Studies with model membranes: Part IX. Evaluation of the thermodynamic effective fixed charge density and permselectivity of parchment supported cobalt tungstate and mercuric chromate membranes

Thermodynamic effective fixed charge densities of cobalt tungstate and mercuric chromate parchment supported membranes were evaluated by a number of methods particularly those of Teorell-Meyer-Sievers [19]. Altug and Hair [23] and the most recent one of Kobatake et al. [24, 27] based on the thermodynamics of irreversible processes. The value of the permselectivity was also obtained for the two membranes based on Kobatake et al.'s procedure. Kobatake et al.' equation was used under two limiting conditions of concentration of electrolyte solution, namely (1) in the concentrated range, and (2) in the dilute range. The charge densities obtained under these conditions namely θ_c and θ_d were found to differ (θ_c=1/2θ_d), but it was interesting to note that θ_c values were more closer to those of the TMS values. The theoretical predictions for membrane potential using Kobatake et al.'s equation are borne out quite satisfactorily by our experimental results for both membranes.     

Studies with model membranes. X. Evaluation of the thermodynamically effective fixed charge density and permselectivity of mercuric and cupric iodide parchment-supported membranes

Thermodynamically effective fixed charge densities of mercuric and cupric iodide parchment supported membranes were estimated by methods of Teorell, Meyer, and Sievers; Altug and Hair; and the most recent one of Kobatake and co-workers based on the thermodynamics of irreversible processes. The two limiting forms of Kobatake's equation for dilute and concentrated ranges gave identical values of charge densities. It is interesting to note that these two values of limiting cases are closer to the Teorell-Meyer-Sievers and Altug-Hair values. The theoretical predictions for membrane potential by the Kobatake equation were borne out quite satisfactorily by experimental results obtained with both the membranes.     

Studies of asymmetry of diffusion permeability of nanocomposite ion-exchange membranes: Model of charge density of fixed groups linear by membrane thickness

A new model of a fine-porous membrane with a linear distribution of charges of its fixed groups along its depth is suggested in the work to explain the effect of asymmetry of diffusion permeability of perfluorinated MF-4SK membranes surface-modified by polyaniline. The model allowed better describing the experimental data for the synthesized nanocomposite MF-4SK/PANI membranes than the earlier developed model of a bilayer membrane with constant fixed charge densities in layers, which points to its feasilibity.     

氢氧化铝镁钠米颗粒的零电荷点及电荷密度研究

探讨了电位滴定(PT)法测定的零电荷点的物理意义, 认为是零净电荷点(ZPNC)。并对零净电荷点pH(pHZPNC), 零可变电荷点pH(pHZPVC), 永久电荷密度(σP), 可变电荷密度(σV)和净电荷密度(σT)之间的关系进行了理论分析。用PT法测定了氢氧化铝镁纳米颗粒的pHZPNC和σP, 探讨了电解质浓度和pH对各电化学性质的影响规律。另外, 还考察了CO3^2^-对PT法测定结果的影响。     

Studies on the ion-exchange behaviour of chromium ferrocyanide

The sorption of univalent, bivalent and trivalent ions has been studied on chromium ferrocyanide gel. The studies reveal a high sorption capacity for Cs⁺, Tl⁺, Ag⁺, Cu²⁺, Zn²⁺, Cd²⁺, Fe³⁺ and Th⁴⁺. The sorption of monovalent cations show purely ion-exchange mechanism while the uptake of bivalent and trivalent cations is non-equivalent in nature. Single elution of Rb⁺, Cs⁺ and Tl⁺ has been performed from the columns of this exchanger and the recovery is almost complete in all the cases. Cu²⁺ and Ag⁺ get completely adsorbed on the gel column and their elution is not possible probably due to the formation of some new solid phases. Depending on the K_d values of the metal ions, a large number of separations of radiochemical as well as analytical importance can be performed on the columns of this exchanger material.     

Asymmetry of current-voltage characteristics of ion-exchange membranes: Model of charge density of fixed groups linear by membrane thickness

The model of a finely porous membrane with a linear distribution of charges of its fixed groups along its depth is used in the work to explain the phenomenon of asymmetry of current-voltage characteristics of perfluorinated MF-4SK membranes surface–modified by polyaniline or halloysite nanotubes. A new exact analytical method of solution of a system of transport equations is suggested that is based on the assumption of the monotonous behavior of the electric potential inside the membrane and allows finding current- voltage characteristics (CVCs) of the membrane using a system of two implicit algebraic equations. Algebraic equations for limiting currents are obtained for the first time for different orientations of the anisotropic membrane in an electrodyalisis cell and existence of two inflection points in CVCs is explained when its less charge side is oriented towards the anode.     

