Pair Of Membranes Research Articles

Brine management from desalination plants for salt production utilizing high current density electrodialysis-evaporator hybrid system: A case study in Kuwait

The potential of producing salt and low salinity water by treating synthetic brine was investigated in a pilot-scale electrodialysis-evaporator hybrid system as part of brine management. An electrodialyzer with 25 cell pairs of monovalent selective anion exchange membranes (AEMs) and monovalent selective cation exchange membranes (CEMs) were used. Effect of three different current densities (300 to 500 A/m2) and two different flowrates (400 L/h and 450 L/h) on brine treatment were evaluated in the current study. The results indicated that the aforementioned membranes were efficient in separating monovalent ions over divalent ions. Moreover, higher current density operation was favoured during the electrodialysis (ED) operation as the operation time for producing salt was shorter. Flowrate is a crucial parameter for the operation of the ED system, where higher flowrate (by 12.5%) reduced the operation time (by 30 min), reduced energy consumption (by 32%) and reduced system resistance (by 32.42%) leading to an increase in current efficiency (by 31.4%). The concentrated brine effluent from ED was fed to an evaporator to produce coarse salt with 84.75% salt recovery and low salinity water of 1526 ppm. Thus, ED-evaporator hybrid system was found to be a good option to treat reject brine from desalination plants.

Role of Protein-Water Interface in the Stacking Interactions of Granum Thylakoid Membranes-As Revealed by the Effects of Hofmeister Salts.

The thylakoid membranes of vascular plants are differentiated into stacked granum and unstacked stroma regions. The formation of grana is triggered by the macrodomain formation of photosystem II and light-harvesting complex II (PSII-LHCII) and thus their lateral segregation from the photosystem I—light-harvesting complex I (PSI-LHCI) super-complexes and the ATP-synthase; which is then stabilized by stacking interactions of the adjacent PSII-LHCII enriched regions of the thylakoid membranes. The self-assembly and dynamics of this highly organized membrane system and the nature of forces acting between the PSII-LHCII macrodomains are not well understood. By using circular dichroism (CD) spectroscopy, small-angle neutron scattering (SANS) and transmission electron microscopy (TEM), we investigated the effects of Hofmeister salts on the organization of pigment-protein complexes and on the ultrastructure of thylakoid membranes. We found that the kosmotropic agent (NH4)2SO4 and the Hofmeister-neutral NaCl, up to 2 M concentrations, hardly affected the macro-organization of the protein complexes and the membrane ultrastructure. In contrast, chaotropic salts, NaClO4, and NaSCN destroyed the mesoscopic structures, the multilamellar organization of the thylakoid membranes and the chiral macrodomains of the protein complexes but without noticeably affecting the short-range, pigment-pigment excitonic interactions. Comparison of the concentration- and time-dependences of SANS, TEM and CD parameters revealed the main steps of the disassembly of grana in the presence of chaotropes. It begins with a rapid diminishment of the long-range periodic order of the grana membranes, apparently due to an increased stacking disorder of the thylakoid membranes, as reflected by SANS experiments. SANS measurements also allowed discrimination between the cationic and anionic effects—in stacking and disorder, respectively. This step is followed by a somewhat slower disorganization of the TEM ultrastructure, due to the gradual loss of stacked membrane pairs. Occurring last is the stepwise decrease and disappearance of the long-range chiral order of the protein complexes, the rate of which was faster in LHCII-deficient membranes. These data are interpreted in terms of a theory, from our laboratory, according to which Hofmeister salts primarily affect the hydrophylic-hydrophobic interactions of proteins, and the stroma-exposed regions of the intrinsic membrane proteins, in particular—pointing to the role of protein-water interface in the stacking interactions of granum thylakoid membranes.

How Does Protein Zero Assemble Compact Myelin?

