Preparation method and application of pva-co-pe nanofiber membrane loaded with cobalt catalyst

Abstract

The application provides a preparation method and application of a PVA-co-PE nanofiber membrane loaded cobalt catalyst, the PVA-co-PE nanofiber membrane is activated and modified first, and then is placed in a complex solution of a cobalt salt and pyridine coordination to react to obtain the PVA-co-PE nanofiber membrane loaded cobalt catalyst with high catalytic activity, high loading capacity and good recycling performance. The complex of the cobalt salt and pyridine is obtained through coordination, and then is loaded, so that the loading capacity and catalytic activity of cobalt are improved, and the recycling performance of the catalyst is improved. Through the amine coordination on the surface of the PVA-co-PE nanofiber membrane and the coordination of the cobalt salt and pyridine, an electron-rich coordination environment of the cobalt salt is provided, the catalytic activity of the cobalt salt is improved, and the catalyst and peroxymonosulfate form a degradation system applied to the field of water purification, so that the oxidation degradation efficiency is higher, and the application range and prospect are wide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heterogeneous catalysts, in particular to a preparation method and application of a PVA-co-PE nanofiber membrane loaded cobalt catalyst. BACKGROUND

[0002] In-situ chemical oxidation is an emerging wastewater treatment technology, because it has the advantages of almost non-selective degradation, high efficiency, and the possibility of enhancing microbial activity after oxidation; in addition, it can completely mineralize various organic compounds. At present, persulfate (PMS) is widely used as an oxidant for wastewater treatment in chemical oxidation technology because it can generate strong oxidizing sulfate radicals during decomposition; it has the advantages of high oxidation efficiency, flexibility and wide application, long half-life (30-40 μs), high selectivity for unsaturated aromatic hydrocarbons, and slow precursor oxidant consumption rate due to its high stability. In addition, persulfate is eventually converted to sulfate, which has less adverse effects on the environment; however, the self-decomposition process of persulfate is very slow, which increases the time cost of water purification, so it is necessary to activate it to accelerate the formation of sulfate radicals.

[0003] There are many methods in the prior art for activating PMS, but the method based on transition metals, i.e. using Cu, Fe, Mn and Co, is considered to be the most effective; among them, Co is considered to be one of the most suitable non-noble metals for PMS activation due to its high activity. In the homogeneous cobalt ion catalytic system, the dosage of cobalt ions is usually large; in view of this problem, the invention patent (application number CN 202210774113.1) discloses a method and application of trace cobalt cooperated with electrically activated persulfate, which improves the biological efficiency of cobalt ion activated persulfate by conducting electric treatment when cobalt activates persulfate, generates more sulfate radicals and hydroxyl radicals, and more effectively reduces organic pollutants, reducing the dosage of cobalt ions; however, this method requires electric treatment, which is difficult to apply in large-scale purification plants and has low safety.

[0004] Heterogeneous catalysts have the characteristics of easy separation and easy recovery; in recent years, the non-homogenization of cobalt salts and their use in activating PMS to degrade organic pollutants have attracted widespread attention from scientific researchers. Fiber substrates have become a research hotspot for heterogeneous catalyst carriers because they are easy to handle in industrial operations and can be easily separated from reaction solutions; in addition, fiber materials also have other attractive properties, including solidity, chemical stability, industrial usability and cost-effectiveness. However, heterogeneous catalysts have the problem of slower reaction rate and lower catalytic efficiency than homogeneous catalysts, so the prior art has not yet found a method to make cobalt salts non-homogenized while still maintaining their high catalytic activity for PMS and better application in water purification.

[0005] Therefore, it is necessary to design an improved preparation method and application of PVA-co-PE nanofiber membrane supported cobalt catalyst to solve the above problems. SUMMARY

[0006] The purpose of the present application is to provide a preparation method and application of PVA-co-PE nanofiber membrane supported cobalt catalyst, which is activated and modified first, then reacted in a complex solution of cobalt salt and pyridine coordination to obtain a PVA-co-PE nanofiber membrane supported cobalt catalyst with high catalytic activity, high loading capacity and good reusability; the catalyst and PMS form a degradation system applied in water purification field, which has higher oxidative degradation efficiency and wide application range and prospect.

