荷电膜的膜电位研究进展

膜电位的测定是表征荷电膜的传递现象的重要参数之一。本文简要介绍了膜电位理论基础,包括T. M. S.理论和不可逆热力学理论。分别阐述了关于离子交换膜、双极膜、两性膜以及复合膜的膜电位的最新进展,并提出今后的发展方向。     

膜Zeta电位测试技术研究进展

分离膜荷电化显著地影响着膜的分离性能和耐污染能力。因此,定量化表征膜表面(包括孔表面)电性能具有重要的理论价值和实际意义。本文系统地综述了各种膜Zeta电位测定原理、特点及其不足,并展望了膜Zeta电位的未来研究方向。     

平流式流动电位测试系统的研制

分离膜表面的荷电化显著地影响着膜的分离性能和耐污染能力。因此,定量化表征膜表面电性能具有重要的理论价值和实际意义。作者在前期透过式膜流动电位测试系统研发工作的基础上成功地研制了平流式流动电位测试系统,并且首次将恒电流法测膜体电导引入膜表面ζ(Zeta)电位的确定过程中。以自制不同共混比的合金荷电膜为测试对象,利用该测试系统和经典的Helmholtz-Smoluchowski(H-S)方程及其变体得到了不同pH下的膜表面Zeta电位,从而揭示了膜表面电导、膜体电导对膜表面Zeta电位的贡献,并展示了该流动电位测试系统的有效性。     

用流动电位法表征纳滤膜的结构及性能

利用测量流动电位的方法考察了纳滤膜的表面电学性能对纳滤膜的截留性能的影响.首先,采用不同功能层材料制备了复合纳滤(NF)膜,考察功能层的交联时间、单体结构等对表面电性能的影响,研究纳滤膜对不同无机盐的选择截留性能与表面电性能的关系.通过流动电位法测定纳滤膜的表面电学参数,如流动电位(ΔE)、zeta电位(ζ)和表面电荷密度(σd).实验表明,这些电学参数的变化与功能层交联时间和纳滤膜截留率的变化一致,在交联时间为45 s时,3种电学参数的绝对值均最大,而纳滤膜对无机盐的截留率也最大.复合纳滤膜zeta电位的绝对值(|ζ|)按照Na2SO4>MgSO4>MgCl2变化,同截留率的变化相同.带侧基单体交联后得到的纳滤膜的表面电性能参数的绝对值小于不带侧基单体的.因此,流动电位法可用于研究复合纳滤膜的截留机理和功能层结构.     

Potential of interaction between the lithium cation and the sulfo group of an aromatic polyamide

A three-dimensional potential for the interaction between the lithium cation and the sulfo group of an aromatic polyamide including both the Lennard—Jones and Coulomb contributions was constructed. The Coulomb contribution was calculated using the semiempirical quantum-chemical MNDO method. The potentials accounting for the changes in the electron densities at the cation and the sulfo group and neglecting these changes (the atom—atom approximation) and the corresponding energy profiles of the migration of the lithium cation in a perfectly dry membrane were compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1237–1240, July, 1995.This work was supported by the Russian Foundation for Basic Research (Project No. 93-03-4205).     

静电位阻模型在纳滤膜跨膜电位解析中的应用

采用静电位阻模型对纳滤膜的跨膜电位进行了理论解析, 考察了溶液体积通量密度、原料液浓度、阴阳离子扩散系数比、膜孔半径和膜体积电荷密度对KCl(1-1型电解质)和MgCl2(2-1型电解质)中的纳滤膜跨膜电位的影响. 研究结果表明, 随着通量密度的增大, KCl和MgCl₂的跨膜电位线性程度增强; 两种电解质的跨膜电位均随着原料液浓度和膜孔半径的增大而下降; 在不同的考察范围内, 阴阳离子扩散系数比对1-1型和2-1型电解质的跨膜电位的影响差别较大; KCl的跨膜电位随着膜体积电荷密度的变化关于零点呈现出对称性, 而MgCl₂的跨膜电位零点则出现在膜体积电荷密度为负的条件下.     

