Carbonized Co-MOF powder, supported membrane, sandwich structure confinement catalytic membrane and preparation method

Abstract

The invention discloses carbonized Co-MOF powder, a supported membrane, a sandwich structure confinement catalytic membrane and preparation methods of the carbonized Co-MOF powder, the supported membrane and the sandwich structure confinement catalytic membrane, and the preparation method of the carbonized Co-MOF powder comprises the following steps: A1, dissolving cobalt salt and 4-(1H-tetrazole-5-yl) benzoic acid in N, N-dimethylformamide to prepare a first solution; a2, after the first solution is completely dissolved, carrying out a hydrothermal reaction on the first solution; a3, standing and aging the product obtained in the step A2, and then carrying out centrifugal washing to obtain a precipitate; a4, the sediment is dried and ground, and Co-MOF powder is obtained; and A5, the Co-MOF powder is heated, carbonized and then ground, and carbonized Co-MOF powder is obtained. The invention provides construction of a new confinement space, and the degradation efficiency and the removal rate of new pollutants are effectively improved.

Description

Technical Field

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

[0003] Advanced oxidation technologies (AOPs) have attracted widespread attention due to their advantages such as high efficiency, thorough treatment and easy operation. Persulfate-based advanced oxidation processes (SR-AOPs) have been more widely favored due to their higher redox potential, longer half-life and stronger pH adaptability. However, traditional homogeneous SR-AOPs have many disadvantages, such as difficulty in catalyst recovery, severe metal ion leaching and short life of active species.

[0004] 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. Not only that, the membrane also has a retention effect, thereby further improving the degradation effect of pollutants. In order to further improve the catalytic performance of the membrane, membrane-based nano-confined catalytic technology has gradually been proposed. Nano-confinement means that when the reaction is confined to a nanoscale space, the physical and chemical properties of the catalyst will change significantly, mainly including electronic morphology, mass transfer path, and phase behavior. The confined space shortens the mass transfer path, the active species are not easily deactivated, and the interaction between pollutants and active species is significantly enhanced. However, the construction of confined space is a major challenge for high-performance catalytic membranes.

[0005] The disclosure of the above background technology content is only used to assist in understanding the concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a carbonized Co-MOF powder, a loaded membrane, a sandwich structured confined catalytic membrane and a preparation method thereof, which provides a new confined space construction and effectively improves the degradation efficiency and removal rate of new pollutants.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention discloses a method for preparing carbonized Co-MOF powder, comprising the following steps: A1: dissolving cobalt salt and 4-(1H-tetrazolyl-5-yl)benzoic acid in N,N-dimethylformamide to prepare a first solution; A2: After the first solution is completely dissolved, subjecting the first solution to a hydrothermal reaction; A3: The product obtained in step A2 is allowed to stand for aging and then centrifuged to wash to obtain a precipitate; A4: drying and grinding the precipitate to obtain Co-MOF powder; A5: The Co-MOF powder is heated and carbonized and then ground to obtain carbonized Co-MOF powder.

[0008] Preferably, the cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid in step A1 are dissolved in N,N-dimethylformamide in a molar ratio of 1:(0.5-2).

[0009] Preferably, the concentration of the cobalt salt in the first solution is 0.01 mol / L to 0.02 mol / L.

[0010] Preferably, the hydrothermal reaction in step A2 is carried out at a temperature of 60° C. to 100° C. and for a time of 24 h to 72 h.

[0011] Preferably, step A3 comprises allowing the product obtained in step A2 to stand and age at room temperature for 24 h to 72 h, and washing the aged product at least three times with N,N-dimethylformamide and pure water under centrifugal conditions, wherein the centrifugal rate during the centrifugation process is 8000 r / min to 10000 r / min, and the centrifugation time for one wash is 5 min to 10 min.

[0012] 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.

[0013] Preferably, step A5 includes adding the Co-MOF powder into a furnace body for heating and carbonization, wherein the heating rate of the furnace body is 5°C / min~10°C / min, the heating and carbonization temperature is 400°C~600°C, and the time is 1h~2h.

[0014] In a second aspect, the present invention discloses a carbonized Co-MOF powder, which is prepared by the method for preparing the carbonized Co-MOF powder described in the first aspect.

[0015] In a third aspect, the present invention discloses a method for preparing a carbonized Co-MOF supported membrane, comprising the following steps: B1: dissolving the carbonized Co-MOF powder described in the second aspect in pure water to obtain a suspension; B2: providing a first polymer membrane, filtering the suspension onto the first polymer membrane, and drying the suspension to obtain a carbonized Co-MOF loaded membrane.

[0016] Preferably, step B1 comprises dissolving the carbonized Co-MOF powder described in the second aspect in pure water to obtain a dispersion having a concentration of 6.3 mg / L to 63 mg / L, and then subjecting the dispersion to ultrasonic treatment to obtain a uniformly dispersed suspension.

[0017] Preferably, the ultrasonic dispersion power during the ultrasonic treatment in step B1 is 50W to 2000W, and the time is 20min to 60min.

[0018] Preferably, the loading amount of the carbonized Co-MOF powder of the carbonized Co-MOF supported film obtained in step B2 is 0.1 mg / cm 2 ~1.0mg / cm 2 .

