Ferrocenyl hydrogel catalyst, preparation method thereof and application of ferrocenyl hydrogel catalyst in degradation of nitro compound

Abstract

The invention provides a ferrocenyl hydrogel catalyst, a preparation method thereof and application of the ferrocenyl hydrogel catalyst in degradation of nitro compounds, and belongs to the technical field of water treatment. According to the invention, a sol-gel method is adopted to synthesize the single-metal cross-linked PVA / alginate-ferrocene double-network hydrogel. Wherein the PVA is an environment-friendly material, the glutaraldehyde crosslinked PVA hydrogel has excellent mechanical properties, the PVA has a large amount of-OH, and the-OH has lone electron pairs, so that after the PVA is added into the alginate-ferrocene iron gel, the mechanical properties of the alginate-ferrocene iron gel can be improved, and an electron-rich microenvironment is formed around transition metal. The prepared hydrogel catalyst has the advantages of being high in mechanical strength, low in Fc dissolution, environmentally friendly and the like, and when the hydrogel catalyst is applied to catalytic degradation of nitrobenzene, the degradation rate of the nitrobenzene reaches up to 93% or above under the conditions that the concentration of the nitrobenzene is 10 mg / L, the pH value of wastewater is 3 and the system action time is 2 h.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly to a ferrocene-based hydrogel catalyst, a preparation method thereof, and an application thereof in the degradation of nitro compounds. Background Art

[0002] Nitrobenzene is commonly found as a pollutant in polluted water bodies and is widely used in the manufacture of dyes, textiles, paper, aniline, pesticides, and explosives. However, these processes generate a large amount of wastewater containing nitrobenzene, which can have an adverse impact on human health, including cancer, anemia, etc.

[0003] The existing ways to degrade organic wastewater mainly include biodegradation, adsorption, coagulation / flocculation, chemical oxidation, membrane separation, and advanced oxidation processes (AOPs). AOPs can generate effective reactive oxygen species (ROS) during the reaction process, converting most organic pollutants into small molecule compounds or even into CO2 and H2O. AOPs are considered an effective technology for treating refractory pollutants. Among them, heterogeneous catalytic technology can not only effectively activate persulfate, hydrogen peroxide, etc. to generate highly active free radicals, but also limit the generation of iron-containing sludge during the degradation process, thereby reducing secondary pollution. Ferrocene (Fc) is a heterogeneous catalyst used to activate substances such as persulfate and hydrogen peroxide to degrade pollutants. However, chemically reagent-grade Fc is nanoscale and Fc is prone to aggregation, and directly using Fc will lead to problems of difficult recovery. Summary of the Invention

[0004] The purpose of the present invention is to provide a ferrocene-based hydrogel catalyst, a preparation method thereof, and an application thereof in the degradation of nitro compounds, which can solve the problems of easy aggregation and difficult recovery of Fc.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a ferrocene-based hydrogel catalyst, comprising the following steps:

[0007] Mix a calcium salt and water to obtain a calcium-containing solution;

[0008] Mix alginate, ferrocene, and water, and perform thermal polymerization to obtain an alginate-ferrocene hydrogel;

[0009] Mix the alginate-ferrocene hydrogel, polyvinyl alcohol, and glutaraldehyde, and perform a first cross-linking reaction to obtain a PVA hydrogel;

[0010] Mix the calcium-containing solution and the PVA hydrogel, and perform a second cross-linking reaction to obtain a ferrocene-based hydrogel catalyst.

[0011] Preferably, the calcium salt includes one or both of calcium chloride and calcium sulfate.

[0012] Preferably, the mass ratio of the calcium salt to water is 1-2:90-110.

[0013] Preferably, the temperature for mixing the calcium salt with water is 15-30 °C, and the time is 10-60 min.

[0014] Preferably, the alginate includes sodium alginate, potassium alginate or ammonium alginate; the mass ratio of the alginate, ferrocene and water is 2-3:2-3:50-70.