Study on the oscillating phenomena of electrical potential across a liquid membrane

The electrical oscillations across a liquid membrane in water/oil/water system was studied with octanol as oil phase by introducing two opposite charged surfactants in oil and aqueous phase, respectively. The sustained and rhythmic oscillation was observed. To a certain extent, the features of the oscillation (e.g. induction time, frequency, life time and orientation of the pulse pikes) strongly depend on the property of surfactant, dissolved in octanol. The mechanism may be explained by the formation and destruction of dual-ion surfactant membrane accompanying with emulsification at the interface and considering the coupling effect of diffusion and associated reaction in the vicinity of the interface.     

膜流动电位测试中Ag-AgCl电极的制备及稳定性研究

膜的动电特性研究中,往往采用流动电位方法。该方法中,Ag-Ag Cl测试电极的质量是影响测试准确性的关键要素。本文采用正交试验设计和方差分析,着重考察电解法制备Ag-Ag Cl电极过程中,电流强度(I)、氯化时间(t)、电解质溶液浓度(CHCl)、电极来源(n)、烘烤温度(T)、活化电极溶液浓度(CKCl)等因素对Ag-Ag Cl电极稳定性的影响。得到Ag-Ag Cl电极的最优制备参数为:电流密度3.0m A/cm2,氯化时间50min,盐酸浓度0.1mol·L-1,烘烤温度120℃,活化电极溶液(KCl)浓度0.001mol·L-1;最显著影响因素为电极来源,显著影响因素为氯化时间和烘烤温度。对最优条件组合下制备的AgAg Cl电极,进行了稳定性实验,结果表明:制备的电极具有较好的稳定性,24h内电极电位漂移量小于0.10mv,7天内电极电位漂移量小于0.2mv;在聚偏氟乙烯中空纤维超滤膜流动电位测试中,流动电位与流动压差具有良好的线性和可重复性,回归曲线R20.99,变化规律符合Helmholtz-Smoluehowski公式,可以较好满足膜的流动电位测试要求。     

Nonisothermal membrane phenomena across perfluorosulfonic acid-type membranes,Flemion S: Part II. Thermal membrane potential and transported entropy of ions

Thermal membrane potentials across the perfluorosulfonic acid-type membrane, Flemion S, were measured for HCl, alkali metal chlorides, and ammonium and methyl ammonium chlorides. The difference between the mean molar transported entropy of the counterions in the membrane and the partial molar entropy of the counterions in the external solution was determined from the experimental data on thermal membrane potential, thermoosmosis and electroosmosis. The sign of the thermal membrane potential in HCl solution varies from positive to negative with the concentration. In HCl and alkali metal chloride solutions, the order of their thermal membrane potentials (–/T) is H⁺>Li⁺=Na⁺>K⁺ which is roughly the inverse of that of the crystallographic radii of the ions. However, the order of their entropy differences is H⁺>Na⁺>K⁺>Li⁺ which is just the inverse of that of their thermoosmotic coefficients (D) or the entropy difference of water in thermoosmosis. For the ammonium and methyl ammonium ion forms, the orders of both –/T and increase with an increasing number of methyl groups: (CH₃)₄N⁺>(CH₃)₃NH⁺>(CH₃)₂NH ₂ ⁺ > CH₃NH ₃ ⁺ >NH ₄ ⁺ , which is also the inverse of that ofD or .     

荷电膜的研究进展

荷电膜以其特殊的分离机理,使之与电中性膜相比在分离性能、通量及膜的使用寿命等方面具有不可比拟的优势.大多数的荷电膜是经过一系列物理化学改性制得的,荷电膜材料的研究为新型膜材料的开发拓宽了领域,随着对膜性能要求的日益提高,荷电膜的研究具有重要的意义.本文首先介绍了荷电膜所用到的材料及其用途,并对所用到的材料进行分类,然后重点论述了荷电膜的制备及其表征方法(膜电位的测试方法),最后指出荷电膜需要进一步深入研究的内容.     

