杂化荷电镶嵌膜在有机溶液体系中膜电位

Membrane potentials across hybrid charged mosaic membrane in organic solutions were measured. Equilibrium swelling degree （SD） and fixed charge density in both organic solutions and water were also determined. Ethylene glycol, ethanol, n-propanol and glycerol were used as organic solutes; meanwhile 0.001mol-dm^-3 aqueous KCl solution was utilized as a strong electrolyte to measure the electrical difference. Equilibrium swelling degree indicated that it could be affected by the density of organic solutes; while it enhanced with the increasing density of these solutes. The measurement of fixed charge density showed that the membrane had the maximal absolute value in water among these solvents whether for cationic or anionic groups; the difference of dielectric constant between the water and the organic solutes might be responsible for these change trends. It was confirmed that membrane potentials increased with both the increasing concentration of the organic solutions and the elevated pH values. These results demonstrated that the characteristics of the hybrid charged mosaic membrane could be highly impacted by the properties of the organic solutes. A theoretical modal for charged membranes in ternary ion systems of weak electrolyte can be used to explain the above-mentioned phenomena.     

Extraction of penicillin G from aqueous solutions: Analysis of reaction equilibrium and mass transfer

Analysis of the reaction equilibrium and mass transfer in the extraction of penicillin G (Pen G) into an organic phase is an important research area to develop a cost-effective process for its separation from an aqueous fermentation media. In order to evaluate this, equilibrium experiments were first carried out to select the organic phase (composed of the carrier and solvent) that gives good values for the distribution of penicillin G between the aqueous and organic phases. An organic phase of Amberlite LA-2 in any of the solvents (Shellsol TK/butyl acetate/tributyl phosphate) gave high distribution coefficient and the stoichiometry of the reaction has been shown to follow a simple ratio of 2:2. The performance of the organic phases was evaluated in a membrane contactor and very high percentage extraction was achieved. The extraction was performed by contacting a “feed” solution containing penicillin G (flowing in the fiber side) with an “organic phase” of Amberlite LA-2 in one of the solvents (flowing on the shell side) of the contactor. The antibiotic solutes formed complex with the Amberlite LA-2 molecules which were transported across the fiber wall to the shell side and extracted in the organic phase. The extraction in once-through mode was low and the feed/organic solutions need to be recycled to increase the percentage extraction. In the recycle mode operated at flow rates of 3.6–4.4 mL/s, an extraction of 90–98% was achieved. A simple mathematical model and its semi-analytical solution presented here can be used to determine the overall mass transfer coefficient using the experimental values of the distribution coefficient, operating parameters and the dimensions of the membrane module.     

G/O/W微分散体系实现甲酸/三辛胺-正辛醇体系萃取分离

以络合萃取法实现了稀溶液中甲酸的富集。确定了高分配系数的萃取体系。根据传质基本方程建立了传质模型,计算并分析了油/水体系中的传质过程,确定传质控制步骤为甲酸自水相至水/油界面的传质。计算了分散尺寸对体系传质性能的影响,结果表明,由于水/油相比高,体系的传质系数低,界面积小,以油/水微分散乳液实现萃取过程,传质效率仍不高。引入惰性气体,并构建气/油/水体系,计算并分析了气/油/水体系中的传质过程并优化了气相加入量,结果表明,气相的加入可以有效促进传质过程。设计了双重膜分散设备,制备了微米尺度的气/油/水双重乳液,并以此实现了稀溶液中甲酸的高效富集。     

Extraction of formic acid with G/O/W microdispersion system

The enrichment of formic acid in dilute solution was achieved by complex extraction method. An extraction system with high partition coefficient was determined. The continuum model was then applied for describing mass transfer process and predicting the mass transfer characteristics in O/W system. The rate-limiting step was determined to be mass transfer of formic acid in aqueous phase, by comparison of mass transfer rates between extractant in organic phase and solute in aqueous phase. The effect of dispersion size of organic droplets on mass transfer characteristics in O/W systems was determined, indicating inefficient extraction process with low mass transfer coefficients and surficial area in O/W systems. Inert gas was introduced into extraction system and a G/O/W system was developed. The calculation of mass transfer performance in G/O/W system indicates the addition of microbubbles effectively enhances the mass transfer process. Also, suitable volumetric fraction of inert gas was optimized. According to the calculation, a double-membrane-dispersion-device was designed, with which G/O/W double emulsion was prepared and effective enrichment of formic acid from its dilute solution was realized.     

