Preparation and application of viscose-based activated carbon composite material

Abstract

The application discloses a viscose-based activated carbon composite material and a preparation and application thereof. 4+ The preparation method of the viscose-based activated carbon composite material comprises the following steps: adding a compound containing Ti into hyperbranched bismaleimide resin to uniformly mix to obtain a first dip-coating liquid; immersing a substrate containing viscose fibers into the first dip-coating liquid to soak, taking out and drying to obtain a first substrate; immersing the first substrate into a metal organic framework precursor solution, washing and drying after heating reaction to obtain a second substrate; carbonizing the second substrate, carrying out pore expansion treatment, and then performing acid washing and drying to obtain the viscose-based activated carbon composite material. The method is simple and reliable, the MOFs are assembled on the viscose fibers before carbonization, the problem that the MOFs are decomposed at high carbonization temperature is successfully overcome, the problem that the pore structure of the activated carbon is damaged due to acidification treatment when the viscose-based activated carbon fibers are loaded with the MOFs is avoided, and the composite material has good adsorption and degradation performance.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of an activated carbon material, in particular to a preparation and application of a viscose-based activated carbon composite material. BACKGROUND

[0002] Metal organic framework (MOFs) is a material with highly ordered porous structure, including UIO-66, ZIF-8, MIL-100 (Fe) and many other types. MOFs has excellent catalytic degradation effect on dichlorodiethyl sulfide and other substances, but pure MOFs has the problems of easy agglomeration of particles and limited mass transfer, so the adsorption capacity is small, which leads to the catalytic degradation performance of MOFs cannot be fully exerted.

[0003] Activated carbon is an adsorbent material with high specific surface area and rich pore structure, and has high adsorption capacity, but does not have catalytic degradation effect on adsorbed substances. The prior art prepares a composite material by loading MOFs on activated carbon, so that the composite material has high adsorption capacity and good catalytic degradation effect at the same time, and the adsorption removal effect of the composite material on target substances is greatly improved. For example, a preparation method of an activated carbon fiber-metal organic framework composite material is disclosed in Chinese patent CN106807329A, which uses activated carbon fiber as raw material, covers metal precursors on the surface of the activated carbon fiber by using a homogeneous precipitation method, and then forms a metal organic framework structure on the surface of the activated carbon fiber by coordinating and complexing the metal precursors with organic ligands under water or solvent thermal conditions, so as to realize the compounding of the activated carbon fiber and the metal organic framework material.

[0004] Since there are not enough active groups on the surface of the activated carbon for in-situ growth and combination of MOFs, the activated carbon needs to be acidized before in-situ loading of MOFs. Although acidizing can generate active groups on the surface of the activated carbon, it will inevitably damage the original pore structure of the activated carbon, leading to a decrease in the adsorption performance of the composite material. In addition, the damage to the pore structure of the activated carbon further leads to uneven distribution of the active groups generated by acidizing, and then leads to uneven in-situ growth of MOFs in the damaged pore area, which may cause local agglomeration and stacking of MOFs, block the pores, and inhibit the exertion of the degradation performance of MOFs, so that the adsorption and degradation performance of the composite material is not ideal.

[0005] Since MOFs are not resistant to high temperature and will decompose at a temperature above 500 DEG C, and the carbonization temperature during preparation of activated carbon is usually above 600 DEG C, if MOFs are pre-assembled and loaded on the activated carbon precursor, the MOFs will be largely decomposed during high-temperature carbonization, and a MOF activated carbon composite material with good adsorption and degradation performance cannot be obtained. There is no report on preparation of a MOF activated carbon composite material by carbonizing an activated carbon precursor (such as viscose fiber, cotton fiber and the like) loaded with MOFs.

[0006] Rayon fiber is a regenerated cellulose fiber with shorter molecular chains and looser arrangement, and lower crystallinity. This amorphous structure is more likely to form a cross-linked network during carbonization, thus enhancing the continuity of carbon skeleton. Meanwhile, rayon fiber is chemically treated (e.g. alkalization) during manufacturing process, and residual metal ions (e.g. sodium) can act as catalysts during activation stage, promoting the uniform generation of pores. The low crystallinity of rayon fiber allows more uniform erosion of activating agents (e.g. water vapor or CO2), forming a hierarchical pore structure. The grooved structure (diameter about 0.1-1 μm) on the surface of rayon fiber is converted into abundant surface defects during activation, further increasing the specific surface area. The activated carbon prepared from rayon fiber can have a specific surface area of more than 2000 m 2 / g. During carbonization of rayon fiber, metal impurities (content about 0.3%) such as sodium catalyze the formation of graphite crystallites at 800℃, with a crystallite size of about 2-3 nm, forming a three-dimensional network structure through sp 3 hybrid carbon bonds, with a compressive strength of up to 50 MPa. In contrast, the natural cellulose in cotton fiber has a higher crystallinity (about 70%), and the fiber structure is tightly ordered. During carbonization, the molecular chains are easily broken, forming discontinuous carbon structures. The microcrystalline orientation in the carbonized product is high (arranged along the fiber axis), but the interlayer bonding is weak, with a transverse strength of only 60-70% of that of rayon-based activated carbon. The high crystallinity also limits the penetration of activating agents, restricting the development of pores and leading to uneven pore distribution. The natural wax layer of cotton fiber may block the pores when carbonization is incomplete. The specific surface area of activated carbon prepared from cotton fiber is usually less than 1500 m 2 / g. Although the performance of rayon fiber as an activated carbon precursor is significantly better than other fibers, the assembly efficiency of Ti 4+ doped high-temperature-resistant UIO-66 on rayon fiber is low, making it difficult to utilize the pre-loaded Ti 4+ doped UIO-66 to prepare MOF activated carbon composites from rayon fiber. SUMMARY