[0015] Preferably, the temperature for thermal polymerization is 50-90 °C, and the time is 1-3 h.

[0016] Preferably, the mass ratio of the alginate-ferrocene hydrogel to polyvinyl alcohol is 1-2:1.5-3.5; the mass ratio of glutaraldehyde to polyvinyl alcohol is 1-2:4-6; the temperature for the first cross-linking reaction is 15-30 °C, and the time is 20-40 min.

[0017] Preferably, the volume ratio of the PVA hydrogel to the calcium-containing solution is 1:2-20; the temperature for the second cross-linking reaction is 15-30 °C, and the time is 1-4 days.

[0018] The present invention provides a ferrocene-based hydrogel catalyst obtained by the preparation method described in the above technical solution.

[0019] The present invention provides the application of the ferrocene-based hydrogel catalyst described in the above technical solution in the degradation of nitro compounds.

[0020] The present invention provides a preparation method of a ferrocene-based hydrogel catalyst, which synthesizes a single-metal cross-linked PVA / alginate double-network hydrogel by the sol-gel method (the first cross-linking and the second cross-linking). Among them, PVA is an environmentally friendly material, and the glutaraldehyde-cross-linked PVA hydrogel has excellent mechanical properties, and PVA has a large number of -OH groups, and these -OH groups have lone electron pairs. Therefore, after adding PVA to the alginate hydrogel, its mechanical properties can be improved, and an electron-rich microenvironment can be formed around ferrocene, so that the rapid conversion of Fe(III) and Fe(II) can be accelerated during the degradation process, thereby enhancing the reaction rate of the Fenton reaction and further enhancing the catalytic performance. The hydrogel catalyst prepared by the present invention has the advantages of high mechanical strength, low Fc dissolution, environmental friendliness, etc. When it is applied to the catalytic degradation of nitrobenzene, under the conditions that the concentration of nitrobenzene is 10 mg / L, the pH value of the wastewater is 3, and the system action time is 2 h, the degradation rate of nitrobenzene is as high as over 93%.

[0021] The double-crosslinked structure provided by the present invention (alginate and PVA, with ferrocene as the reaction center immobilized in the double network) has excellent immobilization function for ferrocene and is not easily dispersed, which can solve the problem of easy aggregation of Fc. Moreover, in the present invention, ferrocene is combined with the hydrogel, and the environmental protection and easy recovery characteristics of the hydrogel beads are utilized to make the recovery of ferrocene easier. The present invention immobilizes the ferrocene catalyst on the double-crosslinked structure hydrogel, while improving the problem of easy aggregation and difficult recovery of ferrocene, provides an effective degradation pathway for the refractory pollutant nitrobenzene.

[0022] The ferrocene-based hydrogel catalyst prepared in the present invention is a hydrogel composite system modified by ferrocene, which has guiding significance for the development of heterogeneous catalysts, and can effectively improve the degradation efficiency of nitrobenzene, and has great potential in practical applications. Brief Description of the Drawings

[0023] Figure 1 SEM images (a-c) and EDS spectra (d-g) of the hydrogel catalyst in Example 1;

[0024] Figure 2 Compression stress-strain curves of the hydrogel catalyst and Alg-Fc hydrogel in Example 1;

[0025] Figure 3 Degradation curves of nitrobenzene by the hydrogel catalyst in nitrobenzene aqueous solutions with different pH values in Example 1;

[0026] Figure 4 Degradation curves of nitrobenzene by the hydrogel catalyst in nitrobenzene aqueous solutions with different hydrogen peroxide concentrations in Example 1;

[0027] Figure 5 Degradation curves of nitrobenzene by the hydrogel catalyst in nitrobenzene aqueous solutions with different catalyst dosages in Example 1;

[0028] Figure 6 Degradation curves of nitrobenzene by the hydrogel catalyst after 5 cycles of use in Example 1;

[0029] Figure 7 Solution comparison diagrams of the hydrogel catalyst before and after degrading nitrobenzene in Example 1, (a) is the solution before the reaction, and (b) is the solution after the reaction. Detailed Description of the Invention

[0030] In the present invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well-known to those skilled in the art.

