Modified straw lignin-based fiber membrane, preparation method thereof and application of modified straw lignin-based fiber membrane in CO2 adsorption
By introducing polyvinylpyrrolidone into straw lignin fiber membranes and using electrospinning technology, modified fiber membranes with porous or hollow structures were prepared, solving the problem of insufficient CO2 adsorption performance of straw lignin fiber membranes and achieving a highly efficient CO2 capture effect.
Patent Information
- Application Number
- CN202511860399.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-02-10
AI Technical Summary
Existing straw lignin fiber membranes lack defective structures in terms of CO2 adsorption performance, resulting in insufficient surface activity and difficulty in efficiently capturing CO2.
By adding polyvinylpyrrolidone to the spinning solution, porous, hollow, or hollow-porous modified straw lignin fiber membranes were prepared using electrospinning technology, thereby enhancing surface activity and adsorption performance.
The prepared modified straw lignin fiber membrane exhibits excellent CO2 adsorption performance, realizing high-value utilization of straw resources and improving CO2 capture efficiency.
Smart Images
Figure CN121490740A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lignin fiber membrane technology, specifically relating to a modified straw lignin-based fiber membrane, its preparation method, and its application in CO2 adsorption. Background Technology
[0002] Rice, as one of the most important crops today, has a global annual production of trillions of tons. This also generates a large amount of rice byproducts such as rice husks and straw, with straw being the most abundant. Therefore, how to properly utilize such a large quantity of straw has become a major agricultural and environmental issue. Because rice straw has very few direct uses, its disposal methods in the past have mainly involved burning or composting, which undoubtedly causes enormous environmental pollution and resource waste. Therefore, in recent years, researchers have begun to explore extracting the main components of rice straw for secondary processing.
[0003] Rice straw is mainly composed of natural polymers such as cellulose, lignin, and hemicellulose. The degree of polymerization of these natural polymers is slightly lower than that of artificial polymers, but they are cheaper and more widely available. Therefore, some scholars have begun to use rice straw cellulose for electrospinning. However, there is still not much research on the development of electrospinning of straw lignin. In order to realize the high-value utilization of rice straw, more in-depth research is needed on the application prospects of straw lignin.
[0004] As people become more reliant on fossil fuels, more and more CO2 is being produced, causing a severe greenhouse effect. To address this problem, it is necessary to develop suitable materials to capture CO2 from the air. Straw lignin molecules contain active groups such as C=O, -OH, and benzene rings, which have the potential to adsorb CO2. Furthermore, preparing straw lignin into nanofiber membranes through electrospinning will undoubtedly amplify this potential due to the increased surface activity.
[0005] However, lignin fiber membranes (LFMs) lack defect structures to accommodate CO2 molecules due to their uniform fiber morphology. Therefore, LFMs need to be modified to further increase their surface activity. Based on this, this patent application is filed. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a modified straw lignin-based fiber membrane, its preparation method, and its application in CO2 adsorption.
[0007] This invention provides the following technical solution:
[0008] This invention provides a method for preparing a modified straw lignin-based fiber membrane, comprising the following steps:
[0009] S1, provides straw lignin;
[0010] S2. Preparation of modified lignin fiber membranes, including:
[0011] Preparation of porous lignin fiber membrane: Polyvinylpyrrolidone and straw lignin are added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile, and fiber membrane is obtained by single needle spinning. The fiber membrane is then subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane, thus obtaining a porous lignin fiber membrane.
[0012] and / or
[0013] Preparation of hollow lignin fiber membrane: Straw lignin was added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile to obtain a shell spinning solution; polyvinylpyrrolidone was added to N,N-dimethylformamide to obtain a core spinning solution; the shell spinning solution and the core spinning solution were coaxially electrospun to obtain a fiber membrane; the fiber membrane was subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane to obtain a hollow lignin fiber membrane;
[0014] and / or
[0015] Preparation of hollow porous lignin fiber membrane: Polyvinylpyrrolidone and straw lignin are added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile to obtain a shell spinning solution; polyvinylpyrrolidone is added to N,N-dimethylformamide to obtain a core spinning solution; the shell spinning solution and the core spinning solution are coaxially electrospun to obtain a fiber membrane; the fiber membrane is subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane to obtain a hollow porous lignin fiber membrane.
