Carbonized Co-MOF powder, supported film, sandwich-structured confined catalytic film and preparation method

Abstract

The present invention discloses a carbonized Co-MOF powder, a supported membrane, a sandwich-structured confined catalytic membrane and a preparation method thereof. The preparation method of the carbonized Co-MOF powder includes: A1: Dissolving a cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid in N,N-dimethylformamide to form a first solution; A2: After the first solution is completely dissolved, performing a hydrothermal reaction on the first solution; A3: Standing and aging the product obtained in step A2, followed by centrifugal washing to obtain a precipitate; A4: Drying and grinding the precipitate to obtain Co-MOF powder; A5: Heating and carbonizing the Co-MOF powder and then grinding it to obtain carbonized Co-MOF powder. The present invention provides a new construction of a confined space, effectively improving the degradation efficiency and removal rate of new pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly to a carbonized Co-MOF powder, a supported membrane, a sandwich-structured confined catalytic membrane and a preparation method thereof. Background Art

[0002] Advanced oxidation technologies (AOPs) have attracted extensive attention due to their advantages such as high efficiency, thorough treatment and easy operation. The sulfate radical-based advanced oxidation process (SR-AOPs) has received more extensive favor due to its higher redox potential, longer half-life and stronger pH adaptability. However, traditional homogeneous SR-AOPs have many drawbacks, such as difficult catalyst recovery, serious metal ion leaching, short lifespan of active species, etc.

[0003] Membrane technology can effectively alleviate such problems. Loading the catalyst on the membrane can effectively improve the reusability of the catalyst and reduce the leaching of metal ions. Moreover, the membrane also has a retention effect, thereby further enhancing the degradation effect of pollutants. In order to further improve the catalytic performance of the membrane, the membrane-based nano-confined catalytic technology has been gradually proposed. Nano-confinement means that when the reaction is confined in a nano-scale space, the physicochemical properties of the catalyst will change significantly, mainly including the electronic form, mass transfer path and phase behavior. The confined space shortens the mass transfer path, makes the active species not easily inactivated, and significantly improves the interaction between pollutants and active species. However, the construction of the confined space is a major challenge for high-performance catalytic membranes.

[0004] The disclosure of the above background art content is only used to assist in understanding the concept and technical solution of the present invention, and it does not necessarily belong to the prior art of this patent application. Without clear evidence indicating that the above content was publicly available at the filing date of this patent application, the above background art should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a carbonized Co-MOF powder, a supported membrane, a sandwich-structured confined catalytic membrane and a preparation method thereof, providing a new construction of a confined space, effectively improving the degradation efficiency and removal rate of new pollutants.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention discloses a preparation method of a carbonized Co-MOF powder, comprising the following steps:

[0008] A1: Dissolve cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid in N,N-dimethylformamide to make a first solution;

[0009] A2: After the first solution is completely dissolved, perform a hydrothermal reaction on the first solution;

[0010] A3: Let the product obtained in step A2 stand for aging and then perform centrifugal washing to obtain a precipitate;

[0011] A4: Dry and grind the precipitate to obtain Co-MOF powder;

[0012] A5: Heat and carbonize the Co-MOF powder and then grind it to obtain carbonized Co-MOF powder.

[0013] Preferably, in step A1, the cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid are dissolved in N,N-dimethylformamide in a molar ratio of 1:(0.5~2).

[0014] Preferably, the concentration of the cobalt salt in the first solution is 0.01 mol / L to 0.02 mol / L.

[0015] Preferably, the conditions for the hydrothermal reaction in step A2 are 60°C to 100°C and the time is 24 h to 72 h.

[0016] Preferably, step A3 includes letting the product obtained in step A2 stand for aging at room temperature for 24 h to 72 h, and washing the aged product with N,N-dimethylformamide and pure water under centrifugation conditions at least three times, where the centrifugation rate during centrifugation is 8000 r / min to 10000 r / min and the centrifugation time for one wash is 5 min to 10 min.

[0017] Preferably, the temperature for drying the precipitate in step A4 is 40°C to 70°C and the time is 8 h to 24 h.

[0018] Preferably, step A5 includes adding the Co-MOF powder to a furnace body for heating and carbonization, where the heating rate of the furnace body is 5°C / min to 10°C / min, the temperature for heating and carbonization is 400°C to 600°C, and the time is 1 h to 2 h.

[0019] In the second aspect, the present invention discloses a carbonized Co-MOF powder prepared by using the preparation method of the carbonized Co-MOF powder described in the first aspect.

[0020] In the third aspect, the present invention discloses a preparation method of a carbonized Co-MOF supported membrane, including the following steps:

[0021] B1: Dissolve the carbonized Co-MOF powder described in the second aspect in pure water to obtain a suspension;

[0022] B2: Provide the first polymer membrane, filter the suspension onto the first polymer membrane, and dry it to obtain a carbonized Co-MOF supported membrane.

[0023] Preferably, in step B1, the carbonized Co-MOF powder described in the second aspect is dissolved in pure water to obtain a dispersion with a concentration of 6.3 mg / L to 63 mg / L, and then the dispersion is ultrasonically treated to obtain a uniformly dispersed suspension.

[0024] Preferably, during the ultrasonic treatment in step B1, the ultrasonic dispersion power is 50 W to 2000 W, and the time is 20 min to 60 min.