Studies in Batch and Continuous Solvent Sublation. IV. Continuous Countercurrent Solvent Sublation and Bubble Fractionation of Hydrophobic Organics from Aqueous Solutions

Abstract

Experimental results on the solvent sublation of four hydrophobic compounds [pentachlorophenol (PCP), 1,2,4-trichlorobenzene (TCB), 2,3,6-trichloroanisole (TCA), and 2,4,6-trichlorophenol (TCP)] from the aqueous phase tc organic solvents are reported. The experiments were conducted with the aqueous and air phases in continuous countercurrent modes and the organic solvent as a stagnant layer. TCB, TCA, and TCP were sublated into mineral oil. PCP at pH 2.9 as neutral molecules were sublated into mineral oil and decyl alcohol while ionic PCP at pH 8.9 were sublated as a complex with hexadecyltrimethyl ammonium bromide into decyl alcohol. The effect of the two organic solvents were compared for neutral PCP sublation from the aqueous phase. The effects of air flow rates, influent feed rates, and the volume of organic solvent were studied. Comparisons were made between the bubble fractionation and solvent sublation of neutral PCP and TCP into mineral oil. The efficiency of sublation was largest for TCB, smallest for TCP, and followed the relative magnitudes of “effective” partition constants for the solutes between the air bubble and aqueous phase.     

Diffusive permeability of ionic solutes in charged chitosan membrane

The permeabilities of three kinds of solutes with similar sizes such as anionic benzenesulfonic acid, neutral styrene glycol, and cationic theophylline in the chitosan membrane were investigated. The chitosan membrane becomes cationic below its pKa value. Benzenesulfonic acid showed the highest permeability, whereas theophylline showed the lowest, although these solutes have almost the same size. This can be explained by the electrostatic attraction or repulsion between the solute and the membrane instead of the size exclusion effect. The permeabilities of benzenesulfonic acid and theophylline increased and decreased, respectively, with the decrease of pH from 7.4 to 4.0 because of the increase of the charge density of the membrane. Thus, the selectivity of benzenesulfonic acid to theophylline increased and reached about 30 at pH 4.0, in contrast to the selectivity of nearly unity in poly(vinyl alcohol) (PVA) membrane. The partition coefficients for three solutes showed the similar tendencies to those in the permeabilities. Contrary to the results of the permeabilities, the partition coefficients increased with the increase of the degree of the crosslinking in the membrane. This is probably due to the increase of the electrostatic interaction between the solute and the membrane brought about by the smaller mesh size and also due to the increase of the bound water fraction in the membrane. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 397–404, 1999     

Analysis of countercurrent membrane vapor extraction of a dilute aqueous biosolute

Removal of dilute bioproducts from fermenter broths is a major challenge both to avoid microbe inhibition and to recover solutes economically without water loss. We analyze a proposed new process, membrane vapor extraction (MVE), where semi‐volatile dilute aqueous solutes vaporize at the upstream side of an omniphobic, microporous membrane and dissolve into a nonpolar solvent highly favorable to the solutes but not to water. A new membrane‐process analysis is outlined and applied to the countercurrent recovery of 2 wt % aqueous butanol by a prototype solvent (dodecane) at 40°C. Thermodynamic phase equilibria, pioneered by the Prausnitz school, are crucial to MVE process design. Over 90% of the feed butanol is recovered with essentially no water loss giving a separation factor of over 1000. Energy requirements in MVE are low. Our design calculations demonstrate that MVE is a viable separation process to remove and recover dilute aqueous biosolutes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2795–2809, 2015     

聚丙烯中空纤维膜在低浓度醋酸废水处理中的应用

膜萃取是膜分离与液液萃取相结合的一种新型分离技术,文中采用膜萃取技术处理糠醛生产过程中产生的大量低浓度醋酸废水.络合萃取剂选用了一定比例的络合剂、稀释剂和调节剂配制成;测定了低浓度下醋酸在萃取相和水相中的分配系数;分别用实验室热致相法制备的聚丙烯(iPP)中空纤维膜和德国Membrana商用iPP中空纤维膜,以醋酸萃取...     

