Tea residue composite adsorption film and preparation method thereof

Abstract

The invention provides a preparation method of a tea residue composite adsorption film. The preparation method comprises the following steps: adding modified tea residues and CNF into NMMO (N-methylmorpholine-N-oxide), and uniformly mixing to prepare mixed sol; coating part of the mixed sol on a first template of which the top is provided with a plurality of bulges, drying until the mixed sol is formed but is not completely dried, and then taking down the mixed sol from the template to obtain a base film with a plurality of pits for later use; coating part of the mixed sol on a second template with a flat top, drying to a completely dry state, and then cutting into a plurality of membranes for later use; the face, with the pits, of the base film is placed upwards, and a particle ball is placed in each pit; blocking each particle ball in the pit by using a membrane, wherein the diameter of the particle ball is smaller than that of the pit and the depth of the particle ball; and finally, uniformly coating a part of the mixed sol on the base membrane and the membrane sheet, and drying to a completely dry state to obtain the tea residue composite adsorption membrane. The method not only can effectively solve the problem of membrane flux attenuation caused by membrane pollution, but also is green and environment-friendly, and the material cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a tea residue composite adsorption membrane and a preparation method thereof. Background Art

[0002] The appearance of the mixed liquor of liquor-making wastewater is yellow and opaque; it has a high chromaticity and turbidity. The mass concentration of suspended solids (SS) in the untreated mixed wastewater is as high as 3000 - 5000 mg / L, and the COD is generally between 15000 - 20000 mg / L. Moreover, it contains a large amount of elements such as nitrogen and phosphorus, with the total nitrogen being about 50 - 500 mg / L and the total phosphorus being about 120 - 900 mg / L. Since liquor-making wastewater is obtained through fermentation and distillation, its pH is between 3 - 5, showing acidity. The liquor-making wastewater has a large volume and relatively complex water quality components, usually containing more organic dyes, low-carbon alcohols (such as methanol, ethanol, etc.), organic acids (such as fatty acids, amino acids, etc.), aldehydes, and esters. Therefore, if the liquor-making wastewater is directly discharged into the environment without treatment, it will cause serious pollution to the surrounding water bodies and soil.

[0003] The treatment of the production wastewater of liquor factories is a very important link. Currently, there are many treatment methods for the production wastewater of liquor factories, and the more common ones are: biological treatment methods, physicochemical treatment methods, and membrane separation technologies. Among them, the membrane separation technology uses a filtration membrane made of special materials (such as mixed fiber microporous membranes, polypropylene membranes, polyethersulfone membranes, polyvinylidene fluoride membranes, polytetrafluoroethylene membranes, nylon membranes) to separate dissolved organic matters, ions, etc. in the wastewater. This technology has the advantages of high efficiency, energy conservation, and no pollution. Membranes are particularly important today due to their high separation efficiency, energy conservation, high efficiency, and no secondary pollution in the context of tight energy supply, increasingly scarce resources, and deteriorating ecological environment. However, during the membrane filtration process, fine particles, colloidal particles, or solute macromolecules in water cause adsorption and deposition on the membrane surface or in the membrane pores due to physical and chemical interactions or mechanical actions with the membrane, resulting in a decrease in membrane pore size or blockage, and causing irreversible changes in the permeation flux and separation characteristics of the membrane (that is, membrane fouling). Therefore, the problem of membrane flux decline caused by membrane fouling has become a key issue hindering its industrialization process. Summary of the Invention

[0004] To solve the above problems, the purpose of the present invention is to provide a tea residue composite adsorption membrane and a preparation method thereof, and this tea residue composite adsorption membrane can effectively solve the problem of membrane flux decline caused by membrane fouling.

