Application Of Electrodialysis Research Articles

Nanofiber membranes by multi-jet electrospinning arranged as arc-array with sheath gas for electrodialysis applications

Multi-jet electrospinning arranged in an arc array with sheath gas has been developed for the high-efficiency production of nanofiber membranes. The arc array constrains the electric field interferences among multiple nozzles and the sheath gas in laminar flow overcomes the electric repulsive force among the jets. The stretching and focusing effect from the sheath gas reduces both the nanofiber diameter and the diameter range, which helps to realize the continuous stable multi-jet electrospinning to fabricate uniform nanofiber membranes. After the treatment of 98% concentrated sulfuric acid for the reactive exchange groups and a hot-pressing process, the membrane is then applicable to electrodialysis applications. Thanks to the net structure, there are many ion transmission passageways within the membrane, leading to the low membrane resistance and high ion transmission efficiency. Experimentally, the increase of membrane thickness results in the decrease of porosity, ion exchange capacity (IEC) and selective permeability and the increase in membrane resistance. The electrodialysis tests show good ion selection performance with a high desalinization ratio of NaCl solution.

Preparation of acid block anion exchange membrane with quaternary ammonium groups by homogeneous amination for electrodialysis-based acid enrichment

Proton leakage defect of anion exchange membrane (AEM) seriously restricts the applications of electrodialysis (ED) in acid enrichment. Different from conventional scheme in which weak base groups are usually introduced, strong base AEMs are endowed with acid block property by the specific design of membrane microstructure in this work. Firstly, as confirmed by 1H NMR and FTIR, a series of quaternary ammonium polysulfone containing long alkyl side chains pendant are synthesized for AEM preparation. Small Angle X-ray Scattering experiments show that ionic domains form a distinct and well-separated phase. The introduced hydrophobic side chains strengthen the hydrophobic matrix and then restrict AEM water uptake. Besides, some interesting confinement effects are observed, for examples, the reinforcement of Donnan exclusion for H+ and facilitated transport of counter-ions. Furthermore, influences of pendant carbon chain length and ion exchange capacity are investigated. Notably, ED measurements show as-prepared AEMs indeed display excellent acid block performance, a current efficiency of almost 100% under certain condition, which substantially exceeds that of conventional AEM fabricated by heterogeneous aminaiton. This observation demonstrates an unprecedented result that novel strong base AEM with both outstanding acid block performance and membrane conductivity can be achieved by constructing phase separation microstructure.

Quaternized graphene oxide modified PVA-QPEI membranes with excellent selectivity for alkali recovery through electrodialysis

Composite anion exchanges membranes are prepared by incorporating quaternized graphene oxide (QGO) within poly(vinyl alcohol) (PVA) or the mixture of PVA and quaternized polyethyleneimine (QPEI), followed by cross-linking with formaldehyde. The PVA-QGO series of membranes have low ion exchange capacities (IECs) of 0.10–0.37mmol/g and low water uptakes (WR) of 16.1%–22.0%, leading to high area resistances (>60Ωcm2). The PVA-QPEI-QGO series of membranes show much lower area resistances of 2.47–6.04Ωcm2, which is ascribed to the improved IECs (0.86–1.37mmol/g) and WR (46.8%–71.4%). Both series of membranes show higher alkali resistance than commercial membrane AMV. Their weight losses are in the range of 0.5%–8.9% after immersion in 60°C 2mol/L NaOH alkaline solution for 32 days, while the value of AMV membrane is 19.2%. When utilized for electrodialysis (ED) application to recover NaOH from NaOH/Na2WO4 mixture, the prepared membranes exhibit high selectivity, as evidenced by the low leakage ratio of Na2WO4. The leakage ratio of the optimized composite membrane to WO42− is only 5.1%, while the leakage ratio of AMV membrane is up to 61.4%. To explore this reason, the composite membranes are selected for the ED separation of monovalent ions. The separation efficiency (S) of the optimized membrane is 83.9%, which is similar to the value of commercial anion selective membrane NEOSEPTA® ACS (88.7%), confirming further the selectivity of the composite membranes.

