Method for preparing multifunctional oil-water separation paper through ZIF-67 in-situ growth on surface of polydopamine coated fiber

Abstract

The invention discloses a method for preparing multifunctional oil-water separation paper through ZIF-67 in-situ growth on the surface of polydopamine coated fiber, and belongs to the technical field of preparation of fiber materials and composite materials thereof. The problems existing in an existing oil-water separation material preparation technology are solved. The method comprises the following steps: filter paper surface pretreatment; growing the MOF particles; and hydrophobic treatment. The product provided by the invention has self-cleaning and organic oil separation performances; the polydopamine and the silane with amino have rich amino, so that the polydopamine and the silane with amino have very high positive charge density during protonation, bacteria with negative charges can be attracted through electrostatic interaction, and the polydopamine and the ZIF-67 particles have a synergistic effect, so that the polydopamine and the ZIF-67 particles have an excellent inhibition effect on staphylococcus aureus. Oriented growth and controllability of MOF particles are achieved through loading of polydopamine on the surfaces of the fibers, and the super-hydrophobic paper is obtained; the method is simple, the process is easy to control, the cost is low, pollution is avoided, the oil-water separation performance is excellent, and the oil-water separation and antibacterial performance is achieved while the economic value of the filter paper is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fiber materials and their composite materials; specifically relates to a method for preparing multifunctional oil-water separation paper by in-situ growth of ZIF-67 on the surface of polydopamine-coated fibers. BACKGROUND

[0002] Water, as an important resource for humans and ecosystems, is under serious threat. Oil-containing wastewater pollution seriously affects water safety, and the global water environment is facing serious threats. Dangerous compounds in oil-containing wastewater pose a significant risk to human health and the ecosystem, and can cause potentially catastrophic consequences. Therefore, the importance of oil-water separation and the rational development of composite materials that can effectively remove organic pollutants from water have attracted global attention. Oil-containing wastewater comes from a wide range of sources, including oil spills at sea and the oil extraction industry. In the production processes of textile manufacturing, food processing, mechanical manufacturing, and metal industry, oil-containing wastewater is also generated. With changes in industrial production methods, the composition of organic and inorganic in oil-containing wastewater is complex and difficult to separate.

[0003] Inspired by the lotus leaf in nature, superhydrophobic materials have attracted widespread attention in the scientific community in the past three decades due to their unique water-repellent, antifouling, and self-cleaning properties. Paper, as the most common packaging material, plays an irreplaceable role in the entire industrial system. Giving the paper surface superhydrophobicity can effectively block water vapor and improve the water resistance and moisture resistance of the material, further expanding the application scenarios of the material. However, the preparation of superhydrophobic surfaces usually uses volatile organic compounds (VOCs) as solvents, which is costly and may pollute the environment during the preparation process. Therefore, it is necessary to develop environmentally friendly oil-water separation materials.

[0004] Zeolitic imidazolate frameworks (ZIFs) are a type of zeolite framework material generated by the reaction of Zn or Co as a metal source and imidazole as an organic ligand. Compared with MOFs, ZIFs have higher thermal and chemical stability. ZIF-67, as a typical ZIF material, is composed of metal atoms Co and dimethyl imidazole, and is generated by the reaction of zinc with imidazole as an organic ligand in methanol or N,N-dimethylformamide (DMF). ZIF-67 has customizable pore size and structure, which is beneficial for modification. These advantages make ZIF-67 widely used in separation, storage, catalysis, and other fields. In the field of oil-water separation, the positive charge on the surface of ZIF-67 forms a strong electrostatic attraction with the negatively charged oil droplets, and the hydrophobic interaction promotes the adsorption of oil droplets on the surface of ZIF-67; therefore, researchers have explored the application of ZIF-67 in oil-water separation. In addition, ZIF-67 exhibits inherent hydrophobicity, high adsorption capacity, high efficiency of separation, and excellent recyclability in oil / water separation applications, making it an excellent choice for offshore oil spill recovery materials. SUMMARY

[0005] The application aims to solve the above-mentioned problems existing in the preparation technology of the existing oil-water separation material, and provides a method for preparing multifunctional oil-water separation paper by coating the surface of fibers with polydopamine and growing ZIF-67 in situ.

