Fe-Mo bimetallic catalyst with chitosan as carbon skeleton and preparation method and application thereof

Abstract

The invention provides a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton and a preparation method and application thereof, and belongs to the technical field of wastewater treatment catalyst preparation. Chitosan is used as a carbon base material, metal ions are wrapped in chitosan beads, M-N and C-N bonds are formed by amino functional groups of a chitosan structure and transition metal, a large number of active sites can be provided after calcination, and explosive and powder components in wastewater can be rapidly degraded. The Fe-Mo bimetallic catalyst with the chitosan as the carbon skeleton is simple in preparation process and not harsh in use condition, catalytic degradation can be carried out only by putting the Fe-Mo bimetallic catalyst and hydrogen peroxide into wastewater together, and the Fe-Mo bimetallic catalyst can be recycled by adding a common magnet into the degraded wastewater, so that reutilization is realized. The research provides an alternative scheme for solving the problems that a photocatalyst preparation process is tedious, the raw material cost is high, industrial application is difficult to realize and the like in an existing explosive and powder wastewater degradation treatment technology, and has important practical significance.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment catalyst preparation, in particular to an Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton, and a preparation method and application thereof. Background Art

[0002] The explosives industry is also a serious source of environmental pollution. With increasingly stringent environmental regulations, explosives are characterized by high energy consumption, significant pollution, and high risk in all aspects of their development, production, use, and waste disposal, hindering the healthy development of the industry. This is particularly true of the disposal of used explosives, which is not only extremely dangerous but also causes environmental pollution. Therefore, the development of green treatment technologies is imperative. During the explosives production process, certain stages produce explosives-containing wastewater components. These components include, but are not limited to, nitrobenzene compounds such as octogenins (HMX), hexachlorobenzene (RDX), 2,4-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT).

[0003] HMX is a high explosive used in a variety of military and other applications, including nuclear devices, rocket propellants, plastic explosives, rocket fuel, detonators, construction, quarrying, and mining. The indiscriminate disposal of HMX waste from production sites, blast sites, and unexploded ordnance has led to significant contamination of soil and water bodies. Therefore, there is a need to develop alternative processes to remove HMX from water bodies.

[0004] Currently, advanced oxidation technologies (AOPs) are being used to replace traditional treatment methods (such as adsorption and incineration) to ensure more efficient degradation and mineralization of octoquinone and nitrobenzene compounds in water. This requires the development of an efficient heterogeneous Fenton catalyst to promote the catalytic degradation of octoquinone and nitrobenzene compounds in water. Advanced oxidation technologies (AOPs) are becoming increasingly important due to their potential effectiveness in treating organic pollutants, especially those that are resistant to biodegradation. Advanced oxidation technologies include various chemical catalysis, photocatalysis, electrocatalysis, and Fenton oxidation methods. As an environmentally friendly and low-cost oxidation method, Fenton technology has unique characteristics, including high degradation efficiency, simple operation, and mild reaction conditions.

[0005] Existing technologies for degrading explosives wastewater primarily rely on photocatalysis, but photocatalytic reactions are conditional and require the presence of a specific light source to function. Furthermore, the complex preparation process for existing photocatalysts and the high cost of raw materials contribute to high overall costs, making industrialization and economic value creation difficult.

[0006] Chitosan, a natural cationic polysaccharide, has an annual production of hundreds of millions of tons. Unlike other polysaccharides, chitosan has a large number of amino and hydroxyl groups on its long chains, which allows it to undergo oxidation, acylation, and alkylation reactions. Chitosan contains a large number of amino groups, which can form MN and CN bonds with transition metals. Furthermore, after freeze-drying and calcination, chitosan-derived carbon has a high specific surface area, making it an ideal heterogeneous Fenton catalyst support. Therefore, the synthesis and preparation of chitosan-derived carbon-based catalysts have certain practical significance and economic value.

[0007] Li Wenbin (application number 202311536706.5) and others used activated carbon as raw material, stirred activated carbon and chitosan solutions, added iron compounds and silver compounds to the solution, and finally alkalized it to obtain gel particles. After a series of treatments and calcination, chitosan-coated iron / silver-loaded activated carbon composite spheres were obtained. The carbon composite spheres prepared by this preparation method only have an adsorption function for pollutants and are used for the adsorption of heavy metals, but have no catalytic function for organic pollutants in water.

