Desalination apparatus and method for recovery and valorization of chlorides in dilute solutions

Abstract

The present invention relates to a desalination device and method for NaCl solution using a three-compartment electrochemical cell separated by relevant ion exchange membranes, i.e. a continuous succession of a cathode compartment (16; 116), a cation exchange membrane (28; 128), a central compartment for salt solution (12; 112), an anion exchange membrane (26; 126) and an anode compartment (14; 114). In OH ‑ and H2 formation, the oxidation of OH ‑ and the reduction of H3O + lead to the passage of Na + and Cl ‑ ions from the central compartment to the other compartments, thus reducing the salt concentration. The feed of the cathode compartment can be managed in a circuit interposed with a carbonation reactor (50) to reduce the concentration of NaOH and eliminate CO2 from the air. Under certain conditions, the chloride entering the anode compartment undergoes oxidation, with the formation of chlorine gas which reacts with water to produce HCl and HClO.

Description

Technical Field

[0001] The present invention relates to desalination apparatus and methods, by way of non-limiting examples, for the recovery and valorization of chlorinated solutions from industrial, mining or water treatment wastewater (including seawater), for example for the production of bactericides and the sequestration of atmospheric CO2. Background Technology

[0002] Reducing chloride levels to levels that allow spillage into surface water (typically around 1,000 ppm) is one of the major challenges in the water treatment sector because chlorides, unlike other elements or compounds (such as calcium, magnesium, sulfates, etc.), cannot be treated in physicochemical plants using sparingly soluble salts, oxides, hydroxides, or flocculants.

[0003] However, chlorides are among the most common pollutants in wastewater generated from industrial processes (such as food, textiles, metal processing, and the power industry), mining, oil extraction (hydraulic fracturing), and last but not least, activities related to seawater desalination for the production of drinking water for human consumption.

[0004] To date, the most commonly used methods for reducing chloride levels below the limits permissible for spillage into surface water largely depend on the chloride concentration level. At concentrations close to the threshold (<5,000 ppm), wastewater is typically mixed with other wastewater containing low chloride levels, and the resulting mixture is then subjected to chemical and physical treatment. For concentrations above 70,000 ppm, the only applicable techniques involve evaporation methods, which recover a volume of water by concentrating it until (potentially) saturation, followed by solid-state chloride recovery. At moderate concentrations between 5,000 and 70,000 ppm, the method typically involves sequentially applying purification through a permeable membrane, thereby evaporating and recovering the concentrated impermeable material.

[0005] Undoubtedly, given the high costs of plants and energy associated with reverse osmosis and evaporation treatments, fraudulent practices such as environmental spillage or relocation to countries with inadequate environmental regulations that allow spills into surface water are not uncommon, where possible.

[0006] Another method, developed in the early 2000s and marketed by the applicant under the name SMIT, is described in the subject matter of European Patent EP3250 516. It specifies the use of an electrochemical device to extract chloride salts dissolved in an aqueous solution, while simultaneously producing a depleted chloride salt and an aqueous solution of two compounds—one being hydrochloric acid (HCl) and the other a base—through a reverse acid-base neutralization process. The method disclosed in the aforementioned patent specifies the use of two catalyst-rich electrodes. By supplying the battery with atmospheric oxygen and hydrogen, two chemical reactions can be achieved on the electrode surfaces, thereby producing H₂ on one side. + Ions, OH- is generated on the other side - Ions. Due to the principle of electroneutrality in aqueous solutions, increasing the concentration of these ion species in a chamber containing two electrodes involves replacing the charged ion species contained in the treated brine with specialized anion and cation exchange membranes, thereby subsequently resulting in ion fixation.

[0007] Despite the significant advantages this technology offers, as it allows for the chemical enhancement of treated brine and the subsequent generation of electricity from the electrochemical processes involved, several problems exist, summarized below:

[0008] The high cost of catalysts used in electrode production (such as platinum oxide) means that the initial costs of building a plant are very high, making catalyst application possible only when the treated wastewater requires very high disposal costs. Neither the acidic nor the alkaline solutions produced can be generated at the desired concentrations because, in the case of acidic solutions, the pH of both solutions must be maintained above 1, while in the case of alkaline solutions, the pH of both solutions must be maintained below 13.

[0009] H cannot be controlled using spontaneous reactions. + and OH - The rate of ion generation is directly proportional to the conductivity of the treated brine. This phenomenon involves a decrease in the ion generation rate as the salinity of the treated brine decreases, making this technology uneconomical for brine with chloride content below 35,000 ppm.

[0010] Finally, because the batteries require hydrogen, SMIT-type plants need to be flanked by facilities for in-situ hydrogen production. These facilities can be constructed using water electrolysis or reforming of fossil and non-fossil hydrocarbons. In applications near urbanized areas, this is not a limiting factor; however, it does represent a technological limitation when the area where the plant is located lacks the resources to manage a continuous supply of hydrocarbons.

[0011] The desalination system described in WO 2016 / 120717 A1 works in conjunction with a diffusion electrode to oxidize H2 at the anode to form H2. +And at the cathode, O2 is reduced to form OH. - This allows brackish water to be turned into drinking water. Summary of the Invention

[0012] The purpose of this invention is to overcome the above-mentioned disadvantages and to provide an apparatus and method for recovering and increasing chloride concentration in diluted solutions (particularly brine with chloride concentrations below 35,000 ppm and above 5,000 ppm).

