Method for recovering catalyst material from a water electrolysis membrane electrode assembly and recycling system for carrying out the method

Abstract

A method is specified for recovering catalyst material (5, 7) from a membrane electrode assembly (1), wherein a membrane electrode assembly (1) is provided. The carrier material of the membrane electrode assembly (1) comprises a membrane (3), in particular a polymer membrane, on which an electrode layer (9) made of an electrode material containing a metallic catalyst material (5, 7) is applied. Electrode material is abrasively removed from the membrane (3) and separated to give a separation material (31), and metallic catalyst material (5, 7) is recovered from the separation material (31). Further specified is a recycling system (35) configured for carrying out the method.

Description

[0001] Description

[0002] Process for the recovery of catalyst material from a membrane electrode assembly of water electrolysis and recycling plant for carrying out the process

[0003] The invention relates to a process for recovering catalyst material from a membrane electrode assembly used in water electrolysis. A used membrane electrode assembly containing a membrane coated with a metallic catalyst material is provided. The invention further relates to a corresponding recycling plant equipped to carry out the process.

[0004] In the context of the present invention, a membrane electrode assembly (MEA) is defined and understood to include catalyst-coated membranes (CCMs), catalyst-coated diaphragms (CCDs), and catalyst-coated substrates (CCSs). These are used particularly in water electrolysis. The term "coated membrane" of a membrane electrode assembly is intended to encompass any of the aforementioned embodiments, meaning, in particular, catalyst-coated diaphragms (CCDs) and catalyst-coated substrates (CCSs).

[0005] Hydrogen can be obtained from deionized water by electrolysis. The electrolysis can be carried out, for example, as polymer electrolyte membrane electrolysis (PEM electrolysis), in which the reaction spaces for the anode reaction (I) and the cathode reaction (II) are separated by a proton-conducting membrane, the polymer electrolyte membrane, also known as a proton exchange membrane.

[0006] Anode reaction 2 H20 — > 4 H+ + 02+ 4 e~ ( I )

[0007] Cathode reaction H+ + 2 e~ — > H2(II) The separation of water into its chemical components hydrogen and oxygen can be carried out using suitable electrolysis cells. These can be designed as so-called polymer electrolyte membrane electrolysis cells. In such an electrolysis cell, a membrane is generally provided which has a respective catalyst layer on surfaces facing away from one another. The catalyst layers are generally bordered by respective gas diffusion layers, which in turn are bordered by respective electrically conductive contact plates, occasionally also called bipolar plates, which serve, among other things, for electrical contact. The contact plates or the bipolar plates are preferably also designed in such a way that they can enable the necessary material transport during electrolysis in the electrolysis cell during normal operation.For this purpose, appropriate channels can be provided for supplying a suitable electrolyte and for removing the reaction products of the electrolysis, namely a hydrogen gas and an oxygen gas. The gas diffusion layer generally provides electrical conductivity to electrically couple the contact plates and the catalyst layers. This allows the desired electrochemical reaction to be realized in the region of the catalyst layers.

[0008] The polymer electrolyte membrane of an electrolysis cell, for example, can usually be made of a polymer, particularly an ionomer. Perfluorosulfonic acid-containing polymers, marketed, for example, under the name Nafion™, are widely used.

[0009] Catalyst materials are usually incorporated or applied to the polymer electrolyte membrane in order to carry out water electrolysis more efficiently. A PEM coated with catalyst material is also referred to as a catalyst coated membrane, abbreviated CCM. Possible catalyst materials are metals, such as iridium, platinum, ruthenium, palladium, in the form of pure metals or metal compounds. In addition to CCMs, catalyst coated diaphragms (CCD) and catalyst coated substrates (CCSs) are also defined as MEAs as membrane electrode assemblies (MEAs), and such embodiments of an MEA with a catalyst layer applied to a membrane are intended to be encompassed by the invention.

[0010] Similar polymer electrolyte membranes and catalyst materials are used in fuel cells. Unlike catalyst materials used in fuel cells, the catalyst materials used in water electrolysis often contain iridium, as iridium is preferentially used to catalyze the oxygen evolution reaction.

[0011] For example, after the end of their service life or in the event of faulty manufacturing, reprocessing (recycling) of the polymer electrolyte membranes including catalyst materials to recover the precious metals and membrane polymers is desirable for cost and environmental reasons, among others.

[0012] Previous recycling processes involve a two-stage combustion process at temperatures between 850 and 1000 °C, in which the fluoropolymers are burned, releasing HF and CO2. Due to the aggressiveness of HF, special reactor linings and an extensive downstream gas scrubbing system are required. The resulting ash is usually mixed with other charges or ore concentrates and fed into a multi-stage refining process to separate the precious metals. Such a refining process may include, among other things, dissolving in aqua regia, i.e., an HCl / HNO3 mixture in a ratio of approximately 3:1.

[0013] However, if metallic iridium catalysts (IrO) are used, the possibility of dissolving in aqua regia is eliminated, since metallic iridium is insoluble. The subsequent separation steps for precious metal separation therefore include the Na2O2 oxidation melt process to convert metallic iridium into soluble IrCu. This process yields only low conversions and must be repeated several times.

[0014] A significant disadvantage of the established process chain is the loss of the catalysts used, as these are completely dissolved and must be reprecipitated or pulverized. Due to the high number of process steps, side streams arise that represent potential loss paths, as they are difficult to integrate into the main process stream.

[0015] Furthermore, the membrane polymers cannot be recovered because they are burned during the initial incineration process. The entire recycling process is also energy- and time-consuming. Furthermore, the use of numerous chemicals produces a number of toxic substances that must be disposed of separately and pose a danger to the recycling personnel as well as the environment.

[0016] An alternative recycling process is known from US Pat. No. 7,255,798 B2, in which the CCM to be recycled is subjected to a treatment at elevated pressure and elevated temperature in a water-solvent mixture. Solvents that can be used are methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, 2-methoxyethanol, 2-ethoxyethanol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dioxane, acetonitrile, or mixtures of the solvents mentioned with a mass fraction of between 10% and 80%.

[0017] After this treatment, the catalyst material and the polymer material can be separated and further processed. For example, the polymer material can be used to create a membrane, and the catalyst material can be deposited on this membrane.

[0018] A disadvantage of this process is the use of mixtures of water and an organic solvent, as this complicates the purification of the recycled polymer and catalyst material. Furthermore, the organic solvents used are hazardous substances, thus posing an increased risk to the personnel involved in recycling and to the environment, particularly given the process conditions of increased pressure and high temperature.