[0005] The purpose of the present invention is achieved through the following technical solutions: A preparation method of a tea residue composite adsorption membrane includes the following steps: adding modified tea residue and nanocellulose (CNF) into an aqueous solution of N-methylmorpholine (NMMO) and mixing them evenly to form a mixed sol; taking a part of the mixed sol and coating it on a first template with multiple protrusions on the top, drying it until it is formed but not completely dry, and then removing it from the template to obtain a base membrane with multiple pits for standby; taking a part of the mixed sol and coating it on a second template with a flat top, drying it until it is completely dry, and then cutting it into multiple membrane pieces for standby; placing the base membrane with the pitted side facing up, and placing a particle ball in each pit respectively; then using the membrane pieces to seal each particle ball in its corresponding pit, and the diameter of the particle ball is smaller than the diameter and depth of the pit; finally, taking a part of the mixed sol and evenly coating it on the base membrane and the membrane pieces, drying it until it is completely dry to obtain the tea residue composite adsorption membrane.

[0006] The preparation steps of the modified tea residue are as follows: washing the tea residue multiple times, drying and grinding it to obtain tea residue powder for standby; mixing the tea residue powder, polyvinyl alcohol and zinc nitrate powder to obtain a mixture, then putting the mixture into a methanol solution containing methylimidazole, continuously stirring and mixing it evenly, after reaction and precipitation, taking the precipitate and washing it multiple times with methanol, and then successively drying and grinding it to obtain the modified tea residue.

[0007] In another structure of the present invention, to improve the cleaning effect, a micro vibrator is further encapsulated at the edge of the tea residue composite adsorption membrane.

[0008] A preparation method of a tea residue composite adsorption membrane is obtained by using the above preparation method.

[0009] The present invention uses tea residue with a special micro-porous structure as a raw material, and through steps of modification, loading and composite film formation, the prepared tea residue composite adsorption membrane can not only effectively solve the problem of membrane flux attenuation caused by membrane pollution and greatly improve the membrane flux, but also is green and environmentally friendly, and has low material cost. Specific embodiments

[0010] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. Example 1

[0011] This example provides a preparation method of a tea residue composite adsorption membrane, including the following steps: S1. Tea residue modification: Wash the tea residue multiple times, then conduct vacuum drying at a temperature of 30 - 45 °C and grind it into fine powder for later use; then mix the tea residue powder, polyvinyl alcohol, and zinc nitrate powder to obtain a mixture. Next, put the mixture into a methanol solution containing methylimidazole, continue to stir and mix evenly, after reaction and precipitation, take the precipitate and wash it multiple times with methanol, and then obtain the modified tea residue after drying and grinding in sequence. The mass ratio of the tea residue powder, polyvinyl alcohol, zinc nitrate, and methylimidazole is 1:0.5:0.2:1.

[0012] S2. Preparation of mixed sol: Add the modified tea residue and nanofibrillated cellulose (CNF) into an aqueous solution of N-methyl morpholine-N-oxide (NMMO) and mix evenly to prepare a mixed sol; the mass ratio of the modified tea residue, nanofibrillated cellulose (CNF), and aqueous solution of N-methyl morpholine-N-oxide (NMMO) is 1:3:100.

[0013] S3. Preparation of base film: Take a part of the mixed sol and coat it on a first template with multiple protrusions on the top. After drying until it is formed but not completely dry, remove it from the template to obtain a base film with multiple pits for later use. The pits on the first template are in the shape of a hollow spherical body, and its depth is four-fifths of its diameter. At the same time, the diameter of the particle ball is two-fifths of the diameter of the pit; the pits are arranged in an array on the base film; the film sheet is in a long strip shape and can cover one row or one column of pits on the base film.

[0014] S4. Preparation of film sheet: Take a part of the mixed sol and coat it on a second template with a flat top. Dry it until it is completely dry, and then cut it into multiple film sheets for later use.

[0015] S5. Composite: Place the base film with the pitted side facing up, and place a particle ball in each pit respectively; then use the film sheet to block each particle ball in its corresponding pit, and the diameter of the particle ball is smaller than the diameter and depth of the pit; finally, take a part of the mixed sol and evenly coat it on the base film and the film sheet, and dry it until it is completely dry to obtain the tea residue composite adsorption film. The particle ball is a sponge ball, a rubber ball, a plastic ball, or a ceramic ball. Example 2

[0016] This example provides a method for preparing a tea residue composite adsorption film, including the following steps: S1. Tea residue modification: Wash the tea residue multiple times, then conduct vacuum drying at a temperature of 30 - 45 °C and grind it into fine powder for later use; then mix the tea residue powder, polyvinyl alcohol, and zinc nitrate powder to obtain a mixture. Next, put the mixture into a methanol solution containing methylimidazole, continue to stir and mix evenly, after reaction and precipitation, take the precipitate and wash it multiple times with methanol, and then obtain the modified tea residue after drying and grinding in sequence. The mass ratio of the tea residue powder, polyvinyl alcohol, zinc nitrate, and methylimidazole is 1:0.5:0.3:1.2.

