Preparation method of multi-walled carbon tube confinement loaded iron oxide heterogeneous Fenton catalytic material

Abstract

The invention discloses a method for preparing a heterogeneous Fenton catalytic material by loading iron oxide in a limited range of a multi-walled carbon tube. The method comprises the steps of selection and pretreatment of the carbon tube, preparation of an iron precursor, preparation of a Fe2O3 (at) m-CNT mixture, preparation of a Fe2O3 (at) m-CNT catalytic material and the like. The iron-carbon material with a good H2O2 catalytic effect under the neutral condition is prepared, the obtained material can catalyze H2O2 under the neutral condition to generate reactive oxygen species (ROS) and perform deep oxidative degradation on organic matters, and the catalytic material can be reused after being filtered and precipitated, so that the generation of a large amount of iron sludge after traditional Fenton oxidation is avoided, and the production cost is reduced. The catalytic material prepared by the method is low in production cost, convenient to use, reusable, free of secondary pollution and remarkable in organic matter catalytic degradation capacity.

Description

Technical Field

[0001] The present invention belongs to the field of preparing novel Fenton advanced oxidation catalytic materials in sewage treatment technology, and particularly relates to a preparation method of a heterogeneous Fenton catalytic material with multi-walled carbon nanotubes confining and loading iron oxides. Background Art

[0002] The traditional Fenton advanced oxidation technology is a commonly used process for advanced sewage treatment at present, but two major defects limit its practical application. First, the traditional Fenton advanced oxidation has a strong proton dependence, that is, ferrous ions have catalytic effect only under strong acidic conditions (pH < 3.5), resulting in the need to adjust the pH value of sewage by adding acid before entering the Fenton oxidation system, and adding caustic soda to adjust the pH value back to neutral after treatment. The operation is cumbersome, and the consumption of chemical agents such as acid and alkali is large, which does not meet the current realistic needs of energy conservation and emission reduction in China. Second, the traditional Fenton advanced oxidation technology is a homogeneous catalytic system, so ferrous salts (such as FeSO4) need to be continuously added for catalytic reaction, and a large amount of iron mud will be generated after the reaction, which is difficult to recycle and the treatment is cumbersome. There is little research on how to find a catalytic material that still has high catalytic effect under neutral conditions and can be reused.

[0003] At present, the field of Fenton catalytic materials mainly focuses on the modification research based on traditional Fenton, such as photo-Fenton technology, electro-Fenton technology or related technologies that change inorganic iron to organic iron catalysis. Many types of Fenton catalytic materials either contain various heavy metal components, or have weak ability to catalyze H2O2 to generate reactive oxygen species (ROS), so the ability to degrade COD is also weak, or still require an acidic environment, which cannot fully meet the needs of engineering practice. Finding an efficient Fenton catalytic material that is independent of protons and can be recycled has become an urgent task. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method of a heterogeneous Fenton catalytic material with multi-walled carbon nanotubes confining and loading iron oxides. The prepared material can be independent of protons on the basis of the traditional Fenton advanced oxidation system and can have high catalytic effect under neutral conditions. Due to the heterogeneous catalytic performance of the material, it can be reused, greatly reducing the dosage of chemical agents (such as acid, alkali and FeSO4), and at the same time greatly reducing the generation of iron mud.

[0005] The technical solution of the present invention is: a preparation method of a heterogeneous Fenton catalytic material with multi-walled carbon nanotubes confining and loading iron oxides, comprising the following steps:

[0006] A: Selection and defect treatment of carbon nanotubes;

[0007] A1: Select multi-walled carbon nanotubes (MWCNT) with an inner diameter of 5 - 10 nm, an outer diameter of 10 - 40 nm, a tube length of 10 - 50 μm, and a purity greater than 90%;

[0008] A2: Weigh 0.3 g of MWCNT that meets the conditions of step A1, add it to 30 ml of concentrated nitric acid solution with a mass percentage of 65%, pour the above mixture into a high-pressure hydrothermal reactor with a volume of ≥100 ml, and carry out a constant-temperature oscillation reaction at 120 - 140 °C for 12 - 20 h;

[0009] A3: After cooling the carbon nanotube - nitric acid mixture treated in step A2, perform vacuum filtration and wash it at least 3 times to ensure that the pH value of the filtrate is ≥6.5;

