Process for treating used membrane material from an end-of-life filtration module

Abstract

The invention relates to a process for treating used membrane material from an end-of-life filtration module, said membrane material being made of a single polymer material. The process comprises the following steps: - a) a step of underwater grinding the used membrane material, producing a membrane material powder; - b) an acid washing step of the membrane material powder, during which the latter is brought into contact with an acidic liquid medium; - c) a water rinsing step of the membrane material powder from step b); and - d) a step of removing water by drying the membrane material powder from step c). The invention also relates to an installation implementing the process according to the invention. Abstract figure: Fig. 1

Description

Title of the invention: Process for treating used membrane material from an end-of-life filtration module Scope of the invention

[0001] The present invention relates to a method for treating used membranes from end-of-life filtration modules. The treatment method according to the invention makes it possible, in particular, to treat used membranes, especially those made of a single polymer material, notably for the purpose of recycling them. Prior art

[0002] One envisaged field of application is in particular that of the recycling of filtration modules of a liquid, and in particular of water.

[0003] Liquid filtration, and in particular water filtration, uses various filtration techniques (reverse osmosis, nanofiltration, ultrafiltration, etc.) which essentially consist of filtering the liquid using a membrane material with a porous structure, the pore size of which depends on the application and the treatment objectives or performance levels to be achieved. Filtration is commonly used for the treatment of drinking and industrial water, in desalination and reuse, particularly for implementing clarification, disinfection, desalination, and other processes.

[0004] Typically, the membrane material allows the passage of water molecules and retains suspended chemical or biological compounds larger than the pore size of the membrane material, such as viruses and bacteria, for example. This membrane material can have various structures and morphologies.

[0005] Filtration is typically implemented using filtration modules containing a porous membrane material. Four types of modules are frequently used: tubular modules, hollow fiber modules, plate modules (also called flat modules), and spiral modules. The present invention relates more particularly to membranes made from hollow fiber and plate modules.

[0006] Filtration modules typically comprise a frame, generally made of polymer material, holding the membrane material, usually a porous polymer material. In hollow fiber membrane modules, the hollow fibers of the membrane material are assembled into bundles. In plate modules, the membrane material is in the form of a plurality of flat membranes, these flat membranes being typically stacked and separated by intermediate frames.

[0007] The membrane material is generally a high-value-added engineering polymer material, usually a fluoropolymer such as, for example, polyvinylidene fluoride (PVDF), or a sulfur-containing polymer, such as polyethersulfones (also denoted PES). PVDF has the advantage of resisting a wide range of chemical compounds, which is one of the reasons why it is valued for use as a filter.

[0008] When these filtration modules cease to be effective, particularly due to irreversible clogging or the degradation of their constituent polymers, they are removed from the installation. These end-of-life modules are most often either landfilled or incinerated. The high-value membrane material is thus lost. Furthermore, the landfilling of polymer materials is increasingly regulated to prevent the migration of degradation products into the soil. In particular, this membrane material can release polyfluoro or perfluorinated polymers (also known as "PFAS" from the English "Per- and PolyfluoroAlkyl Substances") during its degradation, which are harmful to the environment. In addition, fluorinated polymers such as PVDF release hydrofluoric acid during incineration, which must be neutralized.

[0009] Thus, on the one hand, we disseminate in nature compounds that are more or less dangerous, and on the other hand, we deprive ourselves of polymer materials with relatively high added value, particularly in the case of Poly(vinylidene fluoride), the costs of obtaining which are relatively high.

[0010] There are processes for treating membranes. For example, US patent 2022 / 0297036 describes a process for recycling a used PVDF membrane comprising a washing step in which the membrane is soaked in sodium hypochlorite (NaClO) for 0.5 to 4 hours, then in citric acid for 0.5 to 4 hours to remove dirt from the membrane surface. This washing step is followed by a rinsing step with deionized water to obtain a membrane that is then subjected to a restructuring step using a structuring agent, during which the membrane undergoes pore expansion and hydrophilization. The membrane then undergoes a step to repair its hydrophobicity by contacting it with an acidic dopamine solution. This process is, however, complex and requires the use of numerous chemical compounds.Furthermore, maintaining the integrity of membranes can be difficult, especially when dealing with hollow fibers.

[0011] Other processes involve cutting the membranes before treating them in a succession of solutions. They are relatively complex and require the use of numerous chemical compounds.