[0019] Preferably, the first polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyether sulfone, polysulfone, and cellulose acetate, and the average pore size of the first polymer membrane is 0.22 μm to 0.45 μm.

[0020] In a fourth aspect, the present invention discloses a carbonized Co-MOF supported membrane, which is prepared by the method for preparing the carbonized Co-MOF supported membrane described in the third aspect.

[0021] In the fifth aspect, the present invention discloses a method for preparing a carbonized Co-MOF sandwich structure confined catalytic membrane, comprising the following steps: providing a second polymer membrane, and covering the second polymer membrane on one side of the carbonized Co-MOF loaded membrane described in the fourth aspect for filtering the suspension, and obtaining the carbonized Co-MOF sandwich structure confined catalytic membrane after pressing.

[0022] Preferably, the second polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyether sulfone, polysulfone, and cellulose acetate, and the average pore size of the second polymer membrane is 0.22 μm to 0.45 μm.

[0023] Preferably, the pressure during the pressing process is 5 MPa to 20 MPa, and the time is 1 min to 5 min.

[0024] In a sixth aspect, the present invention discloses a carbonized Co-MOF sandwich structure confined catalytic membrane, which is prepared by the preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane described in the fifth aspect.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: the carbonized Co-MOF powder, supported membrane, sandwich structure confined catalytic membrane and preparation method thereof proposed in the present invention obtain a structurally stable carbonized Co-MOF catalytic material by solvent thermal reaction, room temperature aging and high temperature carbonization, and achieve a high degradation efficiency and removal rate for new pollutants. Furthermore, the structurally stable carbonized Co-MOF catalytic material is supported on a polymer membrane, and the obtained carbonized Co-MOF supported membrane can also achieve a high degradation efficiency and removal rate for new pollutants. Furthermore, a carbonized Co-MOF sandwich structure confined catalytic membrane was designed by changing the configuration, forming a sandwich structure of "membrane-catalytic material-membrane". First, the problem of easy detachment of the catalytic material was solved. Second, sufficient confined space was formed. The increase in confined space further effectively improved the degradation efficiency and removal rate of new pollutants, and various types of pollutants could be well removed. Third, large particles of pollutants could be isolated to prevent pollutants from adhering to the surface of the catalytic material and causing a decrease in the number of active sites, effectively preventing membrane pollution from affecting the catalytic effect. Fourth, the isolated catalytic material was directly washed by water flow first to prevent the catalyst from falling off the membrane surface, causing performance degradation and metal leaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the method for preparing carbonized Co-MOF powder disclosed in Example 1 of the present invention; Figure 2 is a SEM image of the morphology of the carbonized Co-MOF powder of Example 2 of the present invention; Figure 3 is a flow chart of a method for preparing a carbonized Co-MOF supported membrane disclosed in Example 3 of the present invention; Figure 4 It is a flow chart of the preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane disclosed in Example 5 of the present invention; Figure 5 This is a surface morphology SEM image of the carbonized Co-MOF sandwich structure confined catalytic membrane of Example 6 of the present invention; Figure 6a The loading is 0.1 mg / cm 2 The local cross-sectional morphology SEM image of the carbonized Co-MOF sandwich structure confined catalytic membrane; Figure 6b The loading is 0.1 mg / cm 2 The overall cross-sectional morphology SEM image of the carbonized Co-MOF sandwich structure confined catalytic membrane; Figure 7a The loading is 0.5 mg / cm 2 The cross-sectional SEM image of the carbonized Co-MOF sandwich structure confined catalytic membrane; Figure 7b The loading amount is 0.5 mg / cm 2 EDS image of the cross-sectional morphology of the carbonized Co-MOF sandwich structure confined catalytic membrane; Figure 8 It is a schematic diagram comparing the removal effects of 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; Figure 9a The figure shows the comparison of the degradation performance of carbonized Co-MOF supported membrane / PMS and carbonized Co-MOF sandwich structure confined catalytic membrane / PMS on ranitidine; Figure 9b Schematic diagram of the comparison of the kinetic reaction constants of ranitidine between carbonized Co-MOF supported membrane / PMS and carbonized Co-MOF sandwich structure confined catalytic membrane / PMS; Fig.10 It is a schematic diagram comparing the removal effects of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS and carbonized Co-MOF supported membrane / PMS under the influence of humic acid; Fig.11 This is a schematic diagram of the degradation effect of carbonized Co-MOF sandwich structure confined catalytic membrane on various new pollutants in water bodies; Fig.12 This is a schematic diagram comparing the degradation performance of ranitidine after PMS activation by carbonized Co-MOF sandwich structure confined catalytic membrane with different loading amounts. DETAILED DESCRIPTION

[0027] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention.

[0028] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and circuit / signal communication.

[0029] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0031] Metal organic frameworks (MOFs) as catalytic materials have the advantages of adjustable structure, unique properties, large specific surface area, and rich pores, making them an excellent choice for constructing nano-confined spaces. The flexibility of MOFs structure is conducive to the construction of confined spaces, and the large specific surface area provides abundant active sites, alleviating the problem of short life span of free radicals.

