Monovalent selective cation exchange membrane

Abstract

A monovalent-selective ion exchange membrane is disclosed. The membrane includes a polymeric microporous substrate, a crosslinked ion transport polymer layer on the surface of the substrate, and a charged functionalized layer covalently bonded to the ion transport layer. A method for producing the monovalent-selective cation exchange membrane is also disclosed. The method may include chemically adsorbing a styrene interlayer to the crosslinked ion transport polymer layer on the surface of the polymeric microporous substrate, chlorosulfonating the styrene interlayer to attach a sulfonyl chloride group layer, amminating the sulfonyl group layer to attach an amine group layer, and functionalizing the amine group layer with a charged compound layer to produce the cation exchange membrane. A water treatment system including the monovalent-selective cation exchange membrane and a method for facilitating water treatment including preparing the monovalent-selective cation exchange membrane are also disclosed.

Description

Cross-reference of related applications

[0001] This application claims priority to U.S. Provisional Application No. 62 / 737,373, titled "Monovalent Selective Cation Exchange Membrane," filed September 27, 2018, under Section 119 of the U.S. Patent Act; U.S. Provisional Application No. 62 / 736,176, titled "Cation Exchange Membrane by UV-Initiated Polymerization," filed September 25, 2018; and U.S. Provisional Application No. 62 / 861,608, titled "Preparation of Exchange Membrane by UV Photopolymerization," filed June 14, 2019, each of which is incorporated herein by reference in whole for all purposes. [Technical Field]

[0002] The embodiments and models disclosed herein generally relate to ion exchange membranes, and more specifically, to monovalent selective ion exchange membranes. [Overview of the Initiative]

[0003] According to one embodiment, a monovalent selective ion exchange membrane is provided. The monovalent selective ion exchange membrane may include a polymer microporous substrate. The monovalent selective ion exchange membrane may include a crosslinked ion transport polymer layer on the surface of the substrate. The monovalent selective ion exchange membrane may include a charged functionalized layer covalently bonded to the crosslinked ion transport polymer layer.

[0004] In some embodiments, the film may have a total thickness of approximately 20 μm to approximately 155 μm. The film may have a total thickness of approximately 25 μm to approximately 55 μm.

[0005] A monovalent selective ion exchange membrane can be a cation exchange membrane. A charged functionalized layer can be a positively charged functionalized layer.

[0006] In some embodiments, the positively charged functionalized layer may contain at least one of a sulfonic acid group, a carboxylic acid group, a quaternary ammonium group, and a tertiary amine group hydrolyzed to a positively charged ammonium group.

[0007] The monovalent selectivity membrane can be an anion exchange membrane. The charged functional layer can be a negatively charged functional layer.

[0008] The monovalent selectivity ion exchange membrane can have at least 100% counterion selective permeability.

[0009] The monovalent selectivity ion exchange membrane can have an initial selectivity of 8 - 12 times of Na / Ca (ppm) at room temperature.

[0010] The monovalent selectivity membrane can have a resistance of less than about 5 Ω-cm 2

[0011] The polymeric microporous substrate can include at least one of high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE).

[0012] According to another aspect, a monovalent selectivity cation exchange membrane support is provided. The monovalent selectivity cation exchange membrane support can include a polymeric microporous substrate. The monovalent selectivity cation exchange membrane support can include a crosslinked ion transport polymer layer on the surface of the substrate. The monovalent selectivity cation exchange membrane support can include an intermediate layer containing an amine group covalently bonded to the crosslinked ion transport polymer layer.

[0013] In some embodiments, the intermediate layer can include a primary amine group or a secondary amine group.

[0014] The intermediate layer can include polyethyleneimine (PEI).

[0015] The intermediate layer can include branched PEI having a molecular weight of at least 600 g / mol.

[0016] The intermediate layer may be covalently bonded to the crosslinked ion transport polymer layer by a styrene group.

[0017] The styrene group may be chemically bonded to chlorosulfonated divinylbenzene (DVB).

[0018] ​ In another embodiment, a method for producing a monovalent selective cation exchange membrane is provided. This method may include chemically adsorbing a styrene intermediate layer onto a crosslinked ion-transport polymer layer on the surface of a polymer microporous substrate. This method may include chlorosulfonating the styrene intermediate layer to deposit a sulfonyl chloride group layer onto the surface of the polymer microporous substrate. This method may include amination of the sulfonyl group layer to deposit an amine group layer onto the surface of the polymer microporous substrate. This method may include functionalizing the amine group layer with a charged compound layer to produce a monovalent selective cation exchange membrane.

[0019] In some embodiments, this method may involve chemically adsorbing styrene DVB onto a crosslinked ion-transport polymer layer on the surface of a polymer microporous substrate.

[0020] This method may involve chlorosulfonating styrene DVB with chlorosulfonic acid (ClSO3H) to bond the ClSO2 group to the styrene DVB.

[0021] This method may involve amination of ClSO2 with PEI.

[0022] This method may involve amination of ClSO2 with branched PEI having a molecular weight of at least 600 g / mol.

[0023] This method may involve functionalizing the amine layer with positively charged groups.

[0024] This method may involve functionalizing the amine layer with positively charged ammonium.

[0025] This method may further include immersing a polymer microporous substrate in a solution containing an ionogen monomer, a polyfunctional monomer, and a polymerization initiator to generate a crosslinked ion-transport polymer layer.

[0026] In another embodiment, a water treatment system is provided. The water treatment system may include a source of water to be treated. The water treatment system may include an electrochemical separator, which is fluidly connected to the water source to be treated and includes at least one monovalent selective cation exchange membrane having a charge-functionalized layer covalently bonded to the surface of the cation exchange membrane. The water treatment system may include a treated water outlet fluidly connected to the electrochemical separator.

[0027] In some embodiments, the water source to be treated is Ca 2+ and Mg 2+ It may contain at least one hardness ion selected from the following.

[0028] In some embodiments, the charged functionalized layer may be a positively charged functionalized layer comprising at least one of a sulfonic acid group, a carboxylic acid group, a quaternary ammonium, and a tertiary amine group hydrolyzed to a positively charged ammonium.

[0029] In some embodiments, the charged functionalized layer may be covalently bonded to the surface of the cation exchange membrane by a chemically adsorbed branched PEI layer.

[0030] In another embodiment, a method is provided for facilitating water treatment using an electrochemical separation apparatus. This method may include preparing a monovalent selective cation exchange membrane having a charge-functionalized layer covalently bonded to the surface of the cation exchange membrane. This method may include instructing the user to install the monovalent selective cation exchange membrane in the electrochemical separation apparatus.

[0031] In some embodiments, this method uses an electrochemical separation device, Ca 2+ and Mg 2+ This may include instructing the user to connect a fluid to a water source to be treated that contains at least one hardness ion selected from the following.

[0032] This method may include preparing a monovalent selective cation exchange membrane support having a polymer microporous substrate having a polymer microporous substrate with a covalently bonded amine base layer on its surface. This method may further include instructing the user to functionalize the amine base layer with a charged compound layer to produce a cation exchange membrane.

[0033] In yet another embodiment, a monovalent selective cation exchange membrane is provided. The cation exchange membrane may comprise a polymer microporous substrate and a positively charged functionalized layer covalently bonded to the surface of the polymer microporous substrate. The monovalent selective cation exchange membrane may have an initial selectivity of 8 to 12 times Na / Ca (ppm) at room temperature.

[0034] Monovalent selective cation exchange membranes can exhibit 4 to 8 times higher Na / Ca (ppm) selectivity after 400 days in 0.5 M NaCl at room temperature.

[0035] Monovalent selective cation exchange membranes can exhibit initial selectivity of 10 to 40 times Na / Ca (moles) at 80°C.

[0036] A monovalent selective cation exchange membrane may exhibit a 3-6 times Na / Ca (molar) selectivity after 30 days in 0.5M NaCl at 80°C.

[0037] This disclosure intends to include all combinations of any one or more of the embodiments described above, as well as any one or more of the embodiments described in the Detailed Description and any examples.