Myelin protein zero (P0), a type I transmembrane protein, is the most abundant protein in peripheral nervous system (PNS) myelin—the lipid-rich, periodic structure of membrane pairs that concentrically encloses long axonal segments. Schwann cells, the myelinating glia of the PNS, express P0 throughout their development until the formation of mature myelin. In the intramyelinic compartment, the immunoglobulin-like domain of P0 bridges apposing membranes via homophilic adhesion, forming, as revealed by electron microscopy, the electron-dense, double “intraperiod line” that is split by a narrow, electron-lucent space corresponding to the extracellular space between membrane pairs. The C-terminal tail of P0 adheres apposing membranes together in the narrow cytoplasmic compartment of compact myelin, much like myelin basic protein (MBP). In mouse models, the absence of P0, unlike that of MBP or P2, severely disturbs myelination. Therefore, P0 is the executive molecule of PNS myelin maturation. How and when P0 is trafficked and modified to enable myelin compaction, and how mutations that give rise to incurable peripheral neuropathies alter the function of P0, are currently open questions. The potential mechanisms of P0 function in myelination are discussed, providing a foundation for the understanding of mature myelin development and how it derails in peripheral neuropathies.

Improving the performance of polymer-flooding produced water electrodialysis through the application of pulsed electric field

Concentration polarization and fouling hamper the desalination of polymer-flooding produced water (PFPW) via electrodialysis (ED). This water is an abundant by-product from the oil and gas industry. A common technique to mitigate both problems is the application of pulsed electric field (PEF), which consists in supplying a constant current during a short time (pulse) followed by a time without current (pause). Accordingly, this work evaluated the application of PEF during the ED of PFPW to improve the process performance and to reduce fouling incidences. The experimental work consisted in performing ED batch runs in a laboratory-scale stack containing commercial ion exchange membranes. Synthetic PFPW was desalinated under different operating regimes until a fixed number of charges were passed. After each experiment, a membrane pair was recovered from the stack and analyzed through diverse techniques. The application of PEF improved the ED performance in terms of demineralization percentage and energy consumption, the latter having reductions of 36% compared to the continuous mode. In general, the shorter the pulses, the higher the demineralization rate and the lower the energy consumption. Regarding the application of different pause lengths, longer pauses yielded lower energy consumptions, but also lower demineralization. Amorphous precipitates composed of polymer and calcium fouled most on the anion and cation exchange membranes, independently of the applied current regime, but in a moderate amount. Finally, the present study relates the observed effects of PEF application to the electrophoresis and diffusion of HPAM, and shows that PEF is a sound option to enhance the desalination of PFPW.

Simultaneous desalination and nutrient recovery during municipal wastewater treatment using microbial electrolysis desalination cell

The removal of organics and saline while simultaneously recovering nutrients in municipal wastewater was achieved in a microbial electrolysis desalination cell (MEDC). System performance in terms of organics removal, desalination, and nitrogen and phosphate recovery was investigated under different ion exchange membrane (IEM) pairs and applied voltages. Compared with single-IEM stack MEDC, the MEDC with multi-IEM pairs proved to be able to perform an effective performance for chemical oxygen demand (COD) removal, desalination, and nutrient recovery. The energy consumption for netrient separation and recovery was 0.12 kWh/m3 with 3-IEM stacks at applied voltage of 2 V. The MEDC system with 3-IEM stacks showed 75.5 ± 1.4% COD removal and 8.5 ± 1.1% Coulombic efficiency. The conductivity in effluent decreased to 545 μS/cm (lower than the single-IEM stack, 934 μS/cm), while conductivity in the product chamber was concentrated to 2160 μS/cm (higher than the single-IEM stack, 998.5 μS/cm). Moreover, the recovery efficiencies of nitrogen and phosphate reached 66 ± 5.3% and 66.7 ± 4.7%, respectively. Furthermore, the CV curve and microbial community structure showed that electrical stimulation increased the abundances of electrogenic bacteria (Rhodocyclaceae and Geobacter), which enhanced COD removal and electron transfer. These results clearly demonstrate that the MEDC is an energy efficient technology for the treatment of municipal wastewater, while simultaneously recovering nitrogen and phosphate resources.

