Efficient iron-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses an efficient iron-based catalyst as well as a preparation method and application thereof. The efficient iron-based catalyst is obtained by taking iron mud as an iron source, taking biochar as a carbon carrier, taking a mixture of the iron mud and the biochar as a precursor and taking alternating current or direct current as a triggering mode. The iron-based catalyst can be applied to treatment of organic polluted wastewater by cooperating with an oxidizing agent, and has efficient degradation capacity at different pH values. According to the method, waste is treated with waste, and waste of iron resources is avoided; through application of a new technology, a traditional recycling method is simplified, and sustainable disposal of harmlessness, reduction and recycling of the iron sludge is achieved. Therefore, the method has great market popularization prospects and has important significance on environmental protection.

Description

Technical Field

[0001] The invention belongs to the field of organic waste resource recovery technology and environmental pollution control, and particularly relates to a high-efficiency iron-based catalyst and a preparation method and application thereof. Background Art

[0002] Fenton and Fenton-like technologies are considered to be effective organic wastewater treatment technologies because of their powerful oxidation ability and their ability to target and degrade various organic matter in water without discrimination. However, during the treatment process of Fenton and Fenton-like technologies, the excited divalent iron ions are easily oxidized into trivalent iron while decomposing organic pollutant molecules, and a large amount of solid waste, namely iron sludge, is produced. Iron sludge is rich in metal ions such as iron, organic matter, bacteria and other substances, and improper treatment may cause secondary environmental pollution.

[0003] The main component of iron sludge is iron hydroxide, which generally accounts for 55% to 60% of the total amount. The existing recycling and treatment technologies are mostly through boiler incineration, chemical refining and landfill, which have the disadvantages of high cost, complex process and easy secondary pollution. How to achieve the sustainable disposal of iron sludge in a harmless, reduced and resource-based manner is an important problem in the application and promotion of Fenton technology in environmental pollution control. Summary of the invention

[0004] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a method for preparing an efficient iron-based catalyst. The method uses iron mud as raw material and Joule heat technology to quickly synthesize an efficient iron-based catalyst that can effectively degrade organic pollutants, thereby realizing the green resource utilization of iron mud and expanding the practical application of Fenton and Fenton-like technologies.

[0005] Another object of the present invention is to provide a high-efficiency iron-based catalyst obtained by the above preparation method.

[0006] Another object of the present invention is to provide an application of the above-mentioned high-efficiency iron-based catalyst.

[0007] The purpose of the present invention is achieved by the following technical solution: a method for preparing a high-efficiency iron-based catalyst, comprising the following steps: using iron mud as an iron source, biochar as a carbon carrier, a mixture of iron mud and biochar as a precursor, and using alternating current or direct current as a triggering method to obtain a high-efficiency iron-based catalyst; specifically comprising the following steps:

[0008] (1) drying the iron mud to constant weight, crushing and sieving to obtain powder;

[0009] (2) uniformly mixing the powder obtained in step (1) and biochar to obtain a material precursor;

[0010] (3) Using Joule heat technology to treat the material precursor obtained in step (2) to obtain a high-efficiency iron-based catalyst.

[0011] The iron sludge is the sludge produced after treating wastewater by Fenton or Fenton-like reaction, including but not limited to the sludge obtained by the following steps: neutralization treatment with alkali, or treatment with alkali and flocculant.

[0012] When the sludge contains a lot of water, it is preferably first treated by filtering or suction to remove the water.

[0013] The comminution method is preferably grinding.

[0014] The sieving is preferably through an 80-mesh sieve.

[0015] The biochar is preferably prepared by hydrothermal method or pyrolysis method from at least one of forest dead branches, crop straw, edible fungus matrix, grain shells, fruit shells, urban garbage and sludge.

[0016] The powder and the biochar are preferably mixed in a mass ratio of 0.5 to 10:1; more preferably in a mass ratio of 1:1.

[0017] The mixing method in step (2) is preferably grinding.

[0018] The treatment environment described in step (3) is preferably an oxygen-free environment.

[0019] The oxygen-free environment is a vacuum-like environment or an environment filled with inert gas.

[0020] The inert gas includes but is not limited to nitrogen, argon and helium.

[0021] The parameters of the Joule heating technique described in step (3) are preferably:

[0022] A. The conditions of alternating current are set as follows: voltage of 100-220V, reaction time of 1-10s, and reaction number of 1 time; preferably: voltage of 150V, reaction time of 10s, and reaction number of 1 time;

[0023] B. The direct current conditions are set as follows: voltage of 100-220 V, number of reactions of 1-10 times, and each reaction time of 10-1000 ms; preferably: voltage of 150 V, number of reactions of 1 time, and reaction time of 50 ms.