[0013] The present invention also aims to provide an apparatus and method for recovering chloride-containing solutions, which have low management and investment costs and can chemically enhance the value of the treated compounds.

[0014] Further objects or advantages of the present invention will become apparent from the following description.

[0015] In a first aspect of the invention, the objective is achieved by means of a desalination device comprising at least one electrochemical cell, the desalination device comprising:

[0016] (a) Anode, which is suitable for allowing OH to occur - Ion oxidation and subsequent production of gaseous oxygen and H + An electrochemical reaction in which protons are released in solution, wherein the anode is contained in an anode chamber adapted to contain or contain an acid solution as an anolyte;

[0017] (b) A cathode, which is electrically connected to the anode and adapted to allow protons H to pass through. + Reduction and subsequent hydrogen and OH - Electrochemical reactions that release ions in solution are made possible, wherein the cathode is contained in a cathode chamber adapted to contain or contain an alkaline solution as the cathode electrolyte, particularly an aqueous solution of NaOH.

[0018] (c) A system for feeding anolyte into the anode chamber;

[0019] (d) A system for feeding cathode electrolyte into the cathode chamber;

[0020] (e) Cation exchange membrane, which is effective against OH- - Ions are not permeable, especially to cations such as Na+. + It has permeability;

[0021] (f) Anion exchange membrane, which has high sensitivity to H+. + Ions are not permeable, especially to cations, Cl. - It has permeability;

[0022] The anode chamber and the cathode chamber are separated by the cation exchange membrane and the anion exchange membrane, which are further separated by a third chamber suitable for containing or containing an aqueous solution of chloride salts (especially NaCl).

[0023] in

[0024] (α) The cation exchange membrane is simultaneously a wall or part of the wall of both the cathode chamber and the third chamber, enabling salt cation channels (particularly for Na) + It is possible to access the cathode chamber from the third chamber;

[0025] (β) The anion exchange membrane is simultaneously a wall or part of the wall of both the anode chamber and the third chamber, allowing salt anions (especially Cl-) to pass through. - The passageway leads from the third chamber to the anode chamber.

[0026] In preferred variations, the electrode is made of stainless steel or graphite. Advantageously, the membrane is made of a reinforced polymer material (particularly polyketone (PK)). The materials of the electrode and membrane can differ; they must simply be suitable for the reactions and permeabilities specified above. Suitable electrodes and membranes can be readily identified by those skilled in the art.

[0027] In a preferred embodiment of the invention, the desalination device (i.e., the associated control unit suitable for managing the various components included in the device) is configured to execute the following algorithm:

[0028] (i) The anode chamber (14; 114) is fed by a system for feeding anolyte (preferably water) into the anode chamber;

[0029] (ii) The cathode chamber (16; 116) is fed by a system for feeding the cathode electrolyte (preferably water or a reduced concentration of the alkali produced therein) into the cathode chamber;

[0030] (iii) Feed a concentrated chloride salt solution into the third chamber (12; 112);

[0031] (iv) OH on the oxide anode (18) - Oxygen (O2) and H+ are formed. + Proton;

[0032] (v) Reduction of H on cathode (20) + It forms H2 hydrogen gas and OH-. - Hydroxide ions.

[0033] Anion exchange membrane retains protons H in the anodic acidification chamber + However, this allows for the transport of anions (such as chloride ions Cl-) from the central chamber. -This makes it possible. The central chamber is preferably constructed in a manner that allows for the transport of the treated salt solution and maximizes its residence time within the chamber while minimizing the active surface area used. The active surface refers to the two walls of the chamber defined by the anion exchange membrane and the cation exchange membrane, respectively.

[0034] Conversely, the cation exchange membrane will absorb OH- - Ions are retained in the alkaline production cathode chamber, while cations (such as sodium ions, Na+) are allowed to be transported from the central chamber. + ).

[0035] To ensure the continuity of the electrochemical reaction and the migration of salt ions from the solution to be treated in the anode and cathode chambers in the desalination apparatus according to the invention, each of the chambers is preferably provided with an inlet and an outlet, specifically as follows:

[0036] (a) The anode chamber is provided with an inlet for fresh anolyte and an inlet for salt-rich anions (especially Cl-). - The outlet of the anolyte (or its derivatives) and oxygen is a more acidic anolyte.

[0037] (b) The cathode chamber is provided with an inlet for fresh cathode electrolyte and an inlet for salt-rich cations (especially Na+). + The outlet of the cathode electrolyte, which is more alkaline than hydrogen; and

[0038] (c) The third chamber is provided with an inlet for the initial salt solution and an outlet for the salt solution to reduce its concentration.

[0039] In a particularly advantageous embodiment of the invention, the desalination device further includes:

[0040] (g) A gas-liquid separation device, particularly a gas-liquid scrubber, adapted to recover the generated hydrogen and connected to the outlet of the cathode chamber, preferably connected to a fuel cell.

[0041] Gas-liquid separation units enable the recovery of hydrogen produced from the alkaline production chamber (and therefore in the cathode chamber) for in-situ reuse, for example, for generating electricity via fuel cells. The generated electricity can be immediately used to power the electrochemical cells of the desalination unit, thereby reducing the electrical energy required from direct feed sources by up to 15%. Other gas-liquid separation systems are also known in the prior art.

[0042] According to a particularly preferred embodiment of the present invention, the desalination apparatus further comprises:

[0043] (h) A carbonation reactor having a cathode chamber comprising an inlet and an outlet connected to a circuit inserted into the carbonation reactor.

