A modified carbon-based calcium-iron layered double hydroxide catalyst, preparation and application thereof

Abstract

The present application relates to a modified carbon-based calcium-iron layered double hydroxide catalyst and its preparation and application, characterized in that the catalyst is composed of a carrier and a layered double hydroxide, the carrier is activated carbon fiber ACF, and the layered double hydroxide is calcium-iron layered double hydroxide; wherein the loading mass percentage of Ca element is 2.26-5.16%, the molar ratio of Ca 2+ and Fe 3+ is (2-5):1; the total specific surface area of the catalyst is 1000-1600 m 2 ·g ‑1 ; the pore volume is 0.60-0.90 cm 3 ·g ‑1 ; and the average pore size is 1-3 nm. The catalyst in the present application can efficiently activate PMS to selectively oxidize SMX in wastewater under a wide range of pH conditions, has a fast degradation rate, is convenient to recover, has a high reusability, and has a high economic benefit.

Description

Technical Field

[0001] This invention relates to a modified carbon-based calcium-iron layered bimetallic hydroxide catalyst, its preparation and application, belonging to the fields of antibiotic wastewater treatment processes and catalytic materials and preparation, specifically applied to the selective oxidation of SMX by activated PMS in antibiotic wastewater. Background Technology

[0002] Sulfamethoxazole (SMX) is one of the most commonly used broad-spectrum antibiotics in the sulfonamide class, possessing advantages such as strong hydrophilicity, low cost, and a broad antibacterial spectrum. Due to its antibacterial activity against a variety of pathogens, the demand for sulfamethoxazole in daily life is gradually increasing. As one of the most commonly used antibiotics, sulfamethoxazole residues in the aquatic environment pose a significant threat to the health of humans and other animals and plants. Long-term accumulation in the human body may cause kidney damage, drug resistance, carcinogenicity, and mutagenicity, posing a serious health risk. Therefore, developing efficient treatment technologies to remove residual sulfamethoxazole from water has gradually become a focus of attention.

[0003] Sulfamethoxazole is a recalcitrant substance. Current treatment technologies for sulfamethoxazole mainly include biological methods, physiochemical methods, advanced oxidation technologies, and combinations of these methods. Research results show that the adsorption of sulfonamide antibiotics by activated sludge in secondary biological treatment is the most important pathway for sulfonamide antibiotic removal in the entire treatment process. Therefore, if traditional wastewater treatment processes and sludge discharge do not employ corresponding advanced treatment processes, residual sulfonamide antibiotics will be discharged into water bodies and soil environments along with the effluent and excess sludge from wastewater treatment plants, leading to serious antibiotic pollution of surface water, groundwater, and farmland soil. Many antibiotic wastewaters, after biological treatment, can generally meet biochemical standards, but a certain amount of recalcitrant antibiotics and their byproducts still remain, posing a potential threat to aquatic ecosystems. Physicochemical methods, especially advanced oxidation treatments, can effectively reduce the low concentrations of residual sulfonamide antibiotics in water bodies. Physicochemical methods offer significantly improved efficiency and time compared to biological methods, but their biggest disadvantage is the relatively high cost. In recent years, advanced oxidation methods based on sulfate radicals have also been frequently used for the degradation of sulfamethoxazole. Sulfate radicals can be obtained by catalytic persulfate (PMS) through thermal activation, alkali activation, ultrasonic activation, and transition metal ion activation. In homogeneous systems, they can be obtained through transition metal ion activation (Co). 2+ Mn 2+ Fe 2+(e.g., activating persulfate); in heterogeneous systems, there are various heterogeneous catalysts such as zero-valent iron, single metal oxides, composite metal oxides, supported metal materials, and metal-free carbon materials; external energy fields (light, sound, electricity, heat) can also directly activate persulfate or assist in improving reaction efficiency. While transition metal activation is simple and economical, it releases large amounts of metal ions, causing secondary pollution and limiting the widespread application of PMS in water treatment. Therefore, developing efficient and economical physicochemical or combined treatment technologies is an effective way to achieve effective degradation of sulfamethoxazole wastewater and reduce environmental safety hazards.

[0004] Compared to traditional advanced oxidation technologies, oxidation technologies based on non-radical reactions have a milder oxidation capacity, higher selectivity, and are less affected by environmental substrates, making them a promising technology for water treatment. Non-radical reactions with milder oxidation capacity discovered in persulfate-activated systems are beneficial for the rapid mineralization of organic pollutants in natural water bodies and actual wastewater substrates. The non-radical reaction mechanism of persulfate-activated oxidation of organic pollutants mainly includes: (1) formation of surface-activated complexes (or surface-confined radicals); (2) promotion of electron transfer; (3) generation of singlet oxygen (…). 1 (O2). This type of non-radical reaction pathway has been mainly found in carbon-based activated persulfate systems. Carbon materials with high specific surface area, good conductivity, and stable chemical properties are commonly used as catalyst supports. However, studies have found that carbon materials themselves, or carbon materials with surface modification and heteroatom doping, possess excellent ability to activate persulfates. By simply adjusting the doping and defect levels of carbon catalysts, the oxidation level of the reaction can be controlled: from mild and selective oxidation via non-radical pathways to deep and non-selective oxidation via radical pathways. Wastewater generally has a complex composition, with many coexisting matrix types and high concentrations, significantly interfering with the removal of target pollutants. Excessive PMS dosage or energy input is often required to effectively remove trace amounts of target pollutants. This not only significantly increases treatment costs but also easily generates toxic byproducts, increasing environmental risks. Therefore, developing selective activated PMS oxidation technology is of great significance for technological innovation in advanced water treatment. Based on the above research status, the idea of ​​this invention is to load metal or its oxide particles with special catalytic activity onto carbon materials with high electrical conductivity and strength, which will help enhance the stability and dispersibility of the metal materials, solve the problem of easy agglomeration during catalysis, improve the catalytic activity and service life of the catalyst, and avoid the release of free metal ions during the process.

[0005] In the field of activated PMS oxidative degradation of sulfamethoxazole, Ji et al. studied the efficiency of thermally activated persulfate technology based on sulfate radicals in degrading sulfonamide antibiotics. The results showed that sulfonamide antibiotics were rapidly and efficiently degraded, with sulfate radicals being the dominant oxidizing agent, and they selectively oxidized the aniline groups on sulfonamide antibiotics. Wu et al. studied the efficiency of three different systems—UV-activated persulfate, bromate, and hydrogen peroxide—in degrading four sulfonamide antibiotics. The results showed that different systems had different degradation