Catalytic membrane capable of repeatedly self-growing active layer as well as preparation method and application of catalytic membrane

Abstract

The invention discloses a catalytic membrane capable of repeatedly self-growing an active layer. A flaky solid of a layered double hydroxide micro / nano active layer is self-grown in situ on a geopolymer inorganic membrane; the invention also discloses a preparation method and application of the catalytic membrane. According to the catalytic membrane, the layered double hydroxide active layer with the micro / nano structure is subjected to in-situ hydro-thermal synthesis, the multifunctional catalytic membrane with the repeatable self-growing active layer is obtained, the repeatable and self-growing active layer can be achieved for multiple times, and micro / nano particles are not prone to falling off from a carrier in the using process.

Description

TECHNICAL FIELD

[0001] The present application relates to a catalytic membrane and its preparation method and application, in particular to a catalytic membrane with self-grown active layer and its preparation method and application. BACKGROUND

[0002] Layered double hydroxide (LDH) is a general term for hydrotalcite (HT) and hydrotalcite-like compounds (HTLCs), which is a two-dimensional layered compound mainly composed of metal oxides and interlayer anions. It has the advantages of wide source, stable chemical properties, low synthesis cost, non-toxicity, etc., and is widely used in adsorption, catalysis and pharmacology fields. However, single LDHs have the disadvantages of less functional groups, poor acid and alkali resistance, low reusability, easy aggregation, and difficult recovery, which makes it difficult to further promote its practical application. Therefore, how to in-situ grow the powder state layered double metal hydroxide on the carrier to obtain a fixed shape sheet (or spherical) material has become one of the key points for its repeated and large-scale practical application.

[0003] Silicate-aluminate geopolymer inorganic material is rich in aluminum and silicon elements, and has similar inorganic properties to layered double hydroxide, which is a good base material for loading / growing layered double hydroxide micro / nano active layer. It can provide strong binding force and growth source for the self-grown micro / nano active layer, which can promote the self-growth of the micro / nano active layer on one hand, and prevent the micro / nano particles from falling off from the carrier during use on the other hand. Geopolymer is a green, non-toxic, amorphous or quasi-crystalline inorganic polymer material with three-dimensional network molecular sieve structure, which is made of natural minerals, solid waste or industrial by-products. It has the advantages of wide raw material source, easy preparation, low energy consumption, high mechanical properties, excellent high temperature resistance, and good application in water treatment, porous materials, building insulation materials, fireproof and anticorrosive materials, biomedical materials, hybrid materials, and solid sealing of toxic and harmful substances.

[0004] Lignin is the second most abundant organic material after cellulose, and about 500 million tons of lignin by-products are separated from plants by the pulp and paper industry every year. However, so far, more than 95% of the lignin is still directly discharged into rivers or burned after being concentrated, and is rarely effectively utilized. In addition, as the main component of lignocellulose, the energy density of lignin is much higher than that of cellulose and hemicellulose. Lignin liquefied oil is more compatible with crude oil and has more potential as a substitute for petroleum fuel. However, the high oxygen content, complex structure and poor thermal stability of lignin limit its direct utilization and result in low conversion and utilization rate. How to improve the conversion and utilization rate and produce high value-added chemicals is a continuous concern of many researchers. SUMMARY

[0005] The present application is directed to the above technical problems, and provides a catalytic membrane with a self-grown active layer and a preparation method thereof. The in-situ hydrothermal growth method is used to grow a precursor metal mixed solution on a geopolymer inorganic membrane, by taking advantage of the rich aluminum content, excellent mechanical properties and thermal stability of the geopolymer inorganic membrane. The present application can not only solve the problem of non-recovery of layered double hydroxide powder, but also obtain a functional catalytic membrane that can degrade lignin and organic wastewater.

[0006] To achieve the above-mentioned object, the technical scheme provided by the present application is as follows:

[0007] A catalytic membrane with a self-grown active layer is a sheet-shaped solid with a self-grown layered double hydroxide micro / nano active layer on a geopolymer inorganic membrane. The base film can be thin or thick, thin and sheet-shaped, thick and cylindrical (actually also sheet-shaped, just thicker).

