Purification and recovery method of waste liquid containing N-methyl pyrrolidone and waste liquid purification device

Abstract

The embodiment of the invention discloses a purification and recovery method of waste liquid containing N-methyl pyrrolidone and a waste liquid purification device. A specific embodiment of the method comprises the following steps: pre-treating the waste liquid containing N-methyl pyrrolidone to obtain a pre-treated component; carrying out dehydration treatment on the pretreated component through a preferential permeable membrane system to obtain a dehydrated component; separating the dehydrated component through a rectifying tower to obtain a tower top gas-phase light component and a tower kettle heavy component, heating and condensing the pretreated component by the tower top gas-phase light component in a preferential permeable membrane system in a waste heat recovery manner, and refluxing to the preferential permeable membrane system to be subjected to dehydration treatment together with the pretreated component to form a cycle; carrying out purification treatment on the tower kettle heavy component to obtain a purified component; and carrying out metal ion removal treatment on the purified component to obtain the electronic-grade N-methyl pyrrolidone solvent. According to the embodiment, the energy consumption is reduced, and meanwhile, the recovery efficiency and the purity of the N-methyl pyrrolidone are improved.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the technical field of chemical waste liquid treatment and resource recovery, and specifically to a purification and recovery method for waste liquid containing N-methylpyrrolidone and a waste liquid purification device. Background Art

[0002] In modern industry, N-methylpyrrolidone is a key chemical raw material. Due to its high boiling point, strong polarity, low volatility and good chemical stability, it is widely used in lithium-ion batteries, polymer synthesis, electronic component cleaning and other fields. In the production of lithium-ion batteries, N-methylpyrrolidone is an excellent solvent for the preparation of electrode materials, which can ensure the performance of electrode slurry. During polymer synthesis, it can create suitable conditions for the reaction and improve the quality of the polymer. In the cleaning of electronic components, its high solubility and low residue can effectively remove dirt and impurities. However, large-scale production in these industries leads to the generation of a large amount of waste liquid containing N-methylpyrrolidone. The waste liquid has complex composition and many impurities. If it is discharged directly, it will not only cause a waste of resources, but also cause serious pollution to the environment. Therefore, it is of great economic and environmental significance to purify and recover N-methylpyrrolidone waste liquid.

[0003] At present, the purification methods of N-methylpyrrolidone-containing waste liquid mainly include adsorption and distillation. The adsorption method is to use an adsorbent to adsorb N-methylpyrrolidone, and then desorb and recover it. The distillation method mostly adopts the traditional distillation technology of three groups of towers in series, which mainly passes the N-methylpyrrolidone-containing waste liquid into the first dehydration distillation tower to remove part of the water and impurities, and the obtained N-methylpyrrolidone crude product is transported to the second dehydration distillation tower to remove the remaining water and some low-boiling impurities, and extract the heavy components. Finally, the new heavy components are sent to the distillation tower again to separate the high-boiling substances, so as to obtain the purified N-methylpyrrolidone solvent.

[0004] However, when the above method is used to recycle N-methylpyrrolidone waste liquid, the following technical problems often occur:

[0005] The adsorption capacity of the adsorption method is limited, the adsorbent needs to be replaced frequently, and the desorption process is complicated to operate, resulting in the low efficiency of the adsorption method for recovering N-methylpyrrolidone.

[0006] The distillation method involves connecting multiple distillation towers in series, which results in high energy consumption and unsatisfactory removal of some trace metal elements, resulting in a low purity of the purified N-methylpyrrolidone solvent.

[0007] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure concept and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. Summary of the invention

[0008] The content of this disclosure is used to introduce concepts in a brief form, which will be described in detail in the detailed implementation section below. The content of this disclosure is not intended to identify the key features or essential features of the technical solution claimed for protection, nor is it intended to limit the scope of the technical solution claimed for protection.

[0009] Some embodiments of the present disclosure provide a method for purifying and recovering waste liquid containing N-methylpyrrolidone and a waste liquid purification device to solve one or more of the technical problems mentioned in the above background technology section.

[0010] In a first aspect, some embodiments of the present disclosure provide a method for purifying and recovering waste liquid containing N-methylpyrrolidone, the method comprising: pretreating the waste liquid containing N-methylpyrrolidone to obtain a pretreated component; dehydrating the pretreated component through a preferential water permeable membrane system to obtain a dehydrated component; separating the dehydrated component through a distillation tower to obtain a light component in a gas phase at the top of the tower and a heavy component in a bottom of the tower, wherein the light component in the gas phase at the top of the tower heats the pretreated component in the preferential water permeable membrane system by recovering waste heat, and after condensation, refluxes to the preferential water permeable membrane system to undergo dehydration treatment together with the pretreated component to form a cycle; purifying the heavy component in the bottom of the tower to obtain a purified component; and removing metal ions from the purified component to obtain an electronic grade N-methylpyrrolidone solvent.

[0011] Optionally, the above-mentioned pretreatment of the waste liquid containing N-methylpyrrolidone to obtain a pretreatment component includes: removing solid impurities, colloidal pigments and macromolecular substances in the above-mentioned waste liquid containing N-methylpyrrolidone through an ultrafiltration membrane to obtain a pretreatment component, wherein the above-mentioned pretreatment component is the waste liquid containing N-methylpyrrolidone after filtering through the above-mentioned ultrafiltration membrane.

[0012] Optionally, the above-mentioned dehydrated components are separated by a distillation tower to obtain a light component in the top gas phase and a heavy component in the bottom of the tower, including: controlling the reflux ratio of the above-mentioned distillation tower to 0.5-5, the number of tower plates to 20-50, the top temperature to 90°C-110°C, the bottom temperature to 110°C-130°C, and the absolute pressure in the tower to 5kPa-15kPa.

[0013] Optionally, the above-mentioned purification treatment of the heavy components in the bottom of the tower to obtain the purified components includes: passing the heavy components in the bottom of the tower through a membrane that preferentially permeates N-methylpyrrolidone.

[0014] Optionally, before purifying the heavy components in the bottom of the tower to obtain the purified components, the method further comprises: controlling the operating absolute pressure of the N-methylpyrrolidone-preferential membrane to be between 1000Pa and 10000Pa and the operating temperature to be between 70°C and 90°C.

[0015] Optionally, the above-mentioned metal ion removal treatment of the purified components to obtain electronic grade N-methylpyrrolidone solvent includes: condensing the purified components; passing the purified components through a metal ion removal membrane to obtain electronic grade N-methylpyrrolidone solvent.

[0016] Optionally, the method further comprises: returning the light gaseous component at the top of the tower obtained after distillation to the preferential water permeable membrane system, and heating the pretreated component by utilizing the waste heat of the light gaseous component at the top of the tower; and preheating the pretreated component to 40°C to 60°C.

