A method for preparing and applying a wood membrane with dual functions of separation and degradation.

Abstract

This invention discloses a method for preparing and applying a dual-functional wood membrane with separation and degradation properties, belonging to the field of environmental functional materials preparation. The method involves placing a delignified wood membrane in a mixed aqueous solution of copper nitrate, ferric nitrate, and cobalt nitrate, followed by vacuum drying. An alkaline aqueous solution of sodium carbonate is then added to the mixed solution, followed by stirring and heating. The treated delignified wood membrane is then removed, washed until neutral, and freeze-dried to obtain the dual-functional wood membrane with separation and degradation properties. This invention treats the wood membrane with delignification and LDH loading, endowing it with excellent superhydrophilic / underwater superoleophobic properties. The separation efficiency for insoluble oils in oily wastewater reaches up to 99.60%, and the initial separation performance can be restored by simple self-washing with persulfate after 10 oil-water separation cycles. This significantly extends the membrane's service life, reduces costs, and is suitable for long-term, high-intensity, and various types of oil-water separation scenarios.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional material preparation, and in particular relates to a method for preparing and applying a wood film with dual functions of separation and degradation. Background Technology

[0002] Currently, the main technologies for treating oily wastewater include chemical oxidation, microbial degradation, flotation, sedimentation, coagulation-flocculation, centrifugation, and membrane separation. Membrane separation technology is considered one of the most promising methods due to its simple operation, high efficiency, and relatively low cost. Porous filter materials with special wettability, such as copper mesh, are used in high-efficiency oil-water separation. Although these materials have high flux and separation efficiency, they still suffer from high material cost, low corrosion resistance, and poor biodegradability, which seriously affect their large-scale application. Therefore, the development of a simple, low-cost, and biodegradable oil-water separation membrane material has attracted considerable research attention.

[0003] Balsa wood is a renewable, biodegradable, inexpensive, and abundant natural resource. Its perfect multi-level microchannels and unique chemical composition give it great potential in the preparation of functional materials. After chemically removing the hydrophobic lignin from the cell walls, the remaining cellulose and some hemicellulose possess hydrophilicity, giving the wood superhydrophilic and underwater superoleophobic properties. Furthermore, its anisotropic microchannels facilitate rapid water passage. The treated wood membrane can efficiently and with high throughput separate various oily wastewaters under gravity. However, actual oily wastewater generally contains water-soluble organic pollutants and water-insoluble oils. Water-soluble organic pollutants are present in the aqueous phase and are difficult to separate. Therefore, providing membrane materials that can simultaneously remove water-insoluble oils and water-soluble organic pollutants from oily wastewater remains a challenge.

[0004] Because wood contains abundant hydroxyl sites, the ideal approach is to load highly efficient catalysts within the multi-level microchannels of wood. Layered double hydroxides (LDHs), as highly efficient heterogeneous catalysts, are widely used in advanced sulfate radical oxidation processes to treat pollutants due to their simple preparation process, high activity, and low toxicity. Furthermore, the layered structure prevents the leaching of metal ions, and the abundant hydroxyl groups in wood can bind to LDHs, thus avoiding problems such as the difficulty in separating LDH particles from the aqueous phase. Cobalt-iron LDHs have a strong affinity for persulfate and can generate a large number of free radicals in a short time to degrade pollutants. However, the insufficient catalytic efficiency, low ion exchange capacity, and limited number of intrinsic active sites of LDHs hinder their potential for practical application. Therefore, developing a low-cost, simple-to-synthesize, high-performance, and highly catalytically efficient biodegradable membrane is a crucial technical challenge in oily wastewater treatment. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a dual-functional wood membrane with separation and degradation capabilities, thereby addressing the problems existing in the prior art. This invention loads a lignin-free wood membrane onto a copper-doped cobalt-iron bilayer hydroxide to impart antifouling properties and multi-level microchannel confined catalytic performance to the wood membrane, thus addressing the issue of copper doping in oil.