[0007] To achieve the above-mentioned purposes, the present application provides a preparation method of PVA-co-PE nanofiber membrane supported cobalt catalyst, comprising the following steps:

[0008] S1, soaking the PVA-co-PE nanofiber membrane in a strong alkali solution, and then soaking it in a 1,4-dioxane solution of tricyanopyridine to obtain an activated PVA-co-PE nanofiber membrane;

[0009] S2, soaking the activated PVA-co-PE nanofiber membrane prepared in step S1 in a tetraethylenepentamine solution, washing it with deionized water until the waste liquid is neutral, and drying to obtain a modified PVA-co-PE nanofiber membrane;

[0010] S3, uniformly mixing a cobalt salt aqueous solution and a pyridine aqueous solution to obtain a complex solution of cobalt salt and pyridine coordination;

[0011] S4, placing the modified PVA-co-PE nanofiber membrane obtained in step S2 in the complex solution of step S3, reacting for 10-14 hours, and drying after washing to obtain a PVA-co-PE nanofiber membrane supported cobalt catalyst.

[0012] As a further improvement of the present application, in step S3, the volume ratio of the cobalt salt aqueous solution to the pyridine aqueous solution in the complex solution is 1:(1.5-2.5); the mass concentration of the cobalt salt aqueous solution is 15-25 g / L; and the mass percentage concentration of the pyridine aqueous solution is 25%-35%.

[0013] As a further improvement of the present application, in step S2, the volume ratio of tetraethylenepentamine to ethanol in the tetraethylenepentamine solution is (2.5-3.5):(6.5-7.5).

[0014] As a further improvement of the present application, in step S1, the substance concentration of the strong alkali solution is 2.0-4.0 mol / L; the mass percentage concentration of the cyanuric chloride in the 1,4-dioxane solution is 8wt%-12wt%.

[0015] As a further improvement of the present application, the PVA-co-PE nanofiber is soaked in the strong alkali solution for 0.5-1.5 h at a temperature of 20-35℃, and is soaked in the cyanuric chloride 1,4-dioxane solution for 1.5-2.5 h at a temperature of 20-35℃.

[0016] As a further improvement of the present application, the strong alkali solution comprises one of sodium hydroxide and potassium hydroxide.

[0017] As a further improvement of the present application, the PVA-co-PE nanofiber is soaked in the tetraethylenepentamine solution for 20-40 min at a temperature of 20-35℃.

[0018] As a further improvement of the present application, the diameter of the fiber in the PVA-co-PE nanofiber membrane is 100-500 nm; the specific surface area of the PVA-co-PE nanofiber membrane is 15-17 m 2 / g.

[0019] As a further improvement of the present application, in step S3, the pyridine species in the pyridine aqueous solution comprises one of pyridine, 2,2'-bipyridine, 2-methylpyridine, and 3-methylpyridine; the cobalt salt in the cobalt salt aqueous solution comprises one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt tungstate.

[0020] The present application also provides an application of the PVA-co-PE nanofiber membrane supported cobalt catalyst prepared by the preparation method of any one of the above, which is applied to catalytic activation of peroxymonosulfate and to the field of water purification.

[0021] As a further improvement of the present application, when the PVA-co-PE nanofiber membrane supported cobalt catalyst is applied to the field of water purification, the water environment is weakly acidic or neutral.

[0022] The present application has the following beneficial effects:

[0023] 1. The application provides a preparation method and application of a PVA-co-PE nanofiber membrane loaded cobalt catalyst, which comprises the following steps: first, soaking the PVA-co-PE nanofiber membrane in a strong alkali solution, then soaking it in a 1,4-dioxane solution of cyanuric chloride, and finally soaking it in a tetraethylenepentamine solution to obtain a modified PVA-co-PE nanofiber membrane; uniformly mixing an aqueous cobalt salt solution and an aqueous pyridine solution to obtain a complex solution of the cobalt salt and pyridine; and finally, soaking the modified PVA-co-PE nanofiber membrane in the complex solution, and obtaining the PVA-co-PE nanofiber membrane loaded cobalt catalyst after reaction. The PVA-co-PE nanofiber membrane is first activated and modified, and then reacted in the complex solution of the cobalt salt and pyridine to obtain the PVA-co-PE nanofiber membrane loaded cobalt catalyst with high catalytic activity, high loading capacity and good reusability; when the heterogeneous catalyst and peroxymonosulfate form a degradation system and are applied in the field of water purification, the degradation efficiency is higher, and the application range and prospect are wide.

