A supermolecular rapid self-assembly coating film incorporated with biochar and preparation and application thereof

Abstract

The application discloses a kind of biochar incorporation's supramolecular rapid self-assembly coating film and its preparation and application, which comprises: tannic acid and tobacco stalk biochar are dissolved in dodecyl benzene sulfonic acid aqueous solution, Tris-HCl buffer solution is added, polyethylene imine aqueous solution is added, and reaction is placed;After reaction, the stable biochar incorporation's supramolecular rapid self-assembly coating film is obtained on polyvinylidene fluoride microfiltration membrane by using polyvinylidene fluoride microfiltration membrane soaked overnight under negative pressure to extract;The pore size of the polyvinylidene fluoride microfiltration membrane is 0.22 μm.The application solves the problem that existing adsorbent is easy to cause secondary pollution to water body and is not easy to recover, completes reaction within 30s, and the prepared adsorption coating film has the performance of high adsorption rate, high organic pollutant interception rate and high permeation flux.The dynamic filtration removal rates of cationic dye CV and neutral dye RhB are more than 95% and more than 85% respectively.

Description

Technical Field

[0001] This invention relates to a method for preparing a coated film, specifically to a biochar-incorporated supramolecular rapid self-assembly coated film and its preparation and application. Background Technology

[0002] In the leather, textile, and printing industries, ionic and nonionic organic dyes are widely used in coloring processes. However, these industries often fail to adequately treat the wastewater generated after the dyeing process, discharging it directly into water bodies. Studies have shown that due to the high coloring power of dyes, even extremely low concentrations are sufficient to cause water pollution. Dyes in water bodies not only threaten aquatic ecosystems but can also pose serious risks to human health. Furthermore, the derivatives produced during dye degradation are often more toxic than the original dyes. Therefore, the treatment of dye-containing wastewater is particularly urgent and important to mitigate its potential negative impacts on the environment and public health.

[0003] Numerous studies have evaluated various technologies for removing dyes from water, including chemical methods (such as oxidation, chemisorption, and electrochemical degradation), biological processes (i.e., aerobic or anaerobic bioremediation technologies), and physical methods (such as physisorption, ion exchange, coagulation, and membrane-based processes). Among these technologies, physical methods are favored due to their ease of operation and high removal efficiency. These methods can effectively remove dye molecules from water through adsorption, ion exchange, or membrane separation, providing a practical solution for the water treatment field. Existing literature 1 (A. Ghaffar, X. Zhu, B. Chen, Biochar composite membrane for high performance pollutant management: Fabrication, structural characteristics and synergistic mechanisms, Environmental Pollution 233 (2018) 1013–1023) prepared a biochar-based blended PVDF membrane using the thermal phase inversion (TPI) method. 17% PVdF and 1% PVP were dissolved in 82% DMAc, and the solution was continuously stirred at 70°C to obtain a homogeneous solution. This blending method also presents a challenge for preparing microfiltration / ultrafiltration membranes with different pore sizes. Reference 2 (L. Huang, Z. Li, Y. Luo, N. Zhang, W. Qi, E. Jiang, J. Bao, X. Zhang, W. Zheng, B. An, G. He, Low-pressure loose GO composite membrane intercalated by CNT for effective dye / salt separation, Separation and Purification Technology 256(2021)117839) mixed prepared graphene oxide dispersion (0.02 mg / mL) and carbon nanotube (CNT) dispersion (0.02 mg / mL) under ice-water bath conditions to prepare graphene oxide laminates with different carbon nanotube contents. The obtained CNT / GO dispersion was filtered through a CA substrate at room temperature by pressure filtration, which took several hours to obtain CNT@GO laminates. After deposition, the CNT@GO laminates were crosslinked with MXDA in an oven at 80°C for 1 hour to obtain crosslinked CNT@GO (c-CNT@GO) films. Reference 2 describes an extreme environment for CNT incorporation, namely high energy consumption (ice-water bath, 80°C thermal crosslinking), but the reaction time involved is relatively long (1 hour of crosslinking).Reference 3 (H.-L. Chen, M.-S. Hsiao, Self-Assembled Mesomorphic Complexes of Branched Poly(ethylenimine) and Dodecylbenzenesulfonic Acid, Macromolecules 32(1999)2967–2973) prepared PEI (DBSA) complexes by mixing the required amounts of polyetherimide (PEI) and 3,5-dibromosalicylic acid aldehyde (DBSA) with water at room temperature. Experiments showed that the high branching level of the PEI chains did not disrupt the ordered stacking of the alkyl tails in the complexes. Due to chain stiffening, the glass transition of PEI increased due to complexation, and the thermal stability of PEI was also enhanced, with the degradation temperature increasing by up to 50 °C.