[0044] The carbonation reactor advantageously diffuses carbon dioxide-containing gas into the resulting alkaline solution and circulates it in a loop between the cathode chamber and the carbonation reactor. This process allows the pH of the alkaline solution to be maintained in a buffer, advantageously between 8.5 and 9.5, ensuring optimal membrane operation and durability. By maintaining the buffered pH, the concentration of reagents removed from the treatment solution can also be increased until a saturated carbonate solution is obtained, which can then be continuously removed from the solution by precipitation. When fed with atmospheric air, the reactor helps reduce its CO2 charge. Therefore, the carbonation reactor serves a dual purpose: maintaining the pH of the alkaline solution in the buffered cathode chamber and allowing the fixation of atmospheric carbon dioxide by producing solid carbonates and bicarbonates, which can be extracted from the solution by supersaturated crystallization.

[0045] Advantageously, the fresh anolyte is simply water or a solution with a pH close to 7, while the fresh catholyte is advantageously a diluted alkaline solution, preferably derived from recycled NaOH generated in the cathode chamber and buffered during the decarbonation reactor. The fresh salt solution is advantageously a concentrated NaCl solution.

[0046] These fresh solutions then undergo chemical reactions, such as in the anode chamber:

[0047] 2OH - →O2(g)+2H + +4e -

[0048] And in the cathode chamber:

[0049] 2H3O + +4e - →2OH - +2H2(g).

[0050] Then, acid is formed in the anode chamber and base is formed in the cathode chamber.

[0051] According to another aspect of the invention, there is an electrochemical cell suitable for a desalination apparatus according to the invention. This electrochemical cell preferably comprises:

[0052] (i) A first plate, which supports the anode chamber of the curved path in a first window applied to the first plate, the thickness of the first plate preferably not exceeding 6 mm relative to the plane of the curved path extension, and having an inlet and an outlet for the anode electrolyte at its end;

[0053] (ii) A second plate, which supports the central chamber of the curved path in a second window applied to the second plate, the thickness of the second plate preferably not exceeding 6 mm relative to the plane of the curved path, and having an inlet and an outlet for the salt solution at its end;

[0054] (iii) A third plate that supports the cathode chamber of the curved path in a third window applied to the third plate, the thickness of the third plate preferably not exceeding 6 mm relative to the plane of the curved path extension, and having an inlet and an outlet for the cathode electrolyte at its end;

[0055] (iv) The anion exchange membrane, which is inserted between the first plate and the second plate;

[0056] (v) the cation exchange membrane, which is inserted between the second plate and the third plate;

[0057] (vi) A plate anode, configured to be adjacent to the first plate on the side opposite to the position of the anion exchange membrane; and

[0058] (vii) A plate cathode, which is positioned adjacent to the third plate on the side opposite to the position of the anion exchange membrane;

[0059] The plates, membranes, and electrodes are stacked in the following order: anode, anode chamber, anion exchange membrane, central chamber, cation exchange membrane, and cathode.

[0060] Each plate is optionally provided with a plurality of first holes, which are arranged such that they are aligned when the plates overlap so that they can be connected to the associated fastening device;

[0061] Each plate has multiple second holes, divided into three pairs of holes for conveying the flow of anolyte, catholyte, and salt solution into separate channels. In each pair, one hole is used for the corresponding flow entering the system, and the other hole is used for exiting the system. The holes are arranged such that they align when the plates overlap so that they can connect to form separate channels for the relevant flows.

[0062] Each plate is preferably provided with multiple third holes for collecting gases formed in the anode and cathode chambers, respectively, and arranged in such a way that they are aligned when the plates overlap so that they can connect to form separate channels for the corresponding airflow in the respective chambers.

[0063] Each flow passes through the entire system along a channel formed by related overlapping holes, but communication with the inlet of the chamber is only achieved in the plate carrying the chamber dedicated to the flow of the related channel, which is achieved by allowing the flow to pass through the chamber and enter the corresponding outlet channel formed by the corresponding series of holes through the outlet of the chamber.

[0064] Electrochemical cells are implemented in the form of three plates with curved or serpentine chambers, which allows for the maximum surface area, thus maximizing the contact area between each chamber and the associated ion exchange membrane, minimizing the thickness or volume of the chambers themselves, and ensuring a consistent and uniform distribution of the corresponding solutions contained within the chambers by the actual layer extension of the chambers, while also guaranteeing periodic degassing. The curved shape allows for the creation of long pathways for the solution inside each chamber within a very small space.

[0065] Combined with optimized contact surfaces, this space saving makes it possible to reduce the membrane area required to separate individual cells, which is a very important fact given the high cost of membranes.

[0066] In a preferred embodiment, the desalination device comprises at least one of the aforementioned electrochemical cells. However, it is understood that the electrochemical cell may be equipped with other types of electrodes and supplied with other types of solutions to carry out other electrochemical reactions, and therefore is not strictly related to the desalination described.

[0067] Plate electrochemical cells can be supplemented with additional plates to form a cell stack, which can be used in the desalination device of the present invention, but can also be used in other contexts that require different solutions and electrode types, while still using the three-compartment principle of the smallest unit of the cell stack.