[0006] A method for preparing multifunctional oil-water separation paper by coating the surface of fibers with polydopamine and growing ZIF-67 in situ, which is realized according to the following steps:

[0007] I. Surface pretreatment of filter paper: loading polydopamine on the surface of filter paper to obtain filter paper loaded with polydopamine;

[0008] II. Growth of MOF particles: immersing the above-mentioned surface pretreated filter paper in a MOF preparation solution for reaction to obtain filter paper with grown MOF particles;

[0009] III. Hydrophobic treatment: immersing the above-mentioned filter paper with grown MOF particles for hydrophobic treatment to obtain polydopamine directional induction ZIF-67@super-hydrophobic filter paper, that is, the method for preparing multifunctional oil-water separation paper by coating the surface of fibers with polydopamine and growing ZIF-67 in situ is completed.

[0010] Further, the specific preparation process of the surface pretreatment of filter paper in step I: using an aqueous solution of tris-hydroxymethyl aminomethane hydrochloride as a buffer solution, then adding sodium hydroxide solution to adjust the pH value to 8.5, then adding dopamine to obtain a mixed solution, then immersing the filter paper in the mixed solution for 12-24 h, washing and drying, then immersing in an ethanol / KH-550 solution for 1-2 h, then washing and drying to obtain filter paper loaded with polydopamine.

[0011] The concentration of the aqueous solution of tris-hydroxymethyl aminomethane hydrochloride is 0.02-0.05 mol / L; the concentration of dopamine in the mixed solution is 2-5 g / L.

[0012] The filter paper is cellulose filter paper with a diameter of 18 cm and ash content of 0.01; the ratio of anhydrous ethanol to KH-550 in the ethanol / KH-550 solution is (100-300) mL:(3-9) mL.

[0013] The washing and drying are performed twice, wherein the first washing and drying: washing with deionized water for 2-3 times and drying at 60-80℃ for 1-3 h; the second washing and drying: washing with anhydrous ethanol for 2-3 times and drying at 60℃ for 1 h.

[0014] Further, the specific preparation process of the growth of MOF particles in step II:

[0015] a. Dissolve cobalt nitrate hexahydrate in anhydrous methanol by stirring thoroughly, and record as solution A; dissolve dimethylimidazole in anhydrous methanol by stirring thoroughly, and record as solution B;

[0016] b. Soak the filter paper loaded with polydopamine in solution A, and stand for 30-60 min; then add solution B to solution A, and continue to stand for 1-8 h; then wash the filter paper with methanol and anhydrous ethanol alternately for 3-4 times, and dry at 60℃ to obtain the filter paper loaded with MOF particles.

[0017] The amount of cobalt nitrate hexahydrate in solution A in step a is 0.72-2.18 g, and the amount of anhydrous methanol is 50-150 mL.

[0018] The amount of dimethylimidazole in solution B in step a is 0.54-1.64 g, and the amount of anhydrous methanol is 50-150 mL.

[0019] Further, the specific process of the hydrophobic immersion treatment in step three is as follows: soak the filter paper loaded with MOF particles prepared in step two in an aqueous solution of hexadecyltrimethoxysilane in ethanol, and stand for 1-2 h; then wash the filter paper with methanol and anhydrous ethanol alternately for 3-4 times, and dry at 60℃ to obtain the polydopamine-directed and induced ZIF-67@superhydrophobic filter paper.

[0020] The ratio of hexadecyltrimethoxysilane, deionized water and ethanol in the aqueous solution of hexadecyltrimethoxysilane in ethanol is (1-5) ml:(2-10) ml:(40-200) ml.