[0017] Optionally, the above-mentioned pretreatment components are dehydrated through a preferentially water-permeable membrane system to obtain dehydrated components, including: controlling the operating temperature of the preferentially water-permeable membrane to 40°C to 60°C and the working absolute pressure to 1000Pa to 10000Pa; passing the above-mentioned pretreatment components through the preferentially water-permeable membrane.

[0018] Optionally, the metal ion removal membrane is prepared; and the metal ion removal membrane is prepared by the following steps: hydrophilic modification of a porous polytetrafluoroethylene membrane to obtain a hydrophilic base membrane; immersing an iminodiacetic acid chelating resin in an ethanol solution of ethylenediaminetetraacetic acid dianhydride to perform amino functionalization modification to obtain a functionalized chelating resin; mixing the functionalized chelating resin with mesoporous silica nanoparticles, grinding and sieving, to obtain a powder in which mesoporous silica is uniformly loaded on the surface of the chelating resin; mixing the powder with a polypropylene and polystyrene-butadiene copolymer emulsion, and vacuum degassing to form a coating liquid; uniformly coating the coating liquid on the base membrane to obtain a chelating membrane; washing the chelating membrane with a mixed solution of electronic grade isopropyl alcohol and ultrapure water to obtain a semi-finished metal ion removal membrane; drying the semi-finished metal ion removal membrane to obtain a finished metal ion removal membrane.

[0019] In a second aspect, some embodiments of the present disclosure provide a waste liquid purification device, which includes: a preferentially water permeable membrane system and a distillation tower, wherein the distillation tower is used to treat the waste liquid treated by the preferentially water permeable membrane system; the device is configured to be able to implement any method described in the first aspect.

[0020] The above-mentioned various embodiments of the present disclosure have the following beneficial effects: through the purification and recovery methods of N-methylpyrrolidone-containing waste liquid of some embodiments of the present disclosure, under the premise of reducing energy consumption, the recovery efficiency and the purity of the recovered N-methylpyrrolidone are improved. Specifically, the reason why the energy consumption of recovering N-methylpyrrolidone is high but the recovery efficiency and the purity of the recovered N-methylpyrrolidone are not high is that the purification method of the waste liquid containing N-methylpyrrolidone mainly uses adsorption method and distillation method. The adsorption method is to use an adsorbent to adsorb N-methylpyrrolidone, and then desorb and recover it, but the adsorption capacity of the adsorption method is limited, and the adsorbent needs to be replaced frequently, and the desorption process is complicated to operate, resulting in the low efficiency of the adsorption method for recovering N-methylpyrrolidone. The distillation method mostly adopts the traditional distillation technology of three groups of towers connected in series, mainly passing the N-methylpyrrolidone-containing waste liquid into the first dehydration distillation tower to remove part of the water and impurities, and the obtained N-methylpyrrolidone crude product is transported to the second dehydration distillation tower to remove the remaining water and some low-boiling impurities, and extract the heavy components. Finally, the new heavy components are sent to the distillation tower again to separate the high-boiling substances, thereby obtaining the purified N-methylpyrrolidone solvent. However, the distillation method will result in high energy consumption due to the series connection of multiple groups of distillation towers, and the removal effect of some trace metal elements is not ideal, resulting in the low purity of the purified N-methylpyrrolidone solvent. Based on this, some embodiments of the present disclosure disclose a method for purifying and recovering N-methylpyrrolidone-containing waste liquid, the method comprising: pre-treating the N-methylpyrrolidone-containing waste liquid to obtain a pre-treated component; dehydrating the pre-treated component through a preferential water-permeable membrane system to obtain a dehydrated component; separating the dehydrated component through a distillation tower to obtain a light component in the gas phase at the top of the tower and a heavy component in the bottom of the tower, wherein the light component in the gas phase at the top of the tower heats the pre-treated component in the preferential water-permeable membrane system by recovering waste heat, condenses and refluxes to the preferential water-permeable membrane system to form a cycle with the pre-treated component; purifying the heavy component in the bottom of the tower to obtain a purified component; and removing metal ions from the purified component to obtain an electronic grade N-methylpyrrolidone solvent. Also because the method is based on membrane separation technology as the core and distillation technology as the auxiliary, it does not require frequent replacement of the adsorbent and does not require desorption operations. The distillation tower only plays an auxiliary role, so the energy consumption is relatively low. Demetallization will also be performed before the finished product is obtained. Thus, the energy consumption is reduced while the purity and recovery efficiency of N-methylpyrrolidone are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and that components and elements are not necessarily drawn to scale.

[0022] Figure 1 is a flow chart of some embodiments of the method for purifying and recovering waste liquid containing N-methylpyrrolidone according to the present disclosure;

[0023] Figure 2 It is a partial structural schematic diagram of a waste liquid purification device according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0024] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0025] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other.

[0026] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0027] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0028] The names of the messages or information exchanged between multiple devices in the embodiments of the present disclosure are only used for illustrative purposes and are not used to limit the scope of these messages or information.

[0029] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0030] Figure 1 The process 100 of some embodiments of the method for purifying and recovering N-methylpyrrolidone-containing waste liquid according to the present disclosure is shown. The method for purifying and recovering N-methylpyrrolidone-containing waste liquid comprises the following steps:

[0031] Step 101, pre-treating the waste liquid containing N-methylpyrrolidone to obtain a pre-treated component.

[0032] In certain embodiments, the waste liquid containing N-methyl pyrrolidone can be pre-treated to obtain a pre-treated component. The above-mentioned pre-treatment can be filtering out solid impurities, colloidal pigments and macromolecular substances contained in the waste liquid containing N-methyl pyrrolidone. The above-mentioned pre-treated component can be the waste liquid containing N-methyl pyrrolidone after filtering out solid impurities, colloidal pigments and macromolecular substances. A circulating pump can be used to provide a driving force for the flow of the waste liquid containing N-methyl pyrrolidone. In practice, the solid impurities, colloidal particles, etc. in the waste liquid can be separated from N-methyl pyrrolidone by the centrifugal force generated by the high-speed rotation of the centrifuge. Solid impurities and colloidal particles with higher density move to the bottom of the centrifuge under the action of centrifugal force, while N-methyl pyrrolidone with lower density is located on the upper layer.

[0033] In some optional implementations of some embodiments, the above pretreatment can be achieved by an ultrafiltration membrane. The material of the above ultrafiltration membrane can be one of polysulfone, polyethersulfone, polyvinylidene fluoride or alumina ceramic, and the membrane pore size can be 0.01 μm to 0.1 μm. The above ultrafiltration membrane uses pore size to filter impurities, is simple to operate, and has obvious separation effect.

[0034] In practice, the waste liquid containing N-methylpyrrolidone can be pretreated by the following steps to obtain a pretreated component:

[0035] In the first step, the circulation pump is turned on to allow the waste liquid containing N-methylpyrrolidone to flow to the ultrafiltration membrane.