[0038] The attached drawings are not intended to be drawn to actual size. In the drawings, each identical or nearly identical component shown in various drawings is represented by similar numbers. For clarity, not all components are labeled in every drawing. [Brief explanation of the drawing]

[0039] [Figure 1]Figure 1 shows the chemical structures of polyethyleneimine (PEI) molecules exhibiting primary (-NH2), secondary (-NH-), and tertiary amine groups. [Figure 2] Figure 2 illustrates the formation of ionic bonds by physical adsorption between a primary or secondary amine of PEI and sulfonic acid groups on the surface of a cation exchange membrane, according to one embodiment. [Figure 3] Figure 3 illustrates, in one embodiment, the formation of a covalent bond by chemiadsorption between a primary or secondary amine of PEI and chlorosulfonic acid (ClSO3H), which occurs as a two-step process. [Figure 4] Figure 4A is a graph showing the concentrations of Ca2+ and Na+ in a dilute stream over time for water treatment using a conventional membrane. Figure 4B is a graph showing the concentrations of Ca2+ and Na+ in a dilute stream over time for water treatment using an alternative conventional membrane. [Figure 5] Figure 5 is a graph showing the concentrations of Ca2+ and Na+ in a dilute stream over time for water treatment using a monovalent selective ion exchange membrane according to one embodiment. [Figure 6] Figure 6A is a graph showing the ion concentration and sodium absorption rate (SAR) of experimental groundwater treated with a monovalent selective ion exchange membrane according to one embodiment. Figure 6B is a graph showing the ion concentration and SAR of experimental groundwater treated with a conventional cation exchange membrane. [Figure 7] Figure 7 is a graph of ion concentrations in experimental seawater treated with a monovalent selective ion exchange membrane according to one embodiment. [Figure 8] Figure 8 is a graph showing the time-dependent monovalent transport selectivity for water treatment using a monovalent selective ion exchange membrane according to one embodiment. [Figure 9] Figure 9 is a schematic diagram of the membrane selectivity experimental apparatus. [Figure 10]Figure 10A is a graph showing the concentration of target cations in a dilute stream desalted by a monovalent selective cation exchange membrane according to one embodiment. Figure 10B is a graph showing the concentration of target cations in a dilute stream desalted by a conventional cation exchange membrane. Figure 10C is a graph showing the concentration of target cations in a dilute stream generated by a monovalent selective cation exchange membrane according to one embodiment. Figure 10D is a graph showing the concentration of target cations in a dilute stream generated by a conventional cation exchange membrane. [Figure 11] Figure 11A is a graph of the concentration of selected ions in a concentration compartment using a monovalent selective anion exchange membrane for treating seawater at an applied current density of 300 A / m2, according to one embodiment. Figure 11B is a graph of the concentration of selected ions in a concentration compartment using a monovalent selective cation exchange membrane for treating seawater at an applied current density of 300 A / m2, according to one embodiment. [Figure 12] Figure 12A is a graph showing the lifetime selectivity (stability) at 80°C for a conventional / commercial monovalent selectivity film and the monovalent selectivity film disclosed herein, according to one embodiment. Figure 12B is a graph showing the lifetime selectivity (stability) at room temperature for a conventional / commercial monovalent selectivity film and the monovalent selectivity film disclosed herein, according to one embodiment. Detailed description of the invention

[0040] Embodiments disclosed herein provide ion exchange membranes and processes for their manufacture. The electrodialysis (ED) membranes described herein can generally combine low resistance and high selective permeability. Their properties can make them very effective in water desalination applications, particularly in seawater desalination. Their properties can also make them very effective in the treatment of irrigation water, particularly in the adjustment of sodium absorption rate (SAR) values. The ion exchange membranes described herein can be manufactured by polymerizing one or more monofunctional ionogen monomers with a neutral monomer, at least one polyfunctional monomer, in the pores of a porous substrate.

[0041] Ion exchange membranes are typically used to transport cations or anions under an electrical or chemical potential. Ion exchange membranes may have negatively or positively charged groups attached to the polymer material that makes up the majority of the membrane. The counterion of each group typically functions as a transportable ion. Cation exchange membranes may have fixed negative charges and mobile positively charged cations. Anion exchange membranes may have fixed positively charged groups and mobile negatively charged anions. The properties of ion exchange membranes can be manipulated by controlling the amount, type, and distribution of fixed ionic groups. These membranes can be described as strong acid, strong base, weak acid, or weak base membranes. Strong acid cation exchange membranes typically have sulfonic acid groups as the charged groups. Weak acid membranes typically have carboxylic acid groups that constitute the fixed charged groups. Quaternary and tertiary positively charged ammonium compounds can generate fixed positively charged groups in strong base and weak base anion exchange membranes, respectively.

[0042] Ion exchange membranes can be used for desalination of water by electrodialysis (ED), as a power source for reverse electrodialysis, or as a separator in a fuel cell. Therefore, the water treatment systems disclosed herein may be, or include, a desalination system, a power generation system, or a reverse electrodialysis system. Other applications include metal ion recovery in the electroplating and metal finishing industries, and applications in the food and beverage industry. In other embodiments, the water treatment systems disclosed herein may be, or include, a metal ion recovery system or a food and beverage processing system.

[0043] In certain exemplary embodiments, the ion exchange membranes disclosed herein can be used in groundwater treatment and / or agricultural environments. The water treatment systems disclosed herein may be or include groundwater treatment systems. The water treatment systems disclosed herein may be or include agricultural irrigation water sifting systems. This method may include treating groundwater. This method may include treating agricultural water sifting.

[0044] Electrodialysis generally desalinates water by moving ions and some charged organic matter through paired anion- and cation-selective membranes under the power of a DC voltage. ED equipment may include conductive, substantially water-impermeable anion-selective and cation-selective membranes arranged as opposing walls of cells. Adjacent cells typically form cell pairs. A membrane stack may contain many, sometimes hundreds, cell pairs. An ED system may contain many stacks. Each membrane stack typically has a DC (direct current) anode at one end of the stack and a DC cathode at the other end. Under a DC voltage, ions can move towards electrodes of the opposite charge.

[0045] A cell pair may contain two types of cells: dilute cells and concentrated cells. Each type of cell can be defined by opposing membranes. An exemplary cell pair may include a common cation transport membrane wall and two anion transport membrane walls forming two cells. That is, a first anion transport membrane and a cation transport membrane form a dilute cell, and its cation transport membrane and a second anion transport membrane form a concentrated cell. In a dilute cell, cations typically pass through the cation transport membrane facing the anode, but may be stopped by the anion transport membrane of the concentrated cell pair in the direction facing the cathode. Similarly, anions pass through the anion transport membrane of the dilute cell facing the cathode, but may be stopped by the adjacent pair of cation transport membranes facing the anode. In this way, salts can be removed from the dilute cell. In adjacent concentrated cells, cations may enter from one direction and anions from the opposite direction. The flow in the stack can be arranged so that the dilute flow and the concentrated flow are kept separate. Therefore, desalination water streams can be generated from rarefied flows.

[0046] A lack of sufficient quality irrigation water negatively impacts crop yields and may necessitate the selection of less-demanded crop varieties. New irrigation methods, such as drip irrigation, which reduce water usage, can also lead to unsustainable conditions due to the accumulation of salts and impurities in the soil from the irrigation water. Soil salinity can rise to much higher concentrations than irrigation water because most of the water is used by crops and evaporation. Irrigation conditions, combined with insufficient raw water or rainfall to leach the soil, can result in soil salinity four to five times higher than that of the irrigation water itself. Furthermore, if the land consists of relatively shallow, impermeable layers, irrigation water can raise the groundwater level. When highly saline groundwater reaches the root level of crops, it can harm crop growth. Additionally, saline soils can damage leafy crops due to water spray from the soil surface. Furthermore, when saltwater is discharged from farmland, trace impurities in the soil such as selenium or boron, or residual contaminants from fertilizer use such as nitrates, can pollute the wastewater, making safe wastewater management difficult.

[0047] When irrigating crops, yields can be affected by the total dissolved salt (TDS) concentration. TDS is usually correlated with conductivity values. For example, a conductivity value of 1 mS / cm corresponds to approximately 500-700 ppm TDS. Various plants benefit from low TDS irrigation water. For example, beans, carrots, and strawberries can benefit from irrigation with water with a conductivity of less than 1 mS / cm. Other plants can tolerate irrigation water with a conductivity of approximately 5 mS / cm. Furthermore, controlling the SAR value at a given TDS and conductivity can affect soil cohesiveness and efficient water infiltration. For example, irrigation water with a conductivity of less than 1 mS / cm can benefit from an SAR value greater than 3 to maintain soil structure. Irrigation water with a conductivity of 2-3 mS / cm can benefit from an SAR value of approximately 10.

