order polynomial function in salt concentration. Similar to the observation reported for vapour–liquid equilibrium (VLE) of solvent–solute mixtures, salting-in and salting-out of the solvent components from the respective phases can be predicted according to the relative solute–solvent interaction parameters of the solvent components in the two phases.     

Extraction of glyphosate by a supported liquid membrane technique

The possible application of the supported liquid membrane (SLM) technique for the extraction of glyphosate is presented. For the extraction of this compound the SLM system has been applied with utilisation of Aliquat 336 as a cationic carrier incorporated into the membrane phase. The extraction efficiency of glyphosate [N-(phosphonomethyl)glycine] is dependent on the donor phase pH, carrier concentration in the organic phase and NaCl concentration in the acceptor phase. The optimal extraction conditions are: donor phase pH>11, acceptor phase of 2 M NaCl solution and the organic phase composed of 20% (w/w) Aliquot 336 solution in di-hexyl ether. Counter-coupled transport of chloride anions from the acceptor phase to the donor phase is a driving force of the mass transfer in this system.     

Micro-scale membrane extraction of glyphosate and aminomethylphosphonic acid in water followed by high-performance liquid chromatography and post-column derivatization with fluorescence detector

A carrier-mediated supported liquid membrane micro-extraction using single hollow fiber membrane suitable for the determination of the herbicide glyphosate and its main metabolite aminomethylphosphonic acid in water is reported. A solution of 0.20 M Aliquat-336, a cationic carrier, in di-n-hexyl ether was selected as the supported liquid. A 20 microL of 1.0 M potassium chloride as the acceptor phase was filled in the membrane lumen. The membrane was immersed in a 20 mL of pH 9.0 sample solution. After 60-min extraction, the acceptor phase was analyzed by high-performance liquid chromatography with post-column derivatization. The enrichment factors were found to be 853 and 136 for glyphosate and aminomethylphosphonic acid, respectively. The method detection limits are 0.22 microg/L for glyphosate and 3.40 microg/L for aminomethylphosphonic acid. The procedure was validated and showed good accuracy and precision over a large linear dynamic range. The validated method was tested for the analysis of both analytes in spiked groundwater with good success.     

Polysalt complexes of poly(vinylbenzo-18-crown-6) and of poly(crown acrylate)s with polyanions

Macrocyclic polyether or crown ether ester derivatives of acrylic and methacrylic acid were synthesized and polymerized. The cation binding properties of the polymers determined by extraction of picrate salts were similar to those obtained for poly(crown ether)s derived from styrene. In the presence of a crown-complexable cation both polymers form insoluble polysalt complexes with sodium carboxymethylcellulose, potassium poly(styrene sulfonate), and potassium polyacrylate. The extent of precipitation depends on the type and concentration of cation as well as on the ratio polyanion to poly(crown ether). The precipitate appears to have an equal number of positive and negative charges. An insoluble hydrogen-bonded complex is formed in the absence of salt when poly(vinylbenzo-18-crown-6) and poly(acrylic acid) are mixed in 0.01M HCl. Organic solutes bound to the poly(crown ether)s, which occur in an aqueous mixture of poly(vinylbenzo-18-crown-6) and picrate anions, are precipitated with the poly(crown ether) when the polysalt complex is formed.     

Transport of calcium and potassium ions in opposite directions in a liquid membrane system

A new type of 18-crown-6 derivative having two carboxylic acids on the side arms transported calcium and potassium ions in opposite directions across a dichloromethane membrane by pH control. Calcium and potassium ions were concentrated in the acidic and the basic phases, respectively. The presence of picrate ion in the acidic phase plays an important role in the transport of potassium ion from the acidic to the basic phase.     

Transport of Ca2+, Sr2+, Ba2+, Na+, K+ and Cs+ through hollow fiber supported liquid membrane

The transport of metal ions (Ca²⁺, Sr²⁺, Ba²⁺, Na⁺, K⁺, Cs⁺) through hollow fiber supported dichlorobenzene liquid membrane has been studied. The transport of cations using 8-crown-6 ether as a carrier and picrate as co-counter ion as well as a pertraction device and capillary isotachophoresis (ITP) measurement of the cation concentration is described.     

