Method for preparing confined iron-based porous carbon catalyst from compound extracted from printing and dyeing alkali decrement white mud and application of confined iron-based porous carbon catalyst

Abstract

The invention discloses a method for preparing a confined iron-based porous carbon catalyst from a compound extracted from printing and dyeing alkali-decrement white mud and application of the confined iron-based porous carbon catalyst. The specific method is as follows: the printing and dyeing alkali-decrement white mud is uniformly dispersed in an organic solvent, filtrate containing terephthalic acid is extracted through oscillation and suction filtration, then ferric trichloride hexahydrate is dropped into the filtrate, and the filtrate is filtered to obtain the confined iron-based porous carbon catalyst. Performing stirring hydrolysis and hydrothermal reaction to synthesize an MIL-101 (Fe)-W precursor, and performing pyrolysis in an inert atmosphere to obtain the confined iron-based porous carbon catalyst Fe (at) C-W. The catalyst has a high specific surface area and a confinement structure, and the prepared catalyst can be used for activating hydrogen peroxide to degrade organic pollutants. The industrial waste is recycled, and the catalyst is high in degradation efficiency, suitable for a wide pH range and good in stability.

Description

Technical Field

[0001] This invention belongs to the field of organic pollutant treatment technology, specifically relating to a method for preparing confined iron-based porous carbon catalysts from compounds extracted from dyeing alkali-reduced white mud, and its application. Background Technology

[0002] Organic pollutants, such as benzene compounds (including benzene, toluene, chlorobenzene, etc.) and chlorophenols (such as p-chlorophenol), are common harmful substances in industrial wastewater, characterized by high toxicity, environmental persistence, and bioaccumulation. Traditional removal technologies mainly include adsorption and reduction methods.

[0003] Adsorption method: This method uses activated carbon or resin materials to remove pollutants through physical adsorption, and has the advantages of simple equipment and high removal rate. However, the adsorption process only achieves phase transfer of pollutants and does not completely degrade them, which can easily lead to secondary pollution. At the same time, it has poor selectivity, and its efficiency decreases when high concentrations of coexisting organic matter are present.

[0004] Reduction dechlorination technology, such as zero-valent iron reduction, can partially degrade chlorinated organic compounds, but the reaction rate is slow, it is easily passivated, and it may produce intermediate products, posing environmental risks.

[0005] In recent years, metal-organic frameworks (MOFs) have attracted attention due to their high specific surface area, tunable pore structure, and catalytic activity. MOFs (such as iron-based MOFs) can be used as precursors to prepare porous carbon catalysts, theoretically improving pollutant mass transfer efficiency and active site exposure. Furthermore, confined structure design (such as encapsulating active components in porous supports) has been shown to suppress nanoparticle aggregation and enhance selectivity and stability. Current confined-domain techniques include zeolite-confined metal clusters and carbon nanotube-encapsulated catalysts, but these methods suffer from complex preparation processes and high costs, limiting large-scale applications.

[0006] The alkali-reduction sludge produced by the dyeing and printing industry is rich in terephthalic acid (BDC) and oligomers. Traditional treatment methods include landfilling or incineration, which have not achieved high-value utilization. Although some studies have attempted to extract BDC from sludge, research on its use in preparing high-performance catalysts is still insufficient.

[0007] These shortcomings collectively limit the efficiency, economic viability, and sustainability of organic pollutant treatment technologies. Therefore, there is an urgent need to develop a low-cost, efficient, and stable catalyst preparation method that can both achieve deep degradation of pollutants and promote the resource utilization of industrial waste. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a method for preparing confined iron-based porous carbon catalysts from compounds extracted from dyeing and printing alkali-reduced white mud, and its application.

[0009] The specific technical solution is as follows: A method for preparing confined iron-based porous carbon catalysts from compounds extracted from dyeing alkali-reduced white mud includes the following steps: S1. Disperse the alkali-reduced white mud evenly in an organic solvent, shake, and filter to obtain a filtrate containing terephthalic acid and oligomers. S2. Ferric chloride hexahydrate was added dropwise to the filtrate containing terephthalic acid and oligomers from step S1 under stirring. After the addition was complete, the mixture was stirred and hydrolyzed, and then transferred to a hydrothermal reactor lined with polytetrafluoroethylene for hydrothermal reaction. The resulting reaction solution was separated and washed to obtain the MIL-101(Fe)-W precursor. The MIL-101(Fe)-W precursor was then pyrolyzed in an inert gas to obtain the confined iron-based porous carbon catalyst Fe@CW.

