Electrochemical cell, system and method for ion separation and / or recovery from a liquid solution

Abstract

The present invention relates to electrochemical cell, system and method for ion separation and / or recovery from a liquid solution. The electrochemical cell comprises: − a compartment; − a first liquid electrode that is positioned in the compartment and comprises a first current collector, a first membrane, and a first electrode channel between the first current collector and the first membrane that is configured to allow a first electrode flow; − a second liquid electrode that is positioned in the compartment and comprises a second current collector, a second membrane, and a second electrode channel between the second current collector and the second membrane that is configured to allow a second electrode flow; and − a feed flow channel extending between the first and second liquid electrodes and having an inlet and an outlet.

Description

[0001] ELECTROCHEMICAL CELL, SYSTEM AND METHOD FOR ION SEPARATION AND / OR RECOVERY FROM A LIQUID SOLUTION

[0002] The present invention relates to an electrochemical cell for ion separation and / or recovery from a liquid solution. More specifically, such electrochemical cell can be used for separation or purification of selective ions from a liquid, such as water, containing dissolved salts. An example of such liquid is lithium containing water from a lithium mining process. Other examples involve purification of a magnesium rich brine by removing kalium and other components. It will be understood that may applications can be envisaged for separation and / or recovery of selective ions from a liquid solution. These selective ions enable forming of (specific) minerals, for example.

[0003] Conventional systems and methods for electrochemical ion separation and / or recovery involve capacitive deionisation and electrodialysis, for example. One of the problems with these conventional systems and methods is the lack of selectivity towards specific ions. This reduces efficiency and restricts possibilities for further application of the ions, for example for forming (specific) minerals. Also reverse osmosis is used for desalination processes. This process relies on ion-pressure membranes to separate water from dissolved salts. Also this process has limited selectivity for specific ions and is relatively energy intensive, thereby reducing the overall efficiency of the separation / purification process. Capacitive de-ionization is used to adsorb ions with porous electrodes, however, often has limited salt removal capacity.

[0004] The present invention aims at obviating or at least reducing one or more of the aforementioned problems and to enable ion separation and / or recovery from a liquid solution that has an enhanced selectivity, improved efficiency and / or has a better environmental sustainability as compared to conventional systems and methods.

[0005] This objective is achieved with the electrochemical cell according to the invention for ion separation and / or recovery from a liquid solution, wherein the electrochemical cell comprises:

[0006] - a compartment;

[0007] - a first liquid electrode that is positioned in the compartment and comprises a first current collector, a first membrane, and a first electrode channel between the first current collector and the first membrane that is configured to allow a first electrode flow;

[0008] - a second liquid electrode that is positioned in the compartment and comprises a second current collector, a second membrane, and a second electrode channel between the second current collector and the second membrane that is configured to allow a second electrode flow; and

[0009] - a feed flow channel extending between the first and second liquid electrodes and having an inlet and an outlet.The electrochemical cell comprises a compartment that is suitable for housing several components of the cell. These components include the first liquid electrode and the second liquid electrodes. These liquid electrodes each comprise a current collector, a membrane, and an electrode channel that at least extends between the current collector and the membrane. This electrode channel enables the respective electrode flows of the liquid electrodes. A feed flow channel with an inlet and an outlet is provided between the first and second electrodes. This feed flow channel enables the flow of the liquid solution. Preferably, the feed flow channel is defined by a spacer or spacer element that is provided in or to the compartment. In a presently preferred embodiment of the invention the first membrane is a porous membrane. Such porous membrane enables ion selection that is based on the size of the ions. For example, the porous membrane may involve a nanofiltration membrane. Preferably, the second membrane is an anion-exchange membrane that selectively enables passage of specific anions, for example. Also, this anion-exchange membrane substantially blocks cations from passing through the membrane. This enables an effective charging process as the desorption of cations from the redox molecule in the second electrode channel results in the cations being kept in the second electrode channel such that the respective anions can be retracted from the feed flow channel to the second electrode channel. An even more efficient and effective charging process is achieved when the redox molecule is part of / present in the first liquid electrode and / or the second liquid electrode.

[0010] In a presently preferred embodiment according to the invention, the inside of the first liquid electrode and the second liquid electrode are substantially liquid. For this purpose, the inside of at least one of the electrodes is preferably provided with an electrode chamber configured for receiving the first, second, or further liquid respectively. In other words, the first liquid electrode comprising a chamber is configured to receive at least the first electrode flow, and the second electrode liquid is configured to receive at least the second electrode flow. Preferably, the first liquid electrode and / or the second liquid electrode comprises (dissolved) redox molecules.

[0011] In a preferred embodiment according to the invention, the first liquid electrode and the second liquid electrode comprises (dissolved) redox molecules.

[0012] It is noted that the first, second, or further liquid also refers to the first electrode flow, second electrode flow, or further electrode flow respectively.

[0013] The electrode chamber is configured for receiving the first, second, or further liquid in operation. An advantage of said chamber is that the first, second, or further liquid do not interfere / mix with each other.

[0014] A further advantage of the electrochemical cell according to the invention is that selective ion separation can be performed using a single electrochemical cell stack. For example, a feed flow (such as feed water) comprising a dissolved salt solution is in an operational state of the electrochemical cell provided to at least one flow channel of the electrochemical cell. In a non-limiting example, the feed solution comprises lithium carbonate (ITzCCh) brine including impurity ions such as sodium (Na+).

[0015] A charging voltage and / or charging current (said charging voltage and / or charging current may also be referred to as electrical charge) is in the operational state applied across the electrochemical cell (such as by connecting the different liquid electrodes with a supply of electricalcharge), resulting in selective adsorption of ions from the feed flow. During charging, the first liquid electrode selectively adsorbs positive ions, such as sodium ions, while the second liquid electrode selectively adsorbs negative ions, such as carbonate ions (CCh2). As the feed flow flows through the cell during charging, a purified effluent stream depleted of the selectively adsorbed ions is produced at the outlet of the flow channel.

[0016] Following the charging, a discharging voltage and / or current and / or charge is applied to the electrochemical cell to induce desorption of the previously adsorbed ions from the liquid electrodes into a flowing liquid stream. This discharging step produces an effluent stream enriched in the desorbed ions, resulting in a concentrated product stream.

[0017] The charging and discharging are performed cyclically, such that the electrochemical cell alternately produces a purified stream and a concentrated stream. Samples of the effluent streams may be collected for compositional analysis or downstream processing.

[0018] To enable the cell to be charged and discharged cyclically, in a presently preferred embodiment, the cell can be transferred to a different flow and / or the flow can be changed.

[0019] Transferring the cell can be performed with the use of transferring means, such as grippers or can be done manually, preferably with the use of closing valves and / or seals. Changing the fluid (flows) may involve the use of one or more valves that can be controlled automatically with a (valve) controller that is optionally integrated in the (overall) controller or can be done manually.