[0031] The present invention provides a preparation method of a ferrocene-based hydrogel catalyst, comprising the following steps:

[0032] Mix a calcium salt and water to obtain a calcium-containing solution;

[0033] Mix alginate, ferrocene and water, and carry out thermal polymerization to obtain an alginate-ferrocene hydrogel;

[0034] Mix the alginate-ferrocene hydrogel, polyvinyl alcohol and glutaraldehyde, and carry out a first cross-linking reaction to obtain a PVA hydrogel;

[0035] Mix the calcium-containing solution and the PVA hydrogel, and carry out a second cross-linking reaction to obtain a ferrocene-based hydrogel catalyst.

[0036] In the present invention, a calcium salt and water are mixed to obtain a calcium-containing solution.

[0037] In the present invention, the calcium salt preferably includes one or two of calcium chloride and calcium sulfate. When there are two or more kinds of the above calcium salts, the present invention has no special limitation on the ratio of different kinds of calcium salts, and any ratio is acceptable.

[0038] In the present invention, the mass ratio of the calcium salt to water is preferably 1-2:90-110, more preferably 1-1.5:95-105, and still more preferably 1-1.2:98-102.

[0039] In the present invention, the temperature for mixing the calcium salt and water is preferably 15-30 °C, more preferably 20-28 °C, and still more preferably 25-27 °C; the time is preferably 10-60 min, more preferably 15-40 min, and still more preferably 20-35 min. The present invention uses the calcium salt to provide cross-linking sites for subsequent hydrogel cross-linking.

[0040] In the present invention, alginate, ferrocene and water are mixed, and thermal polymerization is carried out to obtain an alginate-ferrocene hydrogel.

[0041] In the present invention, the alginate preferably includes sodium alginate, potassium alginate or ammonium alginate, and more preferably sodium alginate.

[0042] In the present invention, the mass ratio of the alginate, ferrocene and water is preferably 2-3:2-3:50-70, more preferably 2.2-2.8:2.2-2.8:55-65, and still more preferably 2.4-2.5:2.4-2.5:60-62.

[0043] In the present invention, the temperature of the thermal polymerization is preferably 50 - 90 °C, more preferably 65 - 80 °C, and still more preferably 70 - 75 °C; the time is preferably 1 - 3 h, more preferably 1.5 - 2.5 h, and still more preferably 2 h. During the thermal polymerization process, alginate forms a hydrogel network through thermal polymerization, and at the same time, ferrocene is uniformly dispersed in the alginate single-network hydrogel. The prepared alginate-ferrocene hydrogel is denoted as Alg-Fc.

[0044] After obtaining the alginate-ferrocene hydrogel, in the present invention, the alginate-ferrocene hydrogel, polyvinyl alcohol, and glutaraldehyde are mixed to carry out the first cross-linking reaction to obtain a PVA hydrogel.

[0045] In the present invention, the mass ratio of the alginate-ferrocene hydrogel to polyvinyl alcohol is preferably 1 - 2:1.5 - 3.5, more preferably 2:2.5; the mass ratio of glutaraldehyde to polyvinyl alcohol is preferably 1 - 2:4 - 6, more preferably 1.5:5.

[0046] In the present invention, the temperature of the first cross-linking reaction is preferably 15 - 30 °C, more preferably 20 - 28 °C, and still more preferably 25 - 27 °C; the time is preferably 20 - 40 min, more preferably 25 - 35 min, and still more preferably 28 - 30 min. During the first cross-linking reaction process, PVA and glutaraldehyde achieve the construction of a polymer network by forming acetal bonds. PVA contains a large number of hydroxyl groups (-OH) and acts as a nucleophile, while glutaraldehyde contains two aldehyde groups (-CHO) and can react with hydroxyl groups under acidic or neutral conditions, enabling each glutaraldehyde molecule to connect two PVA chains to form a three-dimensional polyvinyl alcohol hydrogel network, and the alginate-ferrocene remains unchanged.

