Process to avoid electrode fouling / scaling towards a sustainable seawater / brine electrolysis system

Abstract

Herein disclosed is a system for avoiding fouling or scaling of an electrode used in electrolysis, the system comprising: an electrochemical reactor having a cathode chamber and an anode chamber, wherein the cathode chamber is in fluid communication with a precipitation vessel; a fresh brine pump operable to deliver fresh brine to the precipitation vessel, wherein the fresh brine comprises calcium ions and magnesium ions; and a flue gas pump operable to deliver carbon dioxide to the precipitation vessel; wherein the precipitation vessel is configured to remove any precipitate, wherein the precipitate and a treated brine solution are generated from: (i) an alkaline solution channeled from the cathode chamber, (ii) the fresh brine, and (iii) the carbon dioxide, wherein the treated brine solution is absent of the calcium ions and the magnesium ions after removing any precipitate, and the treated brine solution is channeled from the precipitation vessel to the cathode chamber and the anode chamber. A method for avoiding fouling or scaling of an electrode used in electrolysis via the system is also disclosed.

Description

PROCESS TO AVOID ELECTRODE FOULING / SCALING TOWARDS ASUSTAINABLE SEAWATER / BRINE ELECTROLYSIS SYSTEMCross-Reference to Related Application

[0001] This application claims the benefit of priority of Singapore Patent Application No. 10202402333P, filed 5 August 2024, the content of it being hereby incorporated by reference in its entirety for all purposes.Technical Field

[0002] The present disclosure relates to a system, and a method, for avoiding fouling or scaling of an electrode used in electrolysis.Background

[0003] Brine and seawater electrolysis may be some of the processes traditionally involved for producing green Hi, Cl2, and other valuable chemicals from abundant resources, contributing to sustainable energy and water solutions.

[0004] However, the electrolysis of brine and / or seawater tends to be susceptible to encountering significant issue with fouling / scaling on electrodes, particularly at the cathode. This may occur, for example, in an electrochemical approach for mineral recovery from brine water, wherein precipitates tend to be generated inside a cathode chamber of an electrochemical reactor, affecting continuous operation of the electrochemical system. For example, scaling may occur due to deposits of metal (e.g., Mg2+, Ca2+) hydroxides and / or carbonates on an electrode. The scaling may increase cell resistance which causes higher energy consumption for electrolysis. The scaling may lead to reduced active sites on an electrode, as the deposits may cover the active sites, decreasing overall efficiency. The scaling may then require more frequent cleaning and / or even the replacement of electrode, increasing cost.

[0005] There is thus a need to provide for a solution that addresses one or more of the limitations mentioned above.Summary

[0006] In a first aspect, there is provided for a system for avoiding fouling or scaling of an electrode used in electrolysis, the system comprising: an electrochemical reactor having a cathode chamber and an anode chamber, wherein the cathode chamber is in fluid communication with a precipitation vessel; a fresh brine pump operable to deliver fresh brine to the precipitation vessel, wherein the fresh brine comprises calcium ions and magnesium ions; and a flue gas pump operable to deliver carbon dioxide to the precipitation vessel; wherein the precipitation vessel is configured to remove any precipitate, wherein the precipitate and a treated brine solution are generated from:(i) an alkaline solution channeled from the cathode chamber,(ii) the fresh brine, and(iii) the carbon dioxide, wherein the treated brine solution is absent of the calcium ions and the magnesium ions after removing any precipitate, and the treated brine solution is channeled from the precipitation vessel to the cathode chamber and the anode chamber.

[0007] In another aspect, there is provided for a method for avoiding fouling or scaling of an electrode used in electrolysis via the system described in various embodiments of the first aspect, the method comprising: introducing the fresh brine via the fresh brine pump to the precipitation vessel, wherein the fresh brine comprises calcium ions and magnesium ions; channeling the alkaline solution from the cathode chamber of the electrochemical reactor into the precipitation vessel; introducing the carbon dioxide via a flue gas pump to the precipitation vessel; removing any precipitate in the precipitation vessel, wherein the precipitate and a treated brine solution arc generated from:(i) an alkaline solution channeled from the cathode chamber,(ii) the fresh brine, and(iii) the carbon dioxide, wherein the treated brine solution is absent of the calcium ions and the magnesium ions after removing any precipitate, andchanneling the treated brine solution from the precipitation vessel to the cathode chamber and the anode chamber.Brief Description of the Drawings

[0008] The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the present disclosure. In the following description, various embodiments of the present disclosure are described with reference to the following drawings, in which:

[0009] FIG. 1 is a schematic diagram of the system and method of the present disclosure, illustrating a process to avoid precipitation from the electrochemical reactor. 10 denotes a stream carrying fresh brine or seawater or wastewater. 20 denotes a stream carrying treated brine (Mg2+and Ca2+depleted). 30 denotes a stream of OH" enriched brine. 40 denotes a discharge stream (i.e., waste brine). 50 denotes compressed air.

[0010] FIG. 2A is a photograph showing an overview of the experimental setup of the present system.

[0011] FIG. 2B is a photograph showing an experimental configuration of the precipitation vessel of the present system of FIG. 2A.

[0012] FIG. 2C is a photograph showing the filtration paper attached to the tubes of the precipitation vessel for precipitate separation.

