Method for recovering and reusing solvent in production process of regenerated cellulose material

Abstract

The invention provides a method for recovering and reusing a solvent in a production process of a regenerated cellulose material, which comprises the following steps: carrying out coarse filtration treatment on waste liquid generated in the production process of the regenerated cellulose material to obtain coarse filtrate; treating the coarse filtrate by using anion exchange resin to obtain an eluent; enabling the eluent to pass through a multi-stage series membrane filtration platform so as to remove micro-nano impurities in the eluent, and separating tetrabutylammonium hydroxide, dimethyl sulfoxide and water at the same time, so as to obtain recycled tetrabutylammonium hydroxide, recycled dimethyl sulfoxide and recycled pure water; mixing the recycled tetrabutylammonium hydroxide and the recycled dimethyl sulfoxide according to a ratio, and then, applying the mixture to the production of regenerated cellulose fibers. The method is simple to operate, low in energy consumption, green and environment-friendly, and realizes high-efficiency and low-cost recovery and reutilization of the tetrabutyl ammonium hydroxide solvent and the dimethyl sulfoxide solvent.

Description

Technical Field

[0001] The invention belongs to the technical field of cellulose production and processing, and particularly relates to a method for recovering and reusing solvents from a regenerated cellulose material production process. Background Art

[0002] Cellulose is made from inexhaustible agricultural and forestry biomass in nature. It is a natural, green, degradable and environmentally friendly material. It is mainly used to produce textile fibers (regenerated cellulose materials). Its fabrics have good wear resistance, moisture absorption, air permeability and antibacterial properties. In the traditional production process of regenerated cellulose materials, a large amount of dangerous chemicals such as caustic soda, sulfuric acid, and carbon disulfide seriously corrode equipment and bring many changes to production. Sulfur-containing toxic waste gas and a large amount of zinc-containing wastewater seriously threaten the health of workers. Therefore, people have developed green, efficient, and environmentally friendly cellulose solvents represented by alkyl quaternary ammonium alkali / water-dimethyl sulfoxide, ionic liquids, N-methyl morpholine oxide, etc., and their application in cellulose spinning processes can effectively avoid the release of toxic substances in the production process of regenerated cellulose materials.

[0003] Chinese patent CN104710627B discloses a process for improving the solubility of cellulose in tetrabutylammonium hydroxide aqueous solution, indicating that the tetrabutylammonium hydroxide-water solvent system can quickly dissolve natural cellulose at room temperature. Chinese patent CN105801883B discloses a method for preparing a cellulose solution, by adding a cosolvent such as dimethyl sulfoxide to an organic alkali-water solvent system represented by tetrabutylammonium hydroxide, promoting the gentle dissolution of cellulose at room temperature, and the obtained cellulose solution can be used to prepare materials such as regenerated cellulose fibers, regenerated cellulose films, and cellulose-based composite materials. In the production process of regenerated cellulose materials, water, dilute sulfuric acid, etc. are generally used as coagulation baths. According to this process, the coagulation bath waste liquid after producing regenerated cellulose materials contains cellulose residues, regenerated cellulose, hair, tetrabutylammonium hydroxide, water, dimethyl sulfoxide, acid radical ions, colored impurities and other components. For the sake of environmental protection and cost control, the solvents generated in the production process of regenerated cellulose fibers need to be recovered and recycled.

[0004] The solvent recovery rate not only determines the production cost of cellulose materials, but also directly affects the environmental friendliness of the production process. Chinese patent CN108467347A discloses a method for electrolyzing tetrabutylammonium sulfate solution to recover tetrabutylammonium hydroxide, wherein the tetrabutylammonium sulfate aqueous solution is subjected to bipolar membrane electrodialysis in a four-compartment electrodialysis device, and this process has high processing cost and energy consumption. Chinese patent CN117658874A discloses a method for recovering dimethyl sulfoxide from polyacrylonitrile waste pulp, wherein dimethyl sulfoxide is recovered by filtration and double-effect high-temperature distillation, and its processing cost and energy consumption are high. Cellulose spinning and membrane material forming processing based on tetrabutylammonium hydroxide / water / dimethyl sulfoxide solvent system is a new environmentally friendly process. The solvent recovery processes such as tetrabutylammonium hydroxide and dimethyl sulfoxide reported in the above-mentioned documents and patents are not suitable for coagulation bath waste liquid systems containing complex components such as cellulose residues, regenerated cellulose, hair, tetrabutylammonium hydroxide, dimethyl sulfoxide, acid radical ions, and colored impurities.

[0005] Therefore, there is an urgent need for a process for recovering tetrabutylammonium hydroxide, dimethyl sulfoxide and water from the coagulation bath waste liquid generated in the production process of regenerated cellulose materials, so as to achieve low-energy consumption, low-cost, rapid and efficient recovery of tetrabutylammonium hydroxide, dimethyl sulfoxide and water, which is crucial to the industrial development of regenerated cellulose materials. Summary of the invention

[0006] In order to solve the problems of high energy consumption and high cost in the existing tetrabutylammonium hydroxide and dimethyl sulfoxide recovery process, the present invention provides a method for recovering and reusing solvents from the production process of regenerated cellulose materials. The method is simple to operate, low in energy consumption, and green and environmentally friendly, and realizes efficient and low-cost recovery of tetrabutylammonium hydroxide and dimethyl sulfoxide.