[0019] Against this background, the object of the invention is to provide a method for recovering catalyst material from a membrane electrode arrangement which enables a particularly simple and cost-effective recovery of catalyst material while at the same time achieving a high recovery yield.

[0020] The object is achieved according to the invention by a method for recovering catalyst material from a membrane electrode arrangement, in which a membrane electrode arrangement is provided, wherein the membrane electrode arrangement has a membrane, in particular a polymer membrane, as carrier material, to which an electrode layer made of an electrode material containing a metallic catalyst material is applied, wherein electrode material is abrasively removed from the polymer membrane and separated, so that a separate material is obtained, wherein metallic catalyst material is recovered from the separate material.

[0021] The invention is based on the general fundamental aim that recycling makes a significant contribution to protecting the environment. Recycling means sustainability, because raw material resources do not last forever. And recycling is hard cash, because the metallic catalyst materials are often precious metals that are far too valuable not to be recycled. On the other hand, with the large-scale use of electrolyzers for water electrolysis, a rapidly increasing demand for membrane electrode assemblies is to be expected, so that the requirements for the economic viability of known recycling processes are increasingly being placed in terms of cost and efficiency aspects.

[0022] Although numerous laboratory-scale processing and separation processes are described in the scientific literature, they are too complex and energy-intensive to be implemented economically and on a large scale, and consequently very costly. Therefore, the need for a simple and cost-effective recovery of metallic catalyst material has been recognized by this invention.

[0023] The application of the method of the invention is not limited to the treatment of homogeneous metallic catalyst materials or layers within the electrode layer, but can also remove multi-component coatings and later separate them further in further steps in order to obtain metallic catalyst material. For reuse of the catalyst, further processing steps are to be expected depending on the composition of the separation, based on the respective material composition and the structure of the abrasively removed electrode layer. Accordingly, metallic catalyst material is not exclusively made of one metal, but can also comprise other components. In this sense, metallic catalyst material is understood to mean both a purely metallic and a metal-containing catalyst material.

[0024] The process of the invention makes it possible to recover metallic catalyst material, particularly valuable precious metals, very efficiently. The catalyst material on the membrane of a membrane electrode assembly can, for example, comprise one or more of the following substances on the anode side: nickel-aluminum, nickel-zinc, cobalt-aluminum, cobalt-iron, nickel-iron, nickel-iron-vanadium, nickel-cobalt, nickel-molybdenum, nickel-iron double-layered hydroxide, nickel-iron-cobalt, iridium, ruthenium oxide, nickel hydroxide, nickel oxide, nickel. Membrane electrode assemblies (MEAs) in the form of catalyst coated membranes (CCMs) are the core component of every polymer exchange membrane water electrolyzer (PEMWE) and polymer exchange membrane fuel cells (PEMFC).The invention is not limited to application in membrane electrode assemblies for PEM water electrolysis. Rather, such membrane electrode assemblies with a similar basic structure are used in electrolysis cells, such as catalyst-coated membranes (CCM), catalyst-coated diaphragms (CCDs), or catalyst-coated substrates (CCSs). Thus, membrane electrode assemblies for various water electrolysis technologies can be recycled using the method. In addition to PEM water electrolysis (PEMWE), the invention particularly encompasses the treatment of a membrane electrode assembly, an anion-exchange membrane water electrolysis (AEMWE), and alkaline water electrolysis.

[0025] In the MEA manufacturing process, membranes are coated with electrodes in an almost irreversible manner. The membranes in industrial products, for example, currently consist exclusively of per- and polyfluorinated alkyl substances (PEAs). MEAs, especially in the electrodes, contain elements of high strategic and economic value, such as iridium. MEAs have a limited lifetime and are therefore a wear component. Recycling of the high-quality elements contained in the coatings (electrodes) is therefore crucial to the economic success of these technologies.

[0026] For the first time, the invention proposes abrasive material removal for the recycling of a membrane electrode assembly in order to specifically and locally detach the electrode layer from the membrane, in particular a polymer membrane, and to separate it from the carrier material. The entire surface can be abraded in order to completely remove the electrode layer and detach it from the membrane. Initial tests have surprisingly shown that this mechanical removal process for the electrode layer is very efficient for recovering the valuable catalyst components with a high recovery rate and significantly reduced separation effort. The process can advantageously be carried out at ambient temperature and under normal pressure conditions and is practically non-destructive to the membrane polymer.The resulting separation contains practically only the electrode material, which is loaded with valuable catalyst material, such as iridium, in high concentrations. Depending on the abrasion process and the structure and bonding of the electrode layer, an abrasive working fluid or a solvent can be used to specifically increase the abrasion efficiency and to remove the electrode layer from the membrane more easily and thoroughly. In this case, the working fluid or the solvent can be contained in the separation because wet abrasion is carried out. Dry abrasion is possible without the optional use of a working fluid or a solvent, so that electrode material is obtained in granular form, i.e. in fine particles or powder form, and is separated from the membrane.

[0027] This process is a deliberate departure from the common and frequently described multi-stage and complex separation processes, which involve, among other things, mechanical comminution and thermal treatment, which is particularly problematic when a PFAS-based membrane polymer is used as the carrier material for the membrane electrode assembly and also makes further processing very complex.

[0028] Membrane polymers based on PEAS in particular make conventional recycling methods such as the recovery of valuable materials by incineration followed by refining of the ash a technological challenge. Combustion produces hydrogen fluoride (HF). Due to the aggressive properties of HF, special combustion chamber / pipe linings and an extensive gas scrubbing system are required. After incineration, the resulting ash is usually mixed with other batches or ore concentrates and subjected to a refining process to separate the precious metals it contains. Membrane electrode assemblies made of PEAS contain a fluorine content of approximately 4 wt%. According to the 17th Federal Immission Control Ordinance (17th BImSchV), waste with a halogen content greater than 1% must be incinerated at a minimum incineration temperature of 1,100°C.This means that they cannot be disposed of in conventional incineration plants, where combustion temperatures are between 850 and 1,100 °C.

[0029] In the described process, as well as in other experimental, e.g., solvent-based recycling concepts, the valuable materials locally concentrated in the electrodes are homogenized with the entire MEA or other waste from the batch, for example, by incineration or chemical dissolution. This significantly reduces the concentration of the valuable materials, increases the associated technical expenditure for recovery, and adversely reduces recovery yields. The process of the invention described here is therefore superior to previously common processes in many respects.