[0007] The purpose of the present application is to provide a preparation method of rayon-based activated carbon composite, solving the problem of how to prepare rayon-based activated carbon composite. Another purpose of the present application is to provide an application of rayon-based activated carbon composite in adsorbing and degrading dichlorodiethyl sulfide or benzene or iodine, solving the problem of low adsorption and degradation rate of existing MOF activated carbon composite.

[0008] TECHNICAL SOLUTION The preparation method of the rayon-based activated carbon composite provided by the present application comprises the following steps:

[0009] (1) adding a compound containing Ti 4+ to hyperbranched bismaleimide resin to obtain a first dip coating liquid;

[0010] (2) the substrate containing viscose fibers is soaked in the first dip-coating liquid, taken out and dried to obtain a first substrate;

[0011] (3) the first substrate is immersed in a metal organic framework precursor solution, heated and reacted, washed and dried to obtain a second substrate;

[0012] (4) the second substrate is carbonized, subjected to a pore expansion treatment, and then subjected to acid washing and drying to obtain a viscose-based activated carbon composite material.

[0013] The present application completes the diffusion process of Ti 4+ The present application selects Ti 4+ compound and the metal organic framework precursor solution are separated before carbonization, and the Ti 4+ compound is doped after the MOF is assembled, which not only improves the heat resistance of the MOF, but also effectively avoids the problem of low assembly efficiency of the MOF on the viscose fibers caused by directly adding the Ti 4+ compound in the metal organic framework precursor solution. 4+ The hyperbranched bismaleimide resin as the pre-disposed carrier of the Ti 4+ compound can assist in improving the doping efficiency of the Ti 4+ compound and promoting the layer-by-layer self-assembly of the UIO-66, thereby providing necessary conditions for the doping of the Ti 4+ compound on the UIO-66.

[0014] Preferably, in step (1), the Ti 4+ containing compound includes at least one of titanium dioxide, titanium tetrachloride, titanium tetrabromide, titanyl sulfate, titanium sulfate, titanium nitrate, titanium phosphate, tetramethoxy titanium, tetraethoxy titanium, and tetrabutoxy titanium; and the hyperbranched bismaleimide resin includes at least one of tris(aminophenyl)ethane hyperbranched bismaleimide resin, tris(aminophenyl)methane hyperbranched bismaleimide resin, and 1,3,5-tris(aminophenyl)benzene hyperbranched bismaleimide resin.

[0015] Preferably, in step (1), the mass ratio of the Ti 4+ containing compound to the hyperbranched bismaleimide resin is 1-5:5-100; and in step (2), the substrate containing viscose fibers includes at least one of viscose fiber felt, viscose fiber fabric, viscose fiber non-woven fabric, and viscose fiber bundle.

[0016] Preferably, in step (2), the coating amount of the first dip-coating liquid on the substrate containing viscose fibers is 0.1-10wt% of the weight of the substrate containing viscose fibers, and the drying method is to hang and dry the substrate containing viscose fibers at 30-60℃ after taking it out from the first dip-coating liquid.

[0017] Preferably, in step (3), the metal organic framework precursor solution is prepared by adding a zirconium salt and terephthalic acid into an organic solvent, and then adding an acid, and mixing to obtain the metal organic framework precursor solution.

[0018] Further, the zirconium salt comprises at least one of zirconium chloride, zirconium sulfate, zirconium nitrate, and zirconium oxychloride, the organic solvent comprises at least one of N,N-dimethylformamide, N-methyl-2-pyrrolidone, and diglyme, the acid comprises at least one of hydrochloric acid, formic acid, and acetic acid, the final concentration of the zirconium salt in the metal organic framework precursor solution is 20-30 mM, the final concentration of the terephthalic acid is 20-30 mM, and the final concentration of the acid is 0.1-3.0 M.

[0019] Preferably, in step (3), the heating reaction is performed at 80-150℃ for 4-6h, and the method for washing and drying the first substrate after the reaction is as follows: the first substrate is taken out, washed with an organic solvent and an alcohol solvent, and then taken out for vacuum drying to obtain a second substrate.