[0068] In a variant of the invention, multiple three-chamber electrochemical cells are combined into a battery stack in the following manner:

[0069] Variant (A), in which individual elements follow each other according to the following scheme:

[0070] [+AZC-][+AZC-] n n = 1, 2, ..., ;

[0071] Or based on:

[0072] Variant (B), in which individual elements follow each other according to the following scheme:

[0073] +AZC-CZA+AZC-CZA+.....+AZC-, which has a variable number of groups of AZC and CZA, wherein a unit with three adjacent chambers shares a corresponding electrode,

[0074] In variants (A) and (B), A is a plate with an anode chamber, Z is a plate with a central chamber, and C is a plate with a cathode chamber. The symbol "+" represents the anode, and the symbol "-" represents the cathode. An anion exchange membrane is placed between adjacent chambers A and Z, and a cation exchange membrane is placed between adjacent chambers Z and C.

[0075] For the two variants (A) and (B), the chambers of the same type are connected by the relevant inlets and outlets of the chambers and the corresponding holes in the plates.

[0076] The principle of the plate electrochemical cell will be explained later with reference to Figure 2, where the configuration (number and arrangement) of the holes used to connect the inlet and outlet of a single chamber can vary.

[0077] In embodiments of the invention for large-scale development of the technology, the desalination device comprises not only at least one electrochemical cell, but also multiple electrochemical cells, such as 50, in a multi-polar configuration containing alternating polarity cells in a stack. Advantageously, the active surface area of ​​the membrane and electrodes is approximately 1600 cm². 2 The batteries can be powered by a DC generator, with a voltage ranging from 0 to 9 volts. In a preferred embodiment of the invention, a constant voltage between 2.5 and 3.5 V and 4.5 to 6.5 mA / cm² are provided for each battery, for example, through a photovoltaic system and voltage stabilizer or through DC power supplied by a power source. 2 The current between these values. Alternatively or supplementally, it can be powered by the energy generated by the aforementioned fuel cell. The amperage depends on the conductivity of the brine being treated. For the same voltage, brine with lower salt content produces a lower current, therefore the above range can be extended to 0.5-6.5 mA / cm. 2 .

[0078] The flow of the salt solution to be treated is preferably kept stable in the central chamber of each cell, which in an exemplary form is achieved by using a peristaltic metering pump, which can be controlled by a programmable logic controller (PLC) by monitoring the conductivity of the solution being analyzed as it leaves the cell. Similarly, inside the anode and cathode chambers, the flow of the anolyte / cathode electrolyte (e.g., water flow) is advantageously kept stable, for example by using a peristaltic metering pump managed by a PLC, by monitoring the pH of the same solution being analyzed as it leaves the cell.

[0079] In this respect, the desalination apparatus according to the invention includes an adjustable-speed pumping system for feeding the chamber.

[0080] By controlling the pumping speed of the solution to be treated and the voltage applied to the battery, its desalination capacity can be continuously and dynamically controlled, ensuring that a solution with the desired chloride level can be obtained at the outlet of the central chamber.

[0081] In an alternative embodiment of the invention, the desalination apparatus further includes a reverse osmosis system for separating the solution leaving the central chamber into a freshwater fraction and a concentrated salt solution fraction, the latter being fed in a loop into the central chamber of the electrochemical cell. Preferably, the reverse osmosis apparatus is fed not only the salt solution leaving the central chamber but also brackish water. The salinity of the brackish water is equal to or at least similar to the salinity of the solution leaving the central chamber, to extract an additional portion of drinking water.

[0082] For example, in seawater treatment, this configuration can recover 100% of the water and extract it for drinking water, achieving zero discharge. This configuration is not the only applicable one. For example, in industrial water treatment, electrochemical cells are used to reduce chloride levels below those permissible to overflow into surface water.

[0083] Another aspect of the present invention relates to a desalination method comprising the following steps:

[0084] (a) Providing a desalination apparatus according to the invention;

[0085] (b1) Feed the anode electrolyte into the anode chamber, preferably water;

[0086] (b2) Provide the cathode chamber with a cathode electrolyte, preferably water or a reduced concentration of the alkali produced therein;

[0087] (b3) Feed a concentrated chloride salt solution into the third chamber;

[0088] (c1) OH- oxidized at the anode - Oxygen (O2) and H+ are formed. + ;

[0089] (c2) H reduced on the cathode + Hydrogen gas (H2) and OH- are formed. - hydroxide ions;

[0090] (d1) Response to H in the anode chamber + With the increase in ion concentration, salt anions (especially chlorides) are introduced from the third chamber into the anode chamber;

[0091] (d2) Response to OH in the cathode chamber - With the increase of ion concentration, salt cations (especially Na+) + It enters the cathode chamber from the third chamber.

[0092] This process uses the electrochemical cell or electrochemical cell stack of the present invention to reduce the salt content of the concentrated salt solution and simultaneously produce oxygen and hydrogen. The hydrogen, which cannot be contaminated by other gases, can be used for energy production. Conversely, the oxygen in the anode chamber can be converted through Cl... -The anodic oxidation process is contaminated with chlorine. The alkali produced in the cathode chamber can be used to capture CO2 from the atmosphere and produce carbonates and bicarbonates. Carbonation simultaneously converts the concentrated alkali into a diluted alkali solution, which can then be reintroduced into the cathode chamber, thus avoiding the need to introduce fresh cathode electrolyte.