[0008] The preparation method of the catalytic membrane with a self-grown active layer as described above comprises the following operation steps:

[0009] (1) preparing a porous geopolymer inorganic membrane;

[0010] (2) preparing a double-metal precursor solution;

[0011] (3) adding the double-metal precursor solution obtained in step (2) into a stainless steel high-pressure reaction kettle, then adding the porous geopolymer inorganic membrane obtained in step (1) for soaking, and then heating at 60-180℃ for 12-96h for hydrothermal synthesis reaction. After the reaction, a layered double hydroxide is grown in-situ on the porous geopolymer membrane. The obtained material after the reaction is dried at 30-120℃ to obtain a catalytic membrane with a self-grown layered double hydroxide active layer, i.e. a catalytic membrane with a self-grown active layer. The porous geopolymer inorganic membrane used can be a base film with a thickness of 0.5-15mm according to actual needs.

[0012] Further, the preparation of the porous geopolymer inorganic membrane in step (1) is to take the active substance containing silicate and aluminate, add alkali activator and deionized water, mechanically stir and mix uniformly to obtain a mixed slurry, add foaming agent H2O2 and surfactant sodium dodecyl sulfate (K12) to the mixed slurry, mechanically stir and mix uniformly, pour into a mold, cure, polish, and the porous geopolymer inorganic membrane is obtained; wherein the mold used for pouring is a cylinder with variable size. The obtained porous geopolymer inorganic membrane has a silica-alumina ratio of 0.5-8.0, a specific surface area of 20-200 m 2 / g, and a pore size of 1 nm-1 mm. The active substance containing silicate and aluminate is any two of metakaolin, slag, fly ash or red mud mixed uniformly; when the active substance containing silicate and aluminate is metakaolin and slag, or metakaolin and fly ash, or fly ash and slag, or metakaolin and red mud, the addition amount is 0.5-2.0 in molar ratio of Na2O / Al2O3 and 1.0-5.0 in molar ratio of SiO2 / Al2O3; the alkali activator and deionized water are added in a mass ratio of 10-2:1; the alkali activator is one of NaOH, KOH, modified sodium water glass with a modulus of 1.0-2.4 or modified potassium water glass; the stirring speed of the mechanical stirring is 500-3000 r / min, and the stirring time is 0.5-5 min; the addition amount of the foaming agent H2O2 and the surfactant sodium dodecyl sulfate (K12) is 0.1-2.0% and 0.01-2.0% of the mass of the mixed slurry, respectively; the curing temperature is 30-120℃, and the curing time is 12-96 h.

[0013] Further, the preparation of the double-metal precursor solution in step (2) is to prepare a divalent metal cation salt and a trivalent metal cation salt respectively, i.e. a precursor solution; the ion ratio of the divalent metal cation to the trivalent metal cation is 10:1-1:10.

[0014] Further, the divalent metal cation is one of Co 2+ , Ca 2+ , Mg 2+ , Zn 2+ , Mn 2+ , Ni 2+ , and the anion is one of Cl - , NO3 - , SO4 2- , with a concentration of 0.001-0.5 mol / L; the trivalent metal cation is one of Al 3+ , Fe 3+ , Cr 3+ , and the anion is one of Cl - , NO3 - , SO4 2- .

[0015] Further, the drying in step (3) is 60℃ drying for 12h; the 120℃ heating in step (3) is for hydrothermal synthesis reaction for 24h.

[0016] The catalytic film with self-grown active layer as described above can be used as a catalyst for the application in depolymerization of lignin and degradation of organic wastewater. After use, the surface active layer of the growth surface is polished with sandpaper, and the in-situ self-growth steps of steps (2)-(3) are repeated to obtain the catalytic film with self-grown active layer.

