Self-sharpening phenomenon arisen by ion-exchange membranes in multi-compartment free-flow isoelectric focusing (IEM-FFIEF)

In this article, the self-sharpening phenomenon arisen by ion-exchange membranes is studied. In order to reduce the overlapped components in a single chamber, aminated poly(2,6-dimethyl-1,4-phenylene oxide) (APPO) based anion-exchange membranes are applied in free-flow isoelectric focusing (FFIEF) instead of conventional immobiline membranes as the selective mass transfer media. The APPO polymers with different amination rates are blended with polysulfone and cast on non-woven clothes by the phase inversion technology. Characterizations of XPS scanning, streaming potential and ion-exchange capacity (IEC) demonstrate that the self-prepared membranes posses different extent of amination and IEC values. The performances of the three prepared APPO membranes with different IEC values are compared. Nine pieces identical solid phase porous APPO membranes are employed in FFIEF instead of pH imbedded gel-like immobiline membrane with a protein mixture comprising bovine serum albumin, myoglobin and lysozyme as a separation model. Experimental results show that membranes with the higher charge density perform not only the higher mass transfer rate, but also the stronger “self-sharpening” function. Therefore, the highly charged porous membranes are favorable in reducing components’ overlaps in individual chamber for multi-component protein separations.     

离子交换膜电解分离溶液中硫酸根离子的实验研究

离子交换膜电解技术,由于膜的离子选择透过性,在分离无机离子和浓缩酸碱方面具有良好的发展前景。本文利用阴离子交换膜电解,分离(NH4)2SO4和CuSO4溶液中的SO42-。通过实验得出了电流密度对阳极浓缩H2SO4浓度的影响、温度和电流密度对电流效率的影响以及不同电流密度下最佳能耗和电流效率。     

Electro‐membrane process for the separation of amino acids by iso‐electric focusing

BACKGROUND: Amino acids (AAs) are usually produced commercially using chemical, biochemical and microbiological fermentation methods. The product obtained from these methods undergoes various treatments involving extraction and electrodialysis (ED) for salt removal and AA recovery. This paper describes an electro‐membrane process (EMP) for the charge based separation of amino acids. RESULTS: Iso‐electric separation of AAs (GLU–LYS) from their mixture, using ion‐ exchange membranes (IEMs) has been achieved by an efficient and indigenous EMP. It was observed that electro‐transport rate (flux) of glutamic acid (GLU) at pH 8.0 (above its pI) was extremely high, while that for lysine (LYS) (pH 9.6) across the anion‐exchange membrane (AEM) was very low, under similar experimental conditions. Under optimum experimental conditions, separation of GLU from GLU–LYS mixture was achieved with moderate energy consumption (12.9 kWh kg^?1), high current efficiency (CE) (65%) and 85% recovery of GLU. CONCLUSIONS: On the basis of the electro‐transport rate of AA and membrane selectivity, it was concluded that the separation of GLU–LYS mixture was possible at pH 8.0, because of the oppositely charged nature of the two amino acids due to their different pI values. Moreover, any type of membrane fouling and deterioration in membrane conductivity was ruled out under experimental conditions. This work clearly demonstrates the great potential of EMP for industrial applications. Copyright © 2010 Society of Chemical Industry     

应用ISEP系统回收氯化铵废液

ＩＳＥＰ系统是一种连续型离子交换系统，能彻底解决氯化铵废液的污染问题，并能减少树脂用量，降低碳酸钾的生产成本，有巨大的经济效益     

Removal of phosphorus from anaerobic membrane bioreactor effluent by ion exchange resin

The adsorption and regeneration mechanisms of phosphorus in anaerobic membrane bioreactor (AnMBR) effluent by anion exchange resins were investigated in this study. A strongly basic anion exchange resin (Amberlite IRA958) was selected due to its higher exchange capacity and antifouling performance. The effects of wastewater compounds, flow rate, and bed height of dynamic ion exchange column were determined. The dynamic ion exchange column exhibited stable treatment capacity and high exchange/regeneration capacity for phosphorus for long-term operation. However, humic acid could not be entirely regenerated by NaCl solution and the optimal regeneration protocol needs further investigations.     

Boron removal by ion exchange membranes

Boron removal from aqueous solution was studied through Neosepta-AHA membrane by Donnan dialysis (DD) method as a function of concentration, pH, conduct time, membrane structure and effect of accompanying ions. The feasibility of the system was examined and the highest boron removal was obtained when the pH of the feed phase was 9.5. On the other hand, it was determined that reverse flow transition was accelerated by counter ions and HCO₃⁻ ion was found to be more effective than Cl⁻ and SO₄⁻² ions. It was determined that obtained results of AHA membrane was compared with Neosepta AFN and AMH membranes and the flow rate of boron through Neosepta AHA, AFN and AMH anion exchange membranes were found to be between 3.10⁻⁸−3232.10⁻⁸ mmol cm⁻² s⁻¹ depending on concentration of feed and receiver phases, pH as well as counter ion properties. The order for recovery of boron for membranes was found to be as AFN>AMH>AHA. It could be concluded that the DD method is an appropriate method for boron removal from aqueous solution when an appropriate counter anion was chosen at suitable pH value.     