[0008] Wei Zhixian (application number 201210241343.3) et al. used lanthanum nitrate, strontium carbonate, manganese chloride, tetrabutyl titanate and stearic acid as raw materials, and obtained the catalyst La after a series of treatments. 0.8 Sr 0.2 Mn 1-x Ti x O 3-δ The powder can degrade HMX-containing wastewater when irradiated with light at a certain intensity. This preparation method involves multiple high-temperature treatment steps, resulting in high synthesis costs and difficulty in recycling the powdered catalyst.

[0009] Wang Jie and others (application number 201310146709.8) prepared magnetically loaded nanoparticles of TiO2 / SiO2 / C / Fe3O4 and added them to explosives wastewater in appropriate proportions. They then photocatalytically degraded the wastewater under ultraviolet light. However, this material has limited reaction conditions, requiring only ultraviolet light, and the degradation rate was low, at only 63.24%.

[0010] Sun Xiaofeng (202310633717.9) and others prepared a photocatalyst α-Fe2O3 / RGO / mpg-C3N4 nanocomposite. This catalyst has the advantages of large specific surface area, visible light response, and non-toxicity and environmental protection. However, the catalyst preparation process is complex, with two key steps involving high temperature and hydrothermal reactions, which is time-consuming and difficult to industrialize. Summary of the Invention

[0011] The purpose of the present invention is to provide a Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton and its preparation method and application, so as to solve the above technical problems.

[0012] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0013] The present invention provides a method for preparing an Fe-Mo bimetallic catalyst using chitosan as a carbon skeleton, comprising the following steps:

[0014] Step 1), mixing an iron salt solution, a molybdenum salt solution and a chitosan solution, and then adding anhydrous acetic acid to obtain a chitosan / metal ion solution;

[0015] Step 2) adding the chitosan / metal ion solution dropwise to a sodium hydroxide solution and allowing to stand and cross-link to obtain chitosan beads, which are then washed, freeze-dried, and heat-treated in sequence to obtain a Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton.

[0016] Furthermore, in step 1), the iron salt solution includes FeCl2·4H2O solution, and the molybdenum salt solution includes (NH4)6Mo7O 24 ·4H2O solution;

[0017] The concentration of the iron salt solution is 0.05-0.5M, and the atomic ratio of the molybdenum element in the molybdenum salt solution to the iron element in the iron salt solution is 1:1-10;

[0018] In the chitosan solution, the mass volume ratio of chitosan to water is 1g:30-100mL.

[0019] Furthermore, in step 1), the volume of the anhydrous acetic acid is 1 to 3% of the total volume of the iron salt solution, the molybdenum salt solution and the chitosan solution;

[0020] The mixing is carried out during stirring at a stirring speed of 100 to 150 rpm and a stirring time of 2 to 5 hours.

[0021] Furthermore, in step 1), the chitosan / metal ion solution is further subjected to ultrasonic treatment to remove bubbles, wherein the ultrasonic frequency is 30 to 50 kHz and the ultrasonic time is 0.5 to 1.5 h.

[0022] Furthermore, in step 2), the concentration of the sodium hydroxide solution is 1 to 2 mol / L.

[0023] Furthermore, in step 2), the freeze-drying temperature is -25 to -40°C, and the freeze-drying time is 24 to 36 hours.

[0024] Furthermore, in step 2), the heat treatment temperature is 500-900°C, the time is 1.5-3h, and the heating rate is 8-12°C / min;

[0025] The heat treatment is carried out under N2 protection.

[0026] The present invention provides an Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton, which is prepared by the above-mentioned preparation method, with chitosan as the carbon skeleton and Fe and Mo elements as active components;

[0027] The atomic ratio of Fe to Mo is 1 to 10:1.

[0028] The present invention also provides an application of a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton in degrading explosive wastewater, wherein the Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton and H2O2 solution are added to the explosive wastewater.