[0016] Further, the straw includes one or more of rice straw, wheat straw, rapeseed straw or corn straw; providing straw lignin includes: collecting waste lignin black liquor from the process of extracting straw cellulose, adding deionized water to the waste lignin black liquor, collecting the precipitate by centrifugation after the straw lignin precipitates, washing it with deionized water, and then drying the washed precipitate to obtain straw lignin.
[0017] Further, the preparation of porous lignin fiber membranes includes: adding polyacrylonitrile to N,N-dimethylformamide and stirring in a water bath until completely dissolved to obtain a spinning solution; adding a certain amount of polyvinylpyrrolidone to the spinning solution and stirring in a water bath until completely dissolved, then adding straw lignin and heating and stirring in a water bath to obtain an electrospinning solution; spinning the electrospinning solution with a single needle to obtain a fiber membrane; placing the fiber membrane in a high-pressure reactor, adding deionized water to the reactor, heating in a drying oven to remove polyvinylpyrrolidone, removing the fiber membrane and washing it with deionized water, and freeze-drying to obtain a porous lignin fiber membrane.
[0018] Furthermore, the single-needle spinning conditions were as follows: room temperature, positive voltage of 20kV, negative voltage of 5kV, translation width of the spinning needle of 0cm, distance from the receiver of 16cm, spinning humidity of 60%, and injection speed of 15μL / min.
[0019] Further, the preparation of hollow lignin fiber membranes includes: adding polyacrylonitrile to N,N-dimethylformamide, stirring in a water bath until completely dissolved, adding straw lignin, heating and stirring in a water bath to obtain a shell spinning solution; adding a certain amount of polyvinylpyrrolidone to N,N-dimethylformamide, stirring and dissolving in a water bath to obtain a core spinning solution; performing coaxial electrospinning of the shell spinning solution and the core spinning solution to obtain a fiber membrane; placing the fiber membrane in a high-pressure reactor, adding deionized water to the reactor, heating in a drying oven to remove polyvinylpyrrolidone, removing the fiber membrane and washing it with deionized water, and freeze-drying to obtain a hollow lignin fiber membrane.
[0020] Further, the preparation of hollow porous lignin fiber membranes includes: adding polyacrylonitrile to N,N-dimethylformamide, stirring in a water bath until completely dissolved, adding a certain amount of polyvinylpyrrolidone, then adding straw lignin, stirring in a water bath until completely dissolved, to obtain a shell spinning solution; adding a certain amount of polyvinylpyrrolidone to N,N-dimethylformamide, stirring in a water bath to dissolve, to obtain a core spinning solution; performing coaxial electrospinning of the shell spinning solution and the core spinning solution to obtain a fiber membrane; placing the fiber membrane in a high-pressure reactor, adding deionized water to the reactor, heating in a drying oven to remove polyvinylpyrrolidone, removing the fiber membrane and washing it with deionized water until neutral, and freeze-drying to obtain a hollow porous lignin fiber membrane.
[0021] Furthermore, the coaxial electrospinning conditions were as follows: room temperature, positive voltage of 20kV, negative voltage of 5kV, translation width of the spinning needle of 0cm, distance from the receiver of 16cm, spinning humidity of 60%, and injection rates of 15 and 10μL / min for the shell and core layers, respectively.
[0022] Furthermore, the mass ratio of straw lignin to polyacrylonitrile is 2:1.
[0023] Furthermore, the mass ratio of straw lignin to polyvinylpyrrolidone is 1:(0.5-2).
[0024] Furthermore, the mass ratio of polyvinylpyrrolidone in the shell spinning solution and the core spinning solution is 1:(3-4).
[0025] The present invention also provides a modified straw lignin-based fiber membrane prepared by the above preparation method.
[0026] The present invention also provides the application of the modified straw lignin-based fiber membrane prepared above in CO2 adsorption.
[0027] The present invention has the following beneficial effects:
[0028] 1. This invention adds polyvinylpyrrolidone to the spinning solution, forms a film by electrospinning and heat treatment, and forms a porous and / or hollow structure on the surface and / or inside of the straw wood fiber film, which enhances the surface activity and adsorption performance and exhibits good CO2 adsorption performance.