[0024] 2. The PVA-co-PE nanofiber membrane is activated and modified before being loaded with cobalt salt, the strong alkali solution can remove impurities and pollutants on the surface of the PVA-co-PE nanofiber membrane, and activate the PVA-co-PE nanofiber, so that it can be subsequently grafted and modified, and provides an alkaline condition for the grafting modification; then the PVA-co-PE nanofiber membrane is modified by 1,4-dioxane solution of cyanuric chloride and tetraethylenepentamine in two steps, cyanuric chloride acts as a linker to connect the fiber membrane substrate and tetraethylenepentamine, tetraethylenepentamine provides stronger coordination ability and loading capacity for the PVA-co-PE nanofiber membrane, and the two synergistically improve the coordination and loading capacity of the PVA-co-PE nanofiber membrane for cobalt salt, which is conducive to the loading of the complex of cobalt salt and pyridine on the PVA-co-PE nanofiber membrane.

[0025] 3、The application first carries out coordination of cobalt salt and pyridine to obtain a complex, and then loads the complex on the surface of the modified PVA-co-PE nanofiber membrane, thereby further improving the loading amount of the cobalt salt on the surface of the PVA-co-PE nanofiber membrane; when the cobalt salt is coordinated with the amino group on the surface of the PVA-co-PE nanofiber membrane, the presence of the pyridine not only provides a favorable environment for the coordination, but also can interact with the active groups on the surface of the fiber membrane, thereby improving the loading amount of the cobalt salt on the surface of the PVA-co-PE nanofiber membrane and the solid loading stability of the cobalt salt on the surface of the nanofiber membrane, and further improving the recycling performance of the catalyst.

[0026] 4、The application selects the PVA-co-PE nanofiber membrane as the carrier of the heterogeneous cobalt catalyst, the surface of the PVA-co-PE nanofiber membrane has more hydroxyl groups, and the nanoscale fiber improves the large specific surface area and provides more abundant reaction sites, thereby solving the problems of low loading amount of metal salt and poor catalytic degradation activity from the source; in addition, the PVA-co-PE nanofiber membrane has good hydrophilicity, and after loading the cobalt salt, the PVA-co-PE nanofiber membrane can better contact the pollutants in the water body when used with the persulfate for water purification. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The microelectronic microscope graph of the PVA-co-PE nanofiber membrane loaded with the cobalt catalyst prepared in the embodiment.

[0028] Figure 2 The microelectronic microscope graph of the original PVA-co-PE nanofiber membrane used in the embodiment.

[0029] Figure 3 The process graph of the catalytic performance detection of the PVA-co-PE nanofiber membrane loaded with the cobalt catalyst prepared in the embodiment 1. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the application more clear, the application is described in detail below with reference to the drawings and specific embodiments.

[0031] Here, it also needs to be explained that, in order to avoid the unnecessary details from blurring the application, only the structures and / or processing steps closely related to the scheme of the application are shown in the drawings, and other details not closely related to the application are omitted.

[0032] It is also important to note that the term "comprising" or "including" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0033] A preparation method of a PVA-co-PE nanofiber membrane loaded with a cobalt catalyst, comprising the following steps:

[0034] S1, soaking the PVA-co-PE nanofiber membrane in a strong alkali solution, and then soaking it in a 1,4-dioxane solution of tricyanogen chloride to obtain an activated PVA-co-PE nanofiber membrane; soaking the PVA-co-PE nanofiber membrane in a strong alkali solution can remove surface impurities and pollutants, etc., and activate the PVA-co-PE nanofiber, so that it can be subsequently grafted and modified, and also provides an alkaline condition for the grafting modification;

