Method for coating recycled water treatment waste film with viscous particles
By forming a ternary network coating of plant polyphenols and polyhydroxy chain polymers on the surface of waste water treatment membranes, the problem of decreased separation capacity of waste membranes is solved, enabling a high-efficiency and low-cost regeneration process and improving the membrane's separation performance and antifouling ability.
Patent Information
- Application Number
- CN202511911950.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-01-23
AI Technical Summary
Existing wastewater treatment membranes exhibit reduced separation capacity after contamination, and the recycling process is costly and complex. Conventional methods may damage the membrane structure and reduce performance.
Plant polyphenols and polyhydroxy chain polymers are used to form a stable ternary network with iron ions, which then self-assembles to form an adhesive particulate coating on the surface of the waste membrane, thereby improving its separation performance.
It enables the regeneration of waste membranes from water treatment, restores the separation capacity at the nanofiltration/reverse osmosis level, improves the hydrophilicity and antibacterial properties of the membrane, and reduces operating costs and complexity.
Smart Images
Figure CN121372037A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of water treatment membrane material recycling, and particularly relates to a method for recycling water treatment waste membranes by coating with sticky particles. BACKGROUND
[0002] Membrane technology has become one of the key technologies for modern water treatment due to its high energy utilization efficiency, good reliability, and strong operation stability. However, in actual operation, irreversible pollution of pollutants and structural damage caused by physical or chemical cleaning result in continuous decline of the permeation flux and selectivity of the membrane, until the service life is reached. The conventional disposal methods of water treatment waste membranes, including incineration and landfill, can cause environmental risks such as release of toxic gases and microplastics. Therefore, green recycling of waste membranes is a big difficulty. Formulating a sustainable water treatment waste membrane recycling strategy not only can extend the service life and reduce the manufacturing cost, but also can achieve the green and low-carbon environmental protection demand.
[0003] Some common methods for recycling water treatment waste membranes include chemical or physical cleaning and re-interfacial polymerization. Chemical oxidation or ultrasonic treatment can effectively remove pollutants in the membrane pores. However, these methods usually damage the polyamide selective layer and enlarge the pore structure, converting reverse osmosis or nanofiltration membranes into ultrafiltration or microfiltration membranes with lower performance. The interfacial polymerization process requires dangerous organic solvents, strict reaction conditions and expensive equipment, limiting its scalability and practical application. The self-polymerization process of polydopamine usually requires a long deposition time (more than 12 hours) and is high in cost (about $200 / kg). Therefore, there is an urgent need for a simple, fast and environmentally friendly method to treat water treatment waste membranes to regain their separation ability at the nanofiltration / reverse osmosis level, so as to achieve the regeneration purpose. SUMMARY
[0004] The purpose of the present application is to solve the problems of heavy pollution in the disposal of existing water treatment waste membranes, high cost in the recycling process of water treatment waste membranes, complex operation conditions, and poor separation ability of the recycled membranes, and to provide a method for recycling water treatment waste membranes by coating with sticky particles.
[0005] The present application repairs water treatment waste membranes by plant polyphenols and polyhydroxy chain polymers to regain their separation ability at the nanofiltration / reverse osmosis level and achieve the recycling purpose. Plant polyphenols and polyhydroxy chain polymers can self-assemble on the surface of the waste membranes and form a stable ternary network through complexation of iron ions, and utilize the pore size screening effect to achieve separation performance, thereby regaining the separation ability of the water treatment waste membranes.
[0006] A method for recycling water treatment waste membranes by coating with sticky particles is completed according to the following steps:
[0007] I. Pretreatment:
[0008] First, the waste membrane from water treatment is soaked in sodium hypochlorite solution, then taken out and soaked in citric acid solution. Next, the membrane surface is rinsed clean with deionized water to remove any remaining solution. Finally, it is soaked in deionized water to obtain the pretreated waste membrane.
[0009] II. Preparation of pre-formulated solution:
[0010] Plant polyphenols and polyhydroxy chain polymers are added to water and mixed evenly to obtain a viscous particle solution.