[0032] 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 prone to attack the coordination bonds of MOFs, causing structural damage. Therefore, although the MOFs in many studies have excellent catalytic performance, their stability is very poor. Basically, the catalytic effect has only been explored a few times or at most a few hours, and there is no long-term operation effect. Therefore, for the application of AOPs, how to improve the stability of MOFs is a difficult problem that needs to be solved urgently. Not only that, for catalytic membranes, the catalytic materials loaded on the membranes are also easy to detach from the membrane substrate under the scouring of water flow, resulting in a decrease in catalytic performance and metal leaching, which leads to higher environmental risks.

[0033] In general, the instability of MOFs materials, the shedding of catalytic materials and the construction of confined spaces are important factors that limit the high performance of MOF catalytic membranes. Therefore, the invention of catalytic materials and the improvement of membrane configuration will increase the service life of catalytic membranes, improve the reaction performance of catalytic membranes and reduce environmental safety risks.

[0034] In order to solve the problem of MOFs being unstable in the AOPs system, the present invention obtains a structurally stable carbonized Co-MOF catalytic material by solvent thermal reaction, room temperature aging and high temperature carbonization. At the same time, in order to realize the construction of a confined space and solve the problem of easy detachment of the catalytic material, a tablet press is used to sandwich the obtained Co-MOF catalytic material between two layers of polymer base membranes to form a "membrane-catalytic material-membrane" sandwich structure. Such a structure can achieve efficient removal of new pollutants in water bodies at a lower catalyst dosage.

[0035] like Figure 1 As shown, Embodiment 1 of the present invention discloses a method for preparing carbonized Co-MOF powder, comprising the following steps: A1: dissolving cobalt salt and 4-(1H-tetrazolyl-5-yl)benzoic acid in N,N-dimethylformamide to prepare a first solution; The cobalt salt and 4-(1H-tetrazolyl-5-yl)benzoic acid are dissolved in N,N-dimethylformamide at 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, for example, cobalt nitrate.

[0036] A2: After the first solution is completely dissolved, performing a hydrothermal reaction on the first solution; Specifically, the first solution is ultrasonicated for a period of time until it is completely dissolved, and then placed in an oven for hydrothermal reaction. The hydrothermal reaction conditions are 60° C. to 100° C. and the time is 24 h to 72 h.

[0037] A3: The product obtained in step A2 is allowed to stand for aging and then centrifuged to wash to obtain a precipitate; Specifically, the product obtained in step A2 is aged at room temperature for 24 h to 72 h, and the product obtained after aging is washed at least three times with N,N-dimethylformamide and pure water under centrifugal conditions to remove excess impurities, wherein the centrifugal rate during the centrifugation process is 8000 r / min to 10000 r / min, and the centrifugation time for one wash is 5 min to 10 min.

[0038] A4: Drying and grinding the precipitate to obtain Co-MOF powder; Specifically, the precipitate is placed in an oven to dry for a period of time, and the product is ground using a mortar to obtain a brown powder Co-MOF; wherein the temperature of the oven is 40°C~70°C, and the drying time is 8h~24h.

[0039] A5: The Co-MOF powder is heated and carbonized and then ground to obtain carbonized Co-MOF powder.

[0040] Specifically, the Co-MOF powder is placed in a crucible, heated at high temperature in a tube furnace for a certain period of time, and the product is ground in a mortar to obtain a black powder carbonized Co-MOF. The heating rate of the tube furnace is 5°C / min~10°C / min, the heating carbonization temperature is 400°C~600°C, and the time is 1h~2h.

[0041] Embodiment 2 of the present invention discloses a carbonized Co-MOF powder, which is prepared by the preparation method of the carbonized Co-MOF powder in Embodiment 1. Figure 2 Shown is the SEM (scanning electron microscope) image of the carbonized Co-MOF powder of this embodiment. From the SEM image of the Co-MOF powder, it can be seen that the carbonized Co-MOF powder prepared by the preparation method of the carbonized Co-MOF powder in Example 1 of the present invention contains a plurality of block structures composed of small fragments, which provides good conditions for the subsequent formation of a sandwich structure confined catalytic membrane through vacuum filtration to construct a confined space.

[0042] The carbonized Co-MOF powder can be used to remove new pollutants. The specific steps are as follows: E1: Add carbonized Co-MOF powder and PMS into a beaker containing ranitidine aqueous solution and place it on a magnetic stirrer for reaction. At a certain time interval, a certain amount of degradation solution is drawn through a syringe and filtered using a PVDF membrane. The catalytic degradation efficiency is characterized by the filtrate. The absorbance of the filtrate is detected at a wavelength of 314nm using a UV-visible spectrophotometer, and the residual concentration and degradation rate of ranitidine are calculated using a standard working curve. Among them, the ranitidine concentration is preferably 5mg / L~10mg / L; based on the principle of good degradation effect and small PMS dosage, the PMS concentration is 0.1mmol / L~0.2mmol / L; the concentration of carbonized Co-MOF is 40mg / L~50mg / L, the speed of the magnetic stirrer is 200r / min~300r / min; the volume of the absorbed degradation solution is 1mL~2mL; the pore size of the PVDF membrane is 0.22μm~0.45μm.