[0021] The reaction principle of the application is as follows:

[0022] Filter paper is a porous paper filter medium made of fibrous materials (such as cotton fibers, wood pulp, etc.), which realizes solid-liquid or liquid-liquid separation through physical barrier effect. Paper chromatography is based on filter paper as an inert support. Filter paper fibers have strong affinity with water, which can absorb about 22% of water, and 6-7% of water is combined with the hydroxyl groups of cellulose in the form of hydrogen bonds, which is difficult to remove under normal conditions. The affinity of filter paper fibers with organic solvents is very weak, so general paper chromatography is actually based on the bound water of filter paper fibers as the stationary phase and organic solvents as the mobile phase. When the mobile phase passes through the sample along the paper, the solute on the sample point constantly distributes between water and organic phase. A part of the sample moves with the mobile phase into the solute-free zone, and then re-distributes. A part of the solute enters the stationary phase (water phase) from the mobile phase. With the continuous movement of the mobile phase, various parts constantly distribute according to their respective distribution coefficients and move along the mobile phase, so that the substances are separated and purified. Biomass is the most abundant carbon source material besides petrochemical materials. Under the background of the "double carbon" target, in addition to reasonably reducing the use of carbon-containing fossil fuels, thinking about how to high-value utilize biomass materials has become an important issue worthy of in-depth study. With the rapid development of social economy, the discharge of oily wastewater is gradually increasing, mainly from offshore oil spill accidents, oil exploitation, catering industry, etc. Oily wastewater is easy to cause water body hypoxia, mass death of aquatic organisms, and difficult degradation, which seriously endangers the ecological environment and human health. Therefore, there is an urgent need for a composite material to efficiently and environmentally friendly separate oily wastewater. Cellulose, as the main component of paper, has a large number of active hydroxyl groups. On the one hand, these abundant hydroxyl groups endow the paper surface with hydrophilicity. On the other hand, they provide an active reaction platform, through reaction with many functional reagents, the paper can be easily modified, and MOF particles can be grown on the surface of the paper, which has excellent oil-water separation performance after hydrophobic treatment.First, the paper is composed of fibers that are cross-linked with each other, has a porous three-dimensional network structure, and the pores between the fibers provide a channel for the passage of organic oil; second, the polydopamine is coated on the surface of the fibers, and then KH550 is grafted, the other end of KH550 (siloxane group -Si(OCH2CH3)3) can be hydrolyzed and form a firm chemical bond with the polymer matrix, greatly improve the interface bonding strength, and improve the performance of the composite material, and the polydopamine as an adhesive provides active sites for MOF growth; third, the MOF particles loaded on the surface of the fibers through the in-situ growth method increase the surface roughness of the paper, so that the paper has a large pore structure and a micro / nano two-layer surface roughness, and when the liquid contacts the solid surface, the surface groove is completely infiltrated by the liquid, that is, the actual contact area is larger than the flat surface area, and the hydrophobic performance of the paper can be improved by increasing the surface roughness; fourth, the paper can reduce the surface energy by immersing in a hexadecyl trimethoxysilane solution, and the hydrolysis of the hexadecyl trimethoxysilane forms active hydrophilic silanol (Si-OH), which reacts with the paper fibers through hydrogen bonds and chemical bonds to form a firm super-hydrophobic surface.

[0023] The beneficial effects of the present application are:

[0024] Through the excellent bonding effect of polydopamine and silane coupling agent, growth sites are provided for MOF particles, and zeolite imidazole acid framework (ZIF-67) particles are compounded with hydrophobic long-chain silane to prepare paper with micro / nano two-layer surface roughness and low surface energy. The cellulose filter paper has self-cleaning and organic oil separation performance; at the same time, the polydopamine and the amine group-containing silane have a very high positive charge density when protonated, and can attract negatively charged bacteria through electrostatic attraction, and the synergistic effect between the ZIF-67 particles makes it have excellent inhibition effect on Staphylococcus aureus.

[0025] The method for preparing the multifunctional oil-water separation paper in the present application is simple, the process is easy to control, the cost is low, and there is no pollution, which can improve the economic value of the cellulose filter paper and endow it with functional application.

[0026] The polydopamine prepared in the present application can specifically induce ZIF-67@ super-hydrophobic paper in the aspects of chemistry, physics (strength, separation, etc.), and antibacterial properties.