[0036] The second step is to control the flow rate of the circulation pump so that the waste liquid containing N-methylpyrrolidone can pass through the ultrafiltration membrane at an appropriate speed. For example, the flow rate of the circulation pump can be controlled to 1m 3 / h. The flow rate of the circulation pump is not specifically limited here, as long as it can filter out solid impurities, colloidal pigments and macromolecular substances in the waste liquid containing N-methylpyrrolidone without damaging the ultrafiltration membrane.

[0037] In the third step, a pre-treated component is obtained on the permeate side of the ultrafiltration membrane.

[0038] Step 102, dehydrating the pretreated component through a preferentially water-permeable membrane system to obtain a dehydrated component.

[0039] In some embodiments, the pretreatment components can be dehydrated through a preferential water permeable membrane system to obtain dehydrated components. The dehydrated components are obtained by dehydrating the pretreatment components. Among them, the preferential water permeable membrane system is a combination of multiple components with a preferential water permeable membrane as the core. The preferential water permeable membrane system may include a preferential water permeable membrane, a heat exchanger, and a vacuum pump. Among them, the heat exchanger can be connected to the preferential water permeable membrane and the distillation tower. The heat exchanger can be used to heat the pretreatment components, and its heat source can come from the gas phase components flowing from the top of the distillation tower. The vacuum pump can be connected to one side of the preferential water permeable membrane. The vacuum pump can create a negative pressure environment on one side of the preferential water permeable membrane, so that the moisture in the pretreatment components can have the power to pass through the preferential water permeable membrane. The preferential water permeable membrane system can make the moisture contained in the pretreatment components preferentially permeable.

[0040] Optionally, the preferential water permeable membrane system may include a preferential water permeable membrane. The preferential water permeable membrane may be a pervaporation membrane. The preferential water permeable membrane may be a polyvinyl alcohol (PVA) membrane, a polyimide (PI) membrane, a chitosan membrane, or an inorganic molecular sieve membrane. Further, the PVA membrane, the PI membrane, or the chitosan membrane is a composite membrane structure including a support layer and a selection layer. The material of the support layer may include, but is not limited to, any one of the following: polyethersulfone (PES), polysulfone (PSU), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and an inorganic ceramic membrane. The material of the selection layer is PVA, PI, chitosan, and one of the cross-linked modified polymers. Since the preferential water permeable membrane may be a pervaporation membrane, a pressure difference is required on both sides thereof for normal use. Therefore, the preferential water permeable membrane may be connected to a vacuum system, and the vacuum system may create a negative pressure environment on one side of the preferential water permeable membrane to provide a driving force. The operating temperature of the preferential water permeable membrane may be controlled at 40°C to 60°C, and the working absolute pressure may be controlled at 1000Pa to 10000Pa. The above-mentioned working absolute pressure is equal to the absolute pressure of the above-mentioned vacuum system.

[0041] In practice, the above-mentioned pre-treated components can be dehydrated through a preferentially permeable membrane system by the following steps:

[0042] In the first step, the pretreatment components are preheated to 40°C to 60°C.

[0043] The second step is to control the absolute pressure of the vacuum system to 1000Pa to 10000Pa.

[0044] The third step is to pass the preheated pretreated components to the above-mentioned preferential water permeable membrane system.

[0045] The fourth step is to extract the dehydrated components on the retentate side of the preferentially permeable membrane system.

[0046] Step 103, separating the dehydrated components through a distillation tower to obtain light components in the gas phase at the top of the tower and heavy components in the bottom of the tower.

[0047] In some embodiments, the dehydrated components can be separated by a distillation tower to obtain a light component in the gas phase at the top of the tower and a heavy component in the bottom of the tower. The function of the distillation tower is to heat the dehydrated components so that the substances contained in the dehydrated components are separated into a light component in the gas phase at the top of the tower and a heavy component in the bottom of the tower due to the difference in boiling points. It should be noted that the distillation tower can be a plate tower or a packed tower, and a plate tower is taken as an example here.

[0048] Optionally, the reflux ratio of the above-mentioned distillation tower is controlled at 0.5-5, the number of plates is 20-50, the top temperature is 90°C-110°C, the bottom temperature is 110°C-130°C, and the absolute pressure in the tower is 5kPa-15kPa. Among them, the reason for setting the above-mentioned reflux ratio at 0.5-5 is that such a setting can ensure both the purity of the distillation product and the economic benefit. Compared with a too high reflux ratio, it is more energy-efficient in the range of 0.5-5. When the reflux ratio is too high (for example, greater than 5), more steam is required to heat and vaporize the liquid, and more cooling medium is required to condense the reflux liquid, which consumes a lot of energy. In the range of 0.5-5, while ensuring the separation effect, the amount of steam and cooling medium is relatively reasonable. The number of plates of 20-50 helps to maintain the stable operation of the distillation tower. When the operating conditions such as feed composition, flow rate or temperature fluctuate to a certain extent, the distillation tower with 20-50 plates has a certain buffering capacity. Due to the sufficient number of plates, the contact and mass transfer process between gas and liquid in the tower is relatively stable, and the product quality will not drop significantly immediately due to small fluctuations. From the perspective of cooling, it is relatively easy to achieve effective cooling when the tower top temperature is between 90℃ and 110℃. In industrial production, cooling water is usually used as a cooling medium, and its temperature is generally around 30℃. When the tower top temperature is between 90℃ and 110℃, there is a large temperature difference between the tower top temperature and the cooling water, which makes the cooling process easier to carry out, and can efficiently condense the tower top steam into liquid, reducing the amount of cooling medium and the load of cooling equipment. For the separation of impurities and target products with similar boiling points, it is necessary to avoid excessively high temperatures that cause the target product to be purified to vaporize together with the impurities. By controlling the tower bottom temperature at 110℃ to 130℃, it can be ensured in practice that the impurities are fully vaporized, and the purity of the target product can be improved. In the pressure range of 5kPa to 15kPa, the boiling points of each component in the mixture can be adjusted to optimize the separation effect. For some mixtures whose relative volatility changes significantly with pressure, such as some hydrocarbon mixtures, their relative volatility can be changed by adjusting the pressure. For example, lowering the pressure can make the light component easier to vaporize and increase the degree of separation between light and heavy components. In the pressure range of 5kPa to 15kPa, the pressure can be flexibly adjusted according to the specific mixture and separation requirements to improve the separation capacity of the distillation tower.

[0049] In practice, the above dehydrated components can be separated by a distillation tower through the following steps:

[0050] In the first step, the reflux ratio of the distillation tower is controlled at 0.5-5, the number of plates is 20-50, the top temperature is 90-110°C, the bottom temperature is controlled at 110-130°C, and the absolute pressure is 5kPa-15kPa.

[0051] In the second step, the dehydrated components are introduced into the distillation tower.