[0011] The plant polyphenols mentioned in step two are one or more of the following: epigallocatechin gallate, epicatechin gallate, epigallocatechin, epicatechin, tannic acid, gallic acid, and pyrogallol.
[0012] The polyhydroxy chain polymer mentioned in step two is one or both of polyvinyl alcohol and polyethylene glycol;
[0013] 3. Immerse the pretreated waste membrane in a viscous particle solution, shake it in an air atmosphere to ensure full contact, soak it for a period of time, then take out the waste membrane, blow off the residual liquid on the surface to obtain a dried waste membrane.
[0014] 4. Soak the dried waste membrane in an iron ion solution and shake it in the air to ensure full contact. Soak for a period of time to allow the sticky particles to fully cross-link and solidify with the iron ions. Then rinse with deionized water to obtain a regenerated membrane coated with sticky particles, which is then stored in deionized water.
[0015] The principle of this invention:
[0016] This invention innovatively utilizes the hydrogen-bonded self-assembly of plant polyphenols and polyhydroxy chain polymers to form viscous nano-hydrogel particles that adhere to the membrane surface. These particles then chelate iron ions to form a stable ternary coating. This ternary network, once formed, allows for separation through pore size sieving. Furthermore, plant polyphenols are commonly used green antibacterial and hydrophilic materials; the resulting ternary network coating significantly enhances the hydrophilicity and antibacterial properties of waste membranes, demonstrating promising application prospects.
[0017] Advantages of this invention:
[0018] I. This invention has a wide range of applications for waste membrane recycling;
[0019] Second, this invention is simple, adjustable, has a short cycle time, and low cost;
[0020] Third, this invention regenerates the selective separation performance of waste water treatment membranes;
[0021] IV. This invention improves the hydrophilicity, antibacterial properties, and antifouling performance of waste membranes;
[0022] V. The viscous particle-coated regenerated membrane obtained by this invention can achieve long-term stability of selective separation performance. Attached Figure Description
[0023] Figure 1 For the adhesion force of various particulate materials;
[0024] Figure 2 The surface morphology of the pretreated waste membrane obtained in step one of Example 1 and the regenerated membrane coated with viscous particles obtained in step four of Example 1 are shown.
[0025] Figure 3 The cross-sectional morphology of the viscous particle-coated regenerated membrane prepared for Example 1;
[0026] Figure 4 The pore size distribution of the regenerated membranes coated with viscous particles prepared in Examples 1, 2, and 3;
[0027] Figure 5 Salt separation performance of regenerated membranes coated with viscous particles prepared for Examples 1, 2, and 3;
[0028] Figure 6 The long-term salt separation performance of the regenerated membrane coated with viscous particles prepared in Example 1 was studied. Detailed Implementation
[0029] Specific Implementation Method 1: This implementation method is a method for coating a wastewater treatment membrane with viscous particles, which is completed according to the following steps:
[0030] I. Preprocessing:
[0031] First, the waste membrane from water treatment is soaked in sodium hypochlorite solution, then taken out and soaked in citric acid solution. Next, the membrane surface is rinsed clean with deionized water to remove any remaining solution. Finally, it is soaked in deionized water to obtain the pretreated waste membrane.
[0032] II. Preparation of pre-formulated solution:
[0033] Plant polyphenols and polyhydroxy chain polymers are added to water and mixed evenly to obtain a viscous particle solution.
[0034] The plant polyphenols mentioned in step two are one or more of the following: epigallocatechin gallate, epicatechin gallate, epigallocatechin, epicatechin, tannic acid, gallic acid, and pyrogallol.
[0035] The polyhydroxy chain polymer mentioned in step two is one or both of polyvinyl alcohol and polyethylene glycol;
[0036] 3. Immerse the pretreated waste membrane in a viscous particle solution, shake it in an air atmosphere to ensure full contact, soak it for a period of time, then take out the waste membrane, blow off the residual liquid on the surface to obtain a dried waste membrane.