Transport Studies with Composite Membrane by Sol-Gel Method

The preparation of polystyrene-based composite 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 such as mobility, distribution coefficient, and charge effectiveness controlling the transport phenomena. The membrane potential offered by the electrolytes is in the order of LiCl > NaCl > KCl, and the membrane is found to be cation selective. The large deviation in the value of K _± at the lower concentration of electrolytes was attributed to the high mobility of comparatively free charges of the strong electrolyte. Teorell, Meyer, and Sievers (TMS) method was used for the estimation of the thermodynamically fixed charge density of membranes. The data were then utilized to calculate membrane potential using the TMS theory. It was interesting to note that the theoretical predictions were borne out quite satisfactorily with experimental results.     

Molecular dynamics study of the cations,water molecules,and polymer chains in Nafion type membranes

The structure and dynamics of the hydrated cationic complexes in Nafion type membrane pores has been studied by the molecular dynamics approach. The mechanism of the cationic transport has been examined. The dependence of the cationic transport coefficients on temperature and the number of water molecules has been investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1233–1236, July, 1995.The present work was made possible in part by financial support of the International Science Foundation (Grant MPG000) and the Russian Foundation for Basic Research (Grant 93-03-4205).     

Effects of trialkyllead compounds on mitochondrial energy conservation

The effects of triethyllead acetate and tri-n-butyllead acetate on rat liver mitochondrial ATPase, succinate-driven ATP synthase and mitochondrial membrane potential have been compared with those of the equivalent organotin compounds. ATP synthase I₅₀ values were approximately four times the ATPase I₅₀ values for organotin compounds but the reverse pattern of activity is observed with trialkyllead compounds, which are 5-10 times more effective inhibitors of ATP synthase than of ATPase activity. The primary effects of trialkyltins are as inhibitors of the ATPase complex with relatively minor effects on mitochondrial membrane potential ($PS). In contrast, trialkylleads are potent uncoupling agents, which accounts for their potent inhibition of ATP synthesis. The uncoupling action of trialkylleads and trialkyltins is independent of chloride concentration and is unlikely to be due to Cl^?/OH^? exchange.     

Electrochemical Interpretation of Propagation of the Change in the Membrane Potential Using the Goldman‐Hodgkin‐Katz Equation

Nerve conduction has been frequently explained by the Hodgkin‐Huxley equation based on the flow of K⁺ and Na⁺ across the cell membrane. By considering the relation between the membrane potential and the membrane current based on the Goldman‐Hodgkin‐Katz equation, it becomes clear that the conventional analysis using the voltage‐clamp method is not correct and that the hyperpolarization condition is artificially made. Taking into account the channel functions and the electronic properties, we suggested a new propagation mechanism. When the nerve cell is excited by an external stimulus, the ligand‐gated channels at the synapse serve as an electric power source to propagate the change in the membrane potential to the synapse terminal along the axon and the voltage‐gated channels at the axon locally assist the directional propagation along the axon.     

Electrokinetic characterization of a microporous non-commercial polysulfone membrane: phenomenological coefficients and transport parameters

Electrical and electrokinetic phenomena (electrical resistance, streaming potential and membrane potential) in a porous polysulfone membrane was studied in the framework of the linear thermodynamics of irreversible processes and the phenomenological coefficients were determined for different concentrations of NaCl and MgCl₂ solutions (10⁻³M<5×10⁻²M). From experimental values, other characteristic membrane parameters such as the concentration of fixed charge in the membrane (=−3×10⁻³M), the ionic transport numbers and permeabilities through the membrane (t(Na⁺)=0.392 and t(Mg⁺²)=0.363; P(Na⁺)=3.5×l0⁻⁸m/sec and P(Mg⁺²)=2.9×10⁻⁸m/sec) were also obtained. Membrane surface-electrolyte solution interface was characterized by zeta potential values. The effect of both salt concentration and pH on zeta potential results was also studied.     