[0043] like Figure 3 As shown, Embodiment 3 of the present invention discloses a method for preparing a carbonized Co-MOF supported membrane, comprising the following steps: B1: dissolving the carbonized Co-MOF powder in Example 2 in pure water to obtain a suspension; Specifically, the carbonized Co-MOF powder in Example 2 is dissolved in pure water, and ultrasonic treatment is performed for a certain period of time to obtain a uniformly dispersed suspension, wherein the carbonized Co-MOF powder is dissolved in pure water to obtain a dispersion with a concentration of 6.3 mg / L~63 mg / L, and then the dispersion is ultrasonically treated to obtain a uniformly dispersed suspension, wherein the ultrasonic dispersion power during the ultrasonic treatment process is 50 W~2000 W, and the time is 20 min~60 min, preferably 30 min.

[0044] B2: providing a first polymer membrane, filtering the suspension onto the first polymer membrane, and drying the membrane to obtain a carbonized Co-MOF loaded membrane.

[0045] Specifically, the suspension is filtered onto the first polymer membrane by vacuum filtration and placed in an oven to dry to obtain a carbonized Co-MOF loaded membrane. The first polymer membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polyether sulfone, polysulfone, and cellulose acetate, and the average pore size of the first polymer membrane is 0.22μm~0.45μm. The temperature of the oven is 40℃~70℃, and the drying time is 1h~2h. The loading amount of carbonized Co-MOF powder of the carbonized Co-MOF loaded membrane is 0.1mg / cm 2 ~1.0mg / cm 2 In a more preferred embodiment, the loading amount of the carbonized Co-MOF powder of the carbonized Co-MOF supported film is 0.1 mg / cm 2 ~0.5mg / cm 2 ; The loading amount of carbonized Co-MOF powder is 0.1 mg / cm 2 Specifically, for example, at 12.56 cm 2 100 mL to 200 mL of the suspension is filtered onto the first polymer membrane by vacuum filtration.

[0046] Embodiment 4 of the present invention discloses a carbonized Co-MOF supported membrane, which is prepared by the preparation method of the carbonized Co-MOF supported membrane of Embodiment 3.

[0047] The carbonized Co-MOF loaded membrane can be used to remove new pollutants under gravity conditions. The specific steps are as follows: E2: The carbonized Co-MOF loaded membrane is placed in a suction filtration device, the target pollutant is ranitidine, and the oxidant is permonosulfate (PMS). Under gravity, the ranitidine aqueous solution with PMS added is filtered, and the filtrate is sampled at a certain time interval to characterize the catalytic degradation efficiency. The absorbance of the filtrate is detected at a wavelength of 314nm using a UV-visible spectrophotometer, and the residual concentration and degradation rate of ranitidine are calculated using a standard working curve. Among them, the ranitidine concentration is preferably 5mg / L~10mg / L; based on the principle of good degradation effect and small PMS dosage, the PMS concentration is 0.1mmol / L~0.2mmol / L; the gravity flow pressure (characterized by the liquid injection head height) is 10cm~15cm. Specifically, for example, the ranitidine concentration is 5mg / L, the PMS concentration is 0.2mmol / L, and the gravity flow pressure (characterized by the liquid injection head height) is 12cm.

[0048] like Figure 4 As shown, Example 5 of the present invention discloses a method for preparing a carbonized Co-MOF sandwich structure confined catalytic film, comprising the following steps: C1: providing a second polymer membrane, and covering the second polymer membrane on one side of the filtrated suspension of the carbonized Co-MOF loaded membrane, and obtaining a carbonized Co-MOF sandwich structure confined catalytic membrane after pressing.

[0049] Specifically, the carbonized Co-MOF loaded membrane is placed in a tablet press, and a second polymer membrane is covered thereon, and pressure is applied for a certain period of 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, polyether sulfone, polysulfone, and cellulose acetate, and the average pore size of the second polymer membrane is 0.22μm~0.45μm. The tablet press pressure is 5MPa~20MPa, and the film pressing time is 1min~5min.

[0050] Embodiment 6 of the present invention discloses a carbonized Co-MOF sandwich structure confined catalytic membrane, which is prepared by the preparation method of the carbonized Co-MOF sandwich structure confined catalytic membrane of embodiment 5. Figure 5 As shown, it is the surface morphology SEM image of the carbonized Co-MOF sandwich structure confined catalytic film. Figure 6a and Figure 6b The loading is shown as 0.1 mg / cm 2 The cross-sectional morphology SEM image of the carbonized Co-MOF sandwich structure confined catalytic membrane is shown in Figure 2. Figure 7a The loading is shown as 0.5 mg / cm 2 The cross-sectional morphology SEM image of the carbonized Co-MOF sandwich structure confined catalytic membrane is shown in Figure 2. Figure 7b The loading is shown as 0.5 mg / cm2 EDS (energy dispersive X-ray spectroscopy) of the cross-sectional morphology of the carbonized Co-MOF sandwich structure confined catalytic film. Figure 5 It can be seen that the surface of the carbonized Co-MOF sandwich structure confined catalytic membrane is uniform and flat, some pores are compacted but most are still retained; Figure 6a For a local graph, Figure 6a It can be seen that the carbonized Co-MOF catalytic material is embedded in the interlayer; Figure 6b The whole cross-section of the membrane is shown in Figure 2. Figure 6b It can be seen that the thickness has changed to 11.2μm, which is reduced to 50% of the original thickness. The upper and lower layers are cross-linked and gradually integrated. For more intuitive observation, when the loading amount is increased to 0.5mg / cm 2 When, from Figure 7a The interlayer boundary can be clearly seen. Figure 7b The EDS spectrum of the film cross section shown also shows that the material is uniformly sandwiched in the middle, proving the successful formation of the sandwich structure.