[0020] In the presently preferred embodiments, there is provided one feed flow channel for a cell. It will be understood that, alternatively, also multiple flow channels can be provided. The electrodes channel(s) preferably comprise(s) electrically conducting porous materials (also referred to as porous conductive material) that are used as spacers and are preferably connected to a power source in an operational mode of the electrochemical cell. The channels for feed flow and electrode flow are preferably both designed to minimise hydraulic resistance and in addition to increase mixing of flows.

[0021] The spacer that is preferably applied in or to the feed flow channel is preferably a non-electrically conducting porous material. In the electrode flow channels the electrically conducting porous material acts as spacer.

[0022] In operation, the electrochemical cell according to the present invention can be operated in a charging mode and in a discharging mode. In a charging mode, a (positive) voltage or current is applied between the first liquid electrode and the second liquid electrode such that electrons flowfrom the second electrode channel to the first electrode channel. As a result, an electrochemical reduction of redox molecules will occur in the first electrode channel, thereby adsorbing cations. The redox molecules in the second electrode channel undergo an electrochemical oxidation reaction involving desorption of cations. Preferably, these cations are substantially blocked by the anion-exchange membrane and anions are attracted from the feed flow channel to the second electrode channel. This results in removal of the cations of dissolved salts, from the feed flow channel. Therefore, cations move towards the first electrode channel and the anions move towards the second electrode channel. This charging can be performed energy efficient such that an effective cation and / or anion separation from the liquid solution is performed.

[0023] It is noted that salt is an ionic compound comprising of an assembly of positively charged ions (cations) and negatively charged ions (anions), which preferably results in a compound with no net electric charge (electrically neutral). The constituent ions are held together by electrostatic forces termed ionic bonds.

[0024] In a discharging mode a reverse electrical charge can be applied between the first and second electrodes or alternatively the first and second electrodes are being switched in an open circuit. In such discharging mode the adsorbed ions are adsorbed from the electrode such that the respective ions can be effectively separated in different selective flows to the respective designated outputs for the purified ions. These selective ions enable forming of (specific) minerals, for example.

[0025] In addition to the selectivity that is provided by the porous membrane in relation to size as a first selectivity criterium and / or the selectivity that is provided by the anion-exchange membrane in relation to charge as a second selectivity criterium, the redox molecule provides further selectivity for the ions as a third selectivity criterium as certain ions are preferred in the adsorption of the respective redox molecule, while other ions being prevented from being adsorbed. This multi-step selectivity improves the overall selectivity of the electrochemical cell for ion separation and / or recovery from a liquid solution. This further improves the possibilities for an effective application of the electrochemical cell in an embodiment according to the present invention in different (potential) applications. Such potential applications include lithium purification that may involve removing of impurities such as sodium, potassium, calcium and / or magnesium from a lithium brine flow and / or by selectively separating lithium from these impurities to produce relatively high purity lithium salts. In another potential application sodium, potassium, and / or calcium can be removed from a magnesium rich brine flow that is often present in magnesium mines, for example. This enables separation and / or purifying of magnesium and improving the purity of the magnesium salts. In a further potential application calcium and / or magnesium are removed from a water flow to reduce mineral scaling in water treatment systems, wastewater treatment plants, and also for dish washer water pretreatments and / or posttreatments. In a further potential application, magnesium, sodium, and / or potassium can be selectively removed from cobalt rich brine flows for purifyingcobalt salts. It will be understood that other potential applications can also be envisaged wherein an electrochemical cell in an embodiment according to the present invention can be used effectively. In a presently preferred embodiment of the invention the electrochemical cell further comprises a power supply, wherein the power supply is operatively coupled with at least the first liquid electrode and the second liquid electrode, preferably with the use of one or more connectors, and wherein the power supply is configured to provide an electric charge to and / or withdraw an electric charge from at least the first liquid electrode and / or the second liquid electrode. Preferably, the power supply is operatively coupled with all the electrodes, such that an electric charge may be provided to all the electrodes.

[0026] It is noted that said power supply may also be referred to as current source.

[0027] In a presently preferred embodiment of the invention the first and / or second liquid electrode comprise a redox molecule including one or more elements selected from the group of tungsten, molybdenum, silicon, sodium, potassium, and magnesium. It will be understood that the electrode(s) comprise the molecule at least in the operational state and optionally also in the non-operational state of the cell.

[0028] Experiments have shown that the use of one or more of the listed elements in relation to a redox molecule and the liquid electrodes of the electrochemical cell in an embodiment of the present invention results in an effective ion (cation and / or anion) separation and / or recovery. Preferably, the redox molecule further comprises oxygen (oxygen molecule or one or more oxygen atoms) as a component. This enables an effective charging and discharging operation for the first and second liquid electrodes.

[0029] In a presently preferred embodiment of the invention the redox molecule is one or more of sodium polytungstate (also referred to as sodium metatungstate), sodium polymolybdate, sodium phosphomolybdate, sodium phosphotungstate, sodium polysilicate, phosphomolybdic acid, and phosphotungstic acid.

[0030] It is noted that the aforementioned redox molecules may include the hydrate form thereof and / or (aqueous) solutions thereof.

[0031] The listed redox molecules have shown to provide effective redox molecules that can be applied successfully in one or more of the potential applications, for example in the applications that were already mentioned earlier.

[0032] In one of the presently preferred embodiments of the invention, the redox molecule is sodium polytungstate (SPT).

[0033] The use of SPT as the redox molecule enables an effective charging and discharging operation with the electrochemical cell in an embodiment of the present invention. As an example, the basic reactions in a charging mode, when using SPT, at the negatively charged / biased electrodes are described during charging as follows:Sodium metatungstate is the inorganic compound with the formula NaeEFfcWnOro], sometimes written 3 Na^WOr • 9 WO3 • H2O. It is also referred to as sodium polytungstate (SPT).

[0034] During charging, as an example, the following reaction takes place at the negatively biased electrode:

[0035] 6Na++ [W12O39 + xe ' 6 Na++ [W Osg]6^ + xNa+(orxLi+)

[0036] The electronic charge (xe ) due to negative bias reduces the sodium polytungstate (SPT) resulting in reduced form

[0037]

[0038] . To compensate the extra negative charge in the SPT molecule, more x Na+(or x Li+), is migrated from the feed water through the porous membrane (i.e., removal of Na from feed water). This way, the system is charge neutral.

[0039] During charging, also as an example, the following reaction takes place that the positively charged / biased electrode:

[0040] 6 Na++ [WnO39]6+x+ xNa+(orxLi+) — > 6Na++ [W12O39]6' + xNa+(orxLi+) + x e + xCl

[0041] At the positively charged electrode there is started with the already reduced SPT. The reduced SPT (or charged SPT), that in this example has already adsorbed Na / Li, is oxidized due to electrical bias resulting in desorbing some of the Na+ / Li+and going back to its initial low-negative charge [W12O39]6. The desorbed Na+ / Li+cannot escape the electrode compartment due to the presence of the anion-exchange membrane. Therefore, anions (such as Cl ) are transported from the feed water to the electrode compartment to maintain charge neutrality. These simultaneous occurring phenomena result in this example in removal of Na+(or other cations) and Cl (or other anions) from the feed flow during the charging mode.