[0010] The white sludge from alkali reduction in dyeing and printing originates from the following process: In the alkali reduction process, the weight reduction rate of polyester fabrics is generally 5-20%. This waste material enters the wastewater in the form of terephthalic acid, ethylene glycol, and polyester oligomers. To separate the terephthalic acid from the wastewater, acid precipitation treatment is performed. Concentrated sulfuric acid is used to adjust the pH to 3-5, converting sodium terephthalate into terephthalic acid with extremely low solubility, which then precipitates out. Simultaneously, coagulants such as polyferric sulfate / polyaluminum chloride are used to promote the sedimentation process of terephthalic acid flocs. Finally, the precipitate is dewatered using a plate and frame filter press to form the white sludge from alkali reduction in dyeing and printing. Further, the organic solvent in step S1 is N,N-dimethylformamide solvent (DMF), and the volume of the organic solvent is 30-100 mL / g based on the mass of the white mud used for dyeing and printing alkali reduction.

[0011] Furthermore, the oscillation in step S1 is carried out in a multi-tube vortex mixer with oscillation conditions of 60W, a rotation speed of 2500rpm, and an oscillation time of 0.5-2h.

[0012] Furthermore, in step S2, the hydrothermal reaction temperature is 115-125℃, the hydrothermal reaction time is 24 hours, the pyrolysis temperature is 800℃, and the time is 330-360 minutes.

[0013] Furthermore, in step S2, the molar ratio of terephthalic acid to ferric chloride hexahydrate in the filtrate containing terephthalic acid and oligomers is 1:1 to 1:2.

[0014] An application of a confined iron-based porous carbon catalyst prepared by the above method in the removal of p-chlorophenol using activated hydrogen peroxide includes the following steps: adjusting the pH of the p-chlorophenol-containing contaminant to 3-9, adding hydrogen peroxide as an oxidant to the p-chlorophenol-containing contaminant, and then adding the confined iron-based porous carbon catalyst Fe@CW for treatment. In Fe@CW material, the presence of oligomers forms a confined structure, allowing hydrogen peroxide and organic contaminants to enter the confined structure. Within the confined structure, the probability of contact between hydrogen peroxide and iron increases, enhancing the generation of hydroxyl radicals and simultaneously increasing the contact between hydroxyl radicals and organic contaminants, thus accelerating the degradation of contaminants. In contrast, in Fe@C, hydrogen peroxide can only contact the Fe active sites on the material surface to generate hydroxyl radicals, which then contact the organic contaminants in the solution to achieve degradation. This results in a lower yield of hydroxyl radicals and a lower probability of contact with organic contaminants, thus Fe@CW is more effective.

[0015] The beneficial effects of this invention are as follows: 1) In this invention, the BDC contained in the alkali-reduced white mud of printing and dyeing is recycled and utilized. Fe@CW is prepared by pyrolysis to produce MIL-101(Fe)-W precursor, thus realizing effective resource reuse. 2) The catalyst prepared by this invention has a good degradation effect on p-chlorophenol pollutants in the H2O2 system; 3) The Fe@CW material prepared by pyrolysis in this invention also exhibits good degradation performance under common anion interference conditions; 4) The Fe@CW material prepared by pyrolysis in this invention exhibits good degradation performance under a wide range of pH conditions; 5) The Fe@CW material prepared by pyrolysis in this invention still has a good degradation effect after 8 cycles, and has good stability; 6) The Fe@CW material prepared by pyrolysis in this invention maintains a certain reactivity in a series of actual wastewaters. Attached Figure Description

[0016] Figure 1 The degradation effects of catalysts prepared under different extraction conditions; Figure 2 Isotherms of nitrogen adsorption and desorption for Fe@C and Fe@CW; Figure 3 The Fe content before and after pickling for Fe@C and Fe@CW; Figure 4 Graphs showing the effects of different catalysts on the removal of p-chlorophenol by hydrogen peroxide; Figure 5 The effects of removing chlorophenol and recycling under different pH conditions; Figure 6 The effect of Fe@CW activated hydrogen peroxide on the removal of p-chlorophenol under different coexisting ions; Figure 7 The effect of Fe@C and Fe@CW activated hydrogen peroxide on the removal of various organic pollutants; Figure 8 This is the result of the EPR test; Figure 9 These are the results of the probe experiment. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited thereto.