[0004] Furthermore, to further improve the permeation performance of separation membranes, pore-forming agents are typically introduced during membrane manufacturing. Commonly used agents, such as PEG and PVP, are frequently used in the preparation of membrane materials using NIPs and TIPs methods. These agents remove the pore-forming agent from the matrix through a phase inversion process, thereby forming membrane pores. In the preparation of ceramic membranes, inorganic pore-forming agents include inorganic salts such as sodium carbonate and calcium carbonate; organic pore-forming agents include natural fibers and polymers, including starch, polymethyl methacrylate (PMMA), and porous organic cages. Existing adsorbents are a highly efficient water treatment method, but they are prone to causing secondary pollution to water bodies and are difficult to recycle. Therefore, there is an urgent need to modify and optimize traditional adsorbents to facilitate recycling and regeneration. Biomass-based biochar, with its porous structure, is a green and stable porous material regenerated from agricultural and forestry waste. Introducing it as a pore-forming agent into coatings is expected to improve the permeation performance of separation membranes. Summary of the Invention

[0005] The purpose of this invention is to provide a biochar-incorporated supramolecular rapid self-assembly coated membrane and its preparation and application. This invention solves the problems of existing adsorbents easily causing secondary pollution to water bodies and being difficult to recycle. Under low-energy consumption conditions at ambient temperature and pressure, based on the cross-linking effect between tannic acid (TA) and dodecylbenzenesulfonic acid (DBSA) / polyethyleneimine (PEI) supramolecular self-assembly complex, and by stably incorporating biochar as a "porogen" (to improve the permeation flux of the dense coating membrane), the coating can be rapidly prepared in a "one-pot" method. The resulting adsorption coating separation membrane has the advantages of high flux and high adsorption efficiency.

[0006] To achieve the above objectives, the present invention provides a method for preparing a biochar-incorporated supramolecular rapid self-assembly coating film, the method comprising:

[0007] (1) Dissolve tannic acid and tobacco straw biochar (BC) in a dodecylbenzene sulfonic acid aqueous solution, add Tris-HCl buffer, add polyethyleneimine aqueous solution, and let the reaction stand ("one-pot method" for rapid polymer preparation).

[0008] (2) After the reaction was completed, the membrane was filtered under negative pressure using a polyvinylidene fluoride microfiltration membrane that had been soaked overnight, and a stable biochar-infused supramolecular rapid self-assembly coating membrane was obtained on the polyvinylidene fluoride microfiltration membrane.

[0009] The polyvinylidene fluoride microfiltration membrane has a pore size of 0.22 μm.

[0010] DBSA concentration, PEI concentration, TA addition amount, BC addition amount, and reaction time are all major factors affecting the product structure. DBSA concentration affects the number of adsorption sites and the degree of polymerization of the coating polymer; PEI concentration affects the degree of polymerization of the coating polymer; TA addition amount affects the number of adsorption sites and the degree of polymerization of the coating polymer; BC addition amount affects the pore size of the coating; and reaction time affects the degree of polymerization of the coating polymer. Among these, the degree of polymerization has a significant impact on the permeation flux.

[0011] Preferably, in step (1), the mass-to-volume ratio of tannic acid to dodecylbenzenesulfonic acid aqueous solution is (1-20) mg: 20 mL, and the concentration of dodecylbenzenesulfonic acid aqueous solution is 0.1 g / L to 2 g / L.

[0012] Preferably, in step (1), the pH of the Tris-HCl buffer solution is 8.5; the volume ratio of the polyethyleneimine aqueous solution to the dodecylbenzenesulfonic acid aqueous solution is 4:1; the volume ratio of the Tris-HCl buffer solution to the polyethyleneimine aqueous solution is 1:1; and the concentration of the polyethyleneimine aqueous solution is 0.5 g / L to 3 g / L.

[0013] Preferably, in step (1), the reaction time is 30 s. TA-DBSA / PEI polymerization is completed within 30 s. Furthermore, the coating polymer reaction occurs after 30 s, and increasing the reaction time does not significantly improve the throughput.