Interpolymer ion exchange membranes for CapMix process

In the presented paper interpolymeric ions exchange membranes were used in a capacitive mixing process. This was reach to increase the amount of energy generated during mixing waters with two different salinities. Membranes were prepared by extrusion of ethylene/styrene-co-divinylbenzene interpolymer followed by chemical modification of obtained foils. The extrudate contained 30 wt% of polystyrene crosslinked with different amount of divinylbenzene. Four pairs of membranes of different thickness were tested in CapMix process. It was found that the best membranes for energy harvesting were obtained from interpolymer with 2 wt% of DVB.

Using integrated electrodialysis and RO hybrid system to remediate and reclaim perchlorate-contaminated groundwater

Perchlorate (ClO4−) is a highly oxidizing and water soluble chemical. In this study, a hybrid electrodialysis reversal and reverse osmosis process (EDR + RO) was designed to remediate and reclaim perchlorate-contaminated groundwater. The EDR tests were conducted using a laboratory-scale equipment with seven pairs of ion-selective membranes and a total membrane area of 352 cm2. Up to 95% of perchlorate could be removed in 2.5 h of operation with a voltage of 40 V. The effluent perchlorate concentration dropped to below 0.02 mg/L after the two-stage treatment (EDR followed by RO). Bimetallic nanoparticles Fe0/Al0 (nZVI-coated nZV aluminum) were applied to reduce perchlorate via chemical reduction. Approximately 30.8% of perchlorate could be removed by Fe0/Al0 reduction. Strong acidic functional group (SO3H) on the EDR cation exchange membrane was electrolyzed, which resulted in the accumulation of sulfur content on the ion-exchange membrane. Results from the 3-D excitation-emission fluorescence matrix (EEFM) analyses show that the most proportion of organic matters in groundwater were type II and type IV that are aromatic protein (AP) and soluble microbial by-product-like (SMP) chemicals. The system could electrolyze perchlorate and generate hydrochloric acid (HCl), which could inhibit the hydroxide production and minimize the fouling on the RO membrane.

Effect of channel geometry on ion-concentration polarization-based preconcentration and desalination.

Polarization of the ion-selective systems results in the formation of ion-depleted and ion-concentrated zones in the electrolyte layers adjacent to the system. One can employ ion-concentration polarization for the removal of charged large molecules and small ions from the flowing liquid. Removal of large molecules from the flowing solution and their local accumulation is often referred to as preconcentration, removal of small ions as desalination. Here, we study the effect of the channel geometry on the removal of charged species from their water solutions experimentally. Straight, converging, and diverging channels equipped with a pair of heterogeneous cation-exchange membranes are compared in terms of their effect on preconcentration of an observable fluorescein dye and on desalination of water solution of potassium chloride. Our results show that preconcentration of the dye is not significantly affected by the channel geometry. The distance of the preconcentration band from one of the membranes was approximately the same in all tested channel geometries. The major difference was in the location of the band within the channel, when the conical channels localized the band at one of the channel walls. The straight channel showed a slightly broader range of applicable flow rates. The semibatch desalination of 0.01M KCl solution turned out to be more efficient in conical channels, which was associated with a larger volume of the channel available for the accumulation of the concentrated solution. Our results suggest that conical channels can be advantageously used in transforming the ion-concentration-polarization-based semibatch desalination into a fully continuous one.