[0047] After obtaining the PVA hydrogel, in the present invention, the calcium-containing solution is mixed with the PVA hydrogel to carry out the second cross-linking reaction to obtain a ferrocene-based hydrogel catalyst.

[0048] In the present invention, the volume ratio of the PVA hydrogel to the calcium-containing solution is preferably 1:2 - 20, more preferably 1:5 - 15, and still more preferably 1:10 - 12.

[0049] In the present invention, the PVA hydrogel is preferably dropped into the calcium-containing solution. The dropping instrument is preferably a syringe, a dropper, or a separating funnel. The dropping rate is preferably 0.1 - 0.5 mL / min, more preferably 0.2 - 0.4 mL / min, and still more preferably 0.25 - 0.3 mL / min.

[0050] In the present invention, the temperature of the second cross-linking reaction is preferably 15 to 30 °C, more preferably 20 to 28 °C, and even more preferably 25 to 27 °C; the time is preferably 1 to 4 days, more preferably 2 to 3 days. During the second cross-linking reaction, the alginate group structure present in the alginate-ferrocene hydrogel forms a three-dimensional network through Ca 2+ cross-linking. Metal ions such as Na+ in the alginate are replaced by calcium ions, and then the calcium ions form coordination bonds with the carboxylate groups in the alginate to form an "egg box"-shaped network. Each Ca2+ coordinates with 4 carboxylate groups (from two different alginate chains), and the two chains form a three-dimensional grid through metal bridging, and at the same time form a double-network hydrogel structure with the PVA network.

[0051] After completing the second cross-linking reaction, the obtained cross-linked product is mixed with water and post-treated to obtain a ferrocene-based hydrogel catalyst.

[0052] In the present invention, the mass-volume ratio of the cross-linked product to water is preferably 10 to 40 g: 100 to 200 mL, more preferably 15 to 35 g: 120 to 180 mL, and even more preferably 20 to 30 g: 150 to 160 mL.

[0053] In the present invention, the post-treatment is preferably to soak the cross-linked product in water for 2 to 3 days while continuously changing the water to remove the metal ions on the surface of the hydrogel beads and prevent the metal ions on the surface from affecting the degradation experiment; the time of the post-treatment is preferably 36 to 60 h, more preferably 40 to 56 h, and even more preferably 50 to 52 h.

[0054] The present invention provides a ferrocene-based hydrogel catalyst obtained by the preparation method described in the above technical solution.

[0055] The present invention provides an application of the ferrocene-based hydrogel catalyst described in the above technical solution in the degradation of nitro compounds.

[0056] In the present invention, the nitro compound is preferably nitrobenzene.

[0057] The present invention has no special limitation on the method of the application, and it can be applied according to the methods well known in the art.

[0058] The following describes the specific embodiments of the present invention in detail, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0059] The following experimental and detection methods are all conventional methods unless otherwise specified; the following reagents and raw materials are all commercially available unless otherwise specified.

[0060] Example 1

[0061] Mix anhydrous calcium chloride and water (the mass ratio of anhydrous calcium chloride to water is 2:100), and react at 25 °C for 20 min to obtain a calcium-containing solution;

[0062] Mix sodium alginate, ferrocene and water (the mass ratio of sodium alginate, ferrocene and water is 2.4:2.4:60), and react at 70 °C for 2 h to obtain sodium alginate-ferrocene hydrogel, denoted as Alg-Fc;

[0063] Mix sodium alginate-ferrocene hydrogel, polyvinyl alcohol and glutaraldehyde (the mass ratio of sodium alginate-ferrocene hydrogel, polyvinyl alcohol and glutaraldehyde is 4:5:1.5), and react at 25 °C for 30 min to obtain PVA hydrogel;

[0064] Use a syringe to drop the PVA hydrogel into the calcium-containing solution (the volume ratio of the calcium-containing solution to the PVA hydrogel is 10:1, and the dropping rate is 0.3 mL / min), react at 25 °C for 2 days. After the reaction, mix the obtained sample with water (the mass-volume ratio of the sample to water is 30 g:200 mL), soak in water for 48 h while continuously changing water to remove metal ions on the surface of the hydrogel beads to obtain a hydrogel catalyst, denoted as PVA / Alg-Fc.