[0030] The invention comprises a process for separating the electrode layer containing the metallic catalyst material and the support material of a membrane electrode arrangement by using abrasive removal and optionally adding a solvent. In this process, advantageously, no homogenization of components rich in valuable materials and components poor in valuable materials takes place. Furthermore, depending on the choice of solvent, damage to the support material, in particular the membrane, can be avoided. The process is therefore efficient and gentle on the membrane. The electrode layer can be removed and separated without damaging the support material, and valuable materials such as iridium can be recovered from the separation with a high recycling rate and purity, without the need to incinerate the membrane, in particular, for example, a polymer membrane containing PFAS.The process is applicable for the recovery of valuable metallic materials from both the anode and cathode electrodes. Metallic or metal-containing catalyst material on the membrane can, for example, contain one or more of the following materials on the cathode side: nickel, nickel-molybdenum on carbon black, nickel-molybdenum, nickel-platinum, platinum, nickel on carbon black, nickel phosphate, and nickel-vanadium.

[0031] In a particularly preferred embodiment of the method, an abrasive agent is applied to the electrode layer in such a way that a material-removing effect is brought about by mechanical action of the abrasive agent on the electrode layer, whereby electrode material is removed from the carrier material.

[0032] The abrasive is used to create or enhance the desired abrasive effect during surface treatment. The choice of abrasive is flexible and can be specifically adapted to the electrode layer to be removed and the membrane substrate material supporting the electrode layer, especially the polymer membrane.

[0033] In a preferred embodiment of the method, the abrasive means comprises a brush which is guided on the electrode layer under a predetermined contact pressure, whereby a relative movement is brought about between the brush fibres and the electrode material.

[0034] The mechanism is such that the separation occurs by abrasion of the coating. In the case of a brush as the abrasive, the abrasion is caused by the build-up of a required contact pressure of the brush on the medium to be separated, i.e. on the surface of the electrode layer, and the build-up of a relative speed between the brush fibers and the separating medium. The relative speed and the contact pressure can be optimized by process technology. A contact pressure in the range of 1 N / cm 2 up to 50 cm 2can be set more typically, whereby the exact value can be adapted to the surface condition and the electrode material and is monitored and regulated by a pressure sensor. The contact pressure of the brush can also be adjusted and varied over time during the abrasion process in order to achieve the desired material removal and removal of the electrode material for the membrane without causing damage. A solvent can be added to increase the abrasion effect or to adjust it specifically. It is also possible to use several brushes. The technical design of the brushes is diverse. Brushes are understood here to be any aid or device consisting of a base body to which a brush trim (fibers) is attached. The material and shape are considered to be the design properties of the base body. The brush trim varies in terms of material, fiber diameter, trim length and trim density.The technical design of the brush can be realized using various brush types. These include round brushes, roller brushes, strip brushes and disc brushes. In the simplest case, examples of applications for these brush types are even manual brushes or toothbrushes. Rotary, vibrating and ultrasonic brushes, which can also be handled manually, have proven particularly effective for small-format applications or small series. Strip brushes and roller brushes are particularly suitable for larger technical applications. Suitable materials for the base body are wood, metal or plastic. Natural fibres, synthetic fibres or wires are suitable for the brush trim. Both a brush and a grinding and / or smoothing function for abrasive surface treatment can be implemented in the brush or the brush arrangement.

[0035] In a particularly preferred embodiment of the method, ultrasound is generated so that the electrode material is excited to mechanical vibrations and the material-removing effect is enhanced. Preferably, an ultrasonic frequency of 20 kHz to 400 kHz, in particular of 35 kHz to 200 kHz, is set in the method.

[0036] The abrasive effect can be significantly enhanced by the incidence of ultrasound on the electrode layer in conjunction with the mechanical removal by the abrasive, particularly the brush. Piezoelectric transducers, for example, are used as ultrasound transmitters.

[0037] Piezoelectric quartz or ceramic oscillators can advantageously be used for this purpose. An alternating voltage with their natural resonant frequency or a harmonic thereof is applied to these. The oscillations are then transmitted, for example, via a coupling element to the base body of the brush. In the case of the abrasive, the brush can also advantageously be implemented as an integrated ultrasonic brush, in which a sound generator, base body and brush bristles are integrated to form an ultrasonic brush. In principle, it is also possible to transmit the ultrasonic waves via the bottom of an ultrasonic bath into a liquid, e.g., water, in which the membrane electrode unit is immersed.

[0038] For example, even a low ultrasonic frequency of approximately 20 kHz to 40 kHz may be sufficient to cause the electrode material to vibrate sufficiently, thereby producing an additional abrasive effect.

[0039] Ultrasonic frequencies from 20 kHz to 400 kHz are advantageously used. Low frequencies around 20 kHz create bubbles of larger diameter with powerful pressure surges in an aqueous environment. In contrast, higher frequencies around 35 kHz are better suited to the intensive and gentle cleaning and abrasion of surfaces. It has been shown that a currently advantageous frequency for particles of the electrode material with a diameter greater than 1 pm is around 200 kHz. The frequency range above 400 kHz up to 1-2 MHz is also referred to in the specialist literature as megasound. Particles with a diameter of less than 1 pm are optimally removed here. In general, in addition to sound-induced vibration, rotation or a combination of vibration and rotation is possible when using the brush, which is carried out in repetitive, circular movements.

[0040] In a particularly preferred embodiment of the method, a powdered blasting agent with a carrier gas is jetted onto the surface of the electrode layer under a jet pressure.

[0041] This means that abrasive particles in the form of a powdered blasting agent can be transported by the blasting pressure and impact the surface of the membrane electrode arrangement which is to be cleaned of electrode material at a high speed or impulse, and the electrode material can be abrasively removed by the impulse and force transfer. Compressed air or an inert gas, preferably pure nitrogen, can be used as a carrier gas. Abrasive particles in fine granular form or as powder, for example sand, glass beads, corundum, nutshells or plastic granules or mixtures thereof, are advantageously used as a blasting agent in the carrier gas. This makes it possible to use particle blasting technology similar to sandblasting or combinations thereof as an abrasive agent in addition to brush technology to provide the required mechanical removal effect.

[0042] Preferably, the blasting medium in the process comprises plastic granules. It is also possible for the blasting medium to consist essentially of fine-granular plastic powder with a small particle size of a few 10 pm up to around 100 pm. The advantage of a plastic-based blasting medium arises from the easy separation of the plastic particles from the obtained separation after use, for example by electrostatically separating the plastic particles from the separation. It is also conceivable in a sufficiently aqueous environment that separation is achieved solely by the plastic particles floating to the top of the water and can then be easily separated or sieved out from the surface of the liquid.