[0013] FIG. 2D is a photograph image of the electrochemical reactor of the present system after 4 hours of the process operation.

[0014] FIG. 3 A is a plot of the cell voltage profile during OH ions production.

[0015] FIG. 3B is a plot of the cell voltage curve at an applied current of 200 mA during the process operation.

[0016] FIG. 4 shows x-ray diffraction (XRD) pattern of the precipitate obtained from the precipitation vessel (the precipitate discharged from the precipitation vessel as shown in FIG. 1) under the operation condition stated with respect to FIG. 3B.

[0017] FIG. 5 is a table showing the pH changes in the precipitation vessel during the process operation, with an applied current of 200 mA and flue gas bubbling at 10 seem.

[0018] FIG. 6 shows the cell voltage profile during OH ions production, ran at 110 mA for 3 hours.

[0019] FIG. 7A is a plot for real time Raman monitoring of the Brucite Mg(0H)2 formation.

[0020] FIG. 7B is a plot for real time Raman monitoring of calcite (CaCCh) and CO32" ion formation.

[0021] FIG. 8 shows comparison of the electrochemical reaction and the precipitation reaction involved for a traditional method (left box) against the method and system of the present disclosure (the two boxes on right).

[0022] FIG. 9A is a plot of voltage against time showing V-t profiles of the flow cell for 6 consecutive runs.

[0023] FIG. 9B shows images of the cathode after 112 hours. It was observed that no white precipitates were formed on the cathode surface.

[0024] FIG. 9C shows an image of the solid precipitation obtained after 112 hours.Detailed Description

[0025] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the present disclosure may be practised.

[0026] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0027] The present disclosure relates to a system for reducing fouling / scaling that occurs in the electrolysis of brine and / or seawater (and / or even wastewater, c.g., from construction or mining industries). Particularly, the system is operable to avoid fouling or scaling of an electrode used in, for example, electrolysis of brine, seawater, industrial wastewater, etc. The system is operable to provide an improved process to generate precipitates outside of an electrochemical reactor, avoiding any electrode fouling / scaling issue. The system provides such an advantage without requiring overlycomplex configurations or modifications in an electrochemical reactor and still able to maintain the electrochemical process as a continuous operation.

[0028] Advantageously, the system is operable to provide an improved process for solving any fouling / scaling issues in the recovery of resources from brine, wastewater, and / or seawater. A schematic diagram of the system is shown in FIG. 1. In general, fresh brine 10, which can include mineral ions (e.g., Ca2+and Mg2+), reacts with alkaline brine generated from an electrochemical reactor in a precipitation vessel, wherein CO2 is simultaneously captured. This generates precipitates (which may be denoted by the chemical equation, e.g., Ca2++ Mg2++ CO2 + 4OH" — » CaCCh + Mg(OH)2 + H2O) in the precipitation vessel. The precipitates can be discharged from the precipitation vessel to enable continuous operation. After filtration at the bottom of the precipitation vessel, the treated brine (e.g., with Ca2+and Mg2+removed as stream 20) can be split into two streams. One stream is configured to flow through the cathode chamber of the electrochemical reactor, while another stream is configured to flow through the anode chamber. Under the action of electricity, oxygen in the air (from compress air stream 50) reacts with the water in the treated brine to generate hydroxide (OH ) ions via the oxygen reduction reaction (ORR: O2 + 2H2O + 4e" 4OH ) at the cathode chamber. With the successful capture of Ca2+and Mg2+ions in the precipitation vessel, their content is reduced to a very minor amount, or even none, and no fouling / scaling issues arises in the cathode chamber of the electrochemical reactor during continuous mineral recovery. The system greatly improves the performance and efficiency of the electrochemical reactor compared to traditional systems having such electrochemical reactor.

[0029] The system and method minimize operation downtime that may arise from fouling / scaling issues, as there is no need for frequent cleaning and / or electrode replacement, thereby saving cost.

[0030] The system and method circumvent fouling / scaling issues, allowing maximized utilization of catalytic sites, which in turn lower cell resistance and render higher efficiency.

[0031] The system and method are compatible for use in different industrial and environmental sectors, such as in desalination plants, mining companies, and concrete industries.

[0032] Understandably, the present disclosure relates to a method for reducing fouling / scaling that occurs in the electrolysis of brine and / or seawater, wherein the method is premised on the system. Particularly, the method is suitable for avoiding fouling or scaling of an electrode used in, for example, electrolysis of seawater, brine, any wastewater (e.g., from the mining or construction industries), etc. Accordingly, advantages from the system are analogous to advantages from the method.

[0033] Details of various embodiments of the system and method, and advantages associated with the various embodiments are now described below. Where advantages of the embodiments and features are already demonstrated in one or more examples below, they shall not be reiterated for brevity.