Effect of surface-active substances on the surface charge density of purple membrane fragments

The surface charge density of purple membrane fragments and its alteration upon treatment of purple membranes with several surface-active substances [sodium dodecyl sulphate (SDS), cetylpyridinium chloride (CPC) and 3-[(3-cholamidopropyl) dimethylammonio]-1-propane-sulphonate (CHAPS) were examined by use of 9-amino-acridine fluorescence.The value of the surface charge density of native purple membrane fragments (0.8 electric charges/nm²) obtained by this method is comparable to previously reported values and in agreement with the structural model of the purple membrane.An increase followed by a decrease in the negative surface charge density was observed after treatment of purple membranes with the negatively charged surfactant SDS within the concentration range 0–5 mM, whereas treatment with the positively charged surfactant CPC and zwitterionic derivative of cholic acid (CHAPS) led to a decrease in the surface charge density. The large reduction of the surface charge density after treatment of purple membranes with CHAPS (i.e. partial delipidation of purple membranes) proves the significant contribution of the negative charges of the lipid polar head groups to the negative surface charge of purple membranes.     

Use of chromium ferrocyanide membrane electrode in the potentiometric titration of ferrocyanide with metal ions

Membranes based on the inorganic ion-exchanger chromium ferrocyanide have been prepared, which exhibit linear response to ferrocyanide over the concentration range 10(-1)-10(-4)M. Although the electrode is not very specific for ferrocyanide, it can be used for potentiometric titration of metal ions with ferrocyanide ion or vice versa. Hg(2+), Th(6+), UO(2+)(2), Pb(2+), Cu(2+) and Zn(2+) have been determined in this way.     

Studies with inorganic precipitative membranes: XI. Membrane potential response,characterization and evaluation of effective fixed charge density

Membrane potentials arising across parchment supported nickel and cobalt phosphate membranes when they separete 1:1 electrolyte solutions of concentration c₁ and c₂ such that c₁=10 c₂, have been measured. The membranes in contactwith dilute solutions have been found to carry a negative charge whereas the charge reversal was observed when the membrane was separating concentrated solutions. The membrane potential data have been used according to the procedure prescribed by Teorell-Meyer-Sievers theory (the TMS theory) to derive the value of effective fixed charge density of membranes. The electrical double layer at the membrane-solution interface has been suggested to control the over all rate of diffusion.     

Studies with nickel phosphate membranes: evaluation of charge density and test of recently developed theory of membrane potential

The preparation of polystyrene-based nickel phosphate membrane at different pressures with varying amounts of material has been described. In order to understand the mechanism of transport of ions, membrane potential measurements were carried out using different concentrations of 1:1 electrolyte (KCl, NaCl and LiCl) solutions and also to evaluate various membrane parameters controlling the transport phenomena. Teorell, Meyer and Sievers (TMS) method was used for the estimation of the thermodynamically effective fixed charge density of membranes. The data were then utilized to calculate membrane potential using the extended TMS theory. It was interesting to note that the theoretical predictions were borne out quite satisfactorily with experimental results. scanning electron microscope (SEM) micrographs of the membranes have also been presented.     

Studies on the effect of non-electrolytes on the stability of copper ferrocyanide sol

Summary In general the addition of non-electrolyte to hydrophobic sols results into an irregular change in the stability of the latter, towards electrolyte coagulation. Precipitation concentration of potassium chloride for copper ferrocyanide sol changes in the presence of ethyl alcohol, glycol or glycerol. Ethyl alcohol sensitizes while others stabilise the sol to different extents. In presence of these alcohols, electrolytic coagulation of copper ferrocyanide sol is attended by a decrease in the conductance and hydrogen ion concentration as compared to a pure sol (sol without non-electrolyte).

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Zusammenfassung Im allgemeinen verursacht das Zufügen von Nicht-Elektrolyten zu hydrophoben Solen eine irregul?re ?nderung der Stabilit?t der letzteren hinsichtlich der Elektrolytkoagulation. Die F?llungskonzentration von Kaliumchlorid für Kupfer-Ferrocyanid-Sol ?ndert sich bei Gegenwart von ?thylalkohol, Glykol oder Glycerin. ?thylalkohol sensibilisiert, w?hrend die anderen das Sol in verschiedenem Ausma\ stabilisieren. In Gegenwart dieser Alkohole ist die Elektrolytkoagulation des Kupfer-Ferrocyanid-Sols von einer Abnahme der Leitf?higkeit und der Wasserstoffionenkonzentration, verglichen mit den reinen Solen ohne Nicht-Elektrolyt begleitet.

     

Studies with inorganic precipitate membranes. IV. Evaluation of apparent fixed charge on membranes

Membrane potentials arising across four parchment-supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium when they separate 1:1 electrolyte solutions of concentration C₁ and C₂ such that C₁ = 10C₂, have been measured. The data have been used according to the procedure prescribed by one of the theories of membrane potential due to Teorell and Meyers and Sievers to derive values for the quantity of charge present on the membranes. An alternative procedure employed by Altug and Hair has been considered and found to overestimate the value for the charge on the membranes.     