[0012] A problem which then arises and which the present invention aims to solve is to provide an efficient and simple process to implement which allows the recovery of high value added polymer materials for reuse. Summary of the invention

[0013] In order to solve this problem, a process is proposed for treating a used membrane material from an end-of-life filtration module, said membrane material being made of a single polymer material. This process comprises the following steps: - a) a step of grinding the used membrane material underwater producing a ground membrane material; - b) an acid washing step of the ground membrane material during which the latter is brought into contact with an acidic liquid medium; - c) a water rinsing step of the ground membrane material from step b); and, - d) a step of removing water by drying the ground membrane material from step c).

[0014] Thus, a feature of the invention lies in the combination of several processing steps of a membrane material made up of a single material to recover the high value added polymer constituting it.

[0015] The underwater grinding step makes it possible to remove some of the dirt and fouling from the membrane material while reducing its size. Obtaining a ground material facilitates the transport and subsequent packaging of the membrane material and improves the efficiency of the treatments by increasing the contact surface area. This first step also reduces the quantity of chemical compounds required for the following steps, particularly step b). The acid wash in step b then allows for more thorough treatment of the ground membrane material to remove as many impurities as possible. The subsequent steps c) and d) aim to rinse and dry the ground membrane material, which can then be packaged and stored. The ground membrane material thus treated has sufficient purity to allow the reuse of its constituent polymer.

[0016] The presented process also makes it possible to optimize the management of used membranes at the end of their life by avoiding their landfilling or incineration and by facilitating their transport, the shredded membrane material being easier to move and to transporting only the used membrane material. This process thus makes it possible to recycle part of the waste produced by systems that include filtration modules.

[0017] Advantageously, the membrane material can be chosen from polyvinylidene fluoride and polyethersulfone.

[0018] Polyvinylidene fluoride and polyethersulfone are polymers frequently used in membranes. Preferably, the membrane material can consist solely of polyvinylidene fluoride.

[0019] Advantageously, the membrane material can be in the form of hollow fibers or flat membranes.

[0020] Advantageously, step a) may include at least one of the following features: - the crushed material has a particle size of 1 millimeter to 50 millimeters, preferably from 1 to 30 mm, more preferably from 4 to 20 mm, - an implementation with a water / membrane material mass ratio of 11 to 1, - the membrane material is introduced inside a mill supplied with water via a mill loading hopper directly or by a conveyor belt.

[0021] Advantageously, step b) of acid washing may include at least one of the following features: - The acidic liquid medium is an aqueous solution of at least one acid chosen from an organic acid and a mineral acid, - the acidic liquid medium comprises at least one acid chosen from hydrochloric acid, citric acid, oxalic acid, - the acidic liquid medium has a pH of 0 to 4, preferably 0 to 2, - implementation under agitation, - implementation with a mass ratio of acidic liquid medium / ground membrane material of 10 to 1, - an implementation lasting 0.5 to 4 hours.

[0022] Advantageously, step c) of rinsing may include at least one of the following features: - an implementation with a water / ground membrane material mass ratio of 50 to 1, - implementation under agitation, - an implementation lasting 0.5 to 4 hours, - implementation by bringing the ground material into contact with water until the pH of the water from the contact is identical to the pH of the water before contact.

[0023] Advantageously, step d) includes at least one of the following features: - implementation at a temperature of 40 to 100 °C, preferably 40 to 80 °C, - a drying time of 0.5 to 4 hours, - implementation in the presence of an airflow at a temperature of 40 to 100 °C, - at the end of step d), the ground membrane material has a water content of less than 1% by mass.

[0024] Most often, the membrane material is contained within filtration modules, such modules including, in particular, means for retaining the filtration material, a housing, and inlets and outlets for the liquid to be filtered. Thus, advantageously, upstream of step a) underwater grinding, a step e) dismantling the end-of-life filtration modules containing said used membrane material may be provided, during which said modules are dismantled and the used membrane material is recovered.

[0025] Advantageously, between step c) and step d), the process may include a step f) of draining the ground membrane material from step c). The draining step f) reduces the amount of water to be removed during step d) of water removal by drying and thus reduces the energy used to completely dry the ground membrane material during step d).

[0026] Advantageously, downstream of step a), a conditioning step for the ground membrane material may be provided, during which the ground membrane material is placed inside a woven material container, optionally made of liquid-permeable woven material. The conditioning of the ground membrane material allows for easy transport of the ground material from one step to another or at the end of the process according to the invention.

[0027] Preferably, at least one of steps b) to d) can be carried out while the ground membrane material is inside the container made of liquid-permeable woven material. This facilitates processing by limiting losses of ground material.