[0020] Further, in step (3), the organic solvent comprises at least one of methanol, isopropanol, and N,N-dimethylformamide, and the alcohol solvent comprises at least one of methanol, ethanol, isopropanol, and ethylene glycol.

[0021] Preferably, in step (4), the method for carbonizing the second substrate is as follows: the second substrate is heated at 200-300℃ for 1-2h in air or an inert atmosphere, and then carbonized at 600-900℃ for 1-3h in an inert atmosphere; the method for the pore expansion treatment is as follows: water vapor is introduced into the carbonized product of the second substrate at 800-900℃ for 1-2h; and the method for the acid washing is as follows: the product after the pore expansion treatment is immersed in an aqueous hydrochloric acid solution with a concentration of 0.1-1M for 1-10min, and then taken out and washed with water until neutral.

[0022] The second aspect of the present application discloses the application of the viscose-based activated carbon composite material prepared by the above preparation method in adsorbing and degrading dichlorodiethyl sulfide, benzene, or iodine.

[0023] The viscose-based activated carbon composite material prepared by the application can effectively catalyze the degradation of various organic or inorganic substances through the UIO-66 loaded on the surface of the viscose-based activated carbon, and meanwhile, the concentration of the adsorbed substances on the surface and inside of the composite material is improved through the adsorption enrichment effect of the activated carbon fiber, so that the catalytic degradation efficiency of the UIO-66 on the adsorbed substances is further improved, and the degradation of the adsorbed substances can make the adsorption capacity of the activated carbon fiber be fully utilized, so that the adsorption capacity is not limited, and the purpose substances can be continuously adsorbed from the surrounding environment. The degradation effect of the UIO-66 cooperates with the strong adsorption effect of the activated carbon fiber, so that the comprehensive adsorption and degradation performance of the composite material is synergistically improved.

[0024] Beneficial effects: Compared with the prior art, the application has the following remarkable advantages:

[0025] The method of the application is simple and reliable, and the MOFs are assembled on the viscose fiber before carbonization, and the problem of decomposition of the MOFs at high carbonization temperature is successfully overcome, the problem that the acidification treatment destroys the pore structure of the activated carbon when the MOFs are loaded on the viscose-based activated carbon fiber is avoided, so that the composite material has good adsorption and degradation performance.

[0026] The viscose-based activated carbon composite material prepared by the application has good adsorption and degradation effect on mustard gas, benzene, iodine and the like, and the adsorption removal rate of these substances is significantly higher than that of ordinary activated carbon fiber or pure UIO-66. The adsorption value of iodine of the composite material is more than 1100mg / g within a short time, the static benzene adsorption removal rate is more than 70%, the adsorption removal rate of dichlorodiethyl sulfide is more than 98%, and the composite material has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The scanning electron microscope image of the viscose-based activated carbon composite material prepared in Example 1;

[0028] Figure 2 The scanning electron microscope image of the untreated viscose fiber;

[0029] Figure 3 The scanning electron microscope image of the fiber surface of the activated carbon composite material prepared in Comparative Example 2;

[0030] Figure 4 The scanning electron microscope image of the fiber surface of the activated carbon composite material prepared in Comparative Example 3;

[0031] Figure 5 The scanning electron microscope image of the fiber surface of the activated carbon composite material prepared in Comparative Example 4;

[0032] Figure 6 The scanning electron microscope image of the fiber surface of the activated carbon composite material prepared in Comparative Example 5;

[0033] Figure 7 A scanning electron microscope image of the fiber surface of the activated carbon composite material prepared for Comparative Example 6;

[0034] Figure 8 A scanning electron microscope image of the fiber surface of the activated carbon composite material prepared for Comparative Example 7;

[0035] Figure 9 A scanning electron microscope image of the viscose-based activated carbon composite material prepared for Example 2;

[0036] Figure 10 A scanning electron microscope image of the viscose-based activated carbon composite material prepared for Example 3. DETAILED DESCRIPTION

[0037] The technical solutions of the present application are further described below in combination with the accompanying drawings.

[0038] Example 1: A method for preparing a viscose-based activated carbon composite material is as follows:

[0039] (1) Tetramethoxy titanium was added to the tris(aminophenyl)methane hyperbranched bismaleimide resin (purchased from Xianyang Sanjing Technology Co., Ltd.) in a mass ratio of 3:50 to mix uniformly to obtain a first dip coating liquid;

[0040] (2) The viscose fiber felt completely made of viscose fibers was immersed in the first dip coating liquid at room temperature for 30 min, and was ultrasonically treated (40 kHz, 100 W, 5 s) every 5 min, and then the viscose fiber felt was taken out and squeezed to remove the excess first dip coating liquid until the coating amount of the first dip coating liquid was 5 wt% of the weight of the viscose fiber felt, and was hung for drying at 45°C to obtain a first substrate;

[0041] (3) At room temperature, zirconium chloride hexahydrate was stirred and dissolved in N,N-dimethylformamide (DMF) to obtain a final concentration of 25 mM of zirconium chloride, and then phthalic acid was added to obtain a final concentration of 25 mM, and then hydrochloric acid was added to obtain a final concentration of 1.5 M, and the mixture was stirred for 1 h to obtain a metal organic framework precursor solution.