[0029] Furthermore, the ratio of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton to H2O2 is 1kg:200-400mL, and the ratio of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton to explosive wastewater is 1kg:1000-1500L;

[0030] The concentration of explosive components in the explosive wastewater is 20-50 mg / L;

[0031] The volume concentration of the H2O2 solution is 28-35%;

[0032] The explosive components include one or more of octogenin, hexachlorobenzene and nitrobenzene compounds.

[0033] Beneficial effects of the present invention:

[0034] This invention utilizes the amino groups in the chitosan structure to form M-N and C-N bonds with transition metals, providing a large number of active sites after calcination. The introduction of molybdenum facilitates the rapid degradation of octogenins in wastewater. The invention also incorporates magnetic properties, which facilitate the Fenton reaction between iron ions and hydrogen peroxide, improving the catalyst's reusability and catalytic degradation efficiency.

[0035] The carbon substrate used in the present invention is chitosan, which is a cheap raw material and is conducive to large-scale industrialization. Titration of the chitosan solution in an alkaline solution for cross-linking can greatly improve the utilization rate of metal ions, and most of the metal ions are wrapped by the cross-linked chitosan beads. The present invention introduces a freeze-drying procedure in the processing step. The beads after freeze-drying have rich pore structure and large specific surface area. A porous carbon skeleton is formed when the material is carbonized at high temperature, which is an innovation in materials. The carbon nanotubes generated on the surface of the beads after high-temperature carbonization are conducive to improving the degradation efficiency. The preparation method of the present invention has a simple process, and only the last step involves high temperature, which is easy to prepare on an industrial scale.

[0036] The catalyst obtained by the present invention is used to catalyze the degradation of octogenins, hexogenins, and nitrobenzene compounds in wastewater. The use conditions are not harsh and there are no special requirements. It only needs to be added to the wastewater while hydrogen peroxide is used to generate hydroxyl radicals, which is environmentally friendly. In addition, the catalyst prepared by the present invention is a magnetic carbon material and can be recovered by adding an ordinary magnet to the degraded wastewater. The separated catalyst can be added to the next batch of wastewater to be treated for reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of the preparation method of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton of the present invention;

[0038] Figure 2 Fe obtained in Example 2 2.5 SEM images of Mo / CNTs;

[0039] Figure 3 The XRD curves of the Fe-Mo bimetallic catalysts with chitosan as the carbon skeleton prepared in Examples 1 to 4 respectively;

[0040] Figure 4 The VSM curves of the Fe-Mo bimetallic catalysts with chitosan as the carbon skeleton prepared in Examples 1 to 4 respectively;

[0041] Figure 5 The liquid chromatography spectra of HMX under different catalytic oxidation degradation times of Fe-Mo bimetallic catalysts with chitosan as carbon skeleton prepared in Examples 1 to 4 respectively;

[0042] Figure 6 Schematic diagram of the degradation effect of Fe-Mo bimetallic catalyst with chitosan as carbon skeleton prepared in Examples 1 to 4 on HMX wastewater;

[0043] Figure 7 Fe prepared in Example 2 2.5 Schematic diagram of the number of reuses and removal rates of Mo / CNTs catalytic degradation of HMX wastewater, as well as the loss of iron and molybdenum during use;

[0044] Figure 8 Fe prepared in Example 2 2.5 Schematic diagram of the removal efficiency of Mo / CNTs for HMX (octogenin), RDX (hexachlorobenzene) and DNT (2,4-dinitrotoluene). DETAILED DESCRIPTION

[0045] The present invention provides a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton, a preparation method and application thereof, which are used to solve the above technical problems.

[0046] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0047] The present invention provides a method for preparing an Fe-Mo bimetallic catalyst using chitosan as a carbon skeleton, comprising the following steps:

[0048] Step 1), mixing an iron salt solution, a molybdenum salt solution and a chitosan solution, and then adding anhydrous acetic acid to obtain a chitosan / metal ion solution;

[0049] Step 2) adding the chitosan / metal ion solution dropwise to a sodium hydroxide solution and allowing to stand and cross-link to obtain chitosan beads, which are then washed, freeze-dried, and heat-treated in sequence to obtain a Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton.

