Carbon nanotube coated Fe3C catalyst, preparation method thereof and application of Fenton-like treatment of phenol wastewater

Abstract

The invention discloses a preparation method of a carbon nano tube coated Fe3C catalyst and application of the carbon nano tube coated Fe3C catalyst in a Fenton-like phenol advanced oxidation technology, and aims to solve the problems that a traditional Fenton wastewater treatment catalyst is difficult to separate and reuse, low in reaction activity and low in reaction pH, a large amount of iron-containing sludge can be generated, secondary pollution is caused by a large amount of Fe < 2 + > contained in effluent, and the like. The phenol degradation rate of the iron-carbon catalyst prepared by the preparation method disclosed by the invention can reach 80-90% when the iron-carbon catalyst reacts for 1 hour at room temperature; the method comprises the following steps: 1, weighing an iron source solid and a carbon source solid, dissolving the iron source solid and the carbon source solid in absolute ethyl alcohol, continuously stirring by using a magnetic stirrer to form a purple black solution, heating to evaporate a solvent, and transferring into a drying oven to dry overnight after the solvent is dried to form gel; 2, grinding, and calcining at high temperature to obtain an iron carbide solid catalyst; belongs to the technical field of environmental pollutant treatment.

Description

Technical Field

[0001] The present invention relates to the technical fields of refractory wastewater treatment and environmental engineering, and more specifically, to a carbon nanotube-coated Fe 3 C catalyst, its preparation method, and its application in treating phenol wastewater by a Fenton-like process. Background Art

[0002] Phenol is a compound with extremely high environmental toxicity, which can inhibit the growth of microorganisms and cause ecological imbalance. Phenol-containing wastewater is considered a common type of wastewater due to its wide sources and great harm. Therefore, it is necessary to develop effective methods to improve the removal rate of phenol in wastewater.

[0003] Conventional treatment processes can be classified into physical treatment technologies, chemical treatment technologies, and biochemical treatment technologies according to different treatment mechanisms. Conventional physical treatment technologies include four categories: adsorption, membrane separation technology, thermal evaporation technology, and combined processes formed by two technologies. Biochemical technologies include common activated sludge technology, anaerobic method, aerobic method, A / O technology, A2 / O technology, biological aerated filter, etc.

[0004] The Fenton reaction is a type of advanced oxidation technology. By reacting Fe 2+ with H 2 O 2 to generate strongly oxidizing hydroxyl radicals, it can effectively remove substances that are difficult to degrade in water. Traditional homogeneous Fenton systems have some disadvantages, such as a narrow pH range, the generation of a large amount of iron-containing sludge by-products, and a complex post-treatment process. Heterogeneous Fenton-like oxidation is achieved by using a solid-phase catalyst that is easy to recycle to replace Fe 2+ , and then by activating other oxidants that can replace H 2 O 2 to improve its degradation efficiency. It has the advantages of low cost, low toxicity, good environmental compatibility, and easy separation. Compared with homogeneous reactions, heterogeneous catalysts can be separated from the reaction system and reused after use. This not only overcomes the problem of iron-containing sludge generation in homogeneous systems but also reduces the treatment cost, and is considered a promising method for sewage treatment.

[0005] To solve the above problems and use a more efficient and recyclable catalyst, Chinese invention patent CN113559901A discloses a preparation method of a silicon and rare earth modified Fe 3 C catalyst. Although this catalyst has a porous structure and good catalyst stability, it uses rare earth nitrates such as cerium nitrate or lanthanum nitrate, resulting in high costs and poor economy.

[0006] Therefore, it is particularly necessary to develop a catalyst with high catalytic activity, a simple preparation process, low raw material costs, and easy availability. Summary of the Invention

[0007] In view of the above deficiencies, the first object of the present invention is to provide a carbon nanotube-wrapped Fe 3 C catalyst, which has high activity, good stability, and can be reused.