[0028] In one embodiment, the process according to the invention comprises only steps a) to d), and optionally steps e) and / or f).

[0029] Another object of the invention is an installation for processing used membrane material from an end-of-life filtration module comprising: - an optional section (E) for dismantling filtration modules, - an underwater grinding section (A) for the membrane material implemented in at least one water-supplied grinder, - an acid washing section (B) for the ground membrane material comprising at least one acid liquid supply system, - a water rinsing section (C) for the ground membrane material comprising at least one water supply system, - an optional draining section (F) for the ground membrane material from the rinsing section, - a drying section (D) for the ground membrane material from the rinsing section or the optional draining section (F), - an optional section for conditioning the ground membrane material, - means of transporting the membrane material from one section to another to implement the process as described above.

[0030] Advantageously, the installation may include at least one of the following features: - The underwater grinding section includes at least one water-cooled grinder loading hopper, and optionally a conveyor belt, - the means of transport include one or more of the following transport systems: a conveyor belt, a screw conveyor, a hopper, - The acid washing section includes at least one system for recirculating the acidic liquid medium used, - The water rinsing section includes at least one system for recirculating used water and / or a system for controlling the pH of the water leaving the rinsing section; - The conditioning section includes at least one loading station for the ground membrane material inside a woven material container, optionally made of liquid-permeable woven material. - In the acid washing section, the ground membrane material is placed inside a container made of woven material permeable to liquids, - in the water rinsing section, the ground membrane material is placed inside a container made of woven material permeable to liquids. Detailed description of the invention

[0031] The invention is now described with reference to the accompanying, non-limiting drawing, which schematically represents [Fig.1] the installation according to one embodiment of the invention.

[0032] Method

[0033] The process according to the invention is a process for treating a used membrane material from an end-of-life filtration module. The membrane material here consists of a single polymer material.

[0034] The process includes a step a) of grinding under water of a used membrane material producing a membrane material grind, a step b) of acid washing of the grind, a step c) of rinsing with water of the grind from step b) and a step d) of removing the water by drying.

[0035] The process may also include an optional step e) of dismantling a filtration module upstream of step a) and an optional step f) of draining upstream of step d).

[0036] The alternative configurations of the different stages of the process presented below can be combined according to the treatment objective decided.

[0037] Optional step e) of dismantling a filtration module

[0038] Upstream of step a) underwater grinding, the process may include a step e) of dismantling the end-of-life filtration modules containing said used membrane material during which said modules are dismantled and the used membrane material they contain is recovered and which is to be recycled.

[0039] This step can be implemented in an optional section (E) of dismantling filtration modules and allows the recovery of the used membrane material.

[0040] The end-of-life filtration modules supplied may be modules that have ceased to be effective, in particular due to irreversible clogging, or due to the degradation of the polymers from which they are made. They may also be defective filtration modules intended for disposal.

[0041] Dismantled end-of-life filtration modules can be tubular modules, hollow fiber modules, plate modules (also called flat modules), and spiral modules. Preferably, the dismantled modules are hollow fiber and plate modules.

[0042] The filtration modules may include a frame holding the membrane material. Generally, the frame is made of a polymer material, which may have a porous structure. The frame may, in particular, include means for retaining the filtration material, a housing, and inlets and outlets for the liquid to be filtered.

[0043] For example, in a hollow fiber membrane module, the hollow fibers are assembled into one or more bundles. The framework typically comprises a housing, with one or more hollow fiber bundles being potted to the housing at one or both ends. The potting material is generally a mixture of resin or curable adhesive, such as epoxy resins, polyurethane resins, a specific resin-hardener combination, etc. In a plate module, the membrane material is in the form of flat membranes. The mechanical support of each membrane is provided by a support plate forming a frame through which the membrane is stretched. These support plates are typically stacked and separated by intermediate frames housed in a housing generally called a cassette. The support plates and the housing form the framework.

[0044] Generally, the housings are closed by clips or rivets (ultrasonic welds), although other fastening methods are possible (screws, rivets, other types of welds, etc.). The dismantling step then begins by opening the housing non-destructively when possible, or destructively. in other cases. For example, the bolt fixings must be destroyed, for example by drilling.

[0045] The housing can also be tubular in shape and formed in one piece. In this case, the dismantling step then begins with the removal of the membrane material contained in the housing.

[0046] In some cases, the module does not contain a housing. The frame then consists solely of one or more supports for the membrane material.

