• Korean Journal of Materials Research
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• v.33 no.2
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• pp.71-76
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• 2023

The electroconvection generated on the surface of an ion exchange membrane (IEM) is closely related to the electrical/chemical characteristics or topology of the IEM. In particular, when non-conductive regions are mixed on the surface of the IEM, it can have a great influence on the transfer of ions and the formation of nonlinear electroconvective vortices, so more theoretical and experimental studies are necessary. Here, we present a novel method for creating microscale non-conductive patterns on the IEM surface by laser ablation, and successfully visualize microscale vortices on the surface modified IEM. Microscale (~300 ㎛) patterns were fabricated by applying UV nanosecond laser processing to the non-conductive film, and were transferred to the surface of the IEM. In addition, UV nanosecond laser process parameters were investigated for obvious micro-pattern production, and operating conditions were optimized, such as minimizing the heat-affected zone. Through this study, we found that non-conductive patterns on the IEM surface could affect the generation and growth of electroconvective vortices. The experimental results provided in our study are expected to be a good reference for research related to the surface modification of IEMs, and are expected to be helpful for new engineering applications of electroconvective vortices using a non-conductive patterned IEM.

• Membrane Journal
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• v.32 no.4
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• pp.209-217
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• 2022

Ion exchange membrane (IEM) is an important class of membrane applied in batteries, fuel cells, chloride-alkali processes, etc to separate various mono and multivalent ions. The membrane process is based on the electrically driven force, green separation method, which is an emerging area in desalination of seawater and water treatment. Electrodialysis (ED) is a technique in which cations and anions move selectively along the IEM. Anion exchange membrane (AEM) is one of the important components of the ED process which is critical to enhancing the process efficiency. The introduction of cross-linking in the IEM improves the ion-selective separation performance due to the reduction of free volume. During the desalination of seawater by reverse osmosis (RO) process, there is a lot of dissolved salt present in the concentrate of RO. So, the ED process consisting of a monovalent cation-selective membrane reduces fouling and improves membrane flux. This review is divided into three sections such as electrodialysis (ED), anion exchange membrane (AEM), and cation exchange membrane (CEM).

• Membrane and Water Treatment
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• v.14 no.2
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• pp.55-63
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• 2023

In this study, the influence of different IEMs (ion exchange membranes) to performance of the hypochlorite electrolysis unit with Cl₂ recovery stream was investigated. More specifically, Nafion 117-a representative cation exchange membrane (CEM)-and aminated polypheylene oxide (APPO)-an anion exchange membrane (AEM)-were installed in the hypochlorite electrolysis unit, and the performance and the energy efficiency of the units were evaluated and compared. Regardless of whether CEM (Nafion 117) or AEM (APPO) was installed, the rate of hypochlorite generation was increased (by up to 24.3% and 22.2% for Nafion 117 and APPO, respectively) compared with the unit without an IEM. On the other hand, the power efficiency and the optimum operation condition of hypochlorite production units seem to depend on the conductivity and stability of the installed IEM. As the result, between Nafion 117 and APPO, higher performance and efficiency were achieved with Nafion 117, due to excellent conductivity and stability of the membrane.

• Membrane Journal
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• v.26 no.3
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• pp.229-237
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• 2016

We prepared heterogeneous ion exchange membranes (hetero-IEMs) for the application of membrane capacitive deionization (MCDI). Hetero-IEMs were fabricated by compressing the mixture of ion exchange resin powders and liner low density polyethylene (LLDPE). Characterization and MCDI desalination experiments were carried for the fabricated membranes. Electrical resistance of membrane decreased and water content increased with increasing the resin content in the hetero-IEMs. However, transport number indicating permselectivity of membrane was similar with that of commercial homogenesous ion exchange membrane. The results of MCDI desalination experiments showed that the adsorption amount for hetero-IEM was about 90% of that of homogeneous membrane due to the high electrical resistance of hetero-IEM. Although desalination performance of hetero-IEM decreased compared with homogeneous membrane, it was thought to be applicable to MCDI because of simple preparation and low price.

• Membrane Journal
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• v.32 no.6
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• pp.401-410
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• 2022

Demand for lithium hydroxide (LiOH) is annually increasing due to its efficiency and safety for the environment in comparison to its current alternatives. Lithium can be found in different salty and brine lakes which later synthesized to produce LiOH for various applications. Different methods are used to separate and recover lithium ions, the most common of which is electrodialysis (ED). ED is a membrane-based separation technique which works on potential difference of its layers as a driving force to push ions from one side to another. The ion exchange membrane (IEM) in ED makes the process efficient because of the perm selectivity of different ions vary depending on their hydrodynamic volume. In this review, the different alteration strategies of both ED and IEM, to enhance the recovery of lithium ions are discussed.