[0006] One of the technical solutions provided by this invention:

[0007] A method for preparing a wood membrane with dual functions of separation and degradation includes the following steps: placing a delignified wood membrane in a mixed aqueous solution of copper nitrate, ferric nitrate and cobalt nitrate, vacuum drying it, adding an alkaline aqueous solution of sodium carbonate to the mixed solution, stirring and heating it, removing the treated delignified wood membrane, washing it until neutral, and freeze-drying it to obtain the wood membrane with dual functions of separation and degradation.

[0008] Preferably, the delignified wood membrane is prepared from one of balsa wood membrane, linden wood membrane, poplar wood membrane, and eucalyptus wood membrane.

[0009] Since wood membranes such as balsa wood membrane, linden wood membrane, poplar wood membrane and eucalyptus wood membrane have similar microstructures, rich three-dimensional channels, and the same chemical composition, the lignin-free wood membrane in this invention can be prepared by one of the above-mentioned wood membranes.

[0010] The method for preparing delignified wood membranes using balsa wood membrane as raw material is as follows: NaOH (sodium hydroxide) and Na₂SO₃ (sodium sulfite) are dissolved in a solvent to obtain solution A; the raw balsa wood membrane (PW) is moistened with ethanol, then immersed in solution A and heated. The balsa wood membrane is then removed and rinsed with deionized water until the washing solution is neutral. The balsa wood membrane is then immersed in hydrogen peroxide solution and heated. Finally, the balsa wood membrane is removed, rinsed with deionized water, and treated in a freeze dryer at -54℃ to obtain the delignified wood membrane. The molar concentration of NaOH is 2-3 mol / L, the molar concentration of Na₂SO₃ is 0.3-0.5 mol / L, the solvent volume is 100-200 mL, the heating time is 3-5 h, and the solvent is selected from deionized water, methanol, or ethanol.

[0011] Preferably, the molar concentration ratio of copper nitrate, ferric nitrate and cobalt nitrate in the mixed aqueous solution is (2-6):5:(4-8).

[0012] More preferably, the molar ratio of copper nitrate, ferric nitrate, and cobalt nitrate in the mixed aqueous solution is 4:5:6.

[0013] Preferably, 10 pieces of delignified wood film with a diameter of 2.5 cm and a thickness of 4 mm are added to every 100 mL of mixed aqueous solution.

[0014] Preferably, the vacuum drying process is carried out at a temperature of 20-35°C for 1-3 hours and at a vacuum pressure of -1 MPa.

[0015] Preferably, the stirring time is 15-60 minutes.

[0016] Preferably, the heating temperature is 50-70℃ and the heating time is 24-72h.

[0017] The second technical solution provided by this invention:

[0018] The application of a dual-function wood membrane with separation and degradation prepared by the above preparation method in oil-water separation and degradation of water-soluble organic pollutants.

[0019] Preferably, the water-soluble organic pollutant is tetracycline.

[0020] The beneficial effects of this invention are:

[0021] (1) This invention treats the wood membrane with delignification and LDH loading, endowing it with excellent superhydrophilic / underwater superoleophobic properties. The separation efficiency of insoluble oils in oily wastewater reaches up to 99.60%. After 10 oil-water separations, the initial separation performance can be restored by simple self-cleaning with persulfate. This greatly extends the service life of the membrane, reduces costs, and is suitable for long-term, high-intensity, and various types of oil-water separation scenarios.

[0022] (2) The sulfate radical advanced oxidation process combined with membrane separation technology uses copper-doped cobalt iron LDHs to modify the wood membrane, giving it excellent persulfate activation performance. After separating water-insoluble oils, the degradation rate of water-soluble organic pollutant tetracycline is as high as 94.61% within 40 minutes.

[0023] (3) This invention provides a method for preparing a separation and degradation bifunctional membrane by loading copper-doped cobalt-iron LDHs into the three-dimensional hierarchical channels of delignified wood membrane. By removing hydrophobic and rigid lignin and hemicellulose, soft and hydrophilic cellulose is left behind. The copper-doped cobalt-iron LDHs with the gravel stacking structure on the pore wall of the wood membrane help to enhance capillary force, realizing the preparation of superhydrophilic / underwater superoleophobic surface and effective utilization of materials. The copper-doped cobalt-iron LDHs are stably combined with the excellent three-dimensional hierarchical channels in wood, thereby avoiding catalyst leakage and forming rich confined catalytic channels, giving the wood membrane excellent persulfate activation performance, which can continuously and efficiently separate water-insoluble oils and degrade water-soluble organic pollutants.

