Improved analytical prediction of facilitation factors in facilitated transport

An improved analytical solution for the facilitation factor in facilitated transport that covers a wide range from diffusion-limited to reaction-limited mass transport has been developed. This solution is attained after assuming a small non-zero solute concentration at the membrane exit. Based on previous analysis a graph that provides a reasonable downstream solute concentration was extracted. The exit solute concentration was found to be dependent on both the mobility ratio, , and the inverse Damkohler number, ε. The quick and reasonable results in this work can be used for design and scale-up purposes.     

Facilitated Transport of Carbohydrates, Catecholamines, and Amino Acids Through Liquid and Plasticized Organic Membranes

A number of methods are described to facilitate the transport of monosaccharides, catecholamines, and amino acids through bulk liquid membranes, supported liquid membranes and plasticized cellulose triacetate membranes. Transport is mediated by carrier compounds, such as boronic acids, quaternary ammonium salts and crown ethers, that are dissolved within the lipophilic membranes. Two types of transport mechanisms are described, carrier diffusion and fixed-site jumping.     

A Study of the Permeation of Gold(III) Through Cyanex471x Solid Supported Liquid Membranes (SSLM)

Abstract

A solid supported liquid membrane for the selective removal of Au(III) from chloride solutions has been developed by using Triisobutiphosphine sulfide (Cyanex 471x) In cumene as organic carrier. The membrane system is shown to be effective between chloride solutions ([Cl^?]= 1.0 M) containing traces of Au(III) and SCN^? 0.1 M solutions. Different kinds of at membrane supports have been studied. The results, expressed in terms of membrane permeability, show significant differences between the different supports employed, the polypropylene supports, being the most efficient.     

π-complexes of polystyrene with silver salts and their use as facilitated olefin transport membranes

π-Complexes of silver salts with polystyrene (PS) were prepared and tested in the separation of propylene/propane mixtures. After the incorporation of silver ions into the PS matrix, both the pure propylene gas permeance of the membrane and its olefin selectivity with respect to the propylene/propane mixtures were remarkably higher than those of the pure PS membrane, demonstrating facilitated propylene transport through the solid-state membrane. The remarkable separation performance of the PS/silver salt membranes was attributable to the unusually high solubility of the silver salts in the PS matrix, which was possibly due to the formation of π-complexes between the silver ion and aromatic CC bond of PS. The coordination properties and dissolution behavior of the silver salts in PS were investigated with Fourier transform infrared, Fourier transform Raman, and X-ray photoelectron spectroscopy. The values for the intersegmental d-spacing, determined by wide-angle X-ray scattering, also showed that significant transient crosslinks arose between the PS chains when the silver salts were added to the PS matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2263–2269, 2004     

A re-appraisal of modelling in a liquid surfactant membrane waste water clean up process

Two categories of model have been developed to describe the mass transfer process in emulsion liquid membrane extraction of phenols/amines from waste water. In the first the reaction between the transferred solutes and the trapping agent in the internal phase is assumed to be irreversible while in the second a reversible reaction is involved. Generally the various authors have tested the proposed models against their own experimental data. The present study is an attempt to investigate the efficacy of the reversible reaction model of Bunge and Noble, which is simpler to use and requires input of less parameters to predict the experimental data reported by different authors. It is shown that by introducing a shape factor into the model for the effective diffusivity of solute within the macrodrop, it is possible to use this model to simulate experimental data of other groups reasonably well.     

耦合液膜传输的研究进展

综述了近年来含流动载体的质子、电子及光耦合液膜传输的研究进展及潜在的应用前景。     

HPLC study of the physicochemical characteristics of reverse-osmosis separation on a polyamide membrane material

Summary The fundamental characteristics of reverse osmosis on a polymer membrane have been correlated with HPLC experimental conditions by using the membrane material as a column packing. Twelve formulas were used to calculate the physicochemical characteristics of the reverse-osmosis separation process and it was found that these characteristics can be determined on the basis of retention (t _R, V_R) and partition coefficient (K) of the solute in HPLC. It seems that HPLC is an effective tool for studying the physicochemical nature of reverse-osmosis separations and the characteristics of the polymer membrane.     