[0037] 4. Soak the dried waste membrane in an iron ion solution and shake it in the air to ensure full contact. Soak for a period of time to allow the sticky particles to fully cross-link and solidify with the iron ions. Then rinse with deionized water to obtain a regenerated membrane coated with sticky particles, which is then stored in deionized water.
[0038] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the waste water treatment membrane mentioned in step one is a waste nanofiltration membrane or waste reverse osmosis membrane with polysulfone, polyethersulfone, polyvinyl chloride, or polyvinylidene fluoride as the substrate. The other steps are the same as in Specific Implementation Method One.
[0039] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: the effective chlorine concentration in the sodium hypochlorite solution mentioned in step 1 is 0.5%; and the mass fraction of the citric acid solution mentioned in step 1 is 2%. Other steps are the same as in Specific Implementation Method 1 or 2.
[0040] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: In step one, the waste membrane from water treatment is first soaked in sodium hypochlorite solution for 0-6 hours, then soaked in citric acid solution for 0-6 hours, and then rinsed with deionized water to remove any remaining solution from the membrane surface. Finally, it is soaked in deionized water for 24-48 hours to obtain the pretreated waste membrane. Other steps are the same as in Specific Implementation Methods One to Three.
[0041] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the plant polyphenols mentioned in step two are one or more of epigallocatechin gallate, epicatechin gallate, epigallocatechin, epicatechin, tannic acid, gallic acid, and pyrogallol; the polyhydroxy chain polymer mentioned in step two is one or two of polyvinyl alcohol and polyethylene glycol. Other steps are the same as in Specific Implementation Methods One to Four.
[0042] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the concentration of plant polyphenols in the viscous particulate solution described in step two is 0.1 mg / mL to 1 mg / mL; the concentration of polyhydroxy chain polymers in the viscous particulate solution described in step two is 0.1 mg / mL to 1 mg / mL. The other steps are the same as in Specific Implementation Methods One to Five.
[0043] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One to Six is that the soaking time in step three is 10 to 30 minutes. The other steps are the same as in Specific Implementation Methods One to Six.
[0044] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the iron ion solution mentioned in step four is a ferric chloride solution, a ferric sulfate solution, or a ferric nitrate solution. The other steps are the same as in Specific Implementation Methods One to Seven.
[0045] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the concentration of the iron ion solution mentioned in step four is 0.2 mg / L to 0.5 mg / L. The other steps are the same as in Specific Implementation Methods One to Eight.
[0046] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the soaking time in step four is 2 to 10 minutes; and deionized water is used to rinse 3 to 5 times in step four. Other steps are the same as in Specific Implementation Methods One to Nine.
[0047] The following examples demonstrate the beneficial effects of the present invention:
[0048] Example 1: A method for coating a wastewater treatment membrane with viscous particles is completed according to the following steps:
[0049] I. Preprocessing:
[0050] First, the waste membrane from water treatment is soaked in sodium hypochlorite solution for 4 hours, then soaked in citric acid solution for 1 hour, and then rinsed with deionized water to remove the residual solution from the membrane surface. Finally, it is soaked in deionized water for 24 hours to obtain the pretreated waste membrane (cleaned waste membrane).
[0051] The waste water treatment membrane mentioned in step one is a waste nanofiltration membrane based on polyethersulfone.
[0052] The effective chlorine concentration in the sodium hypochlorite solution mentioned in step one is 0.5%;
[0053] The citric acid solution mentioned in step one has a mass fraction of 2%;
[0054] II. Preparation of pre-formulated solution:
[0055] Tannic acid and polyvinyl alcohol are added to water and mixed evenly to obtain a viscous particle solution;
[0056] The concentration of tannic acid in the viscous particle solution described in step two is 0.5 mg / mL;
[0057] The concentration of polyvinyl alcohol in the viscous particle solution described in step two is 0.5 mg / mL;
[0058] 3. Immerse the pretreated waste membrane in a viscous particle solution, shake it in an air atmosphere to ensure full contact, soak for 15 minutes, then take out the waste membrane, blow off the residual liquid on the surface to obtain a dried waste membrane.