[0029] 2. This invention can prepare straw lignin fiber membranes with various morphologies. By controlling the appropriate material ratio, the fibers have good microstructure and can be applied to CO2 adsorption, realizing the high-value utilization of straw resources. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.
[0031] Figure 1 SEM images of some samples prepared in the embodiments and comparative examples of the present invention;
[0032] Figure 2 TEM images of some samples prepared in the embodiments and comparative examples of the present invention;
[0033] Figure 3 The N2 adsorption-desorption isotherms and pore size distribution diagrams of the samples prepared in the embodiments and comparative examples of this invention are shown below.
[0034] Figure 4 The CO2 adsorption curves of the samples prepared in the embodiments and comparative examples of the present invention are shown at 273 K. Detailed Implementation
[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.
[0036] This invention provides modified straw lignin-based fiber membranes, their preparation methods, and their application in CO2 adsorption.
[0037] A method for preparing modified straw lignin-based fiber membranes includes the following steps:
[0038] S1, provides straw lignin;
[0039] S2. Preparation of modified lignin fiber membranes, including:
[0040] Preparation of porous lignin fiber membrane: Polyvinylpyrrolidone and straw lignin are added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile, and fiber membrane is obtained by single needle spinning. The fiber membrane is then subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane, thus obtaining a porous lignin fiber membrane.
[0041] and / or
[0042] Preparation of hollow lignin fiber membrane: Straw lignin was added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile to obtain a shell spinning solution; polyvinylpyrrolidone was added to N,N-dimethylformamide to obtain a core spinning solution; the shell spinning solution and the core spinning solution were coaxially electrospun to obtain a fiber membrane; the fiber membrane was subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane to obtain a hollow lignin fiber membrane;
[0043] and / or
[0044] Preparation of hollow porous lignin fiber membrane: Polyvinylpyrrolidone and straw lignin are added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile to obtain a shell spinning solution; polyvinylpyrrolidone is added to N,N-dimethylformamide to obtain a core spinning solution; the shell spinning solution and the core spinning solution are coaxially electrospun to obtain a fiber membrane; the fiber membrane is subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane to obtain a hollow porous lignin fiber membrane.
[0045] Specifically, the mass ratio of straw lignin to polyacrylonitrile is 2:1.
[0046] Specifically, the mass ratio of straw lignin to polyvinylpyrrolidone is 1:(0.5-2).
[0047] Specifically, the mass ratio of polyvinylpyrrolidone in the shell spinning solution and the core spinning solution is 1:(3-4).
[0048] Straw lignin can be electrospun into lignin fiber membranes, but the fibers have uniform morphology and lack defects, resulting in poor CO2 adsorption performance. This invention uses straw lignin and polyacrylonitrile (PAN) as raw materials, and adds polyvinylpyrrolidone (PVP) for modification, introducing PVP into the core layer spinning solution and / or shell layer spinning solution. Based on uniaxial electrospinning, coaxial electrospinning and hydrothermal treatment technology, porous lignin fiber membranes (PLFM), hollow lignin fiber membranes (HLFM), and hollow porous lignin fiber membranes (HPLFM) are prepared. The fiber surface forms a porous structure and / or the fibers exhibit a hollow structure, which has high surface activity and excellent CO2 adsorption performance, broadening the application prospects of straw lignin and providing ideas for realizing the high-value utilization of straw.
[0049] The present invention will be further illustrated below through specific embodiments:
[0050] In the following embodiments, rice straw (or wheat straw, rapeseed straw, corn straw, or composite straw) is selected as the straw. The extraction process of straw lignin is as follows: waste lignin black liquor from the extraction of rice straw cellulose is collected, deionized water is added to the waste lignin black liquor, and after the straw lignin precipitates, the precipitate is collected by centrifugation and washed with deionized water. The washed precipitate is then dried to obtain straw lignin.