[0008] The second object of the present invention is to provide a preparation method of the carbon nanotube-wrapped Fe 3 C catalyst, the preparation method of which is simple, the raw materials are easy to obtain, and the production cost is low.

[0009] The third object of the present invention is to provide a method for catalytic oxidation of phenol by the carbon nanotube-wrapped Fe 3 C catalyst.

[0010] To this end, the technical solution provided by the present invention is as follows:

[0011] A preparation method of a carbon nanotube-wrapped Fe 3 C catalyst, comprising the following steps:

[0012] S1. Dissolve the iron source in absolute ethanol and stir to obtain solution A;

[0013] S2. Dissolve the carbon source in absolute ethanol and stir to obtain solution B;

[0014] S3. Mix and stir solution A prepared in S1 and solution B prepared in S2, then heat and react, cool to room temperature, and then perform air drying;

[0015] S4. Grind the dried substance finely and then perform high-temperature calcination to obtain the carbon nanotube-wrapped Fe 3 C catalyst;

[0016] The molar ratio of the iron source compound to the carbon source compound is 0.5:1 to 3:1.

[0017] Further, in the preparation method of the above-mentioned carbon nanotube-wrapped Fe 3 C catalyst, in step S1, the iron source is Fe(NO 3 ) 3 ; the stirring time is 5 min.

[0018] Further, in the preparation method of the above-mentioned carbon nanotube-wrapped Fe 3 C catalyst, in step S2, the carbon source is one of o-phenylenediamine and 1,10-phenanthroline; the stirring time is 5 min.

[0019] Further, in the preparation method of the above-mentioned carbon nanotube-wrapped Fe 3C catalyst and its preparation method. In step S3, the stirring time is 60 min to 120 min; the reaction temperature is 85 °C; the air-blowing drying temperature is 105 - 150 °C, and the time is 10 - 12 h.

[0020] Further, the above-mentioned carbon nanotube-wrapped Fe 3 C catalyst and its preparation method. In step S4, the high-temperature calcination temperature is 800 - 900 °C, the calcination time is 3 - 5 h, and the heating rate is 5 °C / min.

[0021] The second technical solution provided by the present invention is a carbon nanotube-wrapped Fe 3 C catalyst prepared by the method described in the first technical solution.

[0022] The third technical solution provided by the present invention is a carbon nanotube-wrapped Fe 3 Method for catalytic oxidation of phenol by C catalyst. Using phenol as the target pollutant, in an aqueous solution, in the presence of an oxidant, using the carbon nanotube-wrapped Fe 3 C catalyst described in the second technical solution as the catalyst, reacting at room temperature (25 °C) for 0.5 - 1 h to oxidize phenol pollutants in the wastewater;

[0023] The mass ratio of the oxidant, carbon nanotube-wrapped Fe 3 C catalyst, and phenol is: 1.78 - 177.7: 20 - 30: 0.47.

[0024] The concentration ratio of the phenol to the solvent (H 2 O) is 0.1 mmol / L.

[0025] The pH of the reaction system is 3 - 11.

[0026] Further, for the method for catalytic oxidation of phenol by the above-mentioned carbon nanotube-wrapped Fe 3 C catalyst, the oxidant is one of sodium persulfate, potassium peroxymonosulfate, sodium periodate, and hydrogen peroxide.

[0027] The fourth technical solution provided by the present invention is a method for EPR testing of catalytic oxidation of phenol by a carbon nanotube-wrapped Fe 3 C catalyst. Using phenol as the target substance, in an aqueous solution, in the presence of the catalyst and oxidant prepared by the method described in the first technical solution, after being captured by a scavenger, the free radical spectra are measured before and after the addition of phenol.

[0028] The concentration of the catalyst is 0.5 mg / mL.

[0029] The concentration of the oxidant is 1 - 100 mmol / L.

[0030] The concentration ratio of the described phenol to the solvent (H 2 O) is 0.1 mmol / L.

[0031] The described scavenger is 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), and the volume ratio to the total volume of the solution is 1:50.