[0035] S2, soaking the activated PVA-co-PE nanofiber membrane prepared in step S1 in a tetraethylenepentamine solution, and then washing it with deionized water until the waste liquid is neutral, and drying to obtain a modified PVA-co-PE nanofiber membrane; wherein the volume ratio of tetraethylenepentamine to ethanol is (2.5-3.5):(6.5-7.5); two-step modification is carried out in turn using a 1,4-dioxane solution of tricyanogen chloride and tetraethylenepentamine, wherein tricyanogen chloride acts as a linker to connect the fiber membrane substrate and tetraethylenepentamine, and tetraethylenepentamine provides stronger coordination ability and loading capacity for the PVA-co-PE nanofiber membrane, and the two work together to improve the coordination and loading capacity of the PVA-co-PE nanofiber membrane for cobalt salt, which is conducive to the loading of the cobalt salt and pyridine complex on the PVA-co-PE nanofiber membrane;

[0036] S3, uniformly mixing a cobalt salt aqueous solution and a pyridine aqueous solution, wherein the volume ratio of the cobalt salt aqueous solution to the pyridine aqueous solution is 1:(1.5-2.5), to obtain a complex solution of the cobalt salt and pyridine coordination; wherein the mass concentration of the cobalt salt aqueous solution is 15-25 g / L, and the mass percentage concentration of the pyridine aqueous solution is 25%-35%;

[0037] The coordination of cobalt salt and pyridine first obtains the complex, and then the complex is loaded on the surface of the modified PVA-co-PE nanofiber membrane, so that the loading amount of the cobalt salt on the surface of the PVA-co-PE nanofiber membrane is increased; when the cobalt salt is coordinated with the amino group on the surface of the PVA-co-PE nanofiber membrane, the presence of pyridine not only provides a favorable environment for the coordination, but also interacts with the active groups on the surface of the fiber membrane, on the one hand, the loading amount of the cobalt salt on the surface of the PVA-co-PE nanofiber membrane is increased, and on the other hand, the solid loading stability of the cobalt salt on the surface of the nanofiber membrane is improved, and then the recycling performance of the catalyst is improved;

[0038] S4, the modified PVA-co-PE nanofiber membrane obtained in step S2 is placed in the complex solution of step S3, and reacted for 10-14 hours, and then washed and dried to obtain the PVA-co-PE nanofiber membrane loaded with cobalt catalyst.

[0039] Particularly, the present application provides an electron-rich coordination environment of the cobalt salt by coordinating the amine on the surface of the PVA-co-PE nanofiber membrane and coordinating the cobalt salt with pyridine, which is conducive to improving the catalytic activity of the cobalt salt, and then is conducive to improving the oxidative degradation efficiency when the degradation system composed of the catalyst and persulfate is applied to the field of water purification.

[0040] Specifically, in step S1, the molar concentration of the strong alkali solution is 2.0-4.0 mol / L; the mass percentage concentration of cyanuric chloride in the 1,4-dioxane solution is 8wt%-12wt%. The PVA-co-PE nanofiber is soaked in the strong alkali solution for 0.5-1.5 hours at a temperature of 20-35°C, and is soaked in the cyanuric chloride 1,4-dioxane solution for 1.5-2.5 hours at a temperature of 20-35°C. The PVA-co-PE nanofiber is soaked in the tetraethylenepentamine solution for 20-40 minutes at a temperature of 20-35°C. In this way, by limiting the concentration of the strong alkali solution and the soaking time of the PVA-co-PE nanofiber membrane in the strong alkali solution, the structure of the nanofiber membrane is avoided from being damaged, the mechanical properties are avoided from being affected, and then the service life of the heterogeneous catalyst is affected under the premise of realizing the activation of the fiber membrane. By limiting the soaking time of the PVA-co-PE nanofiber membrane in the cyanuric chloride 1,4-dioxane solution and the tetraethylenepentamine solution, the modification degree is controlled, the two-step modification plays the best synergistic effect, and the loading of the cobalt salt on the nanofiber membrane is facilitated.

[0041] In some specific embodiments, the strong alkali solution includes one of sodium hydroxide and potassium hydroxide.

[0042] Specifically, the diameter of the fiber in the PVA-co-PE nanofiber membrane is 100-500 nm; the specific surface area of the PVA-co-PE nanofiber membrane is 15-17 m2 The PVA-co-PE nanofiber membrane is selected as the carrier of the heterogeneous cobalt catalyst, the surface of the PVA-co-PE nanofiber membrane has more hydroxyl groups, and the nanoscale fiber improves the large specific surface area and provides more reaction sites, so that the problems of low loading capacity of metal salt and poor catalytic degradation activity are solved from the source; in addition, the PVA-co-PE nanofiber membrane has good hydrophilicity, and after loading the cobalt salt, the PVA-co-PE nanofiber membrane can better contact the pollutants in the water body when used with persulfate for water purification, and the purification effect is improved.

