Membrane Electrodialysis Research Articles

Lithium Extraction by Electrodialysis: Effect of Co-Occurring Ions for Application in Brine Processing

Abstract Lithium (Li) is considered a critical material because of growing Li-ion battery demand and 90% of global production occurring in Australia, Chile, and China. Li-ion (Li+) extraction from brine uses large areas for evaporation and precipitation. Membrane separation can extract lithium with minimal water losses. However, the effect of brine composition on Li+ transport across different commercial membranes in electrodialysis (ED) separations remains a pressing knowledge gap. This study aimed to evaluate co-occurring ion effects (Na+, Mg2+, Ca2+) on ED Li+ extraction using different commercial membranes. Li+ extraction performance was evaluated for varying current densities in binary solutions using a single-stack ED cell comprised of a standard anion exchange membrane and either a standard cation exchange (CEM), monovalent-selective CEM, or nanofiltration (NF) membrane. Li+ selectivities were highest for the monovalent-selective CEM, followed by NF and then standard CEM. Monovalent contaminants remain an extant challenge for Li+ extraction using all membranes tested. Selectivity factors for Li+ over divalent reached 6.8 (SLi/Mg) and 56.7 (SLi/Ca) at 2.8 mA/cm² for the monovalent-selective CEM. These divalent separation factors were achieved without Ca precipitation/fouling; Li+/Mg2+ and Li+/Ca2+ ratios increased from 0.5 in the feed (for both ions) to 5.0 and 3.5 in the permeate.

Comparing Advanced Bipolar Membranes for High-Current Electrodialysis and Membrane Electrolysis

Comparing Advanced Bipolar Membranes for High-Current Electrodialysis and Membrane Electrolysis

Boosting lithium/magnesium separation performance of selective electrodialysis membranes regulated by enamine reaction

Monovalent cation exchange membranes (MCEMs) have progressively played an important role in the field of ion separation. However, according to transition state theory (TST), synchronously tuning the enthalpy barrier (△H) and entropy barrier (△S) for cation transport to improve ion separation performance is challenging. Here, the enamine reaction between the -NH- and -CHO groups is applied to regulate the subsequent Schiff-base reaction between the -CHO and -NH2 groups, which reduces the positive charges of the selective layer but increases the steric hindrance. The increased -T△S (△S term) for cation transport plays an important role in improving Li+/Mg2+ separation performance. The optimal positively-charged glutaraldehyde@piperazine/polyethyleneimine assembled membrane (M-Glu@PIP/PEI) has a perm-selectivity (Li+/Mg2+) of 31.83 with a Li+ flux of 1.87 mol·m-2·h-1, surpassing the Li+/Mg2+ separation performance of state-of-the-art monovalent ion selective membranes (MISMs). Most importantly, the selective electrodialysis (S-ED) process with M-Glu@PIP/PEI can be directly applied to treat simulated salt-lake brines (SLBs), and its superior Li+/Mg2+ separation performance and operational stability enables 74.44 % of the lithium resources with a Li+ purity of 34.02 % to be recovered. This study presents new insights into the design of high-performance MCEMs for energy-efficient resource recovery.

Graphene oxide‐based nanofluidic membranes for reverse electrodialysis that generate electricity from salinity gradients

AbstractA widely employed energy technology, known as reverse electrodialysis (RED), holds the promise of delivering clean and renewable electricity from water. This technology involves the interaction of two or more bodies of water with varying concentrations of salt ions. The movement of these ions across a membrane generates electricity. However, the efficiency of these systems faces a challenge due to membrane performance degradation over time, often caused by channel blockages. One potential solution to enhance system efficiency is the use of nanofluidic membranes. These specialized membranes offer high ion exchange capacity, abundant ion sources, and customizable channels with varying sizes and properties. Graphene oxide (GO)‐based membranes have emerged as particularly promising candidates in this regard, garnering significant attention in recent literature. This work provides a comprehensive overview of the literature surrounding GO membranes and their applications in RED systems. It also highlights recent advancements in the utilization of GO membranes within these systems. Finally, it explores the potential of these membranes to play a pivotal role in electricity generation within RED systems.