[0024] In order to ensure the uniformity of the final material, when using alternating current to act on the material precursor, it is preferred to also include the following steps: adjusting the external resistance to 0 to 30Ω, controlling the total resistance of the samples treated identically to be within the same range, with an error of ±10Ω; the samples treated identically are material precursors obtained by treating under the same conditions as step (2).

[0025] The Joule heating technology is achieved by using a Joule heating device, which can be performed by selecting a Joule heating device that meets the operating parameters.

[0026] The Joule heating device includes a power control system, a reaction box and an oscilloscope monitoring system; wherein the power control system and the oscilloscope monitoring system are respectively connected to the reaction box; the power control system can set the current trigger type and adjust the reaction parameters; the reaction box is used to place samples, connected to the sample tube through electrodes at both ends, and the sample is squeezed before the reaction to reduce the internal resistance of the sample; the oscilloscope monitoring system can monitor the voltage and current changes during the reaction process.

[0027] A high-efficiency iron-based catalyst is obtained through the preparation method.

[0028] The use of the above-mentioned high-efficiency iron-based catalyst in degrading organic pollutants preferably comprises the following steps: adding the high-efficiency iron-based catalyst and an oxidant to the organic pollutants for reaction.

[0029] The organic pollutants include insecticides, antibiotics, dyes, detergents, pesticides, etc.; preferably, chloramphenicol.

[0030] The organic pollutants are preferably organic pollutants in wastewater.

[0031] The concentration of the organic pollutants is 0-200 mg / L, excluding the endpoint value 0; preferably 80 mg / L.

[0032] The oxidant is preferably at least one of hydrogen peroxide and persulfate.

[0033] The persulfate is preferably at least one of potassium peroxymonosulfate, potassium peroxydisulfate, sodium peroxymonosulfate and sodium peroxydisulfate.

[0034] The dosage of the high-efficiency iron-based catalyst is determined according to the concentration of organic pollutants, preferably 0.01-2 g / L; more preferably 0.5 g / L.

[0035] The dosage of the oxidant is determined according to the concentration of the organic pollutants, preferably 1-10 mmol / L, more preferably 5 mmol / L.

[0036] The reaction conditions are preferably as follows: temperature of 20-45°C, reaction time of 5-100 minutes, and pH of 3-12.

[0037] Compared with the prior art, the present invention has the following advantages and effects:

[0038] (1) In order to realize the resource utilization of iron ions in iron mud, the present invention uses biochar as a carbon carrier and adopts Joule heat technology to synthesize an iron-loaded catalyst in one step. This technology uses the ultra-high temperature generated instantly to promote the exfoliation of biochar into graphene carbon layers; the ionization action breaks the barrier of the change of the valence state of iron ions, promotes the uniform distribution of divalent iron (nanoparticles) and iron atoms on the carbon layer, and improves the electron transfer ability of the catalyst during the reaction. It overcomes the shortcomings of traditional preparation methods that are energy-intensive and require cumbersome and complicated steps to achieve material optimization.

[0039] (2) The iron-based catalyst synthesized from iron mud can be applied to the treatment of organic polluted wastewater. For example, in the present invention, when the concentration of chloramphenicol is 80 mg / L, when the iron-based catalyst with a final concentration of 0.5 g / L and 5 mmol / L of sodium persulfate are added, the degradation rate of chloramphenicol can reach 98.7% in 70 minutes. This method realizes the treatment of waste with waste, has significant economic and social benefits in environmental protection, energy conservation and emission reduction, has great prospects for market promotion, and is of great significance to environmental protection.

[0040] In summary, the present invention provides an economical and effective method for recycling iron sludge, which can replace the traditional treatment methods of burning or landfilling, and avoid the waste of iron resources. The recycling effect of industrial iron sludge is remarkable, and the obtained iron-based material is applied to the treatment of organic wastewater, and has a high degradation ability in organic wastewater of different pH values, realizing waste treatment with waste, which is helpful to promote the practical application of Fenton and Fenton-like technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a diagram showing the degradation effect of chloramphenicol on the catalysts prepared from different waste raw materials using Joule heat technology in Example 1.

[0042] Figure 2 This is a diagram showing the degradation effects of iron-based catalysts prepared by different methods in Example 1 on chloramphenicol.