[0017] The catalytic film with self-grown active layer as described above can be used as a catalyst for the application in degradation of organic wastewater, and the operation is as follows: the catalytic film with self-grown active layer is added to the organic wastewater, and then shaken.

[0018] Further, 0.02-0.8g of the catalytic film with self-grown active layer is added to every 50mL of the organic wastewater; and the shaking is at 30-60℃ for 12h in a shaking table.

[0019] Further, the organic wastewater is at least one of an antibiotic, a herbicide or a dye; the herbicide is 2,4-dichlorophenoxyacetic acid, the antibiotic is tetracycline hydrochloride, and the dye is one of crystal violet, methylene blue, congo red or rhodamine B.

[0020] The catalytic film with self-grown active layer as described above can be used as a catalyst for the application in depolymerization of lignin, and the operation steps are as follows:

[0021] (i) the catalytic film with self-grown active layer, lignin and a reaction solvent are added to a polytetrafluoroethylene reaction kettle, mixed uniformly, the air in the reaction kettle is replaced with nitrogen, and the reaction kettle is sealed;

[0022] (ii) the sealed reaction kettle in step (i) is placed in an electric heating constant temperature drying oven for heating reaction, after the reaction is completed, the sealed reaction kettle is taken out from the electric heating constant temperature drying oven when it is cooled to room temperature, and the mixture obtained after the reaction in the reaction kettle is subjected to solid-liquid separation, and the liquid product is taken, wherein the liquid product contains small molecular compounds such as phenolic compounds, and the liquid product obtained in step (ii) is subjected to qualitative and quantitative analysis to obtain the yield of phenolic compounds. The qualitative analysis is performed by using a gas chromatograph-mass spectrometer, and the quantitative analysis is performed by using an external standard method or an internal standard method; the yield of the liquid product is in the range of 10%-90% (the mass ratio of the liquid product to the initial lignin), and the yield of the phenolic compounds is in the range of 10-300mg / g (the mass ratio of the initial lignin).

[0023] Further, the catalytic membrane in step (i) is added in an amount of 0.01-5 g as required; the lignin in step (i) is one of alkali lignin, lignin sulfonate and organic solvent lignin; the lignin is added in an amount of 0.01-5 g; the reaction solvent in step (i) is added in an amount of 20%-40% of the volume of the polytetrafluoroethylene reaction kettle; the reaction solvent in step (i) is an organic solvent and / or pure water; wherein the organic solvent is methanol, ethanol, isopropyl alcohol, n-hexane or acetone; when the reaction solvent is an organic solvent and pure water, the two are mixed in a volume ratio of 1:1-5:1.

[0024] Further, the heating reaction temperature in step (ii) is 200-280℃, and the reaction time is 0.5-12 h; the solid-liquid separation in step (ii) has two methods, when an organic solvent is used as the depolymerization reaction solvent, the reaction mixture is filtered through an organic filter membrane with a pore size of 0.22 μm to perform solid-liquid separation, and the obtained solution is the liquid product containing phenolic compounds; when pure water or a mixed solvent of an organic solvent and pure water is used as the reaction solvent, the reaction mixture is extracted with ethyl acetate, and the obtained ethyl acetate phase after extraction is the liquid product obtained by depolymerization, which is also the liquid product containing phenolic compounds.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) The catalytic membrane of the present application is in-situ hydrothermally synthesized with a micro / nano-structured layered double hydroxide active layer, and a multifunctional catalytic membrane with a repeatable self-grown active layer is obtained, which can realize multiple "repeatable" and "self-grown" active layers, and the micro / nano particles are not easy to fall off from the carrier during use;

[0027] (2) The method for preparing the catalytic membrane of the present application can effectively utilize natural minerals, solid waste or industrial by-products as raw materials, and can be used in biomass resource conversion and lignin depolymerization and organic wastewater treatment, and has the advantages of environmental friendliness and repeatable manufacturing; compared with the traditional method for preparing layered double hydroxide, the present application can reduce the use of growth source metals, and has strong substrate bonding force to fix the powdered layered double hydroxide;

[0028] (3) The method of the present application can effectively convert lignin waste generated in the pulping and papermaking process into high-value-added phenolic compounds; at the same time, the obtained catalyst can efficiently degrade organic pollutants such as tetracycline, and the degradation rate is more than 90%. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A is a digital photo of the CoAl source catalytic membrane prepared by the present application, Figure 1 B is a scanning electron microscope photo.