[0051] The rice straw cellulose process is as follows: rice straw powder and an ethanol aqueous solution are added to a reaction vessel, sealed, and heated to react. Then, the mixture is filtered to obtain rice straw lignin ethanol black liquor. The ethanol concentration in the aqueous solution is 60-70 wt%, the heating temperature is 160-240℃, and the reaction time is 2-3 h. Deionized water is added to the above rice straw lignin ethanol black liquor to induce lignin to precipitate from the black liquor. The precipitate is collected by centrifugation, and the washed precipitate is dried to obtain rice straw lignin.
[0052] Example 1:
[0053] The preparation process of the modified rice straw lignin-based fiber membrane in this embodiment is as follows:
[0054] 0.3 g of polyacrylonitrile was added to 9.0 g of N,N-dimethylformamide and stirred in a water bath at 60 °C until completely dissolved. Then, 0.6 g of polyvinylpyrrolidone was added to the spinning solution, and stirring continued in a water bath until the polyvinylpyrrolidone was completely dissolved. Finally, 0.6 g of rice straw lignin was introduced into the system, and the mixture was heated and stirred in a water bath for 12 h to obtain the electrospinning solution.
[0055] Electrospinning was performed using a traditional single-needle electrospinning process on the prepared electrospinning solution. The spinning conditions were: positive voltage 20 kV, negative voltage 5 kV, needle translation width 0 cm, distance from receiver 16 cm, spinning humidity 60%, injection speed 15 μL / min, and room temperature. After spinning, the resulting nanofiber membrane was cut into several sheets, each weighing 60 mg. Each sheet was placed individually in a 50 mL polytetrafluoroethylene (PTFE) high-pressure reactor, and 40 mL of deionized water was added. The reactor was then placed in a 120 °C electric heating drying oven for 3 hours to remove polyvinylpyrrolidone (PVP). After the reaction, the reactor was cooled to room temperature, and the fiber membrane was removed and washed with deionized water until neutral. Finally, the fiber membrane was dried in a freeze dryer to obtain a porous lignin fiber membrane (PLFM), denoted as PLFM. 0.6 .
[0056] Example 2:
[0057] The steps are basically the same as in Example 1, except that 0.3g of polyvinylpyrrolidone is added, and the resulting sample is denoted as PLFM. 0.3 .
[0058] Example 3:
[0059] The steps are basically the same as in Example 1, except that 0.9g of polyvinylpyrrolidone is added, and the resulting sample is denoted as PLFM. 0.9 .
[0060] Example 4:
[0061] The steps are basically the same as in Example 1, except that 1.2g of polyvinylpyrrolidone is added, and the resulting sample is designated PLFM. 1.2 .
[0062] Example 5
[0063] The preparation process of the modified rice straw lignin-based fiber membrane in this embodiment is as follows:
[0064] Add 0.3g of polyacrylonitrile to 5.4g of N,N-dimethylformamide and stir in a water bath at 60℃ until completely dissolved. Then, introduce 0.6g of rice straw lignin into the system and heat and stir in a water bath for 12h to obtain the shell spinning solution. Add 0.3g of polyvinylpyrrolidone to 3.6g of N,N-dimethylformamide and stir in a water bath at 60℃ until completely dissolved to obtain the core spinning solution.
[0065] The prepared electrospinning solution was electrospinned using a coaxial electrospinning process. The spinning conditions were: positive voltage 20 kV, negative voltage 5 kV, spinneret translation width 0 cm, distance to receiver 16 cm, spinning humidity 60%, shell and core injection rates 15 and 10 μL / min respectively, and room temperature. After spinning, the resulting nanofiber membrane was cut into several sheets, each weighing 60 mg. Each sheet was placed individually in a 50 mL polytetrafluoroethylene (PTFE) high-pressure reactor, and 40 mL of deionized water was added. The reactor was then placed in a 120 °C electric heating drying oven for 3 h to remove polyvinylpyrrolidone. After the reaction, the reactor was cooled to room temperature, the fiber membrane was removed, washed with deionized water until neutral, and finally dried in a freeze dryer to obtain hollow lignin fiber membrane (HLFM), denoted as HLFM. 0.3 .
[0066] Example 6
[0067] The steps are basically the same as in Example 5, except that 0.6g of polyvinylpyrrolidone is added, and the resulting sample is denoted as HLFM. 0.6 .