[0024] (4) The present invention provides a dual-function wood membrane with separation and degradation properties. It is superhydrophilic / underwater superoleophobic, has a simple preparation method, and has some potential applications, such as being able to efficiently separate oil-water mixtures and exhibiting excellent anti-fouling performance and rapid and strong organic matter degradation ability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 Digital photographs and scanning electron microscope (SEM) images of the balsa wood membrane (PW), the MW membrane prepared in Comparative Example 1, and the MW@CCF-0.4 membrane prepared in Example 2, wherein (a1) is a digital photograph and SEM image of the balsa wood membrane (PW), (a2) is a digital photograph and SEM image of the MW membrane, and (a3) ​​is a digital photograph and SEM image of the MW@CCF-0.4 membrane;

[0027] Figure 2 The EDS spectrum of the MW@CCF-0.4 film prepared in Example 2 is shown.

[0028] Figure 3 XRD images of balsa wood membrane (PW), MW membrane prepared in Comparative Example 1, MW@CCF-0 membrane prepared in Comparative Example 2, and MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3;

[0029] Figure 4 FT-IR images of balsa wood membrane (PW), MW membrane prepared in Comparative Example 1, MW@CCF-0 membrane prepared in Comparative Example 2, and MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3, where (a) is at 1150-2000 cm⁻¹. -1 FT-IR image, (b) at 2500-4050cm -1 FT-IR images;

[0030] Figure 5 Underwater oil contact angle diagrams for balsa wood membrane (PW), MW membrane prepared in Comparative Example 1, MW@CCF-0 membrane prepared in Comparative Example 2, and MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3;

[0031] Figure 6Hydrophilicity test results for balsa wood membrane (PW), MW membrane prepared in Comparative Example 1, MW@CCF-0 membrane prepared in Comparative Example 2, and MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3;

[0032] Figure 7 The separation efficiency and flux of the MW membrane prepared in Comparative Example 1, the MW@CCF-0 membrane prepared in Comparative Example 2, and the MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3 for oil-water mixtures were measured. Among them, (a) is a flowchart of oil-water separation, (b) shows the separation efficiency and flux of different membranes for n-hexane, (c) shows the separation efficiency and flux of different membranes for petroleum ether, (d) shows the separation efficiency and flux of different membranes for toluene, and (e) shows the separation efficiency and flux of different membranes for soybean oil.

[0033] Figure 8 (a) shows the tetracycline degradation performance test results of the MW membrane prepared in Comparative Example 1, the MW@CCF-0 membrane prepared in Comparative Example 2, and the MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3; (b) shows the tetracycline degradation rate of the MW@CCF-0.4 membrane under different PMS dosages; (c) shows the tetracycline degradation rate of the W@CCF-0.4 membrane under different pH conditions; and (d) shows the effect of tetracycline concentration on the degradation performance of the W@CCF-0.4 membrane.

[0034] Figure 9 (a) shows the results of the oil-water separation cycle stability test of the MW@CCF-0.4 membrane prepared in Example 2, and (b) shows the results of the test of the repeated degradation performance of the MW@CCF-0.4 membrane against tetracycline. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] The original balsa wood film used in the following examples was purchased from Alibaba Limited.

[0041] Example 1: A method for preparing a wood membrane with dual functions of separation and degradation

[0042] S1. Preparation of delignified wood membrane: Ten pieces of pure balsa wood membrane (PW) with a diameter of 2.5 cm and a thickness of 4 mm were moistened with ethanol. Then, the balsa wood membrane was immersed in 100 mL of deionized water containing 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 and treated at 80 °C for 3 h. The balsa wood membrane was removed and rinsed with deionized water until the washing solution was neutral. Then, the balsa wood membrane was immersed in 100 mL of 7.7 wt% hydrogen peroxide solution and treated at 80 °C for 3 h. Finally, the balsa wood membrane was removed and rinsed three times with deionized water. Finally, it was treated in a freeze dryer (-54 °C) for 12 h to obtain delignified wood membrane, labeled as MW membrane.