[0030] Figure 2 The pore size distribution of the CoAl source catalytic membrane prepared by the application under two metal ratios.

[0031] Figure 3 The yield distribution of phenolic compounds obtained by using the CoAl source catalytic membrane prepared by the application as a catalyst to depolymerize alkali lignin. DETAILED DESCRIPTION

[0032] The application will be described in detail below with reference to specific embodiments, but it should be understood that the scope of protection of the application is not limited by the specific embodiments. The raw materials and reagents used in the examples are commercially available unless otherwise specified. The alcohol and other drugs used in the examples are all of analytical purity. The alkali lignin was purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd. The elemental analysis is shown in Table 1: The C, H, N, and S contents of the alkali lignin were determined by an elemental analyzer, and the O content was obtained by difference.

[0033] Table 1 Industrial analysis and elemental analysis of alkali lignin

[0034]

[0035] The water glass is an industrial-grade water glass produced and sold by Nanning Chunxu Chemical Industry Co., Ltd. The modulus SiO2 / Na2O is 3.3. The modified water glass used in the examples is a modified sodium water glass obtained by adding sodium hydroxide to the industrial-grade water glass to adjust the corresponding modulus.

[0036] Example 1

[0037] A preparation method of a catalytic membrane with a repeatable self-grown active layer, the operation steps are as follows:

[0038] (1) Preparation of porous geopolymer inorganic membrane: according to the molar ratio Na2O / Al2O3 = 1, SiO2 / Al2O3 = 3.5, take the metakaolin and slag, mix uniformly to obtain a mixed powder, according to the mass ratio of alkali activator: deionized water = 8:1, take the modified sodium water glass with a modulus of 1.0 and deionized water and add them to the mixed powder, keep the mechanical stirring speed at 1000 r / min for 1 min, mix uniformly, obtain a mixed slurry, according to the amount of 0.7% of the mixed slurry and 0.04% of the mixed slurry, add the foaming agent H2O2 and the surfactant K12 to the mixed slurry, keep the mechanical stirring speed at 2000 r / min for 2 min, mix uniformly, cast into a cylindrical plastic mold (R = 20 mm) for film injection, 60℃ curing for 12 h, the surface is polished to 7 mm thick, and the porous geopolymer inorganic membrane is obtained; the specific surface area of the obtained porous geopolymer inorganic membrane is 20-200 m 2 / g, and the pore size is 1 nm-1 mm.

[0039] (2) Preparation of bimetallic precursor solution: according to the ion ratio of divalent metal cation to trivalent metal cation = 3:1, 10.47 mg of cobalt nitrate hexahydrate and 4.5 mg of aluminum nitrate nonahydrate were weighed and respectively prepared into Co ion solution (cobalt ion concentration of 0.036 mol / L) and Al ion solution with deionized water, namely the precursor solution;

[0040] (3) 100 mL of the Co ion solution and the Al ion solution in step (2) were taken and added into a stainless steel high-pressure reaction kettle with a capacity of 500 mL, then the porous geopolymer inorganic membrane obtained in step (1) was added for soaking, and then the stainless steel high-pressure reaction kettle was heated to 110°C for hydrothermal synthesis reaction for 24 h, after the reaction, the layered double hydroxide was grown in situ on the porous geopolymer membrane, and the obtained material after the reaction was dried at 60°C for 12 h, to obtain a catalytic membrane with self-grown active layer of layered double hydroxide (CoAl source catalytic membrane 1), namely the catalytic membrane with self-grown active layer, and the catalytic membrane was a flaky solid. The digital photo of the prepared CoAl source catalytic membrane is shown in Figure 1 Figure 1 In B, it can be observed that the obtained catalytic membrane has a micro / nano-structured active layer of layered double hydroxide, the surface is composed of flaky nanosheets to form micro / nano-flowers, and an overlapped surface is formed.