[0042] (4) The first substrate was immersed in the metal organic framework precursor solution, heated to 100°C for 6 h, and then the first substrate was taken out, washed with DMF for 3 times, and then washed with methanol for 1 time, and then the first substrate was taken out, and vacuum dried at 150°C for 6 h to obtain a second substrate.

[0043] (5) The second substrate was heated at 250°C for 1.5 h in an argon atmosphere, and then the second substrate was carbonized at 800°C for 2 h in an argon atmosphere to obtain a carbonization product;

[0044] (6) At 850℃, only water vapor was introduced into the carbonized product of the second substrate for 1.5h to expand the pores, the water vapor flux was 0.75g / (g·char·h), and the water vapor flow rate was 50 mL / s. Then, at room temperature, the product after pore expansion was placed in a 0.5M hydrochloric acid aqueous solution for 5min, then taken out and washed with water until neutral, and dried to obtain a viscose-based activated carbon composite material, as shown in Figure 1 .

[0045] Example 2: A viscose-based activated carbon composite material was prepared by the following method:

[0046] (1) Titanium tetrachloride was added to tris(aminophenyl)ethane hyperbranched bismaleimide resin (purchased from Xianyang Sanjing Technology Co., Ltd.) at a mass ratio of 1:5 to obtain a first dipping solution;

[0047] (2) At room temperature, the modal knitted fabric was immersed in the first dipping solution for 30min, and was slightly shaken or ultrasonically treated (40 kHz, 100 W, 5s) every 5min. Then, the modal knitted fabric was taken out and the excess first dipping solution was scraped off until the coating amount of the first dipping solution was 2wt% of the weight of the modal knitted fabric. The modal knitted fabric was hung and dried at 30℃ to obtain a first substrate;

[0048] (3) At room temperature, zirconium oxychloride was dissolved in N,N-dimethylformamide (DMF) to obtain a final concentration of 20mM of zirconium oxychloride, then benzenedicarboxylic acid was added to obtain a final concentration of 20mM, and the mixture was stirred for 1h. Then, hydrochloric acid was added to obtain a final concentration of 3M, and the mixture was stirred and mixed to obtain a metal organic framework precursor solution.

[0049] (4) The first substrate was immersed in the metal organic framework precursor solution, heated to 80℃ and reacted for 6h, then taken out, washed with DMF for 3 times and then washed with ethanol for 1 time, and then taken out and dried at 140℃ under vacuum for 8h to obtain a second substrate.

[0050] (5) The second substrate was heated at 200℃ for 2h under an argon atmosphere, and then carbonized at 600℃ for 3h under an argon atmosphere to obtain a carbonized product;

[0051] (6) At 800℃, only water vapor was introduced into the carbonized product of the second substrate for 2h to expand the pores, the water vapor flux was 0.5g / (g·char·h), and the water vapor flow rate was 30 mL / s. Then, at room temperature, the product after pore expansion was placed in a 0.1M hydrochloric acid aqueous solution for 10min, then taken out and washed with water until neutral, and dried to obtain a viscose-based activated carbon composite material, as shown in Figure 9 .

[0052] Example 3: A viscose-based activated carbon composite material was prepared by the following method:

[0053] (1) The titanium nitrate was added into the 1,3,5-tris(aminophenyl)benzene hyperbranched bismaleimide resin (purchased from Xianyang Sanjing Technology Co., Ltd.) at a mass ratio of 1:20 to obtain a first dipping solution;

[0054] (2) The viscose fiber non-woven fabric made entirely of viscose fiber was immersed in the first dipping solution at room temperature for 60 min, with slight shaking or ultrasonic treatment (40 kHz, 100 W, 10 s) every 10 min, and then the viscose fiber non-woven fabric was taken out and hung to drain the excess first dipping solution until the coating amount of the first dipping solution was 10 wt% of the weight of the viscose fiber non-woven fabric, and then it was dried at 60°C to obtain a first substrate;

[0055] (3) The zirconium nitrate was dissolved in N,N-dimethylformamide (DMF) at room temperature by stirring to obtain a final concentration of 30 mM, then benzenedicarboxylic acid was added to obtain a final concentration of 30 mM, and then the stirring was continued for 1 h, and then acetic acid was added to obtain a final concentration of 1 M, and then the mixture was mixed to obtain a metal-organic framework precursor solution;

[0056] (4) The first substrate was immersed in the metal-organic framework precursor solution, heated to 150°C and reacted for 4 h, then the first substrate was taken out, washed with DMF for 3 times and then washed with isopropanol for 1 time, and then the first substrate was taken out and vacuum dried at 150°C for 6 h to obtain a second substrate.

