Embedded-based materials and processes for softening water

Abstract

A device for removing ions from a water stream includes a first electrode and a counter electrode opposite the first electrode in the water stream. The first electrode comprises at least one material capable of embedding one or both of Mg < 2 + > and Ca < 2 + > ions in the water stream. The counter electrode may include a material capable of binding anions in the water stream.

Description

[0001] Priority declaration This application is a utility model application derived from and claims priority to U.S. Provisional Application No. 62 / 760,862, filed on November 13, 2018 and entitled “Intercalation-based materials and processes for softening water,” the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] The present disclosure relates to electrochemical treatment of water, and more particularly to water softening devices incorporating electrode materials configured to intercalate target ions. Background Art

[0003] However, water from traditional safe sources (such as municipal water sources) or drinking water from wells may have a quality that is less desirable to water consumers. For example, water from drinking water sources can vary significantly in taste, odor, turbidity, bacterial and / or viral contamination, heavy metal contamination, hardness, mineral deposits, and / or a combination of these water quality parameters. The quality parameter of water hardness relates to the presence of calcium ions (Ca 2+) in a given volume of water. 2+ ) and / or magnesium ions (Mg 2+ ) concentration. Calcium and / or magnesium are present in drinking water in the form of salts, which are usually soluble in the form of sulfates, carbonates, bicarbonates or chlorides. The soluble salts are usually ionized so that the water contains relatively high concentrations of calcium and / or magnesium ions.

[0004] Water is usually classified as "soft water" or "hard water" according to its hardness. The harder the water, the higher the concentration of calcium and / or magnesium ions per volume. Hard water is usually not desired because it may cause scaling in plumbing systems, fixtures, and appliances, and may affect the performance of these systems and devices. For example, heat from a hot water heater removes some calcium carbonate and magnesium carbonate from the water, resulting in scaling that may slow down the heating process and increase energy use. Cleansers used with hard water are usually less effective. Clothes washed in hard water may become dim and gray over time, and feel rough or itchy. Glassware may become spotted when drying. Films may remain on shower doors or shower curtains, walls, and tubs, and hair washed in hard water may look dull and feel unclean. The process of removing calcium and / or magnesium ions from hard water is usually called water softening.

[0005] There are a variety of existing technologies for removing ions from water, each of which has advantages and disadvantages, which make different technologies more or less desirable for a given application. Reverse osmosis (RO) and modern thermal distillation are effective technologies in comprehensively and non-selectively removing ions (i.e., deionization) from water. Since these technologies remove water from salt, they are most advantageous when the initial ion load is quite high (such as in the case of seawater desalination). However, due to the need for a large amount of energy input, RO and thermal distillation technologies are generally subject to high costs. Another technology for removing ions from water includes electrochemical technologies, such as electrodialysis or electrosorption (i.e., capacitive deionization). These technologies generally use ion exchange membranes and / or high surface area carbons in combination with an applied potential to draw ions out of the water to electrodes and limit desorption to remove ions from the feed water. Therefore, electrodialysis and electrosorption are more attractive for brackish water sources or applications that require partial removal of ions from a water stream.

[0006] The most common technology for municipal water softening is ion exchange. In an ion exchange softening system, the softening device uses ion exchange resins to replace calcium and magnesium ions in the feed water stream with sodium ions when in operation. Although ion exchange systems can recycle slightly more water than CDI systems, and the energy consumption in ion exchange systems is generally lower than when using CDI systems, ion exchange does have some disadvantages. Since calcium and magnesium ions are replaced with sodium ions, softened water may taste salty. In addition, ion exchange systems must be refilled with sodium ions regularly. This requires users to programmatically add salt to the system to maintain system efficiency, which may be a burden to users. In addition, saltwater waste streams in areas with a large amount of hard water may burden local water treatment plants and the environment. Due to this burden, some municipalities have completely banned salt softeners.

[0007] Another technology for removing ions from water includes adding an intercalation body to an electrosorption platform to form a "desalination cell" or similar hybrid system. Adding an intercalation body to an electrosorption platform provides many advantages. For example, a system using an intercalation body can have a higher available capacity than a carbon-based capacitive deionization (CDI) system, which improves efficiency and reduces electrode wear. In addition, because the intercalation body does not rely on high surface area to achieve high capacity, it is less prone to fouling than typical CDI electrodes. In addition, the intercalation compound can be configured to remove specific target ions from the water stream, which is advantageous when the water meets most but not all of the quality standards for a given application.