[0068] Example 7
[0069] The steps are basically the same as in Example 5, except that 0.9g of polyvinylpyrrolidone is added, and the resulting sample is designated as HLFM. 0.9 .
[0070] Example 8
[0071] The steps are basically the same as in Example 5, except that 1.2g of polyvinylpyrrolidone is added, and the resulting sample is designated as HLFM. 1.2 .
[0072] Example 9
[0073] The preparation process of the modified rice straw lignin-based fiber membrane in this embodiment is as follows:
[0074] 0.3 g of polyacrylonitrile was added to 5.4 g of N,N-dimethylformamide and stirred in a water bath at 60 °C until completely dissolved. Then, a certain amount of polyvinylpyrrolidone was added to the spinning solution, and stirring continued in a water bath until the polyvinylpyrrolidone was completely dissolved. Finally, 0.6 g of rice straw lignin was introduced into the system, and the mixture was heated and stirred in a water bath for 12 h to obtain the shell spinning solution. A certain amount of polyvinylpyrrolidone was added to 3.6 g of N,N-dimethylformamide and stirred in a water bath at 60 °C until completely dissolved to obtain the core spinning solution.
[0075] The prepared electrospinning solution was electrospinned using a coaxial electrospinning process. The spinning conditions were as follows: positive voltage 20 kV, negative voltage 5 kV, spinneret translation width 0 cm, distance from receiver 16 cm, spinning humidity 60%, shell and core injection rates 15 and 10 μL / min, respectively, and room temperature. After spinning, the obtained nanofiber membrane was cut into several sheets, each weighing 60 mg. Each sheet was placed individually in a 50 mL polytetrafluoroethylene high-pressure reactor, and 40 mL of deionized water was added. The reactor was then placed in a 120 °C electric heating drying oven for 3 h to remove polyvinylpyrrolidone. After the reaction, the reactor was cooled to room temperature, the fiber membrane was removed, washed with deionized water until neutral, and finally dried in a freeze dryer to obtain a hollow porous lignin fiber membrane (HPLFM).
[0076] In this embodiment, the total amount of polyvinylpyrrolidone added to the shell and core layers was maintained at 0.9 g, and the mass ratio of polyvinylpyrrolidone added to the shell and core layers was 1:3. The resulting sample was designated as HPLFM. 0.9 -1 / 3.
[0077] Example 10
[0078] The steps are basically the same as in Example 9, except that the ratio of polyvinylpyrrolidone added to the shell and core layers is 1:4, and the resulting sample is denoted as HPLFM. 0.9 -1 / 4.
[0079] Example 11
[0080] The steps are basically the same as in Example 9, except that the total amount of polyvinylpyrrolidone added in the shell and core layers is 0.3g, and the resulting sample is designated as HPLFM. 0.3 .
[0081] Example 12
[0082] The steps are basically the same as in Example 9, except that the total amount of polyvinylpyrrolidone added in the shell and core layers is 0.6g, and the resulting sample is designated as HPLFM. 0.6 .
[0083] Example 13
[0084] The steps are basically the same as in Example 9, except that the total amount of polyvinylpyrrolidone added in the shell and core layers is 1.2g, and the resulting sample is designated as HPLFM. 1.2 .
[0085] Comparative Example 1:
[0086] 0.3 g of polyacrylonitrile was added to 9.0 g of N,N-dimethylformamide and stirred in a water bath at 60 °C until completely dissolved to obtain a spinning solution. 0.6 g of rice straw lignin was added to the spinning solution and heated and stirred in a water bath for 12 h to obtain an electrospinning solution. The prepared electrospinning solution was electrospinned using a traditional single-needle electrospinning process to obtain a rice straw lignin-based cellulose membrane, denoted as LFM. The spinning conditions were: room temperature, positive voltage of 20 kV, negative voltage of 5 kV, translation width of the spinning needle of 0 cm, distance from the receiver of 16 cm, spinning humidity of 60%, and injection speed of 15 μL / min.
[0087] Comparative Example 2:
[0088] The steps in this example are basically the same as in Example 9, maintaining the total amount of polyvinylpyrrolidone added to the shell and core layers at 0.9g. The difference is that the mass ratio of polyvinylpyrrolidone added to the shell and core layers is 1:1. The resulting sample is denoted as HPLFM. 0.9 -1 / 1.