Dibenzodioxin-Based Polymers of Intrinsic Microporosity with Enhanced Transport Properties for Lithium Ions in Aqueous Media.

Boosting the transport and selectivity properties of membranes based on polymers of intrinsic microporosity (PIMs) toward one specific working analyte of interest is challenging. In this work, a novel family of PIM membranes, prepared by casting and exhibiting optima mechanical properties and high thermal stability, was synthesized from 4,4'-(2,2,2-trifluoro-1-phenylethane-1,1-diyl) bis(benzene-1,2-diol) and two tetrafluoro-nitrile derivatives. Gas permeability measurements evidenced a CO2/CH4 selectivity up to 170% relative to the reference polymer, PIM-1, in agreement with their calculated fractional free volume and the analysis of the textural properties by N2 and CO2 gas adsorption. Besides, the chemical modification by acid hydrolysis of the PIM membranes favored the permeability for lithium ions (LiCl 2M, 6 × 10-9 cm2·s-1) compared to other alkali metal analogs such as sodium (NaCl 2M, 7.38 × 10-10 cm2·s-1) and potassium (KCl 2M, 1.05 × 10-9 cm2·s-1). Moreover, the complete mitigation of the crossover of redox species with higher molecular sizes than the ions from alkali metal salts was confirmed by using in-line benchtop NMR methods. Additionally, the modified PIM membranes were measured in a symmetric electrochemical flow cell using an aqueous electrolyte by combining lithium ferro/ferricyanide redox compounds and lithium chloride. The electrochemical tests showed low polarization, high-rate capability, and capacity retention values of 99% when cycled at 10 mA·cm-2 for over 50 cycles. Based on these results, these polymers could be used as highly selective and conducting membranes in electrodialysis for lithium separation and lithium-based redox flow batteries and as a protective layer in high-energy density lithium metal batteries.

High-Performance Crown Ether-Modified Membranes for Selective Lithium Recovery from High Na+ and Mg2+ Brines Using Electrodialysis

The challenge of efficiently extracting Li+ from brines with high Na+ or Mg2+ concentrations has led to extensive research on developing highly selective separation membranes for electrodialysis. Various studies have demonstrated that nanofiltration membranes or adsorbents modified with crown ethers (CEs) such as 2-OH-12-crown-4-ether (12CE), 2-OH-18-crown-6-ether (18CE), and 2-OH-15-crown-5-ether (15CE) show selectivity for Li+ in brines. This study aims to develop high-performance cation exchange membranes (CEMs) using CEs to enhance Li+ selectivity and to compare the performance of various CE-modified membranes for selective electrodialysis. The novel CEM (CR671) was modified with 12CE, 18CE, and 15CE to identify the optimal CE for efficient Li+ recovery during brine electrodialysis. The modification process included polydopamine (PDA) treatment and the deposition of polyethyleneimine (PEI) complexes with the different CEs via hydrogen bonding. Interfacial polymerization with 1,3,5-benzenetricarbonyl trichloride-crosslinked PEI was used to create specific channels for Li+ transport within the modified membranes (12CE/CR671, 15CE/CR671, and 18CE/CR671). The successful application of CE coatings and Li+ selectivity of the modified membranes were verified through Fourier-transform infrared spectroscopy, zeta-potential measurements, and electrochemical impedance spectroscopy. Bench-scale electrodialysis tests showed significant improvements in permselectivity and Li+ flux for all three modified membranes. In brines with high Na+ and Mg2+ concentrations, the 15CE/CR671 membrane demonstrated more significant improvements in permselectivity compared to the 12CE/CR671 (3.3-fold and 1.7-fold) and the 18CE/CR671 (2.4-fold and 2.6-fold) membranes at current densities of 2.3 mA/cm2 and 2.2 mA/cm2, respectively. At higher current densities of 14.7 mA/cm2 in Mg2+-rich brine and 15.9 mA/cm2 in Na+-rich brine, the 15CE/CR671 membrane showed greater improvements in Li+ flux, approximately 2.1-fold and 2.3-fold, and 3.2-fold and 3.4-fold compared to the 12CE/CR671 and 18CE/CR671 membranes. This study underscores the superior performance of 15CE-modified membranes for efficient Li+ recovery with low energy demand and offers valuable insights for advancing electrodialysis processes in challenging brine environments.