[0027] The present application is suitable for the preparation of polydopamine directional induction ZIF-67@ super-hydrophobic filter paper. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 SEM image of the polydopamine directed induced ZIF-67@superhydrophobic filter paper prepared in Example 1;

[0029] Figure 2 SEM image of the polydopamine directed induced ZIF-67@superhydrophobic filter paper prepared in Example 2;

[0030] Figure 3 Oil-water separation efficiency diagram of the polydopamine directed induced ZIF-67@superhydrophobic filter paper prepared in Example 2, wherein n-hexane represents n-hexane, petroleum ether represents petroleum ether, dichloromethane represents dichloromethane, carbon tetrachloride represents carbon tetrachloride, cylohexane represents cylohexane, and trichloromethane represents chloroform;

[0031] Figure 4 Bacteriostatic rate diagram of the polydopamine directed induced ZIF-67@superhydrophobic filter paper prepared in Example 2 against Staphylococcus aureus, wherein DPC represents paper coated with polydopamine, ZDP represents ZIF67-loaded polydopamine filter paper, and ZDP@HDTMS represents ZIF67-loaded polydopamine filter paper treated with HDTMS, i.e. polydopamine directed induced ZIF-67@superhydrophobic filter paper. DETAILED DESCRIPTION

[0032] The technical solution of the present application is not limited to the following specific embodiments, but also includes any combination of the specific embodiments.

[0033] Specific embodiment one: a method for preparing multifunctional oil-water separation paper by polydopamine coating fiber surface and in-situ growth of ZIF-67, which is realized according to the following steps:

[0034] I. Pre-treatment of filter paper surface: loading polydopamine on the surface of filter paper to obtain polydopamine-loaded filter paper;

[0035] II. Growth of MOF particles: immersing the above pre-treated filter paper in a MOF preparation solution for reaction to obtain filter paper with grown MOF particles;

[0036] III. Hydrophobic treatment: hydrophobic immersion treatment of the above filter paper with grown MOF particles to obtain polydopamine directed induced ZIF-67@superhydrophobic filter paper, i.e. the method for preparing multifunctional oil-water separation paper by polydopamine coating fiber surface and in-situ growth of ZIF-67 is completed.

[0037] The polydopamine is loaded on the surface of the filter paper in step one of the embodiment. In this process, the polydopamine is generated from the dopamine in the weak alkaline aqueous solution and is simultaneously loaded on the surface of the filter paper, which is used as the rivet site of the MOF particles to realize the directional and controllable growth of the MOF particles.

[0038] In step two of the embodiment, the filter paper after the surface pretreatment is immersed in the MOF preparation solution for reaction, so as to grow the MOF particles on the surface thereof.

[0039] Specific embodiment two: different from the specific embodiment one, the specific preparation process of the surface pretreatment of the filter paper in step one is as follows: the aqueous solution of tris-hydroxymethyl aminomethane hydrochloride is used as the buffer solution, then the sodium hydroxide solution is added to adjust the pH value to 8.5, then the dopamine is added to obtain a mixed solution, then the filter paper is soaked in the mixed solution for 12-24 h, and then the filter paper is washed and dried, and then the filter paper is soaked in the ethanol / KH-550 solution for 1-2 h, and then the filter paper is washed and dried to obtain the filter paper loaded with the polydopamine. The other steps and parameters are the same as those in the specific embodiment one.

[0040] Specific embodiment three: different from the specific embodiment two, the concentration of the aqueous solution of tris-hydroxymethyl aminomethane hydrochloride is 0.02-0.05 mol / L; and the concentration of the dopamine in the mixed solution is 2-5 g / L. The other steps and parameters are the same as those in the specific embodiment two.

[0041] Specific embodiment four: different from the specific embodiment two, the filter paper is the cellulose filter paper with a diameter of 18 cm and ash content of 0.01; and the ratio of the anhydrous ethanol to the KH-550 in the ethanol / KH-550 solution is (100-300) mL:(3-9) mL. The other steps and parameters are the same as those in the specific embodiment two.