[0043] Preparation of S2.CuCo-Fe-LDHs decorative modified wood film: Four MW films prepared in S1 were immersed in 50 mL of deionized water containing 0.016 mol / L Cu(NO3)2·3H2O, 0.04 mol / L Fe(NO3)3·9H2O, and 0.064 mol / L Co(NO3)2·6H2O, and placed in a vacuum drying oven (25℃, -1 MPa) for 1 h. Then, a solution containing 0.25 mol / L NaOH and 0.075 mol / L... 50 mL of deionized Na2CO3 aqueous solution was poured into the above solution and stirred vigorously for 15 min. Finally, the mixed solution was transferred to a water bath (60℃) and kept for 48 h. The membrane was then removed and washed with deionized water until the washing solution was neutral. It was then freeze-dried (-54℃) for 12 h to obtain CuCo-Fe-LDHs decorative modified wood membrane, which is a wood membrane with dual functions of separation and degradation, labeled as MW@CCF-0.2 membrane (where 0.2 represents the molar ratio of copper to the total of copper and cobalt, the same below).

[0044] Example 2: A method for preparing a wood membrane with dual functions of separation and degradation

[0045] S1. Preparation of delignified wood membrane: Ten pieces of raw balsa wood membrane (PW) with a diameter of 2.5 cm and a thickness of 4 mm were moistened with ethanol. Then, the balsa wood membrane was immersed in 100 mL of deionized water containing 2.5 mol / L sodium hydroxide (NaOH) and 0.4 mol / L sodium sulfite (Na2SO3) and treated at 80 °C for 3 h. The balsa wood membrane was removed and rinsed with deionized water until the washing solution was neutral. Then, the balsa wood membrane was immersed in 100 mL of 7.7 wt% hydrogen peroxide solution and treated at 80 °C for 3 h. Finally, the balsa wood membrane was removed and rinsed three times with deionized water. Finally, it was treated in a freeze dryer (-54 °C) for 12 h. The resulting delignified wood membrane was labeled as MW membrane.

[0046] Preparation of S2.CuCo-Fe-LDHs decorative modified wood membrane: Four MW membranes prepared in S1 were immersed in 50 mL of deionized water containing 0.032 mol / L Cu(NO3)2·3H2O, 0.04 mol / L Fe(NO3)3·9H2O and 0.048 mol / L Co(NO3)2·6H2O, and placed in a vacuum drying oven (25℃, -1 MPa) for 1 h. Then, 50 mL of deionized water containing 0.25 mol / L NaOH and 0.075 mol / L Na2CO3 was poured into the above solution and stirred vigorously for 15 min. Finally, the mixed solution was transferred to a water bath (60℃) and kept for 48 h. The membrane was removed and washed with deionized water until the washing solution was neutral. Then, it was freeze-dried (-54℃) for 12 h. The resulting CuCo-Fe-LDHs decorative modified wood membrane is a dual-function wood membrane with separation and degradation capabilities, labeled as MW@CCF-0.4 membrane.

[0047] Example 3: A method for preparing a wood membrane with dual functions of separation and degradation

[0048] S1. Preparation of delignified wood membrane: Ten pieces of raw balsa wood membrane (PW) with a diameter of 2.5 cm and a thickness of 4 mm were moistened with ethanol. Then, the balsa wood membrane was immersed in 100 mL of deionized water containing 2.5 mol / L NaOH and 0.4 mol / L Na2SO3 and treated at 80 °C for 3 h. The balsa wood membrane was removed and rinsed with deionized water until the washing solution was neutral. Then, the wood membrane was immersed in 100 mL of 7.7 wt.% hydrogen peroxide solution and treated at 80 °C for 3 h. Finally, the balsa wood membrane was removed and rinsed three times with deionized water. Finally, it was treated in a freeze dryer (-54 °C) for 12 h to obtain delignified wood membrane, labeled as MW membrane.