[0014] Preferably, in step (2), the negative pressure is 0.4 bar.

[0015] Preferably, the mass ratio of the tobacco straw biochar to tannic acid is (1-20):(5-20).

[0016] More preferably, the mass ratio of the tobacco straw biochar to tannic acid is 5:10.

[0017] This invention provides a biochar-incorporated supramolecular rapid self-assembly coating film prepared by the method described above.

[0018] Preferably, the biochar-incorporated supramolecular rapid self-assembly coating film has a porous structure inside the coating and contains PEI segments.

[0019] This invention provides an application of a biochar-incorporated supramolecular rapid self-assembly coated membrane in separation and purification.

[0020] This invention discloses a biochar-incorporated supramolecular rapid self-assembly coated membrane, its preparation and application, which solves the problems of existing adsorbents easily causing secondary pollution to water bodies and being difficult to recycle, and has the following advantages:

[0021] 1. This invention, under low-energy consumption conditions at ambient temperature and pressure, utilizes the supramolecular self-assembly reaction between DBSA and PEI, and the cross-linking reaction between TA and PEI. These three components can react rapidly within 30 seconds to generate a high-molecular-weight, flocculent, stable TA-DBSA / PEI supramolecular self-assembled composite. Furthermore, biochar is stably incorporated as a "porogen" to improve the permeation flux of the dense coating membrane and form a stable deposited coating on the membrane surface.

[0022] 2. The adsorption coating membrane prepared by this invention has high adsorption rate, high organic pollutant rejection rate, and high permeation flux, exhibiting excellent adsorption effect on organic pollutants. The incorporated biochar powder acts as a "porogen" and "adsorbent," synergistically adsorbing azo dye organic pollutants while also assisting in regulating the membrane's permeation performance. Under the premise of ensuring high separation efficiency, the increased permeation flux is beneficial for large-scale wastewater treatment. The dynamic filtration removal rates of this TA-DBSA / PEI-BC membrane for cationic dye CV and neutral dye RhB reach over 95% and over 85%, respectively.

[0023] 3. The TA and BC involved in this invention are both green biomass materials. The coating preparation method is simple, fast, and mild, and the reaction can be completed within 30 seconds, thereby greatly shortening the material preparation time. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the preparation of the adsorption coating film according to the present invention.

[0025] Figure 2 The images show SEM images of the PVDF original film, the cross-section of the TA-DBSA / PEI-BC adsorption coating film, and the BC powder of Examples 3 and 6 of the present invention.

[0026] Figure 3 The present invention uses ATR-FTIR to characterize the original PVDF membranes and two modified membranes of Examples 3 and 6.

[0027] Figure 4The graph shows the test results of the AFM and contact angle of the original membrane with pure water in Examples 3 and 6 of this invention.

[0028] Figure 5 The graph shows the test results of the AFM and pure water contact angle of TA-DBSA / PEI in Examples 3 and 6 of this invention.

[0029] Figure 6 The graph shows the test results of the AFM contact angle between the TA-DBSA / PEI-BC and pure water in Examples 3 and 6 of this invention.

[0030] Figure 7 The graph shows the test results of the hydrophilicity of the membrane surface in Examples 3 and 6 of the present invention.

[0031] Figure 8 The figure shows the test results of the effect of the apparent characteristics of the three polymer-coated membranes in Example 11 of the present invention on the membrane permeation flux.

[0032] Figure 9 The graph shows the test results of the effect of reaction time on membrane permeation flux of the three polymer-coated membranes in Example 11 of the present invention.

[0033] Figure 10 The figure shows the test results of the effect of different DBSA concentrations on dye removal rate and membrane flux in Comparative Example 2 of this invention.

[0034] Figure 11 The figure shows the test results of the effect of different PEI concentrations on dye removal rate and membrane flux in Example 10 of the present invention.

[0035] Figure 12 The graph shows the test results of the effect of different TA contents on dye removal rate and membrane flux in Examples 1-5 of the present invention.

[0036] Figure 13 The graph shows the test results of the effect of different BC contents on dye removal rate and membrane flux in Examples 1 and 6-9 of this invention.

[0037] Figure 14 The effect of removing simulated dyes in the membrane filtration dynamic separation test of Examples 3 and 6 of the present invention is shown.