A comparative study on the influences of sulfonated- and phosphorated-graphene oxide on polyvinylidene fluoride cation-exchange membranes for electrodialysis

The –SO3H and –PO3H2 groups were grafted on graphene oxide (GO) by adding sulfuric acid and phosphoric acid at the same weight percentage, respectively. The physicochemical properties of the sulfonated GO (SGO) and phosphorated GO (PGO) were compared using different techniques. SGO and PGO were individually incorporated into the PVDF matrix (at the same wt%) to compare their effects on the properties of the resulting PVDF/SGO and PVDF/PGO cation-exchange membranes (CEMs). Membranes' characteristics including ionic conductivity and water content, area resistance, and the rate at which Na+ ions diffuse throughout the membranes changed considerably by altering the type of ion exchange sites, and more desirable values were obtained using PGO. Nevertheless, PVDF/SGO provided an ion exchange capacity (IEC) of 5.5 meq g−1, while it was about 1.7 times lower than PVDF/PGO (9.4 meq g−1). It also provided a promising ionic conductivity (17.24 mS cm−1), transport number (93.65 %), permselectivity (89.58 %), and low area resistance (2.7 Ω cm2), which exceeded those of the commercial CEMs such as Ralex. Moreover, PVDF/SGO exhibited desirable mechanical characteristics, and a low weight loss (2.4 %) and low resistance change (22.2 %) after 9 h being submerged in the Fenton reagent, however, these parameters were better for PVDF/PGO.

Nucleobase-mediated hydrogen bonding crosslinked highly sulfonated poly(ether ether ketone) electrodialysis membranes for efficient waste acid recovery

Electrodialysis is a promising technology for waste acid recovery with the advantages of low energy consumption and high efficiency. In this work, two nucleobase-modified highly sulfonated poly(ether ether ketone) with adenine (SPEEK-50A) and thymine (SPEEK-50T) were successfully synthesized. Then, a series of blending SPEEK-50Ax/50Ty membranes with varying molar ratios of these two functionalized SPEEKs were fabricated by solution casting. The hydrogen bonding crosslinked structure of ‘A-T base pairs’, as well as the acid-base interactions between the incorporated nucleobases and SO3H groups of the polymer backbone, not only enhanced the mechanical properties and thermal stability of the blending membranes, but more importantly, it successfully addressed the over-swelling issue of highly sulfonated SPEEK membrane. The SPEEK-50Ax/50Ty membranes exhibited tensile strengths between 59.3 and 72.3 MPa, which is 2.2–2.6 times that of the pristine SPEEK membrane. And the water uptake of the blending membranes reduced from 116 % to 14.6–19.2 %, while the swelling ratio decreased from 27.1 % to 5.86–6.60 %. The proton affinity of the multiple basic N atoms in nucleobases, as well as the ‘A-T base pairs’ hydrogen bonding network and acid-base interactions between nucleobases and SO3H groups, all can serve as effective proton transport channels. Additionally, the charge repulsion effect of protonated nucleobases and the crosslinking structure is beneficial to the permselectivity. Therefore, the fabricated blending SPEEK-50Ax/50Ty membranes exhibited superior H+ flux (1.66–1.73 mmol m−2 s−1) and enhanced H+/Fe2+ permselectivity (40.3–43.2). The SPEEK-50A0.5/50T0.5 membrane demonstrated a H+ flux of 1.70 mmol m−2 s−1 and a H+/Fe2+ permselectivity of 43.2, which is 2.8 times that of the pristine SPEEK membrane, surpassing both commercially available and recently reported membranes. Therefore, the nucleobase-modified blending SPEEK-50Ax/50Ty membranes might be potential candidates for the efficient recovery of acid from pickling wastewater.

