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BR-112021009630-B1 - Electrochemical filter membrane, electrochemical device for purifying a fluid, and processes for manufacturing a filter membrane.

BR112021009630B1BR 112021009630 B1BR112021009630 B1BR 112021009630B1BR-112021009630-B1

Abstract

Electrochemical device for purifying a fluid, in particular wastewater or sludge, comprising an electrochemical filter membrane, said membrane comprising: - a metallic support, in particular chosen from a screen, a fabric or an open-pore foam, said support being permeable to said fluid, - a coating layer of said support comprising or preferably consisting of a titanium oxide of the general formula TiOx, with x between 1.5 and 1.9.

Inventors

  • Stéphane Raffy
  • YVES MARCEL LÉON BOUSSANT-ROUX
  • Corinne SALLES
  • Brice Aubert

Assignees

  • SAINT-GOBAIN CENTRE DE RECHERCHES ET D'ETUDES EUROPEEN

Dates

Publication Date
20260310
Application Date
20191205
Priority Date
20181207

Claims (15)

  1. 1. Electrochemical filter membrane for the purification of a fluid, characterized in that it comprises: - a metallic support chosen from an open-pore foam, said support being permeable to said fluid, said support having a porosity between 10% and 90% and an average pore diameter, by volume, greater than 70 micrometers and up to 10 millimeters; - a coating layer of said support comprising or preferably consisting of a titanium oxide of the general formula TiOx, with x between 1.5 and 1.9.
  2. 2. An electrochemical device characterized in that it is for purifying wastewater or sludge by oxidizing the organic compounds contained in said fluid, comprising an electrochemical filter membrane as defined in claim 1.
  3. 3. Device according to claim 2, characterized in that the membrane is configured to act as an electrode, in particular, an anode, allowing the partial or complete degradation of said organic compounds.
  4. 4. Device according to claim 2 or 3, characterized in that the support comprises or consists of a metal chosen from titanium, stainless steel, preferably titanium.
  5. 5. Device according to any one of claims 2 to 4, characterized in that the support has a porosity between 20% and 80%.
  6. 6. Device according to any one of claims 2 to 5, characterized in that the support has an average pore diameter smaller than 50 micrometers.
  7. 7. Device according to any one of claims 2 to 5, characterized in that the support has an average pore diameter greater than 100 micrometers.
  8. 8. Device according to any one of claims 2 to 7, characterized in that the support is in the form of a plate or a tube.
  9. 9. Device according to any one of claims 2 to 8, characterized in that the material constituting the coating layer comprises more than 90% by weight, in total, of Magneli phases selected from Ti4O7, Ti5O9, Ti6O11 or a mixture of at least two of these phases.
  10. 10. Device according to any one of claims 2 to 9, characterized in that it also comprises means for introducing the fluid to be purified, means for circulating the fluid, for possible pressurization thereof, means for energizing the support and means for recovering the purified fluid.
  11. 11. Process for manufacturing a filter membrane as defined in claim 1, characterized in that the support comprises or consists of titanium, and in that the coating layer is obtained by oxidation through anodizing or chemical treatment of the support so as to obtain a layer comprising TiO2 and then reduction of said TiO2 to provide a titanium oxide of the general formula TiOx, with x between 1.5 and 1.9.
  12. 12. Process for manufacturing a filter membrane as defined in claim 1, characterized in that, according to a first step, the metallic substrate is brought into contact with a sol-gel type solution comprising titanium, for example, a solution of a tetravalent titanium alkoxide in an alcoholic or aqueous medium, said solution optionally including an additional carbon source such as an additional organic compound or carbon black, then a second step of heat treatment of the sol-gel layer so as to obtain a TiOx coating layer, at a temperature between 500°C but not exceeding 1430°C at atmospheric pressure, under an inert or reducing atmosphere.
  13. 13. Process for manufacturing a filter membrane as defined in claim 1, characterized in that the deposition of the coating layer on the support is carried out by impregnation starting from an aqueous suspension, or a suspension of another solvent, of a TiOx powder, followed by heat treatment at a temperature between 500°C but not exceeding 1430°C at atmospheric pressure, under an inert or reducing atmosphere.
  14. 14. Process for manufacturing a filter membrane as defined in claim 1, characterized in that the deposition of the coating layer on the support is carried out by impregnation starting from an aqueous suspension, or a suspension of another solvent, of a mixture of titanium oxide powder TiO2, preferably in the form of anatase, supplemented by an additional carbon source such as an additional organic compound or carbon black, the TiOx layer being obtained by reducing said TiO2 layer through a subsequent heat treatment at a temperature between 800°C but not exceeding 1430°C at atmospheric pressure, under an inert or reducing atmosphere.
  15. 15. Process for manufacturing a filter membrane as defined in claim 1, characterized in that the deposition of the coating layer on the metallic support is carried out by thermal spraying, in particular plasma spraying, of TiOx particles onto said support.