[0041] The CoAl source catalytic membrane 1 prepared above was used to depolymerize lignin:

[0042] (i) The CoAl source catalytic membrane 1 prepared in step (3) above was cut into a cuboid block with a length of 12 mm, a width of 6 mm, a height of 1 mm, and a mass of 0.1 g, 0.2 g of alkali lignin, and 16 mL of reaction solvent methanol were added into a polytetrafluoroethylene reaction kettle with a volume of 50 mL, the air was replaced with nitrogen, and the reaction kettle was sealed;

[0043] (ii) The sealed reaction kettle in step (i) was placed in an electric heating constant temperature drying oven and heated to 280°C for 2 h, after the reaction was completed, the sealed reaction kettle was taken out from the electric heating constant temperature drying oven, and the mixture obtained after the reaction in the reaction kettle was subjected to solid-liquid separation, namely solid-liquid separation was performed through a 0.22 μm polytetrafluoroethylene filter, to obtain a solid residue and a methanol-based liquid product, and the obtained methanol-based liquid product was a liquid product containing small molecular compounds such as phenolic compounds.

[0044] ​The methanol-based liquid product obtained in step (ii) is subjected to qualitative analysis by gas chromatography-mass spectrometry, and the product distribution table is shown in Table 2. The higher yield monophenol compounds are selected for quantitative analysis by external standard method. The standard curves of ten phenolic compounds, including guaiacol, 4-ethylguaiacol, 4-methylguaiacol, 4-methoxyphenol, isoeugenol, 3-methylguaiacol, 4-methylguaiacol, 2,6-dimethoxyphenol, 2,6-dimethoxy-4-methylphenol, and 2,4-di-tert-butylphenol, are drawn. The methanol-based liquid product is tested by gas chromatography to determine the yield of each monophenol and the total phenol yield. The phenol yield is 53.67 mg / g.

[0045] Table 2 Product identification distribution table of CoAl source catalytic membrane 1 catalytic alcoholysis of alkali lignin

[0046]

[0047]

[0048]

[0049]

[0050] Example 2

[0051] A method for preparing a catalytic membrane with a self-grown active layer, the operation steps are as follows:

[0052] (1) Prepare a porous geopolymer inorganic membrane: polish the surface to 5 mm thick, and the rest of the operation is the same as step (1) of Example 1;

[0053] (2) Prepare a bimetallic precursor solution: ……use deionized water to prepare a Co ion solution (cobalt ion concentration is 0.018 mol / L) and an Al ion solution, which is the precursor solution, and the rest is the same as step (2) of Example 1;

[0054] (3) ……heat the stainless steel high-pressure reaction kettle to 120°C for hydrothermal synthesis reaction for 24h, and the rest is the same as step (3) of Example 1, to obtain CoAl source catalytic membrane 2, which is a sheet-shaped solid catalytic membrane.

[0055] Degradation of lignin using the CoAl source catalytic membrane 2 prepared above:

[0056] (i) Cut the CoAl source catalytic membrane 2 prepared in step (3) above into a cuboid block with a length of 12 mm, a width of 6 mm, and a height of 1 mm. The reaction solvent is deionized water, and the rest is the same as step (4) of Example 1.

[0057] (ii) The sealed reactor from step (i) is placed in an electrically heated constant temperature drying oven and heated to 280°C for 6 hours. After the reaction is completed, the sealed reactor is removed from the electrically heated constant temperature drying oven and the solid-liquid separation of the mixture obtained after the reaction is carried out: the mixture obtained after the reaction is acidified with a 37% hydrochloric acid solution to obtain a pH of about 1.5. Subsequently, 30 mL of ethyl acetate is added to the mixture obtained after the reaction to separate the mixture and stirred for 10 minutes to completely extract the liquid part from the solid residue. Then, centrifugation is carried out at a speed of 9000 r / min for 10 minutes and filtered with a polytetrafluoroethylene (PTFE) membrane. The ethyl acetate part containing the crude oil is recovered from the aqueous phase using a separatory funnel, which is the liquid product obtained after depolymerization.