Enhancing chloride/fluoride selectivity with hydrophobic side-chain anion exchange membranes in electrodialysis

The selective separation of chloride ions (Cl−) from fluoride ions (F−) is a critical concern in various industries due to the potential risks of F− on public health and industrial operations. However, Cl−/F− separation is known to be technologically challenging, considering they have the same charge and valency. This study explores the design of anion exchange membranes (AEMs) in electrodialysis to achieve Cl−/F− separation based on the difference in their hydration energy. Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) polymers brominated at varying reaction temperatures were employed as the basic AEM material, enabling fine-tuning of the hydrophobic properties of the resulting membranes through selective bromination at the benzyl or aryl positions and the subsequent quaternization with tertiary amines of different chain lengths, ultimately enhancing their selectivity. The developed AEMs are tested in electrodialysis involving a binary Cl−/F− mixture. The obtained membranes exhibited remarkable selectivity, reaching as high as 12.5 ± 1.0, surpassing the performance of commercial monovalent selective AEMs. The results demonstrate the potential of Cl−/F− separation by electrodialysis and highlight the significance of tailored membrane design in achieving the separation of ions with the same valency.

Enhancing anti-biofouling activity in electrodialysis by spraying GO@Ag nanosheets on anion exchange membranes

To mitigate biofouling and maintain the properties of the anion exchange membranes (AEMs) in electrodialysis (ED) processes, conferring specialized functional coatings onto surfaces has proven effective in reducing susceptibility to biofouling. In this research, AEM substrates were synthesized using the conventional chemical assembly method, involving the reaction of 1-butylimidazole (BIm) with commercially available bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO). Subsequently, a synergistic anti-biofouling system comprising graphene oxide (GO) and Ag nanoparticles (NPs) co-mingled casting-solution was formulated into a 2-μm coating through spraying onto the AEM surface. Exceptional static antibacterial activity of this system towards prevalent Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria due to contact killing mechanisms. The dynamic anti-biofilm capability of post-electrodialysis AEM was evaluated using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM), revealing consistent efficacy. Notably, the enhancement of anti-biofouling properties was achieved without compromising separation efficiency, as the coating solution shares the same composition as the substrate membrane. Crucially, the co-sprayed coating technique on the AEM surface overcomes the conventional “trade-off phenomenon” between performance and stability. This approach to fabricating anti-biofouling AEMs is believed to provide valuable insights for further optimization and application, thereby facilitating their deployment in water treatment and related fields.

Integrated membrane process of tubular ultrafiltration-nanofiltration-electrodialysis-reverse osmosis for treating fracturing flowback fluid

As an underground source of natural gas, shale gas is important for ensuring national energy security and promoting the “dual carbon” target. However, shale gas extraction produces flowback fluid that requires efficient treatment to avoid negative impacts on the environment and human health. In this study, a pilot plant was constructed to implement a novel membrane-integrated process to treat fracturing flowback fluid. This process employs an aeration reaction sedimentation (ARS) tank and a tubular ultrafiltration (TUF) membrane for pretreatment, followed by three separate membranes for nanofiltration (NF), electrodialysis (ED), and reverse osmosis (RO). The pretreatment removed 99.3% of total hardness, 99.4% of total suspended solids (TSS), and 88.1% of total organic carbon (TOC). Four different types of TUF membranes were tested and compared. It was also found that physico-chemical cleaning of the TUF membrane using the ceramic particle technology resulted in a flux recovery rate of up to 98%. In addition, the NF and ED membranes can remove 99.4% of Na2SO4 and 90% of NaCl, respectively, resulting in an 85.6% decrease in TSS. Water recovery rate of the total system can reach 90%. Based on concept of sustainable green development, carbon footprint of integrated membrane process for treating fracturing flowback fluid was approximately 86.7 kgCO2 eq lower than that of traditional process. Low carbon emissions and no generation of secondary pollutants have become the keys to treat fracturing wastewater. In summary, the integrated TUF-NF-ED-RO process based on membranes is very promising for treating fracturing flowback fluid.