[0042] It will be understood that the application of other redox molecules can also be envisaged in accordance with the present invention. Preferably, also these alternative redox molecules do not contain carbon and have a weight of above 400 g / mol.

[0043] In the aforementioned third selectivity step, the size and charge of the respective ion determines the adsorption possibilities with the respective redox molecule, for example the SPT redox molecule. In addition to the effects of the other selectivity steps, this achieves an effective multi-step selectivity, thereby improving the overall selectivity of the charging process.

[0044] In one of the presently preferred embodiments of the invention the electrochemical cell consists of at least one porous membrane and at least one anion exchange membrane. For example, consists of one porous membrane and one anion exchange membrane. Other types of membranes are not necessarily required in such embodiment for an effective charging and discharging of the electrochemical cell. This enables an efficient and effective electrochemical cell.In a further preferred embodiment of the invention the first membrane has a molecular weight cut off in the range of 30 Da to 5000 Da, preferably the first membrane has a molecular weight cut off in the range of 150 Da to 5000 Da, more preferably the first membrane has a molecular weight cut off in the range of 150 Da to 2000 Da.

[0045] The first membrane, preferably the porous membrane, is provided with a molecular weight cut off in the aforementioned range that is preferably smaller than the molecular weight of the redox molecules that are used in the liquid flow electrodes. Therefore, the membrane effectively blocks passage of the redox molecules from the electrode channel to the feed flow channel, while enabling passing of smaller molecules and ions.

[0046] It was found that a membrane with a molecular weight cut of in the range of 30 Da to 2000 Da, preferably 150 Da to 2000 Da, enables an efficient and effective method according to the invention.

[0047] The invention further relates to an electrochemical system comprising a first electrochemical cell in an embodiment according to the present invention.

[0048] Such electrochemical system provides the same or similar advantages and effects as described in relation to the electrochemical cell.

[0049] In some of the presently preferred embodiments, the electrochemical system further comprises two or more cell stacks having one or more electrochemical cells. Such multi-stack electrochemical system provides additional flexibility to the system, for example enabling improved selectivity in the discharge flow(s) when discharging the electrodes.

[0050] The multi-step selectivity may involve the use of a system comprising a multi-stack electrochemical cell. Said stack preferably comprises at least two electrochemical stacks which are operated in a charging mode and at least two electrochemical stacks are operated in a discharging mode. Each stack comprises (separately) liquid electrodes configured for selective ion adsorption and desorption.

[0051] For example, in a first charging stack, a charging voltage and / or charging current (said charging voltage and / or charging current may also be referred to as electrical charge) is applied to selectively adsorb lithium ions (Li+) and chloride ions (Cl") from a lithium chloride (LiCl) feed solution. In a second charging stack, a charging voltage and / or charging current is applied to selectively adsorb sodium ions (Na+) and carbonate ions (CO32) from a sodium carbonate (Na2COs) feed solution.

[0052] After completion of the charging steps, the liquid electrodes containing adsorbed ions are transferred, fluidically connected, or otherwise integrated into separate discharging stacks. In a third electrochemical stack, the liquid electrode containing chloride ions from the first charging stack and the liquid electrode containing sodium ions from the second charging stack are discharged into a flow of pure water, resulting in the formation of a high-purity sodium chloride(NaCl) solution at the effluent. This transfer / connection / integration can be performed by providing the system with transferring means, for example as described in relation to the cell. In addition, said transferring means may be one or more pumps, connecting lines, inlets, outlets, and the like.

[0053] In a fourth electrochemical stack, the liquid electrode containing lithium ions from the first charging stack and the liquid electrode containing carbonate ions from the second charging stack are discharged into a flow of purified water, resulting in the formation of a high-purity lithium carbonate (ITzCCh) solution at the effluent.

[0054] Effluent streams from each discharging stack may be collected for analysis or further processing. This multi-stack configuration enables effective conversion of lithium chloride into lithium carbonate without introducing sodium carbonate into the same electrochemical stack or vessel, thereby reducing or eliminating contamination by sodium ions in the lithium carbonate product. Preferably, each electrochemical cell of the stack comprises an inlet and outlet, wherein the inlet and outlet of two adjacent electrochemical cells are operatively connected with each other. Said inlet and outlet are configured to transfer a feed flow through the stack.

[0055] In a presently preferred embodiment of the invention, the electrochemical system further comprises a second electrochemical cell that is positioned in series with the first electrochemical cell. Providing multiple electrochemical cells in series, such as two, three, four, five, etc., electrochemical cells in an electrochemical cell stack of such system, the overall performance of the ion separation and / or recovery can be improved further.

[0056] In addition, or alternatively, the second electrochemical ell may be positioned in parallel with the first electrochemical cell. Providing multiple electrochemical cells in parallel, such as two, three, four, five, etc., enables to improve the overall performance of the ion separation and / or recovery, including, but not limited to, an increase of the throughput capacity.

[0057] The two or more cells can be provided in a single stack having a single flow in the charging step (also referred to as charging state) and a single flow in the discharging step (also referred to as discharging state). In a somewhat more complex system, the single stack can be provided with a multi-flow system in the discharging step. Alternatively, the total number of cells is distributed over more than one cell stack, for example two, three, four or any other suitable number of cell stacks. As already indicated, such multi-stack electrochemical system provides additional flexibility. For example, separate cell stacks can be provided with a separate discharge flow in the discharging step such that the discharge flows have a different (selective) ion / mineral component.

[0058] In one of the presently preferred embodiments the first and second membranes are identical for all the individual cells in the stack. This renders the stack suitable for selective separation of a single specific ion (cation) and separation of anions without significant selectivity, for example.

[0059] Alternatively, in another of the presently preferred embodiments of the invention, different cells in a single or multi-stack electrochemical system may have different porous membranes totarget multiple cations using a single stack of cells, for example. In addition, or as an alternative, the different cells may have different (anion) exchange membranes having a different selectivity, for example. The application of one or more different membranes between separate cells enables selective transport of a first target ion in a first cell and selective separation of a second target ion that is different from the first ion in a second or further cell. This enables a selective ion separation for different ions. For example, in a first cell, natrium can be removed from the feed flow, while in the second cell another cation ion is selectively separated from the feed flow. It will be understood that also other ions can be removed selectively. Furthermore, this selective separation of separate ions is not limited to one, two, three or more ions, and enables an endless specific separation of target ions. One of the advantageous effects of such stack having different membranes is that such electrochemical system enables simultaneous removal of different target ions within the same system.

[0060] Preferably, in some of the presently preferred embodiments of the invention, when discharging the electrochemical system in the operational state, the different ions are discharged in separate flows, thereby improving the purity of the recovered ions. These selective ions enable forming of (specific) minerals, for example. Such different flows can be applied in an electrochemical system having multiple stacks with different flows during discharge such that the discharge flows have a different (selective) ion / mineral component. A single stack with multiple cells having different membranes may have one discharge flow having all the different components that are removed in the previous charging step. Alternatively, in a somewhat more complex setup, also a single stack is provided with multiple (discharge) flows having their selective discharge component (ion). Preferably, the second and / or further electrochemical cell in a single or multistack electrochemical system have a discharging inlet and preferably separate discharging outlets. Also preferably, each stack of a multi-stack embodiment of the electrochemical system is provided with a separate discharging inlet and a separate discharging outlet. This enables the aforementioned separate recovery of different ions from the liquid solution, whereby the ions are also purified.