[0008] Traditionally, the use of embedded hosts in CDI systems has been limited by the lack of availability of materials that can: (1) embed relevant ions, such as sodium ions (Na +); (2) have sufficient capacity in the potential window provided by the aqueous electrolyte; (3) be non-toxic; and (4) have an appropriate cycle life for purifying reasonable amounts of water before electrode regeneration or replacement is required. However, applicants have discovered that water softening is an application well suited for use with an embedded body. Municipal water typically contains greater than optimal concentrations of calcium and magnesium ions, otherwise the water is potable. Therefore, a water treatment or water softening system that utilizes an embedded body to selectively extract only the ions of interest would be the most energy efficient. In contrast, conventional carbon-based CDI systems can be difficult to implement because hard water tends to leave mineral deposits on the surface. In addition, municipal hard water typically contains approximately 200 ppm of divalent cations, which is generally too low to justify energy-intensive purification technologies such as RO or distillation-based technologies.

[0009] What is needed is a suitable intercalation host material for softening water that selectively intercalates the ions of interest, has sufficient capacity within the stability window of the aqueous environment in which the intercalation host material is implemented, is non-toxic, and has a long cycle life. A water softening device comprising at least one electrode with such an intercalation host material would be further advantageous. Summary of the invention

[0010] In one aspect of the present disclosure, a device for removing ions from a water stream is provided. The device includes: a first electrode, the first electrode is connectable to a current source; and a counter electrode, the counter electrode is connectable to the current source and is arranged opposite the first electrode in the water stream. In one feature, the first electrode comprises Mg capable of intercalating into the water stream. 2+ and Ca 2+ ions. The material may be selected from the group consisting of: A x CuFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x MnFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x MnMn(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x ZnFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x BaFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x FeFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x NiFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; Ti x Fe 1-x [Fe(CN)6] 0.960≤x≤1; Polyimide; FePO4; NaMnFe2(PO4)3; Na3Fe3(PO4)4; Na(M)PO4, M=Fe, Mn, or Fe x Mn 1-x 0≤x≤1; MnO2; Na x MnO2, 0≤x≤1; ZnMn2O4; MgFeSiO4 / C; Mg x Mn 2-x SiO4, 0≤x≤2; Mg 0.5 Ti2(PO4)3; LiTi2(PO4)3; Ti x Al 2-x (PO4)3, 0≤x≤2; TiP2O7; Na3MnTi(PO4)3; K2Ti4O9; TiS2; FeS2; CaMO3 (M=Mn and / or Fe); potassium terephthalate; 2,5-pyridinedicarboxylic acid (K2PC); KFeF3; K 0.3 MnO2; KMg x Fe 2-x (PO4)2,0≤x≤2; NaTi2(PO4)3; Na2FeP2O7; TiO2; and Na2Ti3O7.

[0011] In another aspect of the present disclosure, a method for removing ions from a water stream comprises: positioning the device in the water stream; and applying a negative voltage to the first electrode in one operating state to cause ions from the water stream to be embedded into the first electrode. In certain embodiments, a positive voltage is applied to a counter electrode configured to bind anions in the water stream, thereby producing an ion-free water stream discharged from the device. In another operating state, a positive voltage is applied to the first electrode to release the embedded ions back into the water stream to produce a wastewater stream discharged from the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A water softening device according to a first embodiment is depicted, the device comprising an electrode having at least one material configured to intercalate a target cation in a water supply.

[0013] Figure 2 Shows Figure 1 A water softening device in an operating state where voltage is applied to the electrodes and target cations are removed from the water supply via intercalation of the material.

[0014] Figure 3 Shows Figure 1 A water softening device in an operating state in which the voltage applied to the electrodes is reversed and target cations are released into the wastewater stream.

[0015] Figure 4 Draws Figures 1 to 3 A cartridge embodiment of the device is shown in , wherein the cartridge is supported within a housing that is integrated into the water supply system of a residence or building.