[0017] S2. Preparation of mixed sol: Add modified tea residue and nanofibrillated cellulose (CNF) into an aqueous solution of N-methyl morpholine (NMMO) and mix well to form a mixed sol; the mass ratio of the modified tea residue, nanofibrillated cellulose (CNF) and the aqueous solution of N-methyl morpholine (NMMO) is 1:2.5:110.

[0018] S3. Preparation of base membrane: Take a part of the mixed sol and coat it on a first template with multiple protrusions on the top. After drying to a formed but not completely dry state, remove it from the template to obtain a base membrane with multiple pits for standby. The pits on the first template are in the shape of a hollow spherical body, and the depth thereof is four-fifths of its diameter. At the same time, the diameter of the particle ball is one-half of the diameter of the pit; the pits are arranged in an array on the base membrane; the membrane sheet is in a strip shape and can cover one row or one column of pits on the base membrane.

[0019] S4. Preparation of membrane sheet: Take a part of the mixed sol and coat it on a second template with a flat top. After drying to a completely dry state, cut it into multiple membrane sheets for standby.

[0020] S5. Composite: Place the base membrane with the pitted side facing up, and place a particle ball in each pit respectively; then use the membrane sheet to block each particle ball in its corresponding pit, and the diameter of the particle ball is smaller than the diameter and depth of the pit; finally, take a part of the mixed sol and evenly coat it on the base membrane and the membrane sheet, and dry it to a completely dry state to obtain a tea residue composite adsorption membrane. The particle ball is a sponge ball, a rubber ball, a plastic ball or a ceramic ball. Working principle:

[0021] During use, the convex surface (the back of the pit) of the tea residue composite adsorption membrane faces the water incoming direction. When water flows through the tea residue composite adsorption membrane, the dirt in the water is adsorbed on the convex surface of the tea residue composite adsorption membrane. Since the convex surface has many protrusions, the contact area with the sewage is large, and it can efficiently filter dirt; at the same time, the tea residue composite adsorption membrane has its own effect of removing dirt, avoiding its adsorption and blocking of micropores; when water enters the pit, it will push the particle ball in the pit to move irregularly in the pit. During the movement of the particle ball, it collides with the pit wall, generating vibrations, so that the dirt just adsorbed on the convex surface of the tea residue composite adsorption membrane is detached from the tea residue composite adsorption membrane, enabling clean water to pass through the tea residue composite adsorption membrane smoothly, while the dirt remains on the convex surface side of the tea residue composite adsorption membrane, and it is not easy to block micropores, greatly improving the service time of the tea residue composite adsorption membrane. Example 3

[0022] As the usage time of the tea residue composite adsorption membrane increases, the concentration of contaminants on the convex side of the tea residue composite adsorption membrane will continuously increase, the vibration and detachment of the particle balls from the adsorbed contaminants will be less effective, and the membrane flux will also show a certain degree of attenuation. To overcome the above problems and further improve the membrane flux and the permeability effect of the tea residue composite adsorption membrane, the following settings are added based on Example 1 or 2 in this embodiment.

[0023] A micro-vibrator is also encapsulated at the edge of the tea residue composite adsorption membrane. The micro-vibrator is similar to the vibrator in a mobile phone. During use, the high-frequency vibration of the micro-vibrator not only drives the vibration of the tea residue composite adsorption membrane, but also causes the particle balls in the pits to move at high frequency within the pits, continuously hitting the tea residue composite adsorption membrane, so that the contaminants adsorbed on the surface of the tea residue composite adsorption membrane are detached, greatly improving the membrane flux.

[0024] Membrane Flux Verification Experiment I. Sample Preparation Control Group: A commercial PVDF filter membrane is used, with material parameters: pore size 0.1 μm, diameter 10 cm.