[0093] In a preferred embodiment of the invention, the at least one electrochemical cell is configured for each cell to have a constant voltage of 2.5 to 3.5 V and an A / cm² voltage of 4.5 to 6.5 mA. 2 The current (in the case of saline solution with low salt concentration, one can imagine 0.5 to 6.5 mA / cm) 2 Operating within the range between [specific values], the oxidation of chloride in the anode chamber causes gaseous chlorine to form gaseous chlorine, which then spontaneously undergoes a disproportionation reaction, subsequently producing hydrochloric acid (HCl) and hypochlorous acid (HClO) in equal proportions. The following reaction is then added to the anode chamber:

[0094] 2Cl - →Cl2(g)+2e -

[0095] Cl2(g) + H2O → HCl (aq) +HClO (aq) .

[0096] A power supply voltage of at least 3 volts allows for the oxidation reaction of chloride within the acid chamber, producing gaseous chlorine. The gaseous chlorine diffusing in the aqueous solution spontaneously undergoes dismutation or a disproportionation reaction, producing hydrochloric acid and hypochlorous acid in equal proportions. Controlling the pumping rate of the feed water to the acid chamber allows for control of the ratio of hydrochloric acid to hypochlorous acid at the chamber outlet, thus obtaining a solution containing the desired amount of active chlorine, for example, in the production of disinfectants. To ensure a further increase in the concentration of active chlorine, it is advantageous to use a suitable alkali buffer to buffer the resulting acid solution. This process can further increase the residence time of the solution within the acidification chamber.

[0097] In an embodiment of the method according to the present invention,

[0098] (i) Feeding (acidic solution) into the anode chamber at a controlled flow rate and extracting an acidic solution containing oxygen, preferably containing HCl and HClO, from the anode chamber;

[0099] (ii) An alkaline solution (NaOH) is fed into the cathode chamber at a controlled flow rate, and the concentrated alkaline solution and hydrogen are extracted from the cathode chamber; and

[0100] (iii) A concentrated salt solution is fed into the central chamber at a controlled flow rate, and a diluted salt solution is extracted. The control of the rate allows for monitoring of the concentration of the aqueous components contained in the relevant chamber.

[0101] In embodiments of the method according to the invention, the feeding of the cathode chamber and the extraction of its contents occur in a loop from which hydrogen is transferred, preferably by feeding into the fuel cell, and comprising a carbonation reactor from which carbonates and / or bicarbonates are transferred, serving to buffer the pH of the alkaline solution returned to the cathode chamber, preferably between pH 8.5 and 9.5. The energy generated in the fuel cell can be used to power a desalination unit.

[0102] Another aspect of the invention relates to the use of the apparatus and desalination method, particularly for reducing the concentration of chlorides in brackish water, industrial, mining or water treatment waste, and seawater according to the invention, and also for one or more purposes selected from the group consisting of:

[0103] - Production of carbonates and / or bicarbonates;

[0104] - Eliminate carbon dioxide from the atmosphere;

[0105] - Producing hydrogen to generate energy;

[0106] - Produces HCl and HClO used in the manufacture of disinfectants.

[0107] The features and advantages disclosed in one aspect of the invention can be transferred to other aspects of the invention with necessary modifications.

[0108] Industrial applicability is evident when chloride concentrations from brackish water, seawater, industrial waste, etc., can be economically reduced (even to below 35,000 ppm), while simultaneously utilizing byproducts such as hydrogen, HCl / HClO, and NaOH to produce energy and carbonates / bicarbonates, and reducing the carbon footprint in the environment.

[0109] The objectives and advantages described herein will be further highlighted in the description of preferred embodiments of the invention, and are by way of non-limiting example only.

[0110] Variations and further features of the invention are the subject names of the dependent claims. The description of preferred embodiments of the apparatus, method, electrochemical cell, and uses in relation to the desalination, recovery, and enhancement of chlorides contained in diluted solutions according to the invention is given by way of non-limiting example only with reference to the accompanying drawings. In particular, unless otherwise stated, the number, shape, size, and material of the system and individual components may vary, and equivalent elements may be used without departing from the inventive concept. Attached Figure Description

[0111] Figure 1 shows a schematic diagram of the desalination apparatus according to the present invention.

[0112] Figure 2 shows a single component of an electrochemical cell that can be used in the device according to Figure 1. Detailed Implementation

[0113] Figure 1 shows a schematic diagram of a desalination apparatus according to the present invention. The apparatus includes an electrochemical cell 10 as a central component, comprising a central chamber 12, an anode chamber 14, and a cathode chamber 16. The anode chamber 14 contains an electrode, namely an anode 18. A corresponding electrode, namely a cathode 20, is located in the cathode chamber 16. Electrodes 18 and 20 are connected via a circuit 22 powered by a photovoltaic cell 24. Electrons move from the negative electrode 18 to the positive electrode 20. The anode chamber 14 is separated from the central chamber 12 by an anion exchange membrane 26, and the cathode chamber 16 is separated from the central chamber 12 by a cation exchange membrane 28. Each of the three chambers 12, 14, and 16 is provided with an inlet and an outlet: an inlet 30 and an outlet 32 ​​for the central chamber 12, an inlet 34 and an outlet 36 for the anode chamber 14, and an inlet 38 and an outlet 40 for the cathode chamber 16. Water (arrow a) is pumped into the anode chamber 14 by a pump 42 through inlet 34. Central chamber 12 is fed with a concentrated NaCl solution (arrow b) through inlet 30, for example, 70 g NaCl / L. A diluted alkaline aqueous solution (0.1 M NaOH) is pumped into cathode chamber 16 through inlet 38 using pump 44 (arrow c). At cathode 20, H3O... + The cation is reduced to form hydrogen gas (H2) according to the following reaction: 2H3O + +4e - →2OH - +2H2(g). The alkalinity of the solution in cathode chamber 16 is then increased. The NaOH solution exits cathode chamber 16 through outlet 40 (arrow d), thus becoming more concentrated (here, 1M). Simultaneously, the formed hydrogen gas exits through outlet 46 (arrow e), separating it from the aqueous NaOH stream, which is managed in loop 48 connecting inlet 38 and outlet 40 of cathode chamber 16. Carbonation reactor 50 is installed in loop 48. The concentrated NaOH solution leaving cathode chamber 16 enters reactor 50, which is fed with gas (i.e., air) through line 52 (arrow f) by pump 54. This gas contains carbon dioxide (CO2) that bubbles in reactor 50. Sodium carbonate and / or sodium bicarbonate are formed by the reaction of NaOH and CO2 in water, respectively, and can be discharged from reactor 50 via outlet 56. Reactor 50 has separation walls 58 for separating the formation of solid carbonates / bicarbonates from loop 48.