[0016] Figure 5 A water softening device according to a second embodiment is depicted, the device being shown in a first operating state in which a voltage is applied to a first electrode having a first material and to a second electrode having a second material, the first material being configured to embed target cations from a water supply, and the second material being configured to release the target cations to a wastewater stream.

[0017] Figure 6 Shows Figure 5 The water softening device is in a second operating state in which the voltage polarity is reversed, the first material is configured to release the target cation to the wastewater stream, and the second material is configured to embed the target cation from the water supply.

[0018] Figure 7 Draws Figures 5 to 6 A cartridge embodiment of the device is shown in , wherein the cartridge is supported within a housing that is integrated into the water supply system of a residence or building. DETAILED DESCRIPTION

[0019] For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the accompanying drawings and described in the following written specification. It should be understood that no limitation of the scope of the present disclosure is thereby intended. It should also be understood that the present disclosure includes any changes and modifications to the illustrated embodiments, and includes additional applications of the principles of the present disclosure as would normally occur to a person skilled in the art to which the present disclosure belongs.

[0020] Figures 1 to 3 A first embodiment of an apparatus 100 for softening water is depicted. The apparatus 100 includes at least one electrode 104 and a counter electrode 136. The electrode 104 may have a substrate 108, wherein at least one material 112 is disposed on the substrate 108. In one embodiment, the substrate 108 is a metal substrate. The material 112 on the substrate includes an intercalation host material configured to intercalate one or more first target ions 116 from a water stream 120. In the illustrated embodiment, the intercalation host material 112 may be configured to intercalate a divalent cation Ca as the first target ion. 2+ and Mg 2+ One or both of the first target ions 116, although in other embodiments, the first target ions 116 may be other target ions. The water stream 120 may also include other cations and anions.

[0021] The embedded host material 112 of the electrode 104 disclosed herein is one or more of the compounds identified in Table 1 below: Table 1 In one embodiment, the electrode 104 includes a material 112 disposed on a substrate 108, a carbon additive for improving conductivity, and a binder, wherein the material 112 includes one or more of the embedded host materials from Table 1. In a specific embodiment, the embedded host material is provided in an amount of 60-85 wt%, the carbon additive is provided in an amount of 3-10 wt%, and polyvinylidene fluoride (PVDF) is provided as a binder in an amount of 5-35 wt%. To produce an electrode 104 having an embedded host material 112, a carbon additive, and a polymer binder, the embedded host material 112, the carbon additive, and the polymer binder are thoroughly mixed as a slurry in a suitable solvent (such as N-methyl-2-pyrrolidone (NMP)), and then it is bladecast, roll cast, or sprayed onto the substrate 108 of the electrode 104.

[0022] In some embodiments, the device 100 is arranged in a water supply system (not shown) of a residence or other building, which includes various pumps, pipes, valves and related components to deliver water from an external water supply to a water distribution branch circuit within the residence or building. The water flow 120 enters the device 100 at an input side 124 and leaves the device 100 at an output side 128. The device 100 can be incorporated into a housing having: an inlet at the input side 124 of the device, the inlet being in fluid-tight engagement with an input line connected to an external water supply; and an outlet at the output side 128 of the device, the outlet being in fluid-tight engagement with an inlet of a water distribution branch circuit.

[0023] As water moves through the device 100 in a flow direction 132 and over the intercalated host material 112 on the electrode 104 , the device 100 is configured to have different operating states to enable it to selectively remove the first target ion 116 from the water stream 120 . Figures 1 to 3 The flow direction 132 shown in FIG. 1 is for reference only and may be reversed in other embodiments. If the flow direction is reversed, the positions of the input side 124 and the output side 128 of the device will also be reversed.

[0024] Figure 1The device 100 is shown in a first operating state in which no voltage is applied to the electrodes 104 while water 120 is flowing through the device 100. In this first operating state, the embedded host material 112 of the device 100 has little effect on the ions in the water, so the water 120 does not change as it enters the input side 124 and leaves the output side 128. Likewise, the embedded host material 112 also has little effect on the ions when water 120 is not flowing through the device.