Property evaluation of custom-made ion exchange membranes for electrochemical performance in reverse electrodialysis application

Reverse electrodialysis (RED) is an emerging energy conversion process that utilizes the ion exchange membranes for salinity gradient power generation. As a primary component in RED, the development of suitable ion exchange membrane is crucial for sustainable energy harvest from various forms of salinity gradients. However, a great challenge still exists in designing and tailoring the RED membranes due to lack of understanding of the complexed relationships among properties of the membranes. This work presents the physical and electrochemical properties of a series of custom-made and commercial IEMs and investigates an interconnected relationship that affects the performance. Also, various membrane combinations comprised of custom-made and commercial membranes are tested in RED stack to evaluate the significance and dependency of the key membrane properties toward the power output via RED. The findings of this study suggest that the membranes having lower area resistance is much more influential regardless of its permselectivity level to perform better in RED. In this work, a combination of custom-made membranes with significantly low area resistance as well as low permselectivity obtained the highest power density. This observation implies that the ion conductance through the membrane should be the priority concern for the power generation in RED than ion selectivity of membrane. The result of this work provides the direction of effective membrane design with proper property orientation for RED application.

Application of reverse electrodialysis to site-specific types of saline solutions: A techno-economic assessment

Salinity gradients are a non-conventional source of renewable energy based on the recovery of the Gibbs free energy related to the mixing of solutions at different concentrations. Reverse Electrodialysis is a promising and innovative technology able to convert this energy directly into electric current. The worldwide availability of salinity gradients is limited to those locations where water bodies at different salinity levels are present. The present work analyses a number of different scenarios worldwide, in locations where salinity gradients are naturally available or generated by anthropogenic activities. A techno-economic model of the Reverse Electrodialysis process is presented. The model is used to evaluate the energy that can be harvested in each real scenario using a reverse electrodialysis plant and relevant results are reported in terms of power densities and energy yields. Finally, an economic analysis based on the estimation of the Levelized Cost Of Electricity (LCOE) for each scenario is presented, and perspective considerations are reported. Results suggest that competitive values of LCOE may be achieved in some scenarios.

(Invited) Low Ionic Resistance Radiation-Grafted Cation- and Anion-Exchange Membranes for Reverse Electrodialysis (salinity gradient power) Application: Cross-Linking Is Essential for High Permselectivities.

Reverse electrodialysis (RED) cells are a form of salinity gradient power technology where electrical energy can be recovered from the mixing of waters of differing salinities. RED cells require both cation- and anion-exchange membranes (CEM and AEM, respectively) in order to operate. This presentation details the development of radiation-grafted (RG) CEMs and AEMs, which were evaluated for ex situ resistances (conductivities) and permselectivities. Trends between ex situ properties will be discussed (e.g. room temperature Na+ conductivities (in water) are higher with RG-CEMs that possess higher gravimetric water uptakes, see Figure). It is clear that RG-CEMs and RG-AEMs are desirably low resistance. However, non-crosslinked RG-CEMs and RG-AEMs have permselectivities that are too low for application in RED cells. However, the addition of crosslinking (either via the addition of divinyl-monomers, such as BVPE, or through the use of difunctional amination agents, such as N,N,N',N'-tetramethylhexane-1,6-diamine) leads to higher permselectivity types. Therefore, we conclude that cross-linking is essential for the production of RG-ion-exchange membranes with high permselectivities for such application. Figure 1

Fabrication and practical applications of molybdenum disulfide nanopores.

Among the different developed solid-state nanopores, nanopores constructed in a monolayer of molybdenum disulfide (MoS2) stand out as powerful devices for single-molecule analysis or osmotic power generation. Because the ionic current through a nanopore is inversely proportional to the thickness of the pore, ultrathin membranes have the advantage of providing relatively high ionic currents at very small pore sizes. This increases the signal generated during translocation of biomolecules and improves the nanopores' efficiency when used for desalination or reverse electrodialysis applications. The atomic thickness of MoS2 nanopores approaches the inter-base distance of DNA, creating a potential candidate for DNA sequencing. In terms of geometry, MoS2 nanopores have a well-defined vertical profile due to their atomic thickness, which eliminates any unwanted effects associated with uneven pore profiles observed in other materials. This protocol details all the necessary procedures for the fabrication of solid-state devices. We discuss different methods for transfer of monolayer MoS2, different approaches for the creation of nanopores, their applicability in detecting DNA translocations and the analysis of translocation data through open-source programming packages. We present anticipated results through the application of our nanopores in DNA translocations and osmotic power generation. The procedure comprises four parts: fabrication of devices (2-3 d), transfer of MoS2 and cleaning procedure (24 h), the creation of nanopores within MoS2 (30 min) and performing DNA translocations (2-3 h). We anticipate that our protocol will enable large-scale manufacturing of single-molecule-analysis devices as well as next-generation DNA sequencing.

