EP3850126A1 - Regeneration of a bio-electrode of a bio-electrochemical device - device and associated method - Google Patents

Regeneration of a bio-electrode of a bio-electrochemical device - device and associated method

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Publication number
EP3850126A1
EP3850126A1 EP19787025.6A EP19787025A EP3850126A1 EP 3850126 A1 EP3850126 A1 EP 3850126A1 EP 19787025 A EP19787025 A EP 19787025A EP 3850126 A1 EP3850126 A1 EP 3850126A1
Authority
EP
European Patent Office
Prior art keywords
bio
anode
gas
bubbles
diffuser
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19787025.6A
Other languages
German (de)
French (fr)
Inventor
Alain Bergel
Théodore BOUCHEZ
Elise BLANCHET
Benjamin Erable
Luc Etcheverry
Yannick FAYOLLE
Alain HUYARD
Elie Le Quemener
Pierre MAURICRACE
JiangHao TIAN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Centre National de la Recherche Scientifique CNRS
Institut National Polytechnique de Toulouse INPT
Institut National de Recherche pour lAgriculture lAlimentation et lEnvironnement
Vigie Groupe SAS
Original Assignee
Centre National de la Recherche Scientifique CNRS
Institut National Polytechnique de Toulouse INPT
Suez Groupe SAS
Institut National de Recherche pour lAgriculture lAlimentation et lEnvironnement
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Centre National de la Recherche Scientifique CNRS, Institut National Polytechnique de Toulouse INPT, Suez Groupe SAS, Institut National de Recherche pour lAgriculture lAlimentation et lEnvironnement filed Critical Centre National de la Recherche Scientifique CNRS
Publication of EP3850126A1 publication Critical patent/EP3850126A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M21/00—Bioreactors or fermenters specially adapted for specific uses
    • C12M21/12—Bioreactors or fermenters specially adapted for specific uses for producing fuels or solvents
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M35/00—Means for application of stress for stimulating the growth of microorganisms or the generation of fermentation or metabolic products; Means for electroporation or cell fusion
    • C12M35/02—Electrical or electromagnetic means, e.g. for electroporation or for cell fusion
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to the bio-electrochemical field, and more particularly relates to systems and methods of electrochemical synthesis using bio-electrochemical devices, that is to say electrochemical devices including at least one of the electrodes called bio. -electrode, is in contact with microorganisms.
  • bioelectrochemical synthesis devices make it possible in particular, from organic waste, to produce organic molecules such as organic acids and / or alcohols.
  • bio-electrochemical device which comprises both a bio-anode and a bio-cathode, the electrolyte of the anode compartment as well as the electrolyte of the cathode compartment containing microorganisms in suspension or in the form of biofilm (WO2016 / 051064).
  • the activity of the bio-cathode is optimized for the production of particular chemical species in the electrolyte, such as acetic, lactic and / or propionic acids or alcohols.
  • These microbial syntheses of organic molecules, involving in particular electrochemical redox reactions, are carried out using electroactive bacteria present on the surface of the electrode.
  • One of the current problems to be solved is to improve the reliability and durability of these bioelectrochemical devices, with a view to applications at the industrial stage.
  • the main objective is to increase the durability of the bio-anode. It has indeed been observed that the activity of this bioanode decreases considerably after a few weeks of operation. This phenomenon has been defined as the “aging” of the bioanode, probably due to clogging of the biofilm on this electrode. Indeed, a biofilm composed of electro-active bacteria (in particular of the genus Geobacter) is necessary for the functioning of the bio-anode. Other non-electroactive microorganisms also develop on this biofilm and thus inhibit its electro-catalytic activity. The deposition of insoluble particles further aggravates this effect.
  • An object of the invention is therefore to propose a means of acting against the "aging" of the bio-anode, and more generally against the decrease in the electrochemical activity of a bio-electrode.
  • the document JPH0416746 describes a system for cleaning probes intended to measure certain physicochemical parameters continuously in wastewater, in particular the concentration of dissolved 0 2 .
  • An air bubbling system makes it possible to generate currents in order to detach the deposits formed on the surface of the optical detection window, which alter the measurement, for example of dissolved oxygen.
  • the generation of these bubbles is carried out in situ (inside the measuring cell) by means of electrodes allowing the electrolysis of water or by means of a heating resistance, arranged respectively on the side and other or below the measurement window to be cleaned.
  • Such solutions adaptable to bioelectrodes (heating is to be excluded so as not to destroy the active biofilm and the generation of oxygen by electrolysis is to be avoided for operation in an anaerobic medium).
  • the document JP5924241 describes a device for continuous measurement of the oxygen dissolved in water by means of a probe placed in a cylindrical envelope in which the water circulates. To avoid deposits which could affect the measurement of the probe, a strong upward current of water around the probe is created by the injection of air bubbles in the upper part of the envelope, above said probe.
  • the solutions of the prior art are by no means satisfactory, for solving the aging of bio-electrodes in a bio-electrochemical device, in particular in a bio-electrochemical synthesis device, which causes a significant reduction in the current density.
  • a first object of the invention is therefore to overcome the drawbacks of the prior art by proposing, in a bio-electrochemical device, in particular in a bio-electrochemical synthesis device, a system making it possible to rid the surface of a bio- electrode of impurities or microorganisms interfering with or inhibiting its functioning.
  • Another object of the invention is to propose, in such a device, means making it possible to regenerate or restore the electrochemical activity of a “aging” bio-electrode, without stopping the operation of the synthesis device.
  • Another object of the invention is to propose a system for "regenerating" the surface of the bio-electrode, in particular a bio-anode, without affecting, or at least maintaining at least in part, the electroactive biofilm present. on this surface.
  • the present invention relates to an electrochemical device comprising at least one anode and at least one cathode each having a surface immersed in at least one compartment containing an electrolyte, and optionally a reference electrode, a potential difference being applied, in operation , between the anode and the cathode or between the anode and the reference electrode, at least one of the anode or cathode electrodes being a bio-electrode immersed in an electrolyte containing microorganisms, said bio-electrode being covered in operation of a biofilm, characterized in that it comprises a diffuser, connected to a gas source, and arranged in an area situated below or in the lower part of the bio-electrode, the diffuser having outlet openings of said gas capable of generating gas bubbles sweeping the surface of said bio-electrode and / or causing turbulence around e the latter, said bubbles being used to regenerate said bio-electrode, during the operation of the electrochemical device
  • the invention relates to a bioelectrochemical device comprising at least one anode and at least one cathode each having a surface immersed in at least one compartment containing an electrolyte, and optionally a reference electrode, a potential difference being applied, in operation, between the anode and the cathode or between the anode and the reference electrode, at least one of the anode electrodes being a bio-electrode called bio-anode immersed in an electrolyte containing microorganisms, said bio- anode being covered in operation with a biofilm, comprising anodic electroactive microorganisms,
  • a diffuser connected to a gas source, and disposed in an area located below or in the lower part of the bio-anode, the diffuser having outlet orifices for said gas capable of generating gas bubbles sweeping the surface of said bio-anode and / or causing turbulence around it, said bubbles being used to regenerate said bio-anode, during the operation of the electrochemical device.
  • Such a diffuser makes it possible to inject, into a compartment containing the electrolyte, gas bubbles which will thus touch or sweep the surface of the bio-anode and / or create turbulence in the electrolyte near said surface of the bio-anode making it possible to "unhook" impurities (such as for example inert debris from waste, or mineral precipitates) of the biofilm, as well as microorganisms from the outer layer of the biofilm covering said bio-anode.
  • impurities such as for example inert debris from waste, or mineral precipitates
  • sweeping is meant here a mechanical action of the gas bubbles on the surface of the bio-anode.
  • a bio-anode "covered with biofilm” means that the bio-anode is covered at least over part of its surface immersed in the electrolyte by a bacterial biofilm. According to one embodiment, the entire submerged surface of the bioanode is covered with biofilm. Alternatively, according to another embodiment, only part of the surface of the bio-anode is covered with biofilm. In this latter embodiment, the surface covered with biofilm is sufficient to generate the desired activity, in particular in the case of waste oxidation or bioelectrochemical synthesis.
  • the electro-active microorganisms of the basal layers of the biofilm remain “attached” to said bio-anode.
  • the fraction (or at least a fraction) of the electroactive biofilm is thus preserved.
  • Electroactive microorganisms are typically anaerobic microorganisms. Microorganisms differ depending on the electrode on which they grow as a biofilm, and the characteristics of the electrolyte in which they are immersed. For example, when wastewater or bio-waste is injected into the anode electrolyte, there is a large population affiliated with the genus Geobacter. On the other hand, in a saline environment, other genera such as Geoalkalibacter or Desulforomonas can become dominant.
  • microorganisms when the microorganisms are located on the anode, we speak of anodic electroactive microorganisms, while when the microorganisms are located on the cathode, we speak of cathodic or electrotrophic electroactive microorganisms.
  • the diffuser is in the form of a ramp comprising a multitude of outlet orifices, said orifices preferably being oriented towards the surface of the bio-anode and / or parallel to said surface.
  • the diffuser comprises between 8 and 50 orifices, in particular between 8 and 20 orifices.
  • the gas outlet orifices of the diffuser have a diameter generally greater than or equal to 1 mm, preferably greater than or equal to 2 mm, and for example between 2 and 6 mm, delivering bubbles of a few mm in diameter. These orifices can be more or less spaced from each other.
  • the diffuser is preferably made of metal, in particular stainless steel, it can also be made of polymeric material. It can be in the form of one or more perforated, single, double, or U-shaped ramps, arranged parallel to the base of the bio-anode. As a variant, for large bio-anodes, a single diffuser or an additional diffuser may be placed halfway up said bio-anode.
  • Said gas can be chosen from: nitrogen, a biogas or a fermentation gas or a mixture of these.
  • Biogas is understood to mean a gas resulting from a methanisation process and containing mainly CH 4 and CO 2 , the fermentation gas mainly containing CO 2 and dihydrogen.
  • the fermentation gas can for example be that produced during the operation of the bio-electrochemical device.
  • the gas may be the gas produced by the anode or cathode compartment or a mixture of these.
  • said gas comprises an oxygen content of less than or equal to 30% by volume, preferably less than 20% by volume, more preferably less than 10% by volume.