邻菲啰啉分光光度法测定离子膜碱中的三氧化二铁

介绍采用邻菲啰啉分光光度法对离子膜碱中三氧化二铁进行的测定,并就吸收曲线、邻菲啰啉铁络合物的稳定性、显色剂浓度对照试验、邻菲啰啉与铁的摩尔比、溶液酸度对络合物的影响以及共存离子消除等条件进行了探讨,以能更好地满足实际检测工作的需要.     

Cyanide detoxification by selective ion exchange with protonated poly(4-vinyl pyridine)

In order to explore the possibility of using cross-linked poly(4-vinyl pyridine), PVP, for selective removal of cyanide in waste water by complexation of the cyanide with ferrous ion followed by ion exchange, the sorption behaviour of the anionic ferrocyanide complex (Fe(CN)₆^4-) on the resin operating in an acid salt form has been studied. The results are compared with those obtained on a conventional gel-type weak base resin, Amberlite IRA-68. The ferrocyanide complex is selectively sorbed in preference to other common ions and is readily stripped with dilute sodium hydroxide. PVP has a high sorption capacity, fast sorption kinetics and a rapid rate of regeneration, being much superior to Amberlite IRA-68 in all these respects. The sorption rate is film-diffusion controlled at low solution concentrations (< 0.8 mmol litre^?1) and particle-diffusion controlled at higher concentrations (> 0.8 mmol dm^?3). Lowering pH to ～ 1 increases the sorption of Fe(CN)₆^4? on to protonated PVP by 75% over that at pH 7, a phenomenon explained by the formation of protonated ferrocyanide species, HFe(CN)₆^3- and H₂Fe(CN)₆^2-. From column operations with 156 mg dm^?3 cyanide waste stream a capacity of 73 mg CN^? g^?1 of protonated PVP to 1 mg dm^?3 breakthrough is determined, compared to 60 mg CN^? g^?1 of protonated IRA-68.     

Surface-functionalized cation exchange membrane by covalent immobilization of polyelectrolyte multilayer for effective separation of mono- and multivalent cations

The existence of numerous non-conductive regions retards the further functionalization of heterogeneous membrane surface. In this report, a modification scheme for covalent immobilization of polyethyleneimine (PEI) multilayer on heterogeneous cation exchange membrane (CEM) was developed by means of diazonium-induced carboxyl group grafting. Of particular note are the influences of some important modification conditions, including the molecular weight of PEI and its deposition times, which were explored and understood. Series of electrodialysis experiments confirmed the achievement of the monovalent cation permselectivity. Furthermore, the results also indicated that the PEI coating can also effectively improve surface homogeneity and then alleviate concentration polarization behaviour during the electrodialysis process.     

Separation of strontium and cadmium ions from nitrate medium by ion‐exchange membrane in an electrodialysis system

The separation of strontium and cadmium ions in a system containing ethylenediaminetetraacetic acid (EDTA) as a complexing agent has been studied using a three‐compartment electrolytic cell. The results suggest that under the influence of an electric field, Sr ions were exclusively transported to the cathode as positively charged uncomplexed cations while cadmium ions removed from the middle compartment of the electrolytic cell migrated to the anode as negatively charged complexes. The effect of the EDTA complexing agent on the separation was studied within the pH range 2–4 at 100 mA (12.4 mA cm^?2). Copyright © 2003 Society of Chemical Industry     

Structural effects of ion‐exchange membrane on the separation of L‐phenylalanine (L‐Phe) from fermentation broth using electrodialysis

The effects of membrane structure on the separation of L ‐phenylalanine (L ‐Phe) by electrodialysis from a fermentation broth and on the fouling tendency were investigated in this study. Two anion‐exchange membranes (Neosepta AFX and AM‐1, Tokuyama, Japan) were selected and characterized using the chronopotentiometry method. For a fresh membrane, AFX showed a lower electrical resistance and a lower permselectivity than AM‐1. After being fouled with humic acid, however, the electrical resistance of AFX was higher than that of AM‐1. The L ‐Phe selectivities for both membranes were lower than those of the fresh membranes. The result may be attributed to the structural difference between AFX and AM‐1 membranes. AFX has a lower repulsion force against the co‐ion and could be more strongly affected by the foulants than AM‐1 because AFX has a more porous structure than AM‐1. Experiments on the separation of L ‐Phe from the fermentation broth were carried out using two different stack configurations, ie desalting electrodialysis and water‐splitting electrodialysis. It was observed that the recovery efficiency of L ‐Phe through electrodialysis for 100 min reached 95% for AFX and 85% for AM‐1. In the desalting configuration of electrodialysis, the solution pH must be adjusted to alkaline conditions to recover the L ‐Phe through the anion‐exchange membrane. On the contrary, it was possible to recover the L ‐Phe without adjustment of the solution pH in the water‐splitting electrodialysis because OH^? generated from the bipolar membrane converted neutral L ‐Phe into an anion. © 2002 Society of Chemical Industry     