Swelling equilibrium of poly(acrylamide) gels in aqueous salt and polymer solutions

The influence of some single salts (NaCl, KCl, Na₂HPO₄ and K₂HPO₄) and poly(ethylene glycol) (PEG) on the swelling of aqueous poly(arcylamide)-gels was studied at 25°C in more than 600 experiments. The chlorides and phosphates cause a different behavior at high salt concentrations: The polyacrylamide gels swell in aqueous solutions of sodium and potassium chloride whereas they shrink when chloride ions are substituted by hydrogen phosphate ions. These differences are due to differences in the interactions of chloride and hydrogen phosphate ions with the network groups. In aqueous solutions of poly(ethylene glycol) the gels shrink continuously with increasing polymer concentration. At constant PEG mass fraction in the liquid phase, the swelling of the gel decreases with increasing molecular weight of PEG. The experimental results (degree of swelling, partitioning of solutes to the coexisting phases) are correlated by combining a model for the Gibbs excess energy for aqueous systems of polymers and electrolytes with a modification of the phantom-network theory. The correlation gives a good agreement with the experimental data for the degree of swelling, whereas in most cases, there is only a qualitative agreement for the partitioning of the solutes.     

Evaluation of selectivity-determining factors for membrane electrodes based on naphtho-15-crown-5 by liquid-liquid extraction

Liquid-liquid extractions of sodium and potassium picrates with naphtho-15-crown-5 (N15C5) into 1,2-dichloroethane are studied, in order to clarify the factors governing the high potassium ion selectivity of the N15C5-based membrane electrode. The distribution coefficient of N15C5 between water and 1,2-dichloroethane was 1800 at 15°C. The formation constants of the complexes of N15C5 with the sodium ion and the potassium ion in the aqueous phase were less than unity and there was no remarkable difference between their values. Potassium picrate was mainly extracted into 1,2-dichloroethane by forming the 2:1 N15C5-potassium complex, while sodium picrate was extracted by forming the 1:1 complex. The extraction constants for sodium picrate and potassium picrate were 10^3.86 and 10^7.61, respectively, The high potassium selectivity is concluded to be due to the high extractability of the 2:1 potassium complex.     

Selective transport of silver ion through a supported liquid membrane using hexathia-18-crown-6 as carrier.

A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated.     

The preparation and properties of neutral diamide ionophores for group IIA metal cations-II

The elaboration of a series of neutral ligands featuring vicinal ether and N,N-dialkylacetamido groups is described. Several of these ligands were prev with K_app=10³-10⁵ in methanol of the Group IIA cations for which they are sensitive. Binding constants by the Scatchard method are reported for a number of ligands mainly with Ca, Sr, Mn and Ba. The ligands in methylene chloride solution extract these cations via their picrate salts from water. The electrochemical K_ij^pot (selectivity) values for some of the ligands when they are incorporated into liquid membrane electrodes and tested with various cations as determined by Simon . (ETH Zurich) are reported. Selectivity ratios of over 100:1 for Na vs Ca were found for several piperidenyl amides of 1,2-phenylenedioxydiacetic acid. Incorporation of N-methylamino instead of ether oxygen groups into the basic structure gives a stronger cation binder which is still selective for Group IIA vs Group IA cations but with binding capacity for transition metal cations also. Limitations of the Scatchard plots for these ligands and the non-correspondance of electrochemical selectivities with the ordering of binding of cations in single liquid phase are discussed.     

Multi-stage premix membrane emulsification for preparation of agarose microbeads with uniform size

Uniform-sized agarose beads with diameters less than 10 μm and agarose content as high as 14 wt% were prepared by premix membrane emulsification. Agarose aqueous solution was used as the water phase. A mixture of liquid paraffin and petroleum ether containing hexaglycerin penta ester (PO-500) was used as the oil phase. The water phase was mixed with the oil phase at 60 °C and a coarse W/O emulsion was produced in a homogenizer. Then, the coarse emulsion was extruded through a hydrophobic membrane under high pressure to form an emulsion, which was slowly cooled under gentle agitation to form gel beads. The effects of preparation conditions on emulsification results were investigated and it showed that the pressure, number of passes, petroleum ether/liquid paraffin (v/v) in the oil phase, the concentration of PO-500 and concentration of agarose in the water phase, all affected the size and uniformity; coarse emulsion did not affect the emulsification results. The coefficient variation (C.V.) of agarose beads under optimal preparation conditions was 9.8%. This method realized microbeads with both uniform sizes and high agarose contents that are difficult to be prepared by conventional emulsion methods.