[0048] The need for irrigation water also competes with the need for drinking water for humans and contaminant-free water for livestock and wildlife. Therefore, agricultural areas generally require a water source that combines irrigation and drinking water. The membranes described herein can be used for agricultural irrigation water treatment. In particular, the membranes described herein can be used to control the TDS, conductivity, and SAR values ​​of agricultural irrigation water. In some embodiments, the membranes described herein can provide water having a conductivity of less than 1 mS / cm. The membranes described herein can provide water having a conductivity between 2 and 3 mS / cm, between 3 and 5 mS / cm, or greater than 5 mS / cm (e.g., between 5 and 7 mS / cm). The membranes described herein can provide water having an SAR value greater than 3, for example between 3 and 5. The membranes described herein can provide water having an SAR value greater than 5, for example between 5 and 10. The membranes described herein can provide water having an SAR value of about 10 or more, for example between 10 and 12.

[0049] Monovalent selectivity or monovalent selective membranes primarily transport monovalent ions. Monovalent selectivity membranes can separate ions based on charge and / or size. Monovalent selectivity membranes can distinguish between monovalent and divalent ions. Monovalent selectivity cation transport membranes can distinguish between ions with a +1 charge, such as sodium and potassium, and ions with a larger positive charge, such as magnesium and calcium. Thus, the monovalent selectivity cation exchange membranes described herein can selectively transport monovalent ions, such as sodium and potassium ions, while blocking the transport of divalent ions, such as calcium and magnesium ions. Similarly, monovalent selectivity anion membranes can separate ions with a -1 charge, such as chlorides, bromides, and nitrates, from ions with a larger negative charge. Thus, the monovalent anion exchange membranes described herein can selectively transport monovalent ions, such as chloride and nitrate ions, while blocking the transport of divalent ions, such as sulfate ions.

[0050] The ion exchange membranes disclosed herein can be used to treat the desalination of brackish water and wastewater. While ED is generally considered too expensive for use with seawater, the ion exchange membranes disclosed herein can be used efficiently for seawater desalination. Effective and efficient seawater desalination is achieved with a 1 Ω-cm² 2 Less than, for example, 0.8 Ω-cm 2 Less than 0.5 Ω-cm 2 It can be implemented with a membrane resistance of less than 1.5. The ion exchange membranes disclosed herein can also provide ion selective permeability of more than 90%, for example, more than 95% or more than 98%. Furthermore, the ion exchange membranes disclosed herein have a longer service life and greater physical strength and chemical durability than comparable conventional ion exchange membranes. Finally, the ion exchange membranes disclosed herein can be manufactured at a relatively low cost.

[0051] As a result, the ion exchange membranes disclosed herein may be used in reverse electrodialysis (RED). RED can be used to convert the free energy generated by mixing two aqueous solutions with different salinity concentrations into electricity. Generally, the greater the difference in salinity concentration, the greater the potential for power generation. The water treatment systems disclosed herein may be or include RED systems. The methods disclosed herein can be used to generate electricity.

[0052] The ion exchange membranes disclosed herein can be used as polymer electrolyte membranes (PEMs). A PEM is a type of ion exchange membrane that functions as both an electrolyte and a separator, and can prevent direct physical mixing of hydrogen from the anode and oxygen supplied to the cathode. A PEM may contain negatively charged groups, such as sulfonic acid groups, either bonded to or as part of the polymer constituting the PEM. Protons typically move through the membrane by jumping from one fixed negative charge to another and permeating the membrane.

[0053] The films disclosed herein may generally include an ion exchange membrane support and a charge-functionalized layer covalently bonded to the ion exchange membrane support. The ion exchange membrane support may include a polymer microporous substrate and a crosslinked ion-transport polymer layer on the surface of the substrate. As an intermediate manufacturing step, the membrane support may further include an amine group layer covalently bonded to the crosslinked ion-transport polymer layer.

[0054] The membranes described herein can generally exhibit good mechanical strength. The mechanical strength can be sufficient to enable the membrane to withstand the stresses of a continuous membrane manufacturing process, be fabricated, and be sealed into a final membrane holding device or module without obvious or hidden damage that can occur after some time of operation. Further, the mechanical strength can be sufficient to provide high dimensional stability. The membrane generally can exhibit minimal variance in dimensions while functioning as a desalination device, during washing, disinfection or antifouling regimens, or during transport or storage. For example, high dimensional stability can be provided against changes in the ionic content or temperature of the fluid contacting the membrane, such that during operation, fluctuations in the distance between membrane pairs that can lead to inefficiencies in current are minimized. Changes in dimensions during electrodialysis can cause stress on the constrained membrane and can lead to membrane defects and performance degradation, and generally can be minimized.

[0055] The membranes described herein can exhibit low resistance. Generally, lower resistance results in reduced electrical energy required for freshwater production and lower operating costs. The specific membrane resistance can sometimes be measured in Ω-cm. Another engineering measure is Ω-cm 2 and is. Resistance can be measured by a resistance test process using a cell having two electrodes of known area in an electrolyte solution. Platinum or black graphite is typically used for the electrodes. Next, the resistance between the electrodes is measured. A membrane sample of known area can be placed between the electrodes in the electrolyte solution. The electrodes do not touch the membrane. Next, the resistance is measured again with the membrane in place. Next, the membrane resistance can be estimated by subtracting the electrolyte resistance without the membrane from the test results when the membrane is in place.

[0056] Resistance can also be measured by determining the voltage-versus-current curve in a cell having two well-stirred chambers separated by the membrane. A calomel electrode can be used to measure the potential drop across the entire membrane. The slope of the potential-drop-versus-current curve is obtained by varying the voltage and measuring the current.

[0057] Electrochemical impedance can also be used in the calculations. This method allows an alternating current to be applied across the entire film. Measurements at a single frequency provide data related to the film's electrochemical properties. By using variations in frequency and amplitude, detailed structural information can be obtained.

[0058] The membranes described herein may have high counterion selective permeability. Selective permeability generally refers to the relative transport of counterions to coions during electrodialysis. In the case of a theoretically ideal cation exchange membrane, only positively charged ions pass through the membrane, resulting in counterion selective permeability of 1.0 or 100%. Selective permeability can be determined by measuring the potential of the entire membrane while separating monovalent salt solutions of different concentrations.

[0059] The ion exchange membranes disclosed herein may have reduced water permeability. Infiltration of the dilute stream through membrane defects under the driving force of the osmotic pressure difference between the dilute and concentrated streams can reduce efficiency. Water infiltration can reduce current efficiency and the productivity of purified water by removing pure water. Water loss can be particularly severe in seawater electrodialysis using thin membranes because a high concentration difference between the concentrated (brine) side of the membrane and the pure water side of the membrane usually increases the osmotic pressure driving force. Membrane defects can be particularly detrimental to operation because high osmotic pressure tends to force pure water through such defects, increasing water loss and power consumption.

[0060] The membranes disclosed herein may generally have a structure that allows for high cation permeability and low osmotic flow. As used herein, apparent counterion selective permeability is the ratio of the transport rates of counterions (cations) to coions (anions). Conventional measurement parameters do not indicate counterion removal rates. In certain embodiments, the membranes disclosed herein may be manipulated to control cation permeability.

[0061] The permeability of cations can be controlled by the structure of the ion (molecular size and total charge) and the influence of the membrane's microstructure. If the membrane is designed to have relatively small pores, the membrane's microstructure can slow down counterion permeability. The relative term can be interpreted as meaning that the counterion encounters high resistance from interactions with the membrane material as it passes through the membrane, as if passing through a tunnel slightly larger than its apparent diameter. Membranes with relatively low water content tend to have reduced counterion permeability pathways. The membrane's water content and effective pore size can be manipulated by balancing the amount and properties of hydrophilic monomers and crosslinking monomers to enhance counterion permeability. Crosslinking monomers can be selected to be hydrophobic or hydrophilic.

[0062] The membranes disclosed herein may generally include ion exchange membrane supports. The ion exchange membrane supports may include a polymer microporous substrate and a crosslinked ion-transport polymer layer on the surface of the substrate. The membrane supports can be manufactured by a process that includes selecting a suitable porous substrate and incorporating a crosslinked ion-transport polymer layer on the surface of the substrate.

[0063] Microporous film substrates can be manufactured from polyolefins, polyvinylidene fluoride, or other polymers. One exemplary class of substrates includes a thin polyolefin film. Another exemplary class of substrates is manufactured from high-density polyethylene (HDPE). Another exemplary class of substrates is manufactured from ultra-high molecular weight polyethylene (UHMWPE). Microporous substrates may include microporous films of polypropylene, high molecular weight polyethylene, ultra-high molecular weight polyethylene, or polyvinylidene fluoride. Substrates can generally have a thickness of less than about 155 μm, for example, less than about 55 μm or less than about 25 μm.