[0057] (5) The second substrate was heated at 300°C for 1 h in an argon atmosphere, and then the second substrate was carbonized at 900°C for 1 h in an argon atmosphere to obtain a carbonized product;

[0058] (6) At 900°C, water vapor was introduced into the carbonized product of the second substrate for 1 h to expand the pores, with a water vapor flux of 0.75 g / (g·char·h) and a water vapor flow rate of 50 mL / s. Then, the product after pore expansion was immersed in a 1 M hydrochloric acid aqueous solution and stirred for 1 min at room temperature, and then the water was washed to neutral, and then dried to obtain a viscose-based activated carbon composite material, as shown in Figure 10 .

[0059] Example 4: A method for preparing a viscose-based activated carbon composite material is as follows:

[0060] (1) The titanium tetrabutoxide was added into the 1,3,5-tris(aminophenyl)benzene hyperbranched bismaleimide resin (purchased from Xianyang Sanjing Technology Co., Ltd.) at a mass ratio of 2:70 to obtain a first dipping solution;

[0061] (2) The pure viscose fiber bundle is immersed in the first dip-coating liquid at room temperature for 45 min, and is slightly oscillated or ultrasonically treated (40 kHz, 100 W, 5 s) every 5 min, then the viscose fiber bundle is taken out and squeezed to remove the excess first dip-coating liquid until the coating amount of the first dip-coating liquid is 10 wt% of the weight of the viscose fiber bundle, and the first substrate is obtained by hanging drying at 50°C;

[0062] (3) Zirconium sulfate is stirred and dissolved in N, N-dimethylformamide (DMF) at room temperature to obtain a final concentration of 20 mM zirconium sulfate, then phthalic acid is added to obtain a final concentration of 25 mM, and the stirring is continued for 1 h, then acetic acid is added to obtain a final concentration of 0.5 M, and the mixture is uniformly mixed to obtain a metal-organic framework precursor solution.

[0063] (4) The first substrate is immersed in the metal-organic framework precursor solution, heated to 120°C for 4 h, then taken out, washed with DMF for 3 times and then washed with ethylene glycol for 1 time, then taken out, and vacuum dried at 150°C for 6 h to obtain a second substrate.

[0064] (5) The second substrate is heated at 300°C for 1.5 h in an argon atmosphere, and then carbonized at 850°C for 2.5 h in an argon atmosphere to obtain a carbonized product;

[0065] (6) The carbonized product of the second substrate is only subjected to steam hole expansion at 800°C for 1.5 h, with a steam flux of 0.5 g / (g·char·h) and a steam flow rate of 30 mL / s, and then the expanded product is placed in a 0.8 M hydrochloric acid aqueous solution at room temperature for 6 min, then taken out and washed with water to neutral, and dried to obtain a viscose-based activated carbon composite material.

[0066] Comparative Example 1: The rest is the same as Example 1, except that:

[0067] The viscose fiber felt is replaced by a cotton fiber felt.

[0068] Comparative Example 2: A viscose-based activated carbon composite material is prepared by the following method:

[0069] (1) The viscose fiber felt in Example 1 is heated at 250°C for 1.5 h in an argon atmosphere, and then carbonized at 800°C for 2 h in an argon atmosphere to obtain a carbonized product;

[0070] (2) The carbonized product of the viscose fiber felt is only subjected to steam hole expansion at 850°C for 1.5 h, with a steam flux of 0.75 g / (g·char·h) and a steam flow rate of 50 mL / s, and then the expanded product is placed in a 0.5 M hydrochloric acid aqueous solution at room temperature for 5 min, then taken out and washed with water to neutral, and dried to obtain an activated carbon fiber felt.

[0071] (3) Zirconium chloride hexahydrate was stirred and dissolved in N,N-dimethylformamide (DMF) at room temperature to obtain a solution with a final concentration of 25 mM of zirconium chloride, then phthalic acid was added to obtain a solution with a final concentration of 25 mM, and then stirred for 1 h, and then hydrochloric acid was added to obtain a solution with a final concentration of 1.5 M, and then stirred to obtain a metal organic framework precursor solution.

[0072] (4) The activated carbon fiber felt was immersed in the metal organic framework precursor solution at room temperature, heated to 100°C and reacted for 6 h, then taken out, washed with DMF for 3 times, washed with methanol for 1 time, and then taken out and vacuum dried at 150°C for 6 h to obtain the viscose-based activated carbon composite material.

[0073] Comparative Example 3: The same as Comparative Example 2, except that:

[0074] The activated carbon fiber felt obtained in step (2) was immersed in a 6 M hydrochloric acid aqueous solution for 24 h, then taken out and washed with distilled water until neutral to obtain a pretreated activated carbon fiber felt.