[0018] Example 1

[0019] Fe@C material prepared by synthesis of pure BDC: 0.43 g of BDC was weighed and added to 45 mL of DMF, and sonicated for at least 20 minutes to ensure dissolution of BDC. The 45 mL solution was then transferred to the lining of a 100 mL hydrothermal reactor, and 5 mM ferric chloride hexahydrate was gradually added dropwise under vigorous stirring, with a molar ratio of BDC to Fe source of 1:2. After the ferric chloride hexahydrate dissolved, the hydrothermal reactor was maintained at 120 °C for 24 hours. After cooling to room temperature, the mixture was washed several times by centrifugation with DMF and methanol, and then dried in a vacuum drying oven at 60 °C to obtain the MIL-101(Fe) precursor. The precursor was then pyrolyzed at 800 °C under an argon atmosphere for 360 min to obtain Fe@C.

[0020] Synthesis of Fe@CW material: 0.65 g of white clay solid was added to 45 mL of N,N-dimethylformamide (DMF) and vortexed for 1 h using a multi-tube vortex mixer (QL-866, 60 W, 2500 rpm). The mixture was then filtered using a vacuum filtration device. The resulting filtrate was a solution containing BDC (concentration 67 wt% as determined by HPLC). 45 mL of the filtrate was then transferred to the lining of a 100 mL hydrothermal reactor. 5 mM ferric chloride hexahydrate was gradually added dropwise under vigorous stirring, with a BDC to Fe source molar ratio of 1:2. After the ferric chloride hexahydrate dissolved, the hydrothermal reactor was maintained at 120 °C for 24 hours. After cooling to room temperature, the precursor was washed several times by centrifugation with DMF and methanol, and then dried in a vacuum drying oven at 60°C to obtain the MIL-101(Fe)-W precursor. The precursor was then pyrolyzed at 800°C under an argon atmosphere for 360 min to obtain the confined iron-based porous carbon catalyst Fe@CW.

[0021] The N2 adsorption-desorption isotherms of the two materials were fitted, and the Fe content before and after acid washing was compared. For Fe@CW and Fe@C, 100 mg of the material was weighed and added to a 100 ml beaker, followed by 50 ml of 1M hydrochloric acid. After standing for 48 hours, the mixture was separated, dried, and then sent to ICP for Fe elemental analysis. The results are as follows: Figure 2 As shown, the specific surface area of ​​Fe@C material is 1.5 times that of Fe@CW material. Figure 3 As shown, the Fe content of Fe@CW and Fe@C decreased from 59wt% to 12.1wt% after pickling and 60wt% to 1.4wt% after pickling, respectively. This is because a portion of Fe@CW is encapsulated by C to form a confined structure.

[0022] Example 2

[0023] Comparison of degradation effects of catalysts prepared under different preparation conditions In Example 1, the 45 mL N,N-dimethylformamide used in the synthesis of Fe@CW material was replaced with 35 mL N,N-dimethylformamide, while other operations remained unchanged, to prepare the confined iron-based porous carbon catalyst Fe@CW-35 mL.

[0024] By replacing the 1 h oscillation in the Fe@CW material synthesis process in Example 1 with 30 min oscillation, and keeping other operations unchanged, the confined iron-based porous carbon catalyst Fe@CW-30min was prepared.

[0025] The results are as follows Figure 1 As shown, from Figure 1 It can be observed that insufficient organic solvent leads to inadequate oligomer content, and insufficient ultrasonic time leads to incomplete oligomer extraction. Both of these factors make it difficult for confined structures to form. When DMF is too low and ultrasonic time is too short, the degradation effect of the prepared material on organic pollutants will be significantly weakened.