[0050] In the present invention, in step 2), adding the chitosan / metal ion solution dropwise to the sodium hydroxide solution can greatly improve the utilization efficiency of the metal ions.

[0051] In the present invention, in step 1), the iron salt solution is preferably FeCl2·4H2O solution, and the molybdenum salt solution is preferably (NH4)6Mo7O 24 ·4H2O solution;

[0052] The concentration of the iron salt solution is 0.05-0.5M, preferably 0.05-0.3M, more preferably 0.1M, and the atomic ratio of the molybdenum element in the molybdenum salt solution to the iron element in the iron salt solution is 1:1-10, preferably 1:2.5-8, more preferably 1:5;

[0053] In the chitosan solution, the mass volume ratio of chitosan to water is 1 g:30-100 mL, preferably 1 g:50-80 mL, and more preferably 1 g:60 mL.

[0054] In the present invention, in step 1), the volume of the anhydrous acetic acid is 1 to 3% of the total volume of the iron salt solution, the molybdenum salt solution and the chitosan solution, preferably 2%;

[0055] The mixing is carried out during stirring at a stirring speed of 100 to 150 rpm, preferably 120 rpm, and for a stirring time of 2 to 5 hours, preferably 3 hours.

[0056] In the present invention, the role of anhydrous acetic acid is to aid dissolution.

[0057] In the present invention, in step 1), the chitosan / metal ion solution is further subjected to ultrasonic treatment to remove bubbles, the ultrasonic frequency is 30 to 50 kHz, preferably 40 kHz, and the ultrasonic time is 0.5 to 1.5 h, preferably 1 h.

[0058] In the present invention, in step 2), the concentration of the sodium hydroxide solution is 1 to 2 mol / L, preferably 1.5 mol / L.

[0059] In the present invention, in step 2), the chitosan beads are washed with deionized water until the pH of the washing solution is between 6 and 8.

[0060] In the present invention, in step 2), the freeze-drying temperature is -25 to -40°C, preferably -30°C, and the freeze-drying time is 24 to 36 hours, preferably 28 to 32 hours, and more preferably 30 hours.

[0061] In the present invention, in step 2), the heat treatment temperature is 500-900°C, preferably 600-800°C, more preferably 700°C, the time is 1.5-3h, preferably 2h, and the heating rate is 8-12°C / min, preferably 10°C / min;

[0062] The heat treatment is carried out under N2 protection.

[0063] In the present invention, after the heat treatment is completed, the mixture is naturally cooled to room temperature.

[0064] In the present invention, the freeze-dried chitosan beads have rich pore structures and large specific surface area. After a high-temperature carbonization process of heat treatment, carbon nanotubes are generated on the surface of the beads to form a porous carbon skeleton. The presence of carbon nanotubes is conducive to improving the degradation efficiency.

[0065] The present invention provides an Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton, which is prepared by the above-mentioned preparation method, with chitosan as the carbon skeleton and Fe and Mo elements as active components;

[0066] The atomic ratio of Fe to Mo is 1 to 10:1.

[0067] In the present invention, the atomic ratio of Fe to Mo is preferably 2.5 to 5:1, more preferably 2.5:1.

[0068] The present invention also provides an application of a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton in degrading explosive wastewater, wherein the Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton and H2O2 solution are added to the explosive wastewater.

[0069] In the present invention, H2O2 is used to generate hydroxyl radicals.

[0070] In the present invention, the ratio of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton to the H2O2 solution is 1kg:200-400mL, preferably 1kg:300mL; the ratio of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton to the explosive wastewater is 1kg:1000-1500L, preferably 1kg:1200-1400L, and further preferably 1kg:1300L;

[0071] The concentration of explosive components in the explosive wastewater is 20-50 mg / L, preferably 30-40 mg / L, and more preferably 35 mg / L.

[0072] The volume concentration of the H2O2 solution is 28-35%, preferably 30%;

[0073] The explosive component includes one or more of octogenin, hexogenin and nitrobenzene compounds, preferably octogenin and / or nitrobenzene compounds, and more preferably octogenin and nitrobenzene compounds.

[0074] In the present invention, the nitrobenzene compounds include 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT).