[0089] Comparative Example 3:
[0090] The steps in this example are basically the same as in Example 9, maintaining the total amount of polyvinylpyrrolidone added to the shell and core layers at 0.9g. The difference is that the mass ratio of polyvinylpyrrolidone added to the shell and core layers is 1:2. The resulting sample is denoted as HPLFM. 0.9 -1 / 2.
[0091] Comparative Example 4:
[0092] The steps in this example are basically the same as in Example 9, except that the total amount of polyvinylpyrrolidone added in the shell and core layers is 1.5g, and the resulting sample is denoted as HPLFM. 1.5 .
[0093] SEM and TEM analyses were performed on some samples prepared in Examples 1-13 and Comparative Examples 1-4. The results are shown in [reference needed]. Figure 1 (where a is LFM and b is PLFM) 0.6 c is PLFM 1.2 d is HLFM 0.3 e is HLFM 1.2 f is HPLFM 0.9 -1 / 4, g is HPLFM 0.9 -1 / 1, h is HPLFM 0.3 -1 / 3, i is HPLFM 0.9 -1 / 3, j is HPLFM 1.5 -1 / 3) Figure 2 (where a is LFM, b is HLFM) 0.3 c is HLFM1.2 d is HPLFM 0.9 -1 / 4, e is HPLFM 0.9 -1 / 1, f is HPLFM 0.3 -1 / 3, g is HPLFM 0.9 -1 / 3, h is HPLFM 1.5 -1 / 3, i is PLFM 0.6 j is PLFM 1.2 ):
[0094] Detailed morphological and microstructural analysis revealed that LFM fibers exhibited uniform morphology, a smooth and flat surface, and no hollow structure. 0.6 PLFM 1.2 Pores of varying sizes can be observed on the fiber surface, with the latter exhibiting a higher pore density, indicating that the addition of PVP and subsequent treatment can create pores on the fiber surface; HLFM 0.3 HLFM 1.2 The hollow structure of the fiber indicates that adding PVP to the core spinning solution and then treating it can produce fibers with a hollow structure; HPLFM 0.9 -1 / 4, HPLFM 0.9 -1 / 3, HPLFM 0.3 -1 / 3 of the fiber surface has many tiny pores and a hollow morphology, but HPLFM 1.5 -1 / 3, HPLFM 0.9 -1 / 1 The fiber collapsed or cracked, indicating that PVP was added to both the shell spinning solution and the core spinning solution. After processing, a fiber membrane with a porous surface and a hollow structure can be obtained. However, it is necessary to control the total amount of PVP added and the proportion of PVP added in the shell and core layers to ensure the integrity of the fiber structure.
[0095] BET analysis was performed on the samples prepared in Examples 1-13 and Comparative Examples 1-4. The results are shown in the figure. Figure 3 and Table 1:
[0096] Table 1. Specific surface area and pore structure parameters of LFM, PLFM, HLFM and HPLFM
[0097]
[0098] All adsorption-desorption curves belong to type IV adsorption-desorption isotherms with an H3 hysteresis loop, but the hysteresis loop is not obvious in some curves. The pore size distribution diagram shows that the pore sizes of all samples are concentrated between 2-50 nm, exhibiting typical mesoporous structures. Table 1 shows that the surface properties of LFM are not particularly outstanding; although the average pore size is 6.378 nm, the specific surface area and pore volume are only 4.081 m². 2 / g and 0.018cm3 / g. After the introduction of PVP, the specific surface area, average pore size, and pore volume of various fibers all increased significantly. Furthermore, with increasing PVP dosage, the specific surface area, average pore size, and pore volume of PLFM, HLFM, and HPLFM all showed an increasing trend, with HPLFM showing the most significant increase. 1.5 With a specific surface area of -1 / 3, an average pore size, and a pore volume of 16.257 m³, this figure is remarkable. 2 / g, 16.048nm and 0.065cm 3 / g, which is almost three times that of LFM. However, if the PVP ratio of the shell to the core is greater than 1:3, the specific surface area and other parameters of HPLFM tend to decrease. This is because when there are too many pores in the shell, it will cause the fiber structure to break and collapse.