  • said gas bubbles generated do not negatively impact the anaerobic medium necessary for the proper functioning of the device, whether it is a bio-cell, a device for digesting waste and / or sludge from a station. purification, or a device for producing certain molecules (electrochemical synthesis device).
  • said gas is devoid of oxygen, that is to say contains an oxygen content of less than 1%, preferably less than 0.1% by volume of oxygen.
  • the invention advantageously applies to bio-electrochemical synthesis devices comprising at least one bio-anode and one bio-cathode as described in patent application WO2016 / 051064.
  • the bio-anode is advantageously in planar form, but can also be in granular form. It can be rigid or flexible.
  • An example of a flexible bio-anode is in particular a carbon film, for example held on a grid.
  • the retaining grid is preferably made of metal, such as stainless steel.
  • the cathode is also a bio-electrode, that is to say that the device comprises both a bio-anode and a bio-cathode.
  • the device can then comprise at least one diffuser per bio-electrode.
  • the device comprises at least two compartments, in particular an anode compartment and a cathode compartment. These compartments can be separated for example by a salt bridge, or by one or more ion-exchange membranes.
  • the bioelectrochemical device according to the invention can advantageously be a bioelectrochemical synthesis device.
  • the present invention also relates to a method for regenerating a bioelectrode of an electrochemical device as described above, characterized in that the method comprises a phase of production of gas bubbles below or in the lower part of the bio-electrode, sweeping the surface of said bio-anode and / or creating turbulence around the latter, during the operation of said device.
  • This production of gas bubbles can be carried out continuously, or intermittently (at regular intervals or not) or be triggered only when the current density at the electrode concerned drops (for a given fixed potential) or reaches a threshold predetermined.
  • the diffuser generates a gas flow rate greater than 0.01 ml_ / s per cm 2 of electrode surface, preferably greater than 0.1 ml_ / s, more preferably still greater than 1 ml_ / s per cm 2 of electrode surface, creating a scan of the surface of the bio-anode with gas bubbles produced with preferably a gas flow rate of at least 50 m / h, advantageously for a duration of at least 1 minute.
  • the speed of flow of the gas bubbles is calculated as the volume of gas in m 3 per m 2 of internal basal surface of the electrochemical compartment and per hour (not to be confused with the speed of ascent of the bubbles which is more difficult to control) .
  • the method according to the invention applies to the regeneration of a bio-anode combining a phase of production of gas bubbles and the reduction (but not the inversion) of the potential difference between the bio-anode and the cathode or between the bio-anode and the reference electrode, the phase of production of the gas bubbles and the reduction in the potential difference being preferably simultaneous.
  • the reduction in potential can, as a variant, be implemented just before the phase of production of gas bubbles, or just after the start of the production of gas bubbles.
  • the cathode can be a bio-cathode.
  • the regeneration process can combine a phase of production of gas bubbles and the decrease in the potential of the bio-anode compared to the reference electrode, the phase for producing gas bubbles and the decrease in potential is preferably simultaneous, the potential of the bioanode relative to the reference electrode then being between 0 and -0.4 V.
  • the methods described above aim to regenerate a bio-anode whose performance is degraded, but it is also possible to apply these methods as a preventive measure, even before the performance of the bio-electrochemical device begins to deteriorate.
  • Figure 1 shows schematically a bio-electrochemical synthesis device comprising a bio-anode and a bio-cathode;
  • Figure 2 is a top view of a first embodiment of the diffuser disposed on either side of a bio-anode;
  • Figure 3 is a side view of the diffuser of Figure 2;
  • Figure 4 is a top view of a second embodiment of a diffuser
  • Figures 5A and 5B are side views of the diffuser of Figure 4 according to two alternative positioning of the gas outlet orifices;
  • FIG. 6 presents two diagrams showing the current density at the bio-anode of the device of FIG. 1 equipped with the diffuser of FIG. 2, as a function of time, with or without bubbling of nitrogen;
  • FIG. 7 is a diagram showing the current density at the bio-anode of the device of FIG. 1 equipped with the diffuser of FIG. 2, as a function of time, with variation of the potential difference between the bio-anode and the reference electrode;
  • Figure 8 is a sectional diagram of an electrochemical device according to the invention comprising a bio-cathode and two bio-anodes equipped with a diffuser;
  • Figure 9 is a diagram showing the variation of the current density, as a function of time, of the device of Figure 8 with a nitrogen injection phase at 14.5 days.
  • the electrochemical device presented in FIG. 1, is an electrolyser 2 with double compartments comprising a bio-anode 3 and a bio-cathode 5.
  • the two anode 13 and cathode 15 compartments consist of 1.5 L glass containers. total volume, separated by a cation exchange membrane 14 (MEC,
  • the basic electrolyte 12A, 12C used is the synthetic medium for the BMP test (Biochemical Methane Potential ISO 1 1734).
  • a bio-waste from food was used as the substrate for the anode compartment. It is composed of potatoes (8.1%), tomatoes (3.4%), ground beef (8.1%), milk powder (0.7%), dry cookies (4, 1%) and water (75.6%). After mixing all the fractions, the bio-waste is left to ferment for 5 days at 35 degrees C °.
  • the composition of biowaste in volatile fatty acids (VFAs) is: lactic acid (55%), butyric acid (24%), propionic acid (10%), acetic acid (7%) , formic acid (3%) and valeric acid (1%).
  • the bio-waste was centrifuged at 7000 g for 5 min to collect its liquid fraction (the supernatant).
  • the average COD (chemical oxygen demand) of this fraction is around 100 g / L.
  • the biowaste supernatant was injected into the anode compartment to have a COD (Chemical Oxygen Demand) of 2.5 g / L each time the substrate was fed.
  • the basic material of the bio-anode is a piece of 4 cm * 4 cm of carbon fabric (Paxitech®, France) it is connected to the electrical circuit by a wire 23 of platinum.
  • the material of the bio-cathode is a stainless steel plate (Outokumpu®, 254 SMO) of 4 cm * 4 cm connected to the electrical circuit by a steel rod 25, preferably made of stainless steel also to avoid any galvanic coupling.
  • An ECS saturated calomel reference electrode is also present in the anode compartment 13.
  • the bio-anode was used as working electrode and the bio-cathode as a counter-electrode.
  • the anode 3 is biased at +0.158 V relative to the ECS reference electrode by means of a potentiostat (BioLogic®, France, VMP3 not shown, controlled by the EC-Lab software ).
  • the diffuser consists of an inlet pipe 7 of gas which separates into two branches 8 on either side of the bio-anode 3.
  • Each branch 8 of the diffuser 6 preferably comprises at least in its upper part, orifices 9 for the outlet of said gas, making it possible to generate bubbles 11 which sweep across the surface of said bio-anode and cause turbulence near its surface.
  • bubbles 1 1 make it possible to “unhook” impurities deposited on the surface of the bio-anode and probably also unhook part of the microorganisms present on the outside (relative to the surface of the bio-anode) from the biofilm which has formed on contact with this electrode.
  • the orifices 9 of the diffuser can advantageously be more or less oriented in the direction of the surface of the electrode to be regenerated (angles a and b relative to the plane 10 in FIGS. 3 and 5B).
  • the diffuser 6 can be in the form of a single conduit, disposed below the bio-anode, and widening below the latter, providing, in the central part, a longitudinal housing 16 for said electrode, the gas outlet orifices 9 being provided on either side of said housing 16.
  • the height H of this housing can be variable, and as a variant the angles a and b of FIG. 5B can be harmful, the upper part of the diffuser 6 then being substantially flat.
  • the potential E an of bioanode 3 was maintained at + 0.158 V relative to the reference electrode DHW.
  • the nitrogen bubbling phases (simple arrows in solid lines) were carried out with a flow rate of 50 ml of gas per second for 5 minutes.
  • the first phase of nitrogen bubbling at 10 days made it possible to regenerate the bio-anodes.
  • a subsequent modification of the potential of the bioanode E an to a value of -0.2 V compared to the reference electrode DHW made it possible to observe an increase in the current density (days 38 to approximately 65) in particular after each supply of waste substrate (30mL each time). An incident of disconnection of the bioanode occurred between days 70 and 80.
  • the dotted arrows CV in this figure correspond to current measurements by cyclic voltammetry.
  • the electrochemical device 1 according to the invention shown diagrammatically in FIG. 8 has been designed on a larger scale to mimic industrial conditions.
  • the electrolyser 2 comprises three compartments separated by two ion-exchange membranes: an anode compartment 13 which encloses two linked stainless steel plates (bio-anodes 3), this compartment is separated by a cation exchange membrane 17 inter-membrane compartment 18 which is itself separated by an anion exchange membrane 19 from the cathode compartment 15 which encloses the cathode 5 (steel frame retaining carbon in granular form).
  • each electrode bio-anodes 3 and cathode 5
  • the sizes of each electrode is 30X30 cm.
  • the electrodes are connected to a potentiostat (BioLogic®, France, VMP3 not shown, controlled by EC-Lab software). A potential difference of 1.1 V is imposed between the anodes and the cathode.
  • the electrolyte used at the cathode is the BMP medium modified with 30 g / L of NaHCO3.
  • the anode electrolyte is composed of 12.5 g / L of Na2HP04.7H20, 3 g / L of KH2P04, 0.5 g / L of NaCI, 1 g / L of NH4CI and 30 g / L of NaHC03 .
  • the electrolyte of the inter-menbranar compartment is composed of 35 g / L of KCI and 32.6 g / L of KH2P04.
  • the pH of the anode is maintained at 7 by automatic injection of a solution of H2CO3.
  • a diffuser 6 (double, with two gas inlets) is positioned just below the two bio-anodes and makes it possible to generate gas bubbles 11 on either side of the surfaces of these bio-anodes.
  • a bubbling phase (see arrow at 14 days in the diagram in FIG. 9) of 500 ml / s for 5 min (i.e. a flow rate of 0.55 ml / s per cm 2 of bio-anode), made it possible to restore part of the activity of these bio-anodes.
  • This flow rate related to the surface of the electrode is also equivalent to a gas flow rate of 120 m 3 / h and per m 2 of cross section of the base of the anode compartment.