[0043] In some specific embodiments, in step S3, the pyridine species in the pyridine aqueous solution includes one of pyridine, 2,2'-bipyridine, 2-methylpyridine and 3-methylpyridine; and the cobalt salt in the cobalt salt aqueous solution includes one of cobalt nitrate, cobalt sulfate, cobalt chloride and cobalt tungstate.

[0044] In some specific embodiments, the drying treatment is drying at 50-70 DEG C, and the cleaning is performed by using deionized water.

[0045] The PVA-co-PE nanofiber membrane is activated and modified first, and then is placed in a complex solution of cobalt salt and pyridine coordination to obtain a PVA-co-PE nanofiber membrane loaded cobalt catalyst with high catalytic activity, high solid loading stability, high loading capacity and good reusability; when the catalyst is applied in the field of water purification together with persulfate to form a degradation system, the catalyst has higher oxidative degradation efficiency, and has wide application range and prospect.

[0046] The application also provides an application of the PVA-co-PE nanofiber membrane loaded cobalt catalyst, the PVA-co-PE nanofiber membrane loaded cobalt catalyst is applied in catalytic activation of persulfate and in the field of water purification; when the PVA-co-PE nanofiber membrane loaded cobalt catalyst is applied in the field of water purification, the water environment is weakly acidic or neutral, preferably weakly acidic, which is conducive to the conversion of cobalt ions to high valence state in the weakly acidic environment, and the high valence state cobalt ions not only have better catalytic effect on persulfate, but also can participate in the degradation of organic pollutants, thereby improving the water purification effect.

[0047] Example 1

[0048] The embodiment provides a preparation method of a PVA-co-PE nanofiber membrane loaded cobalt catalyst, which comprises the following steps:

[0049] S1, the PVA-co-PE nanofiber membrane is placed in a 3M sodium hydroxide solution, soaked at 30°C for 1h, and then placed in a 1,4-dioxane solution containing 10wt% cyanuric chloride, soaked at 30°C for 2h, to obtain an activated PVA-co-PE nanofiber membrane; wherein the average diameter of the fibers in the PVA-co-PE nanofiber membrane is 300nm; the specific surface area of the PVA-co-PE nanofiber membrane is 16m 2 / g

[0050] S2, the activated PVA-co-PE nanofiber membrane prepared in step S1 is placed in a tetraethylenepentamine solution (volume ratio of tetraethylenepentamine: ethanol = 3:7), soaked at 30°C for 30min, washed with deionized water until the waste liquid is neutral, and dried at 60°C to obtain a modified PVA-co-PE nanofiber membrane;

[0051] S3, a cobalt nitrate aqueous solution with a mass concentration of 20g / L is uniformly mixed with a pyridine aqueous solution with a mass percentage of 30%, and the volume ratio of the cobalt salt aqueous solution to the pyridine aqueous solution is 1:2, to obtain a complex solution of cobalt salt and pyridine coordination;

[0052] S4, the modified PVA-co-PE nanofiber membrane obtained in step S2 is placed in the complex solution of step S3, reacted for 12h, then washed with deionized water, and dried at 60°C to obtain a PVA-co-PE nanofiber membrane supported cobalt catalyst.

[0053] Please refer to Figures 1-2 , Figure 1 The micro-SEM image and EDS image of the PVA-co-PE nanofiber membrane supported cobalt catalyst prepared in this example are shown in Figure 2 The micro-SEM image and EDS image of the original PVA-co-PE nanofiber membrane used in this example are shown in the figure. From the SEM image in the figure, it can be seen that the surface of the modified nanofiber has not been damaged, which can indicate that the PVA-CO-PE nanofiber membrane has a certain strength. In addition, the EDS spectrum can not only prove that the cobalt ions are successfully supported on the PVA-CO-PE nanofiber membrane, but also can see that the cobalt ions are uniformly distributed on the surface of the fiber.