[0075] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0076] Example 1

[0077] Mix 4.5 g chitosan with 50 mL distilled water and stir at 120 rpm. Take 50 mL of 0.1 M FeCl2·4H2O solution and 50 mL of (NH4)6Mo7O 24 ·4H2O solution was poured into the chitosan solution respectively to make the atomic ratio of Fe and Mo 1:1. Then 1.5 mL of anhydrous acetic acid was added to dissolve it. After stirring for 2 h to obtain the chitosan / metal ion solution, the solution was ultrasonicated at a frequency of 40 kHz for 0.5 h to remove bubbles.

[0078] The sonicated chitosan / metal ion solution was aspirated with a syringe and added dropwise to 400 mL of 1.5 mol / L NaOH solution. The solution was then allowed to stand for 24 hours to crosslink into chitosan beads. The fully crosslinked chitosan beads were then rinsed with deionized water. After the pH of the rinse solution was measured to be 7, the beads were freeze-dried at -30°C for 24 hours. The chitosan beads were then spread flat on a quartz boat and heat-treated at 800°C under nitrogen at a rate of 10°C / min for 2 hours. After cooling to room temperature, the resulting Fe-Mo bimetallic catalyst with a chitosan carbon skeleton was obtained, designated FeMo / CNTs.

[0079] At 25°C, 1g of a chitosan-based Fe-Mo bimetallic catalyst was added to 1L of wastewater containing 20mg / L of HMX. Simultaneously, 2mL of a 30% H2O2 solution was added for oxidative degradation. After 180 minutes, the HMX degradation rate reached 86.27%.

[0080] Example 2

[0081] Different from Example 1, in this example, the atomic ratio of Fe to Mo is 2.5:1, and the obtained Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton is denoted as Fe 2.5 Mo / CNTs.

[0082] At 25°C, 1g of a chitosan-based Fe-Mo bimetallic catalyst was added to 1L of wastewater containing 20mg / L of HMX. Simultaneously, 2mL of a 30% H2O2 solution was added for oxidative degradation. After 180 minutes, the HMX degradation rate reached 96.09%.

[0083] Example 3

[0084] Different from Example 1, in this example, the atomic ratio of Fe to Mo is 5:1, and the obtained Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton is recorded as Fe5Mo / CNTs.

[0085] At 25°C, 1g of a chitosan-based Fe-Mo bimetallic catalyst was added to 1L of wastewater containing 20mg / L of HMX. Simultaneously, 2mL of a 30% H2O2 solution was added for oxidative degradation. After 180 minutes, the HMX degradation rate reached 89.02%.

[0086] Example 4

[0087] Different from Example 1, in this example, the atomic ratio of Fe to Mo is 10:1, and the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton is obtained, which is denoted as Fe 10 Mo / CNTs.

[0088] At 25°C, 1g of a chitosan-based Fe-Mo bimetallic catalyst was added to 1L of wastewater containing 20mg / L of HMX. Simultaneously, 2mL of a 30% H2O2 solution was added for oxidative degradation. After 180 minutes, the HMX degradation rate reached 84.35%.

[0089] Example 5

[0090] Mix 5 g of chitosan with 30 mL of distilled water and stir at 100 rpm. Take 50 mL of 0.1 M FeCl2·4H2O solution and 50 mL of (NH4)6Mo7O 24 ·4H2O solution was poured into the chitosan solution respectively to make the atomic ratio of Fe and Mo 1:1. Then 2 mL of anhydrous acetic acid was added to dissolve it. After stirring for 2 h to obtain the chitosan / metal ion solution, the solution was ultrasonicated at a frequency of 30 kHz for 0.5 h to remove bubbles.

[0091] The chitosan / metal ion solution, after sonication, was aspirated with a syringe and added dropwise to 400 mL of 1 mol / L NaOH solution. The solution was then allowed to stand for 36 hours to crosslink into chitosan beads. The fully crosslinked chitosan beads were then rinsed with deionized water. After the pH of the rinse solution was measured to be 7, the beads were freeze-dried at -20°C for 30 hours. The chitosan beads were then spread flat on a quartz boat and heat-treated at 500°C under nitrogen at a rate of 8°C / min for 3 hours. After cooling to room temperature, the resulting Fe-Mo bimetallic catalyst with a chitosan carbon skeleton was obtained.