Flow-electrode capacitive deionization (FCDI) scale-up using a membrane stack configuration

Flow-electrode capacitive deionization (FCDI) is an attractive variant of CDI with distinct advantages over fixed electrode CDI including the capability for seawater desalination, high flow efficiency and easy management of the electrodes. Challenges exist however in increasing treatment capacity with this attempted here through use of a membrane stack configuration. By comparison of standardised metrics (in particular, average salt removal rate (ASRR), energy normalized removed salt (ENRS) and productivity), results show that that an FCDI system with two pairs of ion exchange membranes had the highest efficiency in desalting a brackish influent (1000 mg L−1) to potable levels (∼150 mg L−1) at higher ASRR and ENRS. Further increase in the number of membrane pairs resulted in a decrease in current efficiency, likely as a result of the dominance of electrodialysis. Results of this study provide proof of concept that (semi-)continuous desalination can be achieved in FCDI at high energy efficiency (13.8%–20.2%) and productivity (> 100 L m−2 h−1) and, importantly, provide insight into possible approaches to scaling up FCDI such that energy-efficient water desalination can be achieved.

Study of electrodialysis concentration process of inorganic acids and salts for the two-stage conversion of salts into acids utilizing bipolar electrodialysis

The electrodialysis concentration process of sodium chloride, sodium sulfate, lithium chloride, ammonium nitrate, sulfuric and nitric acids were studied. Using the model of electrodialysis concentration, the transport coefficients of the Ralex CM-PP/Ralex AMH-PP membrane pair were calculated. It has been established that for salt solutions, the key factors determining the maximum attainable electrolyte concentration in the concentration chamber are the electromigration current efficiency and the hydration number of the electrolyte. For acid solutions, the most important factors determining their concentration are the osmotic and electroosmotic transport of water through the membrane. Besides, it was found that in the process of electrodialysis concentration of acids, proton leakage occurs through the strongly basic anion-exchange membrane from the concentration chamber to the desalination chamber, which significantly reduces the current efficiency. To obtain concentrated solutions of sulfuric acid with a low content of salt ions, a two-stage scheme for the recovery of the sodium sulfate into sulfuric acid using bipolar electrodialysis (BMED) and an electrodialyzer-concentrator (EDC) is proposed. A two-stage process, including BMED and EDC, for the conversion of sodium sulfate into sulfuric acid allows one to obtain acid with a concentration of up to 1.52 M by sulfate ion with a content of sodium ions of not more than 0.005 M. At a reasonable current density of 2 A/dm2 the obtained concentration of acid was 1.16 M by sulfate ion with current efficiency of 0.89 for BMED and 0.26 for EDC, total specific energy consumption of 0.83 kWh/mol SO42-, and acid flux of 0.024 mol SO42-·dm−2·h−1 (0.23 kg H2SO4·m−2·h−1). The obtained specific characteristics of the process are comparable with the characteristics of bipolar electrodialysis using industrial bipolar membranes.

Salinity gradient power reverse electrodialysis: Cation exchange membrane design based on polypyrrole-chitosan composites for enhanced monovalent selectivity

Reverse electrodialysis (RED) is one of the most promising membrane-based processes for renewable energy generation from mixing two solutions of different salinity. However, the presence of Mg2+ in natural water has been shown to drastically reduce open circuit voltage (OCV) and output power of RED. To alleviate this challenge, commercial cation exchange membranes (CEM) supplied by Fujifilm Manufacturing Europe B.V. (The Netherlands) were chemically modified by polypyrrole (PPy)/chitosan (CS) composites under controlled Pyrrole (Py) concentration (0.025–1 M) and polymerization time (0–8 h). The modified membranes were physically characterized by FTIR, SEM and EDX along with the determination of key electrochemical properties like ion exchange capacity, ionic conductivity, monovalent selectivity and swelling degree. The monovalent selectivity (Na+ vs Mg2+) of the modified membranes, evaluated based on flux of ions by diffusion dialysis, indicated up to 3-fold improvement compared to pristine membranes inline with the enhanced OCV (up to 20%) during RED test in multi-ion solution. This was obtained without significant change in membrane and interface resistances as depicted by electrochemical impedance spectroscopy. The modified membranes displayed power densities in the range of 0.6–1.5 W/m2MP (MP: membrane pair) with more than 42% improvement compared to pristine membranes during RED test with multi-ion solutions. Although there is a gap for further improvement, these findings highlight a promising use of conducting polymers to design a highly selective and conductive membrane for RED.