[0010] A4: Resuspend the carbon nanotubes obtained in step A3 in 30 ml of deionized water, perform ultrasonic treatment at 100 - 300 W for 12 h, and then freeze-dry to obtain a qualified pre-treated multi-walled carbon nanotube sample with defects;

[0011] B: Preparation of iron precursor;

[0012] B1: Weigh 1.5 - 2.0 g of Fe(NO3)3·9H2O with a purity above 99% and dissolve it in 250 ml of acetone solution;

[0013] B2: Perform ultrasonic treatment on the above mixture at 100 - 300 W for 2 h, and keep the ultrasonic temperature at 25 - 45 °C;

[0014] C: Preparation of Fe x O y @MWCNT mixture;

[0015] C1: Accurately weigh 0.25 g of MWCNT prepared in step A4, disperse it into 25 ml of the iron precursor solution prepared in step B2, and fully oscillate the mixture for 0.5 h;

[0016] C2: Perform ultrasonic treatment on the mixture treated in step C1 at 100 - 300 W for 6 - 8 h at a temperature of 25 - 45 °C;

[0017] C3: Dry the mixture treated in step C2 at 45 °C to constant weight to obtain the Fe x O y @MWCNT mixture;

[0018] D: Annealing treatment of Fe x O y @MWCNT mixture;

[0019] D1: Heat the Fe x O y @MWCNT mixture to the range of 135 - 150 °C and then perform annealing treatment for 9 - 12 h;

[0020] D2: After the annealing treatment is completed, wash the mixture with deionized water multiple times to remove the residual impurities and unreacted precursors on the surface, and then dry it at 45 °C to ensure the dryness and stability of the material, thereby obtaining a pure multi-walled carbon nanotube-confined iron oxide heterogeneous Fenton catalytic material, namely Fe x O y @MWCNT;

[0021] E: Verification of the Fe x O y @MWCNT catalytic material;

[0022] Grind the Fe x O y @MWCNT material obtained in step D2 thoroughly with an agate mortar and perform characterizations such as TEM and XPS on it, and analyze the types and morphologies of its iron oxides, and the states of Fe x O y embedded inside the carbon nanotubes and anchored on the surface of the carbon nanotubes, so as to verify the differences between the manufactured material and the expected material.

[0023] The present invention is directed to the field of preparation and research and development of new Fenton catalytic materials. The obtained materials can catalyze H2O2 to produce reactive oxygen species (ROS) under neutral conditions and deeply oxidize and degrade organic matter. The catalytic materials can be reused after filtration and precipitation, thus avoiding the generation of a large amount of iron sludge after traditional Fenton oxidation. The catalytic materials prepared by this method have low production costs, are convenient to use, can be reused and have no secondary pollution, and at the same time have remarkable organic matter catalytic degradation ability. Brief Description of the Drawings

[0024] Figure 1 is the flow chart of the present invention;

[0025] Figure 2 is the TEM morphology of the Fe x O y @MWCNT catalytic material;

[0026] Figure 3 is the distribution of iron oxides in the multi-walled carbon nanotubes of Fe x O y @MWCNT;

[0027] Figure 4 is the Fe x O yXPS Characterization Results of @MWCNT Catalytic Materials;

[0028] Figure 5 is Fe x O y Concentration Change of Methylene Blue (MB) in the @MWCNT Material Catalyzing the H2O2 System;

[0029] Figure 6 is Fe x O y COD Removal Rate Change in the @MWCNT Material Catalyzing the H2O2 System;

[0030] Figure 7 is Fe x O y COD Change of Continuous Flow Inlet and Outlet Water in the @MWCNT System. Detailed Implementation Manner

[0031] Example 1: A Preparation Method of a Heterogeneous Fenton Catalytic Material with Multi-Walled Carbon Nanotubes Confined and Loaded with Iron Oxide, including the following steps:

[0032] A: Selection and Defect Treatment of Carbon Nanotubes;

[0033] A1: Select multi-walled carbon nanotubes MWCNT with an inner diameter of 5 - 10 nm, an outer diameter of 10 - 40 nm, a tube length of 10 - 50 μm, and a purity greater than 90%;

[0034] A2: Weigh 0.3 g of MWCNT that meets the conditions of step A1, add it to 30 ml of a concentrated nitric acid solution with a mass percentage of 65%, pour the above mixture into a high-pressure resistant hydrothermal reaction kettle of ≥100 ml, and carry out a constant temperature oscillation reaction at 120 - 140 °C for 12 - 20 h;