Pervaporation separation of dimethyl carbonate/methanol mixtures with regenerated perfluoro‐ion‐exchange membranes in chlor‐alkali industry

The waste perfluoro‐ion‐exchange membranes (PFIEMs) in chlor‐alkali industry were regenerated and used to the separation of dimethyl carbonate (DMC)/methanol (MeOH) mixtures by pervaporation process. The energy‐dispersive spectrum (EDS) demonstrates that the impurities on the surfaces of waste PFIEMs can be effectively cleared by the regeneration process. The degree of swelling, sorption, and pervaporation properties of the regenerated PFIEMs with different counter ions were investigated. The results indicate that the counter ions of PFIEMs conspicuously influence the degree of swelling, sorption, and pervaporation properties for DMC/MeOH mixtures. The degree of swelling and solubility selectivity both decreases with the alkali metal counter ions in the sequence: Li⁺ > Na⁺ > K⁺ > Cs⁺. The degree of swelling increases with MeOH concentration increasing in feed liquid. The pervaporation measurements illustrate that the permeation flux decreases and the separation factor increases with the rising in ion radius of counter ions. The increase of feed concentration (MeOH) and feed temperature is advantageous to improve permeation flux while at the cost of separation factor decreasing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Efficient separation of (R)‐(‐)‐mandelic acid biosynthesized from (R,S)‐mandelonitrile by nitrilase using ion‐exchange process

BACKGROUND: (R)‐(‐)‐Mandelic acid (R‐MA) is an important intermediate and chiral regent with broad uses. An efficient method for the separation of R‐MA from the bioreaction mixture with high yield is of great importance, thus, the main objective of this work is to investigate the recovery of R‐MA using an ion‐exchange process. RESULTS: The equilibrium isotherms for the separation of R‐MA by resin HZ202 were obtained in the pH range 5.0–9.0 and temperature range 25–35 °C. The equilibrium data are well fitted by the Langmuir isotherm. Batch kinetic experiments showed that the mobility of R‐MA^? in solution was rapid and the R‐MA^?/OH^? ion‐exchange process reached equilibrium after about 60 min. Adsorption kinetics were analyzed by a linear driving force mass‐transfer model, yielding good prediction of the kinetic behavior. In fixed bed column experiments, the breakthrough curves of R‐MA from the solution on resin HZ202 were determined at different flow rates and R‐MA was eluted with different concentrations of HCl. A favorable breakthrough curve and optimal eluant concentration were obtained. The results were used for the separation of R‐MA biosynthesized from (R,S)‐mandelonitrile with nitrilase, and separation was successfully achieved with above 90% recovery yield. CONCLUSION: Resin HZ202 presents favorable behavior for the recovery of R‐MA, in terms of capacity, kinetics, affinity, and susceptibility to regeneration. The results of this study provide an efficient method for R‐MA recovery from bioreaction mixture and could potentially be used in industry. Copyright © 2010 Society of Chemical Industry     

Polymer membranes for high temperature proton exchange membrane fuel cell: Recent advances and challenges

Proton-exchange membrane fuel cells (PEMFCs) are considered to be a promising technology for efficient power generation in the 21st century. Currently, high temperature proton exchange membrane fuel cells (HT-PEMFC) offer several advantages, such as high proton conductivity, low permeability to fuel, low electro-osmotic drag coefficient, good chemical/thermal stability, good mechanical properties and low cost. Owing to the aforementioned features, high temperature proton exchange membrane fuel cells have been utilized more widely compared to low temperature proton exchange membrane fuel cells, which contain certain limitations, such as carbon monoxide poisoning, heat management, water leaching, etc. This review examines the inspiration for HT-PEMFC development, the technological constraints, and recent advances. Various classes of polymers, such as sulfonated hydrocarbon polymers, acid-base polymers and blend polymers, have been analyzed to fulfill the key requirements of high temperature operation of proton exchange membrane fuel cells (PEMFC). The effect of inorganic additives on the performance of HT-PEMFC has been scrutinized. A detailed discussion of the synthesis of polymer, membrane fabrication and physicochemical characterizations is provided. The proton conductivity and cell performance of the polymeric membranes can be improved by high temperature treatment. The mechanical and water retention properties have shown significant improvement., However, there is scope for further research from the perspective of achieving improvements in certain areas, such as optimizing the thermal and chemical stability of the polymer, acid management, and the integral interface between the electrode and membrane.