[0054] Comparative Example 1

[0055] Comparative Example 1 provides a preparation method of a PVA-co-PE nanofiber membrane supported cobalt catalyst. Compared with Example 1, the difference lies in that step S2 is not performed, and the rest is substantially the same as Example 1, which will not be repeated here.

[0056] Comparative Example 2

[0057] Comparative Example 2 provides a preparation method of a PVA-co-PE nanofiber membrane supported cobalt catalyst, which is substantially the same as that of Example 1 except that, in step S1, the PVA-co-PE nanofiber membrane is not soaked in the 1,4-dioxane solution of cyanuric chloride, and the rest is substantially the same as that of Example 1, which is not described here again.

[0058] Comparative Example 3

[0059] Comparative Example 3 provides a preparation method of a PVA-co-PE nanofiber membrane supported cobalt catalyst, which is substantially the same as that of Example 1 except that, in step S1, the PVA-co-PE nanofiber membrane is not soaked in the sodium hydroxide solution, and the rest is substantially the same as that of Example 1, which is not described here again.

[0060] Comparative Example 4

[0061] Comparative Example 4 provides a preparation method of a PVA-co-PE nanofiber membrane supported cobalt catalyst, which is substantially the same as that of Example 1 except that, in step S3, the treatment is not performed, and the rest is substantially the same as that of Example 1, which is not described here again.

[0062] Comparative Example 5

[0063] Comparative Example 5 provides a preparation method of a PVA-co-PE nanofiber membrane supported cobalt catalyst, which is substantially the same as that of Example 1 except that, in steps S3 and S4, the complex solution is replaced by a cobalt nitrate solution with the same concentration as that of Example 1, and the rest is substantially the same as that of Example 1, which is not described here again.

[0064] The catalytic activity and mechanical properties of the PVA-co-PE nanofiber membrane supported cobalt catalysts prepared in Example 1 and Comparative Examples 1-5 are detected. The specific detection method of the catalytic activity is as follows: 100 mL of rhodamine B solution (10 mg / L) is taken in a 250 mL beaker, 50 mg of PVA-co-PE nanofiber membrane supported cobalt catalyst is added first, then PMS (100 mg / L) is added, and the mixture is stirred at room temperature. The degradation of rhodamine B is monitored by ultraviolet spectrophotometry, and the repeatability test is performed. The detection results are shown in the following table.

[0065] Table 1 Catalyst performance detection results of Example 1 and Comparative Examples 1-5

[0066]

[0067] From Table 1, the original PVA-co-PE nanofiber membrane has no degradation effect on rhodamine B. From Comparative Examples 1-5, when the fiber is not soaked in sodium hydroxide, trichloroamine cannot be grafted with the fiber membrane; the fiber membrane is not activated by trichloro cyanide, and the modification grafting of tetraethylene pentamine cannot be carried out; the fiber membrane is not modified by tetraethylene pentamine, and the complex of cobalt salt and pyrrole cannot be accurately loaded on the surface of the fiber membrane; without soaking the activated fiber into the complex solution, no cobalt salt is loaded, and the modified fiber membrane has no degradation performance. In Comparative Example 5, the cobalt salt is directly loaded, the loading amount of the cobalt salt on the surface of the fiber membrane is poor, which leads to low degradation rate of the catalyst and poor reusability. It can be seen that the soaking treatment, activation and modification of the fiber by using specific reagents are indispensable, and are interrelated, so as to prepare the PVA-co-PE nanofiber membrane loaded cobalt catalyst of the present application.

[0068] In addition, through repeated verification, it is found that after 10 times of repetition, the degradation rate of the catalyst prepared in Example 1 does not decrease obviously, which indicates that the cobalt ions loaded by coordination make the catalyst have certain stability. Through the tensile test, it is verified that the strength of the modified nanofiber membrane does not change, so that the modified PVA-co-PE nanofiber membrane under the optimal conditions does not affect the strength of the fiber membrane.

[0069] Please refer to Figure 3 FIG. 1 is a process diagram of the catalytic performance detection of the PVA-co-PE nanofiber membrane loaded cobalt catalyst prepared in Example 1, and the recording time is 3 min, 6 min, 9 min, 12 min and 15 min. As can be seen from the figure, with the increase of time, it can be seen that the color of the solution gradually becomes lighter, which indicates that rhodamine B is gradually degraded; at 15 min, the solution is nearly colorless, which indicates that the degradation degree of rhodamine B is high.