[0035] A3: After cooling the carbon nanotube - nitric acid mixture treated in step A2, perform vacuum filtration and wash at least 3 times to ensure that the pH value of the filtrate is ≥6.5;

[0036] A4: Resuspend the carbon nanotubes obtained in step A3 in 30 ml of deionized water, perform ultrasonic treatment at 100 - 300 W for 12 h, and then freeze-dry to obtain a qualified pre-treated multi-walled carbon nanotube sample with defects;

[0037] B: Preparation of Iron Precursors;

[0038] B1: Weigh 1.5 - 2.0 g of Fe(NO3)3·9H2O with a purity above 99% and dissolve it in 250 ml of acetone solution;

[0039] B2: Ultrasonically treat the above mixture at 100 - 300 W for 2 h, and keep the ultrasonic temperature at 25 - 45 °C;

[0040] C:Fe x O y @Preparation of MWCNT hybrids;

[0041] C1: Accurately weigh 0.25 g of MWCNT prepared in step A4, disperse it into 25 ml of the iron precursor solution prepared in step B2, and fully shake the mixture for 0.5 h;

[0042] C2: The mixed solution after step C1 is subjected to ultrasonic treatment at 100-300W for 6-8h at 25-45°C;

[0043] C3: Dry the mixed solution after step C2 at 45°C to constant weight to obtain Fe x O y @MWCNT hybrid;

[0044] D:Fe x O y @MWCNT hybrid annealing treatment;

[0045] D1: Fe prepared in step C3 x O y @MWCNT mixture, after heating to 135-150℃, annealing treatment is performed for 9-12h;

[0046] D2: After the annealing treatment, the mixture was washed several times with deionized water to remove the impurities and unreacted precursors remaining on the surface, and then dried at 45°C to ensure the dryness and stability of the material, thereby obtaining a pure multi-walled carbon tube-confined iron oxide-loaded heterogeneous Fenton catalytic material, namely Fe x O y @MWCNT;

[0047] E:Fe x O y @Verification of MWCNT catalytic materials;

[0048] The Fe obtained in step D2 x O y @MWCNT material, fully ground using an agate mortar and subjected to TEM and XPS characterization to analyze the type and morphology of iron oxides, Fe x O y The state of being embedded inside the carbon tube and anchored on the surface of the carbon tube is used to verify the difference between the finished material and the expected material. Figure 2 , Figure 3 and Figure 4 shown.

[0049] According to the TEM analysis results, Fex O y There are a lot of deposited iron oxides in the inner cavity of the multi-walled carbon tubes of @MWCNT catalytic materials, which are effective catalytic sites. According to XPS data analysis, Fe x O y XPS spectrum of @MWCNT materials and Fe in hematite α-Fe2O3 2+ The main peak binding energies of 711.68 eV and 725 eV match best. 2+ The satellite peak binding energy of 718eV is also reflected in the XPS energy spectrum of the material, so the iron oxide is mainly α-Fe2O3.

[0050] The prepared Fe x O y @MWCNT material, use an agate mortar to fully grind and weigh 0.12g and pour it into 200ml methylene blue (MB) solution with a concentration of 400μmol / L. After using 100W ultrasonic vibration for 5 minutes, magnetic stirring is carried out in a constant temperature water bath at 25℃. The pH value of the system is about 7.4. Then H2O2 is added to make its initial concentration 150mg / L. At this time, the catalytic system begins to react (the group without catalytic material is used as the control group), and samples are taken regularly to test the MB concentration and the corresponding COD value and calculate the COD degradation rate (the contribution of residual H2O2 needs to be deducted from the COD test). The results are as follows Figure 5 and Figure 6 According to the results, the MB concentration in the H2O2 group decreased by less than 5%, while the H2O2+Fe x O y The MB concentration in the MWCNT group decreased by nearly 100%, indicating that the color structure of MB was completely destroyed; the COD decrease in the H2O2 group was smaller, while the H2O2+Fe x O y The COD reduction of the MWCNT group was about 30%, which is equivalent to 140 mg / L COD equivalent of organic matter being completely oxidized and degraded, indicating that Fe x O y @MWCNT's catalysis of H2O2 no longer relies on strong acidic conditions (pH < 3.5) and the heterogeneous Fenton catalytic degradation of COD is effective. The catalytic filler can repeatedly realize the heterogeneous Fenton catalytic utilization, thus greatly reducing the iron sludge produced by traditional Fenton. It is a good advanced oxidation catalytic medium for new energy saving and consumption reduction.