[0052] In the third step, in response to the generation of a light gaseous component at the top of the distillation tower, the light gaseous component at the top of the tower is passed into the preferential water permeable membrane system. The light gaseous component at the top of the tower is a low-boiling impurity that evaporates due to continuous heating and temperature rise of the dehydrated component in the distillation tower. The light gaseous component at the top of the tower also contains a small amount of N-methylpyrrolidone. In response to the completion of the evaporation of the low-boiling impurities, a heavy component at the bottom of the distillation tower is obtained. The heavy component at the bottom of the tower is the dehydrated component after the low-boiling impurities are separated by heating.

[0053] It should be noted that the preferential water permeable membrane system may include a heat exchanger. The gas phase light component introduced into the preferential water permeable membrane system may heat the pretreatment component through the heat exchanger to achieve energy recovery. The gas phase light component introduced into the preferential water permeable membrane system may be condensed and refluxed into the pretreatment component to continue to participate in the circulation.

[0054] Step 104, purifying the heavy components in the bottom of the tower to obtain purified components.

[0055] In some embodiments, the heavy components in the tower bottom can be purified to obtain purified components. Since the above-mentioned distillation tower only separates low-boiling impurities, the heavy components in the tower bottom may also contain other impurities and need to be further refined. Methods such as adsorption and redistillation can be used. For example, an activated carbon adsorption column is used to pass the heavy components in the tower bottom through the adsorption column to remove other impurities. The size of the adsorption column and the amount of activated carbon used are determined according to the quality requirements and impurity content of the product.

[0056] In some optional implementations of some embodiments, the above-mentioned purification treatment can be achieved by preferentially permeating N-methylpyrrolidone membrane. The above-mentioned preferentially permeating N-methylpyrrolidone membrane can be a pervaporation membrane. The above-mentioned preferentially permeating N-methylpyrrolidone membrane can allow N-methylpyrrolidone in the waste liquid to preferentially permeate, so that the purified components can be obtained on the permeation side of the above-mentioned preferentially permeating N-methylpyrrolidone membrane. The above-mentioned purified components are the heavy components in the bottom of the tower after being treated by the above-mentioned preferentially permeating N-methylpyrrolidone membrane.

[0057] Optionally, since the preferentially permeable N-methylpyrrolidone membrane can be a pervaporation membrane, a pressure difference is required on both sides for normal use. Therefore, the preferentially permeable N-methylpyrrolidone membrane can be connected to a vacuum system, and the vacuum system creates a negative pressure environment on one side of the preferentially permeable N-methylpyrrolidone membrane to provide a driving force. The operating absolute pressure of the preferentially permeable N-methylpyrrolidone membrane can be controlled at 1000Pa to 10000Pa and the operating temperature at 70°C to 90°C, wherein the working absolute pressure is equal to the absolute pressure of the vacuum system.

[0058] Optionally, a condenser may be connected to the permeation side of the above-mentioned preferentially permeable N-methylpyrrolidone membrane. The reason is that the purified components obtained on the permeation side of the above-mentioned preferentially permeable N-methylpyrrolidone membrane are in a vapor state. Connecting a condenser to the permeation side of the above-mentioned preferentially permeable N-methylpyrrolidone membrane can obtain liquid purified components, which is convenient for the next step of operation.

[0059] In practice, the heavy components in the bottom of the tower can be purified by the following steps:

[0060] The first step is to control the operating temperature of the above-mentioned N-methylpyrrolidone preferentially permeable membrane to be between 70°C and 90°C.

[0061] The second step is to control the absolute pressure of the vacuum system to be between 1000Pa and 10000Pa.

[0062] The third step is to control the recombinant fraction in the tower bottom to flow toward the N-methylpyrrolidone preferentially permeable membrane.

[0063] The fourth step is to obtain a purified component on the permeation side of the N-methylpyrrolidone-preferentially permeable membrane, wherein the purified component is a heavy component in the bottom of the tower after being treated by the N-methylpyrrolidone-preferentially permeable membrane, and its components include N-methylpyrrolidone and metal ion impurities.

[0064] It should be noted that, in the third step, a circulating pump may be used to drive the recombinant fraction in the bottom of the tower to flow toward the N-methylpyrrolidone-preferentially permeable membrane.

[0065] Optionally, the above-mentioned purification and recovery method of N-methylpyrrolidone-containing waste liquid may also include preparing a preferentially permeable N-methylpyrrolidone membrane. Among them, the preferentially permeable N-methylpyrrolidone membrane is a separation membrane with special selectivity. Its principle is based on the physical or chemical interaction between the membrane material and the N-methylpyrrolidone molecules, so that in the mixture, the N-methylpyrrolidone molecules can preferentially permeate the membrane compared to other molecules. This interaction may include solubility differences, affinity differences, etc. For example, from the solubility aspect, if the membrane material has a higher solubility for N-methylpyrrolidone, N-methylpyrrolidone is easier to diffuse in the membrane, thereby preferentially permeating. In practice, the preferentially permeable N-methylpyrrolidone membrane can be prepared by thermal crosslinking. The commonly used crosslinking method is to use end-hydroxyl polydimethylsiloxane (PDMS) and tetraethyl orthosilicate (TEOS), under the catalysis of dibutyltin dilaurate (DBTDL), after high temperature heating and long-term crosslinking, to prepare a stable performance preferentially permeable N-methylpyrrolidone membrane. PDMS has a very long silicon-oxygen chain skeleton structure, which is spiral in shape. At the same time, there are many alkyl groups in its side chains, so the PDMS membrane exhibits extremely strong hydrophobicity. In addition, the long chain structure in the PDMS polymer network and the high flexibility of the main chain give the polymer chain high flexibility, which allows organic molecules to diffuse and transport in the polymer matrix. Therefore, the PDMS membrane exhibits excellent performance in the process of filtering N-methylpyrrolidone.

[0066] In some optional implementations of some embodiments, the method for preparing a membrane that preferentially permeates N-methylpyrrolidone may include the following steps:

[0067] In the first step, polytetrafluoroethylene (PTFE) is immersed in an ethanol solution containing 3-aminopropyltriethoxysilane (APTES) and reacted at 40°C for 3 hours to obtain a support layer with surface grafted amino groups.

[0068] In the second step, the support layer with amino groups grafted on the surface is rinsed in an ethanol solution to remove unreacted 3-aminopropyltriethoxysilane.

[0069] In the third step, the support layer with the surface grafted with amino groups after being washed in the second step is placed in an oven at 60° C. and dried for 2 hours to obtain a dry support layer.

[0070] In the fourth step, the polydimethylsiloxane monomer is added into the n-heptane solution to obtain a polydimethylsiloxane solution with a polydimethylsiloxane monomer mass concentration of 5% and uniform distribution.

[0071] The fifth step is to add the MFI zeolite molecular sieve into the above polydimethylsiloxane solution and perform ultrasonic dispersion for 1 hour to obtain a suspension.