[0026] Example 3

[0027] Different catalysts activate hydrogen peroxide to remove p-chlorophenol The Fe@CW sample synthesized in Example 1 was characterized by ICP. The iron content in Fe@CW was found to be 60.01 wt.%, and the iron content in 0.005 g of Fe@CW was calculated to be equivalent to 0.00429 g of Fe2O3, 0.00417 g of Fe3O4, and 0.00384 g of FeO.

[0028] The reaction vessel was set as a 250mL beaker. Five beakers were used, and 100mL of a 20mg / L p-chlorophenol solution was added to each beaker as a contaminant. Hydrogen peroxide (concentration after addition was 3mM) was added as an oxidant. 0.005g of Fe@CW, 0.005g of Fe@C, 0.00429g of Fe2O3, 0.00417g of Fe3O4, and 0.00384g of FeO were added to each of the five beakers respectively. A certain amount of water was taken at regular intervals to measure the p-chlorophenol content. The reaction time was 90 minutes. Figure 4 As shown, Fe@CW has significant advantages in the degradation of p-chlorophenol.

[0029] Example 4

[0030] The effect of pH on the removal of p-chlorophenol by Fe@CW-activated H2O2 and its effect after multiple cycles The pH of all the above examples was 4. As is well known, iron-based reactions depend on pH conditions. Therefore, the initial pH was adjusted to 3, 6 and 9 respectively for the experiments.

[0031] Take three beakers and add 100 ml of 20 mg / L p-chlorophenol solution as the contaminant. Adjust the pH to 3, 6, and 9 respectively. Then add 0.005 g of Fe@CW and hydrogen peroxide (3 mM concentration after addition) to each beaker to initiate the reaction. Take a certain amount of water sample at regular intervals and measure the p-chlorophenol content. The reaction time is one hour. Figure 5 In the data, "control" refers to the degradation effect under the following conditions: 100 ml of 20 mg / L p-chlorophenol solution as the pollutant, 0.005 g of Fe@CW, and the addition of hydrogen peroxide (concentration after addition is 3 mM), at pH 4; TAP represents tap water, and MW represents simulated wastewater. It can be seen that Fe@CW maintains a high removal rate under acidic, neutral, and weakly alkaline conditions, and still shows good performance after 8 cycles.

[0032] Example 5

[0033] Fe@CW activated hydrogen peroxide removes p-chlorophenol under conditions of coexistence of different ions To prepare a p-chlorophenol solution, different ions were added to ultrapure water. Three beakers were used, each containing p-chlorophenol solutions prepared with different concentrations of ions. The pH was adjusted to 4, and then 0.005 g of Fe@CW and 3 mM hydrogen peroxide were added sequentially to initiate the reaction. A water sample was taken at regular intervals to measure the p-chlorophenol content. The reaction time was one hour. Figure 6As shown in the figure (the concentrations in the figure are the concentrations after addition), the reaction between Fe@CW and hydrogen peroxide maintains high activity even under different concentrations of coexisting ions. "Control" refers to the degradation effect under the following conditions: 100 ml of 20 mg / L p-chlorophenol solution as the pollutant, 0.005 g of Fe@CW, addition of hydrogen peroxide (concentration after addition: 3 mM), and pH 4.

[0034] Example 6

[0035] Removal of various organic pollutants by Fe@CW and Fe@C activated hydrogen peroxide Take a beaker and add 100 ml of a 20 mg / L organic pollutant solution as the pollutant. Adjust the pH to 4, then add 0.005 g of Fe@CW and 3 mM hydrogen peroxide sequentially to initiate the reaction. Take a water sample at regular intervals and measure the organic pollutant content. The reaction time is one hour. The Fe@C experiment is similar to the Fe@CW experiment; simply replace Fe@CW with Fe@C. Figure 7 As shown, Fe@CW is far more effective than Fe@C in removing a variety of organic pollutants. Figure 7 The pollutants in the middle are Styrene, 4-CP (p-chlorophenol), BPA (bisphenol A), Phenylamine, 2,3-DCP (2,3-dichlorophenol), and 2,4-DCP (2,4-dichlorophenol).

