A method for preparing and using a biochar-supported iron-copper bimetallic catalyst
By preparing a biochar-supported iron-copper bimetallic catalyst, the pH dependence and stability problems of the traditional Fenton process were solved, achieving efficient removal of organic pollutants and catalyst recovery, thus broadening the resource utilization pathways of black liquor and Fenton sludge.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN UNIV OF SCI & TECH
- Filing Date
- 2023-07-09
- Publication Date
- 2026-07-17
AI Technical Summary
Traditional Fenton processes require pH adjustment, have poor stability, and cannot efficiently utilize papermaking black liquor and Fenton sludge, resulting in low catalytic oxidation efficiency and the generation of large amounts of Fenton sludge.
Using papermaking black liquor acid precipitate, Fenton sludge, and divalent copper compounds as raw materials, a biochar-supported iron-copper bimetallic catalyst was prepared through pyrolysis-hydrothermal treatment, forming a structure with zero-valent iron as the core and iron(III) oxide as the shell. Nano-zero-valent copper coexists in the biochar, synergistically improving catalytic activity and stability.
It maintains high catalytic activity over a wide pH range, improving the removal efficiency of organic pollutants. Furthermore, it reduces metal ion leaching by separating and recovering the catalyst through magnetic field, thus achieving efficient resource utilization.
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Figure CN117000245B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of heterogeneous Fenton catalyst preparation and application and comprehensive utilization of waste resources, and in particular provides a method for preparing and using a biochar-supported iron-copper bimetallic catalyst. Background Technology
[0002] The Fenton advanced oxidation process primarily relies on iron-based catalysts to catalyze hydrogen peroxide to generate highly oxidizing hydroxyl radicals, thereby degrading organic pollutants in water. In recent years, it has been successfully applied to difficult-to-treat wastewater from industries such as dyes, pharmaceuticals, and papermaking. Although the traditional Fenton process using ferrous ions as a catalyst offers advantages such as rapid reaction and ease of operation, its narrow operating pH range (3-4) and the generation of large amounts of Fenton sludge limit its widespread application.
[0003] Ferric oxide (Fe3O4) possesses an inverse spinel structure, allowing for efficient electron transfer between ferrous and ferric iron at octahedral sites, thus promoting their interconversion. Consequently, ferric oxide nanoparticles exhibit excellent surface activity and good magnetic separation performance. As a heterogeneous catalyst for the Fenton reaction, ferric oxide nanoparticles have been successfully used in landfill leachate and dye wastewater treatment. However, ferric oxide nanoparticles suffer from easy aggregation and a significant decrease in catalytic activity under medium to high pH conditions, leading to reduced catalytic oxidation efficiency.
[0004] Black liquor is a cooking waste liquid produced during the alkaline pulping process in the papermaking industry. Its solids typically contain about two-thirds organic matter (including 30-40% alkali lignin) and one-third inorganic matter (mainly cooking waste liquid). Currently, black liquor is treated by burning the organic matter in the black liquor using alkali recovery technology to recover heat and chemicals. The traditional (homogeneous) Fenton treatment process is currently the most commonly used advanced treatment process for papermaking wastewater, but it generates a large amount of iron-containing sludge (i.e., Fenton sludge). How to more effectively utilize papermaking waste—black liquor and Fenton sludge—is a major environmental problem facing the papermaking industry. However, there are few reports on the preparation of high-performance catalysts using black liquor and Fenton sludge as main raw materials. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing and using a biochar-supported iron-copper bimetallic catalyst. Using papermaking black liquor acid precipitate, Fenton sludge, and divalent copper-based compounds as raw materials, a Fenton heterogeneous catalyst (biochar-supported iron-copper bimetallic catalyst) with a zero-valent iron core, a magnetite shell structure, and zero-valent copper coexisting in the biochar is prepared by pyrolysis-hydrothermal treatment. This solves the problems of traditional Fenton processes requiring pH adjustment, poor stability, and inability to be reused, while also broadening the pathways for efficient utilization of black liquor and Fenton sludge.
[0006] This invention is achieved through the following technical solution:
[0007] A method for preparing a biochar-supported iron-copper bimetallic catalyst, comprising the following steps:
[0008] (1) Mix the papermaking black liquor acid precipitate, Fenton sludge, divalent copper compounds and water in a certain proportion. After stirring the mixture for 2-6 hours, dry it at 105-110℃. Then crush the dried sample to less than 1 mm.
[0009] (2) The pulverized sample was pyrolyzed at 750-900℃ for 1-3 hours in an oxygen-free environment.
[0010] (3) The pyrolyzed sample was subjected to hydrothermal treatment together with an ethanol-water mixture;
[0011] (4) The hydrothermal treated sample was vacuum dried at 60°C, and the dried sample was pulverized to obtain a biochar-supported iron-copper bimetallic catalyst.
[0012] The ratio of the solids content of the black liquor precipitate to the iron mass in the Fenton sludge is 1.5-2.5, and the ratio of the iron mass in the Fenton sludge to the copper mass in the divalent copper compound is 1.5-3. The divalent copper compound is copper sulfate or copper nitrate, and the amount of water added ensures that the solids content in the mixture does not exceed 30%.