[0092] Example 6

[0093] Mix 6 g of chitosan with 80 mL of distilled water and stir at 150 rpm. Take 50 mL of 0.1 M FeCl2·4H2O solution and 50 mL of (NH4)6Mo7O 24 ·4H2O solution was poured into the chitosan solution respectively to make the atomic ratio of Fe and Mo 1:1. Then 3 mL of anhydrous acetic acid was added to dissolve it. After stirring for 2 h to obtain the chitosan / metal ion solution, the solution was ultrasonicated at a frequency of 50 kHz for 1.5 h to remove bubbles.

[0094] The chitosan / metal ion solution, after sonication, was aspirated with a syringe and added dropwise to 400 mL of 2 mol / L NaOH solution. The solution was then allowed to stand for 30 hours to crosslink into chitosan beads. The fully crosslinked chitosan beads were then rinsed with deionized water. After the pH of the rinse solution was measured to be 7, the beads were freeze-dried at -50°C for 36 hours. The chitosan beads were then spread flat on a quartz boat and heat-treated at 900°C under nitrogen at a rate of 12°C / min for 3 hours. After cooling to room temperature, the resulting Fe-Mo bimetallic catalyst with a chitosan carbon skeleton was obtained.

[0095] It can be seen from the above examples that the present invention provides a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton, and a preparation method and application thereof. Figure 2 Fe obtained in Example 2 2.5The SEM image of Mo / CNTs shows that the freeze-dried pellets have a rich porosity and a large specific surface area. High-temperature carbonization of the material forms a porous carbon skeleton. Carbon nanotubes form on the surface of the pellets after high-temperature carbonization, which contributes to improved degradation efficiency.

[0096] Figure 3 The XRD curves of the Fe-Mo bimetallic catalysts with chitosan as the carbon skeleton prepared in Examples 1 to 4 respectively show that the characteristic peaks at 2θ=44.673°, 65.021°, and 82.333° correspond to the (110), (200), and (211) crystal planes of the Fe structure. The above diffraction peaks are obtained from the standard PDF card PDF#06-0696 of Fe. Characteristic peaks at 2θ=26.41°, 29.513°, 35.233°, 39.798°, 40.632°, 42.879°, 43.742°, 45.861°, 48.398°, 49.115°, 51.813°, 54.398°, 58.398°, 61.26°, 70.824°, 77.901°, 78.592°, 83.547°, 86.179°, 88.129° The diffraction peaks correspond to the (020), (111), (200), (002), (201), (211), (102), (112), (022), (221), (122), (230), (231), (222), (123), (401), (133), (341), (303), and (430) crystal planes of the Fe3C structure. These diffraction peaks were obtained from the standard PDF card PDF#35-0772 of Fe3C. These results indicate that the composite material was successfully synthesized.

[0097] Figure 4 The VSM curves of the Fe-Mo bimetallic catalysts with chitosan as the carbon skeleton prepared in Examples 1 to 4 respectively show that the magnetic saturation intensity of the material obtained in the present invention is 49.67 emu / g, indicating that it has strong magnetism and is easy to separate from the solution.

[0098] Figure 5 Fe prepared in Example 2 2.5 Liquid chromatography spectra of HMX under different catalytic oxidation degradation times of Mo / CNTs catalyst. It can be seen from the figure that the catalyst material prepared by the present invention has significant degradation ability for HMX.

[0099] Figure 6Schematic diagram of the degradation effect of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton on HMX wastewater prepared in Examples 1 to 4. It can be seen from the figure that under the condition of a reaction temperature of 25°C, when the HMX content in the wastewater is 20 mg / L, the catalyst dosage is 1 g / L, and the hydrogen peroxide concentration is 20 mM, the degradation result is the best when Fe:Mo=2.5:1.

