Incorporating functionalized silica nanoparticles in polyethersulfone‐based anion exchange nanocomposite membranes

In order to investigate for anion exchange membranes (AEMs) with improved properties, four series of polyethersulfone‐based composite AEMs are fabricated by incorporating pristine and three functionalized silica nanoparticles containing propylamine, trimethylpropylamine, and melamine‐based dendrimer amine groups. The results show that by choosing appropriate functional agent, anion exchange membranes with improved parameters can be achieved. The polymeric matrix of the membranes is synthesized by chloromethylation of polyethersulfone using thionyl chloride followed by amination with trimethylamine (TMA). The effectiveness of chloromethylation process is confirmed by ¹H NMR analysis. The effects of functional groups on characteristic and transport properties of the prepared composite membranes i.e., SEM, IEC, water uptake, porosity transport properties, and conductivity are investigated. The scanning electron microscope images illustrates that the synthesized membranes possess dense structures. Ion exchange capacity (IEC), water uptake, transport properties, and conductivity of the composite membranes are measured. In addition, the morphology and thermal stability are characterized. IECs and ion conductivities of up to 1.45 meq g^?1 and 45.46 mS cm^?1 and moderate transport characteristics are obtained from the modified membranes which confirm that these membranes are appropriate for applying in electro‐membrane processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44596.     

Fundamental studies of homogeneous cation exchange membranes from poly(2,6‐dimethyl‐1,4‐phenylene oxide): Membranes prepared by simultaneous aryl‐sulfonation and aryl‐bromination

Strong acid homogenous cation exchange membranes were obtained by simultaneously introducing sulfonic and bromine groups into poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). The ion‐exchange capacity (IEC), water content, transport number, diffusion coefficient, contact angle, and tensile strength of the obtained membranes were studied. The results show that the membrane intrinsic properties are largely dependent on the substitution of bromine: the IEC and water content decrease with bromine content, while the area resistance and permselectivity of the membranes increase with this trend. Therefore, by properly balancing them, a series of homogenous cation exchange membranes having good electrical properties and physical stability can be obtained to comply with different industrial electromembrane processes, such as diffusion dialysis, electrodialysis, electrodeionization, etc. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2238–2243, 2006     

Studies on transport properties of short chain aliphatic carboxylicacids in electrodialytic separation

An electrodialysis process was employed to investigate the concentration of formic, acetic and propionic acid solutions under different experimental conditions. In this process interpolymer-type ion-exchange membranes were used due their high chemical stability and durability. The effects of concentration, electric current and time on the electrodialysis process were studied. A mathematical equation representing the water transport behavior of the electrodialysis process for concentrating acids under the influence of different current densities was developed. This equation is valid for any electrodialysis process with ion-exchange membranes used under similar operating conditions. The reliability of the water transport equation was tested through comparison with the experimental data. Results indicate that electrodialysis is an effective method for concentrating shorter chain aliphatic carboxylic acid solutions. Ionic transportation, power consumption and current efficiency data reveal the following trend of the electrodialysis process's efficiency during concentration of carboxylic acid solutions: formic acid > acetic acid > propionic acid.     

Heterogeneous Cation Exchange Membrane: Preparation,Characterization and Comparison of Transport Properties of Mono and Bivalent Cations

Polycarbonate heterogeneous cation exchange membranes were prepared by solution casting techniques using tetrahydrofuran as solvent and cation exchange resin powder as functional groups agent. The effect of resin ratio loading on properties of prepared membranes was studied. Also, transport properties of the prepared membranes for mono and bivalent cations were evaluated. Scanning electron microscopy and scanning optical microscopy were used for the membranes structure investigation. Images showed that increase of resin ratio in casting solution results in a highly uniform phase to form. Formation and propagation of voids, cavities, and cracks were facilitated through higher resin ratio loading. The water content, surface hydrophilicity, specific surface area, ion exchange capacity, ion concentration, ionic permeability, conductivity, flux, and current efficiency of the membranes were enhanced and their energy consumption, oxidative stability, and mechanical strength were declined by increase of resin ratio loading. Moreover, membranes showed higher ionic flux, current efficiency, and lower energy consumption for sodium ions in comparison with bariums. Furthermore, with the increase of resin loading, permselectivity, membrane potential and transport number of membranes were improved for monovalent ions and diminished for bivalent ones. Also, membranes exhibited lower membrane potential, selectivity, and transport number for bivalent ions in comparison with the monovalent type.     