[0038] Figure 15 The effect of smearing simulated dyes on membrane static tests in Examples 3 and 6 of the present invention. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The materials involved in the following embodiments are as follows:

[0041] Materials and equipment: The membrane filtration test used a membrane with a total volume of 50 mL and an effective area of ​​10.18 cm². 2 Dead-end filtration device (purchased from Shanghai Mosu Scientific Instruments Co., Ltd., model MSC05050 ml); specific surface area and porosity analyzer (purchased from Micron, model Gemini VII 2390).

[0042] The tobacco waste straw originated from Shifang City, Sichuan Province.

[0043] Tannic acid (TA), dodecylbenzenesulfonic acid (DBSA), and polyethyleneimine (PEI) were purchased from Macklin Biochemical Co., Ltd. (Shanghai, China); CV (96% purity) and RhB dye (85% purity) were purchased from Chengdu Kelong Chemical Co., Ltd.; all the above reagents did not require further purification after purchase.

[0044] Preparation method of Tris-HCl solution (pH 8.5): Weigh 121.1g of Tris base and add it to 800mL of deionized water, and stir thoroughly to dissolve it. Adjust the pH of the solution to 8.5 using hydrochloric acid solution.

[0045] The PVDF microfiltration membrane, with a pore size of 0.22μm, was purchased from Haining Kezhun Filtration Equipment Co., Ltd.

[0046] Preparation method of tobacco straw biochar (BC): Recycled tobacco straw is washed, dried, and pulverized. The powder is then passed through a 0.45 mm sieve. The tobacco straw powder is placed in a tube furnace, and the temperature of the furnace is continuously increased to 500℃ at a rate of 10℃ / min and maintained for 2 hours. Subsequently, the obtained char powder is washed three times repeatedly with pure water until the pH of the washing water remains stable (pH close to 7), and then dried in an oven at 85℃ for 10 hours.

[0047] Example 1

[0048] A method for preparing a biochar-incorporated supramolecular rapid self-assembly coated film, such as... Figure 1 The diagram shows a schematic of the preparation of the adsorption coating film according to the present invention. The method includes:

[0049] (1) Immerse a dry PVDF microfiltration membrane in deionized water overnight.

[0050] (2) Dissolve 1 mg of tannic acid (TA) and 5 mg of tobacco straw biochar (BC) in 20 mL of 1 g / L DBSA aqueous solution, add 5 mL of Tris-HCl (pH 8.5) buffer solution, add 5 mL of 1.5 g / L PEI aqueous solution, let stand for 5 min, after the reaction is completed, filter under 0.4 bar negative pressure using the PVDF microfiltration membrane that was left overnight in step (1), and obtain a stable biochar-incorporated supramolecular rapid self-assembly coating membrane on the PVDF microfiltration membrane, which is denoted as TA-DBSA / PEI-BC adsorption coating membrane.

[0051] After the coating film is left to air dry, wash it with pure water and store it in a dark and dry environment.

[0052] Example 2

[0053] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0054] In step (2), the mass of TA is adjusted from 1 mg to 5 mg.

[0055] Example 3

[0056] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0057] In step (2), the mass of TA is adjusted from 1 mg to 10 mg.

[0058] Example 4

[0059] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0060] In step (2), the mass of TA is adjusted from 1 mg to 15 mg.

[0061] Example 5

[0062] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0063] In step (2), the mass of TA is adjusted from 1 mg to 20 mg.

[0064] Example 6

[0065] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0066] In step (2), the mass of TA is adjusted from 1 mg to 10 mg, and 5 mg of tobacco straw biochar (BC) is not added. The same operation is performed to obtain a biochar-incorporated supramolecular rapid self-assembly coating membrane, which is denoted as TA-DBSA / PEI adsorption coating membrane.

[0067] Example 7

[0068] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0069] In step (2), the mass of TA is adjusted from 1 mg to 10 mg, and the mass of BC is adjusted from 5 mg to 10 mg.

[0070] Example 8

[0071] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0072] In step (2), the mass of TA is adjusted from 1 mg to 10 mg, and the mass of BC is adjusted from 5 mg to 15 mg.

[0073] Example 9

[0074] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0075] In step (2), the mass of TA is adjusted from 1 mg to 10 mg, and the mass of BC is adjusted from 5 mg to 20 mg.