[0061] In a further preferred embodiment of the invention the electrochemical system further comprises a controller configured for operating the one or more electrochemical cells and / or stacks, and switching between a charging state and the discharging state. Such controller may optionally include a valve controller that is mentioned in relation to the cell.

[0062] Providing a controller enables an effective switching between the different modes of the system. More specifically, the controller is configured to operate a stack in a charging mode, wherein an electric potential current is applied across the electrode channel of the cell or stack of cells to selectively remove ions from the feed flow within the feed flow channel. In addition, the controller is configured for operating the system in a discharging mode, wherein the voltage or current is reversed to facilitate the recovery of the removed ions. Alternatively, the controller isconfigured to operate the stack in a discharging mode, wherein the electrodes have switched position in an open circuit for recovery of removed ions. Preferably, in any of the discharging modes, the liquid flow is split into multiple streams that are routed to the individual stacks (or cells) to produce separate output flows that are enriched with the specific ions. This improves the overall efficiency of the discharging process and enables a further purification of the respective ions.

[0063] In a further preferred embodiment of the invention the electrochemical system comprises one or more sensors configured for measuring real-time feed flow composition and wherein the sensors are operatively coupled to the controller to enable optimisation of the ion separation and / or purification efficiency.

[0064] Applying a sensor in the system gives access to real-time information that can be used by the controller to optimise the charging and / or discharging operation. For example, the applied voltage or current can be adjusted or switched based on the specific ions, size thereof, charge thereof and order physio-chemical properties such as hydration energy. This improves the operational efficiency of the separation and / or or recovery processes. In addition, this enables the controller to maximise simultaneous adsorption of specific ions in the respective different cells of a multiple cell stack of the electrochemical system in one of the presently preferred embodiments of the invention. Also, in the discharging mode of such system the separate flows can be controlled effectively. In addition, charging and discharging processes can be monitored and controlled effectively, including an optional integrated feedback control system to achieve a further optimisation of the separation and recovery processes. Such sensors may comprise any suitable type of sensor, such as flow sensors, pH sensor, temperature sensor, pressure sensor, etc.

[0065] In a further presently preferred embodiment according to the invention, the electrodes forming the cathode of at least two electrochemical cells or two electrodes forming the anode of at least two electrochemical cells are swopped with each other.

[0066] It is noted that each electrochemical cell comprises an anode and a cathode. Said anode and cathode are formed by the first liquid electrode or second liquid electrode.

[0067] In the aforementioned preferred embodiment, the anode of at least two electrochemical cells or the cathode or at least two electrochemical cells are swopped with each other after the charging state / charging the electrochemical system. Another swop may be performed after discharging. In other words, the cathode or anode of the first electrochemical cell is swopped with the cathode or anode respectively of the second electrochemical cell.

[0068] The invention further also relates to a method for electrochemical ion separations of ions for recovery and / or purification, wherein the method comprises the steps of:

[0069] - providing an electrochemical system according to one of the embodiments of the invention;- providing an electric charge over the electrodes;

[0070] - supplying a feed flow through the feed flow channel;

[0071] - applying an electric charge over the first and second electrodes; and

[0072] - charging the electrode flows and separating ions (cation and / or anions) from the feed flow.

[0073] Such method provides the same or similar effects and advantages as described in relation to the electrochemical cell and / or electrochemical system.

[0074] The method preferably also comprises the step of discharging the electrodes. Such discharging may involve providing a reverse electrical charge to the electrodes and / or switching the electrodes in an open circuit. This enables adsorbing of ions that are absorbed in a charging step discharged to produce new salt types by combining various combination of adsorbed cations and anions. After switching the system to an open-circuit mode in a discharging mode, liquid electrodes are switched or will be positioned between the different cells and different incoming flows are supplied to each cell and / or stack of cells to enable collection of specific salt types and / or minerals in output flows that can be separated from each individual cell and / or stack of cells. This generates a new possibility to produce specific salt types. In such example specific ions (cations and / or anions) are adsorbed in different cells based on the selective electrode and membrane configuration. In several of the presently preferred embodiments the method comprises one or more of the steps that are described in relation to the cell and / or system.

[0075] In one of the presently preferred embodiments, the method further comprises the step of providing two or more electrochemical cells, switching electrodes between electrochemical cells before discharging, and producing specific salt types when discharging the electrodes. This enables producing pre-designed salt types when discharging the electrodes.

[0076] In a further presently preferred embodiment, the method according to the invention further comprises one or more of the steps:

[0077] - controlling the feed flow; and / or

[0078] - changing the direction of the feed flow.

[0079] Said controlling step may be performed during any one of the steps of the method according to the invention. Furthermore, the step of changing the direction of the feed flow may be performed after the step of charging the electrode flow.

[0080] An advantage of the controlling step and / or changing step is that optimal ion separation of ions recovery and / or purification is achieved.

[0081] In a further presently preferred embodiment, the method according to the invention may be used in a battery manufacturing process and / or metal mining process. In other words, the method according to the invention is suitable for electrochemical ion separation and / or purification during battery manufacturing processes and / or metal mining processes, wherein said method comprisesthe steps of the method for electrochemical ion separation of ions for recovery and / or purification according to the invention.

[0082] An advantage of the method according to the invention used in a battery manufacturing process and / or metal mining process is that the environmental impact of waste streams is significantly reduced. Furthermore, said method enables to efficiently remove and / or recover and / or harvest (valuable) mineral / metals from a feed flow.

[0083] Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

[0084] - figure 1A shows an example of a cell and system in an embodiment of the invention; - figure 1B provides a schematic overview of the cell / system of figure 1A when in operation;

[0085] - figure 2 illustrates an overview of a system with multiple cells according to the invention; - figure 3A-C illustrate a schematic overview of different modes of a system with multiple cells in an embodiment of the present invention;

[0086] - figure 4A-C illustrate a schematic overview of different modes of an alternative system according to the invention;

[0087] - figures 5-10 show some experimental results with the cell and system in an embodiment of the present invention;

[0088] - figures 11 A-B show some experimental results with the cell and system in an embodiment of the present invention;

[0089] - figures 12A-D show some experimental results with the cell and system in an embodiment of the present invention;

[0090] - figure 13 shows an example of a cell and system in an embodiment of the invention; and - figure 14 shows an example of a cell and system in an embodiment of the invention. Electrochemical cell 2 (figure 1A) comprises compartment 4. Electrochemical cell 2 is provided with first liquid electrode 6 and second electrode 8. First liquid electrode 6 comprises electrode reservoir 10 that is operatively connected to pump 12 and inlet 14. From inlet 14 the electrode liquid enters electrode channel 16. In the illustrated embodiment, electrode channel 16 is provided with porous material 18 and output 20 that is operatively connected to reservoir 10.