[0047] Once the casing is removed (or when it is absent), the membrane material is separated from its support. This separation can be achieved by cutting with a cutting tool such as a saw, a cutting blade, or the like. In the case of hollow fiber modules, the membrane material is cut flush with the sockets. In the case of plate modules, the membrane material is cut flush with the frame of the support plate.

[0048] The module can be dismantled manually or automatically.

[0049] The membrane material thus recovered consists of a single polymer material, typically a polyethersulfone or PVDF.

[0050] Preferably, the membrane material consists solely of PVDF. This polymer is a high-value polymer, notably used in the chemical industry for its high resistance to chemicals, such as acids or organic solvents, and to high temperatures. It can, for example, be used for fasteners such as screws or nuts, or for the manufacture of polymer additives. PVDF can also be used in electronics for the electrical insulation of wires and piezoelectric elements.

[0051] Step a) of grinding a used membrane material under water

[0052] During step a), the membrane material is ground under water to produce a ground membrane material.

[0053] This step allows the used membrane material to be cut into pieces so that it can be processed efficiently in the subsequent stages of the process, notably by increasing its contact surface area. This also makes it easier to handle by reducing its size.

[0054] This step also allows for a first washing of the used membrane material to remove some of the impurities trapped in the membrane material.

[0055] Step a) can be implemented in an underwater grinding section (A). The grinding section may include at least one water-fed grinder. The grinding section thus includes a water inlet and outlet, a membrane material loading system, and an outlet for the ground membrane material.

[0056] The loading system may include a mill loading hopper, with or without a conveyor belt. The latter, for example, discharges the membrane material over the mill hopper. It is preferable not to use screw loading systems, which tend to clog.

[0057] The grinding section may have, at its outlet, a grid whose mesh size is adapted to the size of the particles of ground membrane material that one wishes to recover.

[0058] It will thus be possible to choose a grid allowing the passage of particles of ground membrane material having the desired particle size.

[0059] The ground material can have a particle size of 1 millimeter to 50 millimeters. Preferably, the particle size is 1 millimeter to 30 millimeters and more preferably 4 millimeters to 20 millimeters, for example 4 to 15 millimeters.

[0060] The processing flow rate of the membrane material treated in step a) can be from 200 kg / h to 500 kg / h.

[0061] Water typically flows continuously through the grinding section and, in particular, through the grinder. During its mixing with the membrane material inside the grinder, at least some of the dirt present in the membrane material is transferred to the water.

[0062] This step can be carried out with a water / membrane material mass ratio of 11 to 1.

[0063] Optional conditioning step

[0064] Optionally, downstream of step a), the process may include a step of conditioning the ground membrane material. During this step, the ground membrane material may be loaded inside a woven material container, for example, to facilitate its transport.

[0065] The optional conditioning step can be implemented in a conditioning section. This section may include at least one loading station for the ground membrane material inside the woven material container.

[0066] For example, the woven material container can be placed near the outlet of the mill. It can then be filled with membrane material by a screw conveyor installed at the mill outlet or by an inclined conveyor belt on which the ground membrane material is placed, preferably by a screw conveyor. A pneumatic transfer system can also be used for loading the woven material container. At least one of the following steps (b) to (d), preferably each of these steps, can then be carried out while the ground membrane material is inside the woven material container.

[0067] When the conditioning step is carried out upstream of steps b) or c), the container is then made of a liquid-permeable material, possibly resistant to The acidic liquid medium used in step b) allows steps b) and / or c) to be carried out while the ground membrane material is located inside the woven material container, thus minimizing losses. The woven material could, for example, be made of polypropylene.

[0068] Although not preferred, the conditioning step can be implemented downstream of steps b), c) or d). Loading systems similar to those previously described can then be implemented (conveyor belt, screw conveyor, pneumatic conveying system, hopper).

[0069] Step b) of acid washing the ground membrane material

[0070] During this step, the ground membrane material is brought into contact with an acidic liquid medium.

[0071] For this purpose, the ground material can be immersed in the acidic liquid medium or brought into contact with a flow of acidic liquid medium at an appropriate flow rate. The flow rate of acidic liquid medium can be from 2 to 8 L / min, preferably from 2 to 6 L / min, for example 4 L / min.

[0072] Typically, the acidic liquid medium is an acidic aqueous medium. The acidic aqueous medium may contain one or more acids to obtain a relatively low pH, for example, from 0 to 4, preferably from 0 to 2. An organic acid or a mineral acid may be used, for example. By way of example, and preferably, the acid is chosen from hydrochloric acid, citric acid, and oxalic acid.