[0076] Comparative Example 1

[0077] A method for preparing a TA-PEI polymer, the method comprising:

[0078] Dissolve 10 mg TA in 20 ml of 1 g / L DBSA aqueous solution, add 5 ml of Tris-HCl (pH 8.5) buffer, add 5 ml of prepared 1.5 g / L PEI aqueous solution, let stand for 1 s, 30 s, or 300 s, and record the state of the mixture.

[0079] Comparative Example 2

[0080] A method for preparing a DBSA / PEI polymer, the method comprising:

[0081] Add 5 ml of Tris-HCl (pH 8.5) buffer to 20 ml of 1 g / L DBSA aqueous solution, then add 5 ml of 1.5 g / L PEI aqueous solution. Allow the mixture to stand for 1 s, 30 s, or 300 s and record the state of the mixture.

[0082] Example 10

[0083] The preparation method of a TA-DBSA / PEI adsorption coating film is basically the same as that in Example 1, except that:

[0084] In step (2), the mass of TA is adjusted from 1 mg to 10 mg, and the concentration of the PEI aqueous solution is adjusted from 1 g / L to 0.5 g / L, 2.0 g / L or 3.0 g / L, while the volume remains unchanged.

[0085] Example 11

[0086] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0087] In step (2), the mass of TA is adjusted from 1 mg to 10 mg, the mass of BC is adjusted from 5 mg to 20 mg, and the reaction time is adjusted from 5 min to 1 s, 30 s or 300 s.

[0088] Comparative Example 2

[0089] The preparation method of a biochar-incorporated supramolecular rapid self-assembly coating film is basically the same as that in Example 1, except that:

[0090] In step (2), the mass of TA is adjusted from 1 mg to 10 mg, 5 mg of tobacco straw biochar (BC) is not added, and the concentration of DBSA aqueous solution is adjusted from 1 g / L to 0.1 g / L, 0.5 g / L, 1.5 g / L or 2.0 g / L, while the volume remains unchanged. The same operation is performed to obtain a supramolecular rapid self-assembly coating membrane with biochar incorporation, which is denoted as TA-DBSA / PEI adsorption coating membrane.

[0091] Experimental Example 1: Characterization of TA-DBSA / PEI-BC Adsorption Coating Film

[0092] 1. SEM and FTIR characterization

[0093] This invention uses field emission scanning electron microscopy (FESEM, S4800, Hitachi, Japan) to observe the surface morphology of the modified films TA-DBSA / PEI and TA-DBSA / PEI-BC prepared in Example 6 and Example 3, respectively, and uses Fourier transform attenuated total reflectance infrared spectroscopy (ATR-FTIR, Thermo Scientific, Nicolet iS50) to analyze the functional groups of the TA-DBSA / PEI-BC adsorption coating films prepared in Example 6...

[0094] like Figure 2The images show SEM images of the PVDF original membrane, the TA-DBSA / PEI-BC adsorption coating membrane cross-section, and BC powder of Examples 3 and 6 of this invention. (a) is the PVDF original membrane of Example 6, (b) is the TA-DBSA / PEI adsorption coating membrane of Example 3, (c) is the TA-DBSA / PEI-BC adsorption coating membrane, (d) is an internal cross-sectional image of the coating, (e) shows the prepared BC, and (f) shows EDS energy dispersive spectroscopy and elemental analysis. Figure 2 As shown in (a), the original PVDF film exhibits a uniform porous structure; Figure 2 As shown in (b), without BC incorporation, the TA-DBSA / PEI adsorption coating film, after initial modification, exhibits a uniform and dense surface (dense coatings are more suitable for removing dyes through static adsorption due to their poor permeability); Figure 2 As shown in (c), after incorporating BC powder, the porous structure introduced by BC can be easily observed on the surface of the TA-DBSA / PEI-BC adsorption coating membrane (high-flux separation membranes are more conducive to large-scale production in removing dyes). Figure 2 As shown in (d), the cross-sectional image also reveals the porous structure distributed within the coating, which to some extent reduces the mass transfer resistance during membrane permeation. Figure 2 As shown in (e), the prepared BC exhibits rod-shaped porous particles. Figure 2 As shown in (f), EDS indicates that BC is mainly composed of C, while also containing trace amounts of O, Ca, and K. Figure 2 The elemental distribution diagram of C, Ca, O, and K in the biochar shows that these elements are evenly distributed on the surface of the biochar.

