Fixed bed electrochemical reactor based on at least one volume electrode, preferably based on biobased carbon, and use thereof in various applications and in particular for removing pollutants from a liquid medium

Abstract

The present invention relates to a fixed bed electrochemical reactor comprising at least a first volume electrode, preferably based on biobased carbon, and a separator configured to separate the first volume electrode from a second surface or volume electrode and to ensure compression at least on said first volume electrode, to the use thereof in various applications such as removing pollutants from a liquid medium comprising at least one organic pollutant, disinfecting water by electrochlorination, water electrolysis, seawater desalination, energy storage (e.g. as redox flow battery or supercapacitor), or the generation of electric power from osmotic power, and to a method for removing pollutants from a liquid medium comprising at least one organic pollutant used in said reactor.

Description

Fixed-bed electrochemical flow reactor based on at least one volume electrode, preferably based on bio-sourced carbon, and its use in various applications and in particular for decontaminating a liquid medium

[0001] The present invention relates to a fixed-bed flow electrochemical reactor comprising at least one first volume electrode, preferably based on biosourced carbon, and a separator configured to separate the first volume electrode from a second surface or volume electrode and to ensure compression at least on said first volume electrode, to its use in various applications such as the decontamination of a liquid medium comprising at least one organic pollutant, the disinfection of water by electrochlorination, the electrolysis of water, the desalination of seawater, the storage of energy (e.g. as a redox flow battery or supercapacitor), or the production of electrical energy from osmotic energy, and to a method for decontaminating a liquid medium comprising at least one organic pollutant used in said reactor.

[0002] Electrochemical processes differ from conventional chemical processes by the heterogeneous nature of the electrochemical reaction and by the presence of an electric field. Furthermore, they often use corrosive media (concentrated solutions, temperatures above room temperature, molten salts, organic media) and the materials of the parts constituting the cell must be chemically inert and retain their mechanical and thermal properties. In addition, the electrode materials are chosen to promote the desired electrochemical reaction and minimize the importance of side reactions such as degradation of the solvent or the products formed. The cells used in industry must meet these material criteria while minimizing the ohmic drop and ensuring a high transfer conductance value.Currently, most commercially available cells are of the filter press type (or capillary gap cell) comprising at least one electrode, at least one counter-electrode, and possibly at least one membrane interposed between the electrode and the counter-electrode. The electrode and the counter-electrode are flat and parallel. The electrolyte solution circulates in the cell through a thin channel. The filter press type cell is characterized by inter-electrode distances that can be very small (e.g. 0.2 mm), thus aiming to minimize ohmic drops. However, this type of cell can cause flow disturbances, with agitated zones, dead volumes, and in some cases short circuits.

[0003] The global contamination of surface water, groundwater, and drinking water by organic micropollutants such as cosmetics, pesticides, pharmaceuticals, and steroid hormones poses potential risks to human health and the ecosystem. Since organic micropollutants are resistant to biological degradation, most wastewater treatment plants cannot effectively remove them from treated effluents and cannot prevent them from entering the environment. Wastewater treatment processes to remove organic pollutants have been proposed. In particular, it is known to use electrochemical filter-press reactors to decontaminate effluents containing organic pollutants by oxidation. Decontamination is carried out by a process called the "electro-Fenton process," in which the hydroxyl radical (OH .), a powerful oxidant of organic pollutants, is produced from an aqueous solution containing ferrous ions and hydrogen peroxide. The ferrous ions themselves are generated electrochemically within the electrochemical reactor. There are two types of filter press reactors: intermittent flow with a single chamber, or continuous parallel flow in which the pollutants flow parallel to the surface of the anode and cathode. However, the efficiency of pollutant removal is not satisfactory.

[0004] Furthermore, other filter press type reactors have been proposed to carry out effluent decontamination by electro-Fenton. For example, Renet al., Chemical Engineering Journal, 2016, 298, 55-67 described a vertical flow reactor implementing the electro-Fenton process comprising a plurality of PbO2 anodes and a plurality of modified graphite felt cathodes alternating over about ten compartments. The pollutants flow perpendicular to the surface of the anodes and cathodes.

[0005] Although such reactors feature a continuous flow effluent feed, they generally have low pressure resistance. Electrodes designed in the form of plates are inserted into openings created in the reactor structure, which are sealed with silicone to prevent leaks. However, silicone does not have a high pressure resistance. In addition, the reactor design does not facilitate regular electrode replacement, an important step to maintain optimal performance under industrial conditions. Finally, lead is toxic, and although graphite is one of the most commonly used electrode materials, its production generates significant carbon emissions and / or requires significant energy input.

[0006] There is therefore a need for new electrochemical reactor architectures, particularly for effluent decontamination but also for other applications in the field of electrochemistry, which make it possible to improve electrochemical performance, while ensuring a reduction in the carbon footprint.

[0007] The invention relates to a fixed-bed electrochemical flow reactor, characterized in that it comprises:- at least one first volume electrode comprising an electrically conductive material, preferably a biosourced carbon,- at least one second surface or volume electrode comprising an electrically conductive material, the second electrode being electrically connected to said first electrode,- at least one first inlet and at least one first outlet, configured respectively to bring a liquid electrolyte in a continuous flow into the reactor, and to take said liquid electrolyte out in a continuous flow from the reactor, and- at least one separator comprising at least one dielectric part in contact with said first and second electrodes, said separator being configured to separate the first and second electrodes, to ensure compression on said first electrode,and to allow movement of the liquid electrolyte in a continuous flow from the first inlet to the first outlet.,

[0008] Thanks to the architecture of the reactor of the invention, and in particular thanks to the presence of at least one volume electrode and the presence of a separator which is configured to separate the first and second electrodes, to ensure compression on said first electrode, and to allow a movement of the liquid electrolyte in continuous flow from the first inlet to the first outlet, a better contact surface is thus obtained between the liquid electrolyte and the electrodes, and increased turbulence, which makes it possible to promote electrochemical transfers and mass transport with good homogenization of the reaction medium within the reactor. Furthermore, the reactor of the invention is robust, modular in that it can be used to implement various electrochemical processes, and adapted to the requirements of industry.The reactor allows in particular to adapt the mass volumes of the electrodes to optimize the efficiency of the specific electrochemical process implemented in said reactor. This reactor configuration is also suitable for parallel and series assembly to meet the needs of electrochemical processes in terms of flow and residence time.

[0009] The reactor of the invention is a fixed-bed flow electrochemical reactor. In other words, the liquid electrolyte moves within the electrochemical reactor in a continuous flow. The reactor is said to be fixed-bed. In other words, when the liquid electrolyte moves within the electrochemical reactor, and in particular passes through the first and second electrodes, said first and second electrodes remain fixed (i.e. are immobilized) and the liquid electrolyte passes through the empty spaces or holes. Consequently, the first and second electrodes remain in a static state during the movement of the liquid electrolyte. This thus makes it possible to avoid side reactions within the reactor.

[0010] The first electrode

[0011] The first volume electrode comprises an electrically conductive material, preferably a bio-sourced carbon.

[0012] The electrically conductive material may have an electrical resistivity of at most approximately 15,000 Ω.m, and particularly preferably ranging from 1x10 -8 Ω.m to about 1 Ω.m.

[0013] Particularly preferably, the first volume electrode is essentially made of a bio-sourced carbon.

[0014] In the invention, the term "essentially consisting" means that the biosourced carbon represents at least approximately 90% by mass, preferably at least approximately 95% by mass, and particularly preferably approximately 100% by mass, relative to the total mass of the first volume electrode.

[0015] In the invention, a bio-sourced carbon is a carbon derived from biomass or raw materials of plant and / or animal origin (and not of fossil or petrochemical origin). It is in particular obtained by extraction of biomass or raw materials of plant and / or animal origin, or obtained by reactions applied to biomass or raw materials of plant and / or animal origin.

[0016] Using bio-based carbon as a bulk electrode reduces electrode material costs, improves the efficiency of electrochemical reactions, and also reduces associated energy costs. Finally, bio-based carbon is a material that can be produced from renewable resources, offering a sustainable alternative to petroleum-based electrode materials that can present supply issues.

[0017] Biosourced carbon is preferably biochar.

[0018] Biochar is a contraction of "bio-charcoal," meaning a charcoal of plant origin. It is generally obtained by thermal treatment (pyrolysis or gasification) of one or more biomass sources such as by-products of the wood industry, crop residues, solid waste, green waste, food waste, etc.

[0019] According to a particular embodiment of the invention, the biochar is obtained by heat treatment of one or more sources of biomass at a temperature of at least approximately 400°C, and preferably at a temperature ranging from approximately 700°C to 1500°C.

[0020] The biomass source is preferably cedar, pine, fir, cypress, hemlock, larch, spruce, birch, elm, eucalyptus, hickory, ebony, ironwood, maple, oak, poplar, or bamboo. Cedar wood is preferred, particularly because it is rich in lignin and has a low ash content.

[0021] The conductive properties and / or specific chemical properties of biochar can be modulated based on the heat treatment conditions and / or the nature of the biomass.