[0049] Preparation of S2.CuCo-Fe-LDHs decorative modified wood membrane: Four MW membranes prepared in S1 were immersed in 50 mL of deionized water containing 0.048 mol / L Cu(NO3)2·3H2O, 0.04 mol / L Fe(NO3)3·9H2O and 0.032 mol / L Co(NO3)2·6H2O, and placed in a vacuum drying oven (25℃, -1 MPa) for 1 h. Then, 50 mL of deionized water containing 0.25 mol / L NaOH and 0.075 mol / L Na2CO3 was poured into the above solution and stirred vigorously for 15 min. Finally, the mixed solution was transferred to a water bath (60℃) and kept for 48 h. The membrane was removed and washed with deionized water until the washing solution was neutral, and then freeze-dried (-54℃) for 12 h to obtain CuCo-Fe-LDHs decorative modified wood membrane, which is a dual-function wood membrane with separation and degradation capabilities, labeled as MW@CCF-0.6 membrane.

[0050] Comparative Example 1

[0051] The preparation method for using simple delignified wood membranes as functional wood membranes is as follows:

[0052] Preparation of delignified wood membrane: Ten virgin balsa wood membranes (PW) were moistened with ethanol, then immersed in 100 mL of deionized water containing 2.5 mol / L sodium hydroxide (NaOH) and 0.4 mol / L sodium sulfite (Na2SO3) and treated at 80℃ for 3 h. The balsa wood membranes were then removed and rinsed with deionized water until the washing solution was neutral. The balsa wood membranes were then immersed in 100 mL of 7.7 wt% hydrogen peroxide solution and treated at 80℃ for 3 h. Finally, the balsa wood membranes were removed and rinsed three times with deionized water. Finally, the membranes were freeze-dried (-54℃) for 12 h to obtain delignified wood membranes, labeled as MW membranes.

[0053] Performance tests demonstrated that loading copper-doped cobalt-iron LDHs onto the wood membrane improved wettability and separation performance, and also provided excellent persulfate activation properties for degrading organic pollutants.

[0054] Comparative Example 2

[0055] The preparation method for loading only cobalt-iron LDHs onto delignified wood membranes is as follows:

[0056] S1. Preparation of delignified wood membrane: Ten pieces of virgin balsa wood membrane (PW) were moistened with ethanol, and then the balsa wood membrane was immersed in 100 mL of deionized water containing 2.5 mol / L sodium hydroxide (NaOH) and 0.4 mol / L sodium sulfite (Na2SO3) and treated at 80℃ for 3 h. The balsa wood membrane was removed and rinsed with deionized water until the washing solution was neutral. Then the balsa wood membrane was immersed in 100 mL of 7.7 wt% hydrogen peroxide solution and treated at 80℃ for 3 h. Finally, the balsa wood membrane was removed and rinsed 3 times with deionized water. Finally, it was treated in a freeze dryer (-54℃) for 12 h to obtain delignified wood membrane, labeled as MW membrane;

[0057] Preparation of S2. Co-Fe-LDHs decorative modified wood membrane: Four MW membranes prepared in S1 were immersed in 50 mL of deionized water containing 0.04 mol / L FFe(NO3)3·9H2O and 0.08 mol / L Co(NO3)2·6H2O and placed in a vacuum drying oven (25℃, -1 MPa) for 1 h. Then, 50 mL of deionized water containing 0.25 mol / L NaOH and 0.075 mol / L Na2CO3 was poured into the above solution and stirred vigorously for 15 min. Finally, the mixed solution was transferred to a water bath (60℃) and kept for 48 h. The membrane was removed and washed with deionized water until the washing solution was neutral. Then, it was freeze-dried (-54℃) for 12 h to obtain the Co-Fe-LDHs decorative modified wood membrane, which is a dual-function wood membrane with separation and degradation capabilities, labeled as MW@CCF-0 membrane.

[0058] Performance tests have shown that copper doping slightly improves wettability and separation performance, and significantly enhances persulfate activation performance.