[0032] The described oxidant is one of sodium persulfate, potassium peroxymonosulfate, sodium periodate, and hydrogen peroxide.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention synthesizes Fe 3 ) 3 C catalyst using Fe(NO 3 , o-phenylenediamine, and 1,10-phenanthroline as raw materials. Due to the adsorbability of the support material, phenol can be first adsorbed onto the surface of the catalyst, and then a strongly oxidizing complex is generated through the reaction of the catalyst with the oxidant. The hydrogen on the hydroxyl group of the phenol molecule is removed and connected to another dehydrogenated phenol molecule, and the phenol molecules are continuously polymerized. Washing the catalyst with ethanol can remove phenol in the wastewater. The catalyst has ferromagnetism, and the purpose of recycling the catalyst can be achieved using a magnet, and this reaction is carried out under normal temperature conditions. Through this method, the oxidative degradation of phenol pollutants is realized, and the reaction process has good safety, simple operation, and the catalyst can be recycled and reused, having good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the XRD pattern of Example 1;

[0036] Figure 2 is the XRD pattern of Example 2;

[0037] Figure 3 is the oxidative degradation efficiency graph of Example 3;

[0038] Figure 4 is the oxidative degradation efficiency graph at different pH values of Example 4.

[0039] Figure 5 is the EPR pattern of Example 5;

[0040] Figure 6 is the EPR pattern of Example 6; DETAILED DESCRIPTION OF THE INVENTION

[0041] The following further illustrates the present invention in conjunction with examples, but the present invention is not limited by these examples.

[0042] Example 1

[0043] A carbon nanotube-wrapped Fe 3 C catalyst provided by this embodiment is prepared by the following method:

[0044] S1. Dissolve 3.0 g of Fe(NO 3 ) 3 in 25 mL of absolute ethanol, and stir at room temperature for 5 min to obtain solution A;

[0045] S2. Dissolve 7.2 g of o-phenylenediamine in 25 mL of absolute ethanol, and stir at room temperature for 5 min to obtain solution B;

[0046] S3. Mix and stir the solution A prepared in S1 and the solution B prepared in S2, then react at 85 °C for 1 h, 1.5 h, and 2 h respectively, cool to room temperature, and then dry in a blast dryer at 105 °C for 10 h;

[0047] S4. Grind the product obtained in S3 finely, then transfer it into a tubular furnace, and under a N 2 atmosphere, heat it to 900 °C at a heating rate of 5 °C / min, and calcine it at 900 °C for 4 h to obtain the carbon nanotube-wrapped Fe 3 C catalyst.

[0048] The XRD pattern of this catalyst is referred to Figure 1 , and it can be seen through Figure 1 that: a relatively strong diffraction peak appears at a diffraction peak position of 26.5°, corresponding to the (020) plane of graphite carbon; relatively strong diffraction peaks appear at diffraction peak positions of 37.66°, 37.74°, 42.88°, 43.74°, 44.57°, 44.99°, 45.86°, and 49.11°, corresponding to the (121) plane, (210) plane, (211) plane, (102) plane, (220) plane, (031) plane, (112) plane, and (221) plane of Fe 3 C respectively, and the Fe 3 C catalyst is successfully synthesized.

[0049] Example 2

[0050] A carbon nanotube-wrapped Fe 3 C catalyst provided by this embodiment is prepared by the following method:

[0051] S1. Dissolve 3.0 g of Fe(NO 3 ) 3 in 25 mL of absolute ethanol, and stir at room temperature for 5 min to obtain solution A;

[0052] S2. Dissolve 12.0 g of 1,10-phenanthroline in 25 mL of absolute ethanol, and stir at room temperature for 5 min to obtain solution B;

[0053] S3. Mix and stir solution A prepared in S1 and solution B prepared in S2, then react them at 85 °C for 1 h, 1.5 h, and 2 h respectively, cool to room temperature, and then dry them in a blast dryer at 105 °C for 12 h;

[0054] S4. Grind the product obtained in S3 finely, and then transfer it into a tubular furnace. Under an N 2 atmosphere, heat it to 800 °C at a heating rate of 5 °C / min, and calcine it at 800 °C for 4 h to obtain the carbon nanotube-wrapped Fe 3 C catalyst.