[0022] The bio-sourced carbon is preferably characterized by a hierarchical porosity comprising an internal microporosity and an intergranular macroporosity. The internal microporosity is specific to the bio-sourced carbon as such. It promotes a high adsorption capacity and optimized electrochemical exchanges. The intergranular macroporosity is specific to the structuring of the bio-sourced carbon within the first volume electrode (or constituting the first volume electrode). It allows the passage and efficient circulation of the fluid within the electrode. The internal microporosity is defined by micropores having an average diameter of less than 2 nm, preferably ranging from about 0.5 to 1.5 nm, and particularly preferably about 1 nm. The intergranular macroporosity depends on the size of the biochar granules and their arrangement in the first volume electrode.It is defined by macropores having an average diameter ranging from approximately 100 µm to 5 mm, and preferably ranging from approximately 500 µm to 1 mm.

[0023] Bio-sourced carbon preferably has a specific surface area ranging from 10 m 2 / g at 3500 m 2 / g approximately, particularly preferably ranging from 50 m 2 / g at 1500 m 2 / g approximately, and more particularly preferably ranging from 50 m 2 / g at 500 m 2 / g approximately. Such a specific surface area is beneficial for electrochemical applications, as it allows for better interaction between the liquid electrolyte and the first electrode, leading to improved performance. Pre-treatment or post-treatment can increase the specific surface area.

[0024] In the invention, the specific surface area and microporosity can be determined by the Brunauer-Emmet-Teller method (BET method), in particular using adsorption isotherms carried out with CO2.

[0025] Biosourced carbon, and in particular biochar, can be functionalized by chemical groups or elements such as oxygenated groups such as carboxyls, lactones, phenols, phosphate or polyphosphate groups, nitrogen groups such as amines, pyridines, pyrroles, pyridones, sulfate groups such as sulfoxides, sulfones, sulfonic acids, thiophenes, thioethers, metal composites or metal oxides, the metal being chosen from iron, manganese, magnesium, zinc, copper, cobalt, and a mixture thereof, in particular by activation or doping. This can improve its conductive properties and / or give it specific chemical properties.

[0026] The bio-sourced carbon preferably has an electrical resistivity of at most approximately 15,000 Ω.m, and particularly preferably ranging from 1x10 - 8 Ω.m to about 1 Ω.m.

[0027] In the invention, the resistivity is determined by the four-point probe technique.

[0028] The bio-sourced carbon is preferably in the form of particles such as granules, chips or pellets, particularly preferably particles such as granules, chips or pellets, with an average size ranging from 250 µm to 100 mm, and more particularly preferably with an average size ranging from 1 mm to 50 mm.

[0029] This form of granules, chips or pellets is advantageous for industrial applications, and in particular allows for a first flexible electrode to be obtained in terms of replacement and maintenance, and with a better contact surface. This also allows for a reactor with increased adaptability to implement different electrochemical processes.

[0030] In the invention, the average size of particles such as granules, chips, or pellets is determined by particle size analysis or by imaging techniques.

[0031] The first electrode can have a volume V1 (in cm 3 ), preferably 1 cm 3 at 1*10 6 cm 3 , and more particularly preferably with a volume of 5 cm 3 at 5000 cm 3 .

[0032] According to a preferred embodiment of the invention, the first electrode has a specific volume ranging from 0.1 to 10 cm 3 / g, preferably 2.5 to 5.0 cm 3 / g, and particularly preferably ranging from 3.0 to 4.5 cm 3 / g. Such a mass volume guarantees a good electrical connection within the bio-sourced carbon particles.

[0033] In the present invention, a volume electrode is an electrode whose active surface is distributed in a volume. Conversely, a surface electrode is defined by two orthogonal main dimensions, and is generally in the form of plates with a small thickness. An electrode is considered to be a plate when the ratio of the thickness with each of the two orthogonal main dimensions (thickness / length and thickness / width) of said electrode is less than 0.3, preferably less than 0.1. In other words, a volume electrode has at least three orthogonal main dimensions D1, D2 and D3 so that D3 / D1 < 0.3 and preferably D3 / D1 < 0.1 and D3 / D2 < 0.3 and preferably D3 / D2 < 0.1.

[0034] According to a preferred embodiment, the first volume electrode represents from 25 to 90% by volume approximately, and particularly preferably from 30 to 75% approximately, relative to the total volume of the reactor.

[0035] The second electrode

[0036] The second electrode is a surface or volume electrode comprising an electrically conductive material, and preferably consisting essentially of an electrically conductive material.

[0037] In the invention, the term "essentially consisting" means that the electrically conductive material represents at least approximately 90% by mass, preferably at least approximately 95% by mass, and particularly preferably approximately 100% by mass, relative to the total mass of the second surface or volume electrode.

[0038] The electrically conductive material may have an electrical resistivity of at most approximately 15,000 Ω.m, and particularly preferably ranging from 1x10 -8 Ω.m to about 1 Ω.m.

[0039] The electrically conductive material may be chosen from ferrous waste, iron, iron alloys such as steel, bio-sourced carbon, and one of their mixtures, preferably bio-sourced carbon or low-carbon steel (i.e. with at most 0.3% by mass of carbon, relative to the total mass of the steel).

[0040] Biosourced carbon is preferably biochar.

[0041] According to a particular embodiment of the invention, the biochar of the second electrode is obtained by heat treatment of one or more sources of biomass at a temperature of at least approximately 400°C, and preferably at a temperature ranging from approximately 700°C to 1500°C.

[0042] The biomass source is preferably cedar, pine, fir, cypress, hemlock, larch, spruce, birch, elm, eucalyptus, hickory, ebony, ironwood, maple, oak, poplar or bamboo.

[0043] The conductive properties and / or specific chemical properties of biochar can be modulated based on the heat treatment conditions and / or the nature of the biomass.

[0044] The bio-sourced carbon is preferably characterized by a hierarchical porosity comprising an internal microporosity and an intergranular macroporosity. The internal microporosity is specific to the bio-sourced carbon as such. It promotes a high adsorption capacity and optimized electrochemical exchanges. The intergranular macroporosity is specific to the structuring of the bio-sourced carbon within the second volume electrode (or constituting the second volume electrode). It allows the passage and efficient circulation of the fluid within the electrode. The internal microporosity is defined by micropores having an average diameter of less than 2 nm, preferably ranging from about 0.5 to 1.5 nm, and particularly preferably about 1 nm. The intergranular macroporosity depends on the size of the biochar granules and their arrangement in the volume electrode.It is defined by macropores having an average diameter ranging from approximately 100 µm to 5 mm, and preferably ranging from approximately 500 µm to 1 mm.

[0045] The bio-sourced carbon of the second electrode preferably has a specific surface area ranging from 10 m 2 / g at 3500 m 2 / g approximately, particularly preferably ranging from 50 m 2 / g at 1500 m 2 / g approximately, and more particularly preferably ranging from 50 m 2 / g at 500 m 2 / g approximately. Such a specific surface area is beneficial for electrochemical applications, as it allows for better interaction between the liquid electrolyte and the second electrode, leading to improved performance.

[0046] Biosourced carbon, and in particular biochar, can be functionalized by chemical groups or elements such as oxygenated groups such as carboxyls, lactones, phenols, phosphate or polyphosphate groups, nitrogen groups such as amines, pyridines, pyrroles, pyridones, sulfate groups such as sulfoxides, sulfones, sulfonic acids, thiophenes, thioethers, metal or metal oxide composites, the metal being chosen from iron, manganese, magnesium, zinc, copper, cobalt, and a mixture thereof, in particular by activation or doping. This can improve its conductive properties and / or give it specific chemical properties.

[0047] When the second electrode is a volume electrode, the second electrode preferably has a mass volume of electrically conductive material ranging from 0.1 to 10 cm 3 / g, and particularly preferably from 0.5 to 5 cm 3 / g.

[0048] When the second electrode is a volume electrode, it represents from 5% to 35% by volume approximately, and particularly preferably from 10 to 30% by volume, relative to the total volume of the reactor.

[0049] The total volume of the reactor (100%) is understood to be the volume of the first volume electrode, the second surface or volume electrode and the separator. When the second electrode is a surface electrode, its volume is negligible compared to the volumes of the first electrode and the separator.

[0050] When the second electrode is a volume electrode, the biosourced carbon is preferably in the form of particles such as granules, chips, or pellets, particularly preferably particles such as granules, chips, or pellets, with an average size ranging from 250 µm to 100 mm, and more particularly preferably with an average size ranging from 1 mm to 50 mm.

[0051] This form of granules, chips or pellets is advantageous for industrial applications, and in particular allows for a second electrode to be obtained that is flexible in terms of replacement and maintenance, and has a better contact surface. This also allows for a reactor with increased adaptability for implementing different electrochemical processes.

[0052] When the second electrode is a volume electrode, the iron or iron alloy is preferably in the form of a fibrous or woven material, such as wool (iron wool or steel wool).

[0053] When the second electrode is a surface electrode, the second electrode is preferably in the form of a plate, a cylinder, a prism, a sphere or a combination of these geometries.

[0054] The second electrode is preferably a volume electrode.