[0034] In the present disclosure, there is provided for a system for reducing fouling or scaling (e.g., of an electrode) in and / or during electrolysis. The system of the present disclosure can be operated without fouling or scaling of an electrode used in (e.g., operating during or in), for example, electrolysis of seawater, brine, any wastewater, etc. In other words, the system of the present disclosure is suitable for avoiding fouling or scaling of an electrode used in electrolysis. In various embodiments, the system may comprise an electrochemical reactor having a cathode chamber and an anode chamber, wherein the cathode chamber is in fluid communication with a precipitation vessel, a fresh brine pump operable to deliver fresh brine to the precipitation vessel, wherein the fresh brine may comprise calcium ions and magnesium ions, and a flue gas pump operable to deliver carbon dioxide to the precipitation vessel, wherein the precipitation vessel may be configured to remove any precipitate (e.g., from a treated brine solution, treated seawater, treated wastewater), wherein the precipitate and a treated brine solution may be generated from: (i) an alkaline solution channeled from the cathode chamber, (ii) the fresh brine, and (iii) the carbon dioxide, wherein the treated brine solution is absent of the calcium ions and the magnesium ions after removing any precipitate, and the treated brine solution may be channeled from the precipitation vessel to the cathode chamber and / or the anode chamber. The terms “fouling” and “scaling” are used exchangeably in the present disclosure, wherein both terms refer to the build-up of deposits on a surface, such as on an electrode.

[0035] Advantageously, the system helps to avoid fouling and / or scaling of one or more electrodes in an electrochemical reactor, especially the electrode in the cathodechamber, which may occur during electrolysis of seawater and / or brine. Brine and seawater may contain minerals, such as calcium and magnesium ions (i.e., Ca2+and Mg2+). The minerals tend to render undesirable deposits build up on an electrode during electrolysis, as such deposits may compromise the performance of electrolysis as mentioned above.

[0036] The present system advantageously removes such ions via the precipitation vessel, which is configured in fluid communication with the cathode chamber of the electrochemical reactor. During operation of the system, oxygen reduction reaction and hydrogen evolution reaction occurs at the cathode chamber to generate, respectively, an alkaline solution comprising OH" ions and hydrogen gas. In the present system, the alkaline solution is channeled directly into the precipitation vessel to come into contact with a fresh brine that is introduced into the precipitation. Carbon dioxide, is also introduced into the precipitation vessel. The alkaline solution, particularly the hydroxide ions, reacts with the minerals, such as Ca2+and Mg2+, in the presence of the carbon dioxide to form precipitates. The chemical equations for this is shown in FIG. 8.

[0037] As seen in FIG. 8, traditional systems and methods are susceptible to such precipitation occuring in the electrochemical reactor, hence fouling of the electrodes. Distinctly, the present system (and present method) arc configured to have the oxygen reduction reaction rendered in the cathode chamber, while the precipitation is rendered in the precipitation vessel. Said differently, the present system (and present method) splits the traditional reaction mechanism into two parts, such that one reaction (i.e., the oxygen reduction reaction) is carried out in the cathode chamber and the precipitation reaction is carried out in a separate precipitation vessel.

[0038] Further advantageously, the present system and method are operable to generate hydrogen at the cathode chamber. In other words, hydrogen evolution reaction is carried out at the same time as the oxygen reduction reaction. The present system and method not only serve to capture carbon dioxide, but generate hydrogen within the process operation.

[0039] Understandably, oxygen evolution reaction and / or chlorine evolution reaction may occur at the anode chamber of the present system and method.

[0040] Tn various embodiments, the cathode chamber may be directly connected to the precipitation vessel. This means there are no intervening units between the cathode chamber and the precipitation vessel, such that the alkaline solution is channeled from the cathode chamber directly into the precipitation vessel and the treated brine solution is channeled from the precipitation vessel directly into the cathode chamber.

[0041] In various embodiments, the flue gas pump is operable to deliver a flue gas or air into the precipitation vessel, wherein the flue gas or the air comprises carbon dioxide.

[0042] In various embodiments, the treated brine solution is formed from the reaction of the alkaline solution and the fresh brine in the presence of the carbon dioxide. In other words, when the alkaline solution and the fresh brine are mixed or come into contact with each other in the precipitation vessel (in the presence of the carbon dioxide), the treated brine solution is formed. The “brine solution” formed at this stage is referred to as “treated brine solution” as it settles in the precipitation vessel and is being filtered to have the precipitates removed therefrom, hence the use of the term “treated”.

[0043] In the present disclosure, the terms “precipitate vessel” and “precipitation vessel” are used exchangeably. The precipitation vessel may be a tank, hence also referred to as a precipitation tank.

[0044] Tn the present disclosure, the electrochemical reactor may be referred to as a flow cell.

[0045] Tn various embodiments, the precipitation vessel may comprise a first inlet for receiving the fresh brine. The fresh brine may comprise calcium and magnesium ions.

[0046] In various embodiments, the precipitation vessel may comprise a second inlet for receiving the alkaline solution from the cathode chamber.

[0047] In various embodiments, the precipitation vessel may comprise a third inlet for receiving the carbon dioxide.

[0048] In various embodiments, the precipitation vessel may comprise a bottom end configured with a first outlet which the treated brine solution flows out from. In various embodiments, the bottom end may be shaped to direct flow of the treated brine solution toward the first outlet. The bottom end may be defined by one or more walls that slopeat an angle toward the first outlet for the treated brine solution to be directed to the first outlet.

[0049] In various embodiments, the precipitation vessel may comprise a filter configured proximal to the bottom end. The filter may extend across the entire crosssection of the precipitation vessel to prevent any precipitate from flowing out of (through) the first outlet.