[0043] Alternatively, in a compressed air blasting process, solid carbon dioxide, so-called dry ice, can be added to the blasting medium.

[0044] In a particularly preferred embodiment of the method, a solvent is injected during the abrasive removal, in particular 2-propanol or acetone, so that the abrasive effect on the electrode material is increased.

[0045] In combination with the brush, the targeted addition of solvent particularly wets the brush fibers, thereby increasing the abrasive effect. This is achieved by the fact that the electrode layer detaches more easily from the carrier material through the locally initiated dissolution process of the structural components of the electrode layer, and the components can also be more gently abraded from the membrane.

[0046] In a preferred embodiment of the process, the solvent is selected from the group of alcohols, ethers, ketones, alkanes or aromatic hydrocarbons.

[0047] This choice has resulted in no significant damage to the membrane. Various options have been proposed for the technical design of the solvent additives, with the selection being able to be adapted to the respective composition of the membrane electrode arrangement according to various criteria. The optional solvent selection depends on the components of the electrode coating and the requirements for the integrity of the membrane support material after separation, i.e., possible damage caused by the use of the solvent during the abrasive treatment. For example, 2-propanol has been shown to be particularly suitable for tested PFAS-based support materials, with no damage occurring that was visible or measurable using Fourier transform infrared spectrometry (FTIR) or X-ray diffraction (XRD).Propan-2-one (acetone), on the other hand, tends to attack the carrier material more strongly, but increases the abrasive effect more than, for example, 2-propanol. Other potential solvents include alcohols (ethanol), carboxylic acid esters (ethyl acetate), ethers (diethyl ether), ketones (propan-2-one), alkanes (n-hexane), aromatic hydrocarbons (toluene), halogenated aliphatic hydrocarbons (carbon tetrachloride), and glycol ethers (ethylene glycol monoethyl ether).

[0048] In a particularly preferred embodiment of the method, hydration of the carrier material is carried out so that softening of the membrane, in particular the polymer membrane, is effected.

[0049] Hydration has proven very beneficial for preparing the membrane electrode assembly for abrasive treatment, as it promotes the abrasive removal of the electrode layer. It is therefore advisable to first hydrate the membrane electrode assembly to be processed as completely as possible in a preparatory process step. One possible approach is to place or soak the membrane electrode assembly in a water bath for about two hours. Complete hydration softens the MEA. This significantly increases the abrasive effect on the electrode layer. Furthermore, the water reduces the penetration of non-polar solvents into the membrane or the carrier material.On an industrial, serial scale with a variety of membrane electrode assemblies, hydration can be achieved in a continuous recycling process using spray humidification, with an appropriate residence time in the hydration chamber equipped with a spray humidification device. It is beneficial for complete and rapid hydration if the water used for hydration is tempered, for example, at a temperature between 40°C and 80°C, typically around 60°C. This promotes rapid and complete softening and swelling of the membrane and appropriate preparation for the abrasion process.

[0050] In a preferred embodiment of the process, the obtained separation is removed from the surface of the membrane using a cleaning agent, in particular water, and collected, with metallic catalyst material subsequently being recovered from the collected separation.

[0051] By adding water, the sediment can be easily rinsed or washed off the membrane surface. The sediment thus collected already contains the metallic catalyst materials in a comparatively high concentration. These valuable metallic components can then be recovered from the sediment in subsequent steps using relatively simple separation steps, particularly iridium or other functional metals of the electrode layer in high purity.

[0052] It is also preferred in the process that the membrane freed from the electrode layer is recycled, whereby carrier material is recovered.

[0053] Once the membrane has been stripped of its electrode layer, the carrier material can now be subjected to further recycling steps, including non-thermal recycling. The carrier material recovered and processed in this way can be used for a membrane, a membrane electrode assembly, or for other purposes.

[0054] A further aspect of the invention relates to a recycling plant for carrying out the method with a separation device comprising a separation chamber in which a brush unit and / or a jet unit is arranged and which is designed to receive and treat a membrane electrode unit, so that during operation a membrane electrode unit can be introduced into the separation chamber and electrode material can be abrasively removed and separated from the membrane of the membrane electrode unit.

[0055] This advantageously enables a largely automated or controlled supply and transport of a membrane electrode arrangement on an industrial scale in order to enable continuous advance and abrasive treatment in the recycling plant. It is possible for both a brush unit and a jet unit to be accommodated in the same separation chamber. Alternatively, it is possible for a respective separation chamber to be provided, each of which accommodates a brush unit or a jet unit. In this way, the recycling plant is particularly advantageously set up for carrying out different abrasive processes, which can advantageously be combined with one another and adapted to the specific properties of the membrane electrode arrangement. This makes it possible to achieve a particularly good recycling result, i.e.the efficient abrasive removal and separation of the electrode layer containing the electrode material from the membrane polymer.

[0056] In a preferred embodiment of the recycling plant, the separation chamber has a solvent injector and the brush unit is equipped with an ultrasonic brush.

[0057] For this purpose, a piezoacoustic transducer or a piezo actuator can be provided as a sound transducer to generate the ultrasonic waves, with a coupling or transmission element in the brush head. It is also possible for the piezoacoustic transducer to be integrated into the brush.

[0058] In a particularly preferred embodiment of the recycling plant, the blasting unit in the separation chamber comprises a particle blasting unit, so that during operation, the surface of the electrode layer can be subjected to a powdered, abrasive blasting agent with a carrier gas under pressure. In a further preferred embodiment of the recycling plant, a separation comb is arranged downstream of the separation chamber, wherein the separation comb is configured to remove the separated material from the membrane, in particular the polymer membrane, and to discharge it.

[0059] In particular, roller brushes are used in the separation chamber to wipe or brush the separation off the surface of the membrane. A device for solid-liquid phase separation is also integrated into the separation comb, so that the separation from the high solvent content can be achieved in the separation chamber. After phase separation, the separation is still present as a suspension, i.e. as a heterogeneous mixture of the liquid and finely distributed solids, in particular the abrasively removed electrode material in the form of particles. A suspension is a coarsely dispersed dispersion and tends towards sedimentation and phase separation. The solids are suspended in the liquid phase.

[0060] In a particularly preferred embodiment of the recycling plant, a separation device is arranged downstream of the separating comb so that used solvent can be collected and recycled.