[0095] like Figure 3 As shown, the present invention uses ATR-FTIR to characterize the original PVDF films of Examples 3 and 6, as well as the two modified films. The results show that at a wavelength of 2921 cm⁻¹... -1 At this point, TA-DBSA / PEI and TA-DBSA / PEI-BC exhibit characteristic peaks of aliphatic CH2, and both show peaks in the 1000-1200 cm⁻¹ range. -1 The presence of characteristic SO peaks at 1705 cm⁻¹ indicates that DBSA participated in the polymer coating reaction. -1 At this point, C=O characteristic peaks were detected in both, indicating that TA was also polymerized in the coating. At a wavelength of 3371 cm⁻¹... -1 At the location, the characteristic peak of -NH2- was detected in both, indicating the presence of PEI segments in the coating.

[0096] 2. AFM characterization

[0097] This invention uses atomic force microscopy (AFM, Bruker AXS) to characterize the surface roughness of the original membrane and the membranes prepared in Examples 6 and 3 (TA-DBSA / PEI and TA-DBSA / PEI-BC). The hydrophilicity of the membrane surface is studied by measuring the water contact angle using an SL 200KB, Kino, USA.

[0098] like Figure 4 The figure shows the test results of the AFM and pure water contact angle of the original membranes in Examples 3 and 6 of the present invention.

[0099] like Figure 5 The figure shows the test results of the AFM and pure water contact angle of TA-DBSA / PEI in Examples 3 and 6 of the present invention.

[0100] like Figure 6 The figure shows the test results of AFM and pure water contact angle of TA-DBSA / PEI-BC in Examples 3 and 6 of the present invention, where TA-DBSA / PEI-BC is a TA-DBSA / PEI modified coating film doped with biochar.

[0101] like Figure 7 The figure shows the test results of the hydrophilicity of the membrane surface in Examples 3 and 6 of the present invention.

[0102] Depend on Figures 4-7 It is evident that the rapid supramolecular polymerization coating of TA-DDBS / PEI at the PVDF membrane surface exhibits low roughness, approaching that of the original membrane (a stable and homogeneous coating); however, the surface roughness of the TA-DDBS / PEI-BC membrane is significantly increased. Pure water contact angle tests indicate that the hydrophilicity relationship of the membrane surfaces is: original membrane < TA-DDBS / PEI membrane < TA-DDBS / PEI-BC membrane. Furthermore, the increase in membrane surface roughness is beneficial for enhancing membrane surface hydrophilicity. It is generally accepted that in the separation and purification of organic pollutants / water systems, increased membrane surface hydrophilicity is beneficial for improving antifouling capabilities.

[0103] Experiment Example 2: Effect of polymerization time on TA-DBSA / PEI-BC polymer coating film

[0104] After the adsorption coating prepared in Example 11 was allowed to stand and air-dry, it was washed with pure water and stored in a dark and dry environment to measure its pure water permeation flux and investigate the effect of polymerization time on the TA-DBSA / PEI-BC polymer coating film.

[0105] The test method for pure water permeate flux: Filtration was performed on a laboratory-scale dead-end filtration device with an effective filtration area of ​​10.18 cm². 2At 25°C, after pre-compressing the membrane at 2 bar for 30 min, the pure water flux was measured at 0.2 bar. The pure water permeation flux J was calculated using the following formula:

[0106]

[0107] In equation (1), Δt is a certain time interval, V(L) is the permeation volume Δt(h) at 5-minute intervals, and A is the effective membrane area in m². 2 .

[0108] like Figure 8 The figure shown is a test result diagram of the effect of the apparent characteristics of the three polymer-coated membranes of Example 11 of the present invention on the membrane permeation flux.

[0109] like Figure 9 The figure shown illustrates the test results of the effect of reaction time on membrane permeation flux for the three polymer-coated membranes of Example 11 of this invention. Figures 8-9 It is evident that TA-DBSA / PEI exhibits a higher degree of polymerization and completes polymerization within 30 seconds. Furthermore, the coating polymer reaction occurs after 30 seconds, and increasing the reaction time does not significantly improve the flux. Therefore, this coating membrane can be rapidly prepared in a short time.