[0070] Comparative Example 6

[0071] Comparative Example 6 provides a preparation method of a PVA-co-PE nanofiber membrane loaded cobalt catalyst, which is different from Example 1 in that in step S2, iminodiacetic acid with a concentration of 2 mol / L is used instead of tetraethylene pentamine solution, and the rest is substantially the same as Example 1, which will not be repeated here.

[0072] Comparative Example 7

[0073] Comparative Example 7 provides a preparation method of a nanofiber membrane loaded cobalt catalyst, which is different from Example 1 in that polypropylene nanofiber membrane is used instead of PVA-co-PE nanofiber membrane, and the rest is substantially the same as Example 1, which will not be repeated here.

[0074] Example 2

[0075] Example 2 provides a preparation method of PVA-co-PE nanofiber membrane supported cobalt catalyst, which is different from Example 1 in that the volume ratio of the aqueous cobalt salt solution to the aqueous pyridine solution is 1:2.5 in step S3, and the rest is substantially the same as Example 1, which will not be repeated here.

[0076] Comparative Example 8

[0077] Comparative Example 8 provides a preparation method of PVA-co-PE nanofiber membrane supported cobalt catalyst, which is different from Example 1 in that the volume ratio of the aqueous cobalt salt solution to the aqueous pyridine solution is 1:1 in step S3, and the rest is substantially the same as Example 1, which will not be repeated here.

[0078] Comparative Example 9

[0079] Comparative Example 9 provides a preparation method of PVA-co-PE nanofiber membrane supported cobalt catalyst, which is different from Example 1 in that the volume ratio of the aqueous cobalt salt solution to the aqueous pyridine solution is 1:4 in step S3, and the rest is substantially the same as Example 1, which will not be repeated here.

[0080] The catalysts prepared in Example 2 and Comparative Examples 6-9 were also subjected to catalytic activity and mechanical property detection using the above detection method, and the results are shown in the following table.

[0081] Table 2 Catalyst performance detection results of Example 2 and Comparative Examples 6-9

[0082]

[0083] As can be seen from Table 2, the volume ratio of the aqueous cobalt salt solution to the aqueous pyridine solution is 1:2, which is the optimal condition. If the volume ratio of the solution is too small or too large, it is not conducive to the efficient generation of the complex. When the modified monomer is changed from tetraethylenepentamine solution to iminodiacetic acid, it is found that the degradation rate is reduced, and the catalyst has poor reusability, because the carboxyl group forms a carboxylate salt with the metal cobalt ion, and the electron-deficient carboxyl group is not conducive to the activation of the cobalt salt catalyst. When it is applied to degrade the cationic dye rhodamine B, there is an ion exchange problem in the aqueous solution, which causes the catalyst to be poisoned, thereby reducing the catalytic activity. When the fiber membrane carrier is replaced by polypropylene fiber, it is found that the polypropylene fiber cannot be successfully modified by the same method, so it cannot achieve the degradation of rhodamine B.

[0084] In summary, the present application provides a preparation method and application of a PVA-co-PE nanofiber membrane supported cobalt catalyst. The PVA-co-PE nanofiber membrane is first activated and modified, and then placed in a solution of a cobalt salt and pyridine coordination complex for reaction to obtain a PVA-co-PE nanofiber membrane supported cobalt catalyst with high catalytic activity, high loading capacity and good reusability. In the present application, the cobalt salt is coordinated with pyridine to obtain a complex, which is then loaded on the surface of the modified PVA-co-PE nanofiber membrane. The amino group on the surface of the PVA-co-PE nanofiber membrane is coordinated with the cobalt salt. The presence of pyridine not only provides a favorable environment for the coordination, but also interacts with the active groups on the surface of the fiber membrane. On the one hand, the loading capacity of the cobalt salt on the surface of the PVA-co-PE nanofiber membrane is improved, and on the other hand, the solid loading stability of the cobalt salt on the surface of the nanofiber membrane is improved, thereby improving the recycling performance of the catalyst. In the present application, the amine coordination on the surface of the PVA-co-PE nanofiber membrane and the coordination of the cobalt salt with pyridine both provide an electron-rich coordination environment for the cobalt salt, which is conducive to improving the catalytic activity of the cobalt salt, and thus the PVA-co-PE nanofiber membrane supported cobalt catalyst and the degradation system composed of peroxymonosulfate have higher oxidative degradation efficiency when applied in the field of water purification, and have a wide range of applications and prospects.