  • the diffusers 6 used had orifices of 2 mm in diameter enabling bubbles of a few millimeters in size to be produced, causing strong turbulence around the surfaces of the electrodes. It has moreover been observed, in other tests, with a bio-anode made of flexible material (carbon tissue for example) that the efficiency of the regeneration of bio-anodes was increased when said bio-anode was made of material flexible.
  • the diffusers as presented in the examples above are easy to install and can be supplied by a source of nitrogen external to the electrochemical device, but it can also be envisaged to use the gas produced in situ, for example present in the gaseous sky of the electrodes, which has the advantage of disturbing the operation of the electrolyser as little as possible.
  • This bubbling allows, in a simple and effective manner, carried out during the operation of the electrolyser, to control the thickness of the biofilm on the treated electrode or at least an amount of electro-active biomass on its surface.

Abstract

A bio-electrochemical device comprising at least one bio-anode immersed in an electrolyte containing anodic electroactive microorganisms characterised in that it comprises a diffuser (6), connected to a gas source, and arranged in a zone situated below or in the lower part of the bio-anode, the diffuser having outlet openings (9) for the gas capable of generating gas bubbles (11) sweeping the surface of this bio-anode and/or causing turbulences around it, the bubbles (11) being used to regenerate this bio-anode, during the functioning of the electrochemical device. A method for regenerating a bio-anode (3) by means of the above device, that can be combined with a reduction in the difference in potential between the bio-anode (3) and the cathode (5).

Description

Régénération d’une bio-électrode d’un dispositif bio-électrochimique - dispositif et procédé associé  Regeneration of a bioelectrode of a bioelectrochemical device - device and associated method
DOMAINE DE L’INVENTION FIELD OF THE INVENTION
La présente invention concerne le domaine bio-électrochimique, et concerne plus particulièrement les systèmes et les procédés de synthèse électrochimique mettant en oeuvre des dispositifs bio-électrochimiques c’est-à-dire des dispositifs électrochimiques dont l’une au moins des électrodes appelée bio-électrode, est au contact de microorganismes.  The present invention relates to the bio-electrochemical field, and more particularly relates to systems and methods of electrochemical synthesis using bio-electrochemical devices, that is to say electrochemical devices including at least one of the electrodes called bio. -electrode, is in contact with microorganisms.
ETAT DE LA TECHNIQUE STATE OF THE ART
Ces dispositifs de synthèses bio-électrochimiques permettent notamment, à partir de déchets organiques, de produire des molécules organiques telles que des acides organiques et/ou des alcools.  These bioelectrochemical synthesis devices make it possible in particular, from organic waste, to produce organic molecules such as organic acids and / or alcohols.
En particulier, il a été mis au point récemment un tel dispositif bio-électrochimique, qui comporte à la fois une bio-anode et une bio-cathode, l’électrolyte du compartiment anodique ainsi que l’électrolyte du compartiment cathodique renfermant des microorganismes en suspension ou sous forme de biofilm(s) (WO2016/051064). Dans ce dispositif, l’activité de la bio-cathode est optimisée en vue de la production d’espèces chimiques particulières dans l’électrolyte, tels que les acides acétique, lactique et/ou propionique ou des alcools. Ces synthèses de molécules organiques par voie microbienne, impliquant en particulier des réactions d’oxydo-réduction électrochimiques, sont réalisées grâce à des bactéries électro-actives présentes à la surface de l’électrode. In particular, such a bio-electrochemical device has recently been developed, which comprises both a bio-anode and a bio-cathode, the electrolyte of the anode compartment as well as the electrolyte of the cathode compartment containing microorganisms in suspension or in the form of biofilm (WO2016 / 051064). In this device, the activity of the bio-cathode is optimized for the production of particular chemical species in the electrolyte, such as acetic, lactic and / or propionic acids or alcohols. These microbial syntheses of organic molecules, involving in particular electrochemical redox reactions, are carried out using electroactive bacteria present on the surface of the electrode.
Un des problèmes actuels à résoudre est d’améliorer la fiabilité et la durabilité de ces dispositifs bio-électrochimiques, en vue d’applications au stade industriel. One of the current problems to be solved is to improve the reliability and durability of these bioelectrochemical devices, with a view to applications at the industrial stage.
Plus particulièrement dans le dispositif mentionné ci-dessus, l’objectif principal est d’augmenter la durabilité de la bio-anode. Il a en effet été constaté que l’activité de cette bio-anode diminue considérablement après quelques semaines de fonctionnement. Ce phénomène a été défini comme le « vieillissement » de la bio- anode, probablement dû à un colmatage du biofilm sur cette électrode. En effet, un biofilm composé de bactéries électro-actives (notamment du genre Geobacter ) est nécessaire pour le fonctionnement de la bio-anode. D’autres microorganismes non électro-actifs se développent également sur ce biofilm et inhibent ainsi son activité électro-catalytique. Le dépôt de particules non-solubles aggrave encore cet effet. More particularly in the device mentioned above, the main objective is to increase the durability of the bio-anode. It has indeed been observed that the activity of this bioanode decreases considerably after a few weeks of operation. This phenomenon has been defined as the “aging” of the bioanode, probably due to clogging of the biofilm on this electrode. Indeed, a biofilm composed of electro-active bacteria (in particular of the genus Geobacter) is necessary for the functioning of the bio-anode. Other non-electroactive microorganisms also develop on this biofilm and thus inhibit its electro-catalytic activity. The deposition of insoluble particles further aggravates this effect.
Un but de l’invention est donc de proposer un moyen d’agir contre le « vieillissement » de la bio-anode, et plus généralement contre la diminution de l’activité électrochimique d’une bio-électrode. An object of the invention is therefore to propose a means of acting against the "aging" of the bio-anode, and more generally against the decrease in the electrochemical activity of a bio-electrode.
Il est connu de l’art antérieur de nettoyer des capteurs de mesure en contact avec des fluides biologiques, sujets à l’encrassement par formation d’un film bactérien. Ces procédés de nettoyage impliquent souvent de vider la cellule électrochimique pour laver ledit capteur par passage d’un fluide de nettoyage (solution aqueuse, organique ou gazeuse). It is known in the prior art to clean measurement sensors in contact with biological fluids, subject to fouling by the formation of a bacterial film. These cleaning methods often involve emptying the electrochemical cell to wash said sensor by passing a cleaning fluid (aqueous, organic or gaseous solution).
Une autre solution est présentée dans la demande de brevet WO 2014/108689 qui prévoit une étape de circulation d’air, selon un flux laminaire, après incorporation d’un échantillon à tester, dans la cellule de mesure à flux continu, afin de nettoyer la cellule et le capteur pendant le protocole de mesure. Another solution is presented in patent application WO 2014/108689 which provides for an air circulation step, in a laminar flow, after incorporation of a sample to be tested, in the continuous flow measurement cell, in order to clean the cell and the sensor during the measurement protocol.
Une telle solution, avec injection d’air, est tout à fait déconseillée pour les électrodes (notamment des bio-anodes) fonctionnant en milieu anaérobie, notamment dans les dispositifs de synthèse électrochimiques. Il n’est pas non plus possible de vider le compartiment anodique ou cathodique pour nettoyer l’électrode correspondante, car ceci interromprait le fonctionnement du dispositif électrochimique et nécessiterait une réadaptation des électrodes pour rétablir les microorganismes électro-actifs sur ces dernières. Such a solution, with air injection, is completely inadvisable for electrodes (in particular bio-anodes) operating in an anaerobic medium, in particular in electrochemical synthesis devices. It is also not possible to empty the anode or cathode compartment to clean the corresponding electrode, as this would interrupt the operation of the electrochemical device and would require readjustment of the electrodes to restore the electro-active microorganisms on them.
Le document JPH0416746 décrit un système de nettoyage de sondes destinées à mesurer certains paramètres physicochimiques en continu dans les eaux usées, notamment la concentration en 02 dissous. Un système de bullage d’air permet de générer des courants afin de détacher les dépôts formés à la surface de la fenêtre de détection optique, qui altèrent la mesure par exemple de l’oxygène dissous. La génération de ces bulles s’effectue in situ (à l’intérieur de la cellule de mesure) au moyen d’électrodes permettant l’électrolyse de l’eau ou au moyen d’une résistance chauffante, disposées respectivement de part et d’autre ou au-dessous de la fenêtre de mesure à nettoyer. De telles solutions ne sont pas non plus adaptables à des bio- électrodes (un chauffage est à exclure pour ne pas détruire le biofilm actif et la génération d’oxygène par électrolyse est à éviter pour un fonctionnement en milieu anaérobie). The document JPH0416746 describes a system for cleaning probes intended to measure certain physicochemical parameters continuously in wastewater, in particular the concentration of dissolved 0 2 . An air bubbling system makes it possible to generate currents in order to detach the deposits formed on the surface of the optical detection window, which alter the measurement, for example of dissolved oxygen. The generation of these bubbles is carried out in situ (inside the measuring cell) by means of electrodes allowing the electrolysis of water or by means of a heating resistance, arranged respectively on the side and other or below the measurement window to be cleaned. Nor are such solutions adaptable to bioelectrodes (heating is to be excluded so as not to destroy the active biofilm and the generation of oxygen by electrolysis is to be avoided for operation in an anaerobic medium).
Le document JP5924241 décrit un dispositif de mesure en continu de l’oxygène dissous dans l’eau au moyen d’une sonde placée dans une enveloppe cylindrique dans laquelle circule l’eau. Pour éviter les dépôts pouvant affecter la mesure de la sonde, un fort courant d’eau ascendant autour de la sonde est créé par l’injection de bulles d’air dans la partie supérieure de l’enveloppe, au-dessus de ladite sonde. The document JP5924241 describes a device for continuous measurement of the oxygen dissolved in water by means of a probe placed in a cylindrical envelope in which the water circulates. To avoid deposits which could affect the measurement of the probe, a strong upward current of water around the probe is created by the injection of air bubbles in the upper part of the envelope, above said probe.
Ainsi, les solutions de l’art antérieur ne sont nullement satisfaisantes, pour résoudre le vieillissement des bio-électrodes dans un dispositif bio-électrochimique, notamment dans un dispositif de synthèse bio-électrochimique, qui provoque une réduction importante de la densité de courant. Thus, the solutions of the prior art are by no means satisfactory, for solving the aging of bio-electrodes in a bio-electrochemical device, in particular in a bio-electrochemical synthesis device, which causes a significant reduction in the current density.