[0091] Liquid electrode 6 further comprises current collector 22 that is electrically connected to voltage or current source 24. Liquid electrode 6 further comprises porous membrane 26. Compartment 4 further comprises feed flow channel 28 having inlet 30 and outlet 32. Second electrode 8 comprises reservoir 34, pump 36, inlet 38, electrode channel 40 with porous material 42, and output 44.In a preferred embodiment, electrochemical cell 2 comprises electrode chamber 17 and / or electrode chamber 41. Said electrode chambers are configured for receiving the first, second, or further liquid.

[0092] Second liquid electrode 8 further comprises current collector 46 that is operatively connected to source 24. Schematically illustrated is spacer 48 that defines feed flow channel 28 between first electrode 6 and second electrode 8. In this illustrated embodiment electrochemical system 102 comprises all components described in relation to electrochemical cell 2 with source 24.

[0093] In a preferred embodiment, electrochemical cell 2 further comprises transferring means 31. Said transferring means comprise outlet, inlets, valves, and (additional) pumps. Said transferring means are configured to operatively couple adjacent electrochemical cells and / or enable to provide feed flow to the electrochemical cell according to the invention.

[0094] In a charging mode of electrochemical cell 2 of electrochemical system 102 (figure 1B), first liquid electrode 6 is negatively charged / biased and second liquid electrode 8 is positively charged / biased. In this embodiment redox molecule SPT 52 is provided in both liquid electrodes 6, 8. From feed flow channel 28, cations 56, 58 and 60 are attracted towards first liquid electrode 6. In this illustrated embodiment porous membrane 26 blocks cation 56 such that only the smaller cations 58, 60 may pass membrane 26. This provides a first selectivity for cell 2. SPT molecule 52, 54 is schematically illustrated comprising a number of positions for adsorbing cations 58, 60. In charging mode, SPT molecule 52 adsorbs selectively cations 58, 60 as a further selectivity step, and at liquid electrode 8 desorbs or releases these cations. Anions 62 are attracted towards the free cations in electrode channel 40. Anion exchange membrane 50 selectively enables anions 62 to leave feed flow channel 28 and enter second electrode channel 40 as a further selectivity step. Also, anion exchange membrane 50 of second electrode 8 blocks cations from leaving second electrode channel 40.

[0095] In another embodiment, electrochemical system 202 (figure 2) comprises first electrochemical cell 204 and second electrochemical cell 206. Each cell 204, 206 comprises a compartment 4a, b that have first liquid electrode 6a, b and second liquid electrodes 8a, b, respectively. In this illustrated embodiment electrochemical system 202 has one feed flow channel 208 to enable liquid flow through each individual cells 204, 206.

[0096] In an illustrated embodiment, system 202 (figure 3A) is provided with a number of electrochemical cells 204, 206 that are placed in series. It is noted that each of the electrochemical cells 204, 206 may represent a stack of cells. It will be understood that a number of cells / stacks 204, 206 can be increased and can be designed as function of the overall system objectives. In charging mode (figure 3B) of system 202, feed flow 208 passes through the respective feed flow channels of cells 204, 206. In this illustrated embodiment, first membrane 26a of first cell 204 is different from the first membrane 26b of the second cell 206. Also in this illustrated embodiment,cations having a single charge are selectively attracted by first electrode 6a of cell 204 and cations having a double charge are attracted to first electrode 6b of second cell 206. Optionally, also anion-exchange membrane 50a of first cell 204 is different from anion membrane 50b of second cell 206. This also enables selective attraction of anion type in different cells 204, 206.

[0097] In the illustrated embodiment of system 202 (figure 3C), the electrical charge is reversed when switching from charging mode to discharge mode. Flow 210 passes through first cell 204 and comprises the first target ions, for example natrium and chloride. A second flow 212 is sent to second cell 206 and comprises selective ions, for example calcium for example forming calcium oxide. It will be understood that other molecules can also be formed in this way. This results in two different outflows to 214, 216 having high purity of a specific component. In this illustrated embodiment the electrical charge is reversed when switching from charging mode to discharge mode.

[0098] In an alternative embodiment, when changing from charging mode to discharge mode electrodes will be switched in their position. Such electrochemical system with switching electrodes 302 (figure 4A-C) is schematically illustrated and is illustrated with two separate cells 304, 306 that are the same or are similar to cells 204, 206 of system 202 (figures 2 and 3). It is noted that each of the electrochemical cells 204, 206 may represent a stack of cells. Such system 302 (figure 4A) is in a charging mode provided with a single feed flow 308, or alternatively with multiple feed flows 308a, b. In this embodiment first electrodes 6a, 6b are different and also second liquid electrodes 8a, 8b are different and show different selectivity similar to the electrochemical cell 202 (figure 3). When going from charging mode (figure 4 A) via a switching operation (figure 4B) to discharging mode (figure 4C) electrodes 6a, b are switched in position. Alternatively, electrodes 8a, b are switched (not shown). In this illustrated embodiment second liquid electrodes 8a, b are maintained in position. After switching is completed, discharging mode can be started with separate flows 310, 312. Providing the respective flows 310, 312 to the respective electrochemical cells 304, 306 provides separate outflows 314, 316. This embodiment thereby enables providing specific ions (and minerals) in outflows 314, 316 depending on the switching of the electrodes (figure 4C). This enables designing the components in the output flows 314, 316.

[0099] In an example, when using system 302 (figure 4A-C), separate feed flows 308a, b are provided. In this example, feed flow 308a relates to high purity sodium carbonate (Na2CO3) solution and feed flow 308b relates to a lithium chloride (LiCl) solution with impurities. In the charging mode, first cell 304 removes Na+and CO32-. Second cell 306 removes Li+selectively, and in this illustrated embodiment removes anions without selectivity. For example, said removal may be applied in battery manufacturing processes and / or metal mining processes.

[0100] When charging, at the negatively biased electrode, the following reactions take place:

[0101] Second ( top) cell 306: 6 Na++ [W12O39]6-+ x e-→ 6 Na++ [W12O39]6+x-+ x Li+First (bottom) cell 304: 6 Na++ [W12O39]6-+ x e-→ 6 Na++ [W12O39]6+x-+ x Na+When charging, at the positively biased electrode, the following reactions take place:

[0102] Second ( top) cell 306: 6 Na++ [W12O39]6+x-+ x Li+→ 6 Na++ [W12O39]6-+ x Li++ x Cl-(or x SO42-) + x e-

[0103] First (bottom) cell 304: 6Na++ [W / 2O3‘>]6+' + xNa+6Na++ [W^O^]6+ xNa++ x CO 3 + x e

[0104] In the switching operation, the anion adsorbed liquid electrodes 8a, b are exchanged between cells 304, 306. This relates to the alternative embodiment (not shown) when changing from charging mode to discharge mode wherein electrodes will be switched in their position. In this example, in the discharging mode, wherein both cells 304,306 of system 302 are provided with a water flow. Second cell 306 concentrates Li2CO3. First cell 304 concentrates a mixture of Na+with the available anions, thereby resulting in NaCl, Na2SO4, or Na2CO3, or mixtures thereof.