[0064] Exemplary microporous membrane materials can be used to produce very thin ion-exchange membranes, for example, as disclosed in U.S. Patent No. 8,703,831, which is incorporated herein by reference in its entirety for all purposes. Exemplary ion-exchange membranes may have thicknesses of 12 to 100 μm, for example, 25 to 32 μm. Thin membranes allow for fast chlorosulfonation reactions, which are effective over a large portion of the membrane and are described in more detail below. For example, a chlorosulfonation reaction of 5 minutes may be sufficient to complete bulk chlorosulfonation. Thus, the methods described herein may involve carrying out a chlorosulfonation reaction that is effective in chlorosulfonating a large portion of the membrane in about 5 minutes.

[0065] Furthermore, certain exemplary microporous film materials can be used to provide stability against aggressive chemicals. For example, HDPE film substrates are generally stable against ClSO3H. Materials such as polypropylene may not be sufficiently stable against ClSO3H.

[0066] Embodiments of the substrate film may have a porosity of more than about 45%, for example, more than about 60%. In certain embodiments, the substrate film may have a porosity of more than about 70%. The substrate film may have a rated pore size of about 0.05 μm to about 10 μm, for example, about 0.1 μm to about 1.0 μm, or about 0.1 μm to about 0.2 μm.

[0067] A membrane support can be manufactured by saturating a monomer solution in the pores of a substrate. The monomer solution can be polymerized from functional monomers, crosslinking agents, and polymerization initiators in the pores to form a crosslinked charged polymer. In certain embodiments, the functional monomers may include ionogen monomers, e.g., monofunctional ionogen monomers, and polyfunctional monomers, e.g., crosslinking agents. As used herein, the term ionogen monomer generally refers to a monomer species in which at least one charged group is covalently bonded. As will be described in more detail below, the charged group may be positively or negatively charged. A monofunctional monomer generally refers to a monomer having a single site for advancing a polymerization reaction. A polyfunctional monomer generally refers to a monomer having multiple polymerization reaction sites and thus capable of forming a networked or crosslinked polymer.

[0068] The process of polymerizing a crosslinked ion-transport polymer layer within the pores of a substrate may involve saturating the substrate with a solution containing monofunctional ionogen monomers, polyfunctional monomers, and polymerization initiators. This process may involve removing excess solution from the surface of the substrate while leaving the porous volume saturated with the solution and initiating polymerization. Polymerization can be initiated by the application of heat, ultraviolet (UV) light, or ionizing radiation, in the absence of substantially all oxygen as needed. This process can be carried out to incorporate a crosslinked ion-transport polymer layer that substantially completely fills the pores of the substrate.

[0069] Therefore, in certain embodiments, the membrane support may be produced by polymerization of one or more ionogen monomers, neutral monomers, and suitable crosslinking monomers. Exemplary neutral monomers are hydroxyethyl acrylate and hydroxymethyl methacrylate. Other neutral monomers are within the scope of this disclosure. The ionogen monomers may be selected to produce a cation exchange membrane or an anion exchange membrane.

[0070] Monomers containing negatively charged groups include, but are not limited to, sulfonated acrylic monomers suitable for providing cation exchange capacity, such as 2-sulfoethyl methacrylate (2-SEM), 2-propylacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sulfonated glycidyl methacrylate, 3-sulfopropyl methacrylate, and sodium 1-allyloxy-2-hydroxypropylsulfonate. Other exemplary monomers are acrylic acid and methacrylic acid or their salts, sodium styrenesulfonate, styrenesulfonic acid, sulfonated vinylbenzyl chloride sodium 1-allyloxy-2-hydroxypropylsulfonate, 4-vinylbenzoic acid, trichloroacrylic acid, vinyl phosphoric acid, and vinylsulfonic acid. Preferred monomers are 2-sulfoethyl methacrylate (2-SEM), styrenesulfonic acid and its salts, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

[0071] The embodiments of cation exchange membranes described herein have a capacitance of approximately 1.0 Ω-cm². 2 Less than, for example, about 0.5 Ω-cm 2 It may have a resistivity of less than 0. Certain embodiments of the cation exchange membranes described herein may have a selective permeability of more than about 95%, for example, more than about 99%. In some embodiments, the ionogen monomer for the production of the cation exchange membrane may be 2-sulfoethyl methacrylate (2-SEM) or 2-acrylamido-2-methylpropanesulfonic acid (AMPS), or may include 2-sulfoethyl methacrylate (2-SEM) or 2-acrylamido-2-methylpropanesulfonic acid (AMPS). One exemplary crosslinking agent is ethylene glycol dimethacrylate. Other ionogen monomers and crosslinking agents are within the scope of this disclosure.

[0072] Monomers containing positively charged groups include, but are not limited to, representative examples, methacrylamidopropyltrimethylammonium chloride, trimethylammonium ethyl methacrylate, quaternary salts of polyamines and vinyl aromatic halides, such as 1,4-diazabicyclo[2,2,2]octanedi (vinyl benzyl chloride) (a quaternary salt of 1,4-diazabicyclo[2,2,2]octane (DABCO) and piperazine divinyl chloride), or quaternary salts formed by the reaction of cyclic ethers, polyamines, and alkyl halides, such as iodoethyldimethylethylenediamino2-hydroxylpropyl methacrylate (a quaternary ammonium salt formed by reacting glycidyl methacrylate (GMA) with N,N-dimethylethylenediamine and ethyl iodide), and vinylbenzyltrimethylammonium chloride. Other exemplary monomers for anion exchange membranes include trimethylammonium ethyl methacrylate, 3-(acrylamidopropyl)trimethylammonium chloride, N,N,N',N',N''-pentamethyldiethylenetriamine di(vinylbenzyl chloride (quaternary salt of N,N,N',N',N''-pentamethyldiethylenetriamine and vinylbenzyl chloride)), glycidyl methacrylate / trimethylamine, or glycidyl methacrylate / N,N-dimethylethylenediamine reaction products.

[0073] The embodiments of the anion exchange membrane described herein have a capacitance of approximately 1.0 Ω-cm². 2 Less than, for example, about 0.5 Ω-cm 2It may have a resistivity of less than 0. In certain embodiments, the anion exchange membranes described herein may have a selective permeability of more than about 90%, for example, more than about 95%. In some embodiments, the ionogen monomer for producing the anion exchange membrane may be or include trimethylammonium ethyl methacrylate crosslinked with ethylene glycol dimethacrylate, or glycidyl methacrylate / N,N-dimethylethylenediamine reaction products and N,N,N',N',N”-pentamethyldiethylenetriamine di(a crosslinked ion transport polymer formed by polymerization of vinyl benzyl chloride (a quaternary salt of N,N,N',N'-pentamethyldiethylenetriamine and vinyl benzyl chloride) or 1,4-diazabicyclo[2,2,2]octane di(vinyl benzyl chloride) (a quaternary salt of 1,4-diazabicyclo[2,2,2]octane (DABCO) and vinyl benzyl chloride).

[0074] Polyfunctional monomers containing one or more ionic groups can be used. Without limiting the examples, monomers such as 1,4-divinylbenzene-3-sulfonic acid or its salts can be used. The degree of crosslinking may range from 2% to 60%. Typical examples of polyfunctional monomers suitable for providing crosslinking with monomers containing negatively or positively charged groups include, but are not limited to, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol triacrylate, tetraethylene glycol dimethacrylate, divinylbenzene, and tri This includes methylolpropane triacrylate, isophorone diisocyanate, glycidyl methacrylate, trimethylolpropane trimethacrylate, ethoxylated (n) bisphenol A di(meth)acrylate (n=1.5, 2, 4, 6, 10, 30), ethoxylated (n) trimethylolpropane tri(meth)acrylate (n=3, 6, 9, 10, 15, 20), propoxylated (n) trimethylolpropane triacrylate (n=3, 6), vinyl benzyl chloride, glycidyl methacrylate, and others.

[0075] Polymerization initiators can be free radical polymerization initiators. Usable free radical polymerization initiators include, for example, benzoyl peroxide (BPO), ammonium persulfate, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2yl)propane], and dimethyl-2,2'-azobis(2-methylpropionate).