[0110] Experimental Example 3: Effect of DBSA and PEI concentrations on TA-DBSA / PEI polymer coating film

[0111] The adsorption-coated membrane prepared in Comparative Example 2 was allowed to air dry, washed with pure water, and stored in a dark, dry environment to measure its pure water permeation flux (measured using the same method as in Experimental Example 2) and dye removal rate, thus investigating the effect of DBSA concentration on the TA-DBSA / PEI polymer coating membrane. The adsorption-coated membrane prepared in Example 10 was also allowed to air dry, washed with pure water, and stored in a dark, dry environment to measure its pure water permeation flux and dye removal rate, thus investigating the effect of PEI concentration on the TA-DBSA / PEI polymer coating membrane.

[0112] Test method for simulated dynamic filtration removal effect of dyes: Using CV, RhB, and MB as model dyes, the adsorption behavior of the coated membrane was studied. The absorbance of the supernatant was measured at 582 nm, 554 nm, and 664 nm using a UV-Vis spectrophotometer (UV 1800, Shimadzu). Calibration curves constructed using standard solutions of different concentrations were used to determine the unadsorbed CV, RhB, and MB. In the membrane filtration dynamic separation experiment, the prepared CV (10 mg / L), RhB (10 mg / L), and MB (10 mg / L) solutions were used as simulated wastewater, and then filtered using the coated membrane in a vacuum-compressed pump-driven dead-end filtration device. The residual dye concentration and retention ratio were calculated for every 50 ml of filtrate collected as follows:

[0113]

[0114] In equation (2), C f C0 and C0 represent the concentrations of dye in the filtrate and simulated wastewater, respectively.

[0115] Test method for simulating the static adsorption effect of dyes: Place the original membrane and the modified membrane in 50 ml of 1 g / L CV, RhB, and MB dye solutions. The detection method is the same as described above. Calculate the equilibrium adsorption capacity q. e as follows:

[0116]

[0117] In equation (3), C0 (mg / L) and C e (mg / L) represents the initial concentration of CV and the adsorption equilibrium concentration of RhB, respectively; V(L) is the volume of the dye solution; m(g) is the mass of the original or modified membrane.

[0118] like Figure 10 As shown in the figure, this invention's comparative example 2 presents the test results of the effect of different DBSA concentrations on dye removal rate and membrane flux. (From...) Figure 10 It is evident that DBSA contributes positively to membrane flux at low concentrations, but the flux loss becomes severe as the concentration continues to increase. However, excessively low concentrations lead to poor coating stability and easy detachment. For CV and RhB dye removal rates, increasing DBSA concentration is beneficial for dye removal, primarily because the hydrophobic chains of DBSA facilitate hydrophobic interactions with the alkyl groups in the dye.

[0119] like Figure 11 The figure shown illustrates the test results of the effect of different PEI concentrations on dye removal rate and membrane flux in Example 10 of this invention. Figures 10-11 It can be seen that the coating membrane exhibits the highest permeation flux and relatively high dye removal rate when the concentrations are 1 g / L DBSA and 1.5 g / L PEI. Since PEI does not provide active sites for adsorbing CV and RhB, the amount of PEI added has little effect on the removal effect, mainly playing a role in segmental polymerization.

[0120] Experiment Example 4: Effects of different TA and BC contents on dye removal rate and membrane flux

[0121] The effects of different TA and BC contents on dye removal rate and membrane flux were investigated, and the removal effect on simulated dyes in the dynamic separation test of membrane filtration was detected. The experimental method was the same as that in Experiment 3 above.

[0122] like Figure 12The figure shows the test results of the effect of different TA contents on dye removal rate and membrane flux in Examples 1-5 of the present invention.

[0123] like Figure 13 The figure shows the test results of the effect of different BC contents on dye removal rate and membrane flux in Examples 1 and 6-9 of this invention. Figures 12-13 It can be seen that, regarding the amount of TA, the membrane flux increases with increasing TA, while the removal rates of both dyes show a trend of first increasing and then decreasing. Regarding the amount of BC, the membrane flux increases with increasing BC. The increase in flux is due to two main reasons: firstly, the increased degree of polymerization from TA leads to a larger polymer volume, resulting in less blockage of the membrane pores by low molecular weight polymers, thus creating a coating with lower mass transfer resistance; secondly, BC occupies space in the coating and introduces a porous structure. However, excessive TA and BC lead to decreased coating stability and varying degrees of cracking, which can cause dye leakage and is detrimental to the long-term preservation and use of the membrane. Therefore, 10 mg TA and 5 mg BC are considered suitable dosages.