[0055] The second electrode can then have a volume V2 (in cm 3 ).

[0056] According to a preferred embodiment, the first and second electrodes are such that the volume ratio V1 / V2 ranges from about 1 to 100, and particularly preferably the volume ratio V1 / V2 ranges from about 1 to 50. When the volume ratio V1 / V2 is greater than 100, the corrosion current may be too high. When the volume ratio V1 / V2 is less than 1, the corrosion current may be too low.

[0057] Entrance and exit

[0058] The reactor comprises at least one first inlet and at least one first outlet, configured respectively to bring a liquid electrolyte in a continuous flow into the reactor, and to leave said liquid electrolyte in a continuous flow from the reactor.

[0059] Therefore, the liquid electrolyte circulates and moves within the reactor from the first inlet to the first outlet in a continuous flow.

[0060] Preferably, the electrolyte enters or is introduced into the reactor in a main flow direction DF0. Particularly preferably, the electrolyte enters or is introduced into the first and second electrodes in a direction parallel to the main flow direction DF0.

[0061] The reactor may further comprise at least one means configured to obtain a movement of the liquid electrolyte in continuous flow within said reactor with a flow rate ranging from 0.1 to 5*10 8 ml / min, and preferably ranging from 1 to 2.5*10 7 ml / min.

[0062] On a smaller scale, other flow rate ranges can be used such as a flow rate of 5 to 100 ml / min, and preferably 30 to 70 ml / min.

[0063] The medium may be a pump such as a peristaltic pump, syringe pump, propeller pump, positive displacement pump, centrifugal pump, or diaphragm pump.

[0064] The liquid electrolyte is preferably a medium poor in bacteria and / or nutrients.

[0065] The liquid electrolyte is preferably an aqueous electrolyte.

[0066] The separator comprises at least one dielectric portion in contact with said first and second electrodes.

[0067] In the invention, the expression "dielectric part" means an electrically insulating part, i.e. a part whose electrical conductivity can be at most 1.10 - 8 S / m (siemens per meter), preferably at most 1.10 - 9 S / m, and particularly preferably at most 1.10 - 10 S / m (siemens per meter), measured at 25°C in direct current.

[0068] The presence of this dielectric part makes it possible to avoid any current supply or leakage within the separator and coming from one or more electrodes. This dielectric part is in contact (i.e. in direct physical contact) with said first and second electrodes. In other words, the separator is in contact with said first and second electrodes by or via said dielectric part.

[0069] The dielectric portion of the separator preferably comprises at least one polymeric material, and particularly preferably consists essentially of a polymeric material.

[0070] In the invention, the term "polymer" includes homo- and copolymers.

[0071] In the invention, the term "essentially consisting" means that the polymer material represents at least approximately 90% by mass, preferably at least approximately 95% by mass, and particularly preferably approximately 100% by mass, relative to the total mass of the dielectric part.

[0072] The polymer material may be selected from polyamides, polycarbonates, polyetherimides, polyolefins (PP, PET, PBT), polystyrenes (PS, ABS), polyacrylates (PMA), polymethacrylates (PMMA), polyaryletherketones (PEEK), and a mixture thereof.

[0073] Polymethacrylates are preferred as a polymer material. This allows for better stability, better mechanical properties, and it is an easy-to-machine polymer material.

[0074] The metal material can be chosen from the following metals and metal alloys: titanium, copper, aluminum, iron, and stainless steel.

[0075] When the separator is made of polymer material, it can be manufactured by 3D printing using stereolithography.

[0076] Said separator is configured to separate the first and second electrodes. In other words, it is positioned within the reactor so as to separate the first and second electrodes. This thus makes it possible to avoid any physical contact between the electrodes and thus any risk of short circuit.

[0077] More particularly, the separator is interposed between the first and second electrodes.

[0078] The separator is also configured to provide compression on said first electrode. Compression involves a reduction or decrease in volume. In other words, the separator comprises at least one compression member or is arranged on either side of the first and second electrodes and / or sized so as to provide compression on said first electrode.

[0079] The first electrode being a volume electrode, the compression on it makes it possible to modulate its density or its mass volume, and thus to promote good electrical contact between the biosourced carbon particles within said first electrode; and also between the biosourced carbon particles and a current collector if one exists. The compression also ensures optimal contact between the first electrode and the current collector if one exists, thus reducing the contact resistance.

[0080] The separator is further preferably also configured to provide compression on said second electrode. The compression ensures in particular optimal contact between the second electrode and a current collector if one exists, thus reducing the contact resistance. Furthermore, when the second electrode is a volume electrode, the compression on it makes it possible to modulate its density or its mass volume, and thus to promote good electrical contact between the particles of electrically conductive material within said second electrode; and also between the particles of electrically conductive material and the current collector if one exists.

[0081] According to a preferred embodiment of the invention, a compressive force is applied by the separator to said first electrode and optionally to the second electrode, and preferably to said first and second electrodes respectively.

[0082] The compressive force may range from about 10 kPa to about 10000 kPa, preferably from about 50 kPa to about 5000 kPa, and particularly preferably from about 100 kPa to about 1000 kPa.

[0083] The separator is further preferably configured to control the volume ratio of the first and second volume electrodes, at constant reactor volume.

[0084] The dimensions of the separator are adjustable in length, width, diameter, thickness, depth, etc. This allows on the one hand to vary the distance between the electrodes (the separator separates the electrodes and a dielectric part of said separator is in contact with them), and on the other hand to vary the volume of each of the volume electrodes (the separator ensures compression on the volume electrodes).

[0085] According to a preferred embodiment of the invention, the separator comprises at least one empty or hollow volume or space between the first and second electrodes. This thus makes it possible to reduce charge losses. Furthermore, the liquid electrolyte can move within this empty or hollow volume or space.

[0086] Advantageously, the separator may be in the form of a piston, a spring, or a hollow element, such as a hollow cylinder. The hollow element (respectively the piston) may then be in contact (by its dielectric part) with the first and second electrodes by two ends positioned on either side of the hollow element (respectively the piston).

[0087] The separator is also configured to allow movement of the liquid electrolyte in a continuous flow from the first inlet to the first outlet.

[0088] Thus, the separator is configured to allow the liquid electrolyte to flow in a continuous flow within the reactor, and in particular from the first inlet to the first outlet. In particular, it allows the selective passage of the liquid electrolyte in a continuous flow within the reactor.

[0089] According to a preferred embodiment, the separator is a hollow element provided with at least one closing element, such as a cover, having one or more openings, such as a grid, to allow the continuous flow movement of the liquid electrolyte from the first electrode or the second electrode towards the first outlet.

[0090] The openings preferably have a size smaller than the average size of the particles of electrically conductive material of the second electrode and the particles of bio-sourced carbon of the first electrode. This makes it possible to prevent the passage of said particles, while allowing the passage of the liquid electrolyte within the separator.

[0091] The separator as a hollow element may comprise a first closure element and a second closure element, the first closure element being preferentially in contact with said first electrode and the second closure element being preferentially in contact with said second electrode. In this preferred embodiment, the first and second closure elements may be positioned on either side of the hollow element, at two ends of said separator, so that they are in contact with said first and second electrodes respectively.

[0092] The first and second closure members preferably have the same definition as the closure member described above.

[0093] According to a preferred embodiment of the invention, the separator is a rigid separator.

[0094] Due to the rigidity of the separator, this prevents the separator from deforming when compressed on the electrode(s).

[0095] Particularly preferably, the separator has a Young's modulus of at least 1.5 GPa, and more particularly preferably of at most 250 GPa.

[0096] In the invention, Young's modulus is determined by a test standardized by the American Society for Testing Materials (ASTM E111) which takes into account the strength and stress of a material to which a uniaxial force is applied incrementally or continuously.

[0097] The separator may be made of a polymer material as defined in the invention, including the dielectric part, or the separator may be made of a metallic material as defined in the invention, except for the dielectric part which is as defined in the invention.

[0098] The metallic material can have a Young's modulus ranging from about 100 to 200 GPa.

[0099] The polymer material can have a Young's modulus ranging from 2 to 5 GPa.

[0100] The separator, by its rigid and hollow design, allows a uniform distribution of pressure on said first and second electrodes, ensuring optimal electrical conductivity through the electrode materials. This central compression provided by the separator makes it possible to achieve a density of the particles forming the volume electrodes appropriate for obtaining good electrochemical performances of the reactor. The length of the separator is adapted to the V1 / V2 electrode volume ratio for a constant reactor volume, thus allowing a precise modulation of the electrochemical configuration without compromising the efficiency of the process. In addition, the design of the separator facilitates the application of sufficient compression on the volume electrodes, essential for maintaining optimal electrical resistivity and ensuring adequate conductivity within the reactor.

[0101] An expandable separator structure, with its ability to dynamically adjust the separator length in an application involving material loss from the volume electrodes, would ensure optimal compression and electrical conductivity of the electrodes.