Membrane stability and enrichment of nickel in the liquid emulsion membrane process

The parameters affecting the stability of a liquid emulsion membrane (LEM) for enrichment of nickel were studied. The liquid membrane is made up of a carrier (di‐2‐ethylhexylphosphoric acid), organic diluent and an emulsifying agent (sorbitan monooleate). Swelling of the internal phase during extraction results in breakage of the emulsion. The role of pH is very important in the LEM process for extraction of nickel. A significant decrease in swelling was observed by maintaining the pH of the feed phase constant during extraction. A lower osmotic pressure difference between the external and internal phase brings about lower changes in the swelling and membrane breakdown. © 2000 Society of Chemical Industry     

LIQUID MEMBRANE TRANSPORT OF CEPHALOSPORIN ANTIBIOTICS: EFFECT OF SOLUTE CHEMICAL NATURE ON CARRIER SPECIFICITY

Cephalosporin antibiotics were transported from a dilute aqueous solution (feed phase) through a bulk liquid membrane containing Aliquat-336 as an anion exchange carrier in n-butyl acetate as the solvent to another aqueous solution (receiving phase) of lower pH. Under appreciable pH gradient of the feed and receiving phases, facilitated uphill transport could be obtained. Under the optimal pH condition, the intial solute flux across the bulk liquid membrane could be correlated well with the hydrophobicity of the solutes. A linear correlation exists between the initial solute flux and hydrophobicity, indicating that the solute of higher hydrophobic nature are transported at a higher rate in the bulk liquid membrane involving the specific carrier. The correlation appears to be derived from a linear dependenc of solute hydrophobicity on equilibrium constant of the reactive extraction system being exploited in the bulk liquid membrane.     

Facilitated Transport of Zinc Chloride through Hollow Fiber Supported Liquid Membrane. Part 2. Membrane Stability

Abstract

The stability of a hollow fiber supported liquid membrane of tri-n-octylamine diluted in n-dodecane with 2-ethylhexyl alcohol was examined for the facilitated transport of zinc chloride. The liquid membrane was unstable when the feed and the strip aqueous solutions were not saturated with the organic phase used as the liquid membrane. This was found to be due to the dissolution of relatively soluble 2-ethylhexyl alcohol to the aqueous phases. When both aqueous phases were presaturated with the organic phase used, a rather constant flux could be maintained for a long time by the reimpregnation of the organic phase approximately once a day. The continuous impregnation of the organic phase to the support membrane drastically increased the stability of the liquid membrane, even without presaturation of the two aqueous phases with the organic phase     

Cation Separations Using A Proton-Ionizable Macrocycle in a Dual Module Hollow Fiber Membrane System

Abstract

Separation of metal cations in aqueous solution using a proton-ionizable macrocycle in a dual module hollow fiber membrane system is described. The advantages of this system, such as easy access to all phases, rapid transport rates, and the potential for continuous operation are maintained with the proton-ionizable macrocycles which allow for proton driven transport. Transport is diffusion limited in the organic phase boundary layer near and on the fibers. Hence, the selectivity of the extraction system is maintained. Selective transport of Ag⁺ over all other cations tested from neutral source phases and of K⁺ over other alkali metal cations from basic source phases using a triazole-18-crown-6 carrier has been demonstrated. Selective K⁺ transport from less basic source phases has been demonstrated using the more acidic thiopyridone-18-crown-6 ligand. However, the large aqueous partition of this ligand makes it difficult to maintain it in the organic phase. Design of the separation systems requires a knowledge of extraction equilibrium constants and partition coefficients. These data have been measured in order to understand these membrane systems.     