[0050] In various embodiments, the precipitation vessel may comprise a second outlet configured proximal to the bottom end and configured vertically above or at the same height as the filter. In various embodiments, the second outlet may be configured to discharge any precipitate.

[0051] In various embodiments, the system may further comprise a Raman module comprising a Raman probe operable to detect any precipitate, and if any precipitate is present, aid in generating a Raman spectrum corresponding to a type of precipitate for identifying the type of precipitate, and wherein the Raman probe may have a sensor end configured in the precipitation vessel proximal to the filter. In various embodiments, the Raman module may be a Raman spectrometer. In various embodiments, the Raman probe may comprise a detector as the sensor end, such as a charge-couple device sensor. In various embodiments, the Raman spectrometer may be coupled to a computer operable to collect and analyse spectral data, and to display the Raman spectrum. Said differently, the system may comprise such a computer operably coupled to the Raman spectrometer. In various embodiments, the sensor end may comprise a laser source.

[0052] In various embodiments, the third inlet may extend into the precipitation vessel further than the first inlet and the second inlet so as to direct the carbon dioxide toward the bottom end for contacting with the alkaline solution and the fresh brine. Advantageously, the carbon dioxide can be better mixed and / or contacted with the alkaline solution and the fresh brine.

[0053] In various embodiments, the system may further comprise a pipe connecting the first outlet to the cathode chamber and the anode chamber, wherein the pipe branches into two, with one connected to the cathode chamber and the other connected to the anode chamber, so as to direct the treated brine solution from the precipitation vessel directly into the cathode chamber and / or the anode chamber. Non-limiting examples of the such pipe confiuration may include a pipe having a Y-junction, T-junction, or anysplitter fitting(s) that branches the flow in the pipe into two. In various embodiments, the first outlet is connected directly to the cathode chamber, i.e., the treated brine solution is channeled directly into the electrochemical reactor with no intervening units.

[0054] In various embodiments, the pipe may comprise a T-junction which branches the pipe into two.

[0055] In various embodiments, the electrochemical reactor may comprise an air inlet configured at the cathode chamber for receiving air.

[0056] In various embodiments, the electrochemical reactor may comprise an outlet connected to the second inlet for channeling the alkaline solution from the cathode chamber directly into the precipitation vessel.

[0057] In various embodiments, the electrochemical reactor may comprise a discharge outlet at the anode chamber, wherein the discharge outlet may be configured to discharge any brine (e.g., waste brine generated at the anode chamber) or any waste.

[0058] In various embodiments, the electrochemical reactor may comprise an ion- conductive membrane defining (e.g., separating) the cathode chamber and the anode chamber.

[0059] The present disclosure provides for a method for reducing fouling or scaling (e.g., of an electrode) in and / or during electrolysis via the system described in various embodiments of the first aspect. The method of the present disclosure can be carried out without fouling or scaling of an electrode used in (e.g, operating during or in), for example, electrolysis of seawater, brine, any wastewater, etc. In other words, the method of the present disclosure is suitable for avoiding fouling or scaling of an electrode used in electrolysis. Embodiments and advantages described for the system can be analogously valid for the method subsequently described herein, and vice versa. As the various embodiments and advantages have already been described above and in examples demonstrated herein, they shall not be iterated for brevity.

[0060] In various embodiments, the method may comprise introducing the fresh brine via the fresh brine pump to the precipitation vessel, wherein the fresh brine may comprise calcium ions and magnesium ions, channeling the alkaline solution from the cathode chamber of the electrochemical reactor into the precipitation vessel, introducing the carbon dioxide via a flue gas pump to the precipitation vessel, removing any precipitate (e.g., from a treated brine solution, treated seawater, treated wastewater)in the precipitation vessel, wherein the precipitate and a treated brine solution are generated from (i) an alkaline solution channeled from the cathode chamber, (ii) the fresh brine, and (iii) the carbon dioxide, wherein the treated brine solution is absent of the calcium ions and the magnesium ions after removing any precipitate, and channeling the treated brine solution from the precipitation vessel to the cathode chamber and the anode chamber.

[0061] As mentioned above in various embodiments described for the system, the precpitation vessel and the cathode chamber may be in direct fluid communication with each other. In other words, the alkaline solution from the cathode chamber can be introduced directly into the precipitation vessel and the treated brine solution from the precipitation vessel can be channeled directly into the cathode chamber, i.e., no intervening units that intercepts aforesaid flows of the alkaline solution and the treated brine solution.

[0062] In various embodiments, the method is absent of the use of, for example, externally added NaOH, i.e., the alkaline solution does not involve an externally added sodium hydroxide.

[0063] In various embodiments, introducing the fresh brine may comprise introducing the fresh brine into the precipitation vessel via the first inlet, and / or channeling the alkaline solution may comprise channeling the alkaline solution into the precipitation vessel via the second inlet, and / or introducing the carbon dioxide may comprise introducing the carbon dioxide into the precipitation vessel via a third inlet.

[0064] In various embodiments, removing any precipitate may comprise filtering any precipitate from the treated brine solution, and discharging any precipitate via the second outlet, wherein the second outlet may be configured proximal to the bottom end and configured vertically above or at the same height as the filter.