[0025] Experimental Group 1: The tea residue composite adsorption membrane prepared according to the scheme of Example 1, with material parameters: particle ball diameter / pit diameter = 40% (rubber ball).

[0026] Experimental Group 2: The tea residue composite adsorption membrane prepared according to the scheme of Example 2, with material parameters: particle ball diameter / pit diameter = 50% (rubber ball).

[0027] Experimental Group 3: The tea residue composite adsorption membrane prepared according to the scheme of Example 3, with material parameters: particle ball diameter / pit diameter = 40% (rubber ball) + micro-vibrator (100 Hz, 0.5 W).

[0028] II. Experimental Conditions

[0029] 1. Simulated Liquor Wastewater The steps to prepare 1 L of simulated liquor wastewater are as follows: Take 80 mL of absolute ethanol, 80 mL of absolute ethanol, 5 mL of glacial acetic acid, 4.0 g of diatomaceous earth, and 16.2 g of glucose and put them into a container. Then add deionized water to make up the volume to 1 L, and mix well by magnetic stirring for 30 min to obtain a simulated liquor wastewater with pH = 4.0, SS = 4000 mg / L, and COD = 18000 mg / L; then expand the volume proportionally as needed according to the above steps for standby.

[0030] Equipment Dead-end filtration device (effective membrane area 38.5 cm²), peristaltic pump (peristaltic pump set circulation flow rate 1.5 m / s), pressure sensor (pressure sensor adjusted to 0.1 MPa), electronic balance (accuracy 0.01 g, real-time record the mass of the filtrate).

[0031] III. Test Steps: Stage 1: Membrane Pretreatment 1. Immerse all membrane samples in deionized water and let stand for 12 hours.

[0032] 2. After taking out, drain the surface moisture and load it into the dead-end filtration device.

[0033] Stage 2: Initial Flux Measurement

[0034] 1. Use deionized water as the feed liquid and conduct constant pressure filtration at 0.1 MPa and 25 °C for 2 hours.

[0035] 2. Record the filtrate mass in the last 1 hour and calculate the initial flux according to the following flux formula: J = V / (T × A) Where, J represents the membrane flux (L / m²·h), V represents the sampling volume (L), T represents the sampling time (h), and A represents the effective membrane area (m²).

[0036] 3. Take the average value of three repeated experiments. Stage 3: Fouling Test

[0037] 1. Switch the feed liquid to the simulated liquor wastewater and maintain a constant pressure of 0.1 MPa.

[0038] 2. Record the filtrate mass every 15 minutes and calculate the instantaneous flux.

[0039] 3. Start the micro vibrator (100 Hz, 0.5 W) in Experimental Group 3 4. Continuously operate for 24 hours Stage 4: Flux Recovery Test (at 24 h)

[0040] 1. Pause the water inlet and remove the fouled membrane.

[0041] 2. Backwash with 50 mL of deionized water for 5 minutes (pressure 0.05 MPa) 3. Reload the device and use deionized water as the feed liquid and operate at 0.1 MPa for 1 hour.

[0042] 4. Record the filtrate mass and calculate the flux recovery rate: Stage 5: Long-term Fouling Test

[0043] 1. Switch back to the simulated liquor wastewater and continue to operate until the cumulative time reaches 30 hours.

[0044] 2. Record the final filtrate mass and calculate the final flux at 30 h according to the flux formula. IV. Experimental Results of Membrane Flux Performance Comparison

[0045] The test results obtained for each sample group (control group, experimental group 1, experimental group 2, experimental group 3) according to the above test steps are shown in Table 1.

[0046] Table 1. Comparison of membrane flux performance experimental results V. Result Analysis

[0047] Analysis based on the data in Table 1 is as follows: 1. Optimization of particle ball size The long-term flux of experimental group 2 (ball diameter / pit diameter = 50%) (135 L / m²·h) is higher than that of experimental group 1 (ball diameter / pit diameter = 40%), indicating that increasing the particle ball diameter (ball diameter / pit diameter = 50%) can enhance the collision energy, more effectively shake off pollutants, and reduce membrane fouling.