[0007] The present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for recovering and reusing solvent from a regenerated cellulose material production process, the method comprising:

[0009] (1) coarsely filtering the waste liquid generated in the production process of the regenerated cellulose material to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate;

[0010] (2) treating the crude filtrate with an anion ion exchange resin to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluent;

[0011] (3) passing the eluate through a multi-stage series membrane filtration platform to remove micro-nano impurities in the eluate, and simultaneously separating tetrabutylammonium hydroxide, dimethyl sulfoxide and water, to obtain recovered tetrabutylammonium hydroxide, recovered dimethyl sulfoxide and recovered pure water;

[0012] (4) The recovered tetrabutylammonium hydroxide and the recovered dimethyl sulfoxide are mixed in proportion and used to dissolve plant cellulose to obtain a cellulose solution. After degassing, filtering and spinning, the solution is subjected to multi-stage drawing in a coagulation bath composed of the recovered pure water and sulfuric acid. After oiling and drying, the solution is used for the production of regenerated cellulose fibers.

[0013] Furthermore, the waste liquid generated in the production process of the regenerated cellulose material is subjected to a coarse filtration treatment to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate, which specifically includes:

[0014] Passing the waste liquid generated in the production process of the regenerated cellulose material through a filter screen with a pore size of 300 to 800 meshes to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate;

[0015] The waste liquid includes coagulation bath waste liquid and / or water washing bath waste liquid.

[0016] Further, the crude filtrate is subjected to ion resin exchange treatment to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluent, which specifically includes:

[0017] The crude filtrate is subjected to ion resin exchange treatment to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluate;

[0018] Wherein, in the ion resin exchange treatment, the type of ion exchange resin includes at least one of styrene series, acrylic series, acetic acid series, epoxy series and urea-formaldehyde series;

[0019] The groups carried by the ion exchange resin include at least one of quaternary amine groups, primary amine groups, secondary amine groups and tertiary amine groups;

[0020] The particle size of the ion exchange resin is 20 to 60 meshes, and the loading amount is 0.3 to 0.9 times the volume of the exchange column;

[0021] In the ion resin exchange treatment, the flow rate of the crude filtrate is 4 to 12 times the volume of the resin bed per hour.

[0022] Further, the eluent is passed through a series of membrane platforms to remove micro-nano impurities in the eluent, and tetrabutylammonium hydroxide, dimethyl sulfoxide and water are separated at the same time to obtain recovered tetrabutylammonium hydroxide, recovered dimethyl sulfoxide and recovered pure water, specifically comprising:

[0023] The eluent is passed through a series of membrane platforms at room temperature and a pressure of 0.2 to 1 MPa to remove micro-nano impurities in the eluent, and tetrabutylammonium hydroxide, dimethyl sulfoxide and water are separated at the same time to obtain recovered tetrabutylammonium hydroxide, recovered dimethyl sulfoxide and recovered pure water.

[0024] Further, the tandem membrane platform includes any one of the following a) to f):

[0025] a) It is composed of a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:1:62:250;

[0026] b) It is composed of a microfiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:250:250;

[0027] c) It is composed of an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:150:300;

[0028] d) It is composed of a microfiltration membrane, an ultrafiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:1:62;

[0029] e) It is composed of a microfiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:250;

[0030] f) It is composed of an ultrafiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:150;

[0031] Wherein, the pore size of the microfiltration membrane is 0.1-10 μm, and the pore size of the ultrafiltration membrane is 0.001-0.1 μm.

[0032] The series membrane platforms are connected in series or parallel-series mode according to the membrane area ratio;

[0033] Preferably, the series membrane platform is formed by connecting a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane in series in a membrane area ratio of 1:1:62:250. Wherein, the series membrane is formed by connecting 1:1:N1:N2 microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membrane modules in series in a membrane area ratio of 1:1:62:250. When N(1-2)=1, the membrane area ratio of the microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, and reverse osmosis membrane module is 1:1:62:250; when N(1-2)>1, the nanofiltration membrane and each membrane module in the reverse osmosis membrane unit are connected in parallel, and then connected in series with the microfiltration membrane and the ultrafiltration membrane to form a parallel-series integrated membrane platform, and the total membrane area ratio of the microfiltration membrane unit, the ultrafiltration membrane unit, the nanofiltration membrane unit, and the reverse osmosis membrane unit module is 1:1:62:250.

[0034] Further, when the series membrane platform includes any one of a) to b) or d) to e), the eluate first passes through the microfiltration membrane in a cross-flow filtration manner;

[0035] When the tandem membrane platform comprises c) or f), the eluate first passes through the ultrafiltration membrane in a cross-flow filtration manner.

[0036] When the series membrane platform includes any one of a) to c), tetrabutylammonium hydroxide is obtained at the cutoff end of the nanofiltration membrane, dimethyl sulfoxide is obtained at the cutoff end of the reverse osmosis membrane, and pure water is obtained at the permeation end of the reverse osmosis membrane.

[0037] When the series membrane platform includes any one of d) to f), tetrabutylammonium hydroxide is obtained at the cutoff end of the nanofiltration membrane, and a dimethyl sulfoxide aqueous solution is obtained at the permeation end of the nanofiltration membrane.

[0038] Further, the material of the microfiltration membrane includes at least one of polypropylene, zirconia ceramics, titanium oxide ceramics, aluminum oxide ceramics, zirconia hybrid ceramics, titanium oxide hybrid ceramics and aluminum oxide hybrid ceramics;

[0039] The material of the ultrafiltration membrane includes at least one of zirconia ceramics, titanium oxide ceramics, aluminum oxide ceramics, zirconia hybrid ceramics, titanium oxide hybrid ceramics and aluminum oxide hybrid ceramics;

[0040] The nanofiltration membrane comprises an inorganic hybrid nanofiltration membrane with a molecular weight cutoff of 80 to 300 Da;

[0041] The reverse osmosis membrane comprises an inorganic hybrid reverse osmosis membrane with a molecular weight cutoff of 40 to 70 Da.