[0105] When discharging, at the positively biased electrode (because the polarity reversed), the following reactions take place:

[0106] Second ( top) cell 306: 6 Na++ [W12O39]6+x-+ x Li+→ 6 Na++ [W12O39]6-+ x e-

[0107] (wherein lithium ions are desorbed back to feed flow)

[0108] F

[0109]

[0110] First (bottom) cell 304: 6 Na++ [W12O39]6+x-+ x Na+→ 6 Na++ [W12O39]6-+ x e-

[0111] (wherein adsorbed Natrium ions are desorbed back to feed flow)

[0112] When discharging, at the negatively biased electrode (because the polarity reversed), the following reactions take place:

[0113] Second ( top) cell 306: 6 Na++ [W12O39]6-+ x Li++ x CO32-+ x e-→ 6 Na++ [W12O39]6+x-+ x Li+(wherein CO32ions desorbed back to feed flow to create LhCOs stream) First (bottom) cell 304: 6 Na++ [W12O39]6-+ x Na++ x Cl-(or SO42-) + x e-→ 6 Na++ [W12O39]6+x-+ x Na+

[0114]

[0115] (wherein Cl- / SO42-ions desorbed back to feed flow to create mix of NaCl / Na2SO4) Further experiments have been performed with different electrochemical systems 102 in different operational settings.

[0116] In an illustrated embodiment, system 402 is provided (figure 13) showing electrochemical cell 404 in the charging state, and electrochemical cell 406 in the discharging state. It is noted that the charging state and the discharging state may also refer to the charging sequence and discharging sequence respectively. Furthermore, electrochemical cell 404 and electrochemical cell 406 are substantially the same. The charging state and discharging state does not change the appearance of system 402. It is noted that in the charging state and the discharging state different chemical processes are performed and the current may flow differently.

[0117] Furthermore, in the charging state, represented by electrochemical cell 404, the system comprises porous membrane 408 and anion exchange membrane 410. Said porous membrane 408and anion exchange membrane 410 at least partly delineate feed flow channel 412. Furthermore, first liquid electrode 414 is operatively connected with porous membrane 408 and second liquid electrode 416 is operatively connected with porous membrane 410. First liquid electrode 414 and second liquid electrode 416 are operatively connected with power supply 418. Feed flow channel 412 is configured to provide a feed flow to system 402. For example, said feed flow comprises Li2CO3(aq) and sodium (aq) impurities in the charging state.

[0118] In the charging state carbonate ions are at least partly separated and sodium ions are effectively separated from the feed flow. System 402 in the charging state enables to provide a flow, preferably an aqueous flow, comprising a purified Li2CO3.

[0119] In addition, in the discharging state, represented by electrochemical cell 406, the system comprises porous membrane 408 and anion exchange membrane 410. Said porous membrane 408 and anion exchange membrane 410 at least partly delineate feed flow channel 412. Furthermore, first liquid electrode 414 is operatively connected with porous membrane 408 and second liquid electrode 416 is operatively connected with porous membrane 410. First liquid electrode 414 and second liquid electrode 416 are operatively connected with power supply 418. Feed flow channel 412 is configured to provide a feed flow to system 402. For example, said feed flow comprises water in the charging state.

[0120] In the discharging state carbonate ions effectively released from second electrode 416. System 402 in the discharging state enables to provide a flow, preferably an aqueous flow, comprising a purified Na2CO3.

[0121] In an illustrated embodiment, system 502 is provided (figure 14) showing electrochemical stack 504 in the charging state, and electrochemical stack 506 in the discharging state.

[0122] Furthermore, system 502 comprises electrode exchange sequence 505. Electrochemical stack 504 comprises electrochemical cell 504A and electrochemical cell 504B. Furthermore, electrochemical stack 506 comprises electrochemical cell 506A and electrochemical cell 506B.

[0123] Electrochemical cell 504A comprises anion exchange membrane 508 and porous membrane 510. Furthermore, said cell 504A comprises first liquid electrode 512 which is operatively connected with anion exchange membrane 508, and second liquid electrode 514 which is operatively connected with porous membrane 510. In addition, anion exchange membrane 508 and porous membrane 510 at least partly delineate flow feed 516.

[0124] Electrochemical cell 504B comprises anion exchange membrane 518 and porous membrane 520. Furthermore, said cell 504B comprises first liquid electrode 522 which is operatively connected with anion exchange membrane 518, and second liquid electrode 524 which is operatively connected with porous membrane 520. In addition, anion exchange membrane 518 and porous membrane 520 at least partly delineate flow feed 526.Electrochemical cell 506A comprises anion exchange membrane 528 and cation exchange membrane 530. Furthermore, said cell 506A comprises first liquid electrode 532 which is operatively connected with anion exchange membrane 528, and second liquid electrode 534 which is operatively connected with cation exchange membrane 530. In addition, anion exchange membrane 528 and cation exchange membrane 530 at least partly delineate flow feed 536.

[0125] Electrochemical cell 506B comprises anion exchange membrane 538 and cation exchange membrane 540. Furthermore, said cell 506B comprises first liquid electrode 542 which is operatively connected with anion exchange membrane 538, and second liquid electrode 544 which is operatively connected with cation exchange membrane 540. In addition, anion exchange membrane 538 and cation exchange membrane 540 at least partly delineate flow feed 546.

[0126] Furthermore, electrochemical system 502 further comprises power supply 548, wherein power supply 548 is operatively connected with one or more of the electrodes 512, 514, 524, 522, 532, 534, 542, 544. Said power supply 548 is configured to provide an electrical charge or withdraw and electrical charge from one or more of said electrodes.

[0127] In the charging state lithium chloride (aq) is separated into lithium ions and chloride ions by electrochemical cell 504A. The flow leaving electrochemical cell 504A is substantially free of lithium chloride (aq). Furthermore, a feed flow comprising Na2CO3(aq) is separated into carbonate ions and sodium ions by electrochemical cell 504B. The flow leaving electrochemical cell 504B is substantially free of Na2CO3.

[0128] After charging sequence 502 electrode exchange sequence 505 enables to change electrochemical stack 504 to electrochemical stack 506. In said electro exchange sequence 505 the electrodes comprising the cations are exchanged. It is noted that an embodiment in which the anions exchange may also be feasible.

[0129] In the discharging state a feed flow, preferably comprising substantially water (for example tap water), is provided to electrochemical cells 506A and 506B. Electrochemical cell 506B enables to release sodium ions and chloride ions such that sodium chloride (aq) is formed. Furthermore, electrochemical cell 506A enables to release lithium ions and carbonate ions such that Li2CO3(aq) is formed.

[0130] Thus, system 502 enables to efficiently and effectively remove lithium chloride (aq) and sodium carbonate (aq) from a feed flow, such that a purified (aqueous streams) comprising sodium chloride (aq) or lithium carbonate (aq) are formed. The charging and discharge cycles of basic cell 2 with different cell Voltage to desalinate a 5 mM NaCl solution are shown (figures 5-7). Results also show the conductivity response at the effluent of cell 2. During charging, the conductivity reduces. This illustrates that the salt is removed from the effluent water. During discharging, conductivity increases showing that salt content increases in the effluent. The experiments areperformed using membranes with different pore sizes while keeping the same anion-exchange membrane.