[0076] The pore filling or saturation process of the substrate can be carried out at a slightly higher temperature (e.g., >40°C) to reduce the solubility of air. In other embodiments, the pore filling or saturation process of the substrate can be carried out after gentle vacuum treatment of the substrate sample immersed in the formulation solution. The substrate sample can be pre-soaked and then placed on a polyester or similar sheet and covered with a cover sheet. The soaked and covered substrate can be smoothed to remove air bubbles. Several pre-soaked portions can be layered and then placed on a polyester or similar sheet, covered with a cover sheet, and smoothed to remove air bubbles.

[0077] The immersed substrate can be heated in an oven to a temperature and for the required time sufficient to initiate complete polymerization. The immersed substrate can also be placed on a heated surface to a temperature and for the required time sufficient to initiate and complete polymerization. Alternative methods can be used to initiate the polymerization reaction. Ionizing radiation, such as ultraviolet light, gamma rays, or electron beam radiation, can be used to initiate the polymerization reaction.

[0078] A continuous pilot or manufacturing method may include saturating a porous substrate, initiating and completing polymerization, and washing or leaching non-polymerized species from the currently formed film. The film may optionally be dried. Salt solution preparation may be carried out via a tank of salt solution, by immersing rolls of wound film, or in a continuous immersion process, such as after manufacturing to modules.

[0079] If the monomer solution is formulated with a solvent that wets the substrate, the process can be initiated by feeding the substrate from a roll into a tank of monomer formulation, and then wiping away any excess solution through it. The immersed substrate can be assembled between two layers of plastic sheets fed from the roll and sandwiched between two rolls to remove air and produce a smooth multilayer assembly. One exemplary sheet material is polyethylene terephthalate film. Other sheet materials can be used. The assembly can be processed through an oven or on heated rolls to initiate and complete polymerization. One alternative method may involve flowing a saturated sheet through an oven covered with an inert gas. Inert gases may be suitable for use with high-boiling point solvents.

[0080] UV light initiation with a suitable polymerization initiator can be used. This method may involve irradiating the assembly with UV light for a sufficient intensity and duration to initiate and complete polymerization. For example, the described three-layer assembly may be carried out via a tunnel or other process apparatus having an inlet and outlet for the substrate web with UV light sources on one or both sides of the web. Using a high-boiling-point formulation, this method can be carried out in an inert gas atmosphere.

[0081] The cover sheet can be removed after polymerization. The resulting film can then be washed and optionally dried.

[0082] Organic solvents can be used as reactant supports. One useful class of solvents is dipolar aprotic solvents. Some examples of suitable solvents include dimethylacetamide, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoramide or triamide, acetone acetonitrile, and acetone. Organic solvents can be used to solvate monomers containing ionic groups and monomers that are not water-soluble. One exemplary solvent is N-methylpyrrolidone. Other solvents that can be used are N-propanol and dipropylene glycol. In certain embodiments, similar hydroxyl-containing solvents can be used, such as alcohols, diols such as isopropanol and butanol, various glycols, or polyols such as glycerin. Other solvents are within the scope of this disclosure. The solvents discussed can be used alone or in combination. Some solvents can be used with water to increase the solubility of ion-containing organic compounds.

[0083] By selecting monomer mixtures and manipulating crosslinked copolymers, membranes with a desired balance of properties can be produced. For example, combining water-soluble and / or swellable ionogen monomers with non-water-swellable comonomers can produce copolymers with a high degree of ionic groups and reduced swelling in water. Such ion exchange membranes can be used for desalination. In particular, exemplary copolymers may have better physical strength in water and less dimensional change during use due to changes in the ion content of water or temperature changes. Therefore, exemplary ion exchange membranes may exhibit suitable mechanical strength, low electrical resistance, and high counter-ion selective permeability, for example, seawater electrodialysis.

[0084] The ion exchange membranes disclosed herein may include a charge-functionalized layer covalently bonded to a crosslinked ion transport polymer layer.

[0085] Many ion exchange membranes are polyvalent selective. A polyvalent ion selective membrane may refer to an ion exchange membrane that selectively transports polyvalent ions. For example, common cation exchange membranes used in EDs allow for faster transport of polyvalent ions than monovalent ions. Faster transport of polyvalent ions usually occurs because ions with a larger charge number are attracted by a greater electric force during movement under the same electric field.

[0086] The ion exchange membranes disclosed herein may be monovalent selective membranes. Ion exchange membranes can be designed to select monovalent ions over polyvalent ions by controlling charge factors such as surface depletion conditions, membrane hydrophobicity, degree of crosslinking, and membrane intrinsic charge conditions. For example, altering the degree of crosslinking and hydrophilicity of a cation exchange membrane can result in a significant delay between polyvalent and monovalent ions by creating low water conditions within the membrane that are unfavorable to polyvalent ions.

[0087] The monovalent selective membranes disclosed herein may have manipulated surface modifications. Surface modifications of ion exchange membranes are generated by providing charged molecules on the membrane surface, which can slow ion transport at higher valence charge numbers. Monovalent selective cation exchange membranes may have positively charged molecules on their surface. For example, a strong acid cation exchange membrane may be functionalized with sulfonic acid groups as charging groups. A weak acid membrane may be functionalized with carboxylic acid groups that constitute fixed charging groups. Quaternary and tertiary positively charged ammonium can be used to functionalize membranes with positively charged groups in strong base and weak base anion exchange membranes, respectively. Monovalent selective anion exchange membranes may have negatively charged molecules on their surface.

[0088] Furthermore, the strength of the surface charge repellent can be manipulated by controlling the charge distribution on the surface of the film. The strength of the charge repellent typically depends on the charge distribution when the same number of charged molecules are provided on the surface. Simply put, the electric field strength of an ion exchange membrane is defined as dq / dx, where q is the number or concentration of charges and x is the depth along ion transport.

[0089] Therefore, in some embodiments, the charged functionalized layer formed on the surface of the film may be selected to be a single layer that substantially does not affect the ion transport resistance, while providing a strong barrier to polyvalent ions or a very large dq / dx value compared to monovalent ions. Furthermore, the single layer may not have a significant impact on the overall conductance of the film. For example, the single layer may not have a significant impact on the transport of water molecules by ions.

[0090] The crosslinked ion-transport polymer layer of the ion-exchange membrane support can be functionalized by covalently bonding an intermediate layer to the polymer layer and reacting the intermediate layer with a charged functionalization layer. In certain embodiments, the intermediate layer may be a molecule containing an amine group. During the intermediate reaction, the amine group may exchange with water to form four covalent bonds or ammonium. The intermediate layer may contain surface-adsorbed polyethyleneimine (PEI). Various primary, secondary, and tertiary amines may provide significant selectivity for polyvalent ions. The molecular structure of PEI is shown in Figure 1.

[0091] As mentioned above, the charged functionalization layer can be selected to be a single layer. In particular, the charged functionalization layer may be a single layer on the surface of the ion exchange membrane. Penetration of the functionalization layer into a large portion of the membrane may react with the charged ion transport layer, resulting in a decrease in the membrane's selective permeability. Therefore, the intermediate layer may be large enough to bond to the surface of the crosslinked polymer-coated microporous polymer membrane without substantially penetrating the membrane's pores. For example, the intermediate layer may be large enough to substantially prevent penetration of the micropores of the polymer substrate.

[0092] The intermediate layer can be selected to have a size larger than the pores of the microporous polymer substrate. Therefore, in some embodiments, the intermediate layer may contain molecules having a molecular weight of at least 100 g / mol, for example, at least 600 g / mol. The intermediate layer may contain molecules having a molecular weight of at least 1,000 g / mol, for example, at least 10,000 g / mol. The intermediate layer may contain molecules having a molecular weight of at least 40,000 g / mol, for example, at least 50,000 g / mol or at least 60,000 g / mol. The intermediate layer may contain molecules having a molecular weight of at least 70,000 g / mol and at least 80,000 g / mol. The intermediate layer may contain molecules having a molecular weight of 60,000 g / mol to 120,000 g / mol. In exemplary embodiments, the intermediate layer may contain branched PEI, which may have molecular weights as described herein.

[0093] Conventionally, PEI can be coated onto the surface of cation exchange molecules by physicoadsorption. Simply put, physicoadsorption is a physicoad reaction that brings about ionic bonding of PEI onto a crosslinked polymer layer, as shown in Figure 2. However, since ionic bonding is generally unstable, charged molecules on the surface may dissolve in water, resulting in a loss of selectivity.