BUTS DE L’INVENTION GOALS OF THE INVENTION
Un premier but de l’invention est donc de pallier les inconvénients de l’art antérieur en proposant, dans un dispositif bio-électrochimique, notamment dans un dispositif de synthèse bio-électrochimique, un système permettant de débarrasser la surface d’une bio-électrode des impuretés ou microorganismes gênant ou inhibant son fonctionnement.  A first object of the invention is therefore to overcome the drawbacks of the prior art by proposing, in a bio-electrochemical device, in particular in a bio-electrochemical synthesis device, a system making it possible to rid the surface of a bio- electrode of impurities or microorganisms interfering with or inhibiting its functioning.
Un autre but de l’invention est de proposer, dans un tel dispositif, des moyens permettant de régénérer ou restaurer l’activité électrochimique d’une bio-électrode « vieillissante », sans arrêter le fonctionnement du dispositif de synthèse. Un autre but de l’invention est de proposer un système de « régénération » de la surface de la bio-électrode, notamment une bio-anode, sans affecter, ou du moins en maintenant au moins en partie, le biofilm électro-actif présent sur cette surface. Another object of the invention is to propose, in such a device, means making it possible to regenerate or restore the electrochemical activity of a “aging” bio-electrode, without stopping the operation of the synthesis device. Another object of the invention is to propose a system for "regenerating" the surface of the bio-electrode, in particular a bio-anode, without affecting, or at least maintaining at least in part, the electroactive biofilm present. on this surface.
DESCRIPTION DE L’INVENTION DESCRIPTION OF THE INVENTION
A cet effet la présente invention concerne un dispositif électrochimique comportant au moins une anode et au moins une cathode présentant chacune une surface immergée dans au moins un compartiment renfermant un électrolyte, et éventuellement une électrode de référence, une différence de potentiel étant appliquée, en fonctionnement, entre l'anode et la cathode ou entre l’anode et l’électrode de référence, au moins l’une des électrodes anode ou cathode étant une bio-électrode plongeant dans un électrolyte contenant des microorganismes, ladite bio-électrode étant recouverte en fonctionnement d’un biofilm, caractérisé en ce qu’il comprend un diffuseur, connecté à une source de gaz, et disposé dans une zone située au-dessous ou dans la partie inférieure de la bio-électrode, le diffuseur présentant des orifices de sortie dudit gaz aptes à générer des bulles de gaz balayant la surface de ladite bio-électrode et/ou provoquant des turbulences autour de celle-ci, lesdites bulles étant utilisées pour régénérer ladite bio-électrode, pendant le fonctionnement du dispositif électrochimique. To this end, the present invention relates to an electrochemical device comprising at least one anode and at least one cathode each having a surface immersed in at least one compartment containing an electrolyte, and optionally a reference electrode, a potential difference being applied, in operation , between the anode and the cathode or between the anode and the reference electrode, at least one of the anode or cathode electrodes being a bio-electrode immersed in an electrolyte containing microorganisms, said bio-electrode being covered in operation of a biofilm, characterized in that it comprises a diffuser, connected to a gas source, and arranged in an area situated below or in the lower part of the bio-electrode, the diffuser having outlet openings of said gas capable of generating gas bubbles sweeping the surface of said bio-electrode and / or causing turbulence around e the latter, said bubbles being used to regenerate said bio-electrode, during the operation of the electrochemical device.
Plus spécifiquement, l’invention concerne un dispositif bio-électrochimique comportant au moins une anode et au moins une cathode présentant chacune une surface immergée dans au moins un compartiment renfermant un électrolyte, et éventuellement une électrode de référence, une différence de potentiel étant appliquée, en fonctionnement, entre l'anode et la cathode ou entre l’anode et l’électrode de référence, au moins l’une des électrodes anode étant une bio-électrode dénommée bio-anode plongeant dans un électrolyte contenant des microorganismes, ladite bio-anode étant recouverte en fonctionnement d’un biofilm, comprenant des microorganismes électro-actifs anodiques, More specifically, the invention relates to a bioelectrochemical device comprising at least one anode and at least one cathode each having a surface immersed in at least one compartment containing an electrolyte, and optionally a reference electrode, a potential difference being applied, in operation, between the anode and the cathode or between the anode and the reference electrode, at least one of the anode electrodes being a bio-electrode called bio-anode immersed in an electrolyte containing microorganisms, said bio- anode being covered in operation with a biofilm, comprising anodic electroactive microorganisms,
caractérisé en ce qu’il comprend un diffuseur, connecté à une source de gaz, et disposé dans une zone située au-dessous ou dans la partie inférieure de la bio-anode, le diffuseur présentant des orifices de sortie dudit gaz aptes à générer des bulles de gaz balayant la surface de ladite bio-anode et/ou provoquant des turbulences autour de celle-ci, lesdites bulles étant utilisées pour régénérer ladite bio-anode, pendant le fonctionnement du dispositif électrochimique. characterized in that it comprises a diffuser, connected to a gas source, and disposed in an area located below or in the lower part of the bio-anode, the diffuser having outlet orifices for said gas capable of generating gas bubbles sweeping the surface of said bio-anode and / or causing turbulence around it, said bubbles being used to regenerate said bio-anode, during the operation of the electrochemical device.
Un tel diffuseur permet d’injecter, au sein d’un compartiment renfermant l’électrolyte, des bulles de gaz qui vont ainsi effleurer ou balayer la surface de la bio-anode et/ou créer des turbulences dans l’électrolyte à proximité de ladite surface de la bio-anode permettant de « décrocher » des impuretés (telles que par exemple des débris inertes issus des déchets, ou encore des précipités minéraux) du biofilm, ainsi que des microorganismes de la couche externe du biofilm recouvrant ladite bio-anode. Such a diffuser makes it possible to inject, into a compartment containing the electrolyte, gas bubbles which will thus touch or sweep the surface of the bio-anode and / or create turbulence in the electrolyte near said surface of the bio-anode making it possible to "unhook" impurities (such as for example inert debris from waste, or mineral precipitates) of the biofilm, as well as microorganisms from the outer layer of the biofilm covering said bio-anode.
Par « balayage » on entend ici une action mécanique des bulles de gaz à la surface de la bio-anode.  By "sweeping" is meant here a mechanical action of the gas bubbles on the surface of the bio-anode.
Au sens de la présente invention, une bio-anode « recouverte de biofilm » signifie que la bio-anode est recouverte au moins sur une partie de sa surface immergée dans l’électrolyte par un biofilm bactérien. Selon un mode de réalisation, la totalité de la surface immergée de la bio-anode est recouverte de biofilm. Alternativement, selon un autre mode de réalisation, une partie seulement de la surface de la bio-anode est recouverte de biofilm. Dans ce dernier mode de réalisation, la surface recouverte de biofilm est suffisante pour générer l’activité recherchée, notamment dans le cas d’une oxydation des déchets ou d’une synthèse bio-électrochimique. Within the meaning of the present invention, a bio-anode "covered with biofilm" means that the bio-anode is covered at least over part of its surface immersed in the electrolyte by a bacterial biofilm. According to one embodiment, the entire submerged surface of the bioanode is covered with biofilm. Alternatively, according to another embodiment, only part of the surface of the bio-anode is covered with biofilm. In this latter embodiment, the surface covered with biofilm is sufficient to generate the desired activity, in particular in the case of waste oxidation or bioelectrochemical synthesis.
Ce diffuseur pouvant être en action pendant le fonctionnement de la bio-anode, les microorganismes électro-actifs des couches basales du biofilm restent « accrochés » à ladite bio-anode. La fraction (ou au moins une fraction) du biofilm électro-actif est ainsi préservée. Since this diffuser can be in action during the functioning of the bio-anode, the electro-active microorganisms of the basal layers of the biofilm remain “attached” to said bio-anode. The fraction (or at least a fraction) of the electroactive biofilm is thus preserved.
Les microorganismes électro-actifs sont typiquement des microorganismes anaérobies. Les microorganismes diffèrent en fonction de l’électrode sur laquelle ils se développent sous forme de biofilm, et des caractéristiques de l'électrolyte dans lequel ils sont immergés. Par exemple, lorsque des eaux usées ou des biodéchets sont injectés dans l'électrolyte anodique, on observe une population abondante affiliée au genre Geobacter. Par contre, dans un milieu salin, d'autres genres tels que Geoalkalibacter ou Desulforomonas peuvent devenir dominants. Ainsi, lorsque les micro-organismes sont situés sur l’anode, on parle de microorganismes électro-actifs anodiques, tandis que lorsque les micro-organismes sont situés sur la cathode, on parle de microorganismes électro-actifs cathodiques ou électrotrophes.  Electroactive microorganisms are typically anaerobic microorganisms. Microorganisms differ depending on the electrode on which they grow as a biofilm, and the characteristics of the electrolyte in which they are immersed. For example, when wastewater or bio-waste is injected into the anode electrolyte, there is a large population affiliated with the genus Geobacter. On the other hand, in a saline environment, other genera such as Geoalkalibacter or Desulforomonas can become dominant. Thus, when the microorganisms are located on the anode, we speak of anodic electroactive microorganisms, while when the microorganisms are located on the cathode, we speak of cathodic or electrotrophic electroactive microorganisms.
Selon un mode de réalisation préféré, le diffuseur est sous la forme d’une rampe comportant une multitude d’orifices de sortie, lesdits orifices étant de préférence orientés vers la surface de la bio-anode et/ou parallèlement à ladite surface. Dans un mode de réalisation particulier, le diffuseur comprend entre 8 et 50 orifices, notamment entre 8 et 20 orifices. According to a preferred embodiment, the diffuser is in the form of a ramp comprising a multitude of outlet orifices, said orifices preferably being oriented towards the surface of the bio-anode and / or parallel to said surface. In a particular embodiment, the diffuser comprises between 8 and 50 orifices, in particular between 8 and 20 orifices.