[0042] Specific embodiment five: different from the specific embodiment two, the washing and drying are performed twice, wherein the first washing and drying is performed as follows: the filter paper is washed with the deionized water for 2-3 times, and then the filter paper is dried at 60-80℃ for 1-3 h; and the second washing and drying is performed as follows: the filter paper is washed with the anhydrous ethanol for 2-3 times, and then the filter paper is dried at 60℃ for 1 h. The other steps and parameters are the same as those in the specific embodiment two.

[0043] Specific embodiment six: different from the specific embodiment one, the specific preparation process of the growth of the MOF particles in step two is as follows:

[0044] a. the cobalt nitrate hexahydrate is fully stirred and dissolved in the anhydrous methanol to obtain solution A; and the dimethyl imidazole is fully stirred and dissolved in the anhydrous methanol to obtain solution B;

[0045] b. The filter paper loaded with polydopamine is soaked in solution A, and after standing for 30-60 min, solution B is added to solution A, and standing is continued for 1-8 h, then washing is performed 3-4 times alternately using methanol and anhydrous ethanol, and drying is performed at 60°C to obtain the filter paper on which MOF particles grow. The other steps and parameters are the same as in Embodiment I.

[0046] Embodiment VII: Different from Embodiment VI, the amount of cobalt nitrate hexahydrate in solution A in step a is 0.72-2.18 g, and the amount of anhydrous methanol is 50-150 mL. The other steps and parameters are the same as in Embodiment VI.

[0047] Embodiment VIII: Different from Embodiment VI, the amount of dimethylimidazole in solution B in step a is 0.54-1.64 g, and the amount of anhydrous methanol is 50-150 mL. The other steps and parameters are the same as in Embodiment VI.

[0048] Embodiment IX: Different from Embodiment I, the specific process of the hydrophobic impregnation treatment in step three is as follows: the filter paper on which MOF particles grow prepared in step two is soaked in an aqueous solution of hexadecyltrimethoxysilane in ethanol, and standing is performed for 1-2 h, then washing is performed 3-4 times alternately using methanol and anhydrous ethanol, and drying is performed at 60°C to obtain the polydopamine-directed induced ZIF-67@superhydrophobic filter paper. The other steps and parameters are the same as in Embodiment I.

[0049] Embodiment X: Different from Embodiment IX, the ratio of hexadecyltrimethoxysilane, deionized water and ethanol in the aqueous solution of hexadecyltrimethoxysilane in ethanol is (1-5) ml:(2-10) ml:(40-200) ml. The other steps and parameters are the same as in Embodiment IX.

[0050] The beneficial effects of the present application are verified by the following examples:

[0051] Example 1:

[0052] A method for preparing multifunctional oil-water separation paper by in-situ growth of ZIF-67 on a polydopamine-coated fiber surface is implemented in the following steps:

[0053] I. Surface pretreatment of the filter paper: loading polydopamine on the surface of the filter paper to obtain a filter paper loaded with polydopamine;

[0054] II. Growth of MOF particles: soaking the filter paper after the surface pretreatment in a MOF preparation solution to perform reaction, and obtaining a filter paper on which MOF particles grow;

[0055] III. Hydrophobic treatment: the filter paper on which the MOF particles grow is subjected to hydrophobic immersion treatment to obtain a ZIF-67@super-hydrophobic filter paper induced by polydopamine, i.e. the method for preparing a multifunctional oil-water separation paper by growing ZIF-67 in situ on the surface of the polydopamine-coated fibers is completed.

[0056] The specific preparation process of the filter paper surface pretreatment in step one of the embodiment is as follows: an aqueous solution of tris-hydroxymethyl aminomethane hydrochloride is used as a buffer solution, then sodium hydroxide solution is added to adjust the pH value to 8.5, dopamine is added to obtain a mixed solution, then the filter paper is soaked in the mixed solution for 24 h, washed and dried, then soaked in an ethanol / KH-550 solution for 2 h, washed and dried again to obtain a filter paper loaded with polydopamine;

[0057] The concentration of the aqueous solution of tris-hydroxymethyl aminomethane hydrochloride is 0.05 mol / L, i.e. 0.78 g of tris-hydroxymethyl aminomethane hydrochloride is added to 200 ml of deionized water; the concentration of dopamine in the mixed solution is 5 g / L, i.e. 1 g of dopamine is added;

[0058] The filter paper is cellulose filter paper with a diameter of 18 cm and ash content of 0.01; the ratio of anhydrous ethanol to KH-550 in the ethanol / KH-550 solution is 200 mL:6 mL;

[0059] The washing and drying are performed twice, wherein the first washing and drying: washing with deionized water for 3 times and drying at 60℃ for 1 h; the second washing and drying: washing with anhydrous ethanol for 3 times and drying at 60℃ for 1 h.