[0051] The carbonized Co-MOF sandwich structure confined catalytic membrane can be used to remove new pollutants. The specific steps are as follows: E3: The carbonized Co-MOF sandwich structure confined catalytic membrane is placed in a filtration device, the target pollutant is ranitidine, and the oxidant is permonosulfate (PMS). Under a certain pressure, the ranitidine aqueous solution with PMS added is filtered, and the filtrate is sampled at a certain time interval to characterize the catalytic degradation efficiency. The absorbance of the filtrate is detected at a wavelength of 314nm using a UV-visible spectrophotometer, and the residual concentration and degradation rate of ranitidine are calculated using a standard working curve. Among them, the ranitidine concentration is preferably 5mg / L~10mg / L; based on the principle of good degradation effect and small PMS dosage, the PMS concentration is 0.1mmol / L~0.2mmol / L; the applied pressure is 0.8MPa~1.0MPa. Specifically, for example, the ranitidine concentration is 5mg / L, the PMS concentration is 0.2mmol / L, and the applied pressure is 0.8MPa.

[0052] Among them, in order to ensure a sufficient flux to achieve normal operation, the carbonized Co-MOF loaded membrane in the embodiment of the present invention can directly use the self-gravity to remove new pollutants, while the carbonized Co-MOF sandwich structure confined catalytic membrane is used to apply a certain pressure to remove new pollutants.

[0053] The carbonized Co-MOF powder and its preparation method, the carbonized Co-MOF supported membrane and its preparation method, the carbonized Co-MOF sandwich structure confined catalytic membrane and its preparation method in the above-mentioned embodiments are further described in detail below with specific examples.

[0054] The preparation method of the carbonized Co-MOF powder, the carbonized Co-MOF supported film and the carbonized Co-MOF sandwich structure confined catalytic film in this specific embodiment includes: S1: Weigh 0.1 mmol of cobalt nitrate and 0.2 mmol of 4-(1H-tetrazolyl-5-yl)benzoic acid into 9 mL of N,N-dimethylformamide solution, dissolve by ultrasonication to obtain a first solution, and place in an oven at 60°C for hydrothermal reaction for 24 h.

[0055] S2: The solution after the hydrothermal reaction was placed at room temperature for aging for 24 hours.

[0056] S3: The aged product was washed three times by high-speed centrifugation with N,N-dimethylformamide and pure water respectively to remove surface impurities.

[0057] S4: The product was placed in an oven at 60°C and dried for 12 h, and the material was ground into powder using a mortar to obtain Co-MOF powder.

[0058] S5: The Co-MOF powder was placed in a tube furnace and heated at 500°C for 2 h, and then the product was ground to obtain carbonized Co-MOF powder.

[0059] S6: The carbonized Co-MOF powder was dispersed in pure water and ultrasonicated for 30 min to obtain a uniformly dispersed carbonized Co-MOF suspension.

[0060] S7: Prepare PVDF substrate and load the carbonized Co-MOF suspension onto the PVDF substrate by vacuum filtration with a loading of 0.1 mg / cm 2 , and dried in an oven at 60 °C to obtain a carbonized Co-MOF loaded membrane.

[0061] S8: Prepare a PVDF base membrane, cover the PVDF base membrane on the surface of the carbonized Co-MOF loaded membrane, and use a tablet press to press the membrane at 10 MPa for 1 min to obtain a carbonized Co-MOF sandwich structure confined catalytic membrane.

[0062] like Figure 8 As shown, it is a comparative schematic diagram of the removal effect of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS, carbonized Co-MOF powder / PMS, carbonized Co-MOF sandwich structure confined catalytic membrane, and PMS, respectively. trepresents the concentration of ranitidine after the reaction, and C0 represents the initial concentration of ranitidine. The test of the removal effect of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS is to use the carbonized Co-MOF sandwich structure confined catalytic membrane obtained in step S8 to perform step E3 to test the residual concentration and degradation rate of ranitidine; the test of the removal effect of ranitidine by carbonized Co-MOF powder / PMS is to use the carbonized Co-MO powder obtained in step S5 to perform step E1 to test the residual concentration and degradation rate of ranitidine. In addition, two groups of comparative examples were added. In one group of comparative examples, the carbonized Co-MOF sandwich structure confined catalytic membrane obtained in step S8 was placed in a filtration device using the above step E3 to degrade new pollutants, but the oxidant PMS was not added thereto, to test its removal effect on ranitidine; in the other group of comparative examples, only the oxidant PMS was used 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.