[0094] The methods disclosed herein may include adhering an intermediate layer to a crosslinked ion transport polymer layer by chemiadsorption. Chemiadsorption generally includes chemically adsorbing an intermediate layer to a polymer layer such that the intermediate layer is covalently bonded. Thus, the ion exchange membrane supports disclosed herein may have a covalently bonded intermediate layer. Covalent bonding can improve the surface stability of the ion exchange membrane. As a result, covalent bonding can increase the selectivity of the membrane for a longer lifetime. In some embodiments, the ion exchange membrane may have an operating lifetime of more than 150 days, for example, more than 400 days when used at room temperature. The ion exchange membrane may have an operating lifetime of more than 2 or 3 years when used at room temperature. Furthermore, the ion exchange membrane may have an operating lifetime of more than 30 days when used at 80°C.

[0095] The intermediate layer may have bonding groups configured to covalently bond the intermediate layer to the crosslinked ion transport polymer layer. The bonding groups may be selected to enhance stability. For example, the bonding groups may be selected to provide a bond that is sufficiently stable to withstand organic compounds in the water being treated during use. In particular, the bonding groups may be sufficiently stable to withstand organic contaminants such as benzyne, toluene, ethylbenzene, and xylene over long periods during use. Thus, the ion exchange membranes disclosed herein can be used to treat wastewater containing organic contaminants such as generated water, groundwater, brackish water, brine, and seawater. The wastewater may contain, for example, about 100 to 1000 ppm of TDS. In certain embodiments, the wastewater may contain, for example, about 100 to 400 ppm of TDS, about 400 to 600 ppm of TDS, or about 600 to 1000 ppm of TDS.

[0096] The monovalent selective cation exchange membranes disclosed herein may be used to treat water containing at least one hardness ion. For example, the water to be treated may contain at least one positively charged divalent ion. In certain embodiments, the water to be treated is Ca2 + and Mg2 + It may contain at least one hardness ion selected from the following. Furthermore, the monovalent selective cation exchange membranes disclosed herein can be used in agricultural water treatment where high sodium content water can damage the soil, but magnesium and calcium are beneficial.

[0097] In one exemplary embodiment, the binding group may be a styrene group. Chemical adsorption of the amine intermediate layer onto the ion-crosslinked polymer layer may include plasma grafting of the amine intermediate layer onto its surface.

[0098] The chemisorption of the intermediate layer can be carried out in a multi-step process. In one exemplary embodiment, as shown in Figure 3, amine groups may react with sulfonyl chloride to form stable immobilized amine groups in a series of reactions. Briefly, a method for producing an ion exchange membrane may involve covalently bonding a styrene layer to a crosslinked polymer layer to form a first intermediate layer. The styrene layer may contain sulfonyl chloride groups. The reaction can be carried out for a sufficient time to bond the styrene layer to most of the substrate. For example, the reaction can be carried out for a sufficient time for the styrene layer to penetrate into the pores of the substrate. Sufficient time can be on the order of several hours, especially in embodiments where the substrate has a thickness of less than about 155 μm, for example less than about 25 μm. For example, the reaction can be carried out in less than about 10 hours. The reaction can be carried out for about 1-2 hours, about 2-5 hours, about 3-6 hours, or about 4-7 hours.

[0099] In exemplary embodiments, the styrene layer may comprise divinylbenzene (DVB). In such embodiments, the method may further comprise attaching sulfonyl chloride groups to the DVB styrene layer. To bond the sulfonyl chloride groups to the DVB styrene layer, the method may comprise polymerizing and chlorosulfonating the DVB. In exemplary embodiments, chlorosulfonation can be carried out by fumigating concentrated sulfuric acid or chlorosulfonic acid (ClSO3H) over the DVB. The chlorosulfonic acid can be hydrolyzed with a caustic solution. In such exemplary embodiments, the chlorosulfonation reaction bonds ClSO2 groups to the DVB.

[0100] The chlorosulfonation reaction can be carried out for a sufficient amount of time to penetrate most of the substrate. A sufficient time for the chlorosulfonation reaction can be on the order of several hours. For example, the chlorosulfonation reaction can be carried out in less than approximately 10 hours. The chlorosulfonation reaction can also be carried out in approximately 1-2 hours, 2-5 hours, 3-6 hours, or 4-7 hours.

[0101] A method for producing an ion-exchange membrane may involve amination of the sulfonyl chloride groups of a first intermediate layer with an amine group layer to generate chemically immobilized amine-containing groups on the surface of the membrane support. The amine groups may include primary or secondary amines. The chemically immobilized amine groups may generally include functionalizable amines. Functionalizable amines can be selected based on the designed charged molecule. Furthermore, the amine groups may be large enough to bond to the outer surface of the substrate while substantially inhibiting penetration of the substrate pores. The amination reaction can be carried out overnight. For example, the amination reaction may be carried out for about 10 to 18 hours. The chemically immobilized amine-containing groups may be PEI or branched PEI, as described above.

[0102] The method may involve functionalizing the ion exchange membrane support by reacting the surface intermediate layer with a charged functional layer. For example, the method may involve bonding charged functional groups to a chemically immobilized amine layer. Any of the above charged functional molecules can be attached to the membrane support. In certain embodiments, for example, to produce a cation exchange membrane, the method may involve hydrolyzing PEI with a sulfonic acid group, such as a sulfonyl hydroxide. The prepared cation exchange membrane will generally have a charged functional layer covalently bonded to the ion exchange membrane support. Covalent bonding can provide better selectivity and stability of the ion exchange membrane in use, as described above.

[0103] The monovalent selective ion exchange membranes disclosed herein may have at least 100% counterion selective permeability. For example, the monovalent selective ion exchange membranes disclosed herein may have counterion selective permeability between approximately 100% and 105% or between approximately 100% and 103%. The monovalent selective ion exchange membranes disclosed herein may have an initial selectivity of 8 to 12 times Na / Ca (ppm) at room temperature. The monovalent selective membranes disclosed herein may have a density of approximately 7 Ω-cm 2 Less than, for example, about 5 Ω-cm 2 Less than approximately 2-7 Ω-cm 2 Between, or approximately 3-5Ω-cm 2 It may have resistivity between [values].

[0104] The functions and advantages of these and other embodiments can be better understood from the following examples. These examples are intended to be illustrative in nature and are not intended to limit the scope of the invention. [Examples]

[0105] Example 1: Preparation of a cation exchange membrane test coupon The following experimental method was used to prepare small coupons for resistivity and counter-ion selective permeability testing, investigating formulation and process effects. Coupons with a diameter of 43 mm were die-cut from a porous membrane substrate. Slightly larger discs (50 mm or 100 mm in diameter) were also die-cut from a transparent polyester sheet. A 105 mm aluminum weighing boat was used to hold the coupon set. The coupons were sandwiched between two polyester film discs.

[0106] First, a template was created by thoroughly wetting the substrate coupon with a monomer solution. This was done by adding the formulated solution to its aluminum boat and then immersing a polyester film disc, on which the substrate coupon was layered, into the solution until the porous support was saturated. Next, the saturated support was removed from the monomer solution and placed on a piece of polyester film. Air bubbles were removed from the coupon by smoothing or squeezing it with a handy tool, such as a small glass rod, or by hand. Next, a second polyester disc was layered on top of the first coupon and smoothed to ensure complete surface contact between the coupon and the lower and upper polyester film layers. Then, a second porous substrate was layered on top of the upper polyester film, and the saturation, smoothing, and addition of upper layers of polyester film were repeated to obtain a multilayer sandwich of two coupons and three protective polyester film layers. In a typical experimental run, there are more than 10 multilayer sandwiches of saturated substrate coupon layers. If necessary, the edges of the aluminum boat were crimped to hold the disc / coupon assembly in place.

[0107] The sample, including the boat and coupon assembly, was placed in an 80°C oven for up to 30 minutes. The bag was then removed and cooled, and the reacted cation exchange membrane coupon was placed in a 0.5N NaCl solution at 40°C–50°C for at least 30 minutes, with up to 18 hours of NaCl immersion proving sufficient.

[0108] The method described was suitable for preparing cation exchange membrane test coupons.

[0109] Example 2: Monovalent selectivity of cation exchange membranes To evaluate the selectivity between monovalent and polyvalent ions, a solution containing 0.15 M NaCl and 0.15 M CaCl2 was used to supply the dilute compartment. A 0.30 M KNO3 solution was supplied to the concentrate and the two electrodes. The dilute stream was a 150 ml sample reservoir with a total volume of approximately 75 ml. The concentrate stream (0.3 M KNO3) was 1000 ml of solution to ensure a very slight increase in concentration. Typically, the experiment lasted 3 hours with a flow rate of 7 cm³. 2 For the film sample, 25% salt removal can be achieved at 70mA.