[0058] The methanol-based liquid product obtained in step (ii) is subjected to qualitative analysis by gas chromatography-mass spectrometry, and the product distribution table is shown in Table 3. The ethyl acetate-soluble product is extracted using a rotary evaporator, and the standard curve is drawn for ten phenolic compounds, including guaiacol, 4-ethylguaiacol, 4-methylguaiacol, 4-methoxyphenol, isoeugenol, 3-methylguaiacol, 4-methylguaiacol, 2,6-dimethoxyphenol, 2,6-dimethoxy-4-methylphenol, and 2,4-di-tert-butylphenol. The sample to be tested is tested by gas chromatography, and quantitative analysis can be performed to obtain a guaiacol yield of 44.28 mg / g (calculated based on the proportion of alkali lignin raw material), 3.35 mg / g of dimethoxy-3-methylguaiacol, and other phenolic compounds (as shown in Table 3). Figure 3

[0059] Table 3 Product identification and distribution table of CoAl source catalytic membrane 2 catalytic hydrolysis of alkali lignin

[0060]

[0061]

[0062]

[0063] Example 3

[0064] A method for preparing a catalytic membrane with a self-grown active layer, the operation steps are as follows:

[0065] ​(1) Preparation of porous geopolymer inorganic membrane: …… keep the rotation speed at 2000 r / min mechanical stirring for 2 min, mix evenly, get mixed slurry, according to the amount of foaming agent is 0.6% of the mass of mixed slurry, the amount of surfactant is 0.03% of the mass of mixed slurry, add foaming agent H2O2 and surfactant K12 to the mixed slurry, keep the rotation speed at 2000 r / min mechanical stirring for 2 min, mix evenly, cast into a circular plastic mold (R = 20 mm) for film injection, 60℃ curing for 12h, the surface is polished to 1mm thick, the rest is the same as step (1) of example 1;

[0066] (2) Preparation of bimetallic precursor solution: the concentration of cobalt ions is 0.024 mol / L, the rest is the same as step (2) of example 1;

[0067] (3) The same as step (3) of example 1, the catalytic membrane is a sheet-shaped solid.

[0068] Tetracyclines are a broad-spectrum antibiotic produced by actinomycetes, widely used in the pharmaceutical industry, animal husbandry and aquaculture. The production and use of tetracyclines currently ranks second in the world among antibiotics, however, during use, only part of the tetracyclines are absorbed by the animal body and metabolized, the rest of the antibiotics are still in active form (parent or metabolite) and discharged outside the body, causing great harm to the ecosystem and human health.

[0069] The above prepared catalytic membrane was used to remove simulated tetracycline hydrochloride wastewater: 0.02 g of the above prepared CoAl source catalytic membrane was weighed and added to 50 mL of tetracycline hydrochloride solution (pH 5.0, 50 mg / L) in a shaking bed at 60℃ for 12h, and the removal effect could reach 91.16%.

[0070] The above prepared catalytic membrane was used to degrade simulated tetracycline hydrochloride wastewater: 0.8 g of the above prepared CoAl source catalytic membrane was weighed and added to 50 mL of tetracycline hydrochloride solution (pH 5.0, 50 mg / L) in a shaking bed at 60℃ for 12h, and the degradation effect could reach 98.99%; after the reaction, the catalytic membrane was recovered and cleaned, and sandpaper was used to polish it, and steps (2)-(3) of the "preparation method of catalytic membrane with repeatable self-grown active layer" were repeated, and the self-growth of the active layer was carried out again to obtain a new catalytic membrane, and the above degradation experiment was repeated, and the degradation effect of the new catalytic membrane on tetracycline hydrochloride could still reach 98.78%.