[0063] from Figure 8 It can be seen that in the stable catalytic process, the carbonized Co-MOF sandwich structure confined catalytic membrane with activated PMS can achieve a degradation rate of about 95% for ranitidine in 5 minutes, and a degradation rate of almost 100% for ranitidine in 35 minutes. The heterogeneous system of carbonized Co-MOF powder can achieve a degradation rate of about 90% for ranitidine in 5 minutes, and the degradation rate of ranitidine remains at about 96% after 20 minutes. It can be seen 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 degradation effect of new pollutants. In addition, without the addition of the oxidant PMS, the carbonized Co-MOF sandwich structure confined catalytic membrane can achieve a degradation rate of about 40% for ranitidine after 5 minutes due to the adsorption of the membrane, but as time goes by, ranitidine cannot be removed, and its removal rate is almost 0, proving that the adsorption of the membrane is negligible. When only the oxidant PMS is used, the self-degradation is about 40% in 60 minutes, which proves that in the absence of a catalyst, the degradation effect of the oxidant alone on pollutants is very limited. Therefore, it can be seen that the carbonized Co-MOF powder obtained in step S5 and the carbonized Co-MOF sandwich structure confined catalytic film obtained in step S8 have very good activation effects on PMS, and the confined catalytic film exhibits a faster degradation effect than the heterogeneous system.

[0064] like Figure 9a and Figure 9bAs shown, it is a comparative schematic diagram of the removal effect of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS and carbonized Co-MOF supported membrane / PMS. Among them, the test of the removal effect of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS is to perform step E3 with the carbonized Co-MOF sandwich structure confined catalytic membrane obtained in step S8 above to test the residual concentration and degradation rate of ranitidine; the test of the removal effect of ranitidine by carbonized Co-MOF supported membrane / PMS is to perform step E2 with the carbonized Co-MO supported membrane obtained in step S7 above to test the residual concentration and degradation rate of ranitidine.

[0065] from Figure 9a From the comparison of the degradation performance of ranitidine by carbonized Co-MOF loaded membrane / PMS and carbonized Co-MOF sandwich structure confined catalytic membrane / PMS, it can be seen that in the stable catalytic process, the carbonized Co-MOF sandwich structure confined catalytic membrane with activated PMS can achieve a degradation rate of about 95% for ranitidine in 5 minutes, and a degradation rate of almost 100% for ranitidine in 35 minutes; while the carbonized Co-MOF loaded membrane with activated PMS can achieve a degradation rate of about 90% for ranitidine in 20 minutes, and a degradation rate of nearly 100% for ranitidine in 40 minutes. Figure 9b The results of the kinetic reaction constants of carbonized Co-MOF loaded membrane / PMS and carbonized Co-MOF sandwich structure confined catalytic membrane / PMS for ranitidine show 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 of the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS is k=0.2493min -1 , the first-order reaction rate constant of carbonized Co-MOF supported membrane / PMS is k=0.1200min -1 From the above comparison, it can be seen that the abundant 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.

[0066] In actual water bodies, the high proportion of natural organic matter (NOM) (generally, 50% to 90% of the organic matter content in water) and its occurrence characteristics will seriously affect the design and operation of water treatment processes. Therefore, the removal effect of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS and carbonized Co-MOF loaded membrane / PMS under the influence of humic acid was further tested to simulate actual use conditions. Fig.10As shown, it is a comparative schematic diagram of the removal effect of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS and carbonized Co-MOF supported membrane / PMS respectively under the influence of humic acid. Among them, the test of the removal effect of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS is to add humic acid to the ranitidine solution when the carbonized Co-MOF sandwich structure confined catalytic membrane obtained in step S8 is performed in step E3 to test the degradation ability of carbonized Co-MOF sandwich structure confined catalytic membrane / PMS to ranitidine in the presence of macromolecular pollutants; the test of the removal effect of ranitidine by carbonized Co-MOF supported membrane / PMS is to add humic acid to the ranitidine solution when the carbonized Co-MO supported membrane obtained in step S7 is performed in step E2 to test the degradation ability of carbonized Co-MOF supported membrane / PMS to ranitidine in the presence of macromolecular pollutants.

[0067] from Fig.10 It can be seen that under the influence of humic acid, the degradation performance of carbonized Co-MOF loaded membrane / PMS and carbonized Co-MOF sandwich structure confined catalytic membrane / PMS on ranitidine is slightly reduced, but the carbonized Co-MOF sandwich structure confined catalytic membrane with activated PMS can still achieve a ranitidine degradation rate of about 95% in 15 minutes and a ranitidine degradation rate of about 97% in 25 minutes even under the influence of humic acid and in the stable catalytic process; and the carbonized Co-MOF loaded membrane with activated PMS can achieve a ranitidine degradation rate of about 80% in 5 minutes under the influence of humic acid and in the stable catalytic process, and the ranitidine degradation rate can be stabilized at about 85% after 30 minutes. Therefore, it can be seen that humic acid has a certain effect on the removal of ranitidine by carbonized Co-MOF loaded membrane / PMS, while it has little effect on the removal of ranitidine by carbonized Co-MOF sandwich structure confined catalytic membrane / PMS. Moreover, after the experimental test, yellow humic acid residues can be clearly seen on the surface of the carbonized Co-MOF sandwich structure confined catalytic membrane, which shows that the sandwich structure confined catalytic membrane can indeed isolate large molecular pollutants.