Control of the fixed charge distribution in an ion-exchange membrane via diffusion and the reaction rate of the monomer

The fixed charge distribution of the ion-exchange membranes was controlled by introducing ion-exchangeable groups onto the glycidyl methacrylate (GMA)-g-polypropylene (PP) membranes. The membranes were prepared by plasma-induced graft polymerization with uniform or nonuniform graft distributions over the cross section. The effects of reaction conditions on the graft distribution in plasma-induced graft polymerization were investigated to obtain the GMA-g-PP membranes with different graft distributions. The examined reaction conditions were plasma power, gas pressure of the plasma, solvent, concentration of the monomer solution, and reaction temperature. The graft distribution of the membranes was directly observed by a microscopic Fourier transform infrared mapping method and field-emission scanning electron microscopy. Also, the graft distribution was correlated with the relative magnitude of the reaction rate to the diffusion rate, which may determine the grafting yield as a function of the distance from the surface. A high rate of diffusion compared to the reaction rate resulted in a more uniform graft distribution. Among the grafting conditions, control of the reaction temperature was found to be the most effective for selectively preparing both uniform and nonuniform graft distribution. Uniform graft distribution was achieved when the reaction was conducted at 1 degrees C because of the relatively rapid diffusion and the slow reaction of the monomer, while nonuniform graft distribution occurred at higher reaction temperatures. Consequently, uniformly and nonuniformly charged cation-exchange membranes were prepared through sulfonation of the corresponding GMA-g-PP membranes at temperatures of 1 and 40 degrees C, respectively.     

Enhanced transfection efficiency of multicomponent lipoplexes in the regime of optimal membrane charge density

Recently, membrane charge density of lipid membranes, sigma M, has been recognized as a universal parameter that controls the transfection efficiency of complexes made of binary cationic liposomes and DNA (binary lipoplexes). Three distinct regimes, most likely related to interactions between complexes and cells, have also been identified. The purpose of this work was to investigate the transfection efficiency behavior of multicomponent lipoplexes in the regime of optimal membrane charge density (1< sigma M < 2 x 10 (-2) e/A (2)) and compare their performance with that of binary lipoplexes usually employed for gene delivery purposes. We found remarkable differences in transfection efficiency due to lipid composition, with maximum in efficiency being obtained when multicomponent lipoplexes were used to transfect NIH 3T3 cells, while binary lipoplexes were definitely less efficient. These findings suggested that multicomponent systems are especially promising lipoplex candidates. With the aim of providing new insights into the mechanism of transfection, we investigated the structural evolution of lipoplexes when interacting with anionic (cellular) lipids by means of synchrotron small-angle X-ray diffraction (SAXD), while the extent of DNA release upon interaction with anionic lipids was measured by electrophoresis on agarose gels. Interestingly, a clear trend was found that the transfection activity increased with the number of lipid components. These results highlight the compositional properties of carrier lipid/cellular lipid mixtures as decisive factors for transfection and suggest a strategy for the rational design of superior cationic lipid carriers.     

Change in permselectivity between sulfate and chloride ions through anion exchange membrane with hydrophilicity of the membrane

The transport number of sulfate ions relative to chloride ions through an anion exchange membrane was measured by electrodialyzing a sodium sulfate and sodium chloride mixed solution containing diethylene glycol after immersing the membrane in diethylene glycol because the membrane had good affinity to ethylene glycol and diethylene glycol. The transport number of sulfate ions relative to chloride ions increased in the presence of diethylene glycol in the membrane. This is due to the increase in the uptake of sulfate ions in the membrane compared with chloride ions, not to the change in a ratio of mobilities of both anions.     

Electrical potentials of two identical particles with fixed surface charge density in a salt-free medium

The electrical potentials of two identical planar, cylindrical, and spherical particles immersed in a salt-free dispersion are solved analytically by a perturbation approach for the case of constant surface charge density. The system under consideration simulates, for example, micelles, where the ionic species in the liquid phase come mainly from the dissociation of the functional groups on the droplet surface. We show that for planar particles, the present zero-order perturbation solution is exact, and for cylindrical and spherical particles, the first-order perturbation solution provides sufficiently accurate results, with an averaged percentage deviation on the order of 1% under typical conditions. In general, the higher the surface charge density, the higher the valence of counterions, the smaller the separation distance between two particles, and the smaller the curvature of particle surface, the better the performance of the perturbation solution.     

Studies on the conductivity of copper ferrocyanide sol during slow coagulation by electrolytes

Stannic sol was prepared and its precipitation values were studied by BaCl₂ and AlCl₃ by employing the surface leaving method in the light of the equation. Different concentrations of these electrolytes were added to the sol and the corresponding times of coagulation were determined. The relation between 1/c?a of electrolyte and their respective times of coagulation was found to be linear. The constantsa, m, andn were determined for each electrolyte.