[0073] Step b) of acid washing can be carried out for a period of 0.5 hours to 4 hours.

[0074] Step b) can advantageously be carried out under agitation to improve the contact between the acidic medium and the ground material.

[0075] A mass ratio of acidic liquid medium / ground membrane material of 10 to 1 may be used.

[0076] The ratio and the pH are chosen in particular according to the cost of the acid while taking into account the fact that by increasing the concentration of the acid in the medium, the washing is more efficient for the same washing time.

[0077] Step b) is implemented in an acid washing section B.

[0078] This section B may include one or more tanks or reactors, preferably equipped with an agitation device. The tank(s) or reactor(s) used may, for example, be made of high-density polyethylene for small capacities or of stainless steel for larger capacities.

[0079] Section B typically includes at least one acid liquid feed system supplying the tank(s) or reactor(s). The acid liquid feed system may then include an inlet installed at each tank or reactor.

[0080] The feeding system may also include a valve or similar controlled to achieve an implementation of step b) with a mass ratio of acidic liquid medium / ground membrane material of 10 to 1.

[0081] Section B may further include at least one system for recirculating the acidic liquid medium.

[0082] Optionally, the ground membrane material can be placed inside a woven material container, which can be installed inside the tank or reactor of section B. In this case, the tank or reactor is preferably not equipped with a stirring device. Alternatively, a stirring device can be introduced inside the woven material container after it has been placed in the tank or reactor. It is then preferable that the woven material container not be completely full to prevent the ground material from escaping the container.

[0083] Step c) of rinsing with water the membrane material from step b)

[0084] Step c) is a water rinsing step of the ground membrane material from the previous step b).

[0085] Rinsing will allow the removal of some of the remaining acidic liquid medium used during step b) as well as the remaining impurities not removed during the previous steps.

[0086] This step is typically carried out by bringing the ground material into contact with water. For this purpose, the ground material can be immersed in water or brought into contact with a stream of water. The water flow rate can then be from 10 to 30 L / min, preferably from 15 to 25 L / min, for example 20 L / min.

[0087] The quantity of rinsing water used during this step can be defined so that the mass ratio of water to ground membrane material is 50 to 1.

[0088] The duration of step c) can be chosen so that the pH of the water at the end of the wash is identical to the pH of the water before the wash, this pH being typically from 6.5 to 9.5. A sufficient duration can be from 0.5 hours to 4 hours.

[0089] Step c) is, in addition, implemented in a water rinsing section C.

[0090] Section C may include one or more tanks or reactors, preferably equipped with an agitation device, or one or more friction washers.

[0091] Preferably, the tanks or reactors of section C may be of the same volume as the tanks or reactor of section B.

[0092] Section C may also include a rinsing water supply system and / or a system for recirculating used water.

[0093] Section C may further include a pH control system for the water exiting the rinsing section C. The pH control system may control the rinsing step c) so that the pH of the water at the end of the wash is identical to the pH of the water before the wash, this pH being from 6.5 to 9.5.

[0094] Section C may also include a system for controlling the appearance of the outgoing rinse water. The appearance control system may control step c) so that the appearance of the water at the end of the wash is identical to the appearance of the incoming water.

[0095] Optionally, the ground material exiting step b) can be placed inside a woven material container that can be installed in the tank or reactor. In this case, the tank or reactor is preferably not equipped with an agitation device. Alternatively, an agitation device can be introduced inside the woven material container after it has been placed in the tank or reactor. It is then preferable that the woven material container not be completely full to prevent the ground material from escaping the container.

[0096] Optional step f) of draining the ground membrane material

[0097] Optionally between step c) and step d), the process may include a step f) of draining the ground membrane material from step c).

[0098] The draining step f) can be carried out for a period of 0.5 hours to 4 hours.

[0099] The optional step f) can be implemented in an optional drainage section F.

[0100] This draining can be achieved by installing, for example, the ground membrane material on a perforated plate such as a grid so as to allow the rinse water to drain.

[0101] Optionally, the ground material exiting step c) can be placed inside a woven material container which can be installed in the optional drainage section F, for example on the perforated plate, or simply suspended, with the water dripping through the woven material of the container which is then permeable to liquids.

[0102] Step d) of removing water from the ground membrane material from the step

[0103] Step d) is a water removal step by drying the ground material membrane material from step c) or f). The water removal step allows obtaining a ground membrane material with a reduced water content.