[0065] Example 2

[0066] Mix anhydrous calcium chloride and water (the mass ratio of anhydrous calcium chloride to water is 2.04:102), and react at 30 °C for 15 min to obtain a calcium-containing solution;

[0067] Mix sodium alginate, ferrocene and water (the mass ratio of sodium alginate, ferrocene and water is 2.5:2.5:62), and react at 75 °C for 1.5 h to obtain sodium alginate-ferrocene hydrogel;

[0068] Mix sodium alginate-ferrocene hydrogel, polyvinyl alcohol and glutaraldehyde (the mass ratio of sodium alginate-ferrocene hydrogel, polyvinyl alcohol and glutaraldehyde is 4:5:1.5), and react at 27 °C for 28 min to obtain PVA hydrogel;

[0069] Using a syringe, the PVA hydrogel was dropped into a calcium-containing solution (the volume ratio of the calcium-containing solution to the PVA hydrogel was 11:1, and the dropping rate was 0.4 mL / min), and the reaction was carried out at 30 °C for 2 days. After the reaction, the obtained sample was mixed with water (the mass-volume ratio of the sample to water was 35 g:160 mL), and soaked in water for 50 h while continuously changing the water to remove metal ions on the surface of the hydrogel beads, obtaining a hydrogel catalyst.

[0070] Example 3

[0071] Calcium chloride dihydrate and water (the mass ratio of calcium chloride dihydrate to water was 2.1:100) were mixed and reacted at 25 °C for 15 min to obtain a calcium-containing solution;

[0072] Sodium alginate, ferrocene and water (the mass ratio of sodium alginate, ferrocene and water was 2.4:2.4:60) were mixed and reacted at 65 °C for 2 h to obtain a sodium alginate-ferrocene hydrogel;

[0073] The sodium alginate-ferrocene hydrogel, polyvinyl alcohol and glutaraldehyde (the mass ratio of the sodium alginate-ferrocene hydrogel, polyvinyl alcohol to glutaraldehyde was 4:5:1.5) were mixed and reacted at 25 °C for 35 min to obtain a PVA hydrogel;

[0074] Using a syringe, the PVA hydrogel was dropped into a calcium-containing solution (the volume ratio of the calcium-containing solution to the PVA hydrogel was 12:1, and the dropping rate was 0.5 mL / min), and the reaction was carried out at 30 °C for 2.5 days. After the reaction, the obtained sample was mixed with water (the mass-volume ratio of the sample to water was 20 g:120 mL), and soaked in water for 52 h while continuously changing the water to remove metal ions on the surface of the hydrogel beads, obtaining a hydrogel catalyst.

[0075] Characterization and performance testing

[0076] Figure 1 SEM images (a-c, 5 μm, 500 μm and 200 μm in sequence) and EDS spectra (d-g, O, Fe, C and Ca in sequence) of the hydrogel catalyst obtained in Example 1 at different magnifications; as Figure 1 shown, for the external morphology of dry PVA / Alg-Fc, the SEM photos show that its surface is undulating with some scattered wrinkles ( Figure 1 in (c)). For the inside of the hydrogel beads, it can be clearly seen that there are abundant pores inside the hydrogel ( Figure 1 in (a)), which are dense and uneven, facilitating the transfer of substances. EDS spectrum analysis confirmed the uniformity and distribution of all elements (Fe, Ca, C and O) in the hydrogel, indicating that the catalytic sites are evenly dispersed in the crosslinked system.