Modification of cation exchange membranes with conductive polyaniline for electrodialysis applications

In this study, composite cation exchange membranes (C-CEMs) based on polyvinyl pyrrolidone (PVP) and mainchain sulfonated polyethersulfone (SPES) were prepared by adding conducting polyaniline (PANi). The electrodialysis (ED) properties of these C-CEMs were characterized to determine their feasibility for practical applications. C-CEMs exhibited smooth surfaces and dense cross-sections when PANi was homogeneously dispersed in the matrix material. An increase in C-CEM mechanical stability was attributed to the formation of a crosslinked structure. The experimental results showed that C-CEM with 0.6% PANi possessed the highest ionic conductivity. ED process results showed that C-CEM with 0.6% PANi exhibited better desalination properties than those of other C-CEMs and commercial CEM. On the whole, an appropriate PANi content improved C-CEM desalination properties. This study detailed a new method for the preparation of novel, low-cost C-CEMs with improved properties. It was found that a 0.6% PANi content was optimal for improving membrane performance.

Electrodialysis Application of the Ultrafiltration Permeate of Milk Before and After Reverse Osmosis

AbstractUltrafiltered (UF) milk permeate was concentrated by reverse osmosis (RO). UF and UF + RO samples were then desalted by electrodialysis (ED) to three levels of desalination: 1, 2.5, and 4 % of ash in the dry matter. Ions were analyzed by a new high‐performance liquid chromatography method, which enables simultaneous estimation of cations and anions. ED of UF permeate has some advantages over that of UF + RO samples, including a shorter ED time and a higher average salt flow rate, but RO treatment of UF permeate before ED enables the processing of larger volumes of UF permeate. Therefore, ED of milk permeate, particularly after RO, improves the handling characteristics and may offer advantages for further processing of secondary dairy products.

Removal of Methylene blue from saline solutions by adsorption and electrodialysis

In this study, the removal of MB from saline solutions was evaluated by two methods by adsorption and electrodialysis; the adsorption of the mixture dye/salt on dried orange peel waste (OPW) was studied in batch method. In this study the biosorption of cationic dye by OPW was investigated as a function of initial solution pH, and initial salt (sodium chloride) concentration. The maximal dye uptake at pH >= 3.6 in the absence and in the presence of salt and the dye uptake diminished considerably in the presence of increasing concentrations of salt up to 8 g/L. The Redlich Peterson and Langmuir were the most suitable adsorption models for describing the biosorption equilibrium data of the dye both individually and in salt containing medium. As well, this work deals with the electrodialysis application to remove the dye. Synthetic solutions were used for the investigation of the main operational factors affecting the treatment performance; such as applied voltage, pH, initial dye concentration and ionic strength. The experimental results for adsorption and electrodialysis confirmed the importance of electrostatic interactions on the dye. The electrodialysis process with standard ion exchange membranes enabled efficient desalination of cationic dye solutions; there are two main factors in fouling: electrostatic interaction between cations of dyes and the fixed charged groups of the CEM, and affinity interactions.

Electrodialysis applied to the treatment of an university sewage for water recovery

The objective of this study was to evaluate the application of electrodialysis (ED) as tertiary treatment of a university effluent aiming at the water recovery and reuse in three alternatives: agricultural, urban and fish farming. The study evaluated the behavior of membranes and effluent quality after successive batches of electrodialysis treatment, without cleaning the system, using the same effluent and with the monitoring of the electrical potential of the system during the treatment. Despite the electrical potential of the system increase at the end of each batch treatment, the transport of ions through the membranes was not compromised. The results showed the removal of ammoniacal nitrogen (95–98%), total (80–99%) and dissolved (80–97%) solids, total inorganic carbon (40–97%), cations (>80%) and anions (>70%), indicating that, for these parameters, the treatment by electrodialysis was an interesting alternative. Besides the aim of ED is the removal of electric charged compounds, it was observed the removal of color (23–44%), turbidity (48–62%), Chemical Oxygen Demand (COD) (49–62%), Biochemical Oxygen Demand (BOD5,20) (38–52%), total carbon (29–45%) and total organic carbon (16–36%), but, in lower levels than that obtained for ions removal. These data suggest the application of another type of treatment before or after electrodialysis. Based on these results, the agricultural or urban reuse alternatives are indicated, where only pH and turbidity correction are necessary. For the use in fish farming, pH correction should be performed.