Mathematical modelling and simulation analysis of electrodialysis regeneration for LiCl liquid desiccant air conditioning systems

The regeneration process is crucial to guarantee continuous dehumidification in liquid desiccant air conditioning systems. Electrodialysis (ED) is recently considered as an alternative solution to assist in regenerating liquid desiccants. This paper presents the mathematical modelling of mass transfer and electrical energy consumed by the ED stack for regenerating liquid desiccant by taking into account the effect of solution concentration and current density on the characteristics of membrane pairs. The model was validated using the data collected from the experiments. Based on which, simulations were conducted to examine how the design and operating parameters affect the regeneration performance of ED using the proposed mathematical model. It was found that the concentration increase per unit power consumption was lower with a larger effective area of one membrane pair and a larger number of membrane pairs. When the inlet concentration of the regenerated solution was below 28% (wt ⋅ wt−1), the concentration increase of the regenerated solution decreased with an elevation in the solution concentration at the inlet of the regenerated channel. When the inlet concentration of the regenerated solution was above 28% (wt ⋅ wt−1), the concentration increase of the regenerated solution elevated with an increase in the solution concentration at the inlet of the regenerated channel.

Electromechanics in vertically coupled nanomembranes

We investigate the electromechanical actuation of a pair of suspended silicon nitride membranes forming a monolithic optomechanical array. By controlling the membrane resonators' tensile stress via a piezoelectrically controlled compressive force applied to the membrane chip, we demonstrate noninvasive tuning of their mechanical mode spectrum, as well as strong intermode electromechanical coupling. Piezoelectric actuation is also shown to enhance the nonlinear response of the membranes, which is evidenced either by parametric amplification of the fundamental mode thermal fluctuations or by resonant driving of these modes into high amplitude states. Such an electro-optomechanical membrane array represents an attractive tunable and versatile platform for sensing, photonics, and optomechanics applications.

Integrated membrane distillation-reverse electrodialysis system for energy-efficient seawater desalination

Although desalination market is today dominated by Seawater Reverse Osmosis (SWRO), important technological issues remain unaddressed, specifically: relatively low water recovery factor (around 50%) and consequent huge amount of brine discharged, and energy consumption (3–5 kWh/m3) still far from the minimum thermodynamic value (∼1 kWh/m3). Herein, the energy performance of an innovative systems combining SWRO, Membrane Distillation (MD) and Reverse Electrodialysis (RED) for simultaneous production of water and energy is investigated. The valorization of hypersaline waste brine by Salinity Gradient Power production via RED and the achievement of high recovery factors (since MD is not limited by osmotic phenomena) represent a step forward to the practical implementation of Zero Liquid Discharge and low-energy desalination. The analysis is supported by lab-scale experimental tests carried out on MD and RED over a broad set of operational conditions. Among the different case studies investigated, exergetic efficiency reached 49% for the best scenario, i.e. MD feed temperature of 60 °C, MD brine concentration of 5 M NaCl, RED power density of 2.2 W/m2MP (MP: membrane pair). Compared to the benchmark flowsheet (only SWRO), up to 23% reduction in electrical energy consumption and 16.6% decrease in specific energy consumption were achieved when including a RED unit. The analysis also indicates that optimization of thermal energy input at the MD stage is critical, although it can potentially be fulfilled by low-grade waste heat or solar-thermal renewable sources. Overall, the proposed integrated system is coherent with the emergent paradigm of Circular Economy and the logic of Process Intensification.