[0077] Figure 2 The compressive stress-strain curves of the hydrogel catalyst obtained in Example 1 and the Alg-Fc hydrogel are shown as follows. Figure 2 It can be seen that the compressive stresses of the PVA / Alg-Fc hydrogel beads and the Alg-Fc hydrogel beads at 50% compressive strain are 309 kPa and 80 kPa respectively. This shows that adding sodium alginate Alg to the PVA network can enhance the compressive strength to a certain extent (by 3.86 times). This indicates that the double-network hydrogel beads with good mechanical properties are beneficial for long-term storage and can effectively inhibit the damage to the hydrogel beads caused by collisions in the heterogeneous Fenton reaction.

[0078] Test Example 1

[0079] The hydrogel catalyst prepared in Example 1 was applied to the treatment of water pollution by advanced oxidation technology. A Fenton system composed of the hydrogel catalyst, hydrogen peroxide, hydroxylamine hydrochloride, and water was used to catalytically degrade nitrobenzene. Nitrobenzene was configured as an aqueous solution with an initial concentration of 10 mg / L. Then, hydrogen peroxide, hydroxylamine hydrochloride, and the hydrogel catalyst were added in sequence. In the mixed system, the concentration of hydrogen peroxide was 1.6 mmol / L, the concentration of hydroxylamine hydrochloride was 2.0 mmol / L, and the concentration of the hydrogel catalyst was 576 mg / L. The temperature of catalytic degradation was room temperature. Hydrochloric acid solution or sodium hydroxide solution was added dropwise to the mixed system to adjust the pH value. The pH values were set to 1, 3, 5, 7, 9, and 11 respectively. The degradation rate of nitrobenzene within 2 h was studied, and the degradation curve of the hydrogel catalyst in Example 1 for nitrobenzene under different pH conditions was obtained. The results are as follows Figure 3 shown:

[0080] Under the conditions of pH value of 1 and system action time of 2 h, the degradation rate of nitrobenzene was 50.5%; under the conditions of pH value of 3 and system action time of 2 h, the degradation rate of nitrobenzene was 93.5%; under the conditions of pH value of 5 and system action time of 2 h, the degradation rate of nitrobenzene was 87.2%; under the conditions of pH value of 7 and system action time of 2 h, the degradation rate of nitrobenzene was 45.5%; under the conditions of pH value of 9 and system action time of 2 h, the degradation rate of nitrobenzene was 36.7%; under the conditions of pH value of 11 and system action time of 2 h, the degradation rate of nitrobenzene was 26.9%.

[0081] Test Example 2

[0082] The hydrogel catalyst prepared in Example 1 was applied to the treatment of water pollution by advanced oxidation technology. A Fenton system composed of the hydrogel catalyst, hydrogen peroxide, hydroxylamine hydrochloride, and water was used to catalytically degrade nitrobenzene. Nitrobenzene was configured into an aqueous solution with an initial concentration of 10 mg / L, and then hydrogen peroxide, hydroxylamine hydrochloride, and the hydrogel catalyst were added in sequence. In the mixed system, the concentrations of hydrogen peroxide were set to 0.8 mmol / L, 1.0 mmol / L, 1.2 mmol / L, 1.4 mmol / L, 1.6 mmol / L, 1.8 mmol / L, and 2.0 mmol / L respectively, the concentration of hydroxylamine hydrochloride was 2.0 mmol / L, the concentration of the hydrogel catalyst was 576 mg / L, the temperature of catalytic degradation was room temperature, and the pH value was 3. The degradation rate of nitrobenzene within 2 h was studied, and the degradation curve of nitrobenzene in water with different hydrogen peroxide concentrations by the hydrogel catalyst obtained in Example 1 was obtained. The results are as Figure 4 shown: Under the condition that the concentration of hydrogen peroxide was 0.8 mmol / L and the system reaction time was 2 h, the degradation rate of nitrobenzene was 79.2%; under the condition that the concentration of hydrogen peroxide was 1.0 mmol / L and the system reaction time was 2 h, the degradation rate of nitrobenzene was 83.6%; under the condition that the concentration of hydrogen peroxide was 1.2 mmol / L and the system reaction time was 2 h, the degradation rate of nitrobenzene was 88.8%; under the condition that the concentration of hydrogen peroxide was 1.4 mmol / L and the system reaction time was 2 h, the degradation rate of nitrobenzene was 89.3%; under the condition that the concentration of hydrogen peroxide was 1.6 mmol / L and the system reaction time was 2 h, the degradation rate of nitrobenzene was 93.5%; under the condition that the concentration of hydrogen peroxide was 1.8 mmol / L and the system reaction time was 2 h, the degradation rate of nitrobenzene was 93.7%; under the condition that the concentration of hydrogen peroxide was 2.0 mmol / L and the system reaction time was 2 h, the degradation rate of nitrobenzene was 94.0%.