Amphoteric ion-exchange membranes with superior mono-/bi-valent anion separation performance for electrodialysis applications

Fabricating stable mono-/multi-valent anion-selective membranes with high perm-selectivity for electrodialysis (ED) applications is critical but challengeable. In this work, we have fabricated a series of novel homogeneous monovalent anion-selective amphoteric ion-exchange membranes (AIEMs, PAES-im-Xc) based on a long-side-chain type imidazolium-functionalized poly(arylene ether sulfone) cross-linked with 4,4′-diazostilbene-2,2′-disulfonic acid disodium salt (DAS) for ED. By tuning the mass percent of DAS added, low swelling ratio but appreciably high anion perm-selectivity (in Cl–/SO42– system) of optimized AIEM are achieved to values of 8.0% and 47.12 at current density of 2.5 mA cm–2, respectively. In particular, at an enhanced current density of 5.0 mA cm–2, its perm-selectivity reaches 12.5, significantly outperforming commercial monovalent anion-selective Neosepta ACS (5.27). The appreciably high perm-selectivity possibly arises from pore-size sieving effect from dense matrix structure with cross-linkings and strong electrostatic repulsion between negative fixed –SO3– groups and negative divalent ions of SO42– in feeding solution. The superior performances might be particularly interesting findings that can facilitate the development of advanced mono-/bi-valent anion-selective membranes in applications of sea water desalination, resource recovery and water treatment/pretreatment etc..

Application of homogeneous membrane electrodialysis in the treatment of high-salt organic wastewater

In this paper, a homogeneous membrane electrodialysis system was used to separate the high COD and high sulfate concentrated water from a non-ferrous metal plant. After continuous pilot test, the results showed that the homogeneous membrane electrodialysis method has the characteristics of low energy consumption, high concentration ratio, strong ion selective permeability and effectively remove organic matter. Therefore, the production cost can be reduced and the recycling of waste water resources can be realized.

PPO/PVA hybrid membranes for application in bipolar membrane electrodialysis

PPO/PVA hybrid membranes for application in bipolar membrane electrodialysis

Fabrication of photocured anion-exchange membranes using water-soluble siloxane resins as cross-linking agents and their application in reverse electrodialysis

The utilization of large amounts of volatile organic solvents and the complicated process required for industrial manufacturing of ion-exchange membranes necessitate the development of simple, rapid, and environmentally friendly fabrication methods such as those based on photopolymerization. We employed hydrolytic sol–gel reactions between ammonium- and acrylamide-functionalized silane coupling agents to synthesize water-soluble siloxane resins that exhibit high condensation levels (>80%) and comprise oligomers with molecular weights below 2000 Da. These resins were then mixed with a hydrophilic monomer bearing ammonium and acrylamide groups, and porous polyethylene substrates were impregnated with the resulting mixtures and then irradiated with ultraviolet light. The hydrophilicity, mechanical strength, and other properties of the resulting membranes depended on the resin composition, indicating that the substrate pores were efficiently filled with the prepared resins and further suggesting that the membrane performance could be effectively altered by varying the resin composition. Moreover, the obtained membranes exhibited chemical stability in the pH range between 0 and 11 and in hot water at 60 °C. The reverse electrodialysis stack consisting of these membranes showed higher power density than a stack of commercial membranes. Therefore, it can be concluded that without employing volatile organic solvents for reverse electrodialysis, the developed technique is well-suited for the fabrication of ion-exchange membranes.

Effect of acid-base solutions used in acid-base compartments for simultaneous recovery of lithium and boron from aqueous solution using bipolar membrane electrodialysis (BMED)