[0061] The term "separation device" is understood here to mean a technical facility in the recycling plant in which different process engineering functions can be implemented and integrated, which can in particular be applied successively in at least two process steps. In a first process engineering step, a solid-liquid separation of electrode material and solvent is to be carried out. In terms of equipment, this can be implemented in the recycling plant using a sedimenter, a centrifuge, a flotation apparatus or a permeation apparatus. In a second process engineering step, a liquid-liquid separation of water and solvent is to be carried out. In terms of equipment, a rectification column, an adsorber or a permeation apparatus is preferably provided for this purpose.The separation device is therefore equipped with a solid-liquid separation device for separating the electrode material and a liquid-liquid separation device for recovering used solvent.

[0062] In a preferred embodiment of the recycling plant, the separation device is equipped with a first separation device and with a second separation device connected downstream of the first separation device, wherein the first separation device forms a solid-liquid separation device and the second separation device forms a liquid-liquid separation device.

[0063] Thus, a two-stage separation process is implemented by at least a two-stage separation device in the recycling plant.

[0064] The solvent fed from a storage tank into the separation chamber via the solvent injector can thus be reused. After optional filtering of suspended particles and purification of the solvent, the solvent can be fed back to the storage tank and reused as needed. It is also possible for regenerated solvent to be returned directly to the separation chamber via the injector and reused to support the abrasion process. The solvent can also be very advantageously recycled, with only minimal solvent consumption.

[0065] In a particularly preferred embodiment of the recycling plant, a hydration chamber is provided which is connected upstream of the separation chamber in such a way that, during operation in the hydration chamber, the membrane electrode unit can be prepared for an abrasive treatment in the separation chamber, wherein swelling and softening of the membrane can be brought about in the hydration chamber.

[0066] For this purpose, the hydration chamber is advantageously equipped with a device for spray humidification with water, which has an appropriate number of nozzles, so that uniform and intensive wetting and complete hydration of the membrane can be achieved in an industrial continuous process. In the simplest case, a water bath can also be provided so that immersion hydration can be achieved by completely immersing the membrane electrode assembly in a water container, thus appropriately preparing and pretreating the surface for the abrasive treatment. Abrasive treatment and detachment of the electrode material from the membrane are advantageously greatly promoted by the hydration.

[0067] Further advantages of the recycling plant according to the invention arise analogously from the advantages of the method according to the invention and can also be transferred in reverse.

[0068] The exemplary embodiments explained below are preferred embodiments of the invention. The features and combinations of features specified above in the description, as well as the features and combinations of features mentioned in the following description of exemplary embodiments and / or shown alone in the figures, can be used not only in the respective combination specified, but also in other combinations. Thus, embodiments are also encompassed by the invention or are to be regarded as disclosed which are not explicitly shown and explained in the figures, but which arise from and can be produced by separate combinations of features from the explained embodiments.The features, functions, and / or effects illustrated by the exemplary embodiments may, in and of themselves, represent individual features, functions, and / or effects of the invention that can be viewed independently of one another, and which also further develop the invention independently of one another. Therefore, the exemplary embodiments are intended to encompass combinations other than those in the embodiments explained. Furthermore, the described embodiments may also be supplemented by further features, functions, and / or effects of the invention already described.

[0069] In the figures, the same reference symbols designate the same features or functions.

[0070] It shows :

[0071] FIG 1 is a schematic sectional view through an electrolysis cell with a membrane electrode arrangement for the electrolysis of water;

[0072] FIG 2 shows a membrane electrode arrangement;

[0073] FIG 3 is a schematic representation of a sequence for the process for recovering catalyst material from the membrane electrode assembly according to the prior art;

[0074] FIG 4 is a schematic representation of a sequence for the process for recovering catalyst material from the membrane electrode assembly according to the invention;

[0075] FIG 5A is an electrode-side plan view of an untreated membrane electrode assembly;

[0076] FIG 5B is a plan view of the abrasively treated membrane electrode assembly of FIG 1 with the electrode layer partially removed;

[0077] FIG 5C shows a plan view of the abrasively treated membrane electrode assembly of FIG 1 with the electrode layer completely removed; FIG 6 shows a recycling plant with plant components and corresponding process diagram.

[0078] FIG. 1 shows a schematic sectional view of an electrolysis cell 11 with a membrane electrode assembly 1. The membrane electrode assembly 1 comprises, in this case, a polymer membrane 3 as the membrane 3, which has two opposite surfaces 15, 17, on which a respective electrode layer 9 is applied on the anode side and the cathode side. The electrode layer 9 comprises respective catalyst materials 5, 7. The electrode layer 9 with the first catalyst material 5 and the second catalyst material 7 in turn contacts a respective, typically multilayered gas diffusion layer 19, 21, which forms a porous and conductive structure and comprises a respective nonwoven material. Each gas diffusion layer 19, 21 contacts a respective contact plate 27, 29, the so-called bipolar plates of the electrolysis cell 11.

[0079] This forms an anode region 23 and a cathode region 25 for an electrolysis cell 11. The contact plates 27, 29 as well as the gas diffusion layers 19, 21 are electrically conductive, so that a low-resistance electrical contact is established between the respective electrode layer 9 containing a catalyst material 5, 7 and the respective contact plate 27, 29. The contact plates 27, 29 also have flow channels (not shown) through which, on the one hand, water or an electrolyte can be supplied to the electrolysis cell 11 and, on the other hand, electrolysis products, namely, for example, hydrogen and oxygen, can be separately transported away.

[0080] The membrane electrode assembly 1 is shown as a separate component in FIG. 2. The membrane electrode assembly 1 comprises a polymer membrane 3 and the electrode layer 9 with the catalyst material 5, 7. The membrane electrode assembly 1 can be manufactured as a separately handleable component, so that the membrane electrode assembly 1 can be easily handled during the manufacturing process of the electrolysis cell 11. The catalyst material 5, 7 is of important functional importance for the electrolysis cell 11 and has considerable economic value, and contains rare metals such as iridium or platinum.

[0081] The membrane electrode arrangement 1 comprises at least the anode-side and the cathode-side electrode layer 9 with the metallic catalyst material 5, 7. A first catalyst material 5 is introduced into the anode-side electrode layer 9. A second catalyst material 7 is introduced into the cathode-side electrode layer 9. Both electrode layers 9 are connected to the polymer membrane 3 to form one component. The respective chemical reactions take place in the catalyst layers, wherein electrons can be diverted to the contact plates 27, 29 via the catalyst and any support structure that is electrically conductive. It is therefore advantageous if the respective electrode layer 9 with the metallic catalyst material 5, 7 has the best possible electrical conductivity and a catalytic capacity.In addition, hydroxide ions OH" are generated in an alkaline environment and protons H+ are generated in an acidic environment, which migrate as charge carriers through the respective polymer membrane 3. For the catalyst materials 5, 7 it is therefore also desirable that they have a correspondingly good conductivity for the respective ions so that these can be easily transported to the polymer membrane 3 or from the polymer membrane 3 to the respective catalytic centers. It is therefore intended that the best possible ionic bonding of the first catalyst material 5 to the first surface 15 and of the second catalyst material 7 to the opposite second surface 17 of the polymer membrane 3 is achieved. At the same time good electrical contact and conductivity of the catalyst material 5, 7 in the electrode layer 9 is brought about.