[0083] Test Example 3

[0084] The hydrogel catalyst prepared in Example 1 was applied to the treatment of water pollution by advanced oxidation technology. A Fenton system composed of the hydrogel catalyst, hydrogen peroxide, hydroxylamine hydrochloride, and water was used to catalytically degrade nitrobenzene. Nitrobenzene was configured into an aqueous solution with an initial concentration of 10 mg / L, and then hydrogen peroxide, hydroxylamine hydrochloride, and the hydrogel catalyst were added in sequence. In the mixed system, the concentration of hydrogen peroxide was 1.6 mmol / L, the concentration of hydroxylamine hydrochloride was 2.0 mmol / L, and the concentrations of the hydrogel catalyst were set to 288 mg / L, 432 mg / L, 576 mg / L, 720 mg / L, and 864 mg / L respectively. The temperature of catalytic degradation was room temperature, and the pH value was 3. The degradation rate of nitrobenzene within 2 h was studied, and the degradation curve of nitrobenzene in water with different catalyst concentrations by the hydrogel catalyst obtained in Example 1 was obtained. The results are as Figure 5As shown; under the conditions of a catalyst concentration of 288 mg / L and a system action time of 2 h, the degradation rate of nitrobenzene is 88.2%; under the conditions of a catalyst concentration of 432 mg / L and a system action time of 2 h, the degradation rate of nitrobenzene is 89.1%; under the conditions of a catalyst concentration of 576 mg / L and a system action time of 2 h, the degradation rate of nitrobenzene is 93.5%; under the conditions of a catalyst concentration of 720 mg / L and a system action time of 2 h, the degradation rate of nitrobenzene is 90.6%; under the conditions of a catalyst concentration of 864 mg / L and a system action time of 2 h, the degradation rate of nitrobenzene is 92.0%.

[0085] The hydrogel catalyst prepared in Example 2 was applied to the treatment of water pollution by advanced oxidation technology. The hydrogel catalyst, hydrogen peroxide, hydroxylamine hydrochloride and water were combined to form a Fenton system for catalytic degradation of nitrobenzene. Nitrobenzene was configured into an aqueous solution with an initial concentration of 10 mg / L, and then hydrogen peroxide, hydroxylamine hydrochloride and the hydrogel catalyst were added in sequence. In the mixed system, the concentration of hydrogen peroxide was 1.6 mmol / L, the concentration of hydroxylamine hydrochloride was 2.0 mmol / L, the concentration of the hydrogel catalyst was 576 mg / L, the temperature of catalytic degradation was room temperature, and the pH value was 3. The degradation rate of nitrobenzene by the hydrogel catalyst in this example was 92.6%.

[0086] The hydrogel catalyst prepared in Example 3 was applied to the treatment of water pollution by advanced oxidation technology. The hydrogel catalyst, hydrogen peroxide, hydroxylamine hydrochloride and water were combined to form a Fenton system for catalytic degradation of nitrobenzene. Nitrobenzene was configured into an aqueous solution with an initial concentration of 10 mg / L, and then hydrogen peroxide, hydroxylamine hydrochloride and the hydrogel catalyst were added in sequence. In the mixed system, the concentration of hydrogen peroxide was 1.6 mmol / L, the concentration of hydroxylamine hydrochloride was 2.0 mmol / L, the concentration of the hydrogel catalyst was 576 mg / L, the temperature of catalytic degradation was room temperature, and the pH value was 3. The degradation rate of nitrobenzene by the hydrogel catalyst in this example was 93.0%.