[0042] Further, the recovered tetrabutylammonium hydroxide is mixed with a new tetrabutylammonium hydroxide reagent in a mass ratio of 1:(0-30) to obtain a plant cellulose solvent having a tetrabutylammonium hydroxide concentration of 55±5wt%, which is used for dissolving and spinning plant cellulose;

[0043] or

[0044] The recovered dimethyl sulfoxide is mixed with the recovered tetrabutylammonium hydroxide (and / or new tetrabutylammonium hydroxide reagent) to obtain a plant cellulose solvent having a mass ratio of dimethyl sulfoxide:tetrabutylammonium hydroxide:water of (0.2-8):1:1, which is used for dissolving and spinning plant cellulose;

[0045] The sulfuric acid is mixed with the recovered pure water in a mass ratio of 1:(1.5-19) to obtain a 5wt%-40wt% H2SO4 coagulation bath for use in spinning plant cellulose;

[0046] The new tetrabutylammonium hydroxide reagent is an analytically pure tetrabutylammonium hydroxide aqueous solution with a concentration of 41 to 70 wt%;

[0047] The sulfuric acid is concentrated sulfuric acid with a concentration of 98 wt%.

[0048] Furthermore, the prepared cellulose solvent is used to dissolve plant cellulose to obtain a cellulose solution, which is deaerated, filtered, and spun, and then subjected to multi-stage drawing and forming in a coagulation bath prepared by recycling pure water and sulfuric acid, and then oiled and dried for use in the production of regenerated cellulose fibers;

[0049] Preferably, the component types of the microfiltration membrane and the ultrafiltration membrane are tubular or plate-and-frame, the filtration accuracy of the microfiltration membrane is 0.1 to 10 μm, and the filtration accuracy of the ultrafiltration membrane is 0.001 to 0.1 μm.

[0050] More preferably, the microfiltration membrane is a zirconium oxide hybrid ceramic membrane, a titanium oxide hybrid ceramic membrane, or an aluminum oxide hybrid ceramic membrane, with a filtration accuracy of 1 to 5 μm, and the ultrafiltration membrane is a zirconium oxide hybrid ceramic membrane, a titanium oxide hybrid ceramic membrane, or an aluminum oxide hybrid ceramic membrane, with a filtration accuracy of 0.01 to 0.1 μm.

[0051] Preferably, the microfiltration membrane, the ultrafiltration membrane, the nanofiltration membrane and the reverse osmosis membrane all adopt cross-flow filtration.

[0052] Based on the same inventive concept, the present invention provides a recovered tetrabutylammonium hydroxide and dimethyl sulfoxide, which are prepared by the above-mentioned method for recovering and reusing solvents from the production process of regenerated cellulose materials.

[0053] Based on the same inventive concept, the present invention also provides a use of recovered tetrabutylammonium hydroxide and dimethyl sulfoxide as or in the preparation of plant cellulose solvent.

[0054] Optionally, the application includes:

[0055] The recovered tetrabutylammonium hydroxide is mixed with a new tetrabutylammonium hydroxide reagent in a mass ratio of 1:(0-30) to obtain a plant cellulose solvent having a tetrabutylammonium hydroxide concentration of 55±5wt%;

[0056] The recovered dimethyl sulfoxide is mixed with the recovered tetrabutylammonium hydroxide (and / or new tetrabutylammonium hydroxide reagent) to obtain a plant cellulose solvent having a mass ratio of dimethyl sulfoxide:tetrabutylammonium hydroxide:water of (0.2-8):1:1;

[0057] The sulfuric acid is mixed with the recovered pure water in a mass ratio of 1:(1.5-19) to obtain a 5wt%-40wt% H2SO4 coagulation bath;

[0058] The new tetrabutylammonium hydroxide reagent is an analytically pure tetrabutylammonium hydroxide aqueous solution with a concentration of 41 to 70 wt%;

[0059] The sulfuric acid is concentrated sulfuric acid with a concentration of 98 wt%.

[0060] The recovered tetrabutylammonium hydroxide and dimethyl sulfoxide are mixed in proportion and used to dissolve plant cellulose (cellulose pulp) to obtain a cellulose solution. After degassing, filtering and spinning, the solution is subjected to multi-stage drawing and forming in a coagulation bath composed of recovered pure water and sulfuric acid. After oiling and drying, the solution is used for the production of regenerated cellulose fibers.

[0061] The plant cellulose includes any one of cotton cellulose, coniferous wood cellulose, broadleaf wood cellulose and bamboo cellulose.

[0062] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0063] 1. The present invention discloses a method for recovering and reusing solvents from a regenerated cellulose material production process. The method adopts coarse filtration, ion resin exchange treatment and tandem membrane treatment to sequentially remove suspended impurities (cellulose residues and hair, etc.), acid radical ions, colored macromolecular impurities and micro-nano impurities visible to the naked eye in waste liquid, thereby achieving separation, purification and concentration of tetrabutylammonium hydroxide, dimethyl sulfoxide and water. In addition, the method adopts a cross-flow filtration process to process the waste liquid through the tandem membrane treatment, thereby increasing the service life of the membrane material and reducing the cost of waste liquid recovery. The method is simple to operate, has high recovery efficiency, low energy consumption and is green and environmentally friendly, thereby achieving efficient and low-cost recovery of tetrabutylammonium hydroxide, dimethyl sulfoxide and water.

[0064] 2. The present invention discloses a method for recovering and reusing solvents from a regenerated cellulose material production process. The method is based on a series integrated membrane technology to separate, purify and concentrate tetrabutylammonium hydroxide, dimethyl sulfoxide and water, including process flows such as coarse filtration, ion resin exchange and membrane treatment. The integrated membrane platform is preferably composed of a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane in series at a membrane area ratio of 1:1:62:250, thereby overcoming the shortcomings of high energy consumption and low stability of existing tetrabutylammonium hydroxide and dimethyl sulfoxide solvent recovery methods.