[0102] According to a preferred embodiment, the separator represents at least approximately 10% by volume, particularly preferably approximately 10% to 70% by volume, and more particularly preferably approximately 25% to 65% by volume, relative to the total volume of the reactor. Unlike the devices of the prior art which tend to limit the thickness of the separator to make it as thin as possible, the separator of the reactor of the invention represents a large volume in the reactor in order in particular to ensure compression on the volume electrodes.

[0103] Preferably, the first electrode / separator volume ratio ranges from 0.35 to 8, and particularly preferably from 0.6 to 4.5.

[0104] The closing and opening elements integrated into the separator allow the application of a uniform radial force on all the volume electrodes. This feature ensures a constant density of the electrode materials throughout the reactor, contributing to the uniformity of the electrochemical reaction. The amount of electrode material used is calculated to fill the space delimited by the separator, taking into account the compression necessary to achieve and maintain the desired electrical conductivity.

[0105] The reactor may further comprise at least one first current collector, preferably in contact with the first electrode.

[0106] In particular, the first electrode is interposed between the first collector and the separator.

[0107] The first collector can be made of copper, silver, steel, nickel, titanium, graphite, or any other corrosion-resistant conductive material.

[0108] The reactor may further comprise at least one second current collector, preferably in contact with the second electrode.

[0109] In particular, the second electrode is interposed between the second collector and the separator.

[0110] The first current collector (respectively the second current collector) is configured to provide compression on the first volume electrode (respectively on the second surface or volume electrode).

[0111] The liquid electrolyte can move in a continuous flow within the reactor according to one or other of the following alternatives: - the liquid electrolyte can move in a continuous flow from the first inlet to the first outlet in a direction D F(parallel to the main flow direction D F0 ), passing successively in this order possibly the second current collector if it exists, the second electrode, the separator, the first electrode, and possibly the first current collector if it exists, or- (a) a first liquid electrolyte can move in continuous flow from the first inlet to the first outlet: in a direction D F1 (parallel to the main flow direction D F0 ), then a direction D F1’ perpendicular to direction D F1 (ie perpendicular to the main flow direction D F0 ) by successively crossing in this order possibly the second current collector if it exists, the second electrode and a first compartment of the separator, and- (b) a second liquid electrolyte can move in continuous flow from a second inlet to a second outlet: in a direction D F2(parallel to the main flow direction D F0 ), then a direction D F2’ perpendicular to direction D F2 (ie perpendicular to the main flow direction D F0 ) by successively crossing in this order possibly the first current collector if it exists, the first electrode and a second compartment of the separator.

[0112] The implementation of one or other of the above alternatives will depend on the electrochemical reaction to be implemented which will itself condition the structure of the separator to be used (presence of one or more membranes, one or more flows, etc. requiring the presence of one or more compartments within the separator).

[0113] In the second alternative, the reactor further comprises a second inlet and a second outlet. The liquid electrolyte comprises a first liquid electrolyte and a second liquid electrolyte. The separator comprises a first compartment and a second compartment.

[0114] Other alternatives are possible (other inlets and / or outlets, other compartments, other flows, etc.) depending on the electrochemical reaction to be implemented.

[0115] According to a preferred embodiment, no electrode delimits a cavity inside which another electrode extends and particularly preferably, the electrodes are not concentric.

[0116] The separator can be single-compartment or single-block, or multi-compartment or multi-block.

[0117] According to a first variant, the separator is single-compartment or single-block.

[0118] According to this first variant, the liquid electrolyte can enter the reactor through the first inlet in a direction D F (parallel to the main flow direction D F0 ), said first inlet being positioned upstream of (i.e. before) the second electrode (even more preferably upstream of the second current collector if it exists) and the liquid electrolyte can exit the reactor through the first outlet in the direction D F , said first outlet being positioned downstream of (i.e. after) the first electrode (even more preferably downstream of the first current collector if it exists). In this embodiment, the liquid electrolyte can then move in a continuous flow from the first inlet to the first outlet in the direction D F (parallel to the main flow direction D F0), passing successively in this order possibly the second current collector if it exists, the second electrode, the separator, the first electrode, and possibly the first current collector if it exists.

[0119] According to this first variant, the reactor may be: - a reactor for implementing a galvano-fenton process, and the electrically conductive material of the second electrode is chosen from iron, ferrous waste and iron alloys; or - a reactor for implementing electrochlorination, and the electrically conductive material of the second electrode is a biosourced carbon; or - a supercapacitor, and the electrically conductive material of the second electrode is a biosourced carbon.

[0120] According to a second variant, the separator is multi-compartmental or multi-block.

[0121] According to this second variant, a first liquid electrolyte can enter the reactor through the first inlet in a direction D F1 (parallel to the main flow direction D F0 ), said first inlet being positioned upstream of (i.e. before) the second electrode (even more preferably upstream of the second current collector if it exists) and the first liquid electrolyte can exit the reactor through the first outlet in a direction D F1’ perpendicular to direction D F1 , said first outlet being positioned downstream of (i.e. after) the second electrode, perpendicular to the first inlet and at the level of a first compartment of the separator.

[0122] In this embodiment, the first liquid electrolyte can then move in a continuous flow from the first inlet to the first outlet in a direction D F 1, then a direction D F1’by successively crossing in this order possibly the second current collector if it exists, the second electrode and the first compartment of the separator.

[0123] According to this embodiment of the second variant, the reactor may further comprise a second inlet and a second outlet so that a second liquid electrolyte may enter the reactor via the second inlet in a direction D F2 (parallel to the main flow direction D F0 ), said second inlet being positioned upstream of (i.e. before) the first electrode (even more preferably upstream of the first current collector if it exists) and the second liquid electrolyte can exit the reactor through the second outlet in a direction D F2’ perpendicular to direction D F2, said second outlet being positioned downstream of (i.e. after) the first electrode, perpendicular to the second inlet and at the level of a second compartment of the separator.

[0124] In this embodiment, the second liquid electrolyte can then move in a continuous flow from the second inlet to the second outlet in a direction D F2 , then a direction D F2’ by successively crossing in this order possibly the first current collector if it exists, the first electrode and the second compartment of the separator.

[0125] The first and second compartments are preferably separated by an ion exchange membrane. This ensures ionic continuity within the reactor.

[0126] According to this embodiment of the second variant, the reactor may be: - a reactor for carrying out water electrolysis, and the electrically conductive material of the second electrode is a bio-sourced carbon; or - a redox flow battery, and the electrically conductive material of the second electrode is a bio-sourced carbon.

[0127] The separator may further comprise a third compartment interposed between the first and second compartments such that the first and third compartments are preferably separated by an ion exchange membrane such as a cation membrane, and the second and third compartments are preferably separated by an ion exchange membrane such as an anion membrane.

[0128] In this embodiment, the reaction preferably further comprises a third inlet and a third outlet, so that a third liquid electrolyte can enter the reactor through the third inlet in a direction D F 3(perpendicular to the main flow direction D F0 ), said third inlet being positioned at the level of the third compartment of the separator, and the third liquid electrolyte can exit the reactor through the third outlet in direction D F 3, said third outlet being positioned at the level of the third compartment of the separator.

[0129] In this embodiment, the third liquid electrolyte can then move in a continuous flow from the third inlet to the third outlet in a direction D F 3 by crossing the third compartment of the separator.

[0130] According to this embodiment of the second variant, the reactor can be: - a reactor for carrying out desalination of sea water, and the electrically conductive material of the second electrode is a bio-sourced carbon; or - for the production of electrical energy from osmotic energy (the difference in salinity between fresh water (rivers) and salt water (sea water), and the electrically conductive material of the second electrode is a bio-sourced carbon.

[0131] The liquid electrolyte is preferably a medium poor in bacteria and / or nutrients.

[0132] The second object of the invention is the use of an electrochemical reactor in accordance with the first object of the invention, for depolluting a liquid medium comprising at least one organic pollutant, for disinfecting water by electrochlorination, for implementing water electrolysis, for implementing seawater desalination, for energy storage (e.g. as a redox flow battery or supercapacitor), or for the production of electrical energy from osmotic energy (the difference in salinity between fresh water (rivers) and salt water (seawater)).

[0133] The reactor according to the first object is modular in that it is possible to modify the first electrode (electrically conductive material) and the second electrode (electrically conductive material, surface or volume electrode, etc.), the shape and structure of the separator, as well as the number of inlets and outlets. Its configuration is therefore versatile and allows it to be used in a large number of applications.

[0134] Electrochlorination

[0135] The reactor can be used to disinfect water through electrochlorination, which involves producing chlorine and other chemical derivatives from saline solutions.

[0136] Electrochlorination is frequently used to disinfect water, whether for drinking water, swimming pools, or industrial cooling systems.

[0137] Chlorine produced by electrochlorination can also kill a variety of harmful microorganisms.

[0138] According to this embodiment, the electrically conductive material of the first electrode is preferably a bio-sourced carbon as defined in the invention, the electrically conductive material of the second electrode is preferably a bio-sourced carbon as defined in the invention, and the second electrode is preferably a volume electrode.

[0139] Electrolysis of water

[0140] The reactor can be used to implement water electrolysis.

[0141] In the energy sector, this reactor configuration can facilitate the electrochemical production of decarbonized dihydrogen by the electrolysis of water.