[0025] Figure 2 The device 100 is shown in a second operating state in which a negative voltage 130 is applied to the electrode 104 while water 120 flows through the device 100 in a flow direction 132. In the second operating state, the first target ion 116 is intercalated into the intercalation host material 112. When the device is operated in the second operating state, the water leaving the output side 128 of the device 100 will contain a lower concentration of the first target ion 116 than the water entering the input side 124 of the device 100. In the second operating state, the first target ion 116 is a divalent cation Ca 2+ and Mg 2+ In one or both embodiments, the water 120 exiting the device 110 will be softened water. The second operating state of the device 100 is sometimes referred to as a "purification cycle" because the removal of the first target ions 116 purifies the water stream exiting the device 100.

[0026] Figure 3 The device 100 is shown in a third operating state in which the voltage polarity is reversed and a positive voltage 130' is applied to the electrode 104 as the water 120 flows through the device in a flow direction 132. In the third operating state, the first target ions 116 are released from the intercalated host material 112 back into the water 120 flowing through the electrode 104. The water 120 that leaves the output side 128 of the device 100 when the device is operated in the third operating state is often referred to as a wastewater stream because it will contain a higher concentration of the first target ions 116 than the water entering the input side 124 of the device. The third operating state of the device 100 is sometimes referred to as a "regeneration cycle" because the intercalated host material 112 is cleared of the first target ions 116 in preparation for a subsequent purification cycle.

[0027] The voltage applied to the electrode 104 in the second and third operating states is configured to be within the stability window of water (i.e., -0.401 to +1.23 V relative to SHE) in order to avoid water electrolysis. Thus, the intercalation host material 112 identified in Table 1 is configured to intercalate and release the first target ion 116 at a voltage within the stability window of water.

[0028] Continue to refer Figures 1 to 3, in some embodiments, the second electrode 136 is configured to remove second target ions 144. The second electrode 136 is spaced apart from the first electrode 104 on an opposite side of the water flow path 120. In the illustrated embodiment, the first and second electrodes are directly opposite each other in the flow path; however, the electrodes may be offset from each other in the flow direction 132. In one embodiment, the second electrode 136 may be configured as a high surface area carbon counter electrode. In some embodiments, the device 100 also includes at least one ion selective membrane 140 disposed between the second electrode 136 and the water 120. The ion selective membrane 140 is configured to allow the second target ions 144 to pass through and increase the resistance to the adsorption of the common ions. In some embodiments, the device 100 may include a permeable water separator 141 (see Figure 2 ), which prevents electrical contact between the electrodes. Separator 141 can be a nylon mesh or other non-conductive, non-toxic material. When paired with electrode 104, second electrode 136 is configured in at least one operating state to selectively remove one or more second target ions 144 from water 120 via electrosorption to pass through ion exchange membrane 140 to porous carbon layer 148. In the illustrated embodiment, second target ions 144 can be anions Cl - or CO3 2- , but in other embodiments, the second target ion 144 may be other target ions.

[0029] When the device 100 is in a Figure 1 In the first operating state shown in FIG. 1 , no voltage is applied to the second electrode 136 while the water 120 is flowing through the device 100. In this first operating state, the second electrode 136 has little effect on the ions in the water 120, so the water is unchanged as it enters the input side 124 and leaves the output side 128. Likewise, the second electrode 136 also has little effect on the ions in the water 120 when the water is not flowing through the device.

[0030] When the device 100 is in a Figure 2 , a positive voltage 130′ is applied to the second electrode 136 as the water 120 flows through the device in the flow direction 132. In the second operating state, the second target ions 144 accumulate at the second electrode 136. When the device is operated in the second operating state, the water leaving the output side 128 of the device 100 will contain a lower concentration of the second target ions 144 than the water entering the input side 124 of the device 100. In this second operating state, a negative voltage is applied to the first electrode 104 to embed the first target ions 116, as described above.

[0031] When the device 100 is in a Figure 3In the third operating state shown in , the voltage polarity is reversed, and a negative voltage 130 is applied to the second electrode 136 when the water 120 flows through the device in the flow direction 132. In the third operating state, the second target ion 144 is released from the second electrode 136 back into the water 120 flowing through the electrode 136. The water leaving the output side 128 of the device 100 when the device is operated in the third operating state will generally contain a higher concentration of the second target ion 144 than the water entering the input side 124 of the device 100. The voltage applied to the second electrode 136 in the second and third operating states is configured to be within the stability window of the water (i.e., -0.401 to +1.23 V relative to the SHE) in order to avoid water electrolysis. As described above, in this third operating state, a positive voltage is applied to the first electrode 104 to release the first target ion 116.