Description

[0001] The invention relates to an electrochemical device, in particular useful for the treatment of fluids and particularly liquids, in particular the purification of wastewater comprising organic compounds. [0002] The difficulties in managing effluents and their content of pollutants, and in particular organic pollutants, are currently a major challenge for our society. Until recently, some of these products were discharged into wastewater treatment effluents without being specifically treated. Current legislation is regulating such discharges in an increasingly strict manner. [0003] In particular, many organic compounds contained in industrial effluents are toxic to the environment. The most common process for treating organic discharges is currently the biological route. However, the microorganisms used are not suitable in some cases for biorefractory compounds or toxic compounds such as pharmaceuticals. Among the alternative physicochemical techniques, electrochemistry is today a very promising way to carry out a pre-treatment that precedes, for example, the biological process or even to ultimately degrade organic products to carbon dioxide and water. Advantageously, an electrochemical process does not require any addition of oxidant or other chemical compound and therefore proves to be particularly clean. [0004] In order to improve the treatment of effluents loaded with biorefractory pollutants (e.g., medicines such as antibiotics, anti-inflammatories, or even textile dyes or pharmaceuticals, etc.) not removed by conventional methods, it is possible to use membrane systems that must have two roles: on the one hand, allow the retention of the organic compounds to be treated and, on the other hand, ensure their electrochemical degradation. The components used in such membrane systems must, therefore, have adequate porosity in relation to the size of the pollutant particles, but make it possible to allow the treated effluent to pass through while decreasing its speed, thus prolonging the contact of the compounds to be degraded with the membrane, without generating a very large pressure drop. They must also be electroactive, that is, they allow the degradation of pollutant compounds into non-toxic material or carbon dioxide through electrochemistry. [0005] Therefore, there is a current need to develop membranes that act as electrodes comprising or consisting of a stable anode and/or cathode material, preferably an anode material, making it possible to achieve at least partial or indeed complete degradation of the molecular structure of organic products. However, the simple transfer of electrons at the interface between the membrane and the fluid to be purified does not seem to make degradation possible on its own. Specifically, it is necessary to generate powerful oxidants such as hydroxyl radicals on the membrane surface. The choice of the material constituting the membrane used as an electrode, in particular as an anode, is therefore an essential element of the treatment process. Furthermore, the materials that can be industrially predicted must have good chemical resistance in acidic and caustic media, but also a long service life. [0006] For this purpose, electrodes were developed in the 1990s for the removal of organic compounds in wastewater through oxidative electrolysis, in particular, based on boron-doped diamond (BDD) as indicated in the publication “Electrochemical synthesis on boron-doped-diamond”, Waldvogel et al.; Electrochimica Acta 82 (2012) 434-443). This compound has remarkable effectiveness, as it allows the generation of highly oxidizing species, such as *OH radicals, useful and highly effective for the degradation of organic compounds. BDD also has high chemical inertness in acidic and basic media. This is, therefore, an expensive material that is difficult to use on large surface areas and/or whose adhesion to the substrate is not always optimal. [0007] Furthermore, porous products are those based on titanium suboxides, in particular consisting of or comprising materials based on the Magneli phase of Ti4O7, Ti5O9 or even Ti6O11 and very particularly based on Ti5O9. According to a first aspect thereof, the present invention proposes to use such a material, which does not have the disadvantages of BDD, as one of the constituents of the electrode, in particular, the anode. Patent Application WO2018/115749A1 describes a porous product entirely based on titanium suboxide TiOx and the process for its manufacture. [0008] The article “Electrochemical impedance spectroscopy study of membrane fouling and electrochemical regeneration at a sub-stoichiometric TiO2 reactive electrochemical membrane” published in the Journal of Membrane Science, 510-523, (2016) describes the use of a membrane consisting of Ti4O7 and Ti6O11 having a porosity of 28.2% with an average pore size of 3.27 μm and also a bimodal pore distribution. [0009] The article “Development and Characterization of Ultrafiltration TiO2