[0025] Preferably, the loading amount of the carbonized Co-MOF powder in the carbonized Co-MOF supported membrane obtained in step B2 is 0.1 mg / cm 2 ~1.0 mg / cm 2 .

[0026] Preferably, the first polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyethersulfone, polysulfone, and cellulose acetate, and the average pore size of the first polymer membrane is 0.22 μm to 0.45 μm.

[0027] Fourth aspect, the present invention discloses a carbonized Co-MOF supported membrane, which is prepared by using the preparation method of the carbonized Co-MOF supported membrane described in the third aspect.

[0028] Fifth aspect, the present invention discloses a preparation method of a carbonized Co-MOF sandwich structure confined catalytic membrane, including the following steps: Provide the second polymer membrane, and cover the second polymer membrane on the side of the carbonized Co-MOF supported membrane for filtering the suspension, and obtain a carbonized Co-MOF sandwich structure confined catalytic membrane after pressing.

[0029] Preferably, the second polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyethersulfone, polysulfone, and cellulose acetate, and the average pore size of the second polymer membrane is 0.22 μm to 0.45 μm.

[0030] Preferably, the pressure during the pressing process is 5 MPa to 20 MPa, and the time is 1 min to 5 min.

[0031] Sixth aspect, the present invention discloses a carbonized Co-MOF sandwich structure confined catalytic membrane, which is prepared by using the preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane described in the fifth aspect.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: The carbonized Co-MOF powder, supported membrane, sandwich-structured confined catalytic membrane and their preparation methods proposed by the present invention are used to prepare a structurally stable carbonized Co-MOF catalytic material through solvothermal reaction, room-temperature aging and high-temperature carbonization, achieving a high degradation efficiency and removal rate for new pollutants. Further, the structurally stable carbonized Co-MOF catalytic material is loaded on a polymer membrane, and the prepared carbonized Co-MOF supported membrane can also achieve a high degradation efficiency and removal rate for new pollutants. Furthermore, by changing the configuration, a carbonized Co-MOF sandwich-structured confined catalytic membrane is designed to form a "membrane - catalytic material - membrane" sandwich structure. First, the problem of easy detachment of the catalytic material is solved. Second, a sufficient confined space is formed, and the increase in the confined space further effectively improves the degradation efficiency and removal rate of new pollutants, and good removal of various types of pollutants can be achieved. Third, it can also isolate large particle pollutants, prevent pollutants from adhering to the surface of the catalytic material and causing a decrease in the number of active sites, and effectively prevent the influence of membrane fouling on the catalytic effect. Fourth, it isolates the catalytic material from being directly washed by water flow, avoids the catalyst from falling off the membrane surface, resulting in a decrease in performance and metal leaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the flowchart of the preparation method of the carbonized Co-MOF powder disclosed in Example 1 of the present invention;

[0034] Figure 2 is the SEM image of the morphology of the carbonized Co-MOF powder in Example 2 of the present invention;

[0035] Figure 3 is the flowchart of the preparation method of the carbonized Co-MOF supported membrane disclosed in Example 3 of the present invention;

[0036] Figure 4 is the flowchart of the preparation method of the carbonized Co-MOF sandwich-structured confined catalytic membrane disclosed in Example 5 of the present invention;

[0037] Figure 5 is the SEM image of the surface morphology of the carbonized Co-MOF sandwich-structured confined catalytic membrane in Example 6 of the present invention;

[0038] Figure 6a is the carbonized Co-MOF sandwich-structured confined catalytic membrane with a loading amount of 0.1 mg / cm 2 of the local cross-sectional morphology SEM image;

[0039] Figure 6b is the carbonized Co-MOF sandwich-structured confined catalytic membrane with a loading amount of 0.1 mg / cm 2 of the overall cross-sectional morphology SEM image;

[0040] Figure 7a is the SEM cross-sectional morphology diagram of the carbonized Co-MOF sandwich structure confined catalytic membrane with a loading of 0.5 mg / cm 2 ;

[0041] Figure 7b is the EDS cross-sectional morphology diagram of the carbonized Co-MOF sandwich structure confined catalytic membrane with a loading of 0.5 mg / cm 2 ;

[0042] Figure 8 is a comparative schematic diagram of the removal effects of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS, carbonized Co-MOF powder / PMS, carbonized Co-MOF sandwich structure confined catalytic membrane, and PMS on ranitidine respectively;

[0043] Figure 9a The figure shows a comparative schematic diagram of the degradation performance of the carbonized Co-MOF supported membrane / PMS and the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS on ranitidine;

[0044] Figure 9b is a comparative schematic diagram of the kinetic reaction constant results of the carbonized Co-MOF supported membrane / PMS and the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS on ranitidine;

[0045] Figure 10 is a comparative schematic diagram of the removal effects of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS and the carbonized Co-MOF supported membrane / PMS on ranitidine under the influence of humic acid respectively;

[0046] Figure 11 is a schematic diagram of the degradation effect of the carbonized Co-MOF sandwich structure confined catalytic membrane on various new pollutants in water;

[0047] Figure 12 is a comparative schematic diagram of the degradation performance of the carbonized Co-MOF sandwich structure confined catalytic membrane with different loadings on ranitidine after activating PMS. Specific Embodiments

[0048] The following provides a detailed description of the embodiments of the present invention. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0049] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, the connection can be for fixing or for circuit / signal connection.