[0065] In various embodiments, channeling the treated brine solution from the precipitation vessel to the cathode chamber and the anode chamber may comprise channeling the treated brine solution from the first outlet to the electrochemical reactor via the pipe, wherein the pipe may branch into two (e.g., channels), with one (channel) connected to the cathode chamber and the other (channel) connected to the anode chamber, so as to direct the treated brine solution from the precipitation vessel directly into the cathode chamber and / or the anode chamber. Non-limiting examples of theconfiguration (e.g., Y-junction, T-junction, splitter fitting) of such pipe have been discussed above and hence not reiterated for brevity.

[0066] In various embodiments, the method may further comprise operating the Raman module comprising the Raman probe having a sensor end configured in the precipitation vessel proximal to the filter to detect for any precipitate, generating the Raman spectrum corresponding to the type of precipitate, if any precipitate is detected, and identifying the type of precipitate from the Raman spectrum.

[0067] In various embodiments, the method may further comprise introducing air to the cathode chamber, operating the electrochemical reactor to render an oxygen reduction reaction in the cathode chamber in the presence of the oxygen so as to generate the alkaline solution, wherein the alkaline solution comprises OH ions, and / or operating the electrochemical reactor to render a hydrogen evolution reaction in the cathode chamber so as to generate hydrogen and an alkaline solution, wherein the alkaline solution comprises OH’ ions.

[0068] Advantages of aforesaid embodiments and features of the system and method are already demonstrated in one or more examples below, hence not reiterated for brevity. Also, the various steps involved in the method are described in the examples and hence not reiterated for brevity.

[0069] The word “substantially” docs not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the present disclosure.

[0070] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0071] In the context of various embodiments, the tilde symbolthe term “about”, and the term “approximately”, as applied to a numeric value encompasses the exact value and a reasonable variance. The variance may be ±20%, ±10%, ±5%, +1%, +0.5%, +0.1%, etc.

[0072] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0073] Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" languagesuch that they include recited elements but also permit inclusion of additional, unrecited elements.Examples

[0074] The system and method of the present disclosure, are described in further details, by way of non-limiting examples, as set forth below.

[0075] Example 1: System Configuration and Process Operation

[0076] From the example(s), it can be seen that the system and method provide an improved process for removing precipitations from a electrochemical reactor, can be applied in the electrolysis of brine and / or seawater (and any wastewater). The system and method can involve a precipitation vessel, and an electrochemical reactor configured as a flow cell (c.g., sec FIG. 1). The schematic representation of the system and method is provided in FIG. 1, which illustrates the complete mitigation of electrode scaling issues and recovering minerals from, for example, brine. The fresh brine 10, which contains mineral ions (e.g., Ca2+and Mg2+), is delivered to a precipitation vessel, wherein the fresh brine 10 reacts with a OH’ ions enriched brine solution 30 from the electrochemical reactor, and CO2 is captured. In the precipitation vessel, precipitates are generated (Ca2++ Mg2++ CO2+ 4OH CaCO3+ Mg(OH)2+ H2O). The OH ions enriched brine solution is generated from the cathode compartment (i.c., cathode chamber) of the electrochemical reactor. The precipitates can be discharged from the precipitation vessel to achieve continuous operation. After filtration at the bottom of the precipitation vessel, the treated brine (stream 20), absent of Mg2+and Ca2+ions, is configured into two streams. One stream is configured to flow through the cathode chamber of the electrochemical reactor, while the other stream is configured to flow through the anode chamber. Under the action of electricity, oxygen in the air reacts with the water in the treated brine to generate OH’ ions via the oxygen reduction reaction (ORR: O2 + 2H2O + 4e — > 4OH ’). Since no Ca2+and Mg2+ions exists in the treated brine, so no fouling / scaling issues due to precipitates arises in the electrochemical reactor. The waste brine (stream 40) after the anode chamber can be discharged. Under a static state operation, the flow rate of stream 40 can be the same as stream 10. The system advantageously simplifies the electrochemical reactor configuration comparedto any traditional electrochemical reactors that were modified to handle undesirable precipitates generation.