[0072] In the sixth step, a crosslinking agent (the mass ratio of monomer to crosslinking agent is 10:1) is slowly added to the above suspension, and stirring is continued to ensure sufficient crosslinking to obtain a selection layer mixed solution. The crosslinking agent can be a silane coupling agent.

[0073] In the seventh step, the selective layer mixture is evenly coated on the dry support layer by spin coating to obtain a support layer coated with a wet film.

[0074] In the eighth step, the support layer coated with the wet film is placed in an oven at 80° C. for curing for 6 hours to obtain a finished product of a preferentially permeable N-methylpyrrolidone film.

[0075] It should be noted that, in the first step, the polytetrafluoroethylene (PTFE) is immersed in an ethanol solution containing 3-aminopropyltriethoxysilane (APTES), wherein the mass fraction of the ethanol solution is 5%.

[0076] In the fifth step, the MFI zeolite molecular sieve is added into the polydimethylsiloxane solution, wherein the mass fraction of the MFI zeolite molecular sieve in the polydimethylsiloxane solution is 10%.

[0077] In the seventh step, the selective layer mixture is evenly coated on the dry support layer by spin coating to obtain a support layer coated with a wet film, wherein the spin coating speed is 2000 r / min, the spin coating time is 30 s, and the thickness of the wet film coated on the support layer is 50 μm to 80 μm.

[0078] The above-mentioned first step to the eighth step and their related contents, as an inventive point of the embodiment of the present disclosure, solve the technical problem of "low separation efficiency of preferentially permeable N-methylpyrrolidone membrane". The factors that lead to the low separation efficiency of preferentially permeable N-methylpyrrolidone membrane are as follows: At present, the commonly used method for preparing preferentially permeable N-methylpyrrolidone membrane is thermal crosslinking. The commonly used crosslinking method is to use polydimethylsiloxane (PDMS) with terminal hydroxyl groups and tetraethyl orthosilicate (TEOS), and under the catalysis of dibutyltin dilaurate (DBTDL), after high temperature heating and long-term crosslinking, to prepare a stable performance preferentially permeable N-methylpyrrolidone membrane. When using the thermal crosslinking method to prepare a preferentially permeable N-methylpyrrolidone membrane, due to the limitation of the structure of the polymer itself, the performance of the membrane has a certain bottleneck, and there is a "trade off" effect between the permeability and selectivity of the membrane, that is, it is difficult to improve the selectivity and permeability at the same time, so the separation effect of the pure PDMS membrane still cannot meet the needs of actual production. If the above factors are solved, the effect of improving the separation efficiency of the preferentially permeable N-methylpyrrolidone membrane can be achieved. In order to achieve this effect, the present disclosure further provides a method for preparing a membrane that preferentially permeates N-methylpyrrolidone, in which porous particles are added to produce a film layer with selective permeability, which is no longer limited by the structure of the polymer itself. The organic affinity of the porous particles can ensure that the organic phase (such as N-methylpyrrolidone) passes preferentially, thereby improving the membrane separation performance. As a result, the separation efficiency of the membrane that preferentially permeates N-methylpyrrolidone is improved.

[0079] Step 105, performing metal ion removal treatment on the purified component to obtain electronic grade N-methylpyrrolidone solvent.

[0080] In some embodiments, the purified components can be treated to remove metal ions to obtain electronic grade N-methylpyrrolidone solvent. Among them, the above-mentioned electronic grade N-methylpyrrolidone solvent is an N-methylpyrrolidone solvent with a purity requirement of more than 99.9%. Electronic grade N-methylpyrrolidone solvent is usually used in precision manufacturing in the electronics industry. In the precision manufacturing process of the electronics industry, even trace amounts of impurities may have a serious impact on the performance of electronic products. For example, in the semiconductor photolithography process, high-purity N-methylpyrrolidone can ensure the precise removal of photoresist, while impurities may cause photoresist residues and affect the pattern accuracy of the chip. In practice, the above-mentioned purified components can be treated to remove metal ions with ion exchange resin. Ion exchange resin is a polymer material with exchangeable ions. Cationic exchange resin contains acidic groups (such as sulfonic acid group -SO3H, carboxyl group -COOH), and the hydrogen ions (H+) on these acidic groups can react with metal cations (such as Na+, Ca+) in the waste liquid. 2+, Fe3+, etc.) for exchange. Anion exchange resin contains basic groups that can exchange with anions (including some metal complex anions) in the above-mentioned purified components. Through the ion exchange process, metal ions are removed from the above-mentioned purified components.

[0081] In some optional implementations of some embodiments, the purified components may be passed through a metal ion removal membrane to obtain an electronic grade N-methylpyrrolidone solvent.

[0082] In practice, the purified components can be treated to remove metal ions by the following steps:

[0083] In the first step, the purified component is passed through the above-mentioned metal ion removal membrane.

[0084] In the second step, electronic grade N-methylpyrrolidone is collected on the permeate side of the metal ion removal membrane.

[0085] It should be noted that, in the first step above, a circulating pump can be used to provide power to the purified components.

[0086] In the second step, a product tank may be connected to the permeate side of the metal ion removal membrane. The product tank may be used to contain electronic grade N-methylpyrrolidone.

[0087] Alternatively, the above-mentioned purification and recovery method of N-methylpyrrolidone-containing waste liquid can also include the preparation of metal ion removal membrane. The above-mentioned metal ion removal membrane is a separation membrane with special selectivity, which can selectively intercept metal ions in a solution system through a physical or chemical mechanism, and allow other substances (such as solvents, some organic matter, etc.) to pass through, thereby achieving the purpose of reducing the metal ion content in the solution. In practice, the metal ion removal membrane can be prepared by a blending method, and its operating steps are as follows: a solution containing a chelating group is evenly mixed with a polymer solution, and then the mixed solution is poured into a mold (such as a glass flat plate mold), and the solution is spread on the mold surface with a scraper to form a liquid layer. Then it is placed in a well-ventilated environment, and along with the evaporation of the solvent, the solution gradually solidifies to form a film. Wherein, the above-mentioned solution containing a chelating group can be an ethylenediaminetetraacetic acid solution. The above-mentioned polymer solution can be a polyvinyl alcohol solution.

[0088] In some optional implementations of some embodiments, the method for preparing a metal ion removal membrane may include the following steps:

[0089] In the first step, the polytetrafluoroethylene membrane is hydrophilically modified to obtain a hydrophilic base membrane.

[0090] In the second step, the iminodiacetic acid chelating resin is immersed in an ethanol solution of ethylenediaminetetraacetic acid dianhydride to perform amino functionalization modification to obtain a functionalized chelating resin with increased chelating sites. The chelating site refers to a specific atom or atomic group in the chelating agent molecule that can coordinate with metal ions to form a chelate bond.