[0082] The membrane electrode assembly 1 is specially designed for use in acidic environments for PEM water electrolysis. For this purpose, the polymer membrane 3 is prepared as a proton-conductive membrane 3. The anode-side catalyst layer has iridium as the first catalyst material 5. The cathode-side catalyst layer has platinum as the second catalyst material 7. The iridium is applied to the first surface 15 of the polymer membrane 3, and the platinum to the opposite second surface 17 of the polymer membrane 3. The polymer membrane 3 functions as the substrate 13.

[0083] During the new production or recycling or reprocessing of a membrane electrode assembly 1, a polymer membrane 3 is first provided as a substrate 13 to produce the membrane electrode assembly 1, which is then coated. The polymer membrane 3 has a first surface 15 and a second surface 17 facing away from the first surface 15. For the purpose of providing a respective electrode layer 9 and introducing the respective catalyst materials 5, 7, a coating tool (not shown in detail) is used. The catalyst materials 5, 7 are then provided in paste form, in particular as a pasty mass, so that they can be applied well and intimately to the respective surfaces 15, 17 by means of the coating tool. It can be provided that particles of the respective catalyst material 5, 7 are simply dissolved and mixed with an ionomer in a highly viscous solvent.The production of the catalyst paste is not shown in detail in the figures. However, conventional methods for mixing substances can be used for this purpose. With such a method, however, no polymeric binder or non-ionic binder needs to be added to the mass. The viscosity of the paste can be adjusted via the ionomer content in the solvent so that conventional industrial coating processes for electrode pastes can be used. For example, doctor blade or dip coating can also be provided as an alternative. If the membrane electrode assembly 1 is one that has already been used in an electrolysis cell 11, i.e. is used, it is very advantageous and desirable from an economic and ecological point of view to recover the valuable metallic catalyst material 5, 7 in a recycling process.For this purpose, the membrane electrode assembly 10 is removed from the electrolysis cell 11 and prepared for a recycling process.

[0084] FIG 3 shows a simplified representation of a method for recovering catalyst material according to the prior art. This process uses a multi-stage recycling process for a membrane electrode assembly 1, the essential process steps of which are only shown here in a very simplified manner. In a first step S 1, a used membrane electrode assembly 1 is provided which has an electrode layer 9 on a polymer membrane 3. The polymer membrane 3 is based on a PFAS material, i.e. per- and polyfluorinated alkyl substances (PEAS), which require special treatment in a complex recycling process. In a step S 2, the entire membrane electrode assembly 1 is crushed and incinerated. In the process, a homogenate mixture 49, e.g. ash, is obtained from the solid components of the entire membrane electrode assembly 1 and is further processed.Due to this process control, the homogenate mixture 49 only has a very small proportion of valuable materials 53, i.e. a very low valuable material concentration. After incineration, the resulting ash is therefore usually mixed with other batches or ore concentrates and subjected to a refining process in order to separate the precious metals it contains. In a step S3, a non-recyclable residue 51 is separated from the homogenate mixture 49. This ultimately makes it possible to separate the valuable materials 53 of interest in a step S4 and recover them in a sufficiently high valuable material concentration, in particular the economically particularly interesting catalyst material 5, such as iridium. The loading of the polymer membrane 3 with PFAS makes previously used recycling methods, such as the recovery of the valuable materials 53 by incineration followed by refining of the homogenate mixture 49, e.g.of the ash, becomes a major technological challenge. During combustion, hydrofluoric acid HF is produced. Due to the aggressive properties of hydrofluoric acid HF, special combustion chamber and pipe linings as well as an extensive and very complex gas scrubbing system are required. For example, a membrane electrode assembly 1 can typically contain a fluorine content of around 4 wt%. According to the 17th Federal Immission Control Ordinance (17th BImSchV), waste with a halogen content of greater than 1% in the waste must be incinerated at a minimum incineration temperature of 1,100 °C. This means that it cannot be disposed of in conventional incineration plants, which have incineration temperatures of 850 °C - 1,100 °C. In the process described, as well as in other known processes, e.g.In solvent-based recycling concepts, the valuable materials 53 locally concentrated in the electrode layer 9 are homogenized with the entire membrane electrode assembly 1 or other waste from the batch, for example by incineration or chemical dissolution, forming the homogenate mixture 49. However, this established process significantly reduces the concentration of the valuable materials 53 of interest in the material turnover, i.e., in the homogenate mixture 49, and the associated technical expenditure for recovery is correspondingly increased, as well as the achievable recovery yields.

[0085] The present invention has recognized these disadvantages and proposes a significantly more efficient and environmentally friendly recycling of a membrane electrode assembly 1 compared to the known processes.