[0065] 3. The present invention discloses a method for recovering and reusing solvents from the production process of regenerated cellulose materials. After being processed by the process of the present invention, a 50wt% tetrabutylammonium hydroxide aqueous solution and a 94wt% dimethyl sulfoxide solution can be obtained. After being reconfigured, they can dissolve a variety of plant cellulose at room temperature. The obtained cellulose solution can be spun to obtain regenerated cellulose fibers with excellent mechanical properties, thus realizing the closed-loop use of solvents. In addition, the method can separate and purify 28-35wt% of water in the waste liquid, which can be recycled in the coagulation regeneration and washing process of the regenerated cellulose material, thereby improving the utilization rate of water and chemical raw materials and reducing chemical emissions and environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0067] Figure 1 This is a process flow chart for recovering solvents during the production of regenerated cellulose materials.

[0068] Figure 2 It is a liquid chromatographic comparison chart for the recovery of tetrabutylammonium hydroxide and dimethyl sulfoxide and their corresponding standard substances.

[0069] Figure 3 Optical images of the recovery of tetrabutylammonium hydroxide and dimethyl sulfoxide.

[0070] Figure 4 This is the infrared (FTIR) spectrum of recovered tetrabutylammonium hydroxide and dimethyl sulfoxide.

[0071] Figure 5 To recover tetrabutylammonium hydroxide and dimethyl sulfoxide ( 1 H-NMR) spectrum. DETAILED DESCRIPTION

[0072] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0073] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0074] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0075] The technical principles of the present invention are as follows:

[0076] The present invention discloses a method for recovering and reusing solvent from a regenerated cellulose material production process, the method comprising:

[0077] S1. The waste liquid generated during the production of the regenerated cellulose material is subjected to coarse filtration to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate;

[0078] S2. treating the crude filtrate with an anion ion exchange resin to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluent;

[0079] S3. The eluate is passed through a multi-stage series membrane filtration platform to remove micro-nano impurities in the eluate, and at the same time separate effective ingredients such as tetrabutylammonium hydroxide, dimethyl sulfoxide, water, etc., to obtain recovered tetrabutylammonium hydroxide, dimethyl sulfoxide and pure water.

[0080] S4. The recovered tetrabutylammonium hydroxide and the recovered dimethyl sulfoxide are mixed in proportion, and used to dissolve plant cellulose (cellulose pulp) to obtain a cellulose solution. After degassing, filtering and spinning, the solution is subjected to multi-stage drawing in a coagulation bath composed of the recovered pure water and sulfuric acid. After oiling and drying, the solution is used for the production of regenerated cellulose fibers.

[0081] Step S1 specifically includes:

[0082] The waste liquid generated in the production process of the regenerated cellulose material is passed through a filter screen with a pore size of 300 to 800 meshes to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate.

[0083] Optionally, the waste liquid includes coagulation bath waste liquid and / or water washing bath waste liquid.

[0084] In the present invention, the waste liquid is passed through a filter screen with a pore size of 300 to 800 meshes, so that micron-level suspended impurities, such as cellulose residues and hair, etc., in the waste liquid can be removed.

[0085] Step S2 specifically includes:

[0086] Treating the crude filtrate with an anion ion exchange resin to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluent;

[0087] Wherein, in the ion resin exchange treatment, the type of ion exchange resin includes at least one of styrene series, acrylic series, acetic acid series, epoxy series and urea-formaldehyde series;

[0088] The groups carried by the ion exchange resin include at least one of quaternary amine groups, primary amine groups, secondary amine groups and tertiary amine groups;

[0089] The particle size of the ion exchange resin is 20 to 60 meshes, and the loading amount is 0.3 to 0.9 times the volume of the exchange column;

[0090] In the ion resin exchange treatment, the flow rate of the crude filtrate is 4 to 12 times the volume of the resin bed per hour.

[0091] In the present invention, the crude filtrate is passed through an exchange column loaded with the above-mentioned ion exchange resin, so that acid radical ions and colored macromolecules in the crude filtrate can be removed.

[0092] In the present invention, the groups carried by the ion exchange resin include at least one of quaternary amine groups, primary amine groups, secondary amine groups and tertiary amine groups, which has the benefits of adsorbing acid radical ions and adjusting the pH value of the eluate.

[0093] Step S3 specifically includes:

[0094] The eluent is passed through a series of membrane platforms at room temperature and a pressure of 0.2 to 1 MPa to remove micro-nano impurities in the eluent, and tetrabutylammonium hydroxide, dimethyl sulfoxide and water are separated at the same time to obtain recovered tetrabutylammonium hydroxide, recovered dimethyl sulfoxide and pure water.

[0095] In the present invention, the eluent passes through a series of membrane platforms at room temperature and a pressure of 0.2 to 1 MPa, thereby removing micro-nano impurities (including micron- and nano-scale regenerated cellulose impurities) in the eluent, separating effective components such as tetrabutylammonium hydroxide, dimethyl sulfoxide and water, and obtaining a tetrabutylammonium hydroxide solution with a concentration of 30 to 50 wt%, and recovered dimethyl sulfoxide and pure water with a concentration of 80 to 95 wt%.

[0096] Further, the tandem membrane platform includes any one of the following a) to f):

[0097] a) It is composed of a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:1:62:250;

[0098] b) It is composed of a microfiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:250:250;

[0099] c) It is composed of an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:150:300;

[0100] d) It is composed of a microfiltration membrane, an ultrafiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:1:62;

[0101] e) It is composed of a microfiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:250;

[0102] f) It is composed of an ultrafiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:150;

[0103] Wherein, the pore size of the microfiltration membrane is 0.1-10 μm, and the pore size of the ultrafiltration membrane is 0.001-0.1 μm.