[0032] In some embodiments, electrode 104 may be paired with one or more auxiliary electrodes that react reversibly with other ions. For example, the auxiliary electrodes may be formed of a material that reacts reversibly with chloride ions, such as Ag / AgCl or BiOCl.

[0033] In one embodiment, the device 100 may be provided in the form of a cartridge 150 mounted within a housing 152, such as Figure 4 . The housing 152 includes an inlet fitting 153 adapted to be fluid-tightly coupled to a water inlet from an external water source, an outlet fitting 154 adapted to be fluid-tightly coupled to an inlet of a water distribution branch circuit of a residence or building, and an interior chamber 155 in which the cartridge 150 is received. The cartridge 150 may be replaceable. The housing 152 includes a controller 160 electrically connected to a current source V IN and electrically connected to electrodes 104, 136 through respective electrical conductors 105, 137. The controller 160 is configured and operable to selectively energize the two electrodes 104, 136 to achieve each of the three operating states described above for the device 100. The controller may be capable of selectively connecting the two electrodes to a current source V IN In one simple embodiment, the controller is a three-position switch that allows an operator to selectively place the device 100 in any of the three states. However, the controller 160 may incorporate a clock and / or timer that activates each of the three operating states according to a specific schedule. The controller may also be programmable or configured to activate any of the three operating states based on specific conditions in the water supply or based on water usage.

[0034] Figure 5 and Figure 6A second embodiment of a device 200 for softening water is shown. The device 200 includes two porous electrodes 204, which are connected to a reference electrode 204. Figures 1 to 3 The electrodes 104 described are configured in substantially the same manner. Therefore, the two electrodes 204 of the device 200 each include an embedded host material 112 (Table 1), and the embedded host material 112 is configured to embed the first target ion 116 from the water supply 120. The device 200 also includes an ion exchange membrane 240 arranged between the two electrodes 204. In the illustrated embodiment, the ion exchange membrane is an anion exchange membrane 240, which promotes the separation of the first target ion 116 to the first region 250 occupied by one of the electrodes 204 of the device 200 and the second region 254 occupied by another of the electrodes 204 of the device 200. The anion exchange membrane 240 is configured to allow other ions (such as the second target ion 144) to freely pass through the anion exchange membrane between the first and second regions. The configuration of the device 200 with two electrodes 204 and an anion exchange membrane 240 eliminates the need for the dedicated electrode for accumulating anions.

[0035] In some embodiments, the device 200 is arranged in a water supply system (not shown) that includes various pumps, pipes, valves, and related components to transport water from a water source to an end user. The device 200 is arranged in the water supply system so that water 120 enters the device 200 at an input side 224 and leaves the device 200 at an output side 228. As the water moves through the device 200 along the flow direction 232 and moves over the embedded host material 112 on the electrode 204, the device 200 is configured to have different operating states so as to enable it to selectively remove the first target ion 116 from the water 120.

[0036] Figure 6 The device 200 is shown in a first operating state in which a voltage is applied to the electrode 204 while water 120 flows through the device 200 in a flow direction 232. Figure 4As shown in FIG. 2 , a positive voltage 230 is applied to the electrode 204 in the first region 250, while a negative voltage 230′ is applied to the electrode 204 in the second region 254. In the first operating state, the first target ions 116 are intercalated into the intercalation host material 112 of the electrode 204 in the second region 254, which reduces the concentration of the first target ions 116 in the second region 254. Conversely, the first target ions 116 are released from the intercalation host material 112 of the electrode 204 in the first region 250, which increases the concentration of the first target ions 116 in the first region 250. The increased concentration of the first target ions 116 in the first region 250 also has the effect of causing the transfer of the second target ions 144 from the second region 254 to the first region 250, thereby reducing the concentration of the second target ions 144 in the second region 254. Due to the separation of the first target ions 116 and the second target ions 144 in the first operating state, the water 120 exiting the device 200 from the second region 254 will be softened water, while the water exiting the device 200 from the first region 250 will constitute a wastewater stream.