[0110] The current density is 100 A / m². 2 The three streams were circulated by three peristaltic pumps, each with a nominal pumping speed of 200 ml / min. The dilute streams were sampled for ion chromatography (IC) analysis. Each sample taken was 100.0 μl and diluted to 50 ml for analysis. Typically, 4 to 6 samples were taken through each membrane experiment. Sample removal did not affect the total volume of the dilute stream. In most cases, water loss was minimal due to the small concentration difference between the concentrated and dilute streams. Volume adjustment was not required for IC analysis samples.

[0111] Conventional cation exchange membrane Figures 4A-4B show the Ca in the dilute stream over time (seconds) during desalination using two conventional membranes, as described in the experimental procedure above. 2+and Na + This is a graph of the molar amount (moles / L) of ions. The graph shows the selectivity (moles / L) of Ca / Na. 2+ and Na + The molar transport ratio between them was approximately 2 in conventional cation exchange membranes. This result is mainly due to the charge effect. Ca 2+ Because the ion charge is large, Na + It moves through the film and into the electric field faster than Ca. However, as the slope of the line indicates, 2+ Ions and Na + Both ions were successfully removed.

[0112] Monovalent selective cation exchange membrane A monovalent selective cation exchange membrane having a PEI with a molecular weight of 600 g / mol, prepared by the method disclosed herein (for example, as described in Example 5 below), was tested as described above. The results are shown in the graph in Figure 5. In short, Ca2 2+ / Na + The selective permeability of Ca was 11. Therefore, 2+ Compared to the conventional, unmodified membrane described above, transport was 22 times slower. Therefore, the monovalent selective cation exchange membrane described herein offers increased selective permeability compared to conventional cation exchange membranes.

[0113] Example 3: Preparation of membrane test coupons A porous polyethylene (PE) film (24 or 34 μm thick) was immersed in a styrene (ST) / divinylbenzene (DVB) / N-methyl-2-pyrrolidone (NMP) solution for 0.01 to 4 hours to prepare a film. A polymerization initiator was added to the mixture to adjust the ST:DVB:NMP composition to 7:1:2 (by mass). The PE film was saturated with the solution and placed between two Mylar sheets. Air bubbles between the Mylar sheets were removed. Additional solution was added to avoid "white areas" due to evaporation of the solution after prolonged exposure. The film was heated to approximately 80-90°C for 1 to 4 hours. Typical film dimensions for such experiments are 4 × 15 inches.

[0114] The prepared film was cut into 1.5-inch disk coupons. The coupons were immersed in a ClSO3H / CH3Cl solution with a composition of ClSO3H:CH3Cl in a ratio of 1:2 (volume) at 4°C for 24 hours. The film was removed from the solution and rinsed with NMP and methanol. The rinsed film was then dried on a napkin and considered ready for further processing and testing.

[0115] The resistance of such films is typically 2500 Ω-cm. 2 Therefore, it does not exhibit selective permeability. The reported resistance exceeded the instrument's measurement.

[0116] Example 4: Preparation of a cation exchange membrane from the membrane test coupon in Example 3 The membrane test coupon from Example 3 was processed to produce a cation exchange membrane test coupon.

[0117] After drying with a napkin, the film was placed in a 1N NaOH solution for approximately 15 minutes. The film was removed from the NaOH solution, rinsed with water, and prepared in a 0.5M NaCl solution.

[0118] The film has a resistance of 1.8 to 3 Ω-cm. 2 The selective permeability of counterions was 101% to 104%.

[0119] Example 5: Surface modification of the cation exchange membrane test coupon from Example 4 The cation exchange membrane test coupon from Example 4 was functionalized to prepare monovalent and polyvalent selective cation exchange membrane test coupons.

[0120] After drying with a napkin, the film was left in a PEI aqueous solution overnight (approximately 15 hours). The pH of the PEI solution was tested to be between 8 and 12.6. The film was removed from the PEI solution and rinsed with water. The film was immersed in a 1N NaOH solution for 15-22 minutes to confirm that most of the SO2Cl groups on the substrate had been completely converted to SO3Na.

[0121] The film surface was modified with PEI polymer molecules, and various tests were performed. The film had a resistance of 2.8 to 7 Ω-cm. 2The selective permeability of counterions was 100% to 103%.

[0122] Example 6: Groundwater Improvement Typical groundwater contains 800 ppm of Na. + , 250 ppm Ca 2+ 50 ppm Mg 2+ Sample water containing these elements was prepared. In reality, groundwater exhibits significant variations in these three cations. The composition tested in this specification was an average value.

[0123] The sample groundwater was treated with the monovalent selective cation exchange membrane described in Example 5 and the conventional cation exchange membrane described in Example 3. The results are shown in the graphs in Figures 6A and 6B. + Ca 2+ , and Mg 2+ Ion concentrations were measured. Sodium adsorption rate (SAR) was also measured. SAR is an important indicator of water hardness requirements for water used in irrigation.

[0124] In short, the results show that the monovalent selective membrane in Example 5 can reduce the SAR value of treated water to 3. In comparison, the cation exchange membrane in Example 3 removes all ions, increasing the SAR value by removing polyvalent ions. Therefore, the monovalent selective membranes described herein can lower the SAR value of treated groundwater.

[0125] Example 7: Treatment of seawater Seawater was treated to remove hardness using a monovalent selective cation exchange membrane as described in Example 5. Removing hardness from seawater can be important for many processes, including the production of hypochlorite, oil extraction, and table salt. The results are shown in Figure 7. Specifically, the time course of Mg in a dilute stream. 2+ Ca 2+ , and Na + The graph in Figure 7 shows the change in ion concentration. Simply put, Mg 2+ and Ca 2+ The concentration of Na remains relatively constant, +The concentration of ions decreases. Therefore, using the monovalent selective membrane described herein, the Na in seawater decreases. + It is possible to lower the ion concentration.

[0126] Example 8: Stability of monovalent selective cation exchange membranes The monovalent selective cation exchange membrane from Example 5 was immersed in a 0.5 M NaCl solution at room temperature. A conventional cation exchange membrane with physically adsorbed PEI was also tested. Figure 8 is a graph of the change in membrane selective permeability over time. In short, after 150 days of immersion, the monovalent selective membrane became Na + Ion vs. Ca 2+ The monovalent selectivity membrane exhibits a selective permeability of over 9 for ions. This monovalent selectivity membrane has higher selectivity than conventional commercially available products and shows significant stability over time. Therefore, the monovalent selectivity membrane has superior selectivity and a longer service life compared to conventional membranes, and remains stable even after long-term use.

[0127] Example 9: Performance investigation of monovalent selective cation membranes The performance of a monovalent selective cation membrane was measured over 7 cm. 2 The surface area of ​​the membrane coupons was investigated under laboratory conditions. Selectivity was determined using a lab ED module (shown in Figure 9) containing dilute and concentrate compartments. The solutions in these compartments were circulated independently via a peristaltic pump with a K2SO4 electrolyte circulating between the anode and cathode compartments. The dilute stream had a total volume of approximately 75 ml, and its ionic components were monitored by ion chromatography (IC). Both the cation exchange membranes and anion exchange membranes used in the tests exhibited high coionic exclusivity with 98% preferential transport of counterions. Current densities were selected to avoid operating beyond the limiting current.

[0128] Synthetic groundwater composition (800 ppm Na + , 260 ppm Ca 2+ 76 ppm Mg 2+ Using (which has), 30 A / m 2The selectivity of the monovalent selective cation exchange membrane was tested at the current density. Figures 10A and 10B show the concentration of the target cation in the dilute compartment over time. Figure 10B shows the decrease in all cation concentrations by passing through the nonselective membrane, while Figure 10A shows the dilution of Na by the monovalent selective cation exchange membrane. + Only the following is shown. Figures 10C and 10D show the concentration of the target cation in the dilute compartment over time in mol / L.

[0129] The recovery of sea salt will also be demonstrated through experiments. The dilution compartment contains the main ions of seawater diluted to 500 ppm TDS (17000 ppm Cl). - , 2800 ppm SO4 2- , 9000 ppm Na + , 1200 ppm Mg 2+ , and 300 ppm Ca 2+ The initial solution includes ). Figures 11A and 11B show a monovalent selective anion exchange membrane and 300 A / m². 2 This shows the concentration of selected ions in a concentration compartment using a monovalent selective cation exchange membrane with an applied current density of . The blue squares represent the concentrations of major ions in the original seawater.