[0085] The above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a PVA-co-PE nanofiber membrane supported cobalt catalyst, characterized in that, The method comprises the following steps: S1, soaking the PVA-co-PE nanofiber membrane in a strong alkali solution, and then soaking the PVA-co-PE nanofiber membrane in a 1,4-dioxane solution of tricyanopyridine to obtain an activated PVA-co-PE nanofiber membrane; S2, soaking the activated PVA-co-PE nanofiber membrane prepared in step S1 in a tetraethylenepentamine solution, washing the PVA-co-PE nanofiber membrane with deionized water until the waste liquid is neutral, and drying the PVA-co-PE nanofiber membrane to obtain a modified PVA-co-PE nanofiber membrane; S3, uniformly mixing a cobalt salt aqueous solution and a pyridine aqueous solution to obtain a complex solution of the cobalt salt and the pyridine; in the complex solution, the volume ratio of the cobalt salt aqueous solution to the pyridine aqueous solution is 1:(1.5-2.5); the mass concentration of the cobalt salt aqueous solution is 15-25 g / L; and the mass percentage concentration of the pyridine aqueous solution is 25%-35%; S4, soaking the modified PVA-co-PE nanofiber membrane obtained in step S2 in the complex solution of step S3, reacting for 10-14 hours, and drying the PVA-co-PE nanofiber membrane after washing to obtain a PVA-co-PE nanofiber membrane loaded with a cobalt catalyst.

2. The method for preparing PVA-co-PE nanofiber membrane supported cobalt catalyst according to claim 1, characterized in that, In step S2, in the tetraethylenepentamine solution, the volume ratio of tetraethylenepentamine to ethanol is (2.5-3.5):(6.5-7.5).

3. The method for preparing the cobalt catalyst supported on the PVA-co-PE nanofiber membrane according to claim 1, characterized in that, In step S1, the strong alkali solution has a concentration of 2.0-4.0 mol / L; and the mass percentage concentration of tricyanopyridine in the 1,4-dioxane solution is 8wt%-12wt%.

4. The method for preparing PVA-co-PE nanofiber membrane supported cobalt catalyst according to claim 3, characterized in that, The PVA-co-PE nanofiber is soaked in the strong alkali solution for 0.5-1.5 hours at a temperature of 20-35°C, and is soaked in the 1,4-dioxane solution of tricyanopyridine for 1.5-2.5 hours at a temperature of 20-35°C.

5. The method for preparing the cobalt catalyst supported on the PVA-co-PE nanofiber membrane according to claim 4, characterized in that, The PVA-co-PE nanofiber is soaked in the tetraethylenepentamine solution for 20-40 minutes at a temperature of 20-35°C.

6. The method for preparing the cobalt catalyst supported on the PVA-co-PE nanofiber membrane according to claim 1, characterized in that, The strong alkali solution comprises one of sodium hydroxide and potassium hydroxide.

7. The method for preparing a cobalt catalyst supported on a PVA-co-PE nanofiber membrane according to claim 1, characterized in that, The diameter of the fiber in the PVA-co-PE nanofiber membrane is 100-500 nm; the specific surface area of the PVA-co-PE nanofiber membrane is 15-17 m 2 / g.

8. The method for preparing a cobalt catalyst supported on a PVA-co-PE nanofiber membrane according to claim 1, characterized in that, In step S3, the pyridine in the pyridine aqueous solution comprises one of pyridine, 2,2'-bipyridine, 2-methylpyridine, and 3-methylpyridine; and the cobalt salt in the cobalt salt aqueous solution comprises one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt tungstate.

9. Use of a PVA-co-PE nanofiber membrane supported cobalt catalyst prepared by the method of any one of claims 1-8, characterized in that, The PVA-co-PE nanofiber membrane loaded with the cobalt catalyst is applied to catalytic activation of persulfate and to the field of water purification.

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