[0104] In the process of treating the eluent, the microfiltration membrane intercepts impurities larger than 0.1 μm in the eluent; the ultrafiltration membrane intercepts impurities larger than 0.01 μm in the eluent; the nanofiltration membrane separates tetrabutylammonium hydroxide from small molecules smaller than 80 to 300 Da (such as dimethyl sulfoxide and water) to obtain recovered tetrabutylammonium hydroxide; and the reverse osmosis membrane separates dimethyl sulfoxide from small molecules smaller than 40 to 70 Da (such as water) to obtain recovered dimethyl sulfoxide and pure water.

[0105] In the present invention, the microfiltration membrane, ultrafiltration membrane, nanofiltration membrane and reverse osmosis membrane are connected in series or in parallel-series according to the membrane area ratio of 1:1:62:250, which has the advantage of ensuring that the liquid flow through each membrane is equivalent, ensuring that the series membrane platform operates stably and reliably in the best state, reducing membrane failures caused by flow fluctuations, and improving the waste liquid treatment efficiency of the entire series membrane platform. Appropriate flow also helps to reduce the accumulation of impurities on the membrane surface, prevent membrane pore blockage, reduce membrane wear and mechanical stress, and extend the service life of the membrane.

[0106] Further, the material of the microfiltration membrane includes at least one of polypropylene, zirconia ceramics, titanium oxide ceramics, aluminum oxide ceramics, zirconia hybrid ceramics, titanium oxide hybrid ceramics and aluminum oxide hybrid ceramics;

[0107] The material of the ultrafiltration membrane includes at least one of zirconia ceramics, titanium oxide ceramics, aluminum oxide ceramics, zirconia hybrid ceramics, titanium oxide hybrid ceramics and aluminum oxide hybrid ceramics;

[0108] The nanofiltration membrane comprises an inorganic hybrid nanofiltration membrane with a molecular weight cutoff of 80 to 300 Da;

[0109] The reverse osmosis membrane comprises an inorganic hybrid reverse osmosis membrane with a molecular weight cutoff of 40 to 70 Da.

[0110] In the present invention, the nanofiltration membrane and the reverse osmosis membrane are made of inorganic hybrid materials, which are alkali-resistant and solvent-resistant, and have higher stability and better durability.

[0111] The invention discloses a method for recovering and reusing solvents from a regenerated cellulose material production process. The method adopts three processes of coarse filtration, ion resin exchange and serial membrane platform treatment to sequentially remove suspended impurities (cellulose residues and hair, etc.), acid radical ions, colored macromolecular impurities, micron-level and nanometer-level regenerated cellulose impurities visible to the naked eye in waste liquid, and simultaneously utilizes the difference between the pore size of a nanofiltration membrane and a reverse osmosis membrane and the size of solvent molecules in a solution to efficiently separate tetrabutylammonium hydroxide, dimethyl sulfoxide and water, thereby achieving purification and concentration of tetrabutylammonium hydroxide and dimethyl sulfoxide.

[0112] Step S4 specifically includes:

[0113] The recovered tetrabutylammonium hydroxide and dimethyl sulfoxide are mixed in proportion, and plant cellulose (cellulose pulp) is dissolved to obtain a cellulose solution, which is deaerated, filtered and spun, and then formed into a multi-stage traction solution in a 5wt% to 35wt% H2SO4 coagulation bath, and then oiled and dried for use in the production of regenerated cellulose fibers.

[0114] The process of the invention has simple operation, high recovery efficiency and low energy consumption, and the obtained recovery solvent has good dissolving performance for various plant celluloses, and realizes the spinning production of regenerated cellulose.

[0115] The following is a detailed description of a method for recovering and reusing solvents from a regenerated cellulose material production process according to the present application in combination with examples and experimental data.

[0116] Example 1

[0117] The method of recovering and reusing solvent from the production process of regenerated cellulose material in this embodiment comprises:

[0118] 1) 2 L of waste liquid consisting of a coagulation bath and a water washing bath generated during the production of regenerated cellulose fibers (wherein the concentration of tetrabutylammonium hydroxide is about 2 wt %, and the concentration of dimethyl sulfoxide is 20 wt %) is filtered through a coarse filter with an 800-mesh filter for 0.2 h to remove large-sized suspended impurities.

[0119] 2) The crude filtrate obtained in 1) is passed into the quaternary ammonium styrene-divinylbenzene copolymer anion (OH - The particle size of the exchange resin is 20 mesh, the resin loading amount is 0.8 times the volume of the exchange column, the feeding flow rate is 5 times the volume of the resin bed per hour, and a transparent eluent is obtained.

[0120] 3) The transparent eluate obtained in 2) is passed through a series membrane platform composed of a 1 μm pore size zirconium oxide hybrid ceramic microfiltration membrane-10 nm zirconium oxide hybrid ceramic ultrafiltration membrane-100 Da inorganic hybrid nanofiltration membrane-40 Da inorganic hybrid reverse osmosis membrane with a membrane area ratio of 1:1:62:250 at a rate of 0.5 L / h, and impurities larger than 10 nm in the eluate are removed at room temperature and 1 MPa to obtain a tetrabutylammonium hydroxide solution with a concentration of 50 wt%, a recovered dimethyl sulfoxide solution with a concentration of 94 wt%, and pure water.

[0121] 4) 70 g of cellulose was added to 791.49 g of recovered dimethyl sulfoxide solution, and after soaking for 30 min, 138.81 g of tetrabutylammonium hydroxide new solvent (concentration of 67 wt%) was added, and magnetic stirring was carried out at 500 rpm / min in a 30° C. water bath for 1 h to obtain a clear and transparent cellulose solution, which was then spun using a spinning machine, extruded through a metering pump after degassing and filtration, and drawn into shape in a 25 wt % H2SO4 coagulation bath (50° C.), and then the spun fibers were drawn onto a roller for primary drawing (7.5 m / min) to make the internal crystal orientation of the cellulose fibers consistent, and at the same time, the cellulose solvent was cleaned in a water washing bath (50° C.), and the spun fibers were again drawn onto a roller for secondary drawing (10.5 m / min), and after passing through an oiling roller, the spun fibers were drawn to a heating roller for drying, and finally the spun fibers were collected by a collection roller to obtain a smooth, shiny, silvery white regenerated cellulose fiber.