Surface physicochemical properties of Pseudomonas fluorescens and impact on adhesion and transport through porous media

The physiological state of an examined Pseudomonas fluorescens strain had a significant impact on its adhesion to glass surfaces and transport through glass-bead columns. In both batch and column studies collision efficiencies, , for exponential phase cells were much larger (≈2–3) than for stationary or decay phase cells (≈0.5–0.7). Centrifugation of exponential phase cells substantially reduced collision efficiencies (≈0.8). Over the examined range (0.02–0.2 M), ionic strength had no impact on cell attachment. The Lewis acid/base (A/B) character of the cell surface varied with physiological states: exponential phase cells exhibited larger values of the electron–donor parameter of the polar surface tension component, γ_S⁻, than stationary or decay phase cells, resulting in larger calculated cell hydrophilicities. A reduction in exponential phase cell ζ-potential was observed upon centrifugation. Traditional Derjaguin–Landau–Verwey–Overbeek (DLVO) interaction energy profiles (between cells and glass surfaces) indicated energy maxima of the order of 90–130kT, and secondary energy minima of less than 10kT. Extended DLVO modeling predicted infinite energy barriers attributable to repulsive A/B interactions, and similar magnitude secondary energy minima. A pseudo-chemical kinetic approach was used to calculate activation energies of adhesion from experimental collision efficiencies. Collision efficiencies were also predicted from a diffusion-governed mass transport model incorporating interacting force fields. Predicted energy barriers underestimated cell collision efficiencies, suggesting that secondary energy minimum interactions governed initial attachment of cells. The partial reversibility of adhesion upon ionic strength reduction supported the secondary minimum interaction hypothesis.     

Proton ionizable crown compounds. 18. Comparison of alkali metal transport in a H2O-CH2Cl2-H2O liquid membrane system by four proton-ionizable macrocycles containing the dialkylhydrogenphosphate moiety

The macrocycle-mediated fluxes of alkali, alkaline earth, and several transition metal cations have been determined and compared in a H₂O-CH₂Cl₂-H₂O liquid membrane system using four water-insoluble macrocycles containing a dialkylhydrogenphosphate moiety. Transport of alkali metal cations by these ligands was greatest from a source phase pH = 12 or above into an acid receiving phase (pH = 1.5). Very low fluxes were observed for the transport of the alkaline earth cations and all transition metal ions studied except Ag⁺ and Pb²⁺ which were transported reasonably well by these new macrocycles.Deceased: September 5, 1987.     

Polymeric complex membranes based on styrene–diene–styrene triblock copolymers for oxygen enrichment

Polymers containing a vinylpyridine, vinylimidazole or oxirane group could be used to immobilize cobalt Schiff bases (CoS), which serve as the oxygen carrier in oxygen enrichment. The graft copolymers, based on styrene–butadiene–styrene (SBS) and styrene–isoprene–styrene grafted with 4-vinylpryidine and 1-vinylimidazole, and epoxidized SBS copolymers were prepared to immobilize CoS. The equilibrium constants between CoS and polymeric materials, the oxygen coordination number and the oxygen binding constants were determined. The thermodynamic parameters of oxygen association/dissociation in various complex membranes were determined. The oxygen permeation behavior through various CoS-containing complex membranes was studied and discussed by the dual-mode facilitated transport theory. The permeation properties of oxygen and nitrogen at low pressure were also investigated.     

Effect of the polymer matrix on the formation of silver nanoparticles in polymer–silver salt complex membranes

When polymer–silver salt complex membranes were exposed to UV irradiation, the separation performances of both the permeance and selectivity for propylene–propane decreased, which was primarily attributed to the reduction of the silver ions in the membranes to silver nanoparticles. Here, the effect of the polymer matrix on the formation of silver nanoparticles in the polymer–silver salt complex membranes was investigated. This effect was assessed for the complexes of two kinds of silver salts (AgBF₄ and AgCF₃SO₃) with several polymeric ligands containing three different carbonyl groups, including poly(vinyl pyrrolidone) (PVP) with an amide group, poly(vinyl methyl ketone) (PVMK) with a ketone group, and poly(methyl methacrylate) (PMMA) with an ester group. UV–vis spectra and transmission electron microscopy (TEM) images clearly indicated that the reduction rate of the silver ions has the following order in the various polymer matrices: PVP > PVMK > PMMA, whereas the size and the distribution of the nanoparticles exhibited the reverse order. The tendency to form silver nanoparticles was explained in terms of the differences between the comparative strengths of the interactions of the silver ions with the different carbonyl oxygens in the matrices, as well as that of the silver ions with counteranions, which was characterized by X‐ray photoelectron spectroscopy (XPS) and FT‐Raman spectroscopy. It was concluded that when the concentration of free silver ions was low due to weak polymer–silver ion and strong silver ion–anion interactions, as found with PMMA, the reduction rate of silver ions to silver nanoparticles was slow. Therefore, the PMMA–silver complex membranes were less sensitive to decreases in separation performance upon UV irradiation than compared to the PVP membranes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1168–1178, 2006     