[0124] like Figure 14 As shown, the membrane filtration dynamic separation test in Examples 3 and 6 of this invention demonstrates the removal effect on simulated dyes. Both the TA-DBSA / PEI membrane and the TA-DBSA / PEI-BC membrane exhibit good removal effects for both CV and RhB. Especially for CV dyes, the removal rate reaches over 95%.

[0125] like Figure 15 As shown, the membrane static test results of Examples 3 and 6 of the present invention demonstrate the effect on the removal of simulated dyes. Figure 15 It was found that the TA-DBSA / PEI membrane and the TA-DBSA / PEI-BC membrane reached adsorption equilibrium after being immersed in 1 g / L of different dyes for 24 hours. The results showed that their adsorption capacities for CV and RhB both reached approximately 18 mg / g or higher, with the TA-DBSA / PEI-BC membrane showing an equilibrium adsorption capacity of 20.089 mg / g for CV. Both membranes also showed adsorption capacities for MB of approximately 6.5 mg / g or higher.

[0126] Experimental Example 5: BET Specific Surface Area Detection

[0127] The present invention uses a fully automated rapid specific surface area and porosity analyzer (Gemini VII 2390) to characterize the specific surface area and porosity of the original membrane and the membranes prepared in Examples 6 and 3 (TA-DBSA / PEI and TA-DBSA / PEI-BC). The results are detailed in Table 1.

[0128] Table 1. BET test results of the original membrane, TA-DBSA / PEI membrane, and TA-DBSA / PEI-BC membrane of this invention.

[0129]

[0130]

[0131] As shown in Table 1, the isotherms of the three membranes conform to type II adsorption, and their specific surface areas are not significantly different, all being predominantly mesoporous structures. However, compared to the modified membrane without BC doping, the pore size of the modified membrane with BC doping is significantly increased, which is beneficial for water permeability filtration and provides more adsorption sites.

[0132] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a biochar-incorporated supramolecular rapid self-assembly coated film, characterized in that, The method includes: (1) Dissolve tannic acid and tobacco straw biochar in a dodecylbenzene sulfonic acid aqueous solution, add Tris-HCl buffer, add polyethyleneimine aqueous solution, and let the reaction stand. (2) After the reaction was completed, the membrane was filtered under negative pressure using a polyvinylidene fluoride microfiltration membrane that had been soaked overnight, and a stable biochar-infused supramolecular rapid self-assembly coating membrane was obtained on the polyvinylidene fluoride microfiltration membrane. The polyvinylidene fluoride microfiltration membrane has a pore size of 0.22 μm.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of tannic acid to dodecylbenzenesulfonic acid aqueous solution is (1-20) mg: 20 mL, and the concentration of dodecylbenzenesulfonic acid aqueous solution is 0.1 g / L to 2 g / L.

3. The preparation method according to claim 1, characterized in that, In step (1), the pH of the Tris-HCl buffer solution is 8.5; the volume ratio of the polyethyleneimine aqueous solution to the dodecylbenzenesulfonic acid aqueous solution is 4:

1.

4. The preparation method according to claim 3, characterized in that, The volume ratio of the Tris-HCl buffer solution to the polyethyleneimine aqueous solution is 1:1; the concentration of the polyethyleneimine aqueous solution is 0.5 g / L to 3 g / L.

5. The preparation method according to claim 1, characterized in that, In step (2), the negative pressure is 0.4 bar.

6. The preparation method according to claim 5, characterized in that, The mass ratio of tobacco straw biochar to tannic acid is (1-20):(5-20).

7. The preparation method according to claim 6, characterized in that, The mass ratio of tobacco straw biochar to tannic acid is 5:

10.

8. A biochar-incorporated supramolecular rapid self-assembly coating film prepared by the preparation method according to any one of claims 1 to 7.

9. The biochar-incorporated supramolecular rapid self-assembly coating film according to claim 8, characterized in that, The biochar-incorporated supramolecular rapid self-assembly coating film has a porous structure inside the coating, and PEI segments are present in the coating.

10. The application of a biochar-incorporated supramolecular rapid self-assembly coated membrane as described in claim 8 in separation and purification.

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