[0122] Figure 2 This is a liquid chromatogram comparison diagram of the tetrabutylammonium hydroxide and dimethyl sulfoxide recovered in Example 1 and their corresponding standard substances. Under the same conditions, the elution time of the recovered tetrabutylammonium hydroxide and the tetrabutylammonium hydroxide standard sample is 0.86 min, and the elution time of the recovered dimethyl sulfoxide and the dimethyl sulfoxide standard sample is 0.74 min.

[0123] like Figure 3 The optical images of recovered tetrabutylammonium hydroxide and dimethyl sulfoxide are shown, wherein (a) is the waste liquid in the production process of regenerated cellulose fiber; (b) is the new tetrabutylammonium hydroxide solution; (c) is the recovered tetrabutylammonium hydroxide; (d) is the new dimethyl sulfoxide solution; (e) is the recovered dimethyl sulfoxide. It can be seen that the recovered tetrabutylammonium hydroxide and dimethyl sulfoxide obtained in this embodiment are colorless and clear, and their appearance is similar to that of the new tetrabutylammonium hydroxide solution and the new dimethyl sulfoxide solution.

[0124] Figure 4 This is the FTIR spectrum of tetrabutylammonium hydroxide and dimethyl sulfoxide recovered in this example. Figure 5 The tetrabutylammonium hydroxide and dimethyl sulfoxide recovered in this embodiment 1 H-NMR spectrum, from Figure 4 , 5 It can be seen that the chemical composition of the recovered tetrabutylammonium hydroxide is the same as that of the new tetrabutylammonium hydroxide solution, and the chemical composition of the recovered dimethyl sulfoxide solvent is the same as that of the new dimethyl sulfoxide solution.

[0125] The energy consumption of this embodiment when recovering the solvent is only 0.44kW / h (the use time of the coarse filtration process (0.2h) × the pump power used for coarse filtration (0.18kW) + the use time of the membrane technology process (4h) × the pump power used for the membrane technology (0.10kW)

[0126] =0.44kW / h. Calculation formula: E=P×t, where energy consumption E=pump power used for coarse filtration (circulating water pump P=0.18kW)×use time of coarse filtration process+pump power used for membrane technology (self-priming pump 0.10kW)×use time of membrane technology process), and the separated water can be directly recycled and applied to the regeneration and washing process of regenerated cellulose fibers (such as Figure 1 ).

[0127] Example 2

[0128] The method of recovering and reusing solvent from the production process of regenerated cellulose material in this embodiment comprises:

[0129] 1) 2 L of waste liquid consisting of a coagulation bath and a water washing bath generated during the production of regenerated cellulose fibers (wherein the concentration of tetrabutylammonium hydroxide is about 2 wt %, and the concentration of dimethyl sulfoxide is 20 wt %) is filtered through a coarse filter with an 800-mesh filter for 0.2 h to remove large-sized suspended impurities.

[0130] 2) The crude filtrate obtained in 1) is passed into the quaternary ammonium styrene-divinylbenzene copolymer anion (OH - The particle size of the exchange resin is 20 mesh, the resin loading amount is 0.8 times the volume of the exchange column, the feeding flow rate is 5 times the volume of the resin bed per hour, and a transparent eluent is obtained.

[0131] 3) The transparent eluate obtained in 2) is passed through a series membrane platform composed of a 1 μm pore size zirconium oxide hybrid ceramic microfiltration membrane-10 nm zirconium oxide hybrid ceramic ultrafiltration membrane-100 Da inorganic hybrid nanofiltration membrane with a membrane area ratio of 1:1:62 at a rate of 1 L / h, and impurities larger than 10 nm in the eluate are removed at room temperature and 1 MPa, and tetrabutylammonium hydroxide and dimethyl sulfoxide are separated to obtain recovered tetrabutylammonium hydroxide with a concentration of 34 wt% and recovered dimethyl sulfoxide with a concentration of 21.25 wt%.

[0132] 4) 70 g of cellulose was added to 744 g of new dimethyl sulfoxide solvent, and after soaking for 30 min, 107.68 g of recovered tetrabutylammonium hydroxide and 78.32 g of new tetrabutylammonium hydroxide solvent (concentration of 72 wt%) were added, and magnetic stirring was carried out at 500 rpm / min in a 30° C. water bath for 1 h to obtain a clear and transparent cellulose solution, which was then spun using a spinning machine, extruded through a metering pump after degassing and filtration, and drawn into shape in a 25 wt % H2SO4 coagulation bath (50° C.), and then the spun fibers were drawn onto a roller for primary drawing (7.5 m / min) to make the internal crystal orientation of the cellulose fibers consistent, and at the same time, the cellulose solvent was cleaned in a water washing bath (50° C.), and the spun fibers were again drawn onto a roller for secondary drawing (10.5 m / min), and after passing through an oiling roller, the spun fibers were drawn to a heating roller for drying, and finally the spun fiber products were collected by a collection roller.

[0133] The energy consumption when recovering the solvent in this embodiment is only 0.236 kW / h (calculation process: use time of coarse filtration process (0.2h) × pump power used for coarse filtration (0.18 kW) + use time of membrane technology process (2h) × pump power used for membrane technology (0.1 kW) = 0.236 kW / h. Calculation formula: E = P × t, wherein, energy consumption E = pump power used for coarse filtration (circulating water pump P = 0.18 kW) × use time of coarse filtration process + pump power used for membrane technology (self-priming pump 0.1 kW) × use time of membrane technology process).