[0086] FIG 4 shows a schematic representation of a corresponding typical sequence for the method for recovering catalyst material 5 of a membrane electrode assembly 1. In a first recycling step RI, a membrane electrode assembly 1 is provided and prepared for subsequent abrasive treatment. The membrane electrode assembly 1 to be separated is placed in water or sprayed with water for approximately two hours so that complete hydration is achieved. Complete hydration causes the membrane electrode assembly 1 and specifically the polymer membrane 3 to soften. This promotes and increases the abrasive effect on the electrode layer 9, which is applied to the polymer membrane 3 as a carrier material. In addition, the water reduces the penetration of non-polar solvents into the polymer membrane 3 or into the carrier material forming the polymer membrane 3.The membrane electrode assembly 3 prepared in this way is fed to the recycling step R2. In the recycling step R2, electrode material is abrasively removed from the polymer membrane 3 and separated, so that a separate material 31 is obtained which contains metallic catalyst material 5, 7. In this case, an abrasive agent 33 is used which is applied to the electrode layer, a material-removing effect being brought about by the mechanical action of the abrasive agent 33 on the electrode layer 9, whereby electrode material is removed from the carrier material. The abrasive agent 33 comprises a brush which is guided on the electrode layer 9 under a predetermined contact pressure, whereby a relative movement is brought about between the brush fibers and the electrode material.In this case, ultrasound can be generated to support the recycling step R2, so that the electrode material of the electrode layer 9 is excited to mechanical vibrations and the material-removing effect is increased. When using a brush that possibly generates ultrasound as the abrasive agent 33, the brush can be wetted with 2-propanol. It has been shown that this measure increases the abrasive effect on the electrode layer 9, since dissolution processes of structure-giving components of the electrode layer 9 are specifically brought about by 2-propanol. In the recycling step R3, the ultrasound-assisted brush is guided in repeated, circular movements over the fully hydrated membrane electrode arrangement 1. An integrated pressure sensor is provided which prevents excessive pressure against the membrane electrode arrangement 1, which would result in mechanical damage to the membrane electrode unit.The separator 31 obtained abrasively in recycling step R3 is washed off the surface of the polymer membrane 3 with water and collected in recycling step R4. The separator 31 contains electrode material 9 with the metallic catalyst material 5. The recycling steps R2, R3 and R4 are repeated until the desired cleaning result is achieved by the abrasive treatment, i.e. until the electrode layer 9 has been abrasively removed as completely as possible. This achieves a mechanical separation of the polymer membrane 3 and the material of the electrode layer 9. The polymer membrane 3 is recovered without destruction and the electrode layer 9 is abrasively removed. The polymer membrane 3 from which the electrode layer 9 has been cleaned is fed to a separate recycling step R5 for further utilization.In an alternative or additional embodiment to the abrasive brush, a powdered blasting agent with a carrier gas can also be used as an abrasive agent 33, which can be sprayed onto the surface of the electrode layer 9 by means of a pressurized carrier gas. For example, plastic granules, small metal or ceramic balls, or quartz sand can be used as the blasting agent.

[0087] FIGS. 5A to 5C show the result of material removal carried out on a laboratory scale in several abrasive treatment and cleaning steps using a brush as the abrasive 33, using a membrane electrode assembly 1 as an example. FIG. 5A shows a plan view of an as yet untreated membrane electrode assembly 1 with an electrode layer 9. The electrode layer 9 comprises the metallic catalyst material 5, in particular iridium in the case of an anodic electrode layer 9, which results in a dark metallic coloring of the surface. FIG. 5B shows the membrane electrode assembly 1 which has already been partially treated and cleaned using the abrasive process, with a somewhat lighter color and the surface of the polymer membrane 3 which has already been largely exposed. FIG. 5C shows a completely cleaned membrane electrode assembly 1.Here, the electrode layer 9 has been completely abrasively removed, and the surface of the polymer membrane 3 is completely exposed. Thus, only the carrier material (substrate) and the structure of the polymer membrane 3 are visible in FIG. 5C. It has been shown that the electrode layer 9 can be very effectively abrasively removed with virtually no damage to the carrier material of the polymer membrane 3, and that valuable materials 53 such as iridium can be recovered from the separated residue 31 without the need to incinerate the PFAS membrane.

[0088] The proposed abrasive recycling process of the invention is therefore characterized by gentle but selective mechanical-abrasive material removal for separating an electrode layer 9 containing a catalyst material 5 and the support materials of the polymer membrane 3 of a membrane electrode assembly 1. An abrasive 33 based on brushes or rollers or a particle-based blasting agent and optionally admixing of solvents is used. In this process, no disadvantageous mixing and homogenization of components rich in and poor in valuable materials takes place, as described in FIG. 3 in the known processes. In this process, the membrane electrode assembly 1 is completely crushed and incinerated to form a homogenate mixture 49 with a very low concentration of valuable materials.In addition, depending on the solvent selected, the abrasive process can virtually completely prevent damage to the carrier material, in particular to the polymembrane 3, so that in addition to the recovery of valuable metallic materials 53 from the electrode layer 9, effective membrane recycling is also possible in the recycling step R5. This also allows the carrier material of the polymer membrane 3 to be recovered and, if necessary, processed and reused.

[0089] FIG 6 shows a possible implementation concept of a recycling plant 35 with plant components, based on which the basic steps of the process control are also illustrated, as they are particularly applicable on an industrial scale. The recycling plant 35 is set up for industrial flow processing and has a hydration chamber 47 and a separation device 37 which is connected downstream of the hydration chamber 47. The separation device 37 comprises a first separation chamber 39A and a second separation chamber 39B which is connected downstream of the first separation chamber 39A in the process direction. The hydration chamber 47 is equipped with a plurality of spray humidifiers (not shown in detail), so that during operation complete hydration of the membrane material can be achieved by introducing water and swelling.The first separation chamber 39A has a brush unit which is designed as an ultrasonic brush with an ultrasonic generator. The second separation chamber 39B has roller brushes. The separation chamber 39A also has a solvent injector 41. A separation comb 43 is formed in the separation chamber 39B as a spatial unit. It is also possible for the separation comb 43 to be arranged downstream of the separation chamber 39B in the process direction and to be spatially separated. The separation chamber 43 is equipped for removing and transporting the separation 31 from the surface of the polymer membrane 3. For this purpose, a separation device 45 is arranged downstream of the separation comb 43 so that used solvent can also be collected and recycled.The term separation device 45 is understood here to mean a technical plant device of the recycling plant in which different process engineering functions can be implemented and integrated, which can in particular be used successively in at least two process steps. In a first process engineering step, a solid-liquid separation of electrode material and solvent is to be carried out. In terms of apparatus, this can be implemented in the separation device 45, for example, by a first separation device such as a sedimenter, a centrifuge, a flotation apparatus or a permeation apparatus. In a second process engineering step, a liquid-liquid separation of water and solvent is to be carried out. In terms of apparatus, a rectification column, an adsorber or a permeation apparatus is preferably provided for this purpose as the second separation device.The separation device 45 is thus designed with a first separation device for a solid-liquid separation for the deposition of the electrode material and with a second separation device for a liquid-liquid separation for the recovery of used solvent.

[0090] In order to replenish fresh solvent as needed, a storage container 59 is provided which feeds the solvent injector 41 with stored solvent. In addition, the separation device 45 is designed such that the separate 31 containing the valuable material 53 can be largely separated from the solvent and recovered as a moist, valuable material-containing dispersion in a heterogeneous mixture of the valuable material 53 with a small residual solvent. Furthermore, a processing device 55 for the polymer membrane 3 and a different processing device 57 for the separate 31 are provided. The processing device 55 for the polymer membrane 3 is connected directly downstream of the separation chamber 39B. The processing device 57 for the separate 31 is connected downstream of the separation device 45, so that catalyst material 5 can be recovered from the valuable material 53 in further recycling steps.The separation chamber 39A, 39B is designed to accommodate and treat a membrane electrode unit 1 in such a way that, during operation, a hydrated membrane electrode unit 1 can be introduced into the separation chamber 39A, 39B and the electrode material 9 can be abraded and separated in a targeted manner from the surface of the polymer membrane 3. From a technical perspective, it is also possible, alternatively or in addition to the arrangement with ultrasonic brushes, for a blasting unit to be provided in a separation chamber 39A, 39B, which is designed as a particle blasting unit. During operation, in this embodiment, the surface of the electrode layer 9 can be subjected to a powdered, abrasive blasting agent with a carrier gas under a working pressure.