[0036] Example 7

[0037] EPR detection EPR capture experiments utilize various capture agents to capture different free radicals, simultaneously forming capture agent-radical complexes. These complexes are detectable by the instrument and exhibit peak shapes with specific area ratios. In this EPR capture experiment, 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) was used as the capture agent. This agent can capture hydroxyl radicals and form DMPO−OH. DMPO−OH is detectable by the instrument, forming peaks with a 1:2:2:1 ratio. The presence of a 1:2:2:1 peak in the EPR chromatogram indicates the formation of hydroxyl radicals in the system. Figure 8 As shown, there are obvious DMPO−OH peaks at 20 minutes and 40 minutes, proving that more hydroxyl radicals are generated in the system and that Fe@C produces more hydroxyl radicals compared to Fe@CW.

[0038] Example 8

[0039] Probe experiments for hydroxyl group determination with Fe@CW and Fe@C benzoic acid Take two beakers, add 100ml of pure water, adjust the pH to 4, and add 0.005g of Fe@CW and Fe@C respectively, along with hydrogen peroxide (3mM concentration after addition). Finally, add 3mM (concentration after addition) of benzoic acid to initiate the reaction. Take a water sample at regular intervals to measure the p-hydroxybenzoic acid content. The reaction time is one hour. Figure 9 As shown, the hydroxyl concentration gradually increases with time, and Fe@CW produces more hydroxyl groups compared to Fe@C. This is consistent with the EPR results in Example 7.

Claims

1. A method for preparing confined iron-based porous carbon catalysts from compounds extracted from dyeing and printing alkali-reduced white mud, characterized in that, Includes the following steps: S1. Disperse the dyeing alkali-reduced white mud evenly in an organic solvent, shake, and filter to obtain a filtrate containing terephthalic acid and oligomers; S2. Ferric chloride hexahydrate was added dropwise to the filtrate containing terephthalic acid and oligomers from step S1 under stirring. After the addition was complete, the mixture was stirred and hydrolyzed, and then transferred to a hydrothermal reactor lined with polytetrafluoroethylene for hydrothermal reaction. The resulting reaction solution was separated and washed to obtain the MIL-101(Fe)-W precursor. The MIL-101(Fe)-W precursor was then pyrolyzed in an inert gas to obtain the confined iron-based porous carbon catalyst Fe@CW.

2. The method for preparing confined iron-based porous carbon catalyst from white mud extracted by reducing alkali in dyeing and printing as described in claim 1, characterized in that, The organic solvent in step S1 is N,N-dimethylformamide, and the volume of the organic solvent is 30-100 mL / g based on the mass of the white mud used for dyeing and printing alkali reduction.

3. The method for preparing confined iron-based porous carbon catalyst from white mud extracted by reducing alkali in dyeing and printing as described in claim 1, characterized in that, The oscillation in step S1 is carried out in a multi-tube vortex mixer under the following conditions: 60 W, 2500 rpm, and 0.5-2 h.

4. The method for preparing confined iron-based porous carbon catalyst by extracting compounds from dyeing and printing alkali-reduced white mud as described in claim 1, characterized in that, The hydrothermal reaction in step S2 is carried out at a temperature of 115-125℃ for 24 hours, and the pyrolysis temperature is 800℃ for 330-360 minutes.

5. The method for preparing confined iron-based porous carbon catalyst from compounds extracted from dyeing and printing alkali-reduced white mud as described in claim 1, characterized in that, In step S2, the molar ratio of terephthalic acid to ferric chloride hexahydrate in the filtrate containing terephthalic acid and oligomers is 1:1 to 1:

2.

6. The application of a confined iron-based porous carbon catalyst prepared by any one of the methods described in claims 1-5 in the removal of p-chlorophenol by activated hydrogen peroxide, characterized in that, The process includes the following steps: adjusting the pH of the pollutant containing p-chlorophenol to 3-9, adding hydrogen peroxide as an oxidant to the pollutant containing p-chlorophenol, and then adding the confined iron-based porous carbon catalyst Fe@CW for treatment.

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