Permeability of mono-carboxylate ions across an anion exchange membrane

Transport numbers of several aliphatic and aromatic carboxylate ions across an anion exchange membrane were determined on the basis of the transport number of the co-ions across the membrane in electrodialysis. Also, the specific conductivity and water content of each carboxylate ionic-form membrane were measured.The transport number of lower aliphatic carboxylate ions decreases slowly with increasing molecular weight, but it decreases markedly where the carbon number is over five. In particular, the transport number of caprylate or of caprate ions is below 0.5, and these ionic-form membranes apparently lose the characteristics of an anion exchange membrane. For aromatic carboxylate ions, the benzoate ion a higher transport number, but p- or O-hydroxybenzoate ions only about 0.6. The specific conductivity and water content of each carboxylate ion having a lower transport number are very small compared with other carboxylate ions of higher transport number. This suggests that the hydration number and the activity of ions with a lower transport number are small in anion exchange membranes.     

Developing homogeneous ion exchange membranes derived from sulfonated polyethersulfone/N-phthaloyl-chitosan for improved hydrophilic and controllable porosity

Ion exchange membranes (IEMs) composed of sulfonated poly (ether sulfone) (SPES) and N-phthaloyl chitosan (NPHCs) were synthesized. NPHCs was employed in membrane fabrication to improve the porosity and hydrophilicity of membranes. The effect of blend ratio of sulfonation (DS) and NPHCs content on physico-chemical characteristics of home-made membranes was investigated. The morphology of prepared membranes was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD) and scanning electron microscopy (SEM). SEM images revealed the formation of a more porous membrane structure and smoother surface. The electrochemical and physical properties of CEMs were characterized comprising water content, contact angle, ion exchange capacity (IEC) and thermal stability. Membrane water content, surface hydrophilicity and IEC were enhanced with increase of DS and NPHCs blend ratios in casting solution. Furthermore, the diffusion coefficient was also improved slightly with increase of DS and NPHCs blend ratios in prepared membranes. Membrane potential, permselectivity, transport number and areal membrane resistance all showed decreasing trends by the increase in NPHCs blend ratio in casting solution. These results indicated that the prepared membrane has good prospective and great potential for desalination in electrodialysis applications.     

Effects of silica sol on ion exchange membranes: Electrochemical characterization of anion exchange membranes in electrodialysis of silica sol containing-solutions

The fouling potential of the negatively charged silica sol in electrodialysis (ED) by adsorption on the surface of an anion exchange membrane was investigated. Since the fouling potential is related to the physical and electrochemical properties of the silica sol and anion exchange membranes, it is important to characterize the properties of silica sol and membranes. The surface charge of silica sol was investigated by the electrophoretic mobility and its isoelectric point was determined as pH 3. The commercial anion exchange membranes were characterized in terms of exchange capacity, water content, the zeta potential and the electrochemical properties of the membranes using impedance spectroscopy to predict the effects on the electrodialysis performances. Among the characterized properties, exchange capacity and some electrochemical properties of the anion exchange membranes were rather improved after ED experiments. In the electrodialysis of solution containing silica sol, deposition of the silica sol did not decrease the desalting performance of the anion exchange membranes because of loosely packed cake layer on the membrane surface.     

Ion and water transport properties of cation exchange membranes prepared by heavy-ion-track grafting technique

ABSTRACT

For high-performance electrodialysis of saline water, cation exchange membranes (CEMs) that actively transport Na⁺ and restrict water permeation are required. In this study, we prepared novel CEMs by a heavy-ion-track grafting technique and measured their membrane resistance and water permeation flux as transport properties. The prepared nanostructured CEMs exhibited lower resistance and lower water flux than the commercial CEM. Na⁺ ions were efficiently transported through their unique one-dimensional ion channels (low resistance), while water transport was suppressed due to the very low water uptake of the CEMs. These results demonstrated the high potential of these nanostructured CEMs for use in practical saline water electrodialysis.     