Kinetics of Ag+ contained polymeric complex membranes for facilitated olefin transport

The reactions of silver ion complexes with polyethylene-graft-poly(acrylic acid) (PE-g-AA) and the olefin reversible coordinates with the PE-g-AA–Ag⁺ complex membranes were studied. Infrared and nuclear magnetic resonance spectra confirmed the complex formation between the carboxylic acid of the PE-g-AA and the Ag⁺ ion. Also, the Ag⁺ ion in PE-g-AA-Ag⁺ membrane was assumed to be a fixed carrier that adsorbs and transports olefin, thereby causing a selective olefin/paraffin separation. A theoretical model of the PE-g-AA-Ag⁺ (olefin) complex was proposed. The coordination number of Ag⁺ ion binding to the carboxylic acid of PE-g-AA is about 1.6 in glycerol solution. The coordination number of olefin binding to the Ag⁺ in the PE-g-AA–Ag⁺ complex membrane is 1. Moreover, the kinetics of olefin binding to the PE-g-AA–Ag⁺ complex membranes were studied. The equilibrium, association, and dissociation constants were also presented. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 909–917, 1997     

Facilitated transport of molecular oxygen in cobaltporphyrin/poly(1-trimethylsilyl-1-propyne) membrane

The combination membrane of poly(1-trimethylsilyl-1-propyne) with enormously high permeability and poly(vinylimidazole)-bound porphinatocobalt with selective oxygenbinding ability was prepared. Oxygen transport through the membrane was facilitated in terms of oxygen transport via the latter domain as a fixed oxygen-carrier, and this oxygen permeability maintained for a month.     

Structure and coordination properties of facilitated olefin transport membranes consisting of crosslinked poly(vinyl alcohol) and silver hexafluoroantimonate

The high selectivity of solid‐state crosslinked poly(vinyl alcohol) (CPVA) membranes containing silver hexafluoroantimonate (AgSbF₆), with respect to olefin/paraffin mixtures, was previously reported. The structure and coordination properties of CPVA/AgSbF₆ complexes were investigated in this study with wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), X‐ray photoelectron spectroscopy (XPS), and theoretical ab initio calculations, and they were compared with those of poly(vinyl alcohol) (PVA)/AgSbF₆ complexes. Contrary to expectations, the measurements of the intersegmental d‐spacings and glass‐transition temperatures indicated that the chain mobility in the PVA/AgSbF₆ membranes was lower than that in the CPVA/AgSbF₆ membranes. The different extents of transient crosslinking in the two systems were attributed mostly to their different coordination structures; silver ions in PVA/AgSbF₆ were coordinated with hydroxyl oxygens located near the polymer main chains, whereas those in CPVA/AgSbF₆ were coordinated with aldehyde oxygens located far from the main chains. According to WAXS spectra, AgSbF₆ was completely dissolved in both PVA and CPVA, and this disrupted the crystallinity of the polymers. However, our DSC study showed that the silver ions dissolved in both polymer matrices recrystallized into silver oxide at elevated temperatures. The binding energy of Ag3d_5/2, as determined from XPS spectra, shifted to lower values with the addition of increasing amounts of the polymer matrix, indicating the increasing coordination of silver ions with polymer chains. The presence of various oxygen species with and without coordination to silver ions was confirmed from O1s XPS spectra of CPVA membranes containing silver ions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 621–628, 2004     

Synthesis of HgSe quantum dots through templates controlling and gas–liquid transport with emulsion liquid membrane system