Application of bipolar membrane electrodialysis (BMED) for simultaneous separation and recovery of lithium and boron from aqueous solution was investigated using Astom Acilyzer EX3B model ED device. In the laboratory scale experiments performed, effects of acid and base solutions types and their concentrations employed in acid and base compartments, electrical potential applied on process efficiency were investigated. The results showed that separations and recoveries of both boron and lithium were effective when 0.05 M HCl and 0.05 M NaOH solutions have been used in acid and base compartments, respectively. The percent separations of boron and lithium were 86.9% and 94.7%, respectively, while their respective recoveries were 50% and 62% at 30 V. The maximum separation and recovery values for boron and lithium were obtained when a 30 V of electrical potential was applied. With optimal initial acid and base concentrations (0.05 M) used in acid and base compartments, the specific power consumption (SPC) was calculated as 7.9 kWh/m3 at 30 V.While higher initial acid and base concentrations showed higher boron and lithium separation efficiencies, relatively lower concentrations of acid and base solutions employed in acid and base compartments improved the recoveries of boron and lithium. Acid and base solutions generating a moderate conductive medium in acid and base compartments improved separations along with recoveries of boron and lithium from solution. When the solutions of 0.1 M HCl and 0.1 M NaOH were used in acid and base compartments, recoveries of boron and lithium were 27% and 33%, respectively. On the other hand, the recoveries of boron and lithium were 62% and 56%, respectively when 0.1 M H3BO3 and 0.1 M LiOH solutions were employed in acid and base compartments.

Improvement of the antifouling performance and stability of an anion exchange membrane by surface modification with graphene oxide (GO) and polydopamine (PDA)

A novel surface modified anion exchange membrane (AEM) was prepared by electrodeposition of graphene oxide (GO) and polydopamine (PDA) coating, aiming at improving antifouling performance and stability. The AEM was firstly modified by electrodeposition of GO and then immersed into the dopamine solution to form a thin PDA layer. The effects of GO and PDA composite modification were investigated by various analytical techniques and electrodialysis application. The GO@PDA-modified AEM (GO@PDA-M) exhibited highly hydrophilic and negatively charged. In addition, the introduction of PDA coating helped to construct a smoother and denser composite modifying layer composed of GO and PDA, and reduced the roughness of membrane surface. Depending on these properties, the GO@PDA-modified AEM showed significant antifouling ability without compromising the desalination performance. After being fouled by 150 mg/L sodium dodecyl benzene sulfonate (SDBS) for 4 h, the desalination rate of GO@PDA-M increased by 39.3% compared to pristine membrane, while for PDA-modified membrane (PDA-M) and GO-modified membrane (GO-M) were 5.7% and 18.2% respectively. Moreover, it still maintained antifouling ability after 20 h of continuous operation. The stability of GO@PDA-M was immensely improved compared with the GO-M due to the introduction of PDA layer.

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.

SORPTION OF AMINO ACID AND CHANGES IN HYDRATION OF HETEROGENEOUS CATION- AND ANION-EXCHANGE MEMBRANES FUMASEP

Hydration of heterogeneous cation-exchange membranes Fumasep FTCM and anion-exchange membranes Fumasep FTAM in hydrogen and hydroxyl forms, respectively, sorbing tyrosine as well as of the samples being used in electrodialysis concentration of tyrosine solution was studied using the methods of thermogravimetry and IR-spectroscopy. It was revealed that tyrosine sorption and membranes application in electrodialysis of this amino acid solution causes membranes hydration decrease. The decrease in membrane hydration after its contact with tyrosine leads to membrane surface hydrophobicity grow up and, consequently, make significant influence on amino acid’s mass transfer.

Synthesis of cation exchange membranes based on sulfonated polyether sulfone with different sulfonation degrees

Composite cation exchange membranes (C-CEMs) based on mainchain sulfonated polyether sulfone (SPES) and polyvinyl pyrrolidone (PVP) have been prepared and the effects of hydrophilicity on C-CEM properties investigated in a previous work. In this study, membrane properties were optimized by investigating the effects of degrees of sulfonation (DS) on CEM properties. SPES with different DS were synthesized and C-CEMs based on PVP and SPES with different DS easily prepared. SPES structures were characterized by FTIR and the DS tested by acid-base titration. TGA, XRD, AFM, and SEM were used to characterize membrane properties and the results showed that C-CEM hydrophilicity increased with increased DS and the ionic conductivity increased accordingly. The ionic conductivity of S-25/P membrane was 0.098 S/cm and higher than the ionic conductivity of commercial TingRun membrane, at 0.082 S/cm. The feasibility for actual electrodialysis (ED) applications was also explored. ED experiments showed that S-20/P membranes possessed better desalination effects than those of TingRun membranes. Increased DS contributed to the formation of higher densities of ionic clusters and the availability of more ion transport channels. Synergistic effects between ionic clusters and hydrophilicity for ion transport were more significant with increased DS. This study demonstrated that C-CEMs based on mainchain SPES and PVP were optimized by properly improving the DS.