[0142] According to this embodiment, the electrically conductive material of the first electrode is preferably a bio-sourced carbon as defined in the invention, the electrically conductive material of the second electrode is preferably a bio-sourced carbon as defined in the invention, and particularly preferably a bio-sourced carbon functionalized with at least one metal or metal oxide (acting as a catalyst), said metal being able to be chosen from iron, manganese, magnesium, calcium, zinc, copper, and cobalt. This can then make it possible to optimize the electrolysis process for maximum electrochemical performance.

[0143] The second electrode is preferably a volume electrode.

[0144] Energy storage

[0145] The reactor can be used for energy storage (e.g. as a redox flow battery or supercapacitor).

[0146] According to this embodiment, the electrically conductive material of the first electrode is preferably a bio-sourced carbon as defined in the invention, the electrically conductive material of the second electrode is preferably a bio-sourced carbon as defined in the invention, and the second electrode is preferably a volume electrode.

[0147] The reactor can be used in particular as a redox flow battery. The use of large surface area bio-based carbon-based volume electrodes improves electrochemical performance by increasing the rate of redox reactions, resulting in higher energy density. The separator, in turn, controls electrical contact in the reactor and can improve overall efficiency.

[0148] The reactor can in particular be used as a supercapacitor.

[0149] This energy storage device relies on the accumulation of ions in a liquid electrolyte during the charging phase, creating a double electrical layer on the surface of the electrodes. This double electrical layer stores energy. The use of volume electrodes based on bio-sourced carbon with a large specific surface area improves electrochemical performance and effectively replaces the activated carbon traditionally used.

[0150] Desalination of seawater

[0151] The reactor can be used to implement seawater desalination, particularly as an electrodialysis cell. Salt ions in the seawater are attracted to the charged electrodes, removing them from the water and making it potable at the separator.

[0152] Seawater desalination is a process designed to remove anions and cations from seawater. In particular, electrical energy is injected to force the migration of anions and cations towards the electrodes.

[0153] According to this embodiment, the electrically conductive material of the first electrode is preferably a bio-sourced carbon as defined in the invention, the electrically conductive material of the second electrode is preferably a bio-sourced carbon as defined in the invention, and the second electrode is preferably a volume electrode.

[0154] The use of volume electrodes based on bio-sourced carbon with a large specific surface area makes it possible to increase the efficiency of electrodialysis.

[0155] In addition, the reactor operating in continuous flow can make the electrodialysis process more efficient and adaptable to different scales, from small portable installations to large industrial plants.

[0156] Energy production

[0157] The reactor can be used for the production of electrical energy from osmotic energy.

[0158] The production of electrical energy from osmotic energy is based on the spontaneous migration of ions between seawater and freshwater to create an ionic current that can be converted into electrical current using electrodes and membranes.

[0159] This makes it possible to produce electrical energy thanks to the difference in salinity between fresh water (rivers) and salt water (sea water).

[0160] According to this embodiment, the electrically conductive material of the first electrode is preferably a bio-sourced carbon as defined in the invention, the electrically conductive material of the second electrode is preferably a bio-sourced carbon as defined in the invention, and the second electrode is preferably a volume electrode.

[0161] Use of the reactor in an electro-fenton process

[0162] The reactor of the invention can be used to implement an electro-Fenton process. In state-of-the-art processes, the first electrode is a copper electrode and the second electrode is an iron electrode. However, the implementation of copper as an electrode material in the process has several drawbacks: copper ions can be released into the effluent to be treated, which can lead to secondary contamination and adverse effects on human health and the environment; the extraction, processing and manufacturing of copper generate significant economic costs and environmental impacts; and copper mining requires significant energy inputs, which increases production costs and contributes to greenhouse gas emissions. The reactor of the invention provides an alternative abundant and bio-sourced first electrode material, while ensuring good electrochemical performance.

[0163] The use of the reactor to decontaminate a liquid medium comprising at least one organic pollutant is preferred.

[0164] The third subject of the invention is a method for decontaminating a liquid medium comprising at least one organic pollutant, preferably chosen from industrial effluents, wastewater, used oil emulsions, and oil-laden wastewater emulsions, comprising at least one organic pollutant, characterized in that:- said method comprises at least one step of degrading said organic pollutant in an oxidizing medium generated by the use of an electrochemical reactor in accordance with the first subject of the invention, and in which:- the liquid electrolyte comprises said liquid medium and at least one oxidizing agent, and- the electrically conductive material of the first electrode is a biosourced carbon, and the electrically conductive material of the second electrode is chosen from iron, ferrous waste and iron alloys.

[0165] Wastewater reuse is a political and socio-economic issue for the development of a sustainable city. This development requires the reduction of micropolluting substances (pesticides, endocrine disruptors, plasticizers, antibiotics, etc.) present in treated water leaving wastewater treatment plants. In this context, micropollutant treatment processes, such as advanced oxidation processes (AOPs), have been booming in recent years. These processes have not yet been selected as a complementary treatment solution in wastewater treatment plants due to their high additional cost and significant energy consumption. Thanks to the use of the reactor of the invention in Galvano-Fenton (GF) technology, wastewater can be treated by degrading micropollutants while producing electrical energy.This process is based on the use of inexpensive electrodes based on iron and bio-sourced carbon in the presence of an oxidizing agent (eg H2O2) to catalyze the Fenton reaction and generate OH radicals. . capable of degrading recalcitrant pollutants in wastewater. Biochar is a by-product of the thermal decomposition of residual biomass that is generally produced from locally available biological waste, such as agricultural and forestry residues, at very low costs. The designed reactor thus promotes the circular bioeconomy, by combining the degradation of micropollutants, energy production and the recovery of biomass waste in a sustainable manner and with a low ecological footprint.

[0166] The organic pollutant may be selected from plasticizers (such as bisphenols), herbicides (such as atrazine), pesticides (such as Alachlor: 2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide), endocrine disruptors (such as ethinylestradiol), pharmaceuticals (such as paracetamol, carbamazepine), per- and polyfluoroalkyls (also known by the acronym "PFAS"), fungicides (such as Chlorothalonil: 2-(aminocarbonyl)-3,5,6-trichloro-4-cyanobenzenesulfonic acid), their metabolites (fungicides), and a mixture thereof.

[0167] The oxidizing agent can be hydrogen peroxide or sodium percarbonate. Sodium percarbonate has the advantage of being easy to transport and / or store and non-toxic.

[0168] According to a preferred embodiment, the liquid electrolyte has a pH ranging from about 1 to 14, and particularly preferably from about 1 to 5.

[0169] According to a preferred embodiment, the liquid electrolyte comprises 1x10 -6 at approximately 1000 ppm of organic pollutant(s), and particularly preferably 1x10 -1 at approximately 100 ppm of organic pollutant(s).

[0170] According to a preferred embodiment, the liquid electrolyte comprises 1x10 -3 at approximately 100 mM of hydrogen peroxide, and particularly preferably 1x10 -1 at about 10 mM hydrogen peroxide, as an oxidizing agent.

[0171] According to a preferred embodiment, the liquid electrolyte has an electrical conductivity ranging from 1x10 -5 at approximately 60 mS / cm, and particularly preferably from approximately 0.001 to 50 mS / cm.

[0172] Preferably, the degradation step is carried out at a temperature ranging from approximately 0 to 50°C.

[0173] According to a preferred embodiment, the first and second electrodes are such that the volume ratio V1 / V2 ranges from approximately 1 to 10, and particularly preferably the volume ratio V1 / V2 ranges from approximately 1 to 5. This makes it possible to guarantee better pollution control performance.

[0174] The invention is illustrated by the following figures and examples, to which it is however not limited. Shows two schematic representations and a photograph of the electrochemical reactor according to the invention. Shows a schematic representation of the electrochemical reactor according to the invention in the pseudo-steady state. Shows a schematic representation of the electrochemical reactor according to the invention in the semi-continuous state. Shows a schematic representation of the batch configuration of a reactor of the prior art, a schematic representation of the continuous flow configuration of a reactor according to the invention, and curves of percentage discoloration as a function of time for both configurations. Shows the power curves for both configurations: batch of a reactor of the prior art and continuous flow of a reactor according to the invention.La shows a schematic representation of a reactor according to the invention operating in a closed operating mode with total recirculation for the decontamination of solutions comprising micropollutants.La shows the ratio of the concentration of the micropollutant solution at time t to the concentration of the micropollutant solution initially as a function of time when the micropollutant is atrazine (ATZ), alachlor (ALA), bisphenol A (BPA), and ethinylestradiol (EE2).La shows the concentration of the micropollutant solution (in µg / L) at time t as a function of time when the micropollutant is perfluorooctanoic acid (PFOA).La shows the concentration of the micropollutant solution at time t as a function of time when the micropollutant is the metabolite of Chlorotalonil “R471811”.La shows the configuration of a reactor according to the invention for electrochlorination and in as a supercapacitor.Shows the configuration of a reactor according to the invention for the electrolysis of water and as a redox flow battery. Shows the configuration of a reactor according to the invention for the desalination of seawater, or for the production of electrical energy from osmotic energy. Examples

[0175] The raw materials used in the examples are listed below:- aqueous hydrogen peroxide solution (35% by weight aqueous solution), Sigma Aldrich,- dichloromethane (≥99.5% purity), Sigma Aldrich,- sodium hydroxide (≥98.0% purity in pellet form), Sigma Aldrich,- sulfuric acid (95.0-98.0% purity), Sigma Aldrich,- potassium chloride (≥99.0% purity), Sigma Aldrich,- potassium ferricyanide (III) (≥98.5% purity, K3Fe(CN)6), Sigma Aldrich,- malachite green (VM) oxalate (≥90.0% purity), Sigma Aldrich,- atrazine (ATZ) (≥98.0% purity), Sigma Aldrich,- alachlor (ALA) (≥98.0% purity), Sigma Aldrich,- ethinylestradiol (EE2), Sigma Aldrich,- bisphenol A (BPA) (≥99.0% purity), Sigma Aldrich,- perfluorooctanoic acid (PFOA) (95.0% purity), Sigma Aldrich,- chlorotalonil “R471811” (≥99.6% purity), ASCA GmbH.