Low-loss polarization-maintaining hollow-core anti-resonant terahertz fiber

Polarization-maintaining terahertz (THz) fibers have been considered as fundamental elements in polarization sensitive THz systems. Based on the anti-resonant waveguiding mechanism, we propose a low-loss polarization-maintaining hollow-core THz fiber with four half-elliptical cladding membranes. Numerical simulations indicate that birefringence of the fundamental mode group could be introduced by modifying the thickness of a pair of membranes while sacrificing available low-loss bandwidth. We observe that the core size, the dimension and shape of cladding membranes, have significant impacts on modal properties. For the half-circular membranes based fiber with optimized parameters, the attenuation coefficients of fundamental modes are below 10 dB m−1, the birefringence is above 10−4 and the group velocity dispersion values are lower than 60 ps THz−1 m−1 within the frequency bandwidths of 0.46–0.6 THz and 0.74–1.1 THz. At 0.9 THz, the lowest attenuation coefficient is 0.5 dB m−1 with birefringence of 1.52 × 10−4. Moreover, this THz fiber is insensitive to neither x- nor y-direction bend with a bend radius no less than 2 cm.

Design and performance simulation of microcavity enhanced bilayer graphene infrared photodetector

Photodetectors based on bilayer graphene have raised great interest for its application in infrared and terahertz detection, because bilayer graphene performs well in optical and electrical area. However, weak light absorption of bilayer graphene limits the property of bilayer graphene photodetector. In this paper a design of microcavity enhanced infrared photodetector based on Bernal stacking bilayer graphene is presented. Quantum efficiency and responsivity of detector can be valid improved by confining light in the cavity. Theoretical analysis shows that microcavity length and reflectivity of reflectors are the key factors to influence the performance. When the microcavity length matches the operating wavelength, under the standing wave effect, the quantum efficiency can reach the maximum, while reflectivity becomes the key factor. To obtain a higher and more detailed reflectivity of reflectors, distributed bragger reflectors (DBRs) are chosen as reflectors of microcavity. Reflectivity is determined through the analysis of electromagnetic field distribution of membrane. The reflectivity of reflectors is calculated by transfer matrix. AlAs/Al0.1Ga0.9As and TiO2/SiO2 membranes are chosen as constituents of reflectors. The structure is confirmed through optimization, and the result is presented below: The microcavity length is 467.4 nm, 13/10 pairs of membranes constructs the top/bottom reflector and the bilayer graphene is located in the middle of microcavity. At a nominal operating wavelength of 1.55 μm, a widely used wavelength in laser range finder, the quantum efficiency can reach 99.33% and the responsivity can reach 1.24 A/W. The method provides a possible approach to fabricate high quantum efficiency bilayer graphene photodetector.

Electrodialysis of aqueous NaCl-glycerol solutions: A phenomenological comparison of various ion exchange membranes

Industrial processes such as e.g. oil, fat and resin production and saponification generate large volumes of aqueous NaCl-glycerol containing streams. With typical glycerol concentrations ranging from 5 to 15 % (m/m) and a high salt content, these streams pose a challenge to further processing, both to end-of-pipe treatment as to possible reuse scenarios for organic components and/or salts. Electrodialysis is evaluated as an alternative technology to remove salt from these streams. Salt, glycerol and water transport is studied experimentally through desalination of synthetic solutions for 7 commercial ion exchange membrane pairs, Fumatech (FAB-FKB, FAM-FKM, FAS-FKS), Neosepta (AMX-CMX), PCA (MVA-MVK, SA-MV) and Ralex (AMH-CMH). A phenomenological model is applied i.e. model coefficients are derived from test data through regression analysis to evaluate transport phenomena. Salt transport is found to be related to electromigration only and the NaCl transference number is determined to be highest in AMH-CMH (0.96 ± 0.04) and FKS-FAS (1.01 ± 0.03). Limiting current density is highest for FKS-FAS and lowest for FAM-FKM. Water transport is attributed to electroosmosis and osmosis. Water transference numbers found are similar to those in literature (tW ∼ 7–10). The value of the osmotic coefficients (Pw) differs strongly among the different membrane pairs and is highest for MV-SA Q380 (0.99 × 10−5 ms−1). Glycerol transport is attributed to diffusion and water flux induced cotransport. The diffusion of glycerol differs significantly among all membrane pairs (range 2.06 × 10−8 ms−1 FAB-FKB to 12.4 × 10−8 ms−1 MV-SA). Reflection coefficients differ significantly among membrane pairs but fall within a relative narrow range (0.36–0.75 ms−1). Numerical simulation of batch desalination with the derived transport model identifies current density as the largest contribution to the overall glycerol transport (38%−64%) followed by osmotic co-transport (16%−41%) and glycerol diffusion (9%−28%). A low glycerol/NaCl flux is desirable, this occurs when both initial glycerol/NaCl and NaCl concentrations are low while current density is high.