[0099] The CO2 adsorption capacity of all prepared LFM, PLFM, HLFM, and HPLFM was tested using a volumetric analyzer (JWBK100, JWGB) at a pressure range of 273 K and 0-101 kPa. The results are shown in the figure. Figure 4 and Table 2:
[0100] Table 2. Maximum CO2 adsorption capacity of LFM, PLFM, HLFM and HPLFM at 273 K and 101 kPa
[0101]
[0102] PLFM exhibits superior CO2 adsorption performance compared to LFM, and the higher the amount of PVP used, the better the CO2 adsorption performance of PLFM. 1.2 The maximum CO2 adsorption capacity of LFM can reach 0.414 mmol / g, which is 3.3 times that of LFM, indicating that the CO2 adsorption of LFM can be optimized by introducing PVP to prepare porous fibers.
[0103] HLFM's CO2 adsorption performance is also comprehensively superior to LFM. 1.2 The maximum CO2 adsorption capacity can reach 0.371 mmol / g. It is worth noting that when the PVP dosage is the same, the CO2 adsorption performance of PLFM is better than that of HLFM. This is because the pores of HLFM are all inside the fiber, and the fiber diameter of LFM is slightly smaller, making it difficult to accommodate too much N2 or CO2 at the same time. In contrast, the pores of PLFM are mostly distributed on the fiber surface, which facilitates contact with the external environment. Furthermore, during the removal of PVP, the PVP components of HLFM are concentrated inside the fiber, making them more difficult to remove than those of PLFM.
[0104] With a fixed PVP dosage, the CO2 adsorption performance of HPLFM initially increases and then decreases with increasing PVP content in the shell layer. This is because increasing the PVP content in the shell layer reduces the internal pores of the HPLFM fibers while increasing the pores on the fiber surface, thus increasing the surface properties and adsorption capacity of HPLFM. However, when there is too much PVP in the shell layer, the pores on the fiber surface may connect with the internal pores, causing the fibers to crack and collapse, thereby destroying the basic morphology of the hollow porous fibers and reducing their surface activity and adsorption performance. This indicates that under a suitable PVP-core-shell ratio (1:3–4), the surface properties and adsorption capacity of HPLFM increase with increasing PVP content, where HPLFM… 1.2 The maximum CO2 adsorption capacity of HPLFM can reach 0.577 mmol / g with a PVP dosage of -1 / 3. Under the same PVP dosage, this is 1.4 and 1.5 times the highest capacity of PLFM and HLFM, respectively. HPLFM has the morphology of both PLFM and HLFM and has the highest surface activity. When the PVP dosage reaches 1.5g, the maximum CO2 adsorption capacity of HPLFM decreases because a small part of the fiber structure breaks and collapses. Therefore, it is necessary to control the amount of PVP added. The fiber morphology and performance are better when the mass ratio of PVP to rice straw lignin is (0.5~2):1.
[0105] This invention enhances surface activity and adsorption performance by adding polyvinylpyrrolidone to the spinning solution, followed by electrospinning and heat treatment to form a porous and / or hollow structure on the surface and / or inside of the straw wood fiber membrane, thus exhibiting good CO2 adsorption performance.
[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a modified straw lignin-based fiber membrane, characterized in that, Includes the following steps: S1, provides straw lignin; S2. Preparation of modified lignin fiber membranes, including: Preparation of porous lignin fiber membrane: Polyvinylpyrrolidone and straw lignin are added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile, and fiber membrane is obtained by single needle spinning. The fiber membrane is then subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane, thus obtaining a porous lignin fiber membrane. and / or Preparation of hollow lignin fiber membrane: Straw lignin was added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile to obtain a shell spinning solution; polyvinylpyrrolidone was added to N,N-dimethylformamide to obtain a core spinning solution; the shell spinning solution and the core spinning solution were coaxially electrospun to obtain a fiber membrane; the fiber membrane was subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane to obtain a hollow lignin fiber membrane; and / or Preparation of hollow porous lignin fiber membrane: Polyvinylpyrrolidone and straw lignin are added to the spinning solution of N,N-dimethylformamide and polyacrylonitrile to obtain a shell spinning solution; polyvinylpyrrolidone is added to N,N-dimethylformamide to obtain a core spinning solution; the shell spinning solution and the core spinning solution are coaxially electrospun to obtain a fiber membrane; the fiber membrane is subjected to hydrothermal treatment to remove polyvinylpyrrolidone from the fiber membrane to obtain a hollow porous lignin fiber membrane.