[0055] The XRD pattern of this catalyst is referred to Figure 2 , and it can be seen through Figure 2 : There is a strong diffraction peak at the diffraction peak position of 26.5°, corresponding to the (020) plane of graphite carbon. Strong diffraction peaks appear at the diffraction peak positions of 37.63°, 37.74°, 42.88°, 43.74°, 44.57°, 44.99°, 45.86°, and 49.11°, corresponding to the (121) plane, (210) plane, (211) plane, (102) plane, (220) plane, (031) plane, (112) plane, and (221) plane of Fe 3 C respectively, and the Fe 3 C catalyst is successfully synthesized.

[0056] Example 3

[0057] A method for the efficient oxidation of phenol by a carbon nanotube-wrapped Fe 3 C catalyst, comprising the following steps:

[0058] S1. Dissolve 2.35 mg of phenol in 250 mL of deionized water and stir for 10 min to obtain liquid A;

[0059] S2. Place 25 mg of the carbon nanotube-wrapped Fe 3 C catalyst of Example 1 in 50 mL of solution A, then stir for 10 min to obtain mixture B;

[0060] S3. Dissolve 1.78 mg, 8.9 mg, 17.8 mg, 88.9 mg, and 177.7 mg of potassium peroxymonosulfate in 0.5 mL of deionized water respectively to obtain 0.1 mM, 0.5 mM, 1 mM, 5 mM, and 10 mM solutions C;

[0061] S4. Place mixture B in a digital display constant temperature magnetic stirrer with a rotation speed of 120 r / min and a temperature of 25 °C. Add solution C and start timing. Take 0.5 mL of samples with a syringe at 0, 1, 2, 3, 5, 10, 20, 40, and 60 min, filter them through a 4.5 μm needle filter, and measure the phenol concentration value by HPLC.

[0062] Refer to the oxidation degradation efficiency diagram Figure 3 . After 10 minutes of reaction, the conversion rates of 0.1 mM, 0.5 mM, 1 mM, 5 mM, and 10 mM potassium persulfate solutions are 45.14%, 32.91%, 54.95%, 71.13%, and 66.56% respectively; after 60 minutes of reaction, the conversion rates are 81.63%, 84.97%, 82.66%, 88.21%, and 88.40% respectively. The reaction rate is relatively fast in the first 20 minutes and then gradually slows down. Generally speaking, 0.5 mM potassium persulfate should be selected for more economic practical applications.

[0063] Example 4

[0064] A method for oxidizing phenol by a carbon nanotube-wrapped Fe 3 C catalyst, comprising the following steps:

[0065] S1. Dissolve 2.35 mg of phenol in 250 mL of deionized water, stir for 10 minutes, and then take 50 mL each to prepare solutions with pH = 3, 5, 7, 9, and 11 to obtain solution A;

[0066] S2. Place 25 mg of the carbon nanotube-wrapped Fe 3 C catalyst from Example 1 into 50 mL of solution A, and then stir for 10 minutes to obtain mixture B;

[0067] S3. Dissolve 8.9 mg of potassium persulfate in 0.5 mL of deionized water to obtain a 0.5 mM solution C;

[0068] S4. Place mixture B in a digital display constant temperature magnetic stirrer with a rotation speed of 120 r / min and a temperature of 25 °C. Add solution C and start timing. Take 0.5 mL of sample with a syringe at 0, 1, 2, 3, 5, 10, 20, 40, and 60 minutes. After filtering through a 4.5 μm needle filter, measure the phenol concentration value by HPLC.