A new synthetic method of HgSe quantum dots has been investigated through template controlling with emulsion liquid membrane system. The membrane system consists of kerosene as solvent, span80 as surfactant, N7301 as carrier, and HgCl₂ solution as internal-aqueous phase containing template of different concentrations, and uses gas–liquid transport on interface of external phase. Its optimum condition is as follows, kerosene:span80:N7301 = 74:6:20, Roi=1:1. While using inorganic KI as the template and adjusting HgCl₂ concentrations (keeping KI/HgCl₂ = 10), transmission electron microscope shows that HgSe quantum dots of different sizes can be obtained respectively, X-ray diffraction (XRD) reveals that the products have a cubic structure. The research has shown that quantum confinement effect of these HgSe quantum dots (2–3 nm) have inverted band structure (HgSe bulk) increase their effective bandgap giving rise to infrared (IR) luminescence. Its forming process is also inferred.     

A study of the transport of ions against their concentration gradient across ion-exchange membranes using the network method

The network method has been used to analyze the conditions that favour the uphill transport across ion-exchange membranes. A model for the Nernst-Planck-Poisson equations describing the ionic transport in such system is proposed, including the Donnan equilibrium relations at the membrane/solution interfaces. With this model and the electric circuit simulation program PSPICE, the transient response of the system under open circuit conditions (I=0) and the response of the system subject to an applied potential difference are simulated. The ionic concentrations and electric potential profiles, as well as the electric current density, the ionic fluxes and the charge density, have been obtained as a function of time.     

A parametric study of electron energy distribution functions and rate and transport coefficients in nonequilibrium helium plasmas

Electron energy distribution functions in helium plasmas have been calculated by solving the Boltzmann equation at given values of reduced electric field, in the presence of superelastic and electron-electron collisions. Analytical expressions have been found connecting macroscopic coefficients to reduced electric field E/N, relative metastable concentration [He(2³S)]/N, and degree of ionization n_e/N.     

Interfacial constraints on water and proton transport across nafion membranes

Water and proton transport across a Nafion membrane are measured as functions of water activity and applied electric potential with a polymer electrolyte hydrogen pump. Water and proton transport across the membrane must match water and proton transport entering and leaving the electrode/membrane/vapor three phase interfaces at the anode and cathode. At low applied electric potential proton and water fluxes are correlated. At moderate to high applied electric potential the proton current is constant, independent of applied electric potential, while the water transport increases with increasing electric potential. At high applied electric potential water and proton transport become uncoupled at the membrane interfaces; water is transported across the membrane/vapor interface and protons are transported across the membrane/electrode interface. The applied electric potential drives electro‐osmosis to redistribute the water in the membrane. Water redistribution is limited by the interfacial transport of water across the membrane/vapor interface. © 2015 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2015 , 53, 1580–1589     

Simulations of the active transport of a neutral solute based on a kinase-channel-phosphatase topology

Simulations of coupled interactions involving two opposite enzymatic reactions, solute diffusions, and electrostatic interactions between membrane charges and charged solutes were conducted under a fixed kinase-channel-phosphatase (KCP) topology oriented from the outside to the inside of a porous membrane structure. Depending on the kinase and phosphatase locations, we recently demonstrated that an active transport of a phosphorylated substrate may occur via the opposite topology, that is, a PCK topology. The present analysis demonstrates that, under a KCP membrane topology, which also behaves as a specific ATP-dependent transporter, the active transport of a neutral substrate may occur. This analogous active transport appears to be dependent on the phosphatase location and on the membrane surface potentials. A broad analysis of the role played by the main parameters taken into account in the model was conducted in order to define precisely the physico-chemical conditions and the membrane topology needed for the highest active transports within the shortest time.     

The transport of amino acids by 18-crown-6 through liquid membranes

The possibility of separating in cationic form some -amino acids (L-Methionine, L-Leucine, L-Isoleucine, L-Valine, L-Phenylalanine, L--Alanine and L-Cysteine) from mixtures in the presence of picrate anion has been investigated by means of active transport assisted by a pH gradient through liquid membranes. 18-Crown-6 in 1,2-dichloroethane has been used as a selective carrier. The effect of stirring rates at different volumes of the membrane, suggests a diffusional rate-limiting process of the amino acid transport.