[0068] To further verify the universality of the carbonized Co-MOF sandwich structure 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 represented endocrine disrupting chemicals (EDCs), oxytetracycline, sulfamethoxazole and carbamazepine represented emerging pollutants (PPCPs), and the carbonized Co-MOF sandwich structure confined catalytic membrane was further tested under the conditions in the above step E3. The results are as follows: Fig.11 As shown. Fig.11 It can be seen that the degradation rate of the carbonized Co-MOF sandwich structure confined catalytic membrane for dyes (methyl orange, rhodamine B and methylene blue) can reach more than 98%, and a degradation rate of 94% can be achieved for EDCs (bisphenol A). For PPCPs, the degradation rates are 90.5% (oxytetracycline), 77.1% (sulfamethoxazole) and 85.7% (carbamazepine), respectively, confirming the excellent performance and broad-spectrum applicability of the carbonized Co-MOF sandwich structure confined catalytic membrane.

[0069] like Fig.12 The figure shows the comparison of the degradation performance of ranitidine after activation of PMS by carbonized Co-MOF sandwich structure confined catalytic membrane with different loading amounts, including the loading amount of 0.1 mg / cm 2 , 0.25mg / cm 2 , 0.5mg / cm 2 , 1mg / cm 2 The removal effect of ranitidine by the carbonized Co-MOF sandwich structure confined catalytic membrane / PMS was tested. The preparation steps of each carbonized Co-MOF sandwich structure confined catalytic membrane were the same as the above steps S1 to S8, except that different concentrations of carbonized Co-MOF suspension were configured in step S6 to obtain corresponding different loading amounts in step S7. The testing steps were the same as the above step E3.

[0070] from Fig.12 It can be seen that in the stable catalytic process, the loading of activated PMS is 0.1 mg / cm 2 The carbonized Co-MOF sandwich structure confined catalytic membrane can achieve a degradation rate of about 96% for ranitidine in 15 minutes, and a degradation rate of almost 100% for ranitidine in 35 minutes; the loading capacity of activated PMS is 0.25 mg / cm 2 , 0.5mg / cm 2 The carbonized Co-MOF sandwich structure confined catalytic membrane can achieve a degradation rate of about 95% for ranitidine in 15 minutes, and a degradation rate of almost 100% for ranitidine in 35 minutes; the loading of activated PMS is 1 mg / cm 2 The carbonized Co-MOF sandwich structure confined catalytic membrane can achieve a degradation rate of about 85% for ranitidine in 22 minutes, and a degradation rate of nearly 96% for ranitidine in 52 minutes. From the above results, it can be seen that the carbonized Co-MOF sandwich structure confined catalytic membrane has a loading of 0.1 mg / cm 2 ~1.0mg / cm 2 All of them can achieve good removal effect on ranitidine, especially when the loading amount is 0.1 mg / cm 2~0.5mg / cm 2 If the loading is less than 0.1 mg / cm 2 When the loading is higher than 1 mg / cm 2 During the film pressing process, some pores may be randomly compacted and blocked, making the film thicker. In the same vertical space, when the upper part is blocked, the lower volume water flow cannot enter, and when the lower part is blocked, the upper volume water flow cannot pass. Therefore, when the two parts are superimposed, there may be a lot of invalid volume in the membrane, which will cause the catalyst to be unable to contact with pollutants and PMS, reduce the number of active sites, and significantly reduce the degradation rate of new pollutants. Therefore, in the present invention, the catalyst loading of the carbonized Co-MOF sandwich structure confined catalytic membrane is determined to be 0.1 mg / cm 2 ~1.0mg / cm 2 , the preferred range is 0.1 mg / cm 2 ~0.5mg / cm 2 .

[0071] In summary, the carbonized Co-MOF powder and the carbonized Co-MOF sandwich structure confined catalytic film prepared in the embodiments of the present invention have significant advantages over the prior art in that: (1) The material described in the present invention is novel, has stable structural properties, and can maintain an intact crystal structure after being immersed in a variety of solvents for 24 hours.

[0072] (2) The present invention combines the advanced oxidation process with the membrane separation process, integrating multiple functions such as filtration, catalysis and adsorption into one; it can degrade new pollutants efficiently, conveniently and thoroughly, thus reducing the problem of secondary disposal of new pollutant concentrates.

[0073] (3) The present invention provides a new method for constructing a confined space, in which the sandwich configuration can compress the catalyst into the interlayer to form a sufficient confined space; the increase in confined space effectively improves the degradation efficiency of the sandwich structure confined catalytic membrane, and the removal rate of ranitidine reaches 100%.