[0104] The residual water content may be chosen according to possible subsequent recycling steps of the ground membrane material.

[0105] At the end of this step d), the ground material may, for example, have a water content of less than 1% by mass. For example, it may have a water content of 0.1 to 1% by mass, typically 0.5 to 1% by mass.

[0106] This step can be carried out at a temperature sufficient to achieve drying and lower than a glass transition temperature of the polymer material. This step can be implemented at a temperature of 40 to 100 °C, for example from 40 to 80 °C.

[0107] Step d) of water removal can be carried out over a period of 0.5 hours to 4 hours. It can be carried out under airflow (dynamic drying) or not.

[0108] The water removal step d) is implemented in a drying section D.

[0109] Drying section D may include one or more drying ovens or furnaces or silos which can increase the temperature of the ground material.

[0110] Preferably, section D can be ventilated by a flow of hot air, for example at a temperature of 40°C to 100°C or 40°C to 80°C, so as to reduce drying time.

[0111] For example, for masses of ground material from step c) less than 20 kg, section D may include one or more ovens or furnaces, while for masses of ground material from step c) greater than 20 kg, section D may include one or more silos.

[0112] For example, step d) can be implemented in a 4 m3 silo for a mass of 40 kilograms of ground membrane material from step c).

[0113] Optionally, the ground material exiting step c) or f), can be placed inside a woven material container which can be installed in the drying section D, namely inside a kiln or oven or silo.

[0114] Installation description

[0115] In [Fig. 1] described below, the solid lines with arrows represent means of transporting the membrane material before grinding or after grinding. The means of transport may, for example, include conveyors (belt conveyors, screw conveyors, pneumatic conveying systems), pallets, trolleys, or hoists for suspending a container of woven material.

[0116] With reference to [Fig. 1], the installation 100 for processing used membrane material from an end-of-life filtration module comprises an optional module dismantling section E suitable for carrying out optional step e), an underwater grinding section A suitable for carrying out step a), an acid washing section B suitable for carrying out step b) of the process, a water rinsing section C suitable for carrying out step c), an optional draining section F suitable for carrying out step f) and a drying section D suitable for carrying out step d).

[0117] In the optional dismantling section E, end-of-life filtration modules are dismantled, for example as described with reference to dismantling step e). Section E may thus include devices for dismantling the module frame, in particular for removing the housing, removing the housing fasteners, etc., for example screwdrivers or drills or the like. It may also include means for cutting the membrane material for the separate from its support. This section E may include a conveyor belt on which the dismantling is carried out and which then allows the membrane material to be transported to the underwater grinding section A.

[0118] Section A of grinding includes at least one water-fed grinder generally equipped with a loading hopper which can be fed with membrane material directly or via a transport system, for example a conveyor belt.

[0119] Optionally, downstream of section A and upstream of section B, the installation may include a conditioning section (not shown) comprising a loading station for the ground membrane material into a woven material container. For example, the woven material container may be placed at the end of a screw conveyor, at the end of an inclined conveyor belt on which the ground membrane material is placed, or it may be loaded by pneumatic conveying. The woven material container may then be moved by a hoist system or other carrying device to the other sections. Alternatively, this conditioning section may be positioned between sections B and C, between sections C and D (before or after section F), or downstream of section D.

[0120] The ground membrane material is then conveyed to the acid washing section B by a conveyor belt or other means, or directly into the woven material container. This section B may include one or more tanks or reactors, preferably equipped with an agitation device. Section B includes at least one acid liquid feed system 101 that can be connected to one or more tanks or reactors. The acid liquid feed system may include one or more containers holding the acid liquid and one or more pipes, valves, and / or pumps for transferring the acid liquid into the tank(s) or reactor(s).Section B may further include at least one recirculation system (not shown) for the acidic liquid medium, comprising one or more extraction lines for the acidic liquid medium from the tank(s) or reactor(s) fluidly connected to the feed system 101 and / or directly to the tank(s) or reactor(s). This recirculation system may be equipped with one or more valves and / or pumps for circulating the liquid medium.