[0043] Figure 3 This is a diagram showing the degradation effect of chloramphenicol on the iron-based catalyst prepared by iron mud under different pH conditions in Example 2. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0045] Example 1

[0046] Based on iron mud, iron-based catalysts were quickly prepared using Joule heat technology, and the differences in the degradation effects of iron-based catalysts prepared by different raw materials and different methods on chloramphenicol were compared, and the effectiveness of iron-based catalysts on the degradation of organic pollutants was verified. The specific operations are as follows:

[0047] (1) Material preparation:

[0048] A. Add alkali and polyacrylamide (flocculant) to the pharmaceutical wastewater after Fenton treatment, filter it to obtain an iron mud mixture, dry it and grind it through an 80-mesh sieve to obtain iron mud powder; use wood chips as raw materials, pyrolyze at 700℃ for 120 minutes in a nitrogen atmosphere to obtain biochar. Grind and mix the treated iron mud powder and biochar at a mass ratio of 1:1 to obtain a material precursor. Then, the material precursor is loaded into a quartz tube, and after placing graphite carbon rods at both ends, the sample tube is placed in a reaction box, and the vacuum pump is used to extract the air to achieve an oxygen-free state. The reaction conditions are set as follows: when the reaction type is alternating current, the voltage is 150V, the reaction time is 10 seconds, and the number of reactions is 1; when the sample mass is 0.1g, the total resistance of the adjustment circuit is 80±10Ω, and the sample obtained after the reaction is named FeAC; when the reaction type is direct current, the voltage is 150V, the reaction time is 50ms, the number of reactions is 1, and the sample obtained is named FeDC.

[0049] B. When using different raw materials as a comparison, the municipal sludge is dehydrated and dried, then ground through an 80-mesh sieve, and the sludge and biochar are ground and mixed at a mass ratio of 1:1 to obtain a material precursor. The material precursor is then loaded into a quartz tube, and after graphite carbon rods are placed at both ends, the sample tube is placed in a reaction box, and the vacuum pump extracts the air to achieve an oxygen-free state. The reaction conditions are set as follows: the reaction type is alternating current, the voltage is 150V, when the sample mass is 0.1g, the external resistance is adjusted from 0 to 30Ω so that the total circuit resistance is 80±10Ω, the reaction time is 10 seconds, the number of reactions is 1, and it is named SAC.

[0050] C. When using different methods for comparison, the iron-based catalyst was prepared by pyrolysis. The dried and ground iron mud was placed in a tube furnace and pyrolyzed at 700°C for 120 minutes under a nitrogen atmosphere. After cooling, it was taken out. The iron-based catalyst obtained by pyrolysis was named FePC.

[0051] (2) Chloramphenicol wastewater degradation simulation: In a glass tube, an iron-based catalyst and sodium persulfate were added to a chloramphenicol solution with a concentration of 80 mg / L, wherein the concentration of the iron-based catalyst in the reaction system was 0.5 g / L, and the concentration of sodium persulfate in the reaction system was 5 mmol / L, and the initial pH was set to 3. The glass tube was placed in a constant temperature oscillating box for degradation reaction at a temperature of 25°C and an oscillation speed of 150 rpm. Part of the solution was taken out at 5, 15, 30, 50 and 70 minutes in the reaction, filtered, and then an equal volume of methanol (chromatographic grade) was added to mix, and the chloramphenicol concentration was determined in a high performance liquid phase and the degradation efficiency was calculated.

[0052] Figure 1The results show that compared with SAC prepared from municipal sludge, the catalyst FeAC prepared from iron sludge has a significant effect on removing chloramphenicol. Among them, SAC basically cannot remove chloramphenicol, and FeAC has a removal rate of 80.7% for chloramphenicol in 5 minutes. The iron element in iron sludge is the source of divalent iron, trivalent iron, etc. in Fenton and Fenton-like reactions, and plays an important role in activating oxidants; the organic matter in iron sludge serves as a carbon source, forming a graphite carbon layer during the high-temperature-rapid annealing process of Joule heat technology, providing a carbon carrier for anchoring iron atoms, iron-containing nanoparticles, etc., and can improve their electron transfer ability in degradation reactions. Therefore, this method is feasible for iron sludge recovery.

[0053] Figure 2 The results show that the catalyst FePC obtained by the traditional pyrolysis method can basically not remove chloramphenicol. The iron-based catalysts FeDC and FePC prepared by different current reaction types in the Joule heat technology using iron mud can basically completely degrade chloramphenicol after 70 minutes (93.4% and 97.3%, respectively), and the degradation rate is fast, degrading more than 77% of chloramphenicol within 5 minutes (77.1% and 80.7%, respectively). Therefore, the iron-based catalyst obtained by the Joule heat technology has high efficiency and activity, which is of great significance for promoting the promotion and application of Fenton and Fenton-like technologies.