[0059] Performance testing

[0060] 1. Scanning electron microscopy and energy dispersive spectroscopy (EDS)

[0061] Figure 1 (a1) shows a digital photograph and scanning electron microscope (SEM) image of the balsa wood membrane (PW); (a2) shows a digital photograph and SEM image of the MW membrane prepared in Comparative Example 1; (a3) ​​shows a digital photograph and SEM image of the MW@CCF-0.4 membrane prepared in Example 2. Figure 1 As can be seen from (a1)-(a2), selective removal of lignin and hemicellulose has no significant effect on the channels of the wood membrane; Figure 1 As shown in (a3), after treatment, the channel surface of the balsa wood membrane was loaded with a large number of LDH nanosheets, thus proving the success of LDH-loaded wood membrane.

[0062] Figure 2 The EDS energy spectrum of the MW@CCF-0.4 film is shown below. Figure 2 As can be seen, the contents of Cu, Co, and Fe elements in the channel are 2.73%, 3.69%, and 5.73%, respectively, which further proves the success of copper-doped cobalt-iron LDHs loaded with balsa wood membrane.

[0063] 2. XRD pattern testing

[0064] Figure 3 XRD images of PW, the MW film prepared in Comparative Example 1, the MW@CCF-0 film prepared in Comparative Example 2, and the MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 films prepared in Examples 1-3.

[0065] from Figure 3 As can be seen, the cellulose-related signals (16.1° and 22.3°) are stronger in the MW membrane than in the PW. This indicates that the exposure of cellulose increases with the removal of lignin. Furthermore, the peaks at 11.6°, 23.4°, 38.9°, 59.5°, and 60.8° in MW@CCF-x can be well attributed to the (003), (006), (015), (110), and (113) planes of CoFe-LDH (JCPDS PDF#50-0235), respectively, demonstrating that CoFe-LDH has been successfully integrated into the MW matrix.

[0066] 3. Fourier Transmission Infrared Spectroscopy (FT-IR) Test

[0067] Figure 4 FT-IR images of PW, the MW film prepared in Comparative Example 1, the MW@CCF-0 film prepared in Comparative Example 2, and the MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 films prepared in Examples 1-3.

[0068] from Figure 4 As can be seen, the lignin and hemicellulose removed from PW were also confirmed by Fourier transform infrared spectroscopy (FT-IR). Figure 4 As shown in (a), after treatment, 1456 (aromatic skeletal vibration), 1503 and 1593 cm⁻¹ -1 The characteristic peaks at (lignin aromatic ring C=C extension vibration) are significantly reduced, indicating that lignin has been removed. Furthermore, the peaks at 1235 and 1735 cm⁻¹ are also significantly reduced. -1 The disappearance of the characteristic peak indicates that hemicellulose has been successfully removed. Furthermore, as... Figure 4 As shown in (b), 3500cm -1 The nearby broadband is attributed to the stretching vibrations of hydroxyl and water molecules in the layered structure. Furthermore, hydrogen bonding occurs due to the 109 cm⁻¹ vibrations of the hydroxyl groups. -1 The movement of the material indicates that CoFe-LDH is bound to the wood membrane via hydrogen bonds.

[0069] 4. Wetting performance test

[0070] Figure 5 Underwater oil contact angle diagrams for PW, MW membrane prepared in Comparative Example 1, MW@CCF-0 membrane prepared in Comparative Example 2, and MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3.

[0071] from Figure 5As can be seen, the PW and MW membranes exhibit oleophobicity, with underwater oil contact angles (UOCA) of 151.1° and 156.6°, respectively. The UOCA of the MW@CCF-0, MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes are 161.3°, 161.6°, 161.8°, and 161.4°, respectively, indicating that the modified wood membranes after loading with LDHs particles exhibit excellent underwater superoleophobicity.

[0072] Figure 6 The hydrophilicity test results of PW, the MW membrane prepared in Comparative Example 1, the MW@CCF-0 membrane prepared in Comparative Example 2, and the MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3.