Comparative performance of ion exchange membranes for electrodialysis of nickel and cobalt

The extraction of nickel and cobalt from their sulfate solutions by electrodialysis in a modified three compartment cell is described. Two cation exchange membranes, the perfluorosulfonic Nafion® 117 and a new sulfonated PVDF membrane, are compared under similar operating conditions. The membranes are used as either flat structures or as corrugated structures. The effect of flow rate, current density, salt concentration and temperature on the performance of each membrane is described. The performance is characterised in terms of transport properties, current efficiencies and concentrations of metal ions transported through each membrane. The performance of the PVDF membrane was as good as; if not slightly better, than that of the commercial Nafion 117. A significant improvement with the use of corrugated membranes on the amounts of metal extracted is observed. The corrugated Nafion 117 membrane gave superior current efficiencies compared to the flat one with the same amount of charged passed. Separation of cobalt from nickel by electrodialysis in mixed solution has also been investigated.     

Nitric acid and sodium hydroxide generation by electrodialysis using bipolar membranes

An electrodialysis process with bipolar membranes was used to generate HNO3 and NaOH from NaNO3 which can be found in industrial waste waters. The current efficiency of this process is limited by proton leakage through the anion exchange membrane (AEM), co-ion leakage through bipolar membranes (BPM) and water transport through the ion exchange membranes. Three cell configurations using three or two compartment cells with different anion or cation exchange membranes (CEM) in stack series were used and compared. Electrodialysis with three compartments gives the best current efficiencies for nitric acid and sodium hydroxide production from sodium nitrate.     

Ageing of ion-exchange membranes in oxidant solutions

In electrodialysis processes, membranes tend to loose some transport properties after a certain period of utilization. Two ion-exchange membranes, namely a homogeneous anion-exchange membrane (MX) and a heterogeneous cation-exchange membrane (MK-40), were used to investigate the ageing phenomenon and to highlight the characteristic parameters of these membranes which evolve most quickly with ageing. An artificial ageing was carried out under oxidizing conditions (i.e. peracetic acid, and P3 Active Oxonia^® solutions) on both membranes. It was found that an increase in conductivity and swelling rate, implying a modification of the polymer chain structure with time, but without a significant deterioration of the functional groups since the exchange capacity remained almost constant.     

A synthesis study of phosphonated PSEBS for high temperature proton exchange membrane fuel cells

A series of novel phosphonated proton exchange membranes has been prepared using poly(styrene‐ethylene/butylene‐styrene) block copolymer (PSEBS) as base material. Phosphonic acid functionalization of the polymer was performed by a simple two‐step process, via chloromethylation of PSEBS followed by phosphonation utilizing the Michaels–Arbuzov reaction. The successful phosphonation of the polymers were characterized by NMR and Fourier transform infrared. The phosphonated ester form of the membranes were obtained by solvent evaporation method and hydrolyzed to get a proton conducting membrane. The membrane properties such as ion exchange capacity, water uptake and proton conductivity at various temperatures were examined for their suitability to be utilized as a high temperature polymer electrolyte. Additionally, the morphology, thermal, and mechanical properties of the synthesized membranes were investigated, using scanning electron microscope, thermogravimetric analysis, and tensile test, respectively. The effective (anhydrous) proton conductivity was studied with respect to various degrees of functionalization. From the studies, the membranes were found to have a comparatively good conductivity and one of the membranes reached the maximum value of 5.81 mS/cm² at 140 °C as measured by impedance analyzer. It was found that the synthesized membranes were mechanically durable, chemically, and thermally stable. Hence, the synthesized phosphonated membranes could be a promising candidate for high temperature polymer electrolyte fuel cell applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45954.     