[0054] Example 2

[0055] (1) Material preparation: Dry the iron mud and grind it through an 80-mesh sieve; use wood chips as raw materials and pyrolyze them at 700°C for 120 minutes in a nitrogen atmosphere to obtain biochar. Grind and mix the treated iron mud and biochar in a mortar at a mass ratio of 1:1 to obtain a material precursor. Then, load the material precursor into a quartz tube, put graphite carbon rods at both ends, place the sample tube in a reaction box, and use a vacuum pump to extract the air to achieve an oxygen-free state. The reaction conditions are set as follows: the reaction type is alternating current, the voltage is set to 150V, when the sample mass is 0.1g, adjust the external resistance from 0 to 30Ω so that the total circuit resistance is 80±10Ω, the reaction time is 10 seconds, and the number of reactions is 1.

[0056] (2) Simulation of chloramphenicol wastewater degradation: In a glass tube, an iron-based catalyst with a final concentration of 0.5 g / L and sodium persulfate with a final concentration of 5 mmol / L were added to a chloramphenicol solution with a concentration of 80 mg / L in the reaction system, and different pH values ​​were set to 3, 5, 7, 9, and 11. The glass tube was placed in a constant temperature oscillation box for degradation reaction at a temperature of 25°C and an oscillation speed of 150 rpm. Part of the solution was taken out at 5, 15, 30, 50, and 70 minutes in the reaction, filtered, and then an equal volume of methanol (chromatographic grade) was added to mix. The chloramphenicol concentration was determined in a high performance liquid phase and the degradation efficiency was calculated. Under different pH conditions, the degradation effect of the iron-based catalyst prepared by iron mud on chloramphenicol is as follows: Figure 3 shown.

[0057] Figure 3 The results showed that the iron-based catalyst prepared by iron mud under Joule heat technology can effectively degrade chloramphenicol in water at different pH (pH 3, 5, 7, 9, 11). After 70 minutes, the degradation rates were 98.7%, 99.2%, 98.8%, 99.0% and 96.2%, respectively, demonstrating the wide application and effectiveness of the catalyst in the environment.

[0058] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a high-efficiency iron-based catalyst, characterized in that The method comprises the following steps: using iron mud as an iron source, using biochar as a carbon carrier, using a mixture of iron mud and biochar as a precursor, and using alternating current or direct current as a triggering method to obtain a high-efficiency iron-based catalyst; The iron sludge is the sludge produced after treating wastewater by Fenton or Fenton-like reaction.

2. The method for preparing a high-efficiency iron-based catalyst according to claim 1, characterized in that The steps include: (1) drying the iron mud to constant weight, crushing and sieving to obtain powder; (2) uniformly mixing the powder obtained in step (1) and biochar to obtain a material precursor; (3) Using Joule heat technology to treat the material precursor obtained in step (2) to obtain a high-efficiency iron-based catalyst.

3. The method for preparing a high-efficiency iron-based catalyst according to claim 2, characterized in that: The pulverizing method is grinding; The sieving is through an 80-mesh sieve; The biochar is prepared by hydrothermal method or pyrolysis method from at least one of forest dead branches, crop straw, edible fungus matrix, grain shells, fruit shells, urban garbage and sludge.

4. The method for preparing a high-efficiency iron-based catalyst according to claim 2, characterized in that: The powder and the biochar are mixed in a mass ratio of 0.5 to 10:

1.

5. The method for preparing a high-efficiency iron-based catalyst according to claim 2, characterized in that: The mixing method in step (2) is grinding; The treatment environment described in step (3) is an oxygen-free environment.

6. The method for preparing a high-efficiency iron-based catalyst according to claim 2, characterized in that: The parameters of the Joule heating technique described in step (3) are: A. The conditions of AC power are set as follows: voltage is 100-220V, reaction time is 1-10s, and reaction number is 1; B. The conditions of direct current are set as follows: voltage is 100-220V, number of reactions is 1-10 times, and each reaction time is 10-1000ms.

7. A high-efficiency iron-based catalyst, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the high-efficiency iron-based catalyst according to claim 7 in degrading organic pollutants.

9. The use according to claim 8, characterized in that The method comprises the following steps: adding the high-efficiency iron-based catalyst and oxidant described in claim 7 into organic pollutants for reaction.

10. The use according to claim 9, characterized in that: The organic pollutants include pesticides, antibiotics, dyes, detergents, and pesticides; The oxidant is at least one of hydrogen peroxide and persulfate; The dosage of the high-efficiency iron-based catalyst is 0.01-2 g / L; The dosage of the oxidant is 1-10 mmol / L.

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