[0075] The pretreated activated carbon fiber felt was then subjected to step (4) to obtain the viscose-based activated carbon composite material.

[0076] Comparative Example 4: The viscose-based activated carbon composite material was prepared as follows:

[0077] (1) Zirconium chloride hexahydrate was stirred and dissolved in N,N-dimethylformamide (DMF) at room temperature to obtain a solution with a final concentration of 25 mM of zirconium chloride, then phthalic acid was added to obtain a solution with a final concentration of 25 mM, and then stirred for 1 h, and then hydrochloric acid was added to obtain a solution with a final concentration of 1.5 M, and then stirred to obtain a metal organic framework precursor solution.

[0078] (2) A viscose fiber felt made entirely of viscose fiber was immersed in the metal organic framework precursor solution at room temperature, heated to 100°C and reacted for 6 h, then the viscose fiber felt was taken out, washed with DMF for 3 times, washed with methanol for 1 time, and then the viscose fiber felt was taken out and vacuum dried at 150°C for 6 h to obtain a carbonization substrate; the fiber surface micrograph of the carbonization substrate is shown in FIG. 1, which shows that there is little UIO-66 assembled in situ on the surface of the viscose fiber, indicating that the precursor solution containing titanium tetramethoxide cannot successfully assemble UIO-66 on the surface of the viscose fiber. Figure 3 (3) The carbonization substrate was heated at 250°C for 1.5 h in an argon atmosphere, and then the carbonization substrate was carbonized at 800°C for 2 h in an argon atmosphere to obtain a carbonization product;

[0079]

[0080] ​(4) At 850℃, only water vapor was introduced into the carbonized product for 1.5h to expand the pores, the water vapor flux was 0.75g / (g·char·h), and the water vapor flow rate was 50 mL / s. Then, at room temperature, the product after pore expansion was placed in a 0.5M hydrochloric acid aqueous solution and soaked for 5min, then taken out and washed to neutral, and dried to obtain a viscose-based activated carbon composite material.

[0081] Comparative Example 5: The rest is the same as Example 1, except that:

[0082] Only hyperbranched bismaleimide resin was used as the first dip-coating liquid, and 0.5M tetramethoxy titanium was added to the metal organic framework precursor solution.

[0083] Comparative Example 6: The rest is the same as Example 1, except that:

[0084] No tetramethoxy titanium was added in step (1), and only hyperbranched bismaleimide resin was used as the first dip-coating liquid.

[0085] Comparative Example 7: The rest is the same as Example 1, except that:

[0086] In step (5), no pre-heating before carbonization was performed, and the second substrate was directly carbonized at 800℃ for 2h to obtain a carbonized product.

[0087] The properties of the activated carbon composite materials prepared in Examples 1-4 and Comparative Examples 1-7 were tested, and the methods were as follows:

[0088] 1. The compressive strength and specific surface area of the activated carbon composite material were measured respectively;

[0089] 2. The iodine adsorption value of the activated carbon composite material at 1h was measured by the method in “Wood Activated Carbon Test Method Iodine Adsorption Value Determination (GB / T 12496.8-1999)”; the static benzene adsorption removal rate was determined according to the national standard GB / T 12496.12-1999;

[0090] The degradation removal rate of dichlorodiethyl sulfide was determined by LY / T 1616-2022 “Wood Activated Carbon Test Method”. Specifically, a standard curve of mustard gas simulant 2-chloroethyl ethyl sulfide (CEES) solution was drawn by referring to Frank's method, the absorbance value at the maximum absorption wavelength of 445nm was measured by ultraviolet spectrophotometer, and the absorbance value was plotted against the concentration C of the standard solution and linear fitting was performed. The standard curve equation was obtained by fitting, and the concentration was calculated according to the standard curve, and the removal rate was calculated by substituting the formula. The formula is as follows: η=(C0-C A ) / C0×100%; C0 is the initial mass concentration of the CEES solution, μg / mL; C AResidual mass concentration of CEES solution, pg / mL.

[0091] The preparation method of the CEES standard solution for drawing the standard curve is as follows:

[0092] The CEES was dissolved in DMSO according to the set concentration gradient (0.1, 0.5, 2, 8, 32, 128, 512 pg / mL) to obtain CEES standard solutions with different concentrations for measuring the absorbance value. Pure DMSO was also set as a blank control.

[0093] The DMSO solution of CEES was prepared according to the final concentration of 30 pg / mL as the initial CEES solution; the activated carbon composite material was completely immersed in the initial CEES solution according to 250 mg / L, and after standing for 24 h, the activated carbon composite material was taken out, the absorbance value of the remaining CEES solution was measured, and the C A .