[0176] The iron plate (surface of 6 cm 2, 9 grams of iron) is marketed by GoodFellow.

[0177] Steel wool (carbon content >0.3% by mass) is marketed by RS Components.

[0178] Copper collectors are sold by RS Components.

[0179] The photopolymerizable stereolithographic resin "Clear V4" is marketed by Makershop. It consists of a methacrylate oligomer, a methacrylate monomer, and <1% diphenyl (2,4,6 trimethylbenzoyl) phosphine oxide (TMDPO) as a photoinitiator. The cedar wood is marketed by a steel mill.

[0180] All solutions were prepared with deionized water (18 MΩ).

[0181] Unless otherwise stated, all materials were used as received from the manufacturers, without purification.

[0182] Specific surface area measurements

[0183] The specific surface area was measured using the Brunauer-Emmet-Teller (BET) model. To do this, a biochar sample was placed in a hermetic cell, where liquid nitrogen was used to cool the system to a cryogenic temperature allowing the adsorption of the selected gas (CO2) under vacuum, at different stages of constant pressure. The analysis was carried out using an automatic surface area and porosity analyzer sold under the trade name “Micro 100” by 3P instruments.

[0184] Measurement of electrical resistivity

[0185] To characterize the electrical resistivity of biochar, a biochar sample (dimensions approximately 40 mm x 10 mm x 0.5-1.5 mm) was polished with 2000 grit sandpaper until a smooth surface was obtained. The measurement was performed with a 4-point tungsten carbide probe, each point having a radius of 125 µm with a spacing of 1.27 mm between them. The system was mounted on a stand sold under the trade name “S-302” by Signatone connected to a source meter sold under the trade name “Keithley 2450”. Based on this measurement setup, the resistivity calculation must take into account the finite thickness of the sample. For this purpose, an equation that considers the resistivity of a two-dimensional sheet was corrected with a thickness factor (also considered isotropic) as shown in the following equation (1): in which:- represents the ideal resistance of an infinite two-dimensional sheet where R simply corresponds to the resistance measured between two probes (R=V / I),- t represents the thickness of the sample, and- F1 corresponds to a correction factor which takes into account the ratio t / s, s being the distance between the tips of the probes.

[0186] This correction factor is dimensionless and becomes negligible when the thickness is significantly less than the distance from the probe tips (if t< .

[0187] Measurement of the mass volume of the biochar volume electrode

[0188] ​This measurement was made on biochar granules. They were carried out under the application of a compressive force on the granules in order to obtain a density guaranteeing adequate electrical conductivity between the granules themselves as well as between the granules and the current collector. The experimental device comprises a piston and an empty, graduated translucent cylinder allowing the compression of the biochar granules. Copper current collectors placed at the end of the piston and at the base of the cylinder facilitate electrical resistance measurements and allow the analysis of the variation of the latter as a function of the density (the mass volume) of the granules, induced by compression. A quantity of 1 g of biochar granules was introduced into the cylinder. Without compression, the mass of biochar occupies an initial volume determined by the graduation of the cylinder, establishing an initial mass volume.The biochar pellets are then compressed using the piston. An ohmmeter is used to measure the resistance between the two current collectors during compression. This compression results in a reduction in volume and a decrease in electrical resistance. Compression is stopped when the electrical resistance value stops decreasing. The volume of the biochar pellets for this compression state is recorded using the cylinder's graduations to determine the corresponding specific volume. The results indicate that the electrical resistance has a minimum value of 4.86 ohms for a maximum specific volume of 3.87 cm. 3 .g -1 .

[0189] Measurement of the mass volume of the steel wool volume electrode

[0190] This measurement was made as previously described for the biochar volume electrode. The results indicate a maximum specific volume of 2.24 cm 3 .g-1 .

[0191] Monitoring the degradation of malachite green (MG)

[0192] The VM concentration during the duration of the experiments was obtained by absorbance measurements of the medium at a wavelength of 618 nm using a spectrophotometer sold under the trade name "Hach-Lange DR 3900". Through the use of a calibration curve for the absorbance values ​​obtained at λ max = 618 nm for different solutions of known VM concentration, the VM concentration was determined at different times of the reaction, allowing the degradation of the compound to be followed. The percentage of decolorization was calculated using the following equation (3): where Co represents the initial concentration of VM and Ct represents its concentration at a given time t(min).

[0193] Example 1: Preparation of biochar

[0194] In this example 1, the cedar wood received was mechanically cut into pieces measuring 70 mm x 20 mm x 3 mm. They were washed with deionized water while stirring for 20 minutes, then subjected to a drying step at 70°C for approximately 24 hours. Then, a pyrolysis heat treatment was carried out in a furnace sold under the trade name “RSH 50 / 500 / 13” by Nabertherm. The furnace was first placed under vacuum (e.g. using a vane pump) then under a nitrogen atmosphere at a flow rate of 100 Lh -1(maintained with a controller sold under the trade name “B 410” from Nabertherm). The heat treatment included heating from room temperature to a pyrolysis temperature of 900°C, with a heating ramp of 5°C per minute, maintaining the pyrolysis temperature for 2 hours, and then cooling to room temperature. The parts were recovered from the furnace, cleaned with isopropanol and deionized water before being stored in an airtight container.

[0195] Biochar in the form of a plate (surface electrode)

[0196] The parts obtained directly from the above process are in the form of plates measuring 37 mm x 13 mm x 2 mm.

[0197] Table 1 below illustrates the properties of the formed biochar:

[0198] Biochar in the form of granules (volume electrode)

[0199] The resulting biochar pieces were mechanically cut using a cutter to form hexahedral biochar pellets measuring 3 mm x 3 mm x 2 mm. Biochar pellets can also be obtained by pre-cutting the cedar wood pieces into aggregates before heat treatment. A shrinkage factor of approximately 1.3 in the dimensions of the aggregates after heat treatment should be taken into account for cedar wood.

[0200] Example 2: manufacturing the electrochemical reactor (first variant)

[0201] A reactor was designed using computer-aided design (CAD) software sold under the trade name “3D Fusion 360”, and the manufacturing of its various components was carried out by SLA 3D printing with a printer marketed under the reference “Form 2” by Formlabs. The printed components were cleaned and exposed to UV radiation. All components are made of polymethacrylate polymer material. The manufactured components are a main cylinder serving as a body and container, completed by a hollow cylindrical element functioning as an electrode separator and equipped with grids at the ends for the circulation of liquids while ensuring the retention and compression of the biochar granules.Cap-shaped covers equipped with a copper current collector serve as pistons to compress the electrodes at the ends of the reactor, thus facilitating current recovery and connection to the external circuit, as well as the supply and discharge of the solution to be treated. Shows two schematic representations (Figures 1 a and 1 b) and a photo (c) of the electrochemical reactor according to the invention, applied to the Galvano-Fenton process for the decontamination of effluents comprising organic pollutants.

[0202] The reactor1 as manufactured comprises a first volume electrode of biochar granules2, a second volume electrode of steel wool3 electrically connected to the first volume electrode of biochar granules2, at least one first inlet4 and at least one first outlet5, configured respectively to bring a liquid electrolyte in a continuous flow into the reactor, and to leave said liquid electrolyte in a continuous flow from the reactor in the same direction D F (parallel to the main flow direction D F0), and at least one separator6 in the form of a hollow cylinder provided with grids at each of its ends. The separator6 is made of dielectric material, it is in contact with said first and second electrodes (2, 3), it separates the first and second electrodes, it provides compression on the first and second electrodes, and it allows movement of the liquid electrolyte in a continuous flow from the first inlet4 to the first outlet5.

[0203] The reactor further comprises a piston cover containing a first copper current collector7 in contact with the first volume electrode2 and a piston cover containing a second copper current collector8 in contact with the second volume electrode3. The separator is a hollow cylinder with a length of 11 cm and a diameter of 13 mm. The hollow cylinder is provided at each end with a closing element comprising 2x1 mm openings spaced 0.5 mm apart such as a grid9. The liquid electrolyte flow D F is represented on the by a vertical arrow.