磺化聚醚砜纳滤膜性能研究

本文主要研究了磺化聚醚砜 (SPES)复合纳滤膜的性能。详细讨论了纳滤膜对不同溶质的分离特性 ;探讨了无机盐浓度 ,操作压力 ,溶液 p H值及磺化聚醚砜的离子交换容量(IEC)与膜性能的关系 ;并对纳滤膜的电性能进行了初步研究。研究结果表明 ,磺化聚醚砜复合纳滤膜为一荷负电性纳滤膜 ,对无机盐有较好的选择分离性能。磺化聚醚砜的离子交换容量 ,无机盐浓度以及操作压力对膜性能影响较大 ,且对于两性溶质 ,膜的脱除性能与溶液 p H值有关     

中空纤维支撑液膜萃取Cu(II)的传递性能

The transport of Cu(II) from aqueous solutions containing buffer media through hollow fiber supported liquid membrane (HFSLM) using di(2-ethylhexyl) phosphoric acid (D2EHPA) dissolved in kerosene as membrane phase and hydrochloric acid as striping phase was investigated. A set of factors were studied, including tube side velocity, shell side velocity, pH of the feed phase, Cu(II) concentration in the feed phase, buffer media concentration and D2EHPA concentration in the membrane phase. Experimental results indicate that the mass transfer coefficient increases with increasing both carrier concentration in the organic phase and flow rates on the tube side and shell side, and decreases with increasing initial Cu(II) concentration in the feed phase. With increasing pH value and acetate concentration in the feed phase, the mass transfer coefficient reaches a maximum value then decreases. The optimal operating conditions are obtained at pH value of 4.44 and 0.1 mol&;#8226;L－1 acetic ion concentration in feed phase, and carrier volume fraction of around 10% in kerosene as organic phase. A mathematical model of the transport mechanism through HFSLM is devel-oped. The modeled results agree well with the experimental ones.     

MASS TRANSFER OF SULFURIC ACID BY TRIOCTYLAMINE THROUGH A SUPPORTED LIQUID MEMBRANE

The extraction of sulfuric acid in a supported-liquid membrane (SLM) process, and the kinetics of extraction and stripping of sulfuric acid in a cell of constant interfacial area by trioctylamine (TOA)/kerosene solvent were investigated. The kinetics of extraction and stripping were determined by examining the effects of the operating variables. The extraction rate is a function of the activity of sulfuric acid and the concentration of TOA; the stripping rate is a function of the concentration of trioctylamine sulfate salts in the organic solution. A generalized transport model, which included the film diffusion of sulfuric acid in the aqueous phase, the membrane diffusion within the SLM, and the interfacial chemical reaction, was built. The permeability of sulfuric acid through the SLM using TOA as a mobile carrier was determined. The rate-determining step of the extraction of sulfuric acid through a SLM was analyzed using the data obtained from the experiments of extraction kinetics and the mass transfer in the aqueous phase. Diffusion within the membrane dominates the process of extraction process of sulfuric acid by TOA through a SLM.     

Carl Hanson Medal

ABSTRACT

Nondispersive equilibrium separation of citric acid from an aqueous solution by reversible chemical complexatlon with trioctyl amine in a diluent of methyl isobutyl ketone is achieved in a microporous hydrophobic hollow fiber extractor. The extractor had a shell-and-tube configuration : a total of 102 hydrophobic polypropylene (Celgard X-20, 240 μm id, 290 μm od, Hoechst Celanese) hollow fibers potted in epoxy in a stainless steel tube of 0.46 cm id. The effective fiber length vas 18.5 cm and surface area/volume was 46.8 cm. Theoretical models have been developed to predict the rate of extraction of citric acid in such systems. It essentially considers diffusion of solute molecules through the boundary layers of the two phases, in addition to the diffusion through the organic liquid occupying the membrane pores, and reversible chemical equilibrium at the phase interface. Conventionally in an aqueous-organic system having a high distribution coefficient for small solutes with a hydrophobic fiber and organic in pores, the aqueous boundary layer resistance controls. Here that is true also except when the membrane resistance of the large citric acid-amine complex diffusing through the organic-filled pores is higher than the aqueous phase boundary layer resistance. Experimental observations show further that the back extraction rate of citric acid present in the solvent (amine-organic diluent) into aqueous sodium hydroxide is much lover than the extraction rate for such a system in the sane hollow fiber extractor.     