[0091] The third step is to mix the functionalized chelating resin and the mesoporous silica nanoparticles, grind and sieve them to obtain a powder in which the mesoporous silica is uniformly loaded on the surface of the chelating resin, wherein the powder further improves the adsorption performance.

[0092] The fourth step is to mix the above powder with polypropylene and polystyrene-butadiene copolymer emulsion, and perform vacuum degassing to form a coating liquid.

[0093] The fifth step is to evenly coat the coating liquid on the base film to obtain a chelating film.

[0094] In the sixth step, the chelating membrane is thoroughly cleaned with a mixed solution of electronic grade isopropyl alcohol and ultrapure water to obtain a semi-finished metal ion removal membrane.

[0095] The seventh step is to dry the semi-finished metal ion removal membrane to obtain a finished metal ion removal membrane.

[0096] It should be noted that, in the first step above, the hydrophilic modification of the polytetrafluoroethylene membrane can be carried out by the following steps:

[0097] In the first step, polyvinyl alcohol (PVA) is dissolved in water to obtain a solution with a mass fraction of polyvinyl alcohol of 5 to 15%.

[0098] In the second step, the solution is coated on the surface of the polytetrafluoroethylene membrane by dip coating to obtain a polytetrafluoroethylene wet membrane.

[0099] It should be noted that during dip coating, the polytetrafluoroethylene film needs to be slowly immersed in the above solution and stay for a period of time. The above period of time can be 1 to 5 minutes. The speed when the polytetrafluoroethylene film is pulled out can be 1 to 10 cm / min. In this way, the surface of the polytetrafluoroethylene film can be evenly stained with the above solution.

[0100] The third step is to dry the wet polytetrafluoroethylene film to obtain a modified polytetrafluoroethylene film.

[0101] It should be noted that when drying the above-mentioned polytetrafluoroethylene wet film, the drying temperature can be controlled at 40°C to 80°C.

[0102] The above-mentioned first step to the seventh step and its related contents are an inventive point of an embodiment of the present disclosure, which solves the technical problem of "the metal ion removal membrane has poor effect in removing metal ions". The specific factors that lead to the poor effect of the metal ion removal membrane in removing metal ions are as follows: At present, the metal ion removal membrane is generally prepared by a blending method, and its operation steps are as follows: a solution containing a chelating group is mixed evenly with a polymer solution, and then the mixed solution is poured into a mold (such as a glass flat mold), and the solution is spread on the mold surface with a scraper to form a liquid layer. Then it is placed in a well-ventilated environment. As the solvent evaporates, the solution gradually solidifies to form a film, and the number of its active sites is small and the distribution is not reasonable enough. When in contact with metal ions, the sites that can effectively bind to metal ions are insufficient, so that a large number of metal ions cannot be captured and fixed in time, resulting in difficulty in improving the removal efficiency. If the above factors are solved, the effect of the metal ion removal membrane in removing metal ions can be improved. To this end, the present disclosure provides a polytetrafluoroethylene film modified by hydrophilicity as a base film, and directly coats the base film with a relatively soft texture itself, so as to avoid the solution being difficult to spread evenly on a hard surface when using a mold. This results in a small number of active sites on the formed membrane and an unreasonable distribution of active sites, thereby improving the effect of the metal ion removal membrane in removing metal ions.

[0103] Some preferred embodiments of the method for purifying and recovering N-methylpyrrolidone-containing waste liquid disclosed herein may include the following process:

[0104] (1) A certain amount of waste liquid containing N-methylpyrrolidone was taken for testing. It was first treated with an ultrafiltration membrane (the membrane material is an alumina ceramic membrane with a pore size of 0.05 microns) at 25°C and a pressure of 0.3 MPa to remove almost all solid particles in the waste liquid. After treatment, the solid impurity content was almost zero.

[0105] (2) The treated waste liquid enters the heat exchanger, is preheated to 45°C, and then enters the preferential water permeable membrane (the membrane material is polyvinyl alcohol membrane), where it is dehydrated at 45°C and a vacuum absolute pressure of 6000Pa, and the moisture content is reduced from 10% to below 3%.

[0106] (3) The dehydrated waste liquid enters the distillation tower with a reflux ratio of 2, a plate number of 30, a top temperature of 105°C, a bottom temperature of 115°C, and an absolute pressure of 6 kPa. At this time, there is basically no water in N-methylpyrrolidone, and most of the easily evaporable impurities are removed. The gaseous light components at the top of the tower provide heat to the heat exchanger, and the heavy components in the bottom of the tower enter the preferential N-methylpyrrolidone membrane. The operating temperature is 74°C and the vacuum absolute pressure is 2000 Pa. After purification by the preferential N-methylpyrrolidone membrane, the purity of N-methylpyrrolidone reaches more than 99.99%.

[0107] The method for preparing the N-methylpyrrolidone-preferential permeable membrane comprises the following steps:

[0108] In the first step, polytetrafluoroethylene (PTFE) is immersed in an ethanol solution (mass fraction of 5%) containing 3-aminopropyltriethoxysilane (APTES) and reacted at 40° C. for 3 hours to obtain a support layer with amino groups grafted on the surface.

[0109] In the second step, the support layer with amino groups grafted on the surface is rinsed in an ethanol solution to remove unreacted 3-aminopropyltriethoxysilane.

[0110] In the third step, the support layer with the surface grafted with amino groups after being washed in the second step is placed in an oven at 60° C. and dried for 2 hours to obtain a dry support layer.

[0111] The fourth step is to evenly distribute the polydimethylsiloxane monomer in the n-heptane solution with a mass concentration of 5 wt %.

[0112] The fifth step is to add the MFI zeolite molecular sieve into the polydimethylsiloxane solution (mass fraction is 10%) and perform ultrasonic dispersion for 1 hour to obtain a suspension.

[0113] Step 6: slowly add a crosslinking agent (the mass ratio of monomer to crosslinking agent is 10:1) to the above suspension, and continue stirring to ensure sufficient crosslinking to obtain a selection layer mixed solution.

[0114] In the seventh step, the selective layer mixture is evenly coated on the dry support layer by spin coating to obtain a support layer coated with a wet film, wherein the spin coating speed is 2000 r / min, the spin coating time is 30 s, and the thickness of the wet film coated on the support layer is 55 μm.

[0115] In the eighth step, the support layer coated with the wet film is placed in an oven at 80° C. for curing for 6 hours to obtain a finished product of a preferentially permeable N-methylpyrrolidone film.

[0116] (4) The permeation side of the preferentially permeable N-methylpyrrolidone membrane is connected to a metal ion removal membrane, wherein the metal ion removal membrane can be a metal ion chelating membrane. Finally, an electronic grade N-methylpyrrolidone solvent is obtained. After precise detection, the electronic grade N-methylpyrrolidone solvent has a purity of up to 99.995%, a metal ion content of less than 0.01 ppb, and a recovery rate of more than 80%. It is at the leading level in the electronic grade high purity standard and can effectively improve the production quality and performance of related electronic products.