[0037] Figure 7 The device 200 is shown in a second operating state in which the voltages applied to the electrodes 204 are reversed. In particular, a negative voltage 230' is applied to the electrodes 204 in the first region 250, while a positive voltage 230 is applied to the electrodes 204 in the second region 254. In the second operating state, the first target ions 116 are intercalated into the intercalation host material 112 of the electrodes 204 in the first region 250, which reduces the concentration of the first target ions 116 in the first region 250. Conversely, the first target ions 116 are released from the intercalation host material 112 of the electrodes 204 in the second region 254, which increases the concentration of the first target ions 116 in the second region 254. The increased concentration of the first target ions 116 in the second region 254 also has the effect of causing a transfer of the second target ions 144 from the first region 250 to the second region 254, thereby reducing the concentration of the second target ions 144 in the first region 250. Due to the separation of the first target ions 116 and the second target ions 144 in the second operating state, the water 120 exiting the device 200 from the first region 250 will be softened water, while the water exiting the device 200 from the second region 254 will constitute a wastewater stream.

[0038] The device 200 may be provided as a cartridge 201 mounted within a housing 260 configured to be integrated into a water supply system of a residence or building in a manner similar to the housing 152 described above. However, since the device 200 includes two discrete regions 250, 254 that alternate between a softened water flow path and a waste flow path, the housing 260 defines two discrete chambers 261, 265, each having a respective inlet fitting 262, 266 and an outlet fitting 263, 267. The housing is configured to maintain the integrity of the two chambers and regions 250, 254 to prevent cross contamination. A controller 268 is provided that is connected to a current source V IN And connected to each of the electrodes 204 to selectively apply positive voltage, negative voltage or no voltage to the electrodes according to one of the three operating states described above. Since the two regions alternately cause softened water and waste water to flow through them, the outputs of the two chambers 261, 265 of the housing are fed to a two position valve assembly 270 according to the operating state. The first element 271 of the valve assembly provides a direct connection 271a between the left chamber 261 and the waste outlet W, and a direct connection 271b between the right chamber 265 and the soft water outlet S. The second element 272 of the valve assembly spans the connection, thereby providing a direct connection 272a between the left chamber 261 and the softened water outlet S, and a direct connection 272b between the right chamber 265 and the waste outlet W. A valve controller 273 (such as a solenoid valve) is provided to selectively move the valve assembly into one of the two positions. The valve controller 273 is connected to the controller 268, which selectively energizes the electrode 204 for each operating state so that the operation of the electrode is coordinated with the operation of the valve assembly. Figure 5 In the second operating state shown in FIG. 1 , the valve assembly is activated to position the first element 271 between the outlet of the housing and the waste outlet W and the softened water outlet S, as shown in FIG. Figure 7 When the controller 268 activates the device in the third operating state, the valve controller 273 activates the valve assembly so that the second element 272 is aligned between the housing outlets 263, 267 and the waste outlet W and the softened water outlet S.

[0039] Although the present disclosure has been shown and described in detail in the drawings and foregoing description, it should be considered illustrative rather than restrictive in nature. It should be understood that only preferred embodiments have been presented and that all changes, modifications and additional applications that fall within the spirit of the present disclosure are desired to be protected.

Claims

1. A device for removing ions from a water stream, comprising: a first electrode connectable to a source of electric current and configured to be disposed in a water flow; a counter electrode connectable to the current source and configured to be arranged in the water flow opposite the first electrode; as well as a non-conductive water-permeable separator arranged to be disposed in the water flow between the first electrode and the counter electrode, The first electrode comprises a MgO2 electrode disposed on a metal substrate and capable of being embedded in the water flow. 2+ and Ca 2+ ions, wherein the at least one material is selected from the group consisting of: polyimide; MgFeSiO4 / C; Mg x Mn 2-x SiO4, 0≤x≤2; potassium terephthalate; 2,5-pyridinedicarboxylic acid (K2PC).

2. The device of claim 1, wherein the counter electrode comprises a material capable of causing anions in the water stream to bind to the counter electrode.

3. The device according to claim 2, wherein the counter electrode material is capable of making Cl in the water flow - and CO3 2- One or both of the anions are bound to the counter electrode. The device of claim 3 , wherein the counter electrode material comprises a porous carbon layer.

5. The apparatus of claim 2, wherein the counter electrode comprises an ion selective membrane disposed on the counter electrode between the counter electrode material and the aqueous flow.