[0077] To test the system and method, a flow cell (i.e., the electrochemical reactor) with a working area of 16 cm2was assembled, and a series of experiments were conducted in the lab. Peristaltic pumps were used to drive the brine flow through the precipitation vessel and electrochemical reactor. The system was operated for the process to be conducted using an electrochemical reactor (flow cell) at three different currents (reaction rate). Here, 200 mA was selected as the representative and nonlimiting current only for the purpose of demonstrating mineral recovery from a desalination brine solution without encountering electrode fouling / scaling issues (FIG. 2A to FIG. 2D). The brine flow rate is 25 mL / h for the cathode, anode, and fresh brine to cathode effluent beaker (i.e., the precipitation vessel). Compressed air, with a flow rate of 20 seem, is supplied to the cathode chamber, while flue gas (composed of 5% CO2 and 95% air) is bubbled into the cathode effluent solution (solution in the precipitation vessel) at a flow rate of 10 seem. After 4 hours of reaction, no observable precipitation is observed in the cathode chamber of the electrochemical reactor (FIG. 2D). However, a significant amount of precipitate was collected in the precipitation vessel, demonstrating that the system and process can be continuously operated without suffering from downtime due to fouling / scaling issues at an electrode in the electrochemical reactor. It is noted here that the precipitate formation may occur when the OH’ ions from the cathode chamber contact with the fresh brine solution outside the precipitation vessel. To maintain uninterrupted mineral recovery, filtered brine was continuously withdrawn from the precipitation vessel for channeling back to both the anode and cathode chambers. The cell voltage for the configured electrochemical reactor during the production of OH ions enriched brine and the process operation for mineral recovery from the fresh brine solution was -2.3 V (FIG. 3A and 3B), indicating an energy-efficient carbon mineralization process. The X-ray diffraction (XRD) result reveals that the precipitate (four washes with water) consists of brucite (Mg(OH)i), calcite (CaCO?,), aragonite (CaCOj), magnesite (MgCCh), and hydromagnesite (Mgs(CO3)4(OH)2-4H2O), with respective phase compositions of 76.95%, 17.13%, 4.98%, 0.38%, and 0.56% (FIG. 4). The presence of carbonate minerals (-23%) is mainly attributed to the continuous introduction of flue gas into the precipitation vessel.Over a 4-hour process operation period, the pH in the precipitation tank slightly dropped from 13.14 to 12.51 (FIG. 5), indicating a sufficient production of OH ions for the precipitation of Mg2+in the continuous mineral recovery process. However, this pH also indicates that the mass transfer between flue gas and brine solution may be limited, as indicated by the relatively low consumption of OH" ions for CO32" ion formation. However, this can be readily dealt with by configuring the flue gas flow rates to achieve higher CO2 capture rates.

[0078] Example 2: Analysis of Mineral Yields

[0079] The mineral yield (four washings with water molecules) after 4 hours of reaction time was measured to be -696 mg. This value is slightly higher than a theoretical yield of -633 mg. calculated based on the volume of fresh brine introduced into the precipitation vessel and accounting for the precipitation of brucite and calcite. The obtained yield further suggests the formation of other carbonate minerals, such as hydromagnesite and magnesite, in addition to CaCOs due to the introduction of flue gas into the precipitation vessel. Hence, the experimental precipitation demonstrated the efficient and simultaneous removal of Mg2+and Ca2+ions from the desalination brine solution under the applied current of 200 mA. This was verified using thermodynamic modelling software VMinteq, where simulations were run similar to the experimental conditions, i.c., OH" enriched brine solution was added to the brine solution along with flue gas composition. The simulation showed the condition where the Mg and Ca can be simultaneously extracted from the brine as precipitates based on CO2 and OH" concentrations.

[0080] Example 3: Energy Consumption

[0081] The system and process experiments were further studied at a relatively lower applied current of 110 mA to reduce energy consumption and minimize the unused OH ions in the continuous process system while keeping all other experimental parameters constant. As anticipated, the cell potential is less than 2 V, indicating low energy consumption, and it remained stable for 4 hours during the mineral recovery process (FIG. 6). The system and process operated continuously without encountering any fouling / scaling issues, demonstrating an advantageous and efficient design for mitigating electrode fouling / scaling problems even at a lower applied current of 110 mA. However, the pH value in the precipitation vessel ranged from -10.1 to -10.5during the process run. This suggests that the pH obtained from the cathode effluents at an applied current of 110 mA may not be sufficient for capturing minerals in the brine solution for prolonged operation. This was supported by observing a small quantity of precipitation in the cathode chamber of the electrochemical reactor, indicating incomplete recovery of Mg2+ions by OH' ions at a pH of -10. From these results, it may be understood that effective and sustainable mineral recovery may be poorer for an electrochemical reactor with a working area of 16 cm2at currents of 110 mA or lower.

[0082] Example 4: Raman Spectrum Analysis

[0083] In the present system and process, an in-situ Raman analyzer was integrated in the electrolysis run at 200 mA in a H-cell. The in-situ Raman analyzer helps in real time monitoring of the precipitation process as seen in FIG. 7 A and FIG. 7B. FIG. 7 A shows the Raman spectra of Mg(0H)i formation and FIG. 7B shows the Raman spectra of Carbonate ion and CaCOs formation. The formation of Mg(0H)2 and CaCOs was also seen from the XRD diffractogram. The Raman analysis helps to demonstrate the efficient and simultaneous removal of Mg2+and Ca2+ions from the desalination brine solution.

[0084] Example 5: Durability Studies

[0085] Determining whether the system can operate for a long time without scaling for practical application was also investigated. To study the system’s durability, experiments were conducted at 200 mA for 112 hours. The fresh softened-brine solution was allowed to flow through between each cycle and the filter at the end of the inlet tube was replaced. It is found that despite a slight increase in cell voltage at the initial stage, the system remained stable for 6 consecutive cycles (>100 hours, FIG. 9A). It is noteworthy that there was no precipitate formation observed in the electrochemical reactor or on the electrode surface (FIG. 9B) for more than 100 hours, confirming the successful avoidance of electrode fouling / scaling issues through the improved system and process for the mineral recovery process. As shown in FIG. 9C, approximately 20 grams of mineral precipitates were generated, very close to the theoretical amount (2000 ppm Mg2+and 615 ppm Ca2+, resulting in Mg(OH)2 and CaCOs, approximately 19 grams).