[0094] The test results are as follows:

[0095] Table 1 Performance test results of different activated carbon composite materials

[0096]

[0097] In the results of Table 1, after viscose fibers are replaced by cotton fibers in Comparative Example 1, the compressive strength and specific surface area of the composite material are both greatly reduced compared with Example 1, mainly due to the fact that the porosity and mechanical properties of carbonized cotton fibers are obviously inferior to those of viscose fibers. During carbonization of cotton fibers, discontinuous carbon structures are easily formed due to molecular chain rupture, resulting in a decrease in mechanical strength. High crystallinity also leads to difficulty in penetration of the activator, and the development of porosity is limited. Viscose fibers are more likely to form a crosslinked network during carbonization, thereby enhancing the continuity of the carbon skeleton. Viscose fibers are more likely to be activated to generate uniform activated carbon porosity, thereby improving the overall specific surface area of the composite material. In Comparative Example 2, the viscose fiber felt is first carbonized, and then UIO-66 is assembled and loaded. Since the surface of the activated carbon after carbonization of viscose fibers lacks active groups for in-situ growth and combination of UIO-66, the surface of the viscose-based activated carbon cannot successfully load UIO-66, resulting in that the performance of the composite material in Comparative Example 2 is close to that of the activated carbon fiber felt, and the adsorption and degradation performance of the activated carbon fiber felt is not improved. In Comparative Example 3, the activated carbon fiber felt is subjected to acid treatment. Although theoretically, the acid treatment can increase the active groups on the activated carbon fiber felt and improve the assembly and loading amount of UIO-66 on the activated carbon fiber felt, in fact, the acid treatment leads to the destruction of the pore structure in the activated carbon fiber, and affects the ordered and uniform assembly of the pore structure of UIO-66. Local stacking blocks the activated carbon pores, significantly reducing the specific surface area of the composite material, and resulting in that the comprehensive performance of the composite material is significantly reduced compared with Example 2 and the activated carbon fiber felt control group. In Comparative Example 4, tetramethoxy titanium is added to the metal-organic framework precursor solution instead of the first dip-coating solution, and there is no assistance of hyperbranched bismaleimide resin. The addition of Ti 4+ greatly reduces the assembly efficiency of UIO-66 on the surface of viscose fibers, and thus the adsorption and degradation performance of the carbonized composite material is also greatly lower than that of Example 1. Similarly, in Comparative Example 5, even though the hyperbranched bismaleimide resin is added to assist the assembly of UIO-66, the hyperbranched bismaleimide resin cannot reverse the assembly obstacle of UIO-66 caused by the addition of Ti 4+ , so that the performance of the composite material is similar to that of the simple viscose-based activated carbon fiber. In Comparative Example 6, UIO-66 is not Ti-doped. Although UIO-66 can be assembled and grown in-situ on the surface of viscose fibers, since UIO-66 is mineralized and decomposed into ZrO2 at a temperature higher than 500°C, a large amount of ZrO2 is generated on the surface of the viscose-based activated carbon fiber during high-temperature carbonization, blocking the pores, resulting in a great reduction in the specific surface area of the composite material, and further leading to poor adsorption and degradation performance of the composite material. In Comparative Example 7, direct high-temperature carbonization is performed, resulting in that Ti 4+ in the hyperbranched bismaleimide resin fails to fully diffuse into the assembled UIO-66, leading to mineralization and decomposition of UIO-66, and also greatly reducing the specific surface area and adsorption and degradation performance of the composite material.

[0098] 3. Determining the UIO-66 generation on the surface of different activated carbon composites.

[0099] From Figure 1 , Figure 9 and Figure 10 It can be seen that in the composite material prepared by the present application, the surface of the viscose-based porous activated carbon fiber is uniformly assembled with UIO-66 particles with a large specific surface area, and the UIO-66 particles are arranged in order without the phenomenon of accumulation and blockage of the pores of the activated carbon fiber. Such a micro-surface structure not only can further increase the specific surface area of the activated carbon fiber and improve the adsorption capacity, but also can greatly improve the catalytic degradation performance of the composite material, thereby comprehensively improving the adsorption and degradation performance of the composite material.

[0100] From Figure 3 It can be seen that in the activated carbon composite material in Comparative Example 2, the fiber surface only has the porous structure of ordinary activated carbon fiber and a small amount of UIO-66 particles, and UIO-66 is not successfully loaded.

[0101] From Figure 4 It can be seen that in the activated carbon composite material prepared in Comparative Example 3, the pore structure in the activated carbon fiber collapses, a large number of large pits appear, and a large number of disordered stacked UIO-66 particles appear on the surface of the activated carbon fiber.

[0102] From Figure 5 It can be seen that in the activated carbon composite material prepared in Comparative Example 4, the fiber surface only has the porous structure of ordinary activated carbon fiber and a small amount of impurity particles, and UIO-66 is not successfully loaded.