[0073] Depend on Figure 6 It can be seen that because PW contains hydrophobic lignin and hemicellulose, it still maintains a water contact angle (WCA) of 104.8° after 1 second of water droplet contact. The WCA of MW membrane, MW@CCF-0 membrane, MW@CCF-0.2 membrane, MW@CCF-0.4 membrane and MW@CCF-0.6 membrane becomes 0° after 0.03 seconds, which proves that the hydrophobic lignin and hemicellulose have been removed, leaving only hydrophilic cellulose.

[0074] 5. Separation performance test

[0075] Figure 7 The separation efficiency and flux of four oil-water mixtures (n-hexane + water, petroleum ether + water, toluene + water, and soybean oil) were determined by the PW membrane, the MW membrane prepared in Comparative Example 1, the MW@CCF-0 membrane prepared in Comparative Example 2, and the MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3.

[0076] in, Figure 7 (a) illustrates oil-water separation (V oil :V water The process is 1:1, with the aqueous phase stained with methylene blue and the oil phase stained with Sudan Red. The wood membrane is moistened and then placed between the glass tubes of the separation device and secured with clamps. Under gravity, the permeation flux J (L m) -2 h -1 Calculate using the following formula:

[0077]

[0078] Where V is the permeation volume (in liters), A is the effective membrane area (in square meters), and Δt is the operating time (in hours).

[0079] The oil concentrations before and after separation were measured using a UV-Vis spectrophotometer. The separation efficiency (R, %) was obtained from the following formula:

[0080]

[0081] Where C f C0 and C0 refer to the oil concentrations in the filtrate and the initial emulsion, respectively.

[0082] Figure 7 As shown in (b)-(e), the separation efficiencies of the above membranes are not significantly different, all exceeding 98.6%, with a separation efficiency of up to 99.6% for n-hexane. Due to differences in oil viscosity, the MW membrane has the highest flux for n-hexane at 5356.26 L / h. -1 m -2 The lowest flux for soybean oil is 4524.45 L / h. -1 m -2 The flux increased after loading copper-doped cobalt-iron LDHs. The fluxes of the MW@CCF-0, MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes for n-hexane were 6068.64, 6055.33, 6073.62, and 6085.63 L / h, respectively. -1 m -2 The fluxes for soybean oil were 5020.79, 5032.24, 5115.25, and 5093.42 L / h. -1 m -2 This is because copper-doped cobalt-iron LDHs form a gravel structure within the membrane channels, thereby enhancing their capillary force.

[0083] 6. Tetracycline degradation performance test

[0084] Figure 8 The results of tetracycline degradation performance tests on the MW membrane prepared in Comparative Example 1, the MW@CCF-0 membrane prepared in Comparative Example 2, and the MW@CCF-0.2, MW@CCF-0.4, and MW@CCF-0.6 membranes prepared in Examples 1-3 are presented. Figure 8In Figure (a), it is shown that the degradation efficiency of potassium persulfate (PMS) alone for tetracycline was only 4.54% within 40 min; the MW membrane only had an adsorption effect on tetracycline, and the tetracycline decreased by only 4.18% after 70 min of adsorption; the degradation rate of tetracycline by the MW@CCF-0 membrane was 85.78%, and the degradation rates of tetracycline by the MW@CCF-0.2 membrane, MW@CCF-0.4 membrane, and MW@CCF-0.6 membrane were 92.65%, 94.61%, and 93.24%, respectively. It can be seen that the persulfate activation performance of cobalt-iron LDHs is significantly enhanced after copper doping.