Deacidification of clarified passion fruit juice using different configurations of electrodialysis

The deacidification of clarified passion fruit juice (P edulis v flavicarpa) was investigated using the electrodialysis process (ED). Different stack configurations like conventional electrodialysis (ED2C), three compartments electrodialysis (ED3C) and electrodialysis with bipolar membranes (EDBM3C, EDBM2C) were tested. The conventional electrodialysis did not allow the deacidification of the clarified juice, whilst with the other configurations the pH of juice was increased from 2.9 (initial value) to 4.0 (target level). The ED performances were evaluated as a function of the nature of the anion exchange membrane (AEM), flow rate and current density. The physico‐chemical and sensorial properties of the deacidified juices were similar : the titrable acidity was reduced from 4.3 to 1.14% w/w, the dry soluble extract varied from 13.2 to 11% w/w, the anion concentration was significantly decreased (60% of organic and 85% of inorganic anions were eliminated), the cation concentration remained inchanged, except for the sodium concentration that increased by using ED3C and EDBM3C configurations. The aroma of the passion fruit juice was preserved after treatment whatever the ED configuration used. The EDBM2C configuration deserves a special attention because the consumption of chemicals is totally eliminated and a valuable solution of citric acid with 89% of purity can be produced. Copyright © 2003 Society of Chemical Industry     

Nanoparticles@rGO membrane enabling highly enhanced water permeability and structural stability with preserved selectivity

Developing advanced membranes with high separation performance and robust mechanical properties is critical to the current water crisis. Herein, a general and scalable fabrication of nanoparticles (NPs)@reduced graphene oxide (rGO) membranes with significantly expanded nanochannels meanwhile ordered laminar structures using in situ synthesized NPs@rGO nanosheets as building blocks is reported. Size‐ and density‐controllable NPs were uniformly grown on the regularly stacked rGO nanosheets through coordination, followed by filtration‐deposition on inner surface of porous ceramic tubes. The NPs bonded rGO building blocks enabled the as‐prepared membranes 1–2 orders of magnitudes higher water permeance than the counterparts while keeping excellent rejections for various organic matters and ions. Moreover, the industrially preferred GO‐based tubular membrane exhibited an extraordinary structural stability under high‐pressure and cross‐flow process of water purification, which is considered as a notable step toward realizing scalable GO‐based membranes. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Cr(VI) transport through ceramic ion-exchange membranes for treatment of industrial wastewaters

This work is devoted to assessment of the possibility of using ceramic membranes, which contain an ion-exchange component, such as hydrated zirconium dioxide (HZD), for Cr(VI) removal from dilute solutions by electrodialysis. Transport properties of the membranes were investigated. HZD-containing membranes were found to be permeable to anions in acidic media while they demonstrate cation-exchange properties in alkaline media. Cr(VI) anion transport through HZD membranes was studied. It was shown that an increase in the amount of ion-exchanger in the membrane results in a rise in electrodialysis efficiency. The transport number of Cr(VI) species was found to range from 0.33 to 0.63 for currents below the limiting current. It was also shown that increasing the concentration of H⁺ or Cr(VI) ions in the solution to be purified allows higher rate of Cr(VI) ion transport through the membrane.     

Preparation and characterization of monovalent ion‐selective poly(vinyl chloride)‐blend‐poly(styrene‐co‐butadiene) heterogeneous anion‐exchange membranes

New types of composite anion‐exchange membranes were prepared by blending of suspension‐produced poly(vinyl chloride) (S‐PVC) and poly(styrene‐co‐butadiene), otherwise known as styrene–butadiene rubber (SBR), as binder, along with anion‐exchange resin powder to provide functional groups and activated carbon as inorganic filler additive. Also, an ultrasonic method was used to obtain better homogeneity. In solutions with mono‐ and divalent anions, the effect of activated carbon and sonication on the morphology, electrochemical properties and selectivity of these membranes was elucidated. For all solutions, ion‐exchange capacity, membrane potential, permselectivity, transport number, ionic permeability, flux and current efficiency of the prepared membranes initially increased on increasing the activated carbon concentration to 2 wt% in the casting solution and then began to decrease. Moreover, the electrical resistance and energy consumption of the membranes initially decreased on increasing the activated carbon loading to 2 wt% and then increased. S‐PVC‐blend‐SBR membranes with additive showed a decrease in water content and a slight decrease in oxidative stability. Also, these membranes showed good monovalent ion selectivity. Structural images of the prepared membranes obtained using scanning optical microscopy showed that sonication increased polymer‐particle interactions and promoted the compatibility of particles with binder. Copyright © 2010 Society of Chemical Industry     