[0117] Wherein, the preparation method of metal ion removal membrane comprises the following steps:

[0118] In the first step, polyvinyl alcohol (PVA) is dissolved in water to obtain a solution with a mass fraction of polyvinyl alcohol of 11%. The solution is coated on the surface of the polytetrafluoroethylene membrane by dip coating. During the dip coating, the polytetrafluoroethylene membrane is slowly immersed in the solution, left for 3 minutes, and then the polytetrafluoroethylene membrane is pulled out at a speed of 5 cm / min, so that the surface of the polytetrafluoroethylene membrane is evenly stained with the solution, and finally dried at 60°C.

[0119] In the second step, the iminodiacetic acid chelating resin is immersed in an ethanol solution of ethylenediaminetetraacetic acid dianhydride and reacted at 60°C for 4 hours to achieve amino functional modification and increase chelating sites. After the reaction is completed, the resin is filtered, washed and dried to obtain a functionalized chelating resin.

[0120] The third step is to mix the functionalized chelating resin with mesoporous silica nanoparticles (pore size 4 nm), grind them with a ball mill for 3 hours to evenly load the mesoporous silica on the surface of the functionalized chelating resin to further improve the adsorption performance, and obtain a 1200-mesh powder by sieving.

[0121] In the fourth step, the above powder is mixed with polypropylene and polystyrene-butadiene copolymer emulsion in a mass ratio of 65:7:28, kneaded at 160° C. for 5 hours, and vacuum degassed for 4 hours to form a coating liquid.

[0122] The fifth step is to evenly coat the coating liquid on the base film to obtain a chelating film.

[0123] In the sixth step, the chelating membrane is thoroughly cleaned with a mixed solution of electronic grade isopropyl alcohol and ultrapure water (60:40 / V:V) until the resistivity is greater than 18.15 MΩ·cm, thereby obtaining a semi-finished metal ion removal membrane.

[0124] The seventh step is to vacuum dry the semi-finished metal ion removal membrane to obtain a finished metal ion removal membrane.

[0125] The above-mentioned various embodiments of the present disclosure have the following beneficial effects: through the purification and recovery methods of N-methylpyrrolidone-containing waste liquid of some embodiments of the present disclosure, under the premise of reducing energy consumption, the recovery efficiency and the purity of the recovered N-methylpyrrolidone are improved. Specifically, the reason why the energy consumption of recovering N-methylpyrrolidone is high but the recovery efficiency and the purity of the recovered N-methylpyrrolidone are not high is that the purification method of the waste liquid containing N-methylpyrrolidone mainly uses adsorption method and distillation method. The adsorption method is to use an adsorbent to adsorb N-methylpyrrolidone, and then desorb and recover it, but the adsorption capacity of the adsorption method is limited, and the adsorbent needs to be replaced frequently, and the desorption process is complicated to operate, resulting in the low efficiency of the adsorption method for recovering N-methylpyrrolidone. The distillation method mostly adopts the traditional distillation technology of three groups of towers connected in series, mainly passing the N-methylpyrrolidone-containing waste liquid into the first dehydration distillation tower to remove part of the water and impurities, and the obtained N-methylpyrrolidone crude product is transported to the second dehydration distillation tower to remove the remaining water and some low-boiling impurities, and extract the heavy components. Finally, the new heavy components are sent to the distillation tower again to separate the high-boiling substances, thereby obtaining the purified N-methylpyrrolidone solvent. However, the distillation method will result in high energy consumption due to the series connection of multiple groups of distillation towers, and the removal effect of some trace metal elements is not ideal, resulting in the low purity of the purified N-methylpyrrolidone solvent. Based on this, some embodiments of the present disclosure disclose a method for purifying and recovering N-methylpyrrolidone-containing waste liquid, the method comprising: pre-treating the N-methylpyrrolidone-containing waste liquid to obtain a pre-treated component; dehydrating the pre-treated component through a preferential water-permeable membrane system to obtain a dehydrated component; separating the dehydrated component through a distillation tower to obtain a light component in the gas phase at the top of the tower and a heavy component in the bottom of the tower, wherein the light component in the gas phase at the top of the tower heats the pre-treated component in the preferential water-permeable membrane system by recovering waste heat, condenses and refluxes to the preferential water-permeable membrane system to form a cycle with the pre-treated component; purifying the heavy component in the bottom of the tower to obtain a purified component; and removing metal ions from the purified component to obtain an electronic grade N-methylpyrrolidone solvent. Also because the method is based on membrane separation technology as the core and distillation technology as the auxiliary, it does not require frequent replacement of the adsorbent and does not require desorption operations. The distillation tower only plays an auxiliary role, so the energy consumption is relatively low. Demetallization will also be performed before the finished product is obtained. Thus, the energy consumption is reduced while the purity and recovery efficiency of N-methylpyrrolidone are improved.

[0126] Figure 2 It is a partial schematic diagram of a waste liquid purification device according to some embodiments of the present disclosure. Figure 2 It includes a condenser 1, a distillation tower 2, a membrane assembly 3, a vacuum system 4 and a product tank 5.

[0127] In some embodiments, the waste liquid purification device may include a preferential water permeable membrane system and a distillation tower 2. The preferential water permeable membrane system may be used to preheat the pretreated waste liquid. The heat source of the preferential water permeable membrane system may come from the gas phase light component extracted from the top of the distillation tower 2. The preferential water permeable membrane system may include a heat exchanger. The heat exchanger may allow the pretreated waste liquid and the gas phase light component to pass through at the same time to achieve the purpose of preheating the pretreated waste liquid. The preferential water permeable membrane system may include a preferential water permeable membrane. The preferential water permeable membrane may be used to remove moisture from the pretreated waste liquid. The distillation tower 2 may be used to separate the waste liquid treated with the preferential water permeable membrane. The distillation tower 2 may separate the low boiling point impurities contained in the waste liquid treated with the preferential water permeable membrane by heating. The separated gaseous low boiling point impurities will have a certain residual temperature, and will inevitably carry part of the target substance to be purified and recovered. In order to achieve efficient utilization of energy and avoid waste of the above-mentioned target substances, the above-mentioned vaporous low-boiling-point impurities can be introduced into the above-mentioned heat exchanger to heat the above-mentioned pretreated waste liquid; the above-mentioned vaporous low-boiling-point impurities after condensation can also be mixed into the pretreated waste liquid to participate in the purification and recovery cycle.

[0128] Optionally, the waste liquid purification device may include a membrane assembly 3. The membrane assembly 3 may include a first membrane, a second membrane, a third membrane and a fourth membrane. The first membrane is used to achieve the pretreatment. The second membrane may be connected to the permeation side of the first membrane. The second membrane may be used to achieve the dehydration treatment. The third membrane may be used to achieve the purification treatment. The fourth membrane may be used to achieve the metal ion removal treatment.