[0134] Comparative Example 1

[0135] This comparative example is a method for recovering and reusing solvent from the production process of regenerated cellulose materials. For comparison, this comparative example does not use an ion resin exchange process, and includes:

[0136] 1) 2 L of waste liquid consisting of a coagulation bath and a water washing bath generated during the production of regenerated cellulose fibers (wherein the concentration of tetrabutylammonium hydroxide is about 2 wt %, and the concentration of dimethyl sulfoxide is 20 wt %) is filtered through a coarse filter with an 800-mesh filter for 0.2 h to remove large-sized suspended impurities.

[0137] 2) The crude filtrate obtained in 1) is passed through a series membrane platform composed of a 1 μm pore size zirconium oxide hybrid ceramic microfiltration membrane-10 nm zirconium oxide hybrid ceramic ultrafiltration membrane-100 Da inorganic hybrid nanofiltration membrane with a membrane area ratio of 1:1:62 at a rate of 1 L / h, and impurities larger than 10 nm in the eluate are removed at room temperature and 1 MPa, and tetrabutylammonium hydroxide and dimethyl sulfoxide are separated to obtain recovered tetrabutylammonium hydroxide with a concentration of 30 wt% and recovered dimethyl sulfoxide with a concentration of 21.42 wt%.

[0138] 3) 70 g of cellulose was added to 744 g of new dimethyl sulfoxide solvent, and after soaking for 30 min, 97.43 g of recovered tetrabutylammonium hydroxide and 88.57 g of new tetrabutylammonium hydroxide solvent (concentration of 72 wt%) were added, and magnetic stirring was carried out at 500 rpm / min in a 30° C. water bath for 1 h to obtain a clear and transparent cellulose solution, which was then spun using a spinning machine, extruded through a metering pump after degassing and filtration, and drawn into shape in a 25 wt % H2SO4 coagulation bath (50° C.), and then the spun fibers were drawn onto a roller for primary drawing (7.5 m / min) to make the internal crystal orientation of the cellulose fibers tend to be consistent, and at the same time, the cellulose solvent was cleaned through a water washing bath (50° C.), and the spun fibers were again drawn onto a roller for secondary drawing (10.5 m / min), and after passing through an oiling roller, the spun fibers were drawn to a heating roller for drying, and finally the spun fiber products were collected by a collection roller.

[0139] The energy consumption when recovering the solvent in this comparative example is only 0.236 kW / h (the use time of the coarse filtration process (0.2h) × the pump power used for coarse filtration (0.18 kW) + the use time of the membrane technology process (2h) × the pump power used for membrane technology (0.1 kW) = 0.236 kW / h. Calculation formula: E = P × t, wherein, energy consumption E = pump power used for coarse filtration (circulating water pump P = 0.18 kW) × the use time of the coarse filtration process + pump power used for membrane technology (self-priming pump 0.1 kW) × the use time of the membrane technology process).

[0140] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article, or apparatus.

[0141] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0142] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for recovering and reusing solvent from a regenerated cellulose material production process, characterized in that: The method comprises: (1) coarsely filtering the waste liquid generated in the production process of the regenerated cellulose material to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate; (2) treating the crude filtrate with an anion ion exchange resin to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluent; (3) passing the eluate through a multi-stage series membrane filtration platform to remove micro-nano impurities in the eluate, and simultaneously separating tetrabutylammonium hydroxide, dimethyl sulfoxide and water, to obtain recovered tetrabutylammonium hydroxide, recovered dimethyl sulfoxide and recovered pure water; (4) The recovered tetrabutylammonium hydroxide and the recovered dimethyl sulfoxide are mixed in proportion and used to dissolve plant cellulose to obtain a cellulose solution. After degassing, filtering and spinning, the solution is subjected to multi-stage drawing in a coagulation bath composed of the recovered pure water and sulfuric acid. After oiling and drying, the solution is used for the production of regenerated cellulose fibers.

2. A method for recovering and reusing solvent from a regenerated cellulose material production process according to claim 1, characterized in that: The waste liquid generated in the production process of the regenerated cellulose material is subjected to coarse filtration treatment to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate, which specifically includes: Passing the waste liquid generated in the production process of the regenerated cellulose material through a filter screen with a pore size of 300 to 800 meshes to remove micron-sized suspended impurities in the waste liquid to obtain a coarse filtrate; The waste liquid includes coagulation bath waste liquid and / or water washing bath waste liquid; The step of subjecting the crude filtrate to ion resin exchange treatment to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluent specifically comprises: The crude filtrate is subjected to ion resin exchange treatment to remove acid ions and colored macromolecules in the crude filtrate to obtain an eluent; Wherein, in the ion resin exchange treatment, the type of ion exchange resin includes at least one of styrene series, acrylic series, acetic acid series, epoxy series and urea-formaldehyde series; The groups carried by the ion exchange resin include at least one of quaternary amine groups, primary amine groups, secondary amine groups and tertiary amine groups; The particle size of the ion exchange resin is 20 to 60 meshes, and the loading amount is 0.3 to 0.9 times the volume of the exchange column; In the ion resin exchange treatment, the flow rate of the crude filtrate is 4 to 12 times the volume of the resin bed per hour.

3. The method for recovering and reusing solvent from the production process of regenerated cellulose material according to claim 1, characterized in that: The step of passing the eluent through a series of membrane platforms to remove micro-nano impurities in the eluent and simultaneously separating tetrabutylammonium hydroxide, dimethyl sulfoxide and water to obtain recovered tetrabutylammonium hydroxide, recovered dimethyl sulfoxide and recovered pure water specifically comprises: The eluent is passed through a series of membrane platforms at room temperature and a pressure of 0.2 to 1 MPa to remove micro-nano impurities in the eluent, and tetrabutylammonium hydroxide, dimethyl sulfoxide and water are separated at the same time to obtain recovered tetrabutylammonium hydroxide, recovered dimethyl sulfoxide and recovered pure water.