[0069] Refer to the oxidation degradation efficiency diagram Figure 4 . After 10 minutes of reaction, the conversion rates at pH = 3, 5, 7, 9, and 11 are 41.91%, 44.52%, 55.51%, 54.81%, and 39.30% respectively; after 60 minutes of reaction, the conversion rates are 90.48%, 87.10%, 85.40%, 82.66%, and 85.22% respectively. The reaction rate is relatively fast in the first 30 minutes and then gradually slows down.

[0070] Example 5

[0071] A method for testing the electron paramagnetic resonance (EPR) of a carbon nanotube-wrapped Fe 3 C catalyst for phenol oxidation, comprising the following steps:

[0072] S1. Dissolve 5 mg of the Fe 3 C catalyst prepared in Example 1 in 1 mL of deionized water and ultrasonicate for 10 min to obtain suspension A;

[0073] S2. Dissolve 0.5953 g of sodium persulfate in 25 mL of deionized water to obtain solution B;

[0074] S3. Dissolve 0.8888 g of potassium peroxymonosulfate in 25 mL of deionized water to obtain solution C;

[0075] S4. Dissolve 0.5348 g of sodium periodate in 25 mL of deionized water to obtain solution D;

[0076] S5. Dissolve 8.3333 mL of hydrogen peroxide in 25 mL of deionized water to obtain solution E;

[0077] S6. Take four 2-mL centrifuge tubes, labeled as centrifuge tube 1, centrifuge tube 2, centrifuge tube 3, and centrifuge tube 4. First, add 10 μL of the scavenger (DMPO) to each of the 4 centrifuge tubes. Then, add 450 μL of solution B to centrifuge tube 1; add 450 μL of solution C to centrifuge tube 2; add 450 μL of solution D to centrifuge tube 3; add 450 μL of solution E to centrifuge tube 4; shake well, set the microwave power of the instrument to 0.5 mW, the scanning width to 120 G, and scan 3 times.

[0078] The results are shown in Figure 5 , and it can be seen from Figure 5 that when the catalyst reacts with sodium persulfate, potassium peroxymonosulfate, and sodium periodate respectively, strongly oxidizing catalyst-oxidant complexes are generated in the system. Moreover, when reacting with potassium peroxymonosulfate, the signal intensity of strong oxidation is the strongest, followed by sodium periodate, and the weakest is sodium persulfate. Then the difficulty of activating the oxidant by this catalyst is: potassium peroxymonosulfate > sodium periodate > sodium persulfate. When the catalyst reacts with hydrogen peroxide, no oxidizing substances are generated in the system, and hydrogen peroxide is not activated.

[0079] Example 6

[0080] A method for testing the electron paramagnetic resonance of phenol oxidation catalyzed by a carbon nanotube-wrapped Fe 3 C catalyst, comprising the following steps:

[0081] S1. Dissolve 5 mg of the Fe 3 C catalyst prepared in Example 1 in 1 mL of deionized water and ultrasonicate for 10 min to obtain suspension A;

[0082] S2. Dissolve 0.5953 g of sodium persulfate in 25 mL of deionized water to obtain solution B;

[0083] S3. Dissolve 0.8888 g of potassium monopersulfate in 25 mL of deionized water to obtain Solution C;

[0084] S4. Dissolve 0.5348 g of sodium periodate in 25 mL of deionized water to obtain Solution D;

[0085] S5. Dissolve 8.3333 mL of hydrogen peroxide in 25 mL of deionized water to obtain Solution E;

[0086] S6. Dissolve 2.35 mg of phenol in 250 mL of deionized water to obtain Solution F;

[0087] S7. Take four 2-mL centrifuge tubes, denoted as centrifuge tube 1, centrifuge tube 2, centrifuge tube 3, and centrifuge tube 4. First, add 10 μL of the capture agent to each of the 4 centrifuge tubes. Then, add 400 μL of Solution B to centrifuge tube 1; add 400 μL of Solution C to centrifuge tube 2; add 400 μL of Solution D to centrifuge tube 3; add 400 μL of Solution E to centrifuge tube 4. Then, add 50 μL of Solution F to each of the four centrifuge tubes and shake well. Set the microwave power of the instrument to 0.5 mW, the scanning width to 120 G, and scan 3 times.