[0086] Example 6: Summary

[0087] The present system and method are operable for removing precipitates from the electrochemical reactor for resource recovery from brine and / or seawater. The system and method involve: (1) a precipitation vessel and (2) an electrolysis reactor or an electrochemical reactor. The operation steps of the process can include:• The fresh brine / seawater, which contains mineral ions (Ca2+and Mg2+), reacts with alkaline brine generated from the electrochemical reactor to capture CO2 and generate precipitates in the precipitation vessel (Ca2++ Mg2++ CO2 + 4OH" —> CaCCh + Mg(0H)2+ H2O).• The precipitates can be discharged from the precipitation vessel to achieve continuous operation. The treated brine (where Ca2+and Mg2+are removed, stream 20 in FIG. 1) can be configured into two streams, i.e., one stream flows through the cathode chamber of the electrochemical reactor, while the other stream flows through the anode chamber.• Under the action of electricity, oxygen in the air reacts with the water in the treated brine to generate hydroxide ions via the oxygen reduction reaction (ORR: O2 + 2H2O + 4e > 4OH") in the electrolysis reactor.• The alkaline brine from the cathode chamber in the electrochemical reactor can be introduced into the precipitation vessel for continuous operation. Since no Ca2+and Mg2+ions arc in the treated brine (stream 20), it follows that no fouling / scaling issues are encountered in the electrochemical reactor.

[0088] The system and method of the present disclosure are able to address the challenges associated with electrode fouling / scaling in a carbon mineralization process. The system and method involve generation of precipitates outside of an electrochemical reactor with the cathode electrode exclusively producing OH" ions, resulting in an alkaline brine solution. When the OH" ions-enriched brine solution interacts with a fresh brine solution outside the electrochemical reactor in the precipitation vessel, precipitation of bruci te can occur. The flue gas, containing 5% CO2 in the air, is bubbled into the precipitation vessel, initiating the generation of carbonate (CO32’) ions. The CO32" ions subsequently react with Ca2+ions, precipitating the calcite phase. Additionally, the bubbling of CO2 enhances the conversion of Mg(0H)2to magnesium carbonates. Thus, the overall process leads to the complete or substantial removal of Mg2+and Ca2+ions from the fresh brine solution in the precipitation vessel. Theprecipitates in the precipitation vessel can be discharged. The treated brine solution, now free from Mg2+and Ca2+ions, can be reintroduced into the cathode and anode chambers (e.g., using peristaltic pumps). Therefore, the process can operate continuously without encountering the fouling / scaling issues in the electrochemical reactor, ensuring efficient and uninterrupted mineral recovery while continuously capturing CO2. Another advantage of the present system and method lies in the inclusion of online monitoring method using Raman. The Raman analyzer module is capable of real time monitoring of the precipitation process. This helps in the real time characterisation the precipitates and the solute species, like carbonate ions. Such information helps in developing and configuring for the control of the precipitate and the process irrespective of the scale of the electrolysis process.

[0089] Example 7: Commercial Applications

[0090] In general, the system and method of the present disclosure provide an approach for continuously solving the fouling / scaling issues towards a sustainable seawater and / or brine electrolysis system, including green H2 production from seawater electrolysis using hydrogen evolution reaction (HER: 2H2O + 2e — > 2OH" + H2) at the cathode side.

[0091] The system and method of the present disclosure can be applied broadly in resource recovery from brinc / scawatcr and various waste streams from cement, concrete, mining, steel industry, etc.

[0092] The system and method of the present disclosure enables the continuous production of sustainable construction materials, including CaCOs and Mg(OH)2, which can be utilized as additives or fillers in concrete applications.

[0093] With regard to carbon capture technology, the present system and method integrates process analytical technologies (PATs), for example, the Raman module mentioned above. Through PATs, real time data collection and analysis help in real time characterisation, control and configuring of the electrolysis process and controlling the precipitate products properties.

[0094] The system and method of the present disclosure can be used to develop CO2 mineralization technology, allowing for direct capture of CO2 emissions from fossil fuel combustion and other sources.

[0095] The system and method of the present disclosure can be used for extracting metals from brine, seawater, concrete and / or mining wastewater, and other sources. The system and method of the present disclosure can be used in CO2 capture in coal or NG- fired plants (NG denotes natural gas), desalination, and steel manufacturing. The system and method of the present disclosure can be used in facilitating scale-up of green H2 production from seawater.

[0096] While the present disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims. The scope of the present disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims arc therefore intended to be embraced.

Claims

CLAIMS1. A system for avoiding fouling or scaling of an electrode used in electrolysis, the system comprising: an electrochemical reactor having a cathode chamber and an anode chamber, wherein the cathode chamber is in fluid communication with a precipitation vessel; a fresh brine pump operable to deliver fresh brine to the precipitation vessel, wherein the fresh brine comprises calcium ions and magnesium ions; and a flue gas pump operable to deliver carbon dioxide to the precipitation vessel; wherein the precipitation vessel is configured to remove any precipitate, wherein the precipitate and a treated brine solution are generated from:(i) an alkaline solution channeled from the cathode chamber,(ii) the fresh brine, and(iii) the carbon dioxide, wherein the treated brine solution is absent of the calcium ions and the magnesium ions after removing any precipitate, and the treated brine solution is channeled from the precipitation vessel to the cathode chamber and the anode chamber.