[0121] Upon exiting section B, the ground membrane material is conveyed to the rinsing section C by a conveyor belt or other means, or directly into the woven material container. Section C may include one or more tanks or reactors, preferably equipped with an agitation device or one or more friction washers. Preferably, the tanks or reactors in section C may have the same volume as the tanks or reactors in section B. Section C may also include A rinsing water supply system 102 and / or a recirculation system (not shown) for the used water, fluidly connected to the water supply system and / or directly to the tank(s) or reactor(s). The water supply system may include one or more pipes, valves, and / or pumps for transferring water into the tank(s) or reactor(s). The water may come from a water network or from one or more water containers. The recirculation system may include one or more pipes for removing water from the tank(s) or reactor(s). This recirculation system may be equipped with one or more valves and / or pumps for circulating the water. Section C may further include a system for controlling the pH of the water leaving the rinsing section C and / or a system for controlling the appearance of the outgoing rinse water, for example, mounted on a water outlet pipe 103.For example, a pH meter could be placed on a pipe through which water flows from section C.

[0122] At the exit of section C, the ground membrane material is brought to the rinsing section by a conveyor belt or other means, or directly into the woven material container, to the optional draining section F or to section D.

[0123] The optional drainage section F may include a perforated plate on which the ground membrane material is installed and / or a woven material container suspension system.

[0124] The drying section D may include one or more ovens, furnaces, or silos capable of increasing the temperature of the ground material. Preferably, section D may then be ventilated by an airflow at a temperature of 40°C to 100°C so as to reduce the drying time.

[0125] When the membrane material has not previously passed through the optional conditioning section, the membrane material exiting step D can then be sent to this conditioning section to be loaded into a woven material container for subsequent use. Alternatively, it can be loaded into trolleys, cartons, tanks, or other suitable containers.

[0126] In one embodiment, the installation according to the invention comprises only sections A to D, and optionally sections E and / or F. Examples

[0127] Embodiments of the present invention are illustrated by the following non-limiting example.

[0128] Example 1: Processing of two batches of filtration modules.

[0129] The first batch of modules comprises highly clogged membrane materials described as "dirty membranes" and the second batch of modules includes membrane materials with low fouling, described as "clean membranes".

[0130] The two sets of modules are filtration modules whose membrane material is in the form of hollow fibers. The membrane material is PVDF.

[0131] Each module of the two sets of filtration modules includes a protective housing for the membrane material, secured with fastening clips. The hollow fibers are held inside the housing by potting at each of their ends.

[0132] Each module is first dismantled. To do this, the housing clips are removed using a screwdriver. Then, the membrane material is cut flush with the potting area using a power saw and recovered for further processing. Dismantling takes approximately 10 minutes for each module.

[0133] During this step, 157 kilograms of dirty membranes were recovered and 103 kilograms of clean membranes were recovered.

[0134] The two batches of membrane material are then ground in a 55kW mill. The mill used is a 55kW SML 45 / 60 mill with underwater equipment from Herbold®. The mill is loaded by pouring the membrane material directly into the mill's feed hopper. The grinding throughput is 250 to 500 kg / h.

[0135] During the grinding of the membrane material, water circulates to remove some of the impurities present in the membrane material. The outgoing water then has a cloudy and brown appearance for dirty membranes and a cloudy and opaque appearance for clean membranes.

[0136] At the outlet of the crusher a four millimeter screen is installed so as to obtain membrane material in the form of particles having a particle size less than or equal to four millimeters.

[0137] 20kg of ground membrane material from each batch is then introduced into a 400 litre tank and washed in a 200 litre bath of 2 mol / litre hydrochloric acid under agitation for 2 hours.

[0138] The membrane material is then transferred to another tank of the same dimensions and washed for 10 minutes in water. The membrane material is completely immersed in the circulating water to ensure turbulence.

[0139] During the acid treatment and rinsing steps, the pH of the solutions in which the ground membrane material is immersed is taken to verify that the process is working properly and thus control it.

[0140] After rinsing, the ground material is dried in a ventilated oven at 80°C for 4 hours to obtain a final moisture content of less than 0.1% by mass. The moisture content is measured using a thermobalance.

[0141] The ground material then has a white color. The ground material was subjected to colorimetric and infrared spectrographic analyses, allowing analysis of the interior and The exterior of the membrane material was analyzed by thermogravimetric analysis (TGA). These analyses showed that water washing during milling followed by acid washing for 2 hours achieved maximum clarity (L* = 83) and reduced the yellowing level (parameter b*) by 70%. Furthermore, water washing during milling reduced organic fouling on the outer membrane wall by 85%, and subsequent acid washing removed 34% of the remaining fouling. In TGA, the mineral residue level ranged from 23% to 26% but was not significantly reduced after water washing and acid washing.