Analysis of mitochondrial membrane potential in the cells by microchip flow cytometry

The mitochondrial membrane potential (DeltaPsi(m)) is an important indicator of the energetic state of both the mitochondria and the cells. To develop a sensitive, convenient, and rapid method for the measurement of DeltaPsi(m), we carried out cell fluorescence assays using the Agilent 2100 bioanalyzer system which, unlike the conventional flow cytometry, is based on microfluidic technology employing fluorescence detection with a 3,3'-dihexyloxacarbocyanine iodide (DiOC(6)(3)) fluorescent probe. The use of DiOC(6)(3) in the fluorometer was shown to be feasible for monitoring variations in DeltaPsi(m) in the mitochondria isolated from rat liver and treated with rotenone, succinate, ADP, and carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP). Flow cytometry analysis showed severe reduction of fluorescence intensity in Jurkat cells after treatment with 1.0 and 10 microM FCCP. However, fluorescence microscopy demonstrated obvious accumulation of fluorescence in the mitochondria and induction of diffuse cytoplasmic fluorescence not localized to the mitochondria in these cells. The dose response range of DiOC(6)(3) in the Agilent 2100 bioanalyzer system for yielding sufficient fluorescence intensity in the mitochondria of the cells was 20 nm-2.0 microM. Furthermore, significant reduction of fluorescence intensity in the cells stained with 2.0 microM DiOC(6)(3) was observed after treatment with 10 microM FCCP for 30 min. These results indicate that the Agilent 2100 bioanalyzer is potentially useful for monitoring DeltaPsi(m) in cell assays.     

Analysis of fouling potential in the electrodialysis process in the presence of an anionic surfactant foulant

Fouling of ion exchange membranes in an electrodialysis process is highly sensitive to the concentration of a surfactant. To investigate the influence of the fouling on the process performance, an anion exchange membrane was characterized by electrochemical properties as well as physical and chemical properties. The fouling potential was then quantitatively analyzed using the membrane fouling index as a function of the surfactant concentration. It was observed that the fouling mechanism is initiated by the micelle formation. That is, most of SDBS molecules form a fouling layer on the membrane surface at a higher concentration than the critical micelle concentration. Also the SDBS fouling mechanisms caused by the fouling layer were examined by the electrochemical impedance spectroscopy. The equivalent circuits show that the fouling potential of the system was increased by an additional layer, simultaneously increasing the electrical resistance to permeation of ions through the membrane. However, the SDBS fouling on the membrane was a reversible process.     

电位法测定异价阳离子通过阳离子交换膜时的选择透过性

从理论上导出了不等价的两种阳离子在通过阳离子交换膜时的选择透过性与膜电位的关系，并用电位法对一些不等价阳离子组合在两种商品膜中的选择透过性进行了测定。本方法测定结果与电渗析实际分离效果相符。     

离子-大分子半透膜扩散体系唐南平衡的建模计算与分析讨论

离子-大分子渗透体系广泛存在于自然界与人们的生产生活中。唐南平衡是一种基于膜电势平衡的离子-大分子渗透体系特殊的离子平衡条件。虽然其表述方式较为直观,但我国教科书与科研应用中对其的阐述与解释常有偏颇。首先通过提问分析,辨析了一些对唐南平衡的错误理解,进而根据大分子情况作完全分类建立了3类模型,即离子渗透入膜模型、离子透析出膜模型和两侧均有大分子模型,并通过分类与计算详细讨论了其数学过程与物理化学意义。最后,浅析了唐南平衡本身的应用局限。     

Thermal membrane potential across cation-exchange membranes for various halide solutions

Thermal membrane potential across cation-exchange membranes was measured for various halide solutions. Linear relationships between thermal membrane potential () and temperature difference (T) were observed, and the temperature coefficient of thermal membrane potential (/T) decreases with increase in the molality of the external solution as predicted by a theory reported. When counterions of membranes are hydrogen ions, the sign of the coefficients turns into minus near 0.01 mol/kg of the external solution for all membranes, although the coefficients are always positive for all the other forms. The dependence of the coefficients on the molality of the external solutions sometimes deviated slightly from the theory. This deviation is attributed to some change in water content of the membranes. A reproducible method of measuring water content of membranes was applied to discuss the change in the state of the membranes.