[0114] In anode chamber 14, OH - The ions are oxidized to form oxygen O2 according to the following reaction: 4OH-- →4e - +2H₂O+O₂(g). Because H₃O + Increased ion concentration leads to a lower pH value in aqueous solutions.

[0115] When the reaction occurs at electrodes 18 and 20, a concentrated NaCl solution is introduced into the central chamber 12 for dilution, because in response to OH... - With increasing concentration, Na + Cations pass through (arrow g) cation exchange membrane 28 in response to H3O. + With increasing concentration, Cl - Anions pass through (arrow h) anion exchange membrane 26. Approximately 35 g / L of diluted NaCl solution exits from outlet 32 ​​of central chamber 12. Cl- enters anode chamber 14. - The ions are oxidized at anode 18 to form chlorine gas (Cl2). The chlorine gas reacts with water to form HCl and HClO (approximately 1 mole), which exit from outlet 36 (arrow i).

[0116] The diluted salt solution leaving the central chamber 12 is mixed with a brine solution of similar concentration (arrow j) and pumped into the reverse osmosis unit 62 by pump 60 to obtain a fresh water fraction (arrow k) and a concentrated NaCl solution fraction (70 g / L), which are then pumped into the central chamber 12 by pump 64 to form a NaCl stream (arrow b).

[0117] Figure 2 shows a single component of an electrochemical cell that can be used in a factory according to Figure 1. From left to right, a first plate 166 with an anode chamber 114, a second plate 168 with a central chamber 112, and a third plate 170 with a cathode chamber 116 can be seen. Each chamber follows a curved or serpentine path.

[0118] In a three-chamber base cell comprising a series of three-chamber units existing independently or separately according to variant (A) or (B) described above, an anion exchange membrane 127 is always inserted between the anode chamber 114 and the central chamber 112, and a cation exchange membrane 128 is always inserted between the central chamber 112 and the cathode chamber 116. In the left plate 166, reference numeral 127 indicates the anion exchange membrane placed above the anode chamber 114; in the right plate 170, reference numeral 128 indicates the cation exchange membrane placed above the cathode chamber 116; and in the central plate 168, reference numeral 126 indicates a group of anion and cation exchange membranes (also indicated separately in the accompanying drawings on both sides), including the central chamber 112 sandwiched therein.

[0119] A base electrochemical cell is obtained by placing a second plate 168 above a first plate 166, placing a third plate 170 above the second plate 168, with an anion exchange membrane 127 between the first plate 166 and the second plate 168, and a cation exchange membrane 128 between the second plate 168 and the third plate 170. To connect one plate to another, multiple holes 172 are provided along the edge of each plate for passage through opposing fixtures. By repeatedly constructing electrochemical cells and placing one cell on top of another, in the order shown above, a stack of electrochemical cells that can be connected to work together is obtained. In this respect, each plate is provided with two three-hole assemblies, one for the outlet of the associated chambers 114, 112, and 116, and the other for the inlet of the associated chamber. The anode chamber 114 of the first plate 166 is connected at its end to the outlet hole 136 and the inlet hole 134; the central chamber 112 is connected at its end to the outlet hole 132 and the inlet hole 130; and the cathode chamber 116 is connected at its end to the outlet hole 140 and the inlet hole 138. Therefore, in an electrochemical cell stack, the outlets and inlets of individual chambers are connected together, creating distinct flows of anolyte solution, salt solution, and cathodic solution between chambers of the same category (anode, center, or cathode).

[0120] In addition, each plate has holes 146 and 147 that can be aligned in the stack for degassing the anode and cathode chambers that generate gas. In particular, in the case of the connected cathode chamber 116, the associated hole 146 is used to create a channel for transporting the generated hydrogen gas.

[0121] The board is made in chip form, for example, with a thickness of about 6 mm.