Fate and removal of trace pollutants from an anion exchange spent brine during the recovery process of natural organic matter and salts

The results of this sampling campaign on pilot scale processes aim to evaluate the occurrence and behavior of trace organic micro-pollutants and metal elements during anion exchange treatment of surface water and the subsequent treatment of generated spent brine with two types of electrodialysis membrane pairs. This knowledge is relevant to assess the quality and reusability of secondary products created during brine treatment; specifically the excess of sodium chloride to be recycled onsite and the natural organic matter, mostly consisting of humic substances, which find multiple applications in the agricultural industry. This study highlights that (1) the attachment mechanism of organic micro-pollutants to anion exchange resin occurs through electrostatic interaction and the subsequent transfer through ion exchange membranes is restricted by size exclusion; and (2) the complexation of trace metals compounds with the natural organic matter partly explains their removal by anion exchange. Complexes remain stable during treatment of the brine with electrodialysis.

Composite inorganic anion exchange membrane for electrodialytic desalination of milky whey

Composite membranes have been obtained by modification of macroporous ceramics with hydrated zirconium dioxide and basic bismuth nitrate. The modification technique provided formation of the two-component modifier directly in macropores of the inorganic matrix. This method allows us to obtain the material, which possesses by optimal combination of charge selectivity and electrical conductivity, by means of one-time modification. It is assumed that nanoparticles of basic bismuth nitrate (5 nm) block pores between larger particles of hydrated zirconium dioxide (several tens of nanometers) providing semipermeability of the membranes towards anions in acidic media: potentiometric transport number of counter-ions (Cl-) reaches 0.9. Electrodialytic desalination of milky whey has been carried out using a pair of polymer cation exchange (Nafion 117) and composite inorganic membranes. The possibility of whey desalination under overlimiting current has been shown. The current efficiency due to anions reaches 80% under these conditions. Electrodialysis of whey allows us to remove 75 % of the mineral components in 3 h, the same purification degree is achieved in 30 min for nanofiltration permeate.

Performance investigation and optimisation of electrodialysis regeneration for LiCl liquid desiccant cooling systems

In this paper, the regeneration performance of membrane electrodialysis (ED) with three different types of ion-exchange membrane pairs working with LiCl liquid desiccant solutions was first experimentally investigated. The membrane pair with the optimal performance for concentrating desiccant solutions was then identified and selected to quantitatively examine the effect of the operating parameters of ED on salt and water mass transfer, the concentration of the transferred solution and energy consumption of the ED stack using Taguchi method and analysis of variance. An optimisation was also performed to determine the optimal levels of the operating factors. The results showed the supplied current density significantly influenced the energy consumption of the ED stack but had a limited impact on the concentration of the transferred solution. Under the predicted optimal operating conditions, the energy consumption can be saved by 31.7% while the concentration of the transferred solution increased by 9.4% in comparison to the average values in the studied range. The main findings can be potentially used to guide optimal design and operation of ED regeneration for LiCl liquid desiccant cooling systems.