[0050] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0051] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0052] Metal-organic frameworks (MOFs) have the advantages of adjustable structure, unique properties, large specific surface area, and rich pores as catalytic materials, and are an excellent choice for constructing nano-confined spaces. The flexibility of the MOF structure is conducive to the construction of the confined space, and the large specific surface area provides abundant active sites, alleviating the problem of the short lifetime of free radicals.

[0053] However, MOFs are very unstable, especially in the field of AOPs. In addition to the structural damage caused by the action of water, the active free radicals generated by AOPs are also likely to attack the coordination bonds of MOFs, resulting in structural damage. Therefore, although the catalytic performance of MOFs in many studies is excellent, their stability is very poor, and the catalytic effects are basically only explored several times or at most within a few hours, without long-term operation effects. Therefore, for the application of AOPs, how to improve the stability of MOFs is an urgent problem to be solved. Moreover, for catalytic membranes, the catalytic materials loaded on the membranes are also likely to detach from the membrane substrate under the scouring of water flow, resulting in a decline in catalytic performance and the leaching of metals, thus leading to a relatively high environmental risk.

[0054] Generally speaking, the instability of MOFs materials, the shedding of catalytic materials, and the construction of confined spaces are important factors restricting the high performance of MOF catalytic membranes. Therefore, the invention of catalytic materials and the improvement of membrane configurations will extend the service life of catalytic membranes, improve the reaction performance of catalytic membranes, and reduce environmental safety risks.

[0055] To solve the problem of the instability of MOFs in the AOPs system, in the present invention, a structurally stable carbonized Co-MOF catalytic material is prepared through solvothermal reaction, room-temperature aging, and high-temperature carbonization. At the same time, to construct a confined space and solve the problem of easy shedding of catalytic materials, a tablet press is used to sandwich the obtained Co-MOF catalytic material between two polymer-based membranes to form a "membrane-catalytic material-membrane" sandwich structure. Such a structure can achieve efficient removal of new pollutants in water with a relatively low catalyst dosage.

[0056] As Figure 1 shown, Example 1 of the present invention discloses a preparation method of carbonized Co-MOF powder, which includes the following steps:

[0057] A1: Dissolve cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid in N,N-dimethylformamide to make a first solution;

[0058] Among them, the cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid are dissolved in N,N-dimethylformamide according to a molar ratio of 1:(0.5~2), and the concentration of the cobalt salt in the first solution is 0.01 mol / L to 0.02 mol / L. The cobalt salt is preferably cobalt nitrate.

[0059] A2: After the first solution is completely dissolved, carry out a hydrothermal reaction on the first solution;

[0060] Specifically, ultrasonically treat the first solution for a period of time until it is completely dissolved, and then place it in an oven for hydrothermal reaction. The conditions of the hydrothermal reaction are 60°C to 100°C, and the time is 24 h to 72 h.

[0061] A3: Let the product obtained in step A2 stand for aging and then carry out centrifugal washing to obtain a precipitate;

[0062] Specifically, let the product obtained in step A2 stand for aging at room temperature for 24 h to 72 h, and wash the aged product with N,N-dimethylformamide and pure water under centrifugal conditions at least three times to remove excess impurities. During the centrifugation process, the centrifugation rate is 8000 r / min to 10000 r / min, and the centrifugation time for one washing is 5 min to 10 min.

[0063] A4: Dry and grind the precipitate to obtain Co-MOF powder;

[0064] Specifically, the precipitate is placed in an oven and dried for a period of time, and the product is ground using a mortar to obtain brown powder Co-MOF; wherein, the temperature of the oven is 40°C to 70°C, and the drying time is 8 h to 24 h.

[0065] A5: The Co-MOF powder is heated and carbonized and then ground to obtain carbonized Co-MOF powder.

[0066] Specifically, the Co-MOF powder is placed in a crucible and heated at a high temperature in a tube furnace for a certain time, and the product is ground using a mortar to obtain black powder carbonized Co-MOF. Among them, the heating rate of the tube furnace is 5°C / min to 10°C / min, the temperature of heating and carbonization is 400°C to 600°C, and the time is 1 h to 2 h.

[0067] Example two of the present invention discloses a carbonized Co-MOF powder, which is prepared by using the preparation method of the carbonized Co-MOF powder in Example one. As Figure 2 shown is the SEM (scanning electron microscope) image of the morphology of the carbonized Co-MOF powder of this example. It can be seen from the SEM image of the morphology of the Co-MOF powder that the carbonized Co-MOF powder prepared by the preparation method of the carbonized Co-MOF powder in Example one of the present invention contains multiple block structures composed of small fragments, providing good conditions for constructing a confined space for the subsequent formation of a sandwich structure confined catalytic membrane by vacuum filtration.

[0068] The removal of new pollutants can be achieved by using this carbonized Co-MOF powder, and the specific steps are as follows:

[0069] E1: The carbonized Co-MOF powder and PMS are added into a beaker containing ranitidine aqueous solution and placed on a magnetic stirrer for reaction. At certain time intervals, a certain amount of the degradation solution is sucked out by a syringe and filtered using a PVDF membrane, and the catalytic degradation efficiency is characterized by the filtrate. The absorbance of the filtrate is detected at a wavelength of 314 nm using an ultraviolet-visible spectrophotometer, and the residual concentration and degradation rate of ranitidine are calculated using a standard working curve. Among them, the concentration of ranitidine is preferably 5 mg / L to 10 mg / L; based on the principle of good degradation effect and small PMS dosage, the concentration of PMS is 0.1 mmol / L to 0.2 mmol / L; the concentration of carbonized Co-MOF is 40 mg / L to 50 mg / L, the rotation speed of the magnetic stirrer is 200 r / min to 300 r / min; the volume of the degradation solution sucked is 1 mL to 2 mL; the pore size of the PVDF membrane is 0.22 μm to 0.45 μm.