Claims

1. A desalination device comprising at least one electrochemical cell (10), said electrochemical cell comprising: (a) Anode (18), which is suitable for allowing OH to occur - Ion oxidation and subsequent oxygen production and H + An electrochemical reaction in which protons are released in solution, wherein the anode (18) is contained in an anode chamber (14; 114), the anode chamber (14; 114) being adapted to contain or contain an acidic solution as an anolyte; (b) A cathode (20), which is connected to the anode (18) via an electrical connector (22) and is adapted to allow protons H to be emitted. + Reduction and subsequent hydrogen and OH - An electrochemical reaction in which ions are released in solution, wherein the cathode (20) is contained in a cathode chamber (16; 116) which is adapted to contain or contain an alkaline solution as a cathode electrolyte; (c) A system for feeding the acidic solution into the anode chamber; (d) A system for feeding the alkaline solution into the cathode chamber; (e) Cation exchange membrane (28; 128), which is effective against OH- - Ions are not permeable, but cations are permeable; (f) Anion exchange membrane (26; 126), which is effective for H+ + Ions are not permeable, but anions are permeable; in, In terms of ion transport, the anode chamber (14; 114) and the cathode chamber (16; 116) are completely separated by the cation exchange membrane (28; 128) and the anion exchange membrane (26; 126), which in turn are completely separated by a third chamber (12; 112) suitable for containing or containing an aqueous solution of chloride salts. in (α) The cation exchange membrane (28; 128) is simultaneously a wall or part of the wall of the cathode chamber (16; 116) and the third chamber (12; 112), allowing salt cations to pass from the third chamber (12; 112) to the cathode chamber (16; 116). (β) The anion exchange membrane (26; 126) is simultaneously a wall or part of a wall of both the anode chamber (14; 114) and the third chamber (12; 112), allowing salt anions to pass from the third chamber (12; 112) to the anode chamber (14; 114); wherein the anode (18) and the cathode (20) are made of graphite, and wherein the desalination device further comprises: (h) Carbonation reactor (50), The cathode chamber (16) therein includes an inlet (38) and an outlet (40), the inlet (38) and the outlet (40) being connected to a loop inserted into the carbonation reactor (50).

2. The desalination device according to claim 1, characterized in that, The desalination device is configured to execute the following algorithm: (i) Feeding the anode electrolyte into the anode chamber (14; 114); (ii) Feeding cathode electrolyte into the cathode chamber (16; 116); (iii) Feed a concentrated chloride salt solution into the third chamber (12; 112); (iv) Oxidation of OH on the anode (18) - Oxygen (O2) and H+ are formed. + Proton; (v) Reduction of H on cathode (20) + It forms H2 hydrogen gas and OH-. - Hydroxide ions.

3. The desalination apparatus according to claim 1 or 2, characterized in that, Each of the chambers (12, 14, 16; 112, 114, 116) is provided with an entrance (30, 34, 38; 130, 134, 138) and an exit (32, 36, 40; 132, 136, 140), that is: (a) The anode chamber (14; 114) is provided with an inlet (34; 134) for fresh anolyte and an outlet (36; 136) for anolyte rich in salt anions and oxygen. (b) The cathode chamber (16; 116) is provided with an inlet (38; 138) for fresh cathode electrolyte and an outlet (40; 140) for cathode electrolyte rich in salt cations and hydrogen; and (c) The third chamber (12; 112) is provided with an inlet (30; 130) for an initial aqueous salt solution and an outlet (32; 132) for a salt solution with reduced concentration.

4. The desalination device according to claim 1, characterized in that, The desalination device further includes (g) A gas-liquid separation device adapted to recover the generated hydrogen and connected to the outlet of the cathode chamber (16; 116).

5. The desalination device according to claim 1, characterized in that, The at least one electrochemical cell includes (i) A first plate (166) supporting the anode chamber (114) of the curved path in a first window applied to the first plate, the first plate having an inlet and an outlet for the anolyte at its end; (ii) A second plate (168) supporting the third chamber (112) of the curved path in a second window applied to the second plate, the second plate having an inlet and an outlet for the salt solution at its end; (iii) A third plate (170) supporting the cathode chamber (116) of the curved path in a third window applied to the third plate, the third plate having an inlet and an outlet for the cathode electrolyte at its end; (iv) The anion exchange membrane (127) is inserted between the first plate (166) and the second plate (168); (v) The cation exchange membrane (128) is inserted between the second plate (168) and the third plate (170); (vi) A plate anode, which is configured to be adjacent to the first plate (168) on the side opposite to the position of the anion exchange membrane (127); and (vii) A plate cathode, which is positioned adjacent to the third plate (170) on the side opposite to the position of the anion exchange membrane (128); The plates, membranes, and electrodes are stacked in the following order: anode, anode chamber, anion exchange membrane, third chamber, cation exchange membrane, and cathode; Each plate has multiple first holes, divided into three pairs (134, 136; 130, 132; 138, 140) for conveying the flow of anolyte, catholyte, and salt solution into separate channels. One hole (134; 130; 138) in each pair is used for the corresponding flow entering the system, and the other hole (136; 132; 140) is used for exiting the system. The arrangement of the corresponding holes is such that they are aligned when the plates overlap so that they can connect to form separate channels for relative flow. Each flow passes through the entire system along a channel formed by related overlapping holes, but communication with the inlet of the chamber is only achieved in the plate carrying the chamber dedicated to the flow of the related channel, which is achieved by allowing the flow to pass through the chamber and enter the corresponding outlet channel formed by the corresponding group of holes through the outlet of the chamber.

6. The desalination device according to claim 5, characterized in that, The desalination device comprises multiple three-chamber electrochemical cells, which are arranged in a cell stack according to the following manner: Variant (A), in which individual elements follow each other according to the following scheme: [+AZC-][+AZC-] n n = 1, 2, ..., ; Or based on: Variant (B), in which individual elements follow each other according to the scheme: +AZC-CZA+AZC-CZA+.....+AZC-, having a variable number of AZC and CZA groups, wherein a unit having three adjacent chambers shares a corresponding electrode, In both variants (A) and (B), A is a plate (166) with an anode chamber (114), Z is a plate (168) with a third chamber (112), and C is a plate (170) with a cathode chamber (116). The symbol "+" represents the anode, and the symbol "-" represents the cathode. An anion exchange membrane (127) is placed between adjacent chambers A and Z, and a cation exchange membrane (128) is placed between adjacent chambers Z and C. For the two variants (A) and (B), the chambers of the same type are connected by the relevant inlets and outlets of the chambers and the corresponding holes in the plates.