[0088] Results are shown in Figure 6 , and it can be seen through Figure 6 : The catalyst reacts with sodium persulfate, potassium monopersulfate, sodium periodate, and hydrogen peroxide respectively. Then, after adding the phenol solution, compared with Example 5, the strong oxidizing signal of the system disappears, indicating that the strong oxidizing substances generated by the system react with phenol. When the catalyst reacts with hydrogen peroxide, no oxidizing substances are generated in the system, hydrogen peroxide is not activated, and no oxidizing signal is generated in the system after adding phenol.

[0089] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a carbon nanotube-wrapped Fe3C catalyst, characterized in that: The steps are as follows: S1. dissolving the iron source compound in a solvent and stirring to obtain a solution A; S2. dissolving the carbon source compound in the solvent and stirring to obtain a solution B; S3. The solution A prepared in S1 and the solution B prepared in S2 were mixed and stirred, and the solvent was evaporated by heating, and the reaction was cooled to room temperature and dried; S4. The dried material is ground into fine powder and then calcined at high temperature to obtain a Fe3C solid catalyst; The molar ratio of the iron source compound to the carbon source compound is 0.5:1 to 3:

1.

2. The method for preparing a carbon nanotube-wrapped Fe3C catalyst according to claim 1, characterized in that: In step S1, the iron source compound is Fe(NO3)3; and the solvent is anhydrous ethanol.

3. The method for preparing a carbon nanotube-wrapped Fe3C catalyst according to claim 1, characterized in that: In step S2, the carbon source compound is one of o-phenylenediamine and 1,10-phenanthroline; and the solvent is anhydrous ethanol.

4. The method for preparing a carbon nanotube-wrapped Fe3C catalyst according to claim 1, characterized in that: In step S3, the mixing and stirring time is 60 min to 120 min.

5. The method for preparing a carbon nanotube-wrapped Fe3C catalyst according to claim 1, characterized in that: In step S3, the heating temperature is 85°C; the drying temperature is 105-150°C, and the drying time is 10-12 hours.

6. The method for preparing a carbon nanotube-wrapped Fe3C catalyst according to claim 1, characterized in that: In step S4, the high temperature calcination temperature is 800°C to 900°C, the calcination time is 3-5h, and the heating rate is 5°C / min.

7. A carbon nanotube-wrapped Fe3C catalyst, characterized in that: Prepared by the method described in any one of claims 1 to 6.

8. A method for catalyzing the oxidation of organic pollutants in wastewater using a carbon nanotube-wrapped Fe3C catalyst, characterized in that: Adding an oxidant and the carbon nanotube-wrapped Fe3C catalyst according to claim 6 into a phenol aqueous solution, and reacting at 25° C. for 30-60 minutes; The mass ratio of the oxidant, the carbon nanotube-wrapped Fe3C catalyst and the phenol is: 1.78-177.7: 20-30: 0.

47.

9. The method for catalyzing the oxidation of organic pollutants in wastewater by using a carbon nanotube-wrapped Fe3C catalyst according to claim 7, characterized in that: The oxidant is one of sodium persulfate, potassium hydrogen persulfate, sodium periodate, and hydrogen peroxide, or any combination thereof.

10. A method for testing the oxidation of organic pollutants in wastewater by an electron paramagnetic resonance spectrometer using a carbon nanotube-wrapped Fe3C catalyst, characterized in that: Taking phenol as the target, in an aqueous solution, in the presence of the catalyst prepared by claim 1 and an oxidant, the free radical spectrum before and after the addition of phenol is measured after being captured by a capture agent; The capture agent is 5,5-dimethyl-1-pyrroline-N-oxide; the oxidant is one of sodium persulfate, potassium persulfate, sodium periodate, hydrogen peroxide or any combination thereof. In the reaction system: The catalyst concentration is 0.5 mg / mL, and the oxidant concentration is 1-100 mmol / L.

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