[0129] Optionally, the waste liquid purification device may include a condenser 1. The condenser 1 may be installed on the permeation side of the third membrane to condense the waste liquid treated by the third membrane. The third membrane may be a pervaporation membrane.

[0130] Optionally, the waste liquid purification device may include a raw material tank, an intermediate tank and a product tank 5. The raw material tank may be used to hold waste liquid containing N-methylpyrrolidone. The intermediate tank may be used to hold the purified components. The product tank 5 may be used to hold the electronic grade N-methylpyrrolidone solvent.

[0131] Optionally, the waste liquid purification device may include a circulation system. The circulation system may include a circulation pump. The number of the circulation pumps may be three, which is not specifically limited herein. The circulation system may be used to provide driving force for the waste liquid in the waste liquid purification device.

[0132] Optionally, the waste liquid purification device may include a vacuum system 4. The vacuum system 4 may include a vacuum pump. The number of the vacuum pumps may be two, which is not specifically limited herein. The vacuum system 4 may be used to provide a negative pressure environment to one side of the second membrane and one side of the third membrane, so that the permeable components contained in the waste liquid can pass through the second membrane and the third membrane by pressure difference, thereby realizing the separation function of the second membrane and the third membrane. It should be noted that the permeable components represent different components when applied to different membrane scenarios. For example, when applied to the second membrane, the permeable components represent the water contained in the waste liquid; when applied to the third membrane, the permeable components represent the N-methylpyrrolidone contained in the waste liquid.

[0133] The above-mentioned various embodiments of the present disclosure have the following beneficial effects: through the waste liquid purification device of some embodiments of the present disclosure, energy consumption can be saved and the purification efficiency can be improved. Specifically, the reason for the large energy consumption and low efficiency is that the device does not realize the recycling and reuse of energy and resources. Based on this, the waste liquid purification device of the embodiment of the present disclosure includes a preferential water permeable membrane system and a distillation tower. Also because the preferential water permeable membrane system can recover the low-boiling point impurities that are vaporized by heat in the distillation tower, and the low-boiling point impurities also contain a certain amount of target substances. Not only can the waste liquid be heated by waste heat recovery, but also the target substances contained in the low-boiling point impurities can be recovered. In this way, the effect of saving energy consumption and improving the purification efficiency is achieved.

[0134] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) and the technical solutions formed.

Claims

1. A method for purifying and recovering waste liquid containing N-methylpyrrolidone, comprising: Pre-treating the waste liquid containing N-methylpyrrolidone to obtain a pre-treated component; Dehydrating the pretreated component through a preferentially permeable membrane system to obtain a dehydrated component; The dehydrated components are separated by a distillation tower to obtain a light component in the gas phase at the top of the tower and a heavy component in the bottom of the tower, wherein the light component in the gas phase at the top of the tower heats the pre-treated components by recovering waste heat in the preferential water permeable membrane system, and then condenses and refluxes to the preferential water permeable membrane system to undergo dehydration treatment together with the pre-treated components to form a cycle; Purifying the heavy components in the tower bottom to obtain purified components; The purified components are subjected to a metal ion removal treatment to obtain an electronic grade N-methylpyrrolidone solvent.

2. The method according to claim 1, wherein: The waste liquid containing N-methylpyrrolidone is pretreated to obtain a pretreated component, comprising: The waste liquid containing N-methylpyrrolidone is passed through an ultrafiltration membrane to remove solid impurities, colloidal pigments and macromolecular substances in the waste liquid to obtain a pretreatment component, wherein the pretreatment component is the waste liquid containing N-methylpyrrolidone filtered through the ultrafiltration membrane.

3. The method according to claim 1, wherein: The dehydrated components are separated by a distillation tower to obtain light components in the gas phase at the top of the tower and heavy components in the bottom of the tower, including: The reflux ratio of the distillation tower is controlled at 0.5-5, the number of plates is controlled at 20-50, the top temperature is controlled at 90-110°C, the bottom temperature is controlled at 110-130°C, and the absolute pressure in the tower is controlled at 5kPa-15kPa.

4. The method according to claim 1, wherein: The step of purifying the heavy components in the tower bottom to obtain purified components comprises: The heavy components in the tower bottom are passed through a membrane that preferentially permeates N-methylpyrrolidone.

5. The method according to claim 4, wherein: Before purifying the heavy components in the bottom of the tower to obtain purified components, the method further comprises: The operating absolute pressure of the N-methylpyrrolidone preferentially permeable membrane is controlled to be between 1000Pa and 10000Pa, and the operating temperature is controlled to be between 70°C and 90°C.

6. The method according to claim 1, wherein: The step of removing metal ions from the purified components to obtain an electronic grade N-methylpyrrolidone solvent comprises: condensing the purified components; The purified components are passed through a metal ion removal membrane to obtain an electronic grade N-methylpyrrolidone solvent.

7. The method according to claim 1, wherein: The method further comprises: The light components of the tower top gas phase obtained after the rectification treatment are sent back to the preferential water permeable membrane system, and the waste heat of the light components of the tower top gas phase is used to heat the pre-treated components; Preheat the pretreatment components to 40°C to 60°C.

8. The method according to claim 1, wherein: The step of dehydrating the pretreated components through a preferentially permeable membrane system to obtain dehydrated components comprises: Controlling the operating temperature of the preferentially water-permeable membrane to be between 40° C. and 60° C. and the working absolute pressure to be between 1000 Pa and 10000 Pa; The pretreatment components are passed through a preferentially water permeable membrane.

9. The method according to claim 6, wherein: The method further comprises: preparing the metal ion removal membrane; And the metal ion removal membrane is prepared by the following steps: The porous polytetrafluoroethylene membrane is hydrophilically modified to obtain a hydrophilic base membrane; The iminodiacetic acid chelating resin is immersed in an ethanol solution of ethylenediaminetetraacetic acid dianhydride to carry out amino functionalization modification to obtain a functionalized chelating resin; The functionalized chelating resin and mesoporous silica nanoparticles are mixed, then ground and sieved to obtain a powder in which the mesoporous silica is uniformly loaded on the surface of the chelating resin; The powder is mixed with polypropylene and polystyrene-butadiene copolymer emulsion, and vacuum degassing is performed to form a coating liquid; Uniformly coating the coating liquid on the base film to obtain a chelating film; The chelating membrane is cleaned with a mixed solution of electronic grade isopropyl alcohol and ultrapure water to obtain a semi-finished metal ion removal membrane; The semi-finished metal ion removal membrane product is dried to obtain a finished metal ion removal membrane product.

10. A waste liquid purification device, comprising a preferentially permeable membrane system and a distillation tower, wherein: The distillation tower is connected to the retentate side of the preferentially water permeable membrane system; The distillation tower is used to treat the waste liquid treated by the preferential water permeable membrane system; The apparatus is configured to implement the method according to any one of claims 1 to 9.

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