6. The device of claim 1, wherein the counter electrode comprises Mg capable of intercalating into the water flow. 2+ and Ca 2+ ions or at least one material of one or both.

7. The device according to claim 6, wherein the at least one material of the counter electrode is selected from the group consisting of: A x CuFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x MnFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x MnMn(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x ZnFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x BaFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x FeFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; A x NiFe(CN)6(A=Li, Na, K, Cs)0≤x≤1; Ti x Fe 1-x [Fe(CN)6] 0.96 0≤x≤1; Polyimide; FePO4; NaMnFe2(PO4)3; Na3Fe3(PO4)4; Na(M)PO4, M=Fe, Mn, or Fe x Mn 1-x 0≤x≤1; MnO2; Na x MnO2, 0≤x≤1; ZnMn2O4; MgFeSiO4 / C; Mg x Mn 2-x SiO4, 0≤x≤2; Mg 0.5 Ti2(PO4)3; LiTi2(PO4)3; Ti x Al 2-x (PO4)3, 0≤x≤2; TiP2O7; Na3MnTi(PO4)3; K2Ti4O9; TiS2; FeS2; CaMO3 (M=Mn and / or Fe); potassium terephthalate; 2,5-pyridinedicarboxylic acid (K2PC); KFeF3; K 0.3 MnO2; KMg x Fe 2-x (PO4)2, 0≤x≤2; NaTi2(PO4)3; Na2FeP2O7; TiO2; and Na2Ti3O7.

8. The device of claim 1, further comprising an ion exchange membrane between the first electrode and the counter electrode.

9. The device of claim 8, wherein the ion exchange membrane is an anion exchange membrane.

10. The device according to claim 8, wherein the ion exchange membrane is a cation exchange membrane.

11. The device of claim 1, wherein the first electrode comprises: Conductive substrate; and a layer on the substrate, the layer comprising the at least one material, a conductive additive, and a binder.

12. The device of claim 11, wherein the conductive additive is a carbon composition.

13. The device of claim 11, wherein the binding agent is polyvinylidene fluoride (PVDF).

14. The device of claim 13, wherein the layer comprises 60-85 wt% of the at least one material, 5-35 wt% of the PVDF binder, and 3-10 wt% of a carbon composition as the conductive additive.

15. A method for removing ions from a water stream, comprising: Positioning a device in the water flow, the device comprising a first electrode, a counter electrode opposite the first electrode, and a non-conductive water-permeable separator, the non-conductive water-permeable separator being arranged to be disposed in the water flow between the first electrode and the counter electrode, wherein the first electrode comprises Mg disposed on a metal substrate and capable of intercalating into the water flow 2+ and Ca 2+ at least one material of one or both of the ions; A negative voltage is applied to the first electrode to cause the Mg 2+ and Ca 2+ One or both of the ions are embedded in the first electrode, wherein the at least one material is selected from the group consisting of: polyimide; MgFeSiO4 / C; Mg x Mn 2-x SiO4, 0≤x≤2; potassium terephthalate; 2,5-pyridinedicarboxylic acid (K2PC).

16. The method of claim 15, further comprising discharging the Mg 2+ and Ca 2+ ions of one or both of the water.

17. The method of claim 15, wherein the negative voltage is within a stability window of water.

18. The method according to claim 15, further comprising applying a positive voltage to the first electrode to release the Mg embedded in the first electrode from the first electrode. 2+ and Ca 2+ ions or both.

19. The method of claim 18, wherein the positive voltage is within the stability window of water.

20. The method according to claim 18, further comprising making the Mg 2+ and Ca 2+ One or both of the ions are released into the water stream exiting the device.

21. The method of claim 20, further comprising: discharging the Mg 2+ and Ca 2+ The water stream containing one or both of the ions is discharged separately with the Mg removed from the device. 2+ and Ca 2+ ions of one or both of the water.

22. The method of claim 15, wherein: The counter electrode of the device comprises a material capable of binding anions; and The step of applying a negative voltage to the first electrode includes applying a positive voltage to the counter electrode to cause the anions in the water flow to bind to the counter electrode.

23. The method of claim 22, wherein the counter electrode material is capable of causing Cl in the water stream to - and CO3 2- One or both of the anions are bound to the counter electrode.

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