[0103] From Figure 6 It can be seen that in the activated carbon composite material prepared in Comparative Example 5, since the viscose fiber surface fails to effectively assemble UIO-66, after carbonization, the fiber surface morphology of the activated carbon composite material is similar to the porous structure of ordinary activated carbon fiber, and only a small amount of UIO-66 particles or impurity particles are loaded.

[0104] From Figure 7 It can be seen that in Comparative Example 6, due to the mineralization of UIO-66 in the carbonization process, a large amount of ZrO2 blocks the pores, and the surface of the activated carbon fiber has no clear porous structure.

[0105] From Figure 8 It can be seen that in Comparative Example 7, the surface of the activated carbon composite material prepared also has the phenomenon of ZrO2 blocking the pores.

Claims

1. A method for producing a viscose-based activated carbon composite material, characterized by, The method comprises the following steps: (1) adding a compound containing Ti 4+ to a hyperbranched bismaleimide resin to mix uniformly to obtain a first dip-coating liquid; (2) soaking the substrate containing viscose fibers in the first dip-coating liquid, taking out and drying to obtain a first substrate; (3) soaking the first substrate in a metal organic framework precursor solution, washing and drying after heating reaction to obtain a second substrate; (4) carbonizing the second substrate, performing pore expansion treatment, and then performing acid washing and drying to obtain a viscose-based activated carbon composite material.

2. The method for preparing the viscose-based activated carbon composite material according to claim 1, characterized in that, In step (1), the compound containing Ti 4+ includes at least one of titanium tetrachloride, titanium tetrabromide, titanyl sulfate, titanium sulfate, titanium nitrate, titanium phosphate, tetramethoxy titanium, tetraethoxy titanium, tetrabutoxy titanium; the hyperbranched bismaleimide resin includes at least one of tris(aminophenyl)ethane hyperbranched bismaleimide resin, tris(aminophenyl)methane hyperbranched bismaleimide resin, 1,3,5-tris(aminophenyl)benzene hyperbranched bismaleimide resin.

3. The method for preparing the viscose-based activated carbon composite material according to claim 1, characterized in that, In step (1) containing Ti 4+ The mass ratio of the compound to the hyperbranched bismaleimide resin is 1-5:5-100; in step (2), the substrate containing viscose fiber includes at least one of viscose fiber felt, viscose fiber fabric, viscose fiber nonwoven fabric, and viscose fiber bundle.

4. The method for preparing the viscose-based activated carbon composite material according to claim 1, characterized in that, In step (2), the coating amount of the first dip-coating liquid on the substrate containing viscose fibers is 0.1-10wt% of the weight of the substrate containing viscose fibers, and the drying method is: taking out the substrate containing viscose fibers from the first dip-coating liquid and hanging drying at 30-60℃.

5. The method for preparing the viscose-based activated carbon composite material according to claim 1, characterized in that, In step (3), the metal organic framework precursor solution is prepared by the following method: adding a zirconium salt and terephthalic acid into an organic solvent, then adding an acid and mixing to obtain the metal organic framework precursor solution.

6. The method for preparing the viscose-based activated carbon composite material according to claim 5, characterized in that, The zirconium salt includes at least one of zirconium chloride, zirconium sulfate, zirconium nitrate and zirconium oxychloride, the organic solvent includes at least one of N,N-dimethylformamide, N-methyl-2-pyrrolidone and diglyme, the acid includes at least one of hydrochloric acid, formic acid and acetic acid, the final concentration of the zirconium salt in the metal organic framework precursor solution is 20-30 mM, the final concentration of terephthalic acid is 20-30 mM, and the final concentration of the acid is 0.1-3.0 M.

7. The method for preparing the viscose-based activated carbon composite material according to claim 1, characterized in that, In step (3), the heating reaction is performed at 80-150℃ for 4-6h, and the washing and drying method is: taking out the first substrate after reaction, washing with an organic solvent and an alcohol solvent, then taking out the first substrate and vacuum drying to obtain the second substrate.

8. The method for preparing the viscose-based activated carbon composite material according to claim 7, characterized in that, The organic solvent includes at least one of methanol, isopropanol and N,N-dimethylformamide, and the alcohol solvent includes at least one of methanol, ethanol, isopropanol and ethylene glycol.

9. The method for preparing the viscose-based activated carbon composite material according to claim 1, characterized in that, In step (4), the carbonization method of the second substrate is: heating the second substrate at 200-300℃ for 1-2h in air or inert atmosphere, and then carbonizing the second substrate at 600-900℃ for 1-3h in inert atmosphere; the pore expansion treatment method is: introducing water vapor into the carbonized product of the second substrate at 800-900℃ for 1-2h; and the acid washing method is: soaking the product after pore expansion in a 0.1-1M hydrochloric acid aqueous solution for 1-10min, and then taking out and washing to neutral.

10. Application of the viscose-based activated carbon composite material prepared by the method of any one of claims 1-9 in adsorbing and degrading dichlorodiethyl sulfide, benzene or iodine.

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