[0100] Figure 7 Fe prepared in Example 2 2.5 The figure shows the number of reuses and removal rate of the Mo / CNTs catalyst for catalytic degradation of HMX wastewater, as well as a schematic diagram of the loss of iron and molybdenum elements during use. As can be seen from the figure, the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton of the present invention has excellent catalytic degradation effect. At the same time, the introduction of magnetism facilitates the Fenton reaction between iron ions and hydrogen peroxide, thereby improving the reusability and catalytic degradation efficiency of the catalyst.

[0101] Figure 8 Fe prepared in Example 2 2.5 A schematic diagram shows the removal efficiency of the Mo / CNTs catalyst for HMX (octogenin), RDX (hexachlorobenzene), and DNT (2,4-dinitrotoluene). The figure demonstrates that the catalyst material of the present invention exhibits excellent catalytic degradation of HMX, DNT, and nitrobenzene, components of explosives. This demonstrates the simple preparation process, low cost, and non-rigid operating conditions of the Fe-Mo bimetallic catalyst with a chitosan carbon skeleton. This catalyst is highly recyclable and has important implications for the green and efficient catalytic degradation of explosives in wastewater.

[0102] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton, characterized in that: The following steps are involved: Step 1), mixing an iron salt solution, a molybdenum salt solution and a chitosan solution, and then adding anhydrous acetic acid to obtain a chitosan / metal ion solution; Step 2) adding the chitosan / metal ion solution dropwise to a sodium hydroxide solution and allowing to stand and cross-link to obtain chitosan beads, which are then washed, freeze-dried, and heat-treated in sequence to obtain a Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton.

2. The method for preparing a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton according to claim 1, characterized in that: In step 1), the iron salt solution includes FeCl2·4H2O solution, and the molybdenum salt solution includes (NH4)6Mo7O 24 ·4H2O solution; The concentration of the iron salt solution is 0.05-0.5M, and the atomic ratio of the molybdenum element in the molybdenum salt solution to the iron element in the iron salt solution is 1:1-10; In the chitosan solution, the mass volume ratio of chitosan to water is 1g:30-100mL.

3. The method for preparing a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton according to claim 1 or 2, characterized in that: In step 1), the volume of the anhydrous acetic acid is 1 to 3% of the total volume of the iron salt solution, the molybdenum salt solution and the chitosan solution; The mixing is carried out during stirring at a stirring speed of 100 to 150 rpm and a stirring time of 2 to 5 hours.

4. The method for preparing a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton according to claim 1, characterized in that: In step 1), the chitosan / metal ion solution is further subjected to ultrasonic treatment to remove bubbles, wherein the ultrasonic frequency is 30 to 50 kHz and the ultrasonic time is 0.5 to 1.5 hours.

5. The method for preparing a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton according to claim 4, characterized in that: In step 2), the concentration of the sodium hydroxide solution is 1-2 mol / L.

6. The method for preparing a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton according to claim 1, 4 or 5, characterized in that: In step 2), the freeze-drying temperature is -25 to -40°C, and the freeze-drying time is 24 to 36 hours.

7. The method for preparing a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton according to claim 6, characterized in that: In step 2), the heat treatment temperature is 500-900°C, the time is 1.5-3h, and the heating rate is 8-12°C / min; The heat treatment is carried out under N2 protection.

8. The Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton prepared by the preparation method according to any one of claims 1 to 7, characterized in that: Chitosan is used as the carbon skeleton and Fe and Mo elements are used as active components; The atomic ratio of Fe to Mo is 1 to 10:

1.

9. The use of a Fe-Mo bimetallic catalyst with chitosan as a carbon skeleton in degrading explosive wastewater according to claim 8, characterized in that: The Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton and H2O2 solution are added into the explosive wastewater.

10. The use of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton in degrading explosive wastewater according to claim 9, characterized in that: The ratio of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton to the H2O2 solution is 1kg: 200-400mL, and the ratio of the Fe-Mo bimetallic catalyst with chitosan as the carbon skeleton to the explosive wastewater is 1kg: 1000-1500L; The concentration of explosive components in the explosive wastewater is 20-50 mg / L; The volume concentration of the H2O2 solution is 28-35%; The explosive components include one or more of octogenin, hexachlorobenzene and nitrobenzene compounds.

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