[0070] As Figure 3 shown, Example three of the present invention discloses a preparation method of a carbonized Co-MOF supported membrane, including the following steps:

[0071] B1: Dissolve the carbonized Co-MOF powder in Example 2 in pure water to obtain a suspension.

[0072] Specifically, dissolve the carbonized Co-MOF powder in Example 2 in pure water, and ultrasonicate for a certain time to obtain a uniformly dispersed suspension. Among them, the carbonized Co-MOF powder is dissolved in pure water to obtain a dispersion with a concentration of 6.3 mg / L to 63 mg / L, and then the dispersion is ultrasonically treated to obtain a uniformly dispersed suspension. The ultrasonic dispersion power during the ultrasonic treatment is 50 W to 2000 W, and the time is 20 min to 60 min, preferably 30 min.

[0073] B2: Provide a first polymer membrane, filter the suspension onto the first polymer membrane, and dry it to obtain a carbonized Co-MOF loaded membrane.

[0074] Specifically, filter the suspension onto the first polymer membrane by vacuum filtration and place it in an oven for drying to obtain a carbonized Co-MOF loaded membrane. Among them, the first polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyethersulfone, polysulfone, and cellulose acetate. The average pore size of the first polymer membrane is 0.22 μm to 0.45 μm. The temperature of the oven is 40 °C to 70 °C, and the drying time is 1 h to 2 h. The loading amount of the carbonized Co-MOF powder in the carbonized Co-MOF loaded membrane is 0.1 mg / cm 2 ~1.0 mg / cm 2 ; In a more preferred embodiment, the loading amount of the carbonized Co-MOF powder in the carbonized Co-MOF loaded membrane is 0.1 mg / cm 2 ~0.5 mg / cm 2 ; Among them, the loading amount of the carbonized Co-MOF powder being 0.1 mg / cm 2 is the best. Specifically, for example, on a 12.56 cm 2 first polymer membrane, 100 mL to 200 mL of the suspension is filtered onto the first polymer membrane by vacuum filtration.

[0075] Example 4 of the present invention discloses a carbonized Co-MOF loaded membrane, which is prepared by the preparation method of the carbonized Co-MOF loaded membrane in Example 3.

[0076] Using this carbonized Co-MOF loaded membrane can achieve the removal of new pollutants under self-gravity conditions. The specific steps are as follows:

[0077] E2: Place the carbonized Co-MOF supported membrane in a suction filtration device. The target pollutant is ranitidine, and the oxidant is peroxymonosulfate (PMS). Under self-gravity, filter the aqueous solution of ranitidine added with PMS, and take filtrate samples at certain time intervals to characterize the catalytic degradation efficiency. Use a UV-visible spectrophotometer to detect the absorbance of the filtrate at a wavelength of 314 nm, and use the standard working curve to calculate the residual concentration and degradation rate of ranitidine. Among them, the concentration of ranitidine is preferably 5 mg / L to 10 mg / L; based on the principle of good degradation effect and small PMS dosage, the concentration of PMS is 0.1 mmol / L to 0.2 mmol / L; the gravity flow pressure (characterized by the liquid injection head height) is 10 cm to 15 cm. Specifically, for example, the concentration of ranitidine is 5 mg / L, the concentration of PMS is 0.2 mmol / L, and the gravity flow pressure (characterized by the liquid injection head height) is 12 cm.

[0078] As Figure 4 shown, Example 5 of the present invention discloses a preparation method of a carbonized Co-MOF sandwich structure confined catalytic membrane, which includes the following steps:

[0079] C1: Provide a second polymer membrane, and cover one side of the suction filtration suspension of the carbonized Co-MOF supported membrane, and obtain a carbonized Co-MOF sandwich structure confined catalytic membrane after pressing.

[0080] Specifically, place the carbonized Co-MOF supported membrane in a tablet press, cover it with another layer of second polymer membrane, and apply pressure for a certain time to obtain a carbonized Co-MOF sandwich structure confined catalytic membrane. Among them, the second polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyethersulfone, polysulfone, and cellulose acetate, and the average pore size of the second polymer membrane is 0.22 μm to 0.45 μm. The pressure of the tablet press is 5 MPa to 20 MPa, and the film pressing time is 1 min to 5 min.