[0051] The prepared Fe x O y@MWCNT material, it was thoroughly ground using an agate mortar and pestle, and 0.96 g was weighed and poured into a conical flask containing 100 ml of pure water. After ultrasonic oscillation at 100 W for 5 minutes, it was loaded into a 2000 ml continuous flow reactor, which was equipped with a micro H2O2 dosing pump and a peristaltic pump for artificial simulated wastewater inlet. The dosing and water inflow were adjusted so that the H2O2 concentration in the influent was about 150 mg / L after the system was operating normally for water inlet and outlet. The influent COD was configured using glucose and was about 100 mg / L. The hydraulic retention time of the system was set to 2 h. A 1000-mesh filter screen was used at the outlet for solid-liquid separation to avoid the loss of Fe x O y @MWCNT. The reactor was placed in a 25 °C constant temperature water bath and magnetically stirred. The pH value of the system was about 7.4. Samples were taken regularly to test the COD values of the influent and effluent. The results are as Figure 7 . According to the result analysis, under the continuous flow operation reaction conditions for 3 days, a total of 72 h, the influent COD was maintained between 95 - 105 mg / L. After oxidation by the Fe x O y @MWCNT material heterogeneous Fenton system, the effluent COD decreased to about 35 mg / L, fully meeting the current domestic sewage discharge standards. The COD reduction rate was about 60 - 70%. With the operation of the system, the oxidation and decomposition effect of organic matter did not decrease significantly, indicating that Fe x O y @MWCNT has good reusability.

Claims

1. A method for preparing a heterogeneous Fenton catalytic material containing iron oxides and confined multi-walled carbon tubes, characterized in that: The following steps are involved: A: Selection of carbon tubes and defect treatment; A1: Select multi-walled carbon nanotubes (MWCNT) with an inner diameter of 5-10 nm, an outer diameter of 10-40 nm, a tube length of 10-50 μm, and a purity greater than 90%; A2: Weigh 0.3 g of MWCNT that meets the conditions of step A1, add it to 30 ml of 65% concentrated nitric acid solution, pour the mixture into a ≥100 ml high pressure hydrothermal reactor, and react at a constant temperature of 120-140°C for 12-20 hours; A3: After cooling the carbon tube-nitric acid mixture treated in step A2, vacuum filter and wash at least 3 times to ensure that the pH value of the filtrate is ≥ 6.5; A4: The carbon nanotubes obtained in step A3 are resuspended in 30 ml of deionized water, and after ultrasonic treatment at 100-300 W for 12 h, freeze-dried to obtain a pre-treated qualified multi-walled carbon nanotube sample with defects; B: Preparation of iron precursor; B1: Weigh 1.5-2.0g of Fe(NO3)3·9H2O with a purity of more than 99% and dissolve it in 250ml of acetone solution; B2: The mixed solution was treated with ultrasound at 100-300W for 2h, and the ultrasound temperature was maintained at 25-45°C; C:Fe x O y @Preparation of MWCNT hybrids; C1: Accurately weigh 0.25 g of MWCNT prepared in step A4, disperse it into 25 ml of the iron precursor solution prepared in step B2, and fully shake the mixture for 0.5 h; C2: The mixed solution after step C1 is subjected to ultrasonic treatment at 100-300W for 6-8h at 25-45°C; C3: Dry the mixed solution after step C2 at 45°C to constant weight to obtain Fe x O y @MWCNT hybrid; D:Fe x O y @MWCNT hybrid annealing treatment; D1: Fe prepared in step C3 x O y @MWCNT mixture, after heating to 135-150℃, annealing treatment is performed for 9-12h; D2: After the annealing treatment, the mixture was washed several times with deionized water to remove the impurities and unreacted precursors remaining on the surface, and then dried at 45°C to ensure the dryness and stability of the material, thereby obtaining a pure multi-walled carbon tube-confined iron oxide-loaded heterogeneous Fenton catalytic material, namely Fe x O y @MWCNT; E:Fe x O y @Verification of MWCNT catalytic materials; The Fe obtained in step D2 x O y @MWCNT material, fully ground using an agate mortar and subjected to TEM and XPS characterization to analyze the type and morphology of iron oxides, Fe x O y The state of being embedded inside the carbon tube and anchored on the surface of the carbon tube is used to verify the difference between the finished material and the expected material.

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