[0071] The catalytic membrane prepared above was used to remove simulated crystal violet wastewater: 0.02 g of the CoAl source catalytic membrane prepared above was added to 50 mL of crystal violet solution (pH 7.0, 50 mg / L) in a shaker and shaken at 30°C for 12 h, and the removal efficiency reached 99.39%.

[0072] Example 4

[0073] A method for preparing a catalytic membrane with a self-grown active layer, the operation steps being as follows:

[0074] (1) The same as step (1) of Example 3;

[0075] (2) Preparation of a bimetallic precursor solution: the copper ion concentration was 0.036 mol / L, and copper nitrate trihydrate and aluminum nitrate nonahydrate were weighed and mixed to prepare a precursor solution, and the rest was the same as step (2) of Example 3;

[0076] (3) 100 mL of Cu ion solution and 100 mL of Al ion solution in step (2) were added to a stainless steel high-pressure reactor with a capacity of 500 mL, and the porous geopolymer inorganic membrane obtained in step (1) (the porous geopolymer inorganic membrane used can be selected according to actual needs, with a substrate film thickness of 0.5-15 mm) was added for soaking, and then the stainless steel high-pressure reactor was heated to 100°C for hydrothermal synthesis reaction for 24 h, and the rest was the same as step (4) of Example 3, to obtain a catalytic membrane with a self-grown layered double hydroxide active layer (CuAl source catalytic membrane), and the catalytic membrane was a sheet-shaped solid.

[0077] 2,4-dichlorophenoxyacetic acid (2,4-D) is a very important herbicide and has been widely used for weed control in agriculture and forestry. It has certain toxic side effects on organisms and can remain in environmental media such as soil and water. Therefore, 2,4-D present in water bodies needs to be removed.

[0078] The catalytic membrane prepared above was used to remove simulated 2,4-D wastewater: 0.04 g of the CuAl source catalytic membrane prepared above was added to 50 mL of 2,4-D solution (pH 7.0, 50 mg / L) in a shaker and shaken at 30°C for 12 h, and the removal efficiency reached 95.08%.

[0079] The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A catalytic membrane with a reproducible self-growing active layer, characterized in that: A sheet-like solid with a layered double hydroxide micro / nano active layer that grows in situ on a geopolymer inorganic membrane.

2. The method for preparing a catalytic membrane with a reproducible self-growing active layer as described in claim 1, characterized in that, The operation includes the following steps: (1) Preparation of porous geopolymer inorganic membranes; (2) Prepare bimetallic precursor solution; (3) Add the bimetallic precursor solution obtained in step (2) into the reaction vessel, then add the porous geopolymer inorganic membrane obtained in step (1), soak it, and then heat it at 60-180℃ for hydrothermal synthesis reaction for 12-96h. Dry the material obtained after the reaction at 30-120℃ to obtain a catalytic membrane with a repeatable self-growing active layer.

3. The method for preparing a catalytic membrane with a reproducible self-growing active layer as described in claim 2, characterized in that: The preparation of porous geopolymer inorganic membrane in step (1) involves taking an active material containing aluminosilicate, adding an alkali activator and water, stirring and mixing to obtain a mixed slurry, adding a foaming agent (H2O2) and a surfactant (sodium dodecyl sulfate) to the mixed slurry, stirring and mixing, casting, curing, and polishing to obtain a porous geopolymer inorganic membrane; the active material containing aluminosilicate is obtained by mixing any two of metakaolin, slag, fly ash, or red mud; when the active material containing aluminosilicate is a combination of metakaolin and slag, or metakaolin and fly ash, or fly ash and slag, or metakaolin and red mud, the amount added is based on the molar ratio Na2O / Al2O3. =0.5~2.0, SiO2 / Al2O3=1.0~5.0; the alkali activator and water are added at a mass ratio of 10-2:1; the alkali activator is one of NaOH, KOH, modified sodium silicate or modified potassium silicate with a modulus of 1.0~2.4; the mechanical stirring speed is 500~3000r / min, and the time is 0.5~5min; the foaming agent H2O2 and the surfactant sodium dodecyl sulfate are added at 0.1~2.0% and 0.01~2.0% of the mass of the mixed slurry, respectively; the curing temperature is 30~120℃, and the curing time is 12~96h.