2. The method for preparing the modified straw lignin-based fiber membrane as described in claim 1, characterized in that: The straw includes one or more of rice straw, wheat straw, rapeseed straw, or corn straw; providing straw lignin includes: collecting waste lignin black liquor from the process of extracting straw cellulose, adding deionized water to the waste lignin black liquor, collecting the precipitate by centrifugation after the straw lignin precipitates, washing it with deionized water, and then drying the washed precipitate to obtain straw lignin.
3. The method for preparing the modified straw lignin-based fiber membrane as described in claim 1, characterized in that: The preparation of porous lignin fiber membranes includes: adding polyacrylonitrile to N,N-dimethylformamide and stirring in a water bath until completely dissolved to obtain a spinning solution; adding a certain amount of polyvinylpyrrolidone to the spinning solution and stirring in a water bath until completely dissolved, then adding straw lignin and heating and stirring in a water bath to obtain an electrospinning solution; spinning the electrospinning solution with a single needle to obtain a fiber membrane; placing the fiber membrane in a high-pressure reactor, adding deionized water to the reactor, heating in a drying oven to remove polyvinylpyrrolidone, removing the fiber membrane and washing it with deionized water, and freeze-drying to obtain a porous lignin fiber membrane.
4. The method for preparing the modified straw lignin-based fiber membrane as described in claim 1, characterized in that: The preparation of hollow lignin fiber membranes includes: adding polyacrylonitrile to N,N-dimethylformamide, stirring in a water bath until completely dissolved, adding straw lignin, heating and stirring in a water bath to obtain a shell spinning solution; adding a certain amount of polyvinylpyrrolidone to N,N-dimethylformamide, stirring and dissolving in a water bath to obtain a core spinning solution; performing coaxial electrospinning of the shell spinning solution and the core spinning solution to obtain a fiber membrane; placing the fiber membrane in a high-pressure reactor, adding deionized water to the reactor, heating in a drying oven to remove polyvinylpyrrolidone, removing the fiber membrane and washing it with deionized water, and freeze-drying to obtain a hollow lignin fiber membrane.
5. The method for preparing the modified straw lignin-based fiber membrane as described in claim 1, characterized in that: The preparation of hollow porous lignin fiber membranes includes: adding polyacrylonitrile to N,N-dimethylformamide, stirring in a water bath until completely dissolved, adding a certain amount of polyvinylpyrrolidone, then adding straw lignin, stirring in a water bath until completely dissolved to obtain a shell spinning solution; adding a certain amount of polyvinylpyrrolidone to N,N-dimethylformamide, stirring in a water bath to dissolve to obtain a core spinning solution; performing coaxial electrospinning of the shell spinning solution and the core spinning solution to obtain a fiber membrane; placing the fiber membrane in a high-pressure reactor, adding deionized water to the reactor, heating in a drying oven to remove polyvinylpyrrolidone, removing the fiber membrane and washing it with deionized water until neutral, and freeze-drying to obtain a hollow porous lignin fiber membrane.
6. The method for preparing the modified straw lignin-based fiber membrane as described in claim 1, 3, 4, or 5, characterized in that: The mass ratio of straw lignin to polyacrylonitrile is 2:
1.
7. The method for preparing the modified straw lignin-based fiber membrane as described in claim 1, 3, 4, or 5, characterized in that: The mass ratio of straw lignin to polyvinylpyrrolidone is 1:(0.5-2).
8. The method for preparing the modified straw lignin-based fiber membrane as described in claim 5, characterized in that: The mass ratio of polyvinylpyrrolidone in the shell spinning solution and the core spinning solution is 1:(3-4).
9. The modified straw lignin-based fiber membrane prepared by any one of the preparation methods described in claims 1 to 8.
10. The application of the modified straw lignin-based fiber membrane according to claim 9 in CO2 adsorption.