[0060] The specific preparation process of the growth of the MOF particles in step two of the embodiment is as follows:

[0061] a. Cobalt nitrate hexahydrate and anhydrous methanol are fully stirred and dissolved to obtain solution A; dimethyl imidazole and anhydrous methanol are fully stirred and dissolved to obtain solution B;

[0062] b. The filter paper loaded with polydopamine is soaked in solution A, and after standing for 30 min, solution B is added to solution A, and the solution is continuously stood for 2 h, then washed with methanol and anhydrous ethanol alternately for 3 times, and dried at 60℃ to obtain a filter paper on which MOF particles grow;

[0063] The amount of cobalt nitrate hexahydrate in solution A in step a is 2.18 g, and the amount of anhydrous methanol is 150 mL;

[0064] The amount of dimethyl imidazole in solution B in step a is 1.64 g, and the amount of anhydrous methanol is 150 mL.

[0065] The specific process of the hydrophobic impregnation treatment in step three of this embodiment is as follows: The filter paper with MOF particles grown in step two is soaked in an ethanol aqueous solution of hexadecyltrimethoxysilane, left to stand for 2 hours, and then washed three times alternately with methanol and anhydrous ethanol, and dried at 60°C to obtain polydopamine-directed induced ZIF-67@ superhydrophobic filter paper.

[0066] The ratio of hexadecyltrimethoxysilane, deionized water, and ethanol in the aqueous ethanol solution of hexadecyltrimethoxysilane is 5 ml: 10 ml: 200 ml.

[0067] Example 2:

[0068] The difference between this embodiment and embodiment 1 is that in step b, the sample is left to stand for another 8 hours; otherwise, it is the same as in embodiment 1.

[0069] result:

[0070] from Figure 1 As shown, the polydopamine-directed induced ZIF-67@ superhydrophobic filter paper prepared in Example 1 successfully grew MOF particles on the fiber surface, and the MOF particle density was relatively low.

[0071] from Figure 2 As shown, the polydopamine-directed induced ZIF-67@ superhydrophobic filter paper prepared in Example 2 successfully grew MOF particles on the fiber surface, and the MOF particle density was very high.

[0072] from Figure 3 As shown, the polydopamine-directed induced ZIF-67@ superhydrophobic filter paper prepared in Example 2 exhibited excellent separation effects on different oil-water mixtures, with all tested liquids having a separation efficiency exceeding 97%.

[0073] from Figure 4 As shown, the polydopamine-directed induced ZIF-67@superhydrophobic filter paper prepared in Example 2 has an excellent antibacterial rate against Staphylococcus aureus. Polydopamine and amine-containing silanes have abundant amine groups, which give them a very high positive charge density when protonated. They can attract negatively charged bacteria through electrostatic interaction. The synergistic effect between polydopamine and ZIF-67 particles makes its antibacterial rate against Staphylococcus aureus reach 84%.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 multifunctional oil-water separation paper by in-situ growth of ZIF-67 on the surface of polydopamine-coated fibers, characterized in that It is carried out in the following steps: I. Surface pretreatment of filter paper: load polydopamine on the surface of filter paper to obtain polydopamine-loaded filter paper; II. Growth of MOF particles: immerse the above surface pretreated filter paper in the MOF preparation solution for reaction to obtain the filter paper with grown MOF particles; III. Hydrophobic treatment: perform hydrophobic immersion treatment on the above filter paper with grown MOF particles to obtain polydopamine directional induction ZIF-67@ super-hydrophobic filter paper, i.e. complete the method for preparing multifunctional oil-water separation paper by polydopamine coating fiber surface and in-situ growth of ZIF-67.