• Membrane Journal
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• v.33 no.5
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• pp.257-268
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• 2023

Membrane capacitive deionization (MCDI) is a variation of the conventional CDI process that can improve desalination efficiency by employing an ion-exchange membrane (IEM) together with a porous carbon electrode. The IEM is a key component that greatly affects the performance of MCDI. In this study, we attempted to derive the optimal fabricating factors for IEMs that can significantly improve the desalination efficiency of MCDI. For this purpose, pore-filled IEMs (PFIEMs) were then fabricated by filling the pores of the PE porous support film with monomers and carrying out in-situ photopolymerization. As a result of the experiment, the prepared PFIEMs showed excellent electrochemical properties that can be applied to various desalination and energy conversion processes. In addition, through the correlation analysis between MCDI performance and membrane characteristic parameters, it was found that controlling the degree of crosslinking of the membranes and maximizing permselectivity within a sufficiently low level of membrane electrical resistance are the most desirable membrane fabricating condition for improving MCDI performance.

• Membrane and Water Treatment
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• v.3 no.1
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• pp.63-76
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• 2012

Mother liquid discharged from a salt-manufacturing plant was electrodialyzed at 25 and $40^{\circ}C$ in a continuous process integrated with $SO_4{^{2-}}$ ion low-permeable anion-exchange membranes to remove $Na_2SO_4$ and recover NaCl in the mother liquid. Performance of electrodialysis was evaluated by measuring ion concentration in a concentrated solution, permselectivity coefficient of $SO_4{^{2-}}$ ions against $Cl^-$ ions, current efficiency, cell voltage, energy consumption to obtain one ton of NaCl and membrane pair characteristics. The permselectivity coefficient of $SO_4{^{2-}}$ ions against $Cl^-$ ions was low enough particularly at $40^{\circ}C$ and $SO_4{^{2-}}$ transport across anion-exchange membranes was prevented successfully. Applying the overall mass transport equation, $Cl^-$ ion and $SO_4{^{2-}}$ ion transport across anion-exchange membranes is evaluated. $SO_4{^{2-}}$ ion transport number is decreased due to the decrease of electro-migration of $SO_4{^{2-}}$ ions across the anion-exchange membranes. $SO_4{^{2-}}$ ion concentration in desalting cells becomes higher than that in concentration cells and $SO_4{^{2-}}$ ion diffusion is accelerated across the anion-exchange membranes from desalting cells toward concentrating cells.

• Journal of the Korean Applied Science and Technology
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• v.16 no.1
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• pp.75-81
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• 1999

HF purification performance of an ion exchange membrane(IEM) was evaluated with 0.5% HF spiked with 10ppb of Fe, Ni and Cu nitrates. The result show that after less than five turnovers through an IEM, the metallic impurity concentration drops below 1ppb. The decrease rate can be fitted to a model assuming the experimental tanks to be continuously stirred tank reaction and that the metallic impurity concentration after the IEM is a function of the single-pass purification efficiency of the membrane, the concentration before purification and the metals desorbed form the IEM. The Concentration after purification was investigated up to a cumulative Fe loading of 300ppb in the 23 liter recirculated loop. It increases linearly vs. cumulative loading and can be explained by the Langmuir theory resulting in a purification efficiency at the equilibrium of close to 99.5% in this loading regime.

• Membrane Journal
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• v.33 no.6
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• pp.315-324
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• 2023

Ion-exchange membrane (IEM), is a key component that determines the performance of the electro-membrane processes. In this review, the latest research trends in improving the performance of IEMs used in various electro-membrane processes through modification using carbon-based and metal-based nanomaterials are investigated. The nanomaterials can be introduced into IEMs through various methods. In particular, carbon-based nanomaterials can strengthen their interaction with polymer chains by introducing additional functional groups through chemical modification. Through this, not only can the ion conductivity of IEM be improved, but also the permselectivity can be improved through the sieving effect through the layered structure. Meanwhile, metal-based nanomaterials can improve permselectivity through sieving properties using the difference in hydration radius between target ions and excluded ions within a membrane by using the property of having a layered or porous structure. In addition, depending on the characteristics of the binder used, ion conductivity can be improved through interaction between nanomaterials and binders. From this review, it can be seen that the properties of IEMs can be effectively controlled using carbon-based and metal-based nanomaterials and that research on this is important to greatly improve the performance of the electro-membrane process.

• Membrane Journal
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• v.32 no.2
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• pp.91-99
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• 2022

It is a global challenge to fulfill the demand for clean water at an affordable cost to all the strata of the population. Desalination of seawater as well as brackish water by the membrane separation process is a well-established and cost-efficient method. However, there is still inherent problem of membrane fouling, disposal of the reject as well as a capital-intensive process. While electrodialysis (ED) is a membrane-based separation process in which a driving force is the potential difference. The advantages of ED process are excellent efficiency and low operation cost. Ion exchange membrane (IEM) used in the ED process needs to have higher chemical and thermal stability along with excellent mechanical strength for long-term use without losing its efficiency. The ion exchange capacity of the ED membrane is largely dependent on the conductivity of IEMs. In this review, the modification strategy of the pristine membrane to enhance the stability and ion conductivity of cation exchange membrane (CEM) and anion exchange membrane (AEM) is discussed.