[0013] The volume ratio of ethanol to water in the ethanol-water mixture is 4:6-7:3, and the ratio of the mass (grams) of the pyrolysis sample to the volume (milliliters) of the ethanol-water mixture is 1:50-1:400.
[0014] The hydrothermal treatment is performed at a temperature of 180-240℃ for 12-24 hours.
[0015] A method for using a biochar-supported iron-copper bimetallic catalyst involves adding wastewater containing organic pollutants into a reactor without adjusting the pH of the wastewater. The biochar-supported iron-copper bimetallic catalyst and hydrogen peroxide are added to the reactor and stirred and mixed for reaction. After the reaction is complete, an electromagnet is used to separate and recover the biochar-supported iron-copper bimetallic catalyst.
[0016] The ratio of biochar-supported iron-copper bimetallic catalyst (g) to hydrogen peroxide (moles) is 10:1-200:1.
[0017] Compared with the prior art, the present invention has the following advantages:
[0018] (1) This invention uses papermaking black liquor, Fenton sludge, and divalent copper compounds as raw materials. Under the conditions specified in this invention, pyrolysis can yield a catalyst supported on biochar with nano-zero-valent iron and nano-zero-valent copper. Further hydrothermal treatment can convert the surface of nano-zero-valent iron into nano-iron oxide, resulting in a Fenton catalyst (biochar-supported iron-copper bimetallic catalyst) with nano-zero-valent iron as the core, nano-iron oxide as the shell, and nano-zero-valent copper coexisting in the biochar. Biochar promotes the adsorption of organic pollutants and increases the concentration of pollutants near the catalytic active sites. Under the combined action of biochar, nano-zero-valent iron, and nano-zero-valent copper, the conversion of ferric iron to ferrous iron is promoted in the heterogeneous catalysis process of nano-iron oxide, thereby improving the catalytic activity of nano-iron oxide. Nano-zero-valent copper has high catalytic activity over a wide pH range. Therefore, under the synergistic effect of nano-iron oxide, nano-zero-valent iron, nano-zero-valent copper, and biochar, the adsorption-catalytic oxidation performance of the catalyst is improved.
[0019] (2) Biochar and the shell-core structure improve the stability of the catalyst and slow down the leaching of metal ions during Fenton oxidation.
[0020] (3) During the preparation process, the iron element in Fenton sludge can be converted into paramagnetic iron(III) oxide and zero-valent iron, and the iron-copper bimetallic catalyst supported on biochar can be separated and recovered by magnetic field (such as electromagnet). Attached Figure Description
[0021] Figure 1 X-ray diffraction pattern of a biochar-supported iron-copper bimetallic catalyst
[0022] Figure 2 Transmission electron microscopy image of a biochar-supported iron-copper bimetallic catalyst Detailed Implementation
[0023] The present invention will be further described below with reference to specific embodiments. However, it should be noted that these embodiments are only used to illustrate the present invention and do not limit the scope of the present invention. Any modifications or alterations made to the present invention by those skilled in the art after reading the detailed contents of the present invention should fall within the scope of the present invention.
[0024] Example 1:
[0025] Papermaking black liquor was acid-precipitated by adjusting the pH to 8 with dilute sulfuric acid, and the resulting product was dehydrated to obtain the papermaking black liquor precipitate. The precipitate, Fenton sludge, copper nitrate, and water were thoroughly mixed in a specific ratio and stirred for 2 hours. The mixture was then dried at 110°C, and the dried sample was pulverized to a size less than 1 mm. The ratio of the solids content of the precipitate to the iron mass in the Fenton sludge was 1.5, the ratio of the iron mass in the Fenton sludge to the copper mass in the copper nitrate was 3, and the amount of water added resulted in a solids content of 20%. The pulverized sample was then anaerobically pyrolyzed at 800°C for 2 hours. The pyrolyzed sample was then hydrothermally treated with an ethanol-water mixture. The volume ratio of ethanol to water in the ethanol-water mixture was 6.5:3.5, the ratio of the mass (g) of the pyrolyzed sample to the volume (ml) of the ethanol-water mixture was 1:300, and the hydrothermal treatment temperature was 180°C for 24 hours. The hydrothermally treated sample was vacuum dried at 60℃, and the dried sample was pulverized to obtain a biochar-supported iron-copper bimetallic catalyst. The X-ray diffraction pattern is shown below. Figure 1 As shown. Transmission electron microscope image as follows. Figure 2 As shown. The saturation magnetization is 40.5 emu / g.
[0026] Wastewater containing 10 mg / L Rhodamine B dye was added to a reactor. A biochar-supported iron-copper bimetallic catalyst and hydrogen peroxide were then added and stirred to react. After the reaction was complete, the biochar-supported iron-copper bimetallic catalyst was separated and recovered using an electromagnet. The amounts of biochar-supported iron-copper bimetallic catalyst and hydrogen peroxide were 0.2 g / L and 0.001 mol / L, respectively, meaning the ratio of biochar-supported iron-copper bimetallic catalyst (g) to hydrogen peroxide (mol) was 200:1. The removal rate of Rhodamine B reached 100%, and after five reuses, the removal rate still reached 98%. The iron leaching concentration was less than 0.1 mg / L, and the copper leaching concentration was less than 0.5 mg / L.