4. The method for preparing a catalytic membrane with a reproducible self-growing active layer as described in claim 2, characterized in that: The preparation of the bimetallic precursor solution in step (2) involves preparing divalent metal cation salts and trivalent metal cation salts, which are the precursor solutions; the ion ratio of divalent metal cations to trivalent metal cations is 10:1 to 1:10; the drying in step (3) is drying at 60℃ for 12h; the hydrothermal synthesis reaction in step (3) is carried out at 120℃ for 24h.

5. The method for preparing a catalytic membrane with a reproducible self-growing active layer as described in claim 4, characterized in that: The divalent metal cation is Co. 2+ Ca 2+ Mg 2+ Zn 2+ Mn 2+ Ni 2+ One of them, the anion is Cl. - NO3 - SO4 2- One of them, with a concentration of 0.001-0.5 mol / L; the trivalent metal cation is Al. 3+ Fe 3+ Cr 3+ One of them, the anion is Cl. - NO3 - SO4 2- One of them.

6. The application of the catalytic membrane with a repeatable self-growing active layer as described in claim 1 or the catalytic membrane with a repeatable self-growing active layer prepared by any of the methods in claims 2-5 as a catalyst in the depolymerization of lignin and the degradation of organic wastewater.

7. The application according to claim 6, characterized in that, When the catalytic membrane with the reproducible self-growing active layer is used as a catalyst to degrade organic wastewater, the operation is as follows: add the catalytic membrane with the reproducible self-growing active layer to the organic wastewater and shake.

8. The application according to claim 7, characterized in that: The catalytic membrane with a reproducible self-growing active layer is added to every 50 mL of organic wastewater; the shaking is performed in a shaker at 30–60 °C for 12 h; the organic wastewater is at least one of an antibiotic, a herbicide, or a dye; the herbicide is 2,4-dichlorophenoxyacetic acid, the antibiotic is tetracycline hydrochloride, and the dye is one of crystal violet, methylene blue, Congo red, or rhodamine B.

9. The application as described in claim 6, characterized in that, The catalytic membrane with a repeatable self-growing active layer is used as a catalyst in the depolymerization of lignin, and the operation steps are as follows: (i) Mix the catalytic membrane with the reproducible self-growing active layer, lignin, and reaction solvent evenly, replace the air with nitrogen, and seal the reaction vessel. (ii) Take the sealed reaction vessel from step (i) and heat it to react. After the reaction is completed, perform solid-liquid separation on the mixture obtained after the reaction in the reaction vessel and take the liquid product.

10. The application according to claim 9, characterized in that: The amount of catalytic membrane added in step (i) is 0.01–5 g; the lignin in step (i) is one of alkali lignin, lignin sulfonate, or organic solvent lignin; the amount of lignin added is 0.01–5 g; the amount of reaction solvent added in step (i) is 20%–40% of the volume of the reaction vessel; the reaction solvent in step (i) is an organic solvent and / or pure water; wherein, the organic solvent is methanol, ethanol, isopropanol, n-hexane, or acetone; when the reaction solvent is an organic solvent and pure water, the two are mixed in a volume ratio of 1:1–5:

1. The heating temperature in step (ii) is 200–280°C, and the reaction time is 0.5–12 h. There are two methods for solid-liquid separation in step (ii). When an organic solvent is used as the solvent for the depolymerization reaction, the reaction mixture is filtered through a 0.22 μm organic filter membrane to perform solid-liquid separation. The resulting solution is the liquid product containing phenolic compounds. When pure water or a mixture of organic and pure water is used as the reaction solvent, the reaction mixture is extracted with ethyl acetate. The extracted ethyl acetate phase is the liquid product obtained from the depolymerization, which is also the liquid product containing phenolic compounds.

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