4. A method for recovering and reusing solvent from a regenerated cellulose material production process according to claim 1 or 3, characterized in that: The tandem membrane platform includes any one of the following a) to f): a) It is composed of a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:1:62:250; b) It is composed of a microfiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:250:250; c) It is composed of an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane connected in series in a membrane area ratio of 1:150:300; d) It is composed of a microfiltration membrane, an ultrafiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:1:62; e) It is composed of a microfiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:250; f) It is composed of an ultrafiltration membrane and a nanofiltration membrane connected in series in a membrane area ratio of 1:150; Wherein, the pore size of the microfiltration membrane is 0.1-10 μm, and the pore size of the ultrafiltration membrane is 0.001-0.1 μm.

5. A method for recovering and reusing solvent from a regenerated cellulose material production process according to claim 4, characterized in that: The series membrane platforms are connected in series or parallel-series mode according to the membrane area ratio; Preferably, the series membrane platform is formed by connecting a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane in series in a membrane area ratio of 1:1:62:250; wherein the series membrane is formed by connecting 1:1:N1:N2 microfiltration membranes, ultrafiltration membranes, nanofiltration membranes and reverse osmosis membrane modules in series in a membrane area ratio of 1:1:62:250, and when N(1-2)=1, the membrane area ratio of the microfiltration membrane, ultrafiltration membrane, nanofiltration membrane and reverse osmosis membrane module is 1:1:62:250; when N(1-2)>1, the nanofiltration membrane and each membrane module in the reverse osmosis membrane unit are connected in parallel and connected in series with the microfiltration membrane and the ultrafiltration membrane to form a parallel-series integrated membrane platform, and the total membrane area ratio of the microfiltration membrane unit, the ultrafiltration membrane unit, the nanofiltration membrane unit and the reverse osmosis membrane unit module is 1:1:62:250; Further, when the tandem membrane platform includes any one of a) to b) or d) to e), the eluate first passes through the microfiltration membrane in a cross-flow filtration manner; When the tandem membrane platform comprises c) or f), the eluate first passes through the ultrafiltration membrane in a cross-flow filtration manner.

6. A method for recovering and reusing solvent from a regenerated cellulose material production process according to claim 4, characterized in that: When the series membrane platform includes any one of a) to c), tetrabutylammonium hydroxide is obtained at the cutoff end of the nanofiltration membrane, dimethyl sulfoxide is obtained at the cutoff end of the reverse osmosis membrane, and pure water is obtained at the permeation end of the reverse osmosis membrane; When the series membrane platform includes any one of d) to f), tetrabutylammonium hydroxide is obtained at the cutoff end of the nanofiltration membrane, and a dimethyl sulfoxide aqueous solution is obtained at the permeation end of the nanofiltration membrane.

7. A method for recovering and reusing solvent from a regenerated cellulose material production process according to claim 4, characterized in that: The material of the microfiltration membrane includes at least one of polypropylene, zirconia ceramics, titanium oxide ceramics, aluminum oxide ceramics, zirconia hybrid ceramics, titanium oxide hybrid ceramics and aluminum oxide hybrid ceramics; The material of the ultrafiltration membrane includes at least one of zirconia ceramics, titanium oxide ceramics, aluminum oxide ceramics, zirconia hybrid ceramics, titanium oxide hybrid ceramics and aluminum oxide hybrid ceramics; The nanofiltration membrane comprises an inorganic hybrid nanofiltration membrane with a molecular weight cutoff of 80 to 300 Da; The reverse osmosis membrane comprises an inorganic hybrid reverse osmosis membrane with a molecular weight cutoff of 40 to 70 Da.

8. The method for recovering and reusing solvent from the production process of regenerated cellulose material according to claim 1, characterized in that: The recovered tetrabutylammonium hydroxide and the new tetrabutylammonium hydroxide reagent are mixed in a mass ratio of 1:(0-30) to obtain a plant cellulose solvent with a tetrabutylammonium hydroxide concentration of 55±5wt%, which is used for dissolving and spinning plant cellulose; or The recovered dimethyl sulfoxide is mixed with the recovered tetrabutylammonium hydroxide (and / or new tetrabutylammonium hydroxide reagent) to obtain a plant cellulose solvent having a mass ratio of dimethyl sulfoxide:tetrabutylammonium hydroxide:water of (0.2-8):1:1, which is used for dissolving and spinning plant cellulose; The sulfuric acid is mixed with the recovered pure water in a mass ratio of 1:(1.5-19) to obtain a 5wt%-40wt% H2SO4 coagulation bath for use in spinning plant cellulose; The new tetrabutylammonium hydroxide reagent is an analytically pure tetrabutylammonium hydroxide aqueous solution with a concentration of 41 to 70 wt%; The sulfuric acid is concentrated sulfuric acid with a concentration of 98 wt%.

9. The method for recovering and reusing solvent from the production process of regenerated cellulose material according to claim 1, characterized in that: The cellulose solution is obtained by dissolving plant cellulose in the cellulose solvent prepared in claim 8, and after degassing, filtering and spinning, multi-stage drawing and forming is carried out in a coagulation bath prepared by recycling pure water and sulfuric acid, and after oiling and drying, it is used for the production of regenerated cellulose fibers; The plant cellulose includes any one of cotton cellulose, coniferous wood cellulose, broadleaf wood cellulose and bamboo cellulose.

10. A recovered tetrabutylammonium hydroxide, dimethyl sulfoxide and pure water, characterized in that: The recovered tetrabutylammonium hydroxide, dimethyl sulfoxide and pure water are prepared by a method for recovering and reusing solvents from a regenerated cellulose material production process as described in any one of claims 1-7.

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