[0027] Example 2:
[0028] Papermaking black liquor was acid-precipitated by adjusting the pH to 9 using flue gas, and the resulting product was dehydrated to obtain the papermaking black liquor acid precipitate. The papermaking black liquor acid precipitate, Fenton sludge, copper sulfate, and water were thoroughly mixed in a specific ratio. After stirring for 6 hours, the mixture was dried at 105℃, and then pulverized to a size less than 1 mm. The ratio of the solids content of the papermaking black liquor acid precipitate to the iron mass in the Fenton sludge was 2.5, the ratio of the iron mass in the Fenton sludge to the copper mass in the copper nitrate was 1.5, and the amount of water added resulted in a solids content of 30%. The pulverized sample was then anaerobically pyrolyzed at 900℃ for 1 hour. The pyrolyzed sample was then hydrothermally treated with an ethanol-water mixture. The volume ratio of ethanol to water in the ethanol-water mixture was 4.5:5.5, the ratio of the mass (g) of the pyrolyzed sample to the volume (ml) of the ethanol-water mixture was 1:70, and the hydrothermal treatment temperature was 240℃ for 12 hours. The hydrothermally treated sample was vacuum dried at 60℃, and the dried sample was pulverized to obtain a biochar-supported iron-copper bimetallic catalyst. Its saturation magnetization was 62.5 emu / g.
[0029] Paper mill wastewater (secondary sedimentation tank effluent, COD) Cr =200mg / L) was added to the reactor, followed by the addition of biochar-supported iron-copper bimetallic catalyst and hydrogen peroxide. The mixture was stirred and stirred until the reaction was complete. After the reaction, the biochar-supported iron-copper bimetallic catalyst was separated and recovered using an electromagnet. The amounts of biochar-supported iron-copper bimetallic catalyst and hydrogen peroxide were 0.3g / L and 0.012mol / L, respectively, i.e., the ratio of iron-based heterogeneous catalyst (g) to persulfate (mol) was 25:1. The COD of the treated wastewater was... Cr With a concentration less than 50 mg / L, COD levels decreased after 5 reuses. Cr The concentration is still less than 60 mg / L. The iron leaching concentration is less than 0.1 mg / L, and the copper leaching concentration is less than 1 mg / L.
Claims
1. A method for preparing a biochar-supported iron-copper bimetallic catalyst, characterized in that, The steps are as follows: (1) The black liquor of papermaking is acidified at pH 8 or 9, and after dehydration, the black liquor acidified product of papermaking is obtained. Then, the black liquor acidified product of papermaking, Fenton sludge, divalent copper compound and water are fully mixed in a certain proportion. After stirring for 2-6 hours, the mixture is dried at 105-110℃. Then, the dried sample is crushed to less than 1 mm. (2) The pulverized sample is subjected to anaerobic pyrolysis at 750-900℃ for 1-3 hours; (3) The pyrolyzed sample was subjected to hydrothermal treatment together with the ethanol-water mixture; (4) The hydrothermal treated sample was vacuum dried at 60°C, and the dried sample was pulverized to obtain a biochar-supported iron-copper bimetallic catalyst.
2. The method for preparing a biochar-supported iron-copper bimetallic catalyst as described in claim 1, characterized in that, The ratio of the solid content of the black liquor acid precipitate to the iron mass in the Fenton sludge is 1.5-2.5, the ratio of the iron mass in the Fenton sludge to the copper mass in the divalent copper compound is 1.5-3, the divalent copper compound is copper sulfate or copper nitrate, and the amount of water added is such that the solid content in the mixture does not exceed 30%.
3. The method for preparing a biochar-supported iron-copper bimetallic catalyst as described in claim 1, characterized in that, The volume ratio of ethanol to water in the ethanol-water mixture is 4:6-7:3, and the ratio of the mass of the pyrolysis sample to the volume of the ethanol-water mixture is 1 g:50 ml to 1 g:400 ml.
4. The method for preparing a biochar-supported iron-copper bimetallic catalyst as described in claim 1, characterized in that, The hydrothermal treatment temperature is 180-240℃, and the time is 12-24 hours.
5. A method of using a biochar-supported iron-copper bimetallic catalyst prepared by the method according to any one of claims 1-4, characterized in that, Wastewater containing organic pollutants is added to the reactor without adjusting the pH of the wastewater. Biochar-supported iron-copper bimetallic catalyst and hydrogen peroxide are added to the reactor and stirred and mixed. After the reaction is completed, an electromagnet is used to separate and recover the biochar-supported iron-copper bimetallic catalyst.
6. The method of using the biochar-supported iron-copper bimetallic catalyst as described in claim 5, characterized in that, The ratio of biochar-supported iron-copper bimetallic catalyst to hydrogen peroxide is 10 g: 1 mole to 200 g: 1 mole.