[0131] More specifically, figure 5 shows results of salt removal experiments that were carried out with 5 mM NaCl and 500 Da porous membrane 18. Currents when charging (positive current) and discharging (negative current) of single cell 2 of system 102 with 1.2 V (solid line), 1 V (dashed line), and 0.8 V (dotted lines) are shown (figure 5A). Conductivity of the effluent water in response to the three different Voltages during charging and discharging is also shown (figure 5B).

[0132] Figure 6 shows results of salt removal experiments that were carried out with 5 mM NaCl and 1000 Da porous membrane 18. Currents when charging (positive current) and discharging (negative current) of the single cell 2 of system 102 with 1.2 V (solid line), 1 V (dashed line), 0.8 V (dotted lines) are shown (figure 6A). Conductivity of the effluent water in response to three different Voltages during charging and discharging are shown (figure 6B).

[0133] Figure 7 shows results of salt removal experiments that were carried out with 5 mM NaCl and 2000 Da porous membrane. Currents when charging (positive current) and discharging (negative current) of the single cell 2 of system 102 with 1.2 V is shown (figure 7A). Conductivity of the effluent water in response to charging and discharging is also shown (figure 7B).

[0134] Figures 8, 9 and 10 show experimental results when a salt mixture containing at-least 2 different cations is treated using cell 2 of system 102 with 2000 Da porous membrane 18. In this setup, one specific cation is removed more selectively than the other one. In the case of a magnesium and sodium combination, magnesium is removed more selectively (4.2 times more) than sodium. In other experiments using a combination of calcium and sodium, calcium is removed 1.6 times more selectively than sodium. In even further experiments using a sodium and lithium salt mixture, sodium is removed 4.4 times more than lithium. These experiments prove that the present invention can selectively separate salts from a mixture of salts in water.

[0135] More specifically, figure 8 shows some results when using a salt mixture that contains 15 mM NaCl and 15 mM of MgCh that is treated using cell 2 of system 102. Figure 8A shows current when charging and discharging cell 2. Figure 8B shows the ratio of concentration change over initial concentration of Mg and Na ions in samples collected during the charging step.

[0136] Figure 9 shows some results when using a salt mixture that contains 15 mM NaCl and 15 mM of CaCh that is treated using cell 2 of system 102. Figure 9 A shows current when charging and discharging cell 2. Figure 9B shows the ratio of concentration change over initial concentration of Ca and Na ions in samples collected during the charging step.

[0137] Figure 10 shows some results when using a salt mixture that contains 384.7 mM LiCl and 6.9 mM of NaCl that is treated using cell 2 of system 102. Figure 10A shows current when charging and discharging cell 2. Figure 10B shows the ratio of concentration change over initial concentration of Ca and Na ions in samples collected during the charging step.In a further experiment, the concentration of ions in collected effluent samples is determined using inductively coupled plasma mass spectrometry (ICP-MS 2030, Shimadzu).

[0138] Prior to analysis, samples are diluted with ultra-pure water to bring ion concentrations within the calibrated measurement range of the ICP-MS instrument for each ion of interest. The diluted samples are subsequently acidified with approximately 2% (v / v) ultra-pure nitric acid to stabilize the ionic species and enable accurate measurement.

[0139] Measured ion concentrations are obtained directly for positive ions. In cases where the feed solution contains a single anionic species, the concentration of the anion is calculated based on charge balance using the measured concentrations of all corresponding positive ions.

[0140] Figure 11 A and B define time (in seconds) on the x-axis, voltage (in V) on the left y-axis and current (in A) on the right y-axis. The dotted line represents the voltage, and the solid line represents the current.

[0141] Said figures 11 A and B illustrates a single-stack operation in which adsorption and desorption steps are performed within the same cell successively. Figure 11A includes the voltage and current responses during selective adsorption of impurities from a lithium carbonate brine. Figure 1 IB includes the voltage and current responses during desorption of the selectively adsorbed impurities in the successive step.

[0142] It is noted that the feed and effluent concentrations during selective adsorption of impurities from a lithium carbonate brine are provided in Table 1. The feed concentration comprises a lithium carbonate equivalent (LCE) of 13.86431, sodium 0.067, calcium 0.116 and magnesium of 0.017. The purity of LCE (wt.%) was 98.58. The anion concentrations were calculated based on charge balance.

[0143] Table 1 shows results from single-stack operation for Lithium carbonate purification, wherein different membrane types are employed for selective impurity adsorption step (figure 11 A) and impurity desorption step (figure 11B). Purified LCE stream is collected during step A and displayed in the table

[0144] Operational voltage window Purity LCE Membrane Purified LCE (g / 1)

[0145] (V) (wt.%)

[0146] LCE* Na Ca Mg

[0147] MWCO 200 Da 1.1 to 1.3 12.271 0.064 0.000 0.013 99.37 MWCO 400 Da 0.8 to 1.1 9.333 0.047 0.000 0.022 99.26 MWCO 1000 Da 0.8 to 1.1 11.750 0.048 0.000 0.011 99.50 MWCO 2000 Da 1.1 to 1.3 11.275 0.054 0.003 0.000 99.49 MWCO 2000 Da 2.5 10.939 0.026 0.000 0.000 99.76

[0148]

[0149] * anion concentrations were calculated based on charge balanceFigures 12A-D illustrates the multi stack operation for salt conversion where in stack 1 (figure 12A) and 2 (figure 12B) used a porous membrane with MWCO of <100 Da on the cation adsorption side and Anion Exchange Membrane on the anion adsorption side. Stack 3 (figure 12C) and 4 (figure 12D) used cation exchange membrane and anion exchange membranes for cation and anion transport.

[0150] Figure 12A-D define time (in seconds) on the x-axis, voltage (in V) on the left y-axis and current (in A) on the right y-axis. The dotted line represents the voltage, and the solid line represents the current. Figure 11A includes voltage and current responses during adsorption of lithium and chloride ions from a EiCl brine in a first cell stack. Figure 12B includes voltage and current responses during adsorption of sodium and carbonate (CO32-) ions from a Na2CO3solution in a second cell stack. Figure 12C includes voltage and current responses during discharge of ions in deionized water, in a third cell stack, of a chloride-adsorbed liquid electrode obtained from step the step forming figure 12A and with a sodium-adsorbed liquid electrode obtained from step forming figure 12B. Figure 12D includes voltage and current responses during discharge of ions in deionized water, in a fourth cell stack, of a lithium-adsorbed liquid electrode obtained from step forming figure 12A with a carbonate-adsorbed liquid electrode obtained from step forming figure 12B, thereby forming a Li2CO3solution and converting LiCl to Li2CO3without direct addition of Na2CO3in the same solution, while reducing or avoiding introduction of sodium impurities.

[0151] It is noted that the feed and effluent concentrations during selective adsorption of impurities from a lithium carbonate brine are provided in Tables 2 and 3.