[0087] It can be seen from the above examples that the hydrogel catalyst prepared by the present invention has advantages such as high mechanical strength and environmental friendliness. When it is applied to the catalytic degradation of nitrobenzene, under the conditions of a nitrobenzene concentration of 10 mg / L, a pH value of 3, and a system action time of 2 h, the degradation rate of nitrobenzene is as high as 93.5%.

[0088] Figure 6 It is the degradation curve graph of the hydrogel catalyst in Example 1 after 5 cycles of use. The degradation conditions are: the initial concentration of nitrobenzene is 10 mg / L, the concentration of hydrogen peroxide is 1.6 mmol / L, the concentration of hydroxylamine hydrochloride is 2.0 mmol / L, the concentration of the hydrogel catalyst is 576 mg / L, the temperature of catalytic degradation is room temperature, and the pH value is 3; asFigure 6 As shown, during the cyclic experiment, the degradation rate remained consistent, thus proving that ferrocene as the reaction center did not suffer any loss.

[0089] Figure 7 Figure for comparing the solutions before and after the degradation of nitrobenzene by the hydrogel catalyst in Example 1. (a) is the solution before the reaction, and (b) is the solution after the reaction. The degradation conditions are as follows: the initial concentration of nitrobenzene is 10 mg / L, the concentration of hydrogen peroxide is 1.6 mmol / L, the concentration of hydroxylamine hydrochloride is 2.0 mmol / L, the concentration of the hydrogel catalyst is 576 mg / L, the temperature for catalytic degradation is room temperature, and the pH value is 3. As Figure 7 shown, no ferrocene suspension appeared in the solution before and after degradation, indicating that ferrocene did not leak out of the hydrogel beads, which means that ferrocene was immobilized in the hydrogel beads.

[0090] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a ferrocene-based hydrogel catalyst, characterized in that, The following steps are involved: Mixing calcium salt and water to obtain a calcium solution; alginate, ferrocene and water are mixed and thermally polymerized to obtain alginate-ferrocene hydrogel; mixing the alginate-ferrocene hydrogel, polyvinyl alcohol and glutaraldehyde, and performing a first cross-linking reaction to obtain a PVA hydrogel; The calcium-containing solution is mixed with the PVA hydrogel to perform a second cross-linking reaction to obtain a ferrocene-based hydrogel catalyst.

2. The preparation method according to claim 1, wherein The calcium salt includes one or both of calcium chloride and calcium sulfate.

3. The preparation method according to claim 2, characterized in that, The mass ratio of the calcium salt to water is 1-2:90-110.

4. The preparation method according to claim 3, characterized in that, The temperature of mixing the calcium salt and water is 15-30° C. and the time is 10-60 minutes.

5. The preparation method according to claim 4, characterized in that The alginate includes sodium alginate, potassium alginate or ammonium alginate; the mass ratio of the alginate, ferrocene and water is 2-3:2-3:50-70.

6. The preparation method according to claim 5, characterized in that, The temperature of the thermal polymerization is 50-90° C., and the time is 1-3 hours.

7. The preparation method according to claim 6, characterized in that The mass ratio of the alginate-ferrocene hydrogel to polyvinyl alcohol is 1-2:1.5-3.5; the mass ratio of the glutaraldehyde to polyvinyl alcohol is 1-2:4-6; the temperature of the first cross-linking reaction is 15-30° C., and the time is 20-40 minutes.

8. The preparation method according to claim 7, characterized in that The volume ratio of the PVA hydrogel to the calcium-containing solution is 1:2-20; the temperature of the second cross-linking reaction is 15-30° C., and the time is 1-4 days.

9. The ferrocene-based hydrogel catalyst obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the ferrocenyl hydrogel catalyst according to claim 9 in the degradation of nitro compounds.

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