[0204] The final dimensions of the reactor are shown in Table 2 below:

[0205] Example 3: Use of the electrochemical reactor for the decontamination of a model solution comprising malachite green

[0206] The reactor of the invention was used to implement the degradation of a model organic pollutant, malachite green (MG) with a flow rate of 10 mL.min -1 and a biochar / steel wool volume ratio of 5.03. The reactor was fed concomitantly at room temperature (25°C) with an aqueous solution of VM and an aqueous solution of hydrogen peroxide, to form a liquid electrolyte having a pH 3 and comprising 10 ppm of VM (CO concentration) and 3 mM of hydrogen peroxide. The concentration of VM in the liquid electrolyte was evaluated at the reactor outlet for each condition, considering a pseudo-steady state of the operation. The configuration used in this first part of Example 3 is represented in the. A degradation rate of 92% was obtained.

[0207] A complementary analysis was performed during the parametric study, where a semi-continuous configuration was used in order to estimate the number of reactors in series required to achieve complete degradation of the model organic pollutant. In this configuration, 50 mL of a 10 ppm VM solution (solution to be treated with concentration C0) was treated in several steps or "passes" (named: τ, 2τ, 3τ, Nτ, etc...) through the reactor with a constant supply of an aqueous solution comprising 3 mM hydrogen peroxide at pH 3, at 25°C, where each of these "passes" in the reactor would represent a reactor in a series configuration. At the end of each "pass" in the reactor, the VM concentration as well as the toxicity of the treated solution were evaluated. A flow rate of 50 mL.min -1and a biochar electrode / steel wool electrode volume ratio of 2.78 were used. The configuration used in this second part of Example 3 is shown in the.

[0208] A degradation rate of 93% was obtained.

[0209] Comparative Example 4: Use of a prior art batch electrochemical reactor for the decontamination of a model solution comprising malachite green

[0210] To do this, a batch configuration reactor (pyrex glass beaker marketed by Labbox equipped with a magnetic stirrer ensuring the mixing of the reagents) comprising 100 mL of a 10 ppm VM solution, a surface electrode in the form of a biochar plate as prepared in Example 1, and a surface electrode in the form of a commercial iron plate was designed. The current collector for each biochar and iron plate was made using a stainless steel wire (marketed under the reference "316L" by Goodfellow). The solution further comprises hydrogen peroxide having an initial concentration of 3 mM, it is at 25°C and has an initial pH of 3. The biochar electrode / iron electrode surface ratio is 3.

[0211] Shows a schematic representation of the batch configuration with surface electrodes of biochar and iron (a), of the configuration of the invention, i.e. continuous flow reaction with volume electrodes of biochar and steel wool (LA) (b), and a curve of the percentage of discoloration as a function of time for the batch configuration (curve a),c) and for the configuration of the invention (curve b),c).

[0212] It is observed that in the batch configuration, it takes 5 minutes to treat 100 mL of water to achieve 70% decolorization and more than 10 minutes to achieve 95% decolorization. On the contrary, with the reactor according to the invention (conditions of example 3, second part: flow rate of 50 mL.min -1 and a biochar / steel wool volume ratio of 2.78), it takes only 2 minutes to process the same amount of solution to 93% decolorization.

[0213] The reactor according to the invention presents a more advantageous performance compared to the batch configuration: thanks to the use of volume electrodes, better degradation kinetics are observed, with an initial degradation rate of 700 µmol.L -1 .min -1 , which is 50 times higher than that obtained in batch configuration (14 µmol.L -1 .min -1 ). This better kinetics of VM degradation allows a faster reduction in the toxicity of the treated solution.

[0214] In addition, an electrochemical characterization was carried out to compare the energy production performances of the Galvano-Fenton process in the two configurations: batch (not in accordance with the invention) and reactor (in accordance with the invention). The use of linear voltammetry allowed the characterization of the two configurations in order to obtain the power curves presented on the. It is observed that the power density expressed by the two configurations are similar.

[0215] Example 5: Use of the electrochemical reactor for the decontamination of model solutions containing other types of organic pollutants

[0216] The reactor according to the invention was used in the degradation of four micropollutants of different chemical natures by the Galvano-Fenton process. The conditions chosen correspond to a biochar electrode / steel wool electrode volume ratio of 2.78 and a flow rate of 50 mL.min-1 The solution to be treated further comprises an initial concentration of 1 ppm of each micropollutant, hydrogen peroxide having an initial concentration of 3 mM, it is at 25°C and has an initial pH of 3. Shows a schematic representation of the closed operating mode with total recirculation.

[0217] Shows the ratio of the concentration of the micropollutant solution at time t (concentration C) to the concentration of the micropollutant solution initially (at t = 0) (concentration C0), as a function of time when the micropollutant is atrazine (ATZ) (a); alachlor (ALA) (b), bisphenol A (BPA) (c), and ethinylestradiol (EE2) (d).

[0218] It can be observed, mainly for the most recalcitrant pollutants (ATZ and ALA), a degradation kinetics reaching a degradation of 80% and 96% after 20 minutes of treatment, and for the micropollutants easiest to degrade (BPA and EE2), a very rapid and practically complete degradation kinetics.

[0219] Example 6: Use of the electrochemical reactor for the decontamination of model solutions containing PFAS

[0220] The reactor according to the invention was used in the degradation of perfluorooctanoic acid (PFOA) by the Galvano-Fenton process. The conditions chosen are those of Example 5, namely a biochar electrode / steel wool electrode volume ratio of 2.78 and a flow rate of 50 mL.min -1. The solution to be treated further comprises an initial concentration of 578 µg / L or 4.92 µg / L of PFOA, hydrogen peroxide having an initial concentration of 3 mM, it is at 25°C and has an initial pH of 3. A schematic representation of the closed operating mode with total recirculation is shown. For treatments beyond 20 minutes, the solution to be treated was enriched with hydrogen peroxide with a concentrated solution to reach further concentrations of 3 mM, this every 20 minutes.

[0221] Shows the concentration of micropollutant in the solution (in µg / L) at time t as a function of time when the micropollutant is perfluorooctanoic acid (PFOA) (Figures 8 a and 8 b).

[0222] A decrease in the presence of PFOA can be observed over the treatment time for both initial concentrations, with a degradation of 87% after 20 minutes and a degradation of 96% after 60 minutes of treatment for the highest initial concentration (a), and with a degradation of 86% after 20 minutes and a degradation of 96% after 60 minutes of treatment for the lowest initial concentration (b).

[0223] Example 7: Use of the electrochemical reactor for the decontamination of model solutions comprising metabolites of certain pesticides

[0224] The reactor according to the invention was used in the degradation of the reference Chlorotalonil metabolite “R471811” by the Galvano-Fenton process. The conditions chosen are those of Example 3, second part, namely a biochar electrode / steel wool electrode volume ratio of 2.78 and a flow rate of 50 mL.min -1. The solution to be treated further comprises an initial concentration of 511 µg / L or 4.89 µg / L of the Chlorotalonil metabolite "R471811", hydrogen peroxide having an initial concentration of 3 mM, it is at 25°C and has an initial pH of 3. A schematic representation of the closed operating mode with total recirculation is shown. For treatments beyond 20 minutes, the solution to be treated was enriched with hydrogen peroxide with a concentrated solution to reach further concentrations of 3 mM, this every 20 minutes.

[0225] Shows the concentration of the micropollutant solution at time t as a function of time when the micropollutant is the metabolite of Chlorotalonil “R471811” (Figures 9 a and 9 b).

[0226] A decrease in the presence of the Chlorotalonil metabolite “R471811” can be observed over the treatment time for both initial concentrations, with a degradation of 83% after 20 minutes and a degradation of 89% after 60 minutes of treatment for the highest initial concentration (a), and with a degradation of 87% after 20 minutes and a degradation of 94% after 60 minutes of treatment for the lowest initial concentration (b).

[0227] Example 8: design of the reactor in accordance with the invention for applications other than the decontamination of effluents containing organic pollutants

[0228] According to a first variant as defined in the invention (monobloc or mono-compartmental separator), the reactor is used for electrochlorination or as a supercapacitor and the electrically conductive material of the second electrode is a biosourced carbon. The shows the configuration of the reactor for electrochlorination (a) and as a supercapacitor (b).

[0229] More specifically, the liquid electrolyte enters the reactor10 through the first inlet40 in a direction D F (parallel to the main flow direction D F0 ), said first inlet 40 being positioned upstream of (i.e. before) the second current collector 80 and the liquid electrolyte leaves the reactor 10 through the first outlet 50 in the direction D F, said first outlet50 being positioned downstream of (i.e. after) the first current collector70. The liquid electrolyte then moves in a continuous flow from the first inlet40 to the first outlet50 in the direction D F , successively passing in this order through the second current collector 80, the second electrode 30, the separator 60, the first electrode 20, and the first current collector 70. In the case of electrochlorination, the following reaction takes place at the first electrode 20: 2H2O + 2e - -> H2+ 2OH - . In the case of electrochlorination, the following reactions take place at the second electrode 30: 2H2O -> O2+ 4 H + + 4th - , and 2Cl - - > Cl2+ 2nd - .