[0085] Taking the MW@CCF-0.4 membrane as an example, the effects of PMS application amount, pH, and tetracycline concentration on degradation were investigated. Figure 8 As shown in Figure (b), the MW@CCF-0.4 membrane exhibited excellent tetracycline degradation performance under different PMS dosages; the degradation performance gradually improved with increasing PMS dosage, reaching a maximum degradation rate of 95.90% when the PMS dosage was 0.5 g / L. Figure 8 As shown in (c), the degradation rate of the MW@CCF-0.4 membrane differs significantly under different pH conditions. When the pH is between 3 and 9, the catalytic performance of the MW@CCF-0.4 membrane does not change much. However, when the pH increases to 11, the catalytic performance shows a significant downward trend. This is because PMS self-decomposes at this point, and under strongly alkaline conditions, hydroxide ions quench sulfate free radicals, thereby inhibiting free radical generation. Figure 8 As shown in (d), the degradation efficiency decreases with increasing tetracycline dosage. This is because as the pollutant concentration increases, more active free radicals are required to participate in the reaction. Since the catalyst concentration is fixed, the number of free radicals generated is also fixed, so the degradation efficiency inevitably decreases. In summary, the MW@CCF-0.4 membrane exhibits excellent tetracycline degradation performance under different conditions.

[0086] 7. Cyclic performance test

[0087] Figure 9 The results show the oil-water separation cycle stability and tetracycline repeated degradation performance of the MW@CCF-0.4 membrane prepared in Example 2. Figure 9 As shown in Figure (a), the MW@CCF-0.4 membrane was used in 20 oil-water separation experiments on a hexane-water mixture, with an initial separation efficiency of 99.60% and a flux of 6073.62 L / h. -1 m -2 At this point, the UOCA was 161.8°; after 10 oil-water separation cycles, the separation efficiency and throughput decreased slightly to 99.02% and 6002.55 L / h, respectively. -1 m -2The UOCA value became 148.6°; at this point, 0.3 g / L PMS was added for a 20-minute self-cleaning treatment, and the separation efficiency and throughput almost completely recovered, with the UOCA value reaching 160.9°; after 10 more oil-water separation cycles, the separation efficiency and throughput decreased slightly to 98.85% and 5992.76 L / h, respectively. -1 m -2 The UOCA value is 147.3°; the MW@CCF-0.4 membrane still maintains excellent separation performance and superhydrophilic / underwater superoleophobic properties. From Figure 9 Figure (b) shows that the MW@CCF-0.4 membrane underwent 5 consecutive cycles of degradation experiments. After 40 minutes of the 5 cycles, the degradation efficiency remained at 93.84%, which proves that the MW@CCF-0.4 membrane has excellent catalytic stability and is suitable for continuous and long-term pollutant degradation scenarios.

[0088] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a wood membrane with dual functions of oil-water separation and organic matter degradation, characterized in that, Includes the following steps: The delignified wood membrane was placed in a mixed aqueous solution of copper nitrate, ferric nitrate, and cobalt nitrate. After vacuum drying, an alkaline aqueous solution of sodium carbonate was added to the mixed solution. After stirring and heating, the treated delignified wood membrane was removed, washed until neutral, and freeze-dried to obtain the wood membrane with dual functions of oil-water separation and organic matter degradation.

2. The preparation method according to claim 1, characterized in that, The delignified wood membrane is prepared from one of balsa wood membrane, linden wood membrane, poplar wood membrane, and eucalyptus wood membrane.

3. The preparation method according to claim 1, characterized in that, The molar ratio of copper nitrate, ferric nitrate and cobalt nitrate in the mixed aqueous solution is (2-6):5:(4-8).

4. The preparation method according to claim 3, characterized in that, The molar ratio of copper nitrate, ferric nitrate, and cobalt nitrate in the mixed aqueous solution is 4:5:

6.

5. The preparation method according to claim 1, characterized in that, Add 10 pieces of delignified wood film with a diameter of 2.5 cm and a thickness of 4 mm to every 100 mL of mixed aqueous solution.

6. The preparation method according to claim 1, characterized in that, The vacuum drying process is carried out at a temperature of 20-35℃ for 1-3 hours and at a vacuum pressure of -1 MPa.

7. The preparation method according to claim 1, characterized in that, The heating temperature is 50-70℃, and the time is 24-72h.

8. The application of a dual-function wood membrane for oil-water separation and organic matter degradation prepared by the preparation method according to any one of claims 1-7 in oil-water separation and degradation of water-soluble organic pollutants.

9. The application according to claim 8, characterized in that, The water-soluble organic pollutant is tetracycline.

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