The role of ionic concentration polarization on the behavior of nanofluidic membranes

Water, the elixir of life, faces a pressing challenge—salinity. As humanity's demand for freshwater intensifies, the significance of efficient desalination processes becomes paramount. The promising prospects of nanofluidic membranes and unique electrokinetic phenomena like ion concentration polarization (ICP) signal optimistic strides in enhancing salt removal processes. This study is dedicated to elucidating the transport mechanism of buffer ions at interfaces between micro and nanochannels. To achieve this, we introduce a multiphysics coupling model that incorporates a boundary condition for the fixed surface voltage, offering a comprehensive description of the impact of nanochannel arrays. In this context, it is important to note that the nanochannel array is characterized by a positive charge density, akin to a cation exchange membrane (CEM), seamlessly integrated into the microchannel wall to serve as a cationic half-cell. The analysis involved solving governing equations, including the Poisson-Nernst-Planck, continuity, and Navier-Stokes equations, numerically using the finite element method in an unsteady state. Employing cylindrical nanochannel array configurations—single, dual, and triple—we scrutinized their impact on salt species concentration and removal efficiency under specified conditions (c0=1mM, ρv=2C/m3, LN=10μm, VT=26mV, Vsurr=4VT, VL/VR=8,t≥0.5 and ζ=−60mV). The single nanochannel array configuration demonstrated a relatively uniform salt distribution, achieving a removal efficiency of approximately 58%. The introduction of two nanochannel arrays at distinct locations resulted in a notable increase in removal efficiency, reaching 72%, particularly in the "down first" configuration, emphasizing a synergistic effect. The presence of three nanochannel arrays, each with varying lengths, produced intricate patterns, with the highest removal efficiency observed at 91% in the "different length" condition. This study emphasizes the superior desalination capabilities achievable through multiple nanochannel arrays, advancing our understanding of nanofluidic membrane applications for efficient water desalination. In conclusion, emulating electrodialysis membrane procedures, particularly by integrating an anionic half-cell, holds promise for further advancing desalination processes, offering a potential avenue to enhance efficiency.

Characterization and Performance Evaluation of Digital Light Processing 3D Printed Functional Anion Exchange Membranes in Electrodialysis

With the rapid development of 3D printing technologies, more attention has been focused on using 3D printing for the fabrication of membranes. This study investigated the application of digital light processing (DLP) 3D printing combined with quaternization processes to develop dense anion exchange membranes (AEMs) for electrodialysis (ED) separation of Cl− and SO42− ions. It was discovered that at optimal curing times of 40 min, the membrane pore density was significantly enhanced and the surface roughness was reduced, and this resulted in an elevation of desalination rates (97.5–98.7%) and concentration rates (165.8–174.1%) of the ED process. Furthermore, increasing the number of printed layers improved the membranes’ overall polymerization and performance, with double-layer printing showing superior ion flux. This study also highlights the impact of the polyethylene glycol diacrylate (PEGDA) molecular weight on membrane efficacy, where PEGDA-700 outperformed PEGDA-400 in ion transport capabilities and desalination efficiency. Additionally, higher 4-vinylbenzyl chloride (VBC) content improved the quaternary ammonium group concentration and membrane conductivity, and hence elevated the ED performance. Under optimized conditions, DLP 3D printed membranes demonstrated exceptional selectivity of 24.0 for Cl−/SO42− and a selective purity of 81.4%. With a current density of 400 A/m2, the current efficiency and energy consumption were in the range of 82.4% to 99.7%, and 17.2 to 25.4 kW‧h‧kg−1, respectively, showcasing the potential of advanced manufacturing techniques in creating efficient and functional ion exchange membranes.

MAGNEX and PILCCU in Finland: deployment of CO2 mineralisation in circular economies