[0081] Example 6 of the present invention discloses a carbonized Co-MOF sandwich structure confined catalytic membrane, which is prepared by using the preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane in Example 5. As Figure 5 shown, it is the SEM image of the surface morphology of the carbonized Co-MOF sandwich structure confined catalytic membrane. As Figure 6a and Figure 6b shown, it is the SEM image of the cross-sectional morphology of the carbonized Co-MOF sandwich structure confined catalytic membrane with a loading amount of 0.1 mg / cm 2 . As Figure 7a shown, it is the SEM image of the cross-sectional morphology of the carbonized Co-MOF sandwich structure confined catalytic membrane with a loading amount of 0.5 mg / cm 2 . As Figure 7bThe cross-sectional morphology EDS (energy-dispersive X-ray spectroscopy) diagram of the carbonized Co-MOF sandwich structure confined catalytic membrane with a loading of 0.5 mg / cm 2 is shown. Among them, it can be seen from Figure 5 that the surface of the carbonized Co-MOF sandwich structure confined catalytic membrane is uniform and flat, and some pores are compacted but most of them are still retained; Figure 6a is a local view. It can be seen from Figure 6a that the carbonized Co-MOF catalytic material is embedded inside the interlayer; Figure 6b is the overall cross-sectional view of the membrane. It can be seen from Figure 6b that the thickness becomes 11.2 μm, shrinking to 50% of the original, and the upper and lower layers are cross-linked and gradually integrated. For more intuitive observation, when the loading is increased to 0.5 mg / cm 2 , the interlayer boundary can be clearly seen from Figure 7a . The EDS spectrum of the membrane cross-section shown in Figure 7b also shows that the material is evenly sandwiched in the middle, proving the successful formation of the sandwich structure.

[0082] The use of this carbonized Co-MOF sandwich structure confined catalytic membrane can achieve the removal of new pollutants, and the specific steps are as follows:

[0083] E3: Place the carbonized Co-MOF sandwich structure confined catalytic membrane in a suction filtration device. The target pollutant is ranitidine, and the oxidant is peroxymonosulfate (PMS). Under a certain pressure, filter the ranitidine aqueous solution added with PMS, and take filtrate samples at certain time intervals to characterize the catalytic degradation efficiency. Use a UV-visible spectrophotometer to detect the absorbance of the filtrate at a wavelength of 314 nm, and use the standard working curve to calculate the residual concentration and degradation rate of ranitidine. Among them, the ranitidine concentration is preferably 5 mg / L to 10 mg / L; based on the principle of good degradation effect and small PMS dosage, the PMS concentration is 0.1 mmol / L to 0.2 mmol / L; the external pressure is 0.8 MPa to 1.0 MPa. Specifically, for example, the ranitidine concentration is 5 mg / L, the PMS concentration is 0.2 mmol / L, and the external pressure is 0.8 MPa.

[0084] Among them, to ensure a comparable flux for normal operation, in the embodiments of the present invention, when using the carbonized Co-MOF loaded membrane to remove new pollutants, the self-gravity effect can be directly used, while when using the carbonized Co-MOF sandwich structure confined catalytic membrane to remove new pollutants, a certain pressure is applied.

[0085] The following specific examples further elaborate in detail on the carbonized Co-MOF powder and its preparation method, the carbonized Co-MOF supported membrane and its preparation method, and the carbonized Co-MOF sandwich structure confined catalytic membrane and its preparation method in the above-mentioned respective examples.

[0086] The preparation methods of the carbonized Co-MOF powder, the carbonized Co-MOF supported membrane, and the carbonized Co-MOF sandwich structure confined catalytic membrane in this specific example include:

[0087] S1: Weigh 0.1 mmol of cobalt nitrate and 0.2 mmol of 4-(1H-tetrazol-5-yl)benzoic acid in 9 mL of N,N-dimethylformamide solution, ultrasonically dissolve to obtain a first solution, and place it in an oven at 60 °C for hydrothermal reaction for 24 h.

[0088] S2: Let the solution after hydrothermal reaction stand at room temperature and age for 24 h.

[0089] S3: Centrifuge and wash the aged product three times with N,N-dimethylformamide and pure water at high speed to remove surface impurities.

[0090] S4: Place the product in an oven at 60 °C and dry for 12 h, and grind the material into powder with a mortar to obtain Co-MOF powder.

[0091] S5: Place the Co-MOF powder in a tube furnace, heat it at 500 °C for 2 h, and then grind the product to obtain carbonized Co-MOF powder.

[0092] S6: Disperse the carbonized Co-MOF powder in pure water and ultrasonicate for 30 min to obtain a uniformly dispersed carbonized Co-MOF suspension.

[0093] S7: Prepare a PVDF bottom membrane, and load the carbonized Co-MOF suspension onto the PVDF bottom membrane by vacuum filtration. The loading amount is 0.1 mg / cm 2 , and place it in an oven at 60 °C for drying to obtain a carbonized Co-MOF supported membrane.

[0094] S8: Prepare a PVDF base membrane, cover the surface of the carbonized Co-MOF supported membrane loaded with carbonized Co-MOF with the PVDF base membrane, and press the membrane at 10 MPa for 1 min with a tablet press to obtain a carbonized Co-MOF sandwich structure confined catalytic membrane.

[0095] As Figure 8 shown, it is a comparative schematic diagram of the removal effects of ranitidine by the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS, the carbonized Co-MOF powder / PMS, the carbonized Co-MOF sandwich structure confined catalytic membrane, and PMS respectively. Among them, C in the ordinate t$C$ represents the concentration of ranitidine after the reaction, and $C_0$ represents the initial concentration of ranitidine. Among them, the test of the removal effect of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS on ranitidine is carried out by using the carbonized Co-MOF sandwich structure confined catalytic membrane obtained in the above step S8 to execute step E3 to test the residual concentration and degradation rate of ranitidine; the test of the removal effect of the carbonized Co-MOF powder / PMS on ranitidine is carried out by using the carbonized Co-MO powder obtained in the above step S5 to execute step E1 to test the residual concentration and degradation rate of ranitidine. In addition, two control groups are added. In one control group, the carbonized Co-MOF sandwich structure confined catalytic membrane obtained in step S8 is also placed in a suction filtration device to degrade new pollutants by using the above step E3, but the oxidant PMS is not added to test its removal effect on ranitidine; the other control group is to only use the oxidant PMS in the above steps, without adding catalysts such as carbonized Co-MOF powder or carbonized Co-MOF sandwich structure confined catalytic membrane to test its removal effect on ranitidine.