Claims

Demands

1. A process for treating a used membrane material from an end-of-life filtration module, said membrane material being made of a single polymer material, characterized in that it comprises the following steps: - a) a step of grinding the used membrane material under water producing a membrane material powder; - b) an acid washing step of the membrane material powder during which the latter is brought into contact with an acidic liquid medium; - c) a step of rinsing the membrane material powder from step b) with water; and, - d) a step of removing the water by drying the membrane material powder from step c).

2. Processing method according to claim 1, characterized in that the membrane material is selected from polyvinylidene fluoride and polyethersulfone.

3. Processing method according to claim 1 or 2, characterized in that the membrane material is in the form of hollow fibers or flat membranes.

4. Processing method according to any one of claims 1 to 3, characterized in that step a) comprises at least one of the following features: - the ground material has a particle size of 1 mm to 50 mm, preferably 1 to 30 mm, more preferably 4 to 20 mm, - implementation with a mass ratio of water / membrane material of 11 to 1, - the membrane material is introduced into a mill supplied with water via a mill loading hopper directly or by a conveyor belt.

5. A treatment method according to any one of claims 1 to 4, characterized in that step b) of acid washing comprises at least one of the following characteristics: - the acidic liquid medium is an aqueous solution of at least one acid selected from an organic acid and a mineral acid, - the acidic liquid medium includes at least one acid chosen from hydrochloric acid, citric acid, oxalic acid, - the acidic liquid medium has a pH of 0 to 4, preferably from 0 to 2, - implementation under agitation, - implementation with a mass ratio of acidic liquid medium / ground membrane material of 10 to 1, - implementation for 0.5 to 4 hours.

6. Processing method according to any one of the preceding claims, characterized in that step c) of rinsing comprises at least one of the following features: - implementation with a mass ratio of water / ground membrane material of 50 to 1, - implementation under agitation, - implementation for 0.5 to 4 hours, - implementation by contacting the ground material with water until the pH of the water from the contact is identical to the pH of the water before contact.

7. Processing method according to any one of the preceding claims, characterized in that step d) comprises at least one of the following characteristics: - implementation at a temperature of 40 to 100 °C, preferably 40 to 80 °C, - a drying time of 0.5 to 4 hours, - implementation in the presence of an airflow at a temperature of 40 to 100 °C, - at the end of step d), the ground membrane material has a water content of less than 1% by mass.

8. Processing method according to any one of the preceding claims, characterized in that upstream of step a) underwater grinding, the process includes a step e) of dismantling the end-of-life filtration modules containing said used membrane material during which said modules are dismantled and the used membrane material is recovered.

9. Processing method according to any one of the preceding claims, characterized in that between step c) and step d), the process includes a step f) of draining the ground membrane material from step c).

10. Processing method according to any one of the preceding claims, characterized in that it comprises, downstream of step a), a conditioning step of the ground membrane material during which the ground membrane material is placed inside a woven material container, optionally of liquid-permeable woven material.

11. Processing method according to the preceding claim, characterized in that at least one of steps b) to d) is carried out while the ground membrane material is inside the container made of woven material permeable to liquids.

12. Installation for processing used membrane material from an end-of-life filtration module comprising: - an optional section (E) for dismantling filtration modules, - an underwater grinding section (A) for the membrane material implemented in at least one water-fed grinder, - an acid washing section (B) for the ground membrane material comprising at least one acid liquid feed system, - a water rinsing section (C) for the ground membrane material comprising at least one water feed system, - an optional draining section (F) for the ground membrane material from the rinsing section, - a drying section (D) for the ground membrane material from the rinsing section or the optional draining section (F), - an optional conditioning section for the ground membrane material,- means of transporting the membrane material from one section to another to implement the process according to any one of the preceding claims.

13. A processing installation according to claim 12 comprising at least one of the following features: - the underwater grinding section comprises at least one water mill loading hopper, and optionally a conveyor belt, - the transport means comprise one or more of the following transport systems: a conveyor belt, a screw conveyor, a hopper, - The acid washing section includes at least one system for recirculating the acidic liquid medium used, - the water rinsing section includes at least one system for recirculating used water and / or a system for controlling the pH of the water exiting the rinsing section, - the conditioning section includes at least one loading station for the ground membrane material inside a container made of woven material, optionally made of liquid-permeable woven material, - In the acid washing section, the ground membrane material is placed inside a container made of woven material permeable to liquids, - in the water rinsing section, the ground membrane material is placed inside a container made of woven material permeable to liquids.

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