2. The system of claim 1, wherein the precipitation vessel comprises a first inlet for receiving the fresh brine.

3. The system of claim 1 or 2, wherein the precipitation vessel comprises a second inlet for receiving the alkaline solution from the cathode chamber.

4. The system of any one of claims 1 to 3, wherein the precipitation vessel comprises a third inlet for receiving the carbon dioxide.

5. The system of any one of claims 1 to 4, wherein the precipitation vessel comprises a bottom end configured with a first outlet which the treated brine solution flows out from.

6. The system of claim 5, wherein the precipitation vessel comprises a filter configured proximal to the bottom end.

7. The system of claim 6, wherein the precipitation vessel comprises a second outlet configured proximal to the bottom end and configured vertically above or at the same height as the filter, wherein the second outlet is configured to discharge any precipitate.

8. The system of claim 6 or 7, further comprising: a Raman module comprising a Raman probe operable to detect any precipitate, and if any precipitate is present, aid in generating a Raman spectrum corresponding to a type of precipitate for identifying the type of precipitate, and wherein the Raman probe has a sensor end configured in the precipitation vessel proximal to the filter.

9. The system of any one of claims 5 to 8, wherein the third inlet extends into the precipitation vessel further than the first inlet and the second inlet so as to direct the carbon dioxide toward the bottom end for contacting with the alkaline solution and the fresh brine.

10. The system of any one of claims 5 to 9, further comprising a pipe connecting the first outlet to the cathode chamber and the anode chamber, wherein the pipe branches into two, with one connected to the cathode chamber and the other connected to the anode chamber, so as to direct the treated brine solution from the precipitation vessel directly into the cathode chamber and the anode chamber.

11. The system of claim 10, wherein the pipe comprises a T-junction, a Y-junction, or any splitter fitting which branches the pipe into two.

12. The system of any one of claims 1 to 11, wherein the electrochemical reactor comprises an air inlet configured at the cathode chamber for receiving air.

13. The system of any one of claims 3 to 12, wherein the electrochemical reactor comprises an outlet connected to the second inlet for channeling the alkaline solution from the cathode chamber directly into the precipitation vessel.

14. The system of any one of claims 1 to 13, wherein the electrochemical reactor comprises a discharge outlet at the anode chamber, wherein the discharge outlet is configured to discharge any brine.

15. A method for avoiding fouling or scaling of an electrode used in electrolysis via the system of any one claims 1 to 14, the method comprising: introducing the fresh brine via the fresh brine pump to the precipitation vessel, wherein the fresh brine comprises calcium ions and magnesium ions; channeling the alkaline solution from the cathode chamber of the electrochemical reactor into the precipitation vessel; introducing the carbon dioxide via a flue gas pump to the precipitation vessel; removing any precipitate in the precipitation vessel, wherein the precipitate and the treated brine solution are generated from:(i) an alkaline solution channeled from the cathode chamber,(ii) the fresh brine, and(iii) the carbon dioxide, wherein the treated brine solution is absent of the calcium ions and the magnesium ions after removing any precipitate, and channeling the treated brine solution from the precipitation vessel to the cathode chamber and the anode chamber.

16. The method of claim 15, wherein: introducing the fresh brine comprises introducing the fresh brine into the precipitation vessel via the first inlet; and / or channeling the alkaline solution comprises channeling the alkaline solution into the precipitation vessel via the second inlet; and / or introducing the carbon dioxide comprises introducing the carbon dioxide into the precipitation vessel via a third inlet.

17. The method of claim 15 or 16, wherein removing any precipitate comprises filtering any precipitate from the treated brine solution, and discharging any precipitate via the second outlet, wherein the second outlet is configured proximal to the bottom end and configured vertically above or at the same height as the filter.

18. The method of any one of claims 15 to 17, wherein channeling the treated brine solution from the precipitation vessel to the cathode chamber and the anode chamber comprises: channeling the treated brine solution from the first outlet to the electrochemical reactor via the pipe, wherein the pipe branches into two, with one connected to the cathode chamber and the other connected to the anode chamber, so as to direct the treated brine solution from the precipitation vessel directly into the cathode chamber and the anode chamber.

19. The method of any one of claims 15 to 18, further comprising: operating the Raman module comprising the Raman probe having a sensor end configured in the precipitation vessel proximal to the filter to detect for any precipitate; generating the Raman spectrum corresponding to the type of precipitate, if any precipitate is detected; and identifying the type of precipitate from the Raman spectrum.

20. The method of any one of claims 15 to 19, further comprising: introducing air to the cathode chamber; operating the electrochemical reactor to render an oxygen reduction reaction in the cathode chamber in the presence of the oxygen so as to generate the alkaline solution, wherein the alkaline solution comprises OH ions; and / or operating the electrochemical reactor to render a hydrogen evolution reaction in the cathode chamber so as to generate hydrogen and the alkaline solution, wherein the alkaline solution comprises OH ions.

Images