[0096] It can be seen from Figure 8 that during the stable catalytic process, the carbonized Co-MOF sandwich structure confined catalytic membrane that activates PMS can achieve a degradation rate of ranitidine of about 95% in 5 min and almost 100% in 35 min. The heterogeneous system of the carbonized Co-MOF powder can achieve a degradation rate of ranitidine of about 90% in 5 min, and the degradation rate of ranitidine has been maintained at about 96% after 20 min. It can be seen from this that further processing the carbonized Co-MOF powder into a carbonized Co-MOF sandwich structure confined catalytic membrane can further improve the degradation rate and effect on new pollutants. In addition, when the carbonized Co-MOF sandwich structure confined catalytic membrane does not add the oxidant PMS, the degradation rate of ranitidine can reach about 40% after 5 min due to the adsorption of the membrane. However, as time goes by, the removal of ranitidine cannot be achieved, and its removal rate is almost 0, proving that the adsorption of the membrane can be ignored. When only the oxidant PMS is used, the self-degradation in 60 min is about 40%, proving that the degradation effect of the oxidant on the pollutant is very limited in the absence of a catalyst. Therefore, it can be seen that the carbonized Co-MOF powder obtained in step S5 and the carbonized Co-MOF sandwich structure confined catalytic membrane obtained in step S8 have very good activation effects on PMS, and the confined catalytic membrane shows a faster degradation effect than the heterogeneous system.

[0097] As Figure 9a and Figure 9bAs shown, it is a comparison schematic diagram of the removal effects of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS and the carbonized Co-MOF loaded membrane / PMS on ranitidine. Among them, for the test of the removal effect of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS on ranitidine, the carbonized Co-MOF sandwich structure confined catalytic membrane obtained by the above-mentioned step S8 is used to perform step E3 to test the residual concentration and degradation rate of ranitidine; for the test of the removal effect of the carbonized Co-MOF loaded membrane / PMS on ranitidine, the carbonized Co-MO loaded membrane obtained by the above-mentioned step S7 is used to perform step E2 to test the residual concentration and degradation rate of ranitidine.

[0098] From Figure 9a the comparison of the degradation performance of ranitidine between the carbonized Co-MOF loaded membrane / PMS and the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS in it, it can be seen that during the stable catalytic process, the carbonized Co-MOF sandwich structure confined catalytic membrane that activates PMS can achieve a degradation rate of ranitidine of about 95% in 5 min, and can achieve a degradation rate of ranitidine of almost 100% in 35 min; while the carbonized Co-MOF loaded membrane that activates PMS can achieve a degradation rate of ranitidine of about 90% in 20 min, and can also achieve a degradation rate of ranitidine close to 100% in 40 min. From Figure 9b the results of the kinetic reaction constants of ranitidine between the carbonized Co-MOF loaded membrane / PMS and the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS in it, it can be seen that the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS has a higher degradation rate, and its first-order reaction rate constant (k) is twice that of the carbonized Co-MOF loaded membrane / PMS. Among them, the first-order reaction rate constant k of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS is 0.2493 min -1 , and the first-order reaction rate constant k of the carbonized Co-MOF loaded membrane / PMS is 0.1200 min -1 . Through the above comparison, it can be seen that the rich confined space in the sandwich structure confined catalytic membrane greatly enhances the efficiency of the catalytic reaction, that is, the advantage of the configuration can improve the degradation performance of the membrane.

[0099] In actual water bodies, due to the high proportion of natural organic matter (NOM) (generally, accounting for 50% - 90% of the organic matter content in water) and its occurrence characteristics, it will seriously affect the design and operation of water treatment processes. Therefore, the removal effects of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS and the carbonized Co-MOF loaded membrane / PMS on ranitidine under the influence of humic acid are further tested to simulate the actual use conditions. As Figure 10As shown, it is a comparative schematic diagram of the removal effects of ranitidine by the carbonized Co-MOF sandwich-structured confined catalytic membrane / PMS and the carbonized Co-MOF supported membrane / PMS under the influence of humic acid. Among them, the test of the removal effect of ranitidine by the carbonized Co-MOF sandwich-structured confined catalytic membrane / PMS was carried out by adding humic acid to the ranitidine solution when the carbonized Co-MOF sandwich-structured confined catalytic membrane obtained by the above step S8 was used to perform step E3, so as to test the degradation ability of the carbonized Co-MOF sandwich-structured confined catalytic membrane / PMS to ranitidine in the presence of macromolecular pollutants; the test of the removal effect of ranitidine by the carbonized Co-MOF supported membrane / PMS was carried out by adding humic acid to the ranitidine solution when the carbonized Co-MO supported membrane obtained by the above step S7 was used to perform step E2, so as to test the degradation ability of the carbonized Co-MOF supported membrane / PMS to ranitidine in the presence of macromolecular pollutants.