Les orifices de sortie du gaz du diffuseur présentent un diamètre généralement supérieur ou égal à 1 mm, de préférence supérieur ou égal à 2 mm, et par exemple compris entre 2 et 6 mm, délivrant des bulles de quelques mm de diamètre. Ces orifices peuvent être plus ou moins écartés les uns des autres. The gas outlet orifices of the diffuser have a diameter generally greater than or equal to 1 mm, preferably greater than or equal to 2 mm, and for example between 2 and 6 mm, delivering bubbles of a few mm in diameter. These orifices can be more or less spaced from each other.
Le diffuseur est de préférence en métal, en particulier en acier inoxydable, il peut également être en matériau polymère. Il peut se présenter sous la forme d’une ou plusieurs rampes perforées, simples, doubles, ou en forme de U, disposées parallèlement à la base de la bio-anode. En variante, pour des bio-anodes de grandes tailles, un seul diffuseur ou un diffuseur supplémentaire peut être disposé à mi-hauteur de ladite bio-anode. The diffuser is preferably made of metal, in particular stainless steel, it can also be made of polymeric material. It can be in the form of one or more perforated, single, double, or U-shaped ramps, arranged parallel to the base of the bio-anode. As a variant, for large bio-anodes, a single diffuser or an additional diffuser may be placed halfway up said bio-anode.
Ledit gaz peut être choisi parmi : l’azote, un biogaz ou un gaz de fermentation ou un mélange de ceux-ci. Par biogaz, on entend un gaz issu d'un procédé de méthanisation et renfermant principalement du CH4 et du CO2, le gaz de fermentation renfermant majoritairement du CO2 et du dihydrogène. Said gas can be chosen from: nitrogen, a biogas or a fermentation gas or a mixture of these. Biogas is understood to mean a gas resulting from a methanisation process and containing mainly CH 4 and CO 2 , the fermentation gas mainly containing CO 2 and dihydrogen.
Le gaz de fermentation peut être par exemple celui produit au cours du fonctionnement du dispositif bio-électrochimique. En particulier, dans le cas d’un dispositif comprenant un compartiment anodique et un compartiment cathodique distincts ou physiquement séparés, le gaz peut être le gaz produit par le compartiment anodique ou cathodique ou un mélange de ceux-ci. The fermentation gas can for example be that produced during the operation of the bio-electrochemical device. In particular, in the case of a device comprising a separate or physically separate anode compartment and a cathode compartment, the gas may be the gas produced by the anode or cathode compartment or a mixture of these.
Selon un mode de réalisation particulier, ledit gaz comprend une teneur en oxygène inférieure ou égale à 30 % en volume, de préférence inférieure à 20 % en volume, de préférence encore inférieure à 10 % en volume. Ainsi les bulles de gaz générées n’impactent pas négativement le milieu anaérobie nécessaire au bon fonctionnement du dispositif, qu’il s’agisse d’une bio-pile, d’un dispositif de digestion des déchets et/ou des boues de station d’épuration, ou d’un dispositif de production de certaines molécules (dispositif de synthèse électrochimique). De manière avantageuse, ledit gaz est dépourvu d’oxygène, c’est-à-dire renferme une teneur en oxygène inférieure à 1%, de préférence inférieure à 0,1 % en volume en oxygène. According to a particular embodiment, said gas comprises an oxygen content of less than or equal to 30% by volume, preferably less than 20% by volume, more preferably less than 10% by volume. Thus the gas bubbles generated do not negatively impact the anaerobic medium necessary for the proper functioning of the device, whether it is a bio-cell, a device for digesting waste and / or sludge from a station. purification, or a device for producing certain molecules (electrochemical synthesis device). Advantageously, said gas is devoid of oxygen, that is to say contains an oxygen content of less than 1%, preferably less than 0.1% by volume of oxygen.
L’invention s’applique avantageusement aux dispositifs de synthèse bio- électrochimique comportant au moins une bio-anode et une bio-cathode tels que décrits dans la demande de brevet WO2016/051064. The invention advantageously applies to bio-electrochemical synthesis devices comprising at least one bio-anode and one bio-cathode as described in patent application WO2016 / 051064.
La bio-anode se présente avantageusement sous forme plane, mais peut également être sous forme granulaire. Elle peut être rigide ou bien souple. Un exemple de bio- anode souple est notamment un film de carbone, par exemple maintenu sur une grille, La grille de maintien est de préférence en métal, tel que l’acier inoxydable. The bio-anode is advantageously in planar form, but can also be in granular form. It can be rigid or flexible. An example of a flexible bio-anode is in particular a carbon film, for example held on a grid. The retaining grid is preferably made of metal, such as stainless steel.
Selon un autre mode de réalisation de l’invention, la cathode est également une bio- électrode, c’est-à-dire que le dispositif comprend à la fois une bio-anode et une bio- cathode. Dans ce mode de réalisation, le dispositif peut alors comprendre au moins un diffuseur par bio-électrode. According to another embodiment of the invention, the cathode is also a bio-electrode, that is to say that the device comprises both a bio-anode and a bio-cathode. In this embodiment, the device can then comprise at least one diffuser per bio-electrode.
Selon un mode de réalisation particulier de l’invention, le dispositif comprend au moins deux compartiments, notamment un compartiment anodique et un compartiment cathodique. Ces compartiments peuvent être séparés par exemple par un pont salin, ou par une ou plusieurs membranes échangeuses d’ions. According to a particular embodiment of the invention, the device comprises at least two compartments, in particular an anode compartment and a cathode compartment. These compartments can be separated for example by a salt bridge, or by one or more ion-exchange membranes.
Ainsi, le dispositif bio-électrochimique selon l’invention peut avantageusement être un dispositif de synthèse bio-électrochimique.  Thus, the bioelectrochemical device according to the invention can advantageously be a bioelectrochemical synthesis device.
La présente invention concerne également un procédé de régénération d’une bio- électrode d’un dispositif électrochimique tel que décrit ci-dessus, caractérisé en ce que le procédé comprend une phase de production de bulles de gaz au-dessous ou dans la partie inférieure de la bio-électrode, balayant la surface de ladite bio-anode et/ou créant des turbulences autour de cette dernière, pendant le fonctionnement dudit dispositif. Cette production de bulles de gaz peut être effectuée en continu, ou par intermittence (à intervalles réguliers ou non) ou n’être déclenchée que lorsque la densité de courant à l’électrode concernée chute (pour un potentiel donné fixe) ou atteint un seuil prédéterminé. The present invention also relates to a method for regenerating a bioelectrode of an electrochemical device as described above, characterized in that the method comprises a phase of production of gas bubbles below or in the lower part of the bio-electrode, sweeping the surface of said bio-anode and / or creating turbulence around the latter, during the operation of said device. This production of gas bubbles can be carried out continuously, or intermittently (at regular intervals or not) or be triggered only when the current density at the electrode concerned drops (for a given fixed potential) or reaches a threshold predetermined.
De préférence, le diffuseur génère un débit de gaz supérieur à 0,01 ml_/s par cm2 de surface d’électrode, de préférence supérieur à 0,1 ml_/s, de préférence encore supérieur à 1 ml_/s par cm2 de surface d’électrode, créant un balayage de la surface de la bio-anode avec des bulles de gaz produites avec de préférence une vitesse débitante de gaz d’au moins 50m/h, avantageusement pendant une durée d’au moins 1 minute. La vitesse débitante des bulles de gaz est calculée comme le volume de gaz en m3 par m2 de surface basale intérieure du compartiment électrochimique et par heure (pour ne pas confondre avec la vitesse d’ascension des bulles qui est plus difficile à contrôler). Preferably, the diffuser generates a gas flow rate greater than 0.01 ml_ / s per cm 2 of electrode surface, preferably greater than 0.1 ml_ / s, more preferably still greater than 1 ml_ / s per cm 2 of electrode surface, creating a scan of the surface of the bio-anode with gas bubbles produced with preferably a gas flow rate of at least 50 m / h, advantageously for a duration of at least 1 minute. The speed of flow of the gas bubbles is calculated as the volume of gas in m 3 per m 2 of internal basal surface of the electrochemical compartment and per hour (not to be confused with the speed of ascent of the bubbles which is more difficult to control) .
Selon un mode de réalisation avantageux, le procédé selon l’invention s’applique à la régénération d’une bio-anode combinant une phase de production de bulles de gaz et la diminution (mais non l'inversion) de la différence de potentiel entre la bio-anode et la cathode ou entre la bio-anode et l’électrode de référence, la phase de production des bulles de gaz et la diminution de la différence de potentiel étant de préférence simultanées. According to an advantageous embodiment, the method according to the invention applies to the regeneration of a bio-anode combining a phase of production of gas bubbles and the reduction (but not the inversion) of the potential difference between the bio-anode and the cathode or between the bio-anode and the reference electrode, the phase of production of the gas bubbles and the reduction in the potential difference being preferably simultaneous.
Les inventeurs ont en effet constaté que cette combinaison était efficace pour restaurer l’activité de la bio-anode. The inventors have indeed found that this combination is effective in restoring the activity of the bioanode.
La diminution du potentiel peut, en variante, être mise en oeuvre juste avant la phase de production de bulles de gaz, ou juste après le démarrage de la production des bulles de gaz.  The reduction in potential can, as a variant, be implemented just before the phase of production of gas bubbles, or just after the start of the production of gas bubbles.
Des résultats intéressants ont été observés lorsque la différence de potentiel entre la bio-anode et la cathode ou entre la bio-anode et l’électrode de référence est comprise entre 10 et 50 % de la valeur de fonctionnement du dispositif électrochimique. Interesting results have been observed when the potential difference between the bio-anode and the cathode or between the bio-anode and the reference electrode is between 10 and 50% of the operating value of the electrochemical device.
Dans ce cas, la cathode peut être une bio-cathode.  In this case, the cathode can be a bio-cathode.
De même, lorsque le dispositif bio-électrochimique comprend une électrode de référence (par exemple électrode au calomel saturée, notée « ECS »), le procédé de régénération peut combiner une phase de production de bulles de gaz et la diminution du potentiel de la bio-anode par rapport à l’électrode de référence, la phase de production des bulles de gaz et la diminution du potentiel étant de préférence simultanées, le potentiel de la bio-anode par rapport à l’électrode de référence étant alors compris entre 0 et -0,4 V. Likewise, when the bioelectrochemical device comprises an electrode for reference (for example saturated calomel electrode, noted “DHW”), the regeneration process can combine a phase of production of gas bubbles and the decrease in the potential of the bio-anode compared to the reference electrode, the phase for producing gas bubbles and the decrease in potential is preferably simultaneous, the potential of the bioanode relative to the reference electrode then being between 0 and -0.4 V.