Separation of Zinc Ions from an Acidic Mine Drainage using a Stirred Transfer Cell–Type Emulsion Liquid Membrane Contactor

Abstract

This is a report on the separation and recovery of zinc ions from an acidic mine drainage using a stirred transfer cell‐type emulsion liquid membrane contactor. Di(2‐ethylhexyl) phosphoric acid was used as a highly selective carrier for the transport of zinc ions through the emulsified liquid membrane. A study was made of the effect on the extraction extent and initial extraction rate of the following variables: pH and initial metal concentration of the feed phase, carrier content in the organic solution, a stripping agent concentration in the receiving phase, and stirring speed in the transfer cell. The content of sulfuric acid as a stripping agent did not show in the studied range any significant influence on metal permeation through the SLM, although a minimum hydrogen ion concentration of 100 g/L is suggested in the internal aqueous solution to ensure an acidity gradient between both aqueous phases to promote the permeation of metal ions toward the strip liquor. Results show that using a pH of 4.0 in the feed acid solution, a concentration of 3% w/w_o of phosphoric carrier in the organic phase and a H₂SO₄ content of 100 g/L in the strip liquor, the extent and rate of extraction through the liquid membrane can be highly favored, pointing to the potential of this method for extracting heavy metals from many kinds of dilute aqueous solutions.     

Performance of Perstractive Enzyme Reactor for Synthesis of Aspartame Precursor

A perstractive enzyme reactor was used for the synthesis of N-(benzyloxycarbonyl)-L -aspartyl-L -phenylalanine methyl ester (ZAPM), the precursor of the artificial sweetener, aspartame. The synthesis of ZAPM in the reactor proceeded by an enzymatic reaction between N-(benzyloxycarbonyl)-L -aspartic acid (ZA) and L -phenylalanine methyl ester (PM) in the aqueous phase. The synthesized ZAPM in the aqueous phase was mainly extracted into the organic phase, therefore, the concentration of ZAPM in the aqueous phase could be kept low. As a result, high conversion of ZAPM was obtained with this system. The partition coefficients of substances in the aqueous/butyl acetate biphasic system, the mass transfer coefficients of substances through the membrane and the enzymatic kinetics of ZAPM synthesis were determined experimentally. The reaction model which was based on the material mass balance equations was discussed to estimate the performance of the perstractive enzyme reactor system. The calculation values using the model and the experimental data showed good agreement with the concentration changes of the substances in the system. © 1997 SCI     

溶胀对膜萃取传质性能的影响

溶剂对膜的溶胀,使膜的物理结构发生变化,进而对膜萃取传质性能产生一定的影响。本文以３０％ＴＢＰ（煤油）－醋酸－水,正丁醇－醋酸－水和２０％７３０１（煤油）－醋酸－水为实验体系在聚砜和聚四氟乙烯微孔平板膜器中系统地了溶胀地膜萃取总传质系数的影响。结果表明,微孔膜发生溶胀后孔隙率发生明显的变化,其总传质系数有较大的下降。     

Emulsion liquid membrane pertraction of L-lysine from dilute aqueous solutions by D2EHPA mobile carrier

The results of experimental studies on the batch extraction of L-lysine by emulsion liquid membrane are discussed and the capabilities of this method in the separation of solute from dilute aqueous solutions are shown. Studies on the extraction equilibrium for organic and aqueous phases were performed. The experimental results showed that the degree of extraction was increased by an increase in the pH of the feed phase, the concentration of [H⁺] in the internal phase, and concentration of the carrier in the organic phase. An optimum value of stirring speed was achieved. The rate of water swelling as an undesirable phenomenon was also measured.