[0100] As can be seen from Figure 10 it, under the influence of humic acid, the degradation performance of both the carbonized Co-MOF supported membrane / PMS and the carbonized Co-MOF sandwich-structured confined catalytic membrane / PMS to ranitidine decreased slightly. However, even under the influence of humic acid during the stable catalytic process, the carbonized Co-MOF sandwich-structured confined catalytic membrane that activates PMS can still achieve a degradation rate of ranitidine of about 95% in 15 min and a degradation rate of ranitidine of about 97% in 25 min; while the carbonized Co-MOF supported membrane that activates PMS, under the influence of humic acid during the stable catalytic process, can achieve a degradation rate of ranitidine of about 80% in 5 min and a stable degradation rate of ranitidine of about 85% after 30 min. Therefore, it can be seen that humic acid has a certain impact on the removal of ranitidine by the carbonized Co-MOF supported membrane / PMS, while it has little impact on the removal of ranitidine by the carbonized Co-MOF sandwich-structured confined catalytic membrane / PMS. Moreover, after the experimental test, obvious yellow humic acid residues can also be seen on the surface of the carbonized Co-MOF sandwich-structured confined catalytic membrane, indicating that the sandwich-structured confined catalytic membrane can indeed isolate macromolecular pollutants.

[0101] Furthermore, to verify the universality of the carbonized Co-MOF sandwich-structured confined catalytic membrane prepared in the above specific embodiment for pollutant degradation, methyl orange, rhodamine B and methylene blue were selected to represent dyes (Dyes), bisphenol A was selected to represent endocrine disrupting chemicals (EDCs), and oxytetracycline, sulfamethoxazole and carbamazepine were selected to represent emerging pollutants (PPCPs). The carbonized Co-MOF sandwich-structured confined catalytic membrane was further tested under the conditions in the above step E3, and the results are asFigure 11 as shown in Figure 11 It can be seen that the degradation rate of the carbonized Co-MOF sandwich-structured confined catalytic membrane for dyes (methyl orange, rhodamine B, and methylene blue) can reach over 98%, for EDCs (bisphenol A) it can achieve a degradation rate of 94%, and for PPCPs, the degradation rates are 90.5% (oxytetracycline), 77.1% (sulfamethoxazole), and 85.7% (carbamazepine) respectively, which confirms the excellent performance and broad applicability of the carbonized Co-MOF sandwich-structured confined catalytic membrane.

[0102] such as Figure 12 shown, is a schematic diagram comparing the degradation performance of the carbonized Co-MOF sandwich-structured confined catalytic membrane with different loadings for ranitidine after activating PMS, which includes the tests of the removal effect of the carbonized Co-MOF sandwich-structured confined catalytic membrane / PMS with loadings of 0.1 mg / cm 2 , 0.25 mg / cm 2 , 0.5 mg / cm 2 , 1 mg / cm 2 on ranitidine. The preparation steps of each carbonized Co-MOF sandwich-structured confined catalytic membrane are the same as the above steps S1 - S8, only different concentrations of carbonized Co-MOF suspension are configured in step S6 to obtain corresponding different loadings in step S7, and the test steps are the same as the above step E3.

[0103] It can be seen from Figure 12 that during the stable catalytic process, the carbonized Co-MOF sandwich-structured confined catalytic membrane with a PMS activation loading of 0.1 mg / cm 2 can achieve a degradation rate of ranitidine of about 96% in 15 min and almost 100% in 35 min; the carbonized Co-MOF sandwich-structured confined catalytic membranes with PMS activation loadings of 0.25 mg / cm 2 and 0.5 mg / cm 2 can both achieve a degradation rate of ranitidine of about 95% in 15 min and also almost 100% in 35 min; the carbonized Co-MOF sandwich-structured confined catalytic membrane with a PMS activation loading of 1 mg / cm 2 can achieve a degradation rate of ranitidine of about 85% in 22 min and a degradation rate of ranitidine close to 96% in 52 min. It can be seen from the above results that for the carbonized Co-MOF sandwich-structured confined catalytic membrane, loadings in the range of 0.1 mg / cm 2 ~1.0 mg / cm 2 can all achieve good removal effects on ranitidine, especially when the loading is 0.1 mg / cm 2~0.5 mg / cm 2 The effect is better when it is in this range. If the loading amount is lower than 0.1 mg / cm 2 it will cause the catalytic membrane to be unstable; if the loading amount is higher than 1 mg / cm 2 during the process of pressing the membrane, some pores may be randomly compacted and blocked, resulting in a thicker membrane layer. In the same vertical space, when the upper part is blocked, the volume of water flow in the lower part cannot enter, and when the lower part is blocked, the volume of water flow in the upper part cannot pass through either. Therefore, when the effects of the two parts are superimposed, there may be a lot of ineffective volume in the membrane, which will further cause the catalyst to be unable to contact the pollutants and PMS, resulting in a significant decrease in the number of active sites and a significant decrease in the degradation rate of new pollutants. Therefore, in the present invention, the catalyst loading amount of the carbonized Co-MOF sandwich structure confined catalytic membrane is determined to be 0.1 mg / cm 2 ~1.0 mg / cm 2 , and the preferred range is 0.1 mg / cm 2 ~0.5 mg / cm 2 .

[0104] In summary, compared with the prior art, the carbonized Co-MOF powder and the carbonized Co-MOF sandwich structure confined catalytic membrane prepared in the embodiments of the present invention have the following significant advantages:

[0105] (1) The materials of the present invention are novel, with stable structural properties, and can still maintain a complete crystal structure after being soaked in various solvents for 24 hours.