Les procédés décrits ci-dessus visent à régénérer une bio-anode dont les performances sont dégradées, mais il est également possible d’appliquer ces procédés à titre préventif, avant même que des performances du dispositif bio-électrochimique commencent à se dégrader. The methods described above aim to regenerate a bio-anode whose performance is degraded, but it is also possible to apply these methods as a preventive measure, even before the performance of the bio-electrochemical device begins to deteriorate.
D’autres caractéristiques et avantages de l’invention apparaîtront dans la description ci-dessous d’exemples de réalisation, non limitatifs, en référence aux schémas annexés, dans lesquels : Other characteristics and advantages of the invention will appear in the description below of nonlimiting exemplary embodiments, with reference to the attached diagrams, in which:
La figure 1 schématise un dispositif de synthèse bio-électrochimique comportant une bio-anode et une bio-cathode ; Figure 1 shows schematically a bio-electrochemical synthesis device comprising a bio-anode and a bio-cathode;
La figure 2 est une vue de dessus d'un premier mode de réalisation du diffuseur disposé de part et d'autre d'une bio-anode ;  Figure 2 is a top view of a first embodiment of the diffuser disposed on either side of a bio-anode;
La figure 3 est une vue de côté du diffuseur de la figure 2 ;  Figure 3 is a side view of the diffuser of Figure 2;
La figure 4 est une vue de dessus d'un deuxième mode de réalisation d'un diffuseur ; Figure 4 is a top view of a second embodiment of a diffuser;
Les figures 5A et 5B sont des vues de côté du diffuseur de la figure 4 selon deux variantes de positionnement des orifices de sortie de gaz ; Figures 5A and 5B are side views of the diffuser of Figure 4 according to two alternative positioning of the gas outlet orifices;
La figure 6 présente deux diagrammes montrant la densité de courant à la bio-anode du dispositif de la figure 1 équipée du diffuseur de la figure 2, en fonction du temps, avec ou sans bullage d'azote ; FIG. 6 presents two diagrams showing the current density at the bio-anode of the device of FIG. 1 equipped with the diffuser of FIG. 2, as a function of time, with or without bubbling of nitrogen;
La figure 7 est un diagramme montrant la densité de courant à la bio-anode du dispositif de la figure 1 équipée du diffuseur de la figure 2, en fonction du temps, avec variation de la différence de potentiel entre la bio-anode et l'électrode de référence ; FIG. 7 is a diagram showing the current density at the bio-anode of the device of FIG. 1 equipped with the diffuser of FIG. 2, as a function of time, with variation of the potential difference between the bio-anode and the reference electrode;
La figure 8 est un schéma en coupe d'un dispositif électrochimique selon l'invention comportant une bio-cathode et deux bio-anodes équipées d'un diffuseur ; La figure 9 est un diagramme présentant la variation de la densité de courant, en fonction du temps, du dispositif de la figure 8 avec une phase injection d'azote à 14,5 jours. Figure 8 is a sectional diagram of an electrochemical device according to the invention comprising a bio-cathode and two bio-anodes equipped with a diffuser; Figure 9 is a diagram showing the variation of the current density, as a function of time, of the device of Figure 8 with a nitrogen injection phase at 14.5 days.
EXEMPLES EXAMPLES
Exemple 1  Example 1
Le dispositif électrochimique, présenté à la figure 1 , est un électrolyseur 2 à double compartiments comportant une bio-anode 3 et une bio-cathode 5. Les deux compartiments anodique 13 et cathodique 15 sont constitués de récipients en verre de 1 ,5 L de volume total, séparés par une membrane 14 échangeuse de cations (MEC, The electrochemical device, presented in FIG. 1, is an electrolyser 2 with double compartments comprising a bio-anode 3 and a bio-cathode 5. The two anode 13 and cathode 15 compartments consist of 1.5 L glass containers. total volume, separated by a cation exchange membrane 14 (MEC,
Fumasep® FKE, Germany). Les deux compartiments sont fermés par un couvercle et étanches au gaz. Fumasep® FKE, Germany). The two compartments are closed by a cover and gas-tight.
L’électrolyte de base 12A, 12C utilisé est le milieu synthétique du test de BMP (Biochemical Methane Potential ISO 1 1734). The basic electrolyte 12A, 12C used is the synthetic medium for the BMP test (Biochemical Methane Potential ISO 1 1734).
Substrat Substrate
Un biodéchet de produits alimentaires a été utilisé en tant que substrat du compartiment anodique. Il est composé de pommes de terre (8,1 %), de tomates (3,4%), de steak haché (8,1 %), de poudre de lait (0,7%), de biscuits secs (4,1 %) et d’eau (75,6%). Après le mélange de toutes les fractions, le biodéchet est laissé fermenter pendant 5 jours à 35 degrés C°. Ainsi, la composition du biodéchet en acides gras volatils (AGVs) est : l'acide lactique (55%), l'acide butyrique (24%), l'acide propionique (10%), l'acide acétique (7%), l'acide formique (3%) et l'acide valérique (1 %). Le biodéchet a été centrifugé à 7000 g pendant 5 min pour récolter sa fraction liquide (le surnageant). La DCO (demande chimique en oxygène) moyenne de cette fraction est d’environ 100 g/L. Le surnageant du biodéchet a été injecté dans le compartiment anodique pour avoir une DCO (Demande Chimique en Oxygène) de 2,5 g/L à chaque alimentation en substrat.  A bio-waste from food was used as the substrate for the anode compartment. It is composed of potatoes (8.1%), tomatoes (3.4%), ground beef (8.1%), milk powder (0.7%), dry cookies (4, 1%) and water (75.6%). After mixing all the fractions, the bio-waste is left to ferment for 5 days at 35 degrees C °. Thus, the composition of biowaste in volatile fatty acids (VFAs) is: lactic acid (55%), butyric acid (24%), propionic acid (10%), acetic acid (7%) , formic acid (3%) and valeric acid (1%). The bio-waste was centrifuged at 7000 g for 5 min to collect its liquid fraction (the supernatant). The average COD (chemical oxygen demand) of this fraction is around 100 g / L. The biowaste supernatant was injected into the anode compartment to have a COD (Chemical Oxygen Demand) of 2.5 g / L each time the substrate was fed.
Le matériau de base de la bio-anode est un morceau de 4 cm * 4 cm de tissu de carbone (Paxitech®, France) il est connecté au circuit électrique par un fil 23 de platine. Le matériau de la bio-cathode est une plaque d’acier inoxydable (Outokumpu®, 254 SMO) de 4 cm * 4 cm connectée au circuit électrique par une tige d’acier 25, de préférence en acier inoxydable également pour éviter tout couplage galvanique. The basic material of the bio-anode is a piece of 4 cm * 4 cm of carbon fabric (Paxitech®, France) it is connected to the electrical circuit by a wire 23 of platinum. The material of the bio-cathode is a stainless steel plate (Outokumpu®, 254 SMO) of 4 cm * 4 cm connected to the electrical circuit by a steel rod 25, preferably made of stainless steel also to avoid any galvanic coupling.
Une électrode de référence au calomel saturé ECS est également présente dans le compartiment anodique 13. La bio-anode a été utilisée comme électrode de travail et la bio-cathode en tant que contre-électrode.  An ECS saturated calomel reference electrode is also present in the anode compartment 13. The bio-anode was used as working electrode and the bio-cathode as a counter-electrode.
Selon un exemple de mise en oeuvre, l’anode 3 est polarisée à +0,158 V par rapport à l’électrode de référence ECS au moyen d'un potentiostat (BioLogic®, France, VMP3 non représenté, piloté par le logiciel EC-Lab). According to an example of implementation, the anode 3 is biased at +0.158 V relative to the ECS reference electrode by means of a potentiostat (BioLogic®, France, VMP3 not shown, controlled by the EC-Lab software ).
Après environ 30 jours de fonctionnement à ce potentiel, on constate que la densité de courant à la bio-anode chute fortement (voir figure 6), malgré des injections de substrat régulières (flèches blanches). After approximately 30 days of operation at this potential, we see that the current density at the bio-anode drops sharply (see Figure 6), despite regular substrate injections (white arrows).
La solution apportée à ce problème est l’incorporation, selon la présente invention, d’un diffuseur 6 de gaz au niveau de la partie inférieure ou au-dessous de la bio-anode (figures 2, 3 4 5A et 5B). The solution to this problem is the incorporation, according to the present invention, of a gas diffuser 6 at the level of the lower part or below the bio-anode (FIGS. 2, 3 4 5A and 5B).
Selon un premier mode de réalisation schématisé aux figures 2 et 3, le diffuseur se compose d’un conduit d’arrivée 7 de gaz qui se sépare en deux branches 8 de part et d’autre de la bio-anode 3. Chaque branche 8 du diffuseur 6 comporte, de préférence au moins dans sa partie supérieure, des orifices 9 de sortie dudit gaz, permettant de générer des bulles 1 1 qui viennent balayer la surface de ladite bio-anode et provoquer des turbulences à proximité de sa surface. According to a first embodiment shown schematically in Figures 2 and 3, the diffuser consists of an inlet pipe 7 of gas which separates into two branches 8 on either side of the bio-anode 3. Each branch 8 of the diffuser 6 preferably comprises at least in its upper part, orifices 9 for the outlet of said gas, making it possible to generate bubbles 11 which sweep across the surface of said bio-anode and cause turbulence near its surface.