焦化生化出水电渗析脱盐研究

采用电渗析技术对焦化生化出水如曝气生物滤池出水及反渗透浓水进行脱盐,考察不同废水中的离子迁移、废水脱盐及离子交换膜污染情况。结果表明:2种焦化废水采用电渗析处理具有较好的脱盐效果,其中不同离子的迁移脱除与其浓度、离子半径等密切相关。膜电阻测试表明,不同焦化废水电渗析体系中不同离子交换膜的污染存在差别。扫描电镜和红外分析表明,曝气生物滤池出水主要由有机物造成阴离子交换膜污染,而反渗透浓水主要在电渗析浓室侧的膜表面形成颗粒状的无机污染,且阳膜浓室侧比阴膜浓室侧更显著。     

Effect of polymers blend ratio binder on electrochemical and morphological properties of PC/S‐PVC‐based heterogeneous cation‐exchange membranes

In this research, heterogeneous cation exchange membranes were prepared by the casting‐solution technique using polycarbonate (PC) and S‐polyvinylchloride (S‐PVC) as binders along with cation exchange resin as functional group agent. The effect of blend ratio (PC to S‐PVC) of polymer binder on structure and electrochemical properties of the prepared membranes were elucidated. The morphology of the prepared membranes was investigated by scanning electron microscopy (SEM) and scanning optical microscopy (SOM). The images show that the addition of PC ratio in the casting solution results in formation of a membrane with more inner cavities and micro voids. The electrochemical properties and mechanical strength tests were conducted. Water content, ion exchange capacity, ion permeability, flux, current efficiency, and oxidative stability of the prepared membranes initially were decreased by increasing the PC ratio in the casting solution and then it began to increase. The blending of S‐PVC and PC polymers results in membranes with lower mechanical strength. Membrane potential, surface charge density, perm‐selectivity, cationic transport number, electrical resistance, and energy consumption were initially improved by the increment of PC ratio in the casting solution and then it decreased. The membrane with 70% PC exhibited the highest flux, maximum current efficiency, and minimum energy consumption. However, the selectivity of this membrane was low compared with the other prepared membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of heat treatment on the properties of heterogeneous cation permeable membranes from blends of poly(ether sulfone)/sulfonated poly(phenylene sulfide) and phenolphthalein poly(ether ether ketone)/sulfonated poly(phenylene sulfide)

The effects of heat treatment on the properties of membranes prepared from blends of poly(ether sulfone)/sulfonated poly(phenylene sulfide) (SPPS) and phenolphthalein poly(ether ether ketone)/SPPS were studied in detail. The membranes' fundamental properties, including water content, transport number, diffusion coefficient of electrolytes, flux, and so on, changed with both treated temperature and time, whereas the ion‐exchange capacity and electrical resistance remained approximately unchanged. The trends may have been due to the possible structural change resulted from the shrinking of the polymers forming the membranes. Furthermore, the membranes also retained a good physical appearance at temperatures below 220°C. Therefore, a series of heterogeneous membranes with desired conductivities and selectivities as well as proper water contents, which could satisfy different industrial purposes, such as electrodialysis, diffusional dialysis, and proton exchange, were achieved by simple heat treatment for a proper time and at a proper temperature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 494–499, 2005     

Use of bipolar membranes for ion exchange resin regenerant production

The utilisation of electrodialysis bipolar membranes to prepare hydrochloric acid and sodium hydroxide from a sodium chloride solution was tested at West Thurrock Power Station. The product chemicals were then used to regenerate full scale ion exchange units on the site and the results compared to normal operation with commercial regenerants. The large scale pilot plant was found to operate satisfactorily and the quality of produced chemicals was in line with predictions. The adoption of on-site, on-demand production of regenerants could offer immediate advantages for remote installations which would otherwise be dependent on the transport of dangerous chemicals over long distances. In the longer term further advances in the selectivity of commercially available membranes and the prevailing cost of commercial regenerants are considered the key factors governing the future rate of implementation of this novel process.