Two ongoing projects in Finland, MAGNEX (Viable magnesium ecosystem: exploiting Mg from magnesium silicates with carbon capture and utilization) and PILCCU (Piloting of ÅA CCU) aim at using CO2 mineralisation technology for the overlapping purposes of large-scale CO2 emissions mitigation and bringing several valuable material streams into circular economies, including construction. Of central importance are magnesium-based materials, such as magnesium carbonate hydrate (MCH), besides (amorphous) silica and several metallic species. On top of revenues from these, CO2 emissions mitigation lowers the financial penalty from CO2 emission rights under for example the European ETS. The ÅA process routes are stepwise processes based on extraction of magnesium (and other species) from serpentinite-containing mining tailings from Finland, followed by precipitation of metallic species, carbonation using a CO2 containing gas-stream (no separate capture step needed) and recovery of solvent salt, respectively. Several separation steps involve (ion-selective) membrane electrodialysis. Besides ongoing mapping and characterisation of Finnish rock resources as tailings or other side-streams at metal and mineral mines in Finland, the projects address public acceptance, legislation and other non-technical issues related to large-scale roll-out of this type of CCU technology.For the use of the solids, magnesium-based cement binders and plaster-like recipes are investigated as well as applications for the (amorphous) silica and other residues, including the use of MCH for cyclic thermal energy storage (TES). Special focus is on accelerating the carbonation step and the final outcome of MCH production, considering pressure (including supercritical CO2 levels), and the role of recoverable catalysts and other additives. The work receives funding from the Academy of Finland (2022-2025) and from Business Finland plus industry partners (2022-2024), respectively.

Construction of integrated model of bipolar membrane electrodialysis membrane process and gas absorption-ion reaction process

The bipolar membrane electrodialysis (BMED) possesses the capability of green and efficient recovery of salt resources and alkali production, making it suitable for coupling with seawater utilization and CO2 absorption-mineralization processes. In order to reveal the process control mechanism and dynamic equilibrium, the imperative arises to construct a transport-reaction differential model. The overall process is subdivided into distinct modules: mass transport, reaction, electrical, and tank, with the aim of streamlining this intricate coupling procedure. Based on the Nernst-Planck model and combined with semi-empirical models, the models for each module were constructed, and differential equations were used for model integration. This approach addresses the complexity of multiphase reactions and mass transport processes that are challenging to describe through mathematical models. This model can predict indicators such as decalcification rate, carbon fixation rate, and energy consumption, and the accuracy of these results under various conditions was thoroughly verified through experimental data. This study is expected to provide guidance for the modeling of membrane process coupling.

Electrodialysis membrane desalination with diagonal membrane spacers: a review.

Electrodialysis desalination uses ion exchange membranes, membrane spacers, and conductors to remove salt from water. Membrane spacers, made of polymeric strands, reduce concentration polarization. These spacers have properties such as porosity and filament shape that affect their performance. One important property is the spacer-bulk attack angle. This study systematically reviews the characteristics of a 45° attack angle of spacers and its effects on concentration polarization and fluid dynamics. Membrane spacers in a channel create distinct flow fields and concentration profiles. When set at a 45° attack angle, spacers provide greater turbulence and mass-heat transfer than traditional spacers. This is because both the transverse and longitudinal filaments become diagonal in relation to the bulk flow direction. A lower attack angle (<45°) results in a lower pressure drop coupled with a decline in wakes and stream disruption because when the filaments are more parallel to the primary fluid direction, the poorer their affect. This research concludes that membrane spacers with a 45° spacer-bulk attack angle function optimally compared to other angles.

High monovalent/divalent permselectivity and low ionic resistance of ionene-based anion exchange membranes in electrodialysis

This study presents an investigation on the monovalent/divalent ion permselectivity of anion exchange ionenes, a distinct class of solid polymer polyelectrolytes having cationic fixed charge groups located directly on the polymer backbone, rather than being pendant. These ionenes are commercially available as Aemion® AEMs and are based on hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI). Monovalent/divalent permselectivity values of four Aemion® membranes of different thickness and ion exchange capacity were determined via electrodialysis in a mixed electrolyte system comprising chloride/sulfate anions. To fully understand the transport phenomena in these materials, ion transport properties were studied in conjunction with water uptake and ionic conductance. When the AEMs were exposed to mixed chloride/sulfate solutions, their water uptake significantly increased compared to purely chloride containing solutions, and the concentration of fixed charge groups in the AEMs consequently decreased. We find that thicker ionenes with lower IEC exhibit the highest permselectivity. The data also reveal that thinner AEMs yield a greater ionic flux loss and decreased permselectivity values, particularly in case of lower IEC AEMs. Surprisingly, despite its low water uptake and high resistance, commercial Selemion AMV possesses lower permselectivity than low IEC ionene-based Aemion® AEMs, which we explain on the basis of the highly tortuous internal morphology of low water content ionenes. Permselectivity-to-resistance ratio values are an order of magnitude higher for low IEC ionenes when compared with high IEC ionenes and Selemion AMV.