Ces bulles 1 1 permettent de « décrocher » des impuretés déposées à la surface de la bio-anode et probablement également décrocher une partie des microorganismes présents en partie extérieure (par rapport à la surface de la bio-anode) du biofilm qui s’est formé au contact de cette électrode. Les orifices 9 du diffuseur peuvent être avantageusement plus ou moins orientés en direction de la surface de l’électrode à régénérer (angles a et b par rapport au plan 10 sur les figures 3 et 5B). Selon un deuxième mode de réalisation, le diffuseur 6 peut se présenter sous la forme d’un conduit unique, disposé au-dessous de la bio-anode, et s’élargissant au-dessous de cette dernière en ménageant, dans la partie centrale, un logement 16 longitudinal pour ladite électrode, les orifices 9 de sortie de gaz étant prévus de part et d’autre dudit logement 16. La hauteur H de ce logement peut être variable, et en variante les angles a et b de la figure 5B peuvent être nuis, la partie supérieure du diffuseur 6 étant alors sensiblement plane. These bubbles 1 1 make it possible to “unhook” impurities deposited on the surface of the bio-anode and probably also unhook part of the microorganisms present on the outside (relative to the surface of the bio-anode) from the biofilm which has formed on contact with this electrode. The orifices 9 of the diffuser can advantageously be more or less oriented in the direction of the surface of the electrode to be regenerated (angles a and b relative to the plane 10 in FIGS. 3 and 5B). According to a second embodiment, the diffuser 6 can be in the form of a single conduit, disposed below the bio-anode, and widening below the latter, providing, in the central part, a longitudinal housing 16 for said electrode, the gas outlet orifices 9 being provided on either side of said housing 16. The height H of this housing can be variable, and as a variant the angles a and b of FIG. 5B can be harmful, the upper part of the diffuser 6 then being substantially flat.
Deux dispositifs électrochimiques ont été conduits en parallèle. Un bullage d’azote (à 65 jours) à un débit de 50 ml_/s pendant 5 minutes (flèche noire) au moyen du diffuseur de la figure 2 a permis de régénérer la bio-anode du premier dispositif et de restaurer son activité à un niveau équivalent aux premiers jours de fonctionnement (densité de courant en trait plein sur le diagramme de la figure 6), alors que le second électrolyseur (contrôle) présente une densité de courant à la bio-anode très faible (traits pointillés). Two electrochemical devices were run in parallel. Nitrogen bubbling (at 65 days) at a flow rate of 50 ml / s for 5 minutes (black arrow) by means of the diffuser in FIG. 2 made it possible to regenerate the bio-anode of the first device and to restore its activity to a level equivalent to the first days of operation (current density in solid line on the diagram in Figure 6), while the second electrolyser (control) has a very low bio-anode current density (dotted lines).
Exemple 2 Example 2
Avec un dispositif identique à celui de l’exemple 1 ci-dessus a été testée la combinaison d’un bullage d’azote et d’une variation du potentiel de la bio-anode. Les résultats sont présentés sur le diagramme de la figure 7.  With a device identical to that of Example 1 above, the combination of nitrogen bubbling and a variation of the potential of the bio-anode was tested. The results are shown in the diagram in Figure 7.
Dans la première partie de l’expérience (de 0 à 38 jours), le potentiel Ean de la bio- anode 3 était maintenu à +0,158 V par rapport à l’électrode de référence ECS. Les phases de bullage d’azote (flèches simples en traits pleins) ont été réalisés avec un débit de 50 mL de gaz par seconde pendant 5 minutes. La première phase de bullage d’azote à 10 jours a permis de régénérer les bio-anodes. Une modification consécutive du potentiel de la bio-anode Ean à une valeur de -0,2 V par rapport à l’électrode de référence ECS a permis d’observer une augmentation de la densité de courant (jours 38 à 65 environ) notamment après chaque alimentation en substrat déchet (30mL à chaque fois). Un incident de déconnection de la bio- anode a eu lieu entre les jours 70 et 80. In the first part of the experiment (from 0 to 38 days), the potential E an of bioanode 3 was maintained at + 0.158 V relative to the reference electrode DHW. The nitrogen bubbling phases (simple arrows in solid lines) were carried out with a flow rate of 50 ml of gas per second for 5 minutes. The first phase of nitrogen bubbling at 10 days made it possible to regenerate the bio-anodes. A subsequent modification of the potential of the bioanode E an to a value of -0.2 V compared to the reference electrode DHW made it possible to observe an increase in the current density (days 38 to approximately 65) in particular after each supply of waste substrate (30mL each time). An incident of disconnection of the bioanode occurred between days 70 and 80.
Au 82e jour une phase de bullage d’azote a été réalisée (50 mL/s pendant 5 min), qui a eu, en combinaison avec ce potentiel négatif à la bio-anode, un impact tout à fait favorable sur la régénération de la bio-anode puisqu’on remarque sur le diagramme de la figure 7 des valeurs de densité de courant supérieures à 15 A/m2, c’est à dire supérieures aux valeurs en début de fonctionnement du dispositif électrochimique.The 82 th day a nitrogen bubbling phase was carried out (50 mL / s for 5 min), which was, in combination with the negative potential to the bio-anode, an impact quite favorable on the regeneration of the bio-anode since on the diagram of FIG. 7 we notice values of current density greater than 15 A / m 2 , that is to say greater than the values at the start of operation of the electrochemical device.
Les flèches en pointillés CV sur cette figure correspondent à des mesures de courant par voltamétrie cyclique. The dotted arrows CV in this figure correspond to current measurements by cyclic voltammetry.
Exemple 3 Example 3
Le dispositif 1 électrochimique selon l’invention schématisé à la figure 8, a été conçu en plus grande échelle pour mimer les conditions industrielles. L’électrolyseur 2 comprend trois compartiments séparés par deux membranes échangeuses d’ions : un compartiment anodique 13 qui enferme deux plaques inox liées (bio-anodes 3), ce compartiment est séparé par une membrane 17 échangeuse de cations compartiment inter-membranaire 18 qui est lui-même séparé par une membrane 19 échangeuse d’anions du compartiment cathodique 15 qui enferme la cathode 5 (cadre d’acier retenant du carbone sous forme granulaire).  The electrochemical device 1 according to the invention shown diagrammatically in FIG. 8 has been designed on a larger scale to mimic industrial conditions. The electrolyser 2 comprises three compartments separated by two ion-exchange membranes: an anode compartment 13 which encloses two linked stainless steel plates (bio-anodes 3), this compartment is separated by a cation exchange membrane 17 inter-membrane compartment 18 which is itself separated by an anion exchange membrane 19 from the cathode compartment 15 which encloses the cathode 5 (steel frame retaining carbon in granular form).
Les volumes de ces trois compartiments sont de 5,25 L, 2 L et 5,25 L respectivement. La taille de chaque électrode (bio-anodes 3 et cathode 5) est de 30X30 cm. Les électrodes sont connectées à un potentiostat (BioLogic®, France, VMP3 non représenté, piloté par le logiciel EC-Lab). Une différence de potentiel de 1 ,1 V est imposée entre les anodes et la cathode.  The volumes of these three compartments are 5.25 L, 2 L and 5.25 L respectively. The size of each electrode (bio-anodes 3 and cathode 5) is 30X30 cm. The electrodes are connected to a potentiostat (BioLogic®, France, VMP3 not shown, controlled by EC-Lab software). A potential difference of 1.1 V is imposed between the anodes and the cathode.
L'électrolyte utilisé à la cathode est le milieu BMP modifié avec 30 g/L de NaHC03. L’électrolyte de l’anode est composé de 12,5 g/L de Na2HP04.7H20, 3 g/L de KH2P04, 0,5 g/L de NaCI, 1 g/L de NH4CI et 30 g/L de NaHC03. L’électrolyte du compartiment inter-menbranaire est composé de 35 g/L de KCI et 32,6 g/L de KH2P04.  The electrolyte used at the cathode is the BMP medium modified with 30 g / L of NaHCO3. The anode electrolyte is composed of 12.5 g / L of Na2HP04.7H20, 3 g / L of KH2P04, 0.5 g / L of NaCI, 1 g / L of NH4CI and 30 g / L of NaHC03 . The electrolyte of the inter-menbranar compartment is composed of 35 g / L of KCI and 32.6 g / L of KH2P04.
Le pH de l'anode est maintenu à 7 par injection automatique d'une solution de H2CO3. The pH of the anode is maintained at 7 by automatic injection of a solution of H2CO3.
Un diffuseur 6 (double, à deux entrées de gaz) est positionné juste au-dessous des deux bio-anodes et permet de générer des bulles 11 de gaz de part et d’autre des surfaces de ces bio-anodes. Une phase de bullage (voir flèche à 14 jours sur le schéma de la figure 9) de 500 ml_/s pendant 5 min (soit un débit de 0,55 mL/s par cm2 de bio-anode), a permis de restaurer une partie de l’activité de ces bio-anodes. Ce débit rapporté à la surface de l’électrode équivaut également à un débit de gaz de 120 m3/h et par m2 de section transversale du socle du compartiment anodique. A diffuser 6 (double, with two gas inlets) is positioned just below the two bio-anodes and makes it possible to generate gas bubbles 11 on either side of the surfaces of these bio-anodes. A bubbling phase (see arrow at 14 days in the diagram in FIG. 9) of 500 ml / s for 5 min (i.e. a flow rate of 0.55 ml / s per cm 2 of bio-anode), made it possible to restore part of the activity of these bio-anodes. This flow rate related to the surface of the electrode is also equivalent to a gas flow rate of 120 m 3 / h and per m 2 of cross section of the base of the anode compartment.
A titre d’illustration, non limitative, dans les exemples ci-dessus les diffuseurs 6 mis en oeuvre comportaient des orifices de 2 mm de diamètre permettant de produire des bulles de taille de quelques millimètres, provoquant de fortes turbulences autour des surfaces des électrodes. Il a d’ailleurs été constaté, dans d’autres essais, avec une bio-anode en matériau souple (tissu de carbone par exemple) que l’efficacité de la régénération des bio-anode était augmentée lorsque ladite bio-anode était en matériau souple. By way of illustration, without limitation, in the examples above, the diffusers 6 used had orifices of 2 mm in diameter enabling bubbles of a few millimeters in size to be produced, causing strong turbulence around the surfaces of the electrodes. It has moreover been observed, in other tests, with a bio-anode made of flexible material (carbon tissue for example) that the efficiency of the regeneration of bio-anodes was increased when said bio-anode was made of material flexible.
Les diffuseurs tels que présentés dans les exemples ci-dessus sont faciles à installer et peuvent être alimentés par une source d’azote extérieure au dispositif électrochimique, mais il peut aussi être envisagé d’utiliser le gaz produit in situ, par exemple présent dans le ciel gazeux des électrodes, ce qui présente l’avantage de perturber le moins possible le fonctionnement de l’électrolyseur. The diffusers as presented in the examples above are easy to install and can be supplied by a source of nitrogen external to the electrochemical device, but it can also be envisaged to use the gas produced in situ, for example present in the gaseous sky of the electrodes, which has the advantage of disturbing the operation of the electrolyser as little as possible.