[0106] (2) The present invention combines the advanced oxidation process with the membrane separation process, integrating multiple functions such as filtration, catalysis, and adsorption; it is efficient, convenient, and thorough in degrading new pollutants, reducing the problem of secondary disposal of new pollutant concentrates.

[0107] (3) The present invention provides a new way to construct a confined space, and the sandwich configuration can compress the catalyst into the interlayer to form a sufficient confined space; the increase in the confined space effectively improves the degradation efficiency of the sandwich structure confined catalytic membrane, and the removal rate of ranitidine reaches 100%.

[0108] (4) The sandwich configuration described in the present invention can play an effective isolation role; on the one hand, it isolates large particle pollutants, avoiding the adhesion of pollutants to the surface of the catalytic material and causing a decrease in the number of active sites, thereby affecting the catalytic effect; on the other hand, it isolates the direct scouring of the catalytic material by water flow, avoiding the shedding of the catalyst from the membrane surface, resulting in a decrease in performance and the leaching of metals.

[0109] (5)Even when facing water bodies containing organic substances or actual water bodies, the membrane with the "membrane-catalytic material-membrane" sandwich structure of the present invention can be directly filtered without pretreatment. The first membrane can intercept macromolecules and particulate matters, and the target pollutants enter the second layer, i.e., the catalytic material layer, for degradation. The third membrane then intercepts them, and the effluent is cleaner.

[0110] (6)The present invention has fabricated a carbonized Co-MOF catalytic material with stable structure, and further constructed a confined space through film pressing, which improves various performances and is simple and convenient to assemble.

[0111] (7)The preparation method of the sandwich structure confined catalytic membrane of the present invention has certain expandability; the interlayer material or the upper and lower base membranes can be changed to meet the requirements of different scenarios, or it can be changed into a three-layer or multi-layer multifunctional membrane according to different actual needs, so that one membrane can meet multiple needs.

[0112] The background part of the present invention may include background information about the problems or environments of the present invention, rather than the prior art described by others. Therefore, the content included in the background art section is not an admission by the applicant of the prior art.

[0113] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, they can make several substitutions or modifications to these described embodiments, and these substitution or modification methods should all be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of reference terms such as "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the scope defined by the appended claims.

Claims

1. A preparation method of a carbonized Co-MOF sandwich structure confined catalytic membrane, characterized in that Comprising the following steps: A1: Dissolve cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid in N,N-dimethylformamide to prepare a first solution; wherein, the cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid are dissolved in N,N-dimethylformamide according to a molar ratio of 1:(0.5 - 2); A2: After the first solution is completely dissolved, perform a hydrothermal reaction on the first solution, wherein the conditions of the hydrothermal reaction are 60°C - 100°C; A3: Let the product obtained in step A2 stand and age at room temperature for 24h - 72h, and then perform centrifugal washing to obtain a precipitate; A4: Dry and grind the precipitate to obtain Co-MOF powder; A5: Heat and carbonize the Co-MOF powder and then grind it to obtain carbonized Co-MOF powder, wherein the temperature of heat and carbonization is 400°C - 600°C; B1: Dissolve the carbonized Co-MOF powder in pure water to obtain a suspension; B2: Provide a first polymer membrane, filter the suspension onto the first polymer membrane, and dry it to obtain a carbonized Co-MOF supported membrane, wherein the loading amount of the carbonized Co-MOF powder in the obtained carbonized Co-MOF supported membrane is 0.1 mg / cm 2 ~1.0 mg / cm 2 , the first polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyethersulfone, polysulfone, and cellulose acetate, and the average pore size of the first polymer membrane is 0.22 μm to 0.45 μm; C1: Provide a second polymer membrane, and cover the second polymer membrane on the side of the carbonized Co-MOF supported membrane for filtering the suspension, and obtain a carbonized Co-MOF sandwich structure confined catalytic membrane after pressing; wherein, the second polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyethersulfone, polysulfone, and cellulose acetate, and the average pore size of the second polymer membrane is 0.22μm - 0.45μm; the pressure during the pressing process is 5MPa - 20MPa, and the time is 1min - 5min.

2. The preparation method of the carbonized Co-MOF sandwich structure-confined catalytic membrane according to claim 1, characterized in that, The concentration of the cobalt salt in the first solution is 0.01mol / L - 0.02mol / L.

3. The preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane according to claim 1, wherein, In step A2, the time of the hydrothermal reaction is 24h - 72h; in step A3, the product obtained after aging is washed at least three times with N,N-dimethylformamide and pure water under centrifugal conditions, wherein the centrifugal rate during centrifugation is 8000r / min - 10000r / min, and the centrifugal time for one wash is 5min - 10min; in step A4, the temperature for drying the precipitate is 40°C - 70°C, and the time is 8h - 24h; in step A5, it includes adding the Co-MOF powder into a furnace body for heat and carbonization, wherein the heating rate of the furnace body is 5°C / min - 10°C / min, and the time of heat and carbonization is 1h - 2h.

4. The preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane according to claim 1, characterized in that, In step B1, it includes dissolving the carbonized Co-MOF powder in pure water to obtain a dispersion with a concentration of 6.3mg / L - 63mg / L, and then performing ultrasonic treatment on the dispersion to obtain a uniformly dispersed suspension.

5. A carbonized Co-MOF sandwich structure confined catalytic membrane, characterized in that, Prepared by using the preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane according to any one of claims 1 to 4.

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