[0130] The graph clearly shows the increase in chloride (Figure 11A) relative to sulfate and sodium (Figure 11B) relative to calcium concentrations in the concentration compartment over time. The combination of monovalent selective anion and cation exchange membranes demonstrates applicability for recovering sea salt from seawater using ED processes with both membranes. Furthermore, a combination of non-selective and monovalent selective membrane cell pairs can be used to generate ionic compositions specifically targeted in the EDR-generated water.

[0131] Figures 12A and 12B show a comparison of the initial selectivity and lifetime selectivity (stability) of conventional / commercial monovalent selectivity membranes and the monovalent selectivity membranes disclosed herein. The selectivity in Figures 12A and 12B is expressed as the ratio of the change in sodium ion concentration to calcium ion concentration on a parts per million (ppm) or molar (M) concentration scale.

[0132] Conventional / commercially available membranes were fabricated by methods including physical adsorption of PEI. Figure 12A shows membrane selectivity at immersion time in a 0.5 M NaCl solution at a temperature of 80°C. Results were estimated using temperature corrections previously derived from experiments on Arrhenius plots with a slope of 2.5 / 10°C. As shown in accelerated testing, the loss of selectivity in the monovalent cation-selective membranes disclosed herein decreases considerably over time compared to conventional membranes. Furthermore, by extrapolating the lifetime from high temperatures to normal operating temperatures (as shown in Figure 12B), the allowable lifetime of the monovalent cation-exchange membranes disclosed herein is determined by the high selectivity of monovalent cations to divalent cations.

[0133] Example 10: Use of monovalent selective cation exchange membranes Examples of how the monovalent selective cation exchange membranes disclosed herein may be used in water treatment systems are described below. The water quality of the EDR product and the rejected water was modeled using in-house finite element analysis (FEA) projection software for monovalent selective cation exchange membranes. The scaling index (SI) of the rejected water was calculated using PHREEQC software (a computer program written in the C++ programming language designed to perform various aqueous geochemical calculations) with various instantaneous EDR recoveries. The results were compared with field data from non-selective EDR installations and FEA models.

[0134] Application 1: Minimizing industrial water brine In many industrial applications, reverse osmosis (RO) is used to produce low-salinity water. While RO systems often have low and limited recovery rates due to potential scale formation, brine disposal can be a costly part of the overall process. Using monovalent selective cation exchange membrane EDRs (Endostatic Drip Reservoirs) to process brine and achieve emission limits can significantly reduce disposal costs.

[0135] One comparative application site operates RO with a 75% recovery rate on a reject stream TDS of 2297 mg / L. Without further processing, 25% of the total feed flow rate would need to be disposed of as brine waste. By employing non-selective EDR, this brine can be reduced to 5.7% of the feed flow rate. Monovalent selective cation exchange membranes can further reduce brine waste to 3.2% of the feed flow rate by increasing the recovery rate of the EDR process from 82% to 90%, before the risk of CaCO3 scale precipitation occurs. Table 1 shows the main ion concentrations in the stream from field tests and monovalent selective cation exchange membrane modeling, and the SI of CaCO3 at maximum EDR recovery.

[0136] [Table 1]

[0137] Application 2: Discharge of generated water The processes used to harvest oil and gas sometimes produce "product water," which presents environmental challenges in terms of treatment. An EDR system was tested at a product water facility where desalination is a key component of the treatment process. The sample water contains high concentrations of silica, which limits pressure-driven membrane recovery.

[0138] In the EDR pilot study, while reducing TDS from 8587 mg / L to 2107 mg / L in the first stage of the two-step process, an instantaneous recovery of 88% was observed, but higher recovery could not be achieved due to the potential formation of BaSO4 scale. By applying selectivity from a monovalent selective cation exchange membrane, the same TDS reduction can be achieved while operating at an expected recovery rate of 98%. Table 2 shows the stream analysis of the product and concentrates predicted at a recovery rate of 97%.

[0139] [Table 2]

[0140] Application 3: Agricultural Desalination To reduce the burden on freshwater sources for agricultural use, alternative sources of brackish water quality should be considered. While some crops, such as barley and cotton, are more tolerant of saline conditions, constant use of brackish water generally leads to salt buildup in the soil, negatively impacting yields as freshwater cannot adequately leach the salt. Even more caution is needed for saline-sensitive crops, including fruit trees, which often require desalination.

[0141] In addition to overall salinity, cation concentration can have various effects on soil structural stability. This effect can be expressed by the sodium adsorption ratio (SAR) and the cation ratio of structural stability (CROSS). The impact of these parameters on agricultural yield depends on the specific crop and salinity, but lower SAR or CROSS values ​​generally indicate higher soil stability. The formulas for SAR and CROSS are shown below.

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[0142] Monovalent selective cation exchange membrane EDRs can selectively remove sodium and potassium more than calcium and magnesium. As a result, they may be suitable for reducing TDS in agricultural applications and maintaining low SAR values. In particular, monovalent selective cation exchange membrane EDRs maintain low SAR values ​​across the entire range of product TDS concentrations with low energy consumption and without additional process steps, as is required for many crops.

[0143] The sample brackish water feed was modeled using non-selective EDR and monovalent-selective EDR with the same product TDS. Product ion concentrations are shown in Table 3. The SAR value for monovalent-selective cation exchange-generated water was 0.16, compared to 6.59 for the non-selective process.

[0144] [Table 3]

[0145] Therefore, the monovalent selective cation exchange membranes disclosed herein are suitable for applications such as minimizing industrial water brine, discharging generated water, and agricultural desalination.

[0146] The expressions and terminology used in this book are for illustrative purposes only and should not be considered limiting. Where used herein, the term “plural” refers to two or more items or elements. The terms “contains,” “carries,” “has,” “includes,” and “includes” are open-form terms, whether in written descriptions or claims, meaning “contains but not limited to these.” Therefore, the use of such terms implies encompassing the items listed thereafter, their equivalents, and any additional items. With respect to claims, only the transitional phrases “consist of” and “essentially become from” are closed or semi-closed transitional phrases, respectively. The use of common terms such as “first,” “second,” and “third” in claims to modify claim elements does not, by itself, imply priority, rank, or a temporary order in which the operation of one claim element over another is performed, but is used solely as labels to distinguish claim elements, to differentiate one claim element having a particular name from another element having the same name (other than the use of ordinal terminology).

[0147] Having described several aspects of at least one embodiment, it should be understood that various changes, modifications, and improvements will readily arise for those skilled in the art. Any feature described in any embodiment may be included in or substituted for any feature in any other embodiment. Such changes, modifications, and improvements are intended to be part of this disclosure and within the scope of the invention. Accordingly, the foregoing description and drawings are merely examples.

[0148] Those skilled in the art will understand that the parameters and configurations described herein are illustrative, and that actual parameters and / or configurations will depend on the specific application in which the disclosed methods and materials are used. Those skilled in the art should also be able to identify or verify equivalents to the specific embodiments disclosed using only routine experiments.

Claims

1. Polymer microporous substrate; A crosslinked ion transport polymer layer on the surface of the polymer microporous substrate; and Electrostatically functionalized intermediate layer covalently bonded to the aforementioned crosslinked ion transport polymer layer Includes, The polymer microporous substrate comprises at least one of high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE), The electrostatically functionalized intermediate layer has a bonding group configured to covalently bond the electrostatically functionalized intermediate layer to the crosslinked ion transport polymer layer; the bonding group is a group derived from the polymerization of styrene and a group derived from the polymerization of divinylbenzene. The aforementioned electrostatically functionalized intermediate layer is a positively charged electrostatically functionalized intermediate layer. The positively charged functionalized intermediate layer comprises a sulfonic acid group and a branched polyethyleneimine (PEI) having a molecular weight of at least 600, in a monovalent selective cation exchange membrane.

2. The monovalent selective cation exchange membrane according to claim 1, wherein the monovalent selective cation exchange membrane has a total thickness of 20 μm to 155 μm.

3. The monovalent selective cation exchange membrane according to claim 2, wherein the monovalent selective cation exchange membrane has a total thickness of 25 μm to 55 μm.

4. A monovalent selective cation exchange membrane according to claim 1, having an initial selectivity of 8 to 12 times Na / Ca (ppm) at room temperature.

5. 5Ω-cm ２ A monovalent selective cation exchange membrane according to claim 1, having a resistivity of less than 1.

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