7. The desalination apparatus according to claim 1, characterized in that, The desalination device comprises multiple electrochemical cells in a multipolar configuration within a stack containing alternating polarity cells.

8. The desalination apparatus according to claim 1, characterized in that, The desalination unit includes an adjustable-speed pumping system (42, 44, 64) for feeding the chamber.

9. The desalination apparatus according to claim 1, characterized in that, The alkaline solution is an aqueous solution of NaOH, and the salt cation is Na. + The salt anion is Cl. - The chloride salt is NaCl.

10. The desalination apparatus according to claim 2, characterized in that, The anolyte is water, and the catholyte is water or an alkali produced in the cathode chamber at a reduced concentration.

11. The desalination apparatus according to claim 3, characterized in that, The salt anion is Cl. - The salt cation is Na. + .

12. The desalination apparatus according to claim 4, characterized in that, The gas-liquid separation device is a gas-liquid scrubber, or it can be connected to a fuel cell.

13. The desalination apparatus according to claim 5, characterized in that, The thickness of at least one of the first plate, the second plate, and the third plate does not exceed 6 mm relative to the plane extending along the bending path.

14. The desalination apparatus according to claim 5, characterized in that, Each plate is provided with a plurality of second holes (172) arranged in such a way that they are aligned when the plates overlap so that they can be connected to the associated fixtures; or each plate is provided with a plurality of third holes (146, 147) for collecting gases formed in the anode chamber and cathode chamber (114, 116) respectively, and arranged in such a way that they are aligned when the plates overlap so that they can be connected to form separate channels for the associated airflow in the respective chambers.

15. A desalination method comprising the following steps: (a) Providing a desalination apparatus according to claim 1 or 2; (b1) Feed the anolyte into the anode chamber (14; 114); (b2) Supply cathode electrolyte to the cathode chamber (16; 116); (b3) Feed a concentrated chloride salt solution into the third chamber (12; 112); (c1) OH- oxidized at the anode - To form oxygen (O2) and protons (H2). + ; (c2) H reduced on the cathode + Hydrogen gas (H2) and OH- are formed. - hydroxide ions; (d1) Response to H in the anode chamber (14; 114) + With the increase of ion concentration, salt anions are introduced from the third chamber (12; 112) into the anode chamber (14; 114). (d2) Response to OH in cathode chamber (16; 116) - As the ion concentration increases, salt cations are introduced from the third chamber (12; 112) into the cathode chamber (16; 116); in which carbonates and bicarbonates (56) are transferred from the carbonation reactor, which serves to buffer the pH of the alkaline solution returning to the cathode chamber (16).

16. The method according to claim 15, characterized in that, (i) Feeding into the anode chamber (14; 114) at a controlled flow rate and extracting an oxygen-containing acidic solution from the anode chamber; (ii) A controlled flow rate is used to feed an alkaline solution into the cathode chamber (16; 116) and extract the concentrated alkaline solution and hydrogen from the cathode chamber; and (iii) The concentrated salt solution is fed into the third chamber (12; 112) at a controlled flow rate and the diluted salt solution is extracted from the third chamber, thereby allowing control over the concentration of the components of the aqueous solution contained in the relevant chambers (12, 14, 16; 112, 114, 116).

17. The method according to claim 15, characterized in that, The feeding of the cathode chamber (16) and the extraction of its contents occur in the circuit from which hydrogen (46) is transferred to the fuel cell, where the energy generated by the fuel cell is used to power the desalination unit.

18. The method according to claim 15, characterized in that, The anolyte is water, the catholyte is water or an alkali produced at a reduced concentration in the cathode chamber, and the salt anion is Cl. - The salt cation is Na. + .

19. The method according to claim 16, characterized in that, The anode chamber is filled with an acidic solution or water, and the alkaline solution is NaOH.

20. The method according to claim 15, characterized in that, The pH of the alkaline solution returned to the cathode chamber (16) is buffered between 8.5 and 9.

5.

21. The method according to claim 15, characterized in that, The flow of the salt solution to be treated remains stable in the third chamber of each cell, and the flow of anolyte and catholyte remains stable inside the anode and cathode chambers.

22. The method according to claim 21, characterized in that, The flow of the salt solution to be processed is kept stable in the third chamber of each cell by using a peristaltic metering pump controlled by a programmable logic controller (PLC) by monitoring the conductivity of the solution being analyzed as it leaves the cell. Similarly, in the anode and cathode chambers, the flow of the anolyte and catholyte is kept stable by using peristaltic metering pumps managed by the PLC, by monitoring the pH of the same solution being analyzed as it leaves the cell.

23. The use of the desalination apparatus according to claim 1 for reducing the concentration of chlorides in brackish water, industrial waste, mining or water treatment, and seawater, for one or more purposes selected from the group consisting of: - Produces carbonates or bicarbonates; - Eliminate carbon dioxide from the atmosphere; - Producing hydrogen to generate energy.

24. The use of the desalination apparatus according to claim 1 for reducing the concentration of chlorides in brackish water, industrial waste, mining or water treatment, and seawater, for the production of carbonates and bicarbonates.

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