[0074] (4) The sandwich configuration described in the present invention can play an effective isolation role; on the one hand, it isolates large particle pollutants and prevents pollutants from adhering to the surface of the catalytic material, resulting in a decrease in the number of active sites, thereby affecting the catalytic effect; on the other hand, the isolated catalytic material is directly washed by the water flow first, preventing the catalyst from falling off the membrane surface, resulting in a decrease in performance and metal leaching.

[0075] (5) Even when facing a water body or actual water body containing organic matter, the sandwich structure membrane of the present invention can be directly filtered without pretreatment. The first membrane can intercept large molecules and particulate matter, and the target pollutants enter the second layer - the catalytic material layer for degradation, and are further intercepted by the third membrane, resulting in cleaner effluent.

[0076] (6) The present invention produces a carbonized Co-MOF catalytic material with a stable structure, and further realizes the construction of a confined space by film pressing, thereby improving the performance in various aspects, and the assembly is simple and convenient.

[0077] (7) The method for preparing the sandwich structure confined catalytic membrane of the present invention has a certain degree of scalability; the interlayer material or the upper and lower base membranes can be changed to meet the needs of different scenarios, and can also be transformed into a three-layer or multi-layer multifunctional membrane according to different actual needs, so that one membrane can meet multiple needs.

[0078] The background section of the present invention may contain background information about the problem or environment of the present invention, rather than describing the prior art by others. Therefore, the content contained in the background section is not an admission by the applicant that the prior art is available.

[0079] 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 limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, in the absence of mutual contradiction, the technical personnel in this field 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 modifications can be made herein without departing from the scope defined by the attached claims.

Claims

1. A method for preparing carbonized Co-MOF powder, characterized in that: The following steps are involved: A1: dissolving cobalt salt and 4-(1H-tetrazolyl-5-yl)benzoic acid in N,N-dimethylformamide to prepare a first solution; A2: After the first solution is completely dissolved, subjecting the first solution to a hydrothermal reaction; A3: The product obtained in step A2 is allowed to stand for aging and then centrifuged to wash to obtain a precipitate; A4: drying and grinding the precipitate to obtain Co-MOF powder; A5: The Co-MOF powder is heated and carbonized and then ground to obtain carbonized Co-MOF powder.

2. The method for preparing carbonized Co-MOF powder according to claim 1, characterized in that: The cobalt salt and 4-(1H-tetrazol-5-yl)benzoic acid in step A1 are dissolved in N,N-dimethylformamide in a molar ratio of 1:(0.5-2).

3. The method for preparing carbonized Co-MOF powder according to claim 1, characterized in that: The concentration of the cobalt salt in the first solution is 0.01 mol / L to 0.02 mol / L.

4. The method for preparing carbonized Co-MOF powder according to claim 1, characterized in that: The conditions of the hydrothermal reaction in step A2 are 60°C~100°C, and the time is 24h~72h; step A3 includes aging the product obtained in step A2 at room temperature for 24h~72h, and washing the aged product with N,N-dimethylformamide and pure water at least three times under centrifugal conditions, wherein the centrifugal rate during the centrifugation process is 8000r / min~10000r / min, and the centrifugal time for one wash is 5min~10min; the temperature for drying the precipitate in step A4 is 40°C~70°C, and the time is 8h~24h; step A5 includes adding the Co-MOF powder into a furnace body for heating and carbonization, wherein the heating rate of the furnace body is 5°C / min~10°C / min, the heating and carbonization temperature is 400°C~600°C, and the time is 1h~2h.

5. A carbonized Co-MOF powder, characterized in that The carbonized Co-MOF powder is prepared by the method for preparing the carbonized Co-MOF powder according to any one of claims 1 to 4.

6. A method for preparing a carbonized Co-MOF supported membrane, characterized in that: The following steps are involved: B1: dissolving the carbonized Co-MOF powder according to claim 5 in pure water to obtain a suspension; B2: providing a first polymer membrane, filtering the suspension onto the first polymer membrane, and drying the suspension to obtain a carbonized Co-MOF loaded membrane.

7. The method for preparing a carbonized Co-MOF supported membrane according to claim 6, characterized in that: Step B1 comprises dissolving the carbonized Co-MOF powder according to claim 5 in pure water to obtain a dispersion having a concentration of 6.3 mg / L to 63 mg / L, and then subjecting the dispersion to ultrasonic treatment to obtain a uniformly dispersed suspension; the carbonized Co-MOF loaded film obtained in step B2 has a loading amount of 0.1 mg / cm 2 ~1.0mg / cm 2 .

8. A carbonized Co-MOF supported membrane, characterized in that The carbonized Co-MOF supported membrane is prepared by the preparation method of claim 6 or 7.

9. A method for preparing a carbonized Co-MOF sandwich structure confined catalytic membrane, characterized in that: The following steps are involved: A second polymer membrane is provided, and the second polymer membrane is covered on the side of the carbonized Co-MOF supported membrane of claim 8 where the suspension is filtered, and the carbonized Co-MOF sandwich structure confined catalytic membrane is obtained after pressing.

10. A carbonized Co-MOF sandwich structure confined catalytic membrane, characterized in that: The carbonized Co-MOF sandwich structure confined catalytic membrane is prepared by the preparation method of claim 9.

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