Ce bullage permet, de manière simple et efficace, effectué pendant le fonctionnement de l’électrolyseur, de contrôler l’épaisseur du biofilm sur l’électrode traitée ou du moins une quantité de biomasse électro-active à sa surface. This bubbling allows, in a simple and effective manner, carried out during the operation of the electrolyser, to control the thickness of the biofilm on the treated electrode or at least an amount of electro-active biomass on its surface.

Claims

REVENDICATIONS
1. Dispositif (1 ) bio-électrochimique comportant au moins une anode (3) et au moins une cathode (5) présentant chacune une surface immergée dans au moins un compartiment renfermant un électrolyte (12A, 12C), et éventuellement une électrode de référence, une différence de potentiel étant appliquée, en fonctionnement, entre l'anode et la cathode ou entre l’anode et l’électrode de référence, au moins l’une des électrodes anode étant une bio-électrode dénommée bio-anode plongeant dans un électrolyte contenant des microorganismes, ladite bio-anode étant recouverte en fonctionnement d’un biofilm, comprenant des microorganismes électro-actifs anodiques, 1. Bioelectrochemical device (1) comprising at least one anode (3) and at least one cathode (5) each having a surface immersed in at least one compartment containing an electrolyte (12A, 12C), and optionally a reference electrode , a potential difference being applied, in operation, between the anode and the cathode or between the anode and the reference electrode, at least one of the anode electrodes being a bio-electrode called a bio-anode immersed in a electrolyte containing microorganisms, said bio-anode being covered in operation with a biofilm, comprising anodic electroactive microorganisms,
caractérisé en ce qu’il comprend un diffuseur (6), connecté à une source de gaz, et disposé dans une zone située au-dessous ou dans la partie inférieure de la bio-anode, le diffuseur (6) présentant des orifices (9) de sortie dudit gaz aptes à générer des bulles (11 ) de gaz balayant la surface de ladite bio-anode et/ou provoquant des turbulences autour de celle-ci, lesdites bulles (1 1 ) étant utilisées pour régénérer ladite bio-anode, pendant le fonctionnement du dispositif électrochimique. characterized in that it comprises a diffuser (6), connected to a gas source, and arranged in an area located below or in the lower part of the bio-anode, the diffuser (6) having orifices (9 ) outlet of said gas capable of generating bubbles (11) of gas sweeping the surface of said bio-anode and / or causing turbulence around it, said bubbles (1 1) being used to regenerate said bio-anode, during the operation of the electrochemical device.
2. Dispositif selon la revendication 1 , caractérisé en ce que le diffuseur est sous la forme d’une rampe comportant une multitude d’orifices (9) de sortie, lesdits orifices étant de préférence orientés vers la surface de la bio-anode et/ou parallèlement à ladite surface. 2. Device according to claim 1, characterized in that the diffuser is in the form of a ramp comprising a multitude of outlet orifices (9), said orifices preferably being oriented towards the surface of the bio-anode and / or parallel to said surface.
3. Dispositif selon la revendication 2, caractérisé en ce que les orifices (9) de sortie du gaz du diffuseur (6) présentent un diamètre supérieur ou égal à 1 mm, de préférence supérieur ou égal à 2 mm, de préférence encore compris entre 2 mm et 6 mm. 3. Device according to claim 2, characterized in that the orifices (9) for the outlet of the gas from the diffuser (6) have a diameter greater than or equal to 1 mm, preferably greater than or equal to 2 mm, more preferably between 2 mm and 6 mm.
4. Dispositif selon l’une quelconque des revendications précédentes, caractérisé en ce que le dispositif comprend au moins deux compartiments : un compartiment anodique et un compartiment cathodique. 4. Device according to any one of the preceding claims, characterized in that the device comprises at least two compartments: an anode compartment and a cathode compartment.
5. Utilisation du dispositif selon l’une quelconque des revendications précédentes, pour une synthèse bio-électrochimique de molécules organiques telles que des acides organiques et/ou des alcools, à partir de déchets organiques. 5. Use of the device according to any one of the preceding claims, for a bioelectrochemical synthesis of organic molecules such as acids organic and / or alcohols, from organic waste.
6. Procédé de régénération d’une bio-anode d’un dispositif (1 ) bio-électrochimique conforme à l’une quelconque des revendications 1 à 4, caractérisé en ce que le procédé comprend une phase de production de bulles (1 1 ) de gaz au-dessous ou dans la partie inférieure de la bio-anode, balayant la surface de ladite bio-anode et/ou créant des turbulences autour de cette dernière, pendant le fonctionnement dudit dispositif. 6. Method for regenerating a bio-anode of a bio-electrochemical device (1) according to any one of claims 1 to 4, characterized in that the method comprises a phase of production of bubbles (1 1) of gas below or in the lower part of the bio-anode, sweeping the surface of said bio-anode and / or creating turbulence around the latter, during the operation of said device.
7. Procédé selon la revendication 6, caractérisé en ce que ledit gaz comprend une teneur en oxygène inférieure ou égale à 30 % en volume, de préférence inférieure à 207. Method according to claim 6, characterized in that said gas comprises an oxygen content less than or equal to 30% by volume, preferably less than 20
% en volume, de préférence encore inférieure à 10 % en volume. % by volume, preferably still less than 10% by volume.
8. Procédé selon l’une quelconque des revendications 6 ou 7, caractérisée en ce que le gaz est dépourvu d’oxygène. 8. Method according to any one of claims 6 or 7, characterized in that the gas is devoid of oxygen.
9. Procédé selon l’une quelconque des revendications 6 à 8, caractérisée en ce que le gaz est choisi parmi : l’azote, un biogaz ou un gaz de fermentation ou un mélange de ceux-ci. 9. Method according to any one of claims 6 to 8, characterized in that the gas is chosen from: nitrogen, a biogas or a fermentation gas or a mixture thereof.
10. Procédé de régénération selon l'une quelconque des revendications 6 à 9, caractérisé en ce que le diffuseur (6) génère un débit de gaz supérieur à 0,01 ml_/s par cm2 de surface d’électrode, de préférence supérieur à 0,1 ml_/s, de préférence encore supérieur à 1 mL/s par cm2 de surface d’électrode, créant un balayage de la surface de la bio-anode avec des bulles de gaz produites avec une vitesse débitante d’au moins 50 m/h, avantageusement pendant une durée d’au moins 1 minute, la vitesse débitante des bulles de gaz étant calculée comme le volume de gaz en m3 par m2 de surface basale intérieure du compartiment électrochimique et par heure. 10. A regeneration method according to any one of claims 6 to 9, characterized in that the diffuser (6) generates a gas flow greater than 0.01 ml_ / s per cm 2 of electrode surface, preferably greater at 0.1 ml_ / s, preferably still greater than 1 ml / s per cm 2 of electrode surface, creating a sweep of the surface of the bio-anode with gas bubbles produced with a flow rate of at least minus 50 m / h, advantageously for a period of at least 1 minute, the delivery speed of the gas bubbles being calculated as the volume of gas in m 3 per m 2 of internal basal surface of the electrochemical compartment and per hour.
1 1. Procédé de régénération d’une bio-anode d’un dispositif électrochimique conforme à la revendication 7, caractérisé en ce qu’il combine une phase de production de bulles (1 1 ) de gaz et la diminution de la différence de potentiel entre la bio-anode et la cathode ou entre la bio-anode et l’électrode de référence, la phase de production des bulles (11 ) de gaz et la diminution de la différence de potentiel étant de préférence simultanées. 1 1. Method for regenerating a bio-anode of an electrochemical device according to claim 7, characterized in that it combines a phase of production of gas bubbles (1 1) and the reduction of the potential difference between the bio-anode and the cathode or between the bio-anode and the reference electrode, the production phase of gas bubbles (11) and the decrease in the potential difference preferably being simultaneous.
12. Procédé selon la revendication 1 1 , caractérisé en ce que la diminution de la différence de potentiel entre la bio-anode (3) et la cathode (5) ou entre la bio-anode et l’électrode de référence est comprise entre 10 et 50 % de la valeur de fonctionnement du dispositif bio-électrochimique. 12. Method according to claim 1 1, characterized in that the decrease in the potential difference between the bio-anode (3) and the cathode (5) or between the bio-anode and the reference electrode is between 10 and 50% of the operating value of the bio-electrochemical device.
13. Procédé selon la revendication 11 , caractérisé en ce que le dispositif bio- électrochimique comprenant une électrode de référence (ECS), le procédé combine une phase de production de bulles (11 ) de gaz et la diminution du potentiel de la bio- anode par rapport à l’électrode de référence, la phase de production des bulles (1 1 ) de gaz et la diminution du potentiel étant de préférence simultanées, le potentiel de la bio- anode (3) par rapport à l’électrode de référence (ECS) étant alors compris entre 0 et - 0,4 V. 13. Method according to claim 11, characterized in that the bioelectrochemical device comprising a reference electrode (DHW), the method combines a phase of production of gas bubbles (11) and the reduction of the potential of the bioanode relative to the reference electrode, the phase of production of the bubbles (1 1) of gas and the decrease in the potential being preferably simultaneous, the potential of the bioanode (3) relative to the reference electrode ( DHW) then being between 0 and - 0.4 V.
EP19787025.6A 2018-09-13 2019-09-12 Regeneration of a bio-electrode of a bio-electrochemical device - device and associated method Withdrawn EP3850126A1 (en)

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FR1858236A FR3085970B1 (en) 2018-09-13 2018-09-13 REGENERATION OF A BIO-ELECTRODE OF A BIO-ELECTROCHEMICAL DEVICE - DEVICE AND ASSOCIATED METHOD
PCT/FR2019/052107 WO2020053526A1 (en) 2018-09-13 2019-09-12 Regeneration of a bio-electrode of a bio-electrochemical device - device and associated method

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JPS5924241B2 (en) 1978-08-11 1984-06-08 マツダ株式会社 Combination of side housing and side seal in rotary piston engine
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