[0091] The separation of the separated material 31 takes place during operation of the recycling plant 35 by abrasion of the electrode layer 9 from a membrane electrode arrangement 1. The abrasion when a brush system is used as the abrasive agent 33 is caused by the brush building up a contact pressure on the medium to be separated and the build-up of a relative speed between the brush fibers and the separating medium. The relative speed and the contact pressure can be optimized in terms of process technology. In order to increase the abrasion effect, a solvent is fed in via the solvent injector 41. For the brush system, brushes are generally understood to be any device that consists of a base body to which a brush trim (fibers) is attached. The material and shape are considered to be the design properties of the base body. The brush trim varies in terms of material, fiber diameter, trim length and trim density.The technical design can be achieved using various brush types. These include round brushes, roller brushes, strip brushes and disc brushes. In the simplest case, examples of applications for these brush types are even manual brushes or toothbrushes with an ultrasonic head. Rotary, vibrating and ultrasonic brushes have proven to be particularly effective for small applications. Strip brushes and roller brushes are particularly suitable for technical applications. Suitable materials for the base body are wood, metal or plastic. Natural fibres, synthetic fibres or wires are suitable for the brush trim. The optional choice of solvent depends on the components of the coating and the requirements for the integrity of the carrier material after separation. 2-Propanol is suitable for a tested PFAS carrier material without causing any visible damage or damage that can be measured using FTIR / XRD.Propan-2-one attacks the substrate more strongly, but increases the abrasive effect more than 2-propanol. Other potential solvents include alcohols (ethanol), carboxylic acid esters (ethyl acetate), ethers (diethyl ether), ketones (propan-2-one), alkanes (n-hexane), aromatic hydrocarbons (toluene), halogenated aliphatic hydrocarbons (carbon tetrachloride), and glycol ethers (ethylene glycol monoethyl ether).

Claims

Patent claims 1. A method for recovering catalyst material (5, 7) from a membrane electrode arrangement (1), in which a membrane electrode arrangement (1) is provided, the membrane electrode arrangement (1) having a membrane (3), in particular a polymer membrane, as a carrier material, to which an electrode layer (9) made of an electrode material containing a metallic catalyst material (5, 7) is applied, electrode material being abrasively removed from the membrane (3) and separated, so that a separate material (31) is obtained, metallic catalyst material (5, 7) being recovered from the separate material (31).

2. Method according to claim 1, wherein an abrasive agent (33) is applied to the electrode layer (9) in such a way that a material-removing effect is brought about by mechanical action of the abrasive agent (33) on the electrode layer (9), whereby electrode material is removed from the carrier material.

3. Method according to claim 1 or 2, wherein the abrasive means (33) comprises a brush which is guided under a predetermined contact pressure on the electrode layer (9), whereby a relative movement is brought about between brush fibers and electrode material.

4. A method according to claim 1, 2 or 3, wherein ultrasound is generated so that the electrode material is excited to mechanical vibrations and the material-removing effect is enhanced.

5. Method according to claim 4, wherein an ultrasonic frequency of 20 kHz to 400 kHz, in particular 35 kHz to 200 kHz, is set.

6. Method according to one of the preceding claims, in which a powdered blasting agent is mixed with a carrier gas under a jet pressure is applied to the surface of the electrode layer (9).

7. The method according to claim 6, wherein the blasting medium comprises plastic granules.

8. Method according to one of the preceding claims, in which a solvent is injected during the abrasive removal, in particular 2-propanol or acetone, so that the abrasive effect on the electrode material is increased.

9. The process according to claim 8, wherein the solvent is selected from the group of alcohols, ethers, ketones, alkanes or aromatic hydrocarbons.

10. Method according to one of the preceding claims, in which the hydration of the carrier material is carried out so as to cause a softening of the membrane (3).

11. Method according to one of the preceding claims, in which the obtained separation (31) is removed from the surface of the membrane (3) with a cleaning agent, in particular with water, and collected, and in which metallic catalyst material (5, 7) is recovered from the collected separation (31).

12. The method according to claim 11, wherein the membrane (3) freed from the electrode layer (9) is recycled so that carrier material is recovered.

13. Recycling plant (35) for carrying out the method according to one of the preceding claims, with a separation device (37) comprising a separation chamber (39A, 39B) in which a brush unit and / or a jet unit is arranged and which is designed to receive and treat a membrane electrode unit (1), so that in operation a membrane electrode unit (1) can be introduced into the separation chamber (39A, 39B) and electrode material from the membrane (3) of the membrane electrode unit (1) can be abrasively removed and separated.

14. Recycling plant (35) according to claim 13, wherein the separation chamber (39A, 39B) has a solvent injector (41) and the brush unit is equipped with an ultrasonic brush.

15. Recycling plant (35) according to claim 13, wherein in the separation chamber (39A, 39B) the blasting unit has a particle blasting unit, so that during operation the surface of the electrode layer can be subjected to a powdered abrasive blasting agent with a carrier gas under pressure.

16. Recycling plant (35) according to one of claims 13 to 15, wherein the separation chamber (39A, 39B) has a separating comb (43) , which is equipped for removing the separator (31) from the membrane (3).

17. Recycling plant (35) according to one of claims 14 to 16, in which the separating comb (43) is followed by a separating device (45) so that used solvent can be collected and recycled.

18. Recycling plant (35) according to claim 17, wherein the separation device (45) is equipped with a first separation device and with a second separation device connected downstream of the first separation device, wherein the first separation device has a solid-liquid separation device and the second separation device has a liquid-liquid separation device.

19. Recycling plant (35) according to one of the preceding claims, in which a hydration chamber (47) is provided which is connected upstream of the separation chamber (39A, 39B), and in which, during operation, the membrane electrode unit (1) is prepared for an abrasive treatment in the separation chamber (39A, 39B). can be pared, wherein swelling and softening of the membrane (3) can be brought about in the hydration chamber (47).

Images