Electrodialysis membrane desalination for water and wastewater processing: irregular attack angles of membrane spacers.

Electrodialysis desalination is constructed with a number of anion exchange membranes (AEM), cation exchange membranes (CEM), anode, cathode, adjacent silicon gasket integrated membrane spacers, and inlet/outlet holes per cell. At the boundary among an ionic solution and an ion exchange membrane, concentration polarization develops. Spacers placed in between channel's walls function as stream baffles to increase turbulence, improve heat and mass transfer, diminish the laminar boundary layer, and lessen fouling problems. The current study offers a systematic review of membrane spacers, spacer-bulk attack angles, and irregular attack angles. Spacer-bulk attack angle is accountable for variations in the pattern and direction of stream which impact heat-mass transfer and concentration polarization. Irregular attack angles (e.g., 0°, 15°, 30°, 37°, 45°, 55°, 60°, 62°, 70°, 74°, 80°, 90°, 110°, 120°) in the present study were found to provide unique stream patterns due to the spacer's filaments being less or more transverse in respect to the primary solution direction, which may significantly alter heat transfer, mass transport, pressure drop, and overall flow dynamics. Spacer applies shear stress resulting by continuous stream tangent to the membrane exterior, which lessens polarization. In the end, 45° is concluded as the preferred attack angle that offers balanced rates of heat transfer, mass transport, and pressure drop throughout the feed channel while greatly lowering the rate of concentration polarization.

Electrodialysis Membrane Technology applied to MEG reclamation – a case study

At Beach Energy’s Otway Gas Plant (OGP) the mono-ethylene glycol (MEG) system salt concentration increased significantly following the commissioning of new subsea horizontally completed wells. Therefore, to de-risk future developments, which are anticipated to include similar wells, a salt removal strategy was implemented. The use of MEG for gas hydrate suppression in wet-raw gas subsea or onshore production pipelines is common across the oil and gas industry, with the MEG recycled using well-proven regeneration and/or reclamation technologies. The MEG extracts water that can contain residual salt and minerals, which over time accumulate in the MEG and can lead to several operational issues, including severe fouling in the MEG regeneration plant, production line blockages and production pipeline integrity concerns, such as accelerated corrosion. MEG reclamation is used to minimise salt accumulation and to date, the dominant technologies employed have been vacuum distillation or flash vaporisation. However, since early 2022, electrodialysis (ED) membrane technology has been deployed at the OGP in an effort to find a more cost-effective solution. The technology is proving a viable alternative to a traditional vacuum distillation reclaiming–regeneration process with energy savings of 17–28% for a hybrid ED-Regeneration process with significantly lower capital cost. This paper details the technical and operational challenges overcome to implement the ED reclamation technology in an industry with more stringent regulatory requirements when compared to typical ED applications (e.g. within the water treatment, pharmaceutical, and food and beverage industries), as well as present the main system performance outcomes following 6 months of operation.

Mechanism of selective transportation of metal ions across chelating membranes in electrodialysis

The presented research explains the mechanism of selective transportation mass in electrodialysis by chelating membrane according to the electrosorption and specific diffusivity. The Nernst-Planck equation was applied for modelling and defining the character of mass transportation. The chelating membrane is developed by the chemical grafting of hydroxyquinoline (HQ), which guarantees selectivity. The investigation of mass transportation was determined using a single-component solution of transition metal cations like Co2+, Mn2+and Ni2+, as well as from alkaline metal classes like Li+ and Mg2+. Finally, the multi-component solutions were tested to confirm the chelating membrane's specific character and mass transportation mechanism. The chemical and electrochemical investigations like FTIR and EIS confirmed the appearance of the chelating reactions between membrane and cobalt cations only. According to the creation of aqua complexes of HQ and Co2+, the PAN-5C8Q membrane could transport in a significant majority only Co2+ against other mono- and divalent cations. The transport number against the Mn2+, Ni2+, Mg2+ and Li+ for Co2+got over 0.6.