[0048] 2. Synergistic effect of the micro vibrator The flux recovery rate of experimental group 3 (40% ball diameter + vibrator) is as high as 95% at 24 h, and the final flux (158 L / m²·h) is 31.7% higher than that of experimental group 1 without a vibrator (120 L / m²·h), verifying that the vibrator can significantly activate the movement of particle balls and solve the problem of dirt accumulation during long-term operation.

[0049] 3. Comparison of the tea residue composite membrane with the existing commercial PVDF membrane The initial flux, long-term flux, and recovery rate of all experimental groups are better than those of the control group. Especially at 30 h of operation, the flux of experimental group 2 is 87.5% higher than that of the PVDF membrane, and the flux of experimental group 3 is 119.4% higher than that of the PVDF membrane. This proves that the tea residue composite membrane significantly improves the anti-fouling ability through a dynamic self-cleaning mechanism (particle ball collision + vibration).

[0050] Other details not elaborated in the present invention are conventional techniques well known to those skilled in the art.

[0051] It should be noted that the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0052] The protection scope of the present invention is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A preparation method of a tea residue composite adsorption membrane, characterized in that, It includes the following steps: Adding modified tea residue and nanofibrillated cellulose (CNF) into an aqueous solution of N-methyl morpholine (NMMO) and mixing evenly to form a mixed sol; Taking a part of the mixed sol, coating it on a first template with multiple protrusions on the top, drying it to a formed but not completely dry state, and then removing it from the template to obtain a base film with multiple pits for standby; Taking a part of the mixed sol, coating it on a second template with a flat top, drying it to a completely dry state, and then cutting it into multiple film pieces for standby; Placing the base film with the pitted side facing up, and placing a particle ball in each pit respectively; then using the film pieces to seal each particle ball in its corresponding pit, and the diameter of the particle ball is smaller than the diameter and depth of the pit; finally, taking a part of the mixed sol and evenly coating it on the base film and the film pieces, drying it to a completely dry state to obtain a tea residue composite adsorption film.

2. The preparation method of the tea residue composite adsorption membrane according to claim 1, characterized in that, The preparation steps of the modified tea residue are as follows: washing the tea residue multiple times, drying and grinding it to obtain tea residue powder for standby; mixing the tea residue powder, polyvinyl alcohol and zinc nitrate powder to obtain a mixture, then putting the mixture into a methanol solution containing methylimidazole, continuing to stir and mix evenly, after reaction and precipitation, taking the precipitate and washing it multiple times with methanol, and then successively drying and grinding to obtain the modified tea residue.

3. The preparation method of the tea residue composite adsorption membrane according to claim 2, characterized in that The mass ratio of the tea residue powder, polyvinyl alcohol, zinc nitrate and methylimidazole is 1:(0.3 - 0.6):(0.15 - 0.35):(0.8 - 1.5).

4. The preparation method of the tea residue composite adsorption membrane according to claim 2, wherein: The drying after washing the tea residue multiple times is vacuum drying at a temperature of 30 - 45°C.

5. The preparation method of the tea residue composite adsorption membrane according to claim 1, wherein: The pits on the first template are in the shape of a hollow spherical body, and its depth is four-fifths of its diameter. At the same time, the diameter of the particle ball is one-fifth to three-fifths of the diameter of the pit.

6. The preparation method of the tea residue composite adsorption membrane according to claim 1, wherein: The particle ball is a sponge ball, a rubber ball, a plastic ball or a ceramic ball.

7. The preparation method of the tea residue composite adsorption membrane according to claim 1, characterized in that: A micro vibrator is also encapsulated at the edge of the tea residue composite adsorption film.

8. The preparation method of the tea residue composite adsorption membrane according to claim 1, wherein: The pits are arranged in an array on the base film; the film pieces are strip-shaped and can cover one row or one column of pits on the base film.

9. The preparation method of the tea residue composite adsorption membrane according to claim 1, characterized in that: The mass ratio of the modified tea residue, nanofibrillated cellulose (CNF) and aqueous solution of N-methyl morpholine (NMMO) is 1:(2 - 5):(90 - 120).

10. A preparation method of a tea residue composite adsorption film, characterized in that: It is prepared by using the preparation method described in any one of claims 1 - 9.

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