[0230] According to a second variant as defined in the invention (multi-compartment or multi-block separator), the reactor is used for the implementation of water electrolysis or as a redox flow battery, and the electrically conductive material of the second electrode is a bio-sourced carbon. The diagram shows the configuration of the reactor for water electrolysis (a) and as a redox flow battery (b).

[0231] More particularly, a first liquid electrolyte enters the reactor100 through the first inlet41 in a direction D F1 (parallel to the main flow direction D F0 ), said first inlet 41 being positioned upstream of (i.e. before) the second current collector 80 and the first liquid electrolyte leaves the reactor 100 via the first outlet 51 in a direction D F1’ perpendicular to direction D F1, said first outlet51 being positioned downstream of (i.e. after) the second electrode30, perpendicular to the first inlet41 and at the level of a first compartment61 of the separator6. The first liquid electrolyte then moves in a continuous flow from the first inlet41 to the first outlet51 in a direction D F1 , then a direction D F1’ by successively crossing in this order the second current collector80, the second electrode30 and the first compartment61 of the separator6.

[0232] The reactor further comprises a second inlet 42 and a second outlet 52 so that a second liquid electrolyte enters the reactor 100 through the second inlet in a direction D F2 (parallel to the main flow direction D F0), said second inlet 42 being positioned upstream of (i.e. before) the first current collector 70 and the second liquid electrolyte exits the reactor 100 via the second outlet 52 in a direction D F2’ perpendicular to direction D F2 , said second outlet52 being positioned downstream of (i.e. after) the first electrode20, perpendicular to the second inlet42 and at the level of a second compartment62 of the separator6. The second liquid electrolyte then moves in a continuous flow from the second inlet42 to the second outlet52 in a direction D F2 , then a direction D F2’ by successively crossing in this order the first current collector70, the first electrode20 and the second compartment62 of the separator6.

[0233] The first and second compartments (61, 62) are separated by an ion exchange membrane11. This ensures ionic continuity within the reactor. The process makes it possible to transform water into oxygen and hydrogen in the case of water electrolysis, or vanadium V ions 5+ and V 2+ in vanadium V ions 4+ and V 3+ respectively in the case of the redox flow battery.

[0234] In the, the reactor 101 is identical to that of the except with respect to the separator 6 which further comprises a third compartment 63 interposed between the first and second compartments (61, 62) such that the first and third compartments (61, 63) are separated by an ion exchange membrane such as a cation membrane 12, and the second and third compartments (62, 63) are separated by an ion exchange membrane such as an anion membrane 13. The reactor 101 further comprises a third inlet 43 and a third outlet 53, such that a third liquid electrolyte enters the reactor 101 through the third inlet 43 in a direction D F3 , said third inlet43 being positioned at the level of the third compartment63 of the separator6, and the third liquid electrolyte leaves the reactor101 through the third outlet53 in the direction D F3, said third outlet53 being positioned at the level of the third compartment63 of the separator6. The third liquid electrolyte then moves in a continuous flow from the third inlet43 to the third outlet53 in a direction D F3 crossing the third compartment63 of the separator6.

[0235] According to this, the reactor is a reactor for the implementation of desalination of sea water, or for the production of electrical energy from osmotic energy and salt water, and the electrically conductive material of the second electrode is a bio-sourced carbon.

Claims

Fixed bed flow electrochemical reactor (1, 10, 100), characterized in that it comprises:- at least one first volume electrode (2, 20) comprising an electrically conductive material, preferably a biosourced carbon,- at least one second surface or volume electrode (3, 30) comprising an electrically conductive material, the second electrode being electrically connected to said first electrode,- at least one first inlet (4, 40, 41) and at least one first outlet (5, 50, 51), configured respectively to bring a liquid electrolyte in a continuous flow into the reactor, and to take said liquid electrolyte out in a continuous flow from the reactor, and- at least one separator (6) comprising at least one dielectric part in contact with said first and second electrodes, said separator (6) being configured to separate the first (2, 20) and second (3, 30) electrodes, to ensure compression on said first electrode (2, 20),and to allow movement of the liquid electrolyte in a continuous flow from the first inlet (4,40,41) to the first outlet (5,50,51)., Reactor (1,10,100) according to claim 1, characterized in that the separator (6) is a rigid separator, preferably having a Young's modulus of at least 1.5 GPa, and particularly preferably of at most 250 GPa. Reactor (1,10,100) according to claim 1 or 2, characterized in that the second electrode (3,30) is a volume electrode, and in that the first electrode (2,20) has a volume V1 and the second electrode (3,30) has a volume V2 so that V1 / V2 ranges from 1 to 100. Reactor (1, 10, 100) according to any one of the preceding claims, characterized in that the dielectric part of the separator (6) comprises at least one polymer material, preferably chosen from polyamides, polycarbonates, polyetherimides, polyolefins, polystyrenes, polyacrylates, polymethacrylates, polyaryletherketones, and one of their mixtures. Reactor (1,10,100) according to any one of the preceding claims, characterized in that the first electrode (2,20) has a specific volume ranging from 0.1 to 10 cm 3 / g, preferably 2.5 to 5.0 cm 3 / g, and particularly preferably ranging from 3.0 to 4.5 cm 3 / g. Reactor (1,10,100) according to any one of the preceding claims, characterized in that the reactor (1,10,100) comprises at least one means configured to obtain a movement of the liquid electrolyte in continuous flow within said reactor (1,10,100) with a flow rate ranging from 0.1 to 5*10 8 ml / min, and preferably ranging from 1 to 2.5*10 7 ml / min Reactor (1, 10, 100) according to any one of the preceding claims, characterized in that the separator (6) is a hollow element provided with at least one closing element having one or more openings, to allow the continuous flow movement of the liquid electrolyte from the first electrode (2, 20) or the second electrode (3, 30) towards the first outlet (5, 50, 51). Reactor (1, 10, 100) according to any one of the preceding claims, characterized in that the electrically conductive material of the first electrode (2, 20) is a biosourced carbon in the form of granules, chips, or pellets, preferably of average size ranging from 250 µm to 100 mm. Reactor (1, 10, 100) according to any one of the preceding claims, characterized in that the electrically conductive material of the second electrode (3, 30) is chosen from ferrous waste, iron, iron alloys, bio-sourced carbon, and one of their mixtures. Reactor (1,10,100) according to any one of the preceding claims, characterized in that the separator (6) represents from 10% to 70% by volume, relative to the total volume of the reactor. Reactor (1,10,100) according to any one of the preceding claims, characterized in that a compressive force is applied by the separator (6) to said first electrode (2,20) and possibly the second electrode (3,30) and ranges from 10 kPa to 10000 kPa. Reactor (1,10,100) according to any one of the preceding claims, characterized in that the liquid electrolyte enters or is introduced into the reactor (1,10,100) in a main flow direction D F0 and the liquid electrolyte moves in a continuous flow within the reactor according to one or other of the following alternatives: - the liquid electrolyte moves in a continuous flow from the first inlet (4, 40, 41) to the first outlet (5, 50, 51) in a direction D F parallel to the main flow direction D F0, by successively crossing in this order the second electrode (3,30), the separator (6), the first electrode (2,20), or- (a) a first liquid electrolyte moves in continuous flow from the first inlet (4,40,41) to the first outlet (4,40,41): in a direction D F1 parallel to the main flow direction D F0 , then a direction D F1’ perpendicular to direction D F1 by successively crossing in this order the second electrode (3, 30) and a first compartment of the separator (61), and- (b) a second liquid electrolyte moves in continuous flow from a second inlet (42) to a second outlet (52): in a direction D F2 parallel to the main flow direction D F0 , then a direction D F2’ perpendicular to direction D F2 by successively crossing in this order the first electrode (2,20) and a second compartment of the separator (62). Use of an electrochemical reactor (1, 10, 100) as defined in any one of claims 1 to 12, for depolluting a liquid medium comprising at least one organic pollutant, for disinfecting water by electrochlorination, for carrying out the electrolysis of water, for carrying out desalination of sea water, for energy storage, or for the production of electrical energy from osmotic energy. Method for decontaminating a liquid medium comprising at least one organic pollutant, preferably chosen from industrial effluents, wastewater, used oil emulsions, and oil-laden wastewater emulsions, comprising at least one organic pollutant, characterized in that:- said method comprises at least one step of degrading said organic pollutant in an oxidizing medium generated by the use of an electrochemical reactor (1, 10, 100) as defined in any one of claims 1 to 12 wherein:- the liquid electrolyte comprises said liquid medium and at least one oxidizing agent, and- the electrically conductive material of the first electrode is a biosourced carbon, and the electrically conductive material of the second electrode is chosen from iron, ferrous waste and iron alloys. Method according to claim 14, characterized in that the organic pollutant is chosen from plasticizers, herbicides, pesticides, endocrine disruptors, pharmaceutical products, per- and polyfluoroalkyls, fungicides, their metabolites, and one of their mixtures.

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