2. The method for preparing multifunctional oil-water separation paper by in-situ growth of ZIF-67 on the surface of polydopamine-coated fibers according to claim 1, characterized in that The specific preparation process of the surface pretreatment of filter paper in step I: use a solution of tris-hydroxymethyl aminomethane hydrochloride as a buffer solution, then add sodium hydroxide solution to adjust the pH value to 8.5, then add dopamine to obtain a mixed solution, then immerse the filter paper in the mixed solution for 12-24 h, wash and dry, then immerse in an ethanol / KH-550 solution for 1-2 h, then wash and dry to obtain the polydopamine-loaded filter paper.

3. The method according to claim 2, wherein the polydopamine-coated fiber surface is in-situ grown with ZIF-67 to prepare multifunctional oil-water separation paper. The concentration of the solution of tris-hydroxymethyl aminomethane hydrochloride is 0.02-0.05 mol / L; the concentration of dopamine in the mixed solution is 2-5 g / L.

4. The method for preparing multifunctional oil-water separation paper by in-situ growth of ZIF-67 on the surface of polydopamine-coated fibers according to claim 2, characterized in that The filter paper is cellulose filter paper with a diameter of 18 cm and ash content of 0.01; the ratio of anhydrous ethanol to KH-550 in the ethanol / KH-550 solution is (100-300) mL:(3-9) mL.

5. The method of claim 2, wherein the polydopamine-coated fiber surface is in-situ grown with ZIF-67 to prepare multifunctional oil-water separation paper. The washing and drying are performed twice, wherein the first washing and drying: wash with deionized water for 2-3 times, dry at 60-80℃ for 1-3 h; the second washing and drying: wash with anhydrous ethanol for 2-3 times, dry at 60℃ for 1 h.

6. The method of claim 1, wherein the polydopamine-coated fiber surface is in-situ grown with ZIF-67 to prepare multifunctional oil-water separation paper. The specific preparation process of the growth of MOF particles in step II: a. fully stir and dissolve cobalt nitrate hexahydrate in anhydrous methanol to obtain solution A; fully stir and dissolve dimethyl imidazole in anhydrous methanol to obtain solution B; b. immerse the polydopamine-loaded filter paper in solution A, stand for 30-60 min, then add solution B to solution A, continue to stand for 1-8 h, then wash with methanol and anhydrous ethanol alternately for 3-4 times, dry at 60℃ to obtain the filter paper with grown MOF particles.

7. The method of claim 6, wherein the polydopamine-coated fiber surface is in-situ grown with ZIF-67 to prepare multifunctional oil-water separation paper. The amount of cobalt nitrate hexahydrate in solution A in step a is 0.72-2.18 g, and the amount of anhydrous methanol is 50-150 mL.

8. The method of claim 6, wherein the polydopamine-coated fiber surface is in-situ grown with ZIF-67 to prepare multifunctional oil-water separation paper. The amount of dimethyl imidazole in solution B in step a is 0.54-1.64 g, and the amount of anhydrous methanol is 50-150 mL.

9. The method of claim 1, wherein the polydopamine-coated fiber surface is in-situ grown with ZIF-67 to prepare multifunctional oil-water separation paper. The specific process of the hydrophobic immersion treatment in step III: immerse the filter paper with grown MOF particles prepared in step II in an ethanol aqueous solution of hexadecyl trimethoxysilane, stand for 1-2 h, then wash with methanol and anhydrous ethanol alternately for 3-4 times, dry at 60℃ to obtain the polydopamine directional induction ZIF-67@ super-hydrophobic filter paper.

10. The method of claim 9, wherein the polydopamine-coated fiber surface is in-situ grown with ZIF-67 to prepare multifunctional oil-water separation paper. The ratio of hexadecyl trimethoxysilane, deionized water and ethanol in the ethanol aqueous solution of hexadecyl trimethoxysilane is (1-5) ml:(2-10) ml:(40-200) ml.

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