[0152] The feed concentration comprises a lithium chloride concentration of 16.717, sodium 0.378, calcium 0.816 and magnesium of 0.02816. The purity of the lithium chloride (wt.%) was 93.19 for the feed water used for the results disclosed in Table 2.

[0153] The feed concentration comprises a lithium chloride of 9.126, sodium 0.158745, calcium 0.087683 and magnesium of 0.076738. The purity of the lithium chloride (wt.%) was 96.58 for the feed water used for the results disclosed in Table 3.

[0154] The anion concentrations were calculated based on charge balance.

[0155] Table 2 shows results from multi-stack operation for salt conversion, wherein different membrane types are employed for lithium extraction in the step forming figure 12A and for formation of Li2CO3and / or LiF in the step forming figure 12D from a LiCl feed solution.

[0156] Purity LCE LiCl to LCE conversion Membrane LCE converted (g / 1)

[0157] (wt.%) (wt.%) LCE* Na Ca Mg

[0158] MWCO <100 Da 0.85767 0.0124 0.004 0.002 97.90 5.1

[0159] MWCO <150 Da 2.010725 0.0228 0.032 0.0012 97.29 12.0

[0160]

[0161] MWCO 200 Da 2.419094 0.0288 0.076 0.00344 95.72 14.5

[0162] Purity LiF LiCl to LiF conversion LiF converted (g / 1)

[0163] (wt.%) (wt.%) LiF* Na Ca Mg

[0164] MWCO <100 Da 0.3 0.0078 0 0 97.47 1.8

[0165]

[0166] * anion concentrations were calculated based on charge balance

[0167] Table 3 shows the same multi-stack operation using a higher-purity LiCl brine feed, resulting in formation of Li2CO3having a purity greater than 99.5 wt%, suitable for use in battery manufacturing processes.

[0168] Purity LCE LiCl to LCE conversion Membrane LCE converted (g / 1)

[0169] (wt.%) (wt.%) LCE* Na Ca Mg

[0170] MWCO <100 1.256742 0.004751 0 0.001361 99.52 13.8

[0171] Da

[0172]

[0173] * anion concentrations were calculated based on charge balance

[0174] It was found that an electrochemical cell according to the invention comprising a membrane with a molecular weight cut of in the range of 30 Da to 2000 Da provides an efficient and effective ion separation / recovery. Using a membrane with a molecular weight cut off above 5000 Da results in undesired ion transport between the various compartments. Therefore, in a preferred embodiment according to the invention, at least the first membrane has a molecular weight cut off in the range of 30 Da to 5000 Da.

[0175] Furthermore, it was found that the electrochemical cell and / or electrochemical system and / or method for electrochemical ion separation according to the invention can efficiently and effectively separate ions for recovery and / or purification. As a result, the (valuable) ions can be harvested from a feed stream.

[0176] The present invention is by no means limited to the above-described preferred embodiments and / or experiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged.

Claims

CLAIMS1. Electrochemical cell for ion separation and / or recovery from a liquid solution, wherein the electrochemical cell comprises:- a compartment;- a first liquid electrode that is positioned in the compartment and comprises a first current collector, a first membrane, and a first electrode channel between the first current collector and the first membrane that is configured to allow a first electrode flow;- a second liquid electrode that is positioned in the compartment and comprises a second current collector, a second membrane, and a second electrode channel between the second current collector and the second membrane that is configured to allow a second electrode flow; and - a feed flow channel extending between the first and second liquid electrodes and having an inlet and an outlet.

2. Electrochemical cell according to claim 1, wherein the second membrane comprises an anion exchange membrane, and / or wherein the first and / or second electrode channel comprises a porous conductive material.

3. Electrochemical cell according to any one of the foregoing claims, further comprising a power supply, wherein the power supply is operatively coupled with at least the first liquid electrode and the second liquid electrode, and wherein the power supply is configured to provide an electric charge to and / or withdraw an electric charge from at least the first liquid electrode and / or the second liquid electrode, preferably the power supply comprises one or more connectors wherein the connectors are configured to operatively connect the power supply with the first liquid electrode and the second liquid electrode.

4. Electrochemical cell according to any of the foregoing claims, wherein the first and / or second liquid electrode comprises a redox molecule including one or more elements selected from the group of tungsten, molybdenum, silicon, sodium, potassium, and magnesium.

5. Electrochemical cell according to the foregoing claim, wherein the redox molecule further comprises oxygen as a component.

6. Electrochemical cell according to the foregoing claim, wherein the redox molecule is one or more of sodium polytungstate, sodium polymolybdate, sodium phosphomolybdate, sodiumphosphotungstate, sodium polysilicate, phosphomolybdic acid, and phosphotungstic acid, and / or wherein the redox molecule is sodium polytungstate (SPT).

7. Electrochemical cell according to any of the foregoing claims, wherein the first liquid electrode and / or the second liquid electrode comprises an electrode chamber configured for receiving the first electrode flow or second second electrode flow.

8. Electrochemical cell according to any of the foregoing claims, wherein the first membrane has a molecular weight cut off in the range of 30 Da to 5000 Da, preferably in the range of 150 Da to 5000 Da, more preferably in the range of 50 Da to 2000 Da.

9. Electrochemical system comprising a first electrochemical cell according to any of the foregoing claims.

10. Electrochemical system according to the foregoing claim, further comprising two or more cell stacks having one or more electrochemical cells.

11. Electrochemical system according to any of the foregoing claims 9-10, further comprising a second electrochemical cell in series with the first electrochemical cell.

12. Electrochemical system according to any of the foregoing claims 9-11, wherein the first and / or second membrane of the second electrochemical cell and / or cell stack is different from the first and / or second membrane of the first electrochemical cell and / or cell stack.

13. Electrochemical system according to the foregoing claim, wherein the second electrochemical cell and / or stack has a discharging inlet and a separate discharging outlet.

14. Electrochemical system according to any of the foregoing claims 9-13, further comprising a controller configured for operating the one or more electrochemical cells and / or stacks, and switching between a charging state and a discharging state.

15. Electrochemical system according to the foregoing claim, further comprising one or more sensors configured for measuring real-time feed flow composition, and that is / are operatively coupled to the controller to enable optimization of the ion separation and / or purification efficiency.

16. Electrochemical system according to any one of the claims 9-15, wherein the electrodes forming the cathode of at least two electrochemical cells or two electrodes forming the anode of at least two electrochemical cells are swopped with each other.

17. Method for electrochemical ion separation of ions for recovery and / or purification, the method comprising the steps of:- providing an electrochemical cell or system according to any of the foregoing claims; - providing an electric charge over the electrodes;- supplying a feed flow through the feed flow channel;- applying an electric charge over the first and second electrodes; and- charging the electrode flows and separating ions from the feed flow.

18. Method according to the foregoing claim, further comprising the step of discharging the electrodes.

19. Method according to the foregoing claim, further comprising the step of providing two or more electrochemical cells, switching electrodes between electrochemical cells before discharging, and producing specific salt types when discharging the electrodes.

20. Method according to any one of the claims 17 to 19, further comprising one or more of the steps:- controlling the feed flow; and / or- changing the direction of the feed flow.

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