[0059] 4. Immerse the dried waste membrane in a 0.2 mg / L ferric chloride solution, shake it in air to ensure full contact, soak for 2 minutes to allow the sticky particles and iron ions to fully cross-link and solidify, then rinse 5 times with deionized water to obtain a regenerated membrane coated with sticky particles, which is then stored in deionized water.
[0060] Example 2: The difference between this example and Example 1 is that the concentration of polyvinyl alcohol in the viscous particle solution described in step two is 0.1 mg / mL. All other steps and parameters are the same as in Example 1.
[0061] Example 3: The difference between this example and Example 1 is that the concentration of polyvinyl alcohol in the viscous particle solution described in step two is 1.0 mg / mL. All other steps and parameters are the same as in Example 1.
[0062] Test the adhesion between the particles and the substrate:
[0063] ① Add tannic acid to water to obtain a tannic acid solution with a concentration of 0.5 mg / mL; immerse silica microspheres with a particle size of 20 μm in the tannic acid solution with a concentration of 0.5 mg / mL for 15 min, remove and dry to obtain modified silica microspheres;
[0064] ② Add polyvinyl alcohol to water to obtain a polyvinyl alcohol solution with a concentration of 0.5 mg / mL; immerse silica microspheres with a particle size of 20 μm in the polyvinyl alcohol solution with a concentration of 0.5 mg / mL for 15 min, remove and dry to obtain modified silica microspheres;
[0065] ③ Add tannic acid and polyvinyl alcohol to water and mix well to obtain a viscous particle solution; the concentration of tannic acid in the viscous particle solution is 0.5 mg / mL and the concentration of polyvinyl alcohol is 0.5 mg / mL; immerse silica microspheres with a particle size of 20 μm in the viscous particle solution for 15 min, take them out and dry them to obtain modified silica microspheres;
[0066] ④ Add tannic acid and polyvinyl alcohol to water and mix well to obtain a viscous particle solution; the concentration of tannic acid in the viscous particle solution is 0.5 mg / mL and the concentration of polyvinyl alcohol is 0.5 mg / mL; immerse silica microspheres with a particle size of 20 μm in the viscous particle solution for 15 min, remove and dry; then immerse in a ferric chloride solution with a concentration of 0.2 mg / L for 2 min, remove and dry to obtain modified silica microspheres;
[0067] Under an optical microscope, the modified silica microspheres obtained in steps ① to ④ above were attached to commercial NP-10 probes using epoxy resin adhesive. After the adhesive was allowed to dry naturally at room temperature, colloidal probes were obtained using dual-probe AFM. Adhesion force was measured in a fluid cell containing deionized water. The membrane surface was equilibrated in the fluid cell for 30 minutes before testing. Testing was conducted in tap mode to obtain data on diode voltage and cantilever displacement during approach and retraction. Where F is the adhesion force (nN), U is the diode voltage (V), and K is the probe stiffness (N·m). -1 S is the sensitivity of the probe (V·m) -1 Force measurements were performed at six different locations on the membrane surface, with at least six measurements taken at each location. The test results are shown in [the table below]. Figure 1 As shown;
[0068] Figure 1 This demonstrates the adhesion of tannic acid-polyvinyl alcohol nanoparticles to the substrate; however, after cross-linking with iron ions to form a stable ternary network, the adhesion disappears.
[0069] Figure 2 The surface morphology of the pretreated waste membrane obtained in step one of Example 1 and the regenerated membrane coated with viscous particles obtained in step four of Example 1 are shown.
[0070] Figure 3 The cross-sectional morphology of the viscous particle-coated regenerated membrane prepared for Example 1;
[0071] from Figure 2 and Figure 3 It can be seen that the nano-thickness viscous particle coating layer is uniformly deposited and solidified on the film surface and has no obvious boundary with the film surface. The tight bond between the two ensures the stability of the modified film.
[0072] Figure 4 The pore size distribution of the regenerated membranes coated with viscous particles prepared in Examples 1, 2, and 3;
[0073] Figure 4 It has been demonstrated that the nanoparticle coating can shrink the membrane pores to the nanoscale and can be separated by size sieving.
[0074] The membrane separation performance was evaluated using a membrane filtration device constructed with a STERLITECH HP4750 dead-end filtration stirred tank as the core. The membrane separation performance was assessed by evaluating the rejection rate of a 2000 ppm salt solution. Figure 5 This demonstrates that the regenerated membrane coated with the viscous particles obtained in Example 1 achieved optimal NaCl / Na2SO4 separation performance, with a separation factor as high as 54.5.
[0075] Figure 6Long-term salt separation performance of the regenerated membrane coated with viscous particles prepared in Example 1;
[0076] Figure 6 This demonstrates that the viscous particles coated with the regenerated membrane obtained in Example 1 can achieve a highly efficient separation of NaCl / Na2SO4 over a time period of up to 144 hours, with the Na2SO4 rejection rate remaining above 97% and the NaCl rejection rate remaining below 30%.
[0077] The above results demonstrate that the method of coating viscous particles to recycle waste water treatment membranes can reuse waste water treatment membranes as pressure-driven separation membranes at the nanofiltration scale.
Claims
1. A method for coating a wastewater treatment membrane with viscous particles, characterized in that... This method is completed in the following steps: I. Preprocessing: First, the waste membrane from water treatment is soaked in sodium hypochlorite solution, then taken out and soaked in citric acid solution. Next, the membrane surface is rinsed clean with deionized water to remove any remaining solution. Finally, it is soaked in deionized water to obtain the pretreated waste membrane. II. Preparation of pre-formulated solution: Plant polyphenols and polyhydroxy chain polymers are added to water and mixed evenly to obtain a viscous particle solution.
3. Immerse the pretreated waste membrane in a viscous particle solution, shake it in an air atmosphere to ensure full contact, soak it for a period of time, then take out the waste membrane, blow off the residual liquid on the surface to obtain a dried waste membrane.
4. Soak the dried waste membrane in an iron ion solution and shake it in the air to ensure full contact. Soak for a period of time to allow the sticky particles to fully cross-link and solidify with the iron ions. Then rinse with deionized water to obtain a regenerated membrane coated with sticky particles, which is then stored in deionized water.
2. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... The waste water treatment membrane mentioned in step one is a waste nanofiltration membrane or waste reverse osmosis membrane with polysulfone, polyethersulfone, polyvinyl chloride or polyvinylidene fluoride as the substrate.
3. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... The effective chlorine concentration in the sodium hypochlorite solution mentioned in step one is 0.5%; the mass fraction of the citric acid solution mentioned in step one is 2%.
4. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... In step one, the waste membrane from water treatment is first soaked in sodium hypochlorite solution for 0-6 hours, then soaked in citric acid solution for 0-6 hours, then rinsed with deionized water to remove any remaining solution from the membrane surface, and finally soaked in deionized water for 24-48 hours to obtain the pretreated waste membrane.
5. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... The plant polyphenols mentioned in step two are one or more of epigallocatechin gallate, epicatechin gallate, epigallocatechin, epicatechin, tannic acid, gallic acid, and pyrogallol; the polyhydroxy chain polymers mentioned in step two are one or two of polyvinyl alcohol and polyethylene glycol.
6. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... The concentration of plant polyphenols in the viscous particulate solution in step two is 0.1 mg / mL to 1 mg / mL; the concentration of polyhydroxy chain polymers in the viscous particulate solution in step two is 0.1 mg / mL to 1 mg / mL.
7. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... The soaking time described in step three is 10 to 30 minutes.
8. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... The iron ion solution mentioned in step four is a ferric chloride solution, a ferric sulfate solution, or a ferric nitrate solution.
9. The method for coating a wastewater treatment membrane with viscous particles according to claim 8, characterized in that... The concentration of the iron ion solution mentioned in step four is 0.2 mg / L to 0.5 mg / L.
10. The method for coating a wastewater treatment membrane with viscous particles according to claim 1, characterized in that... The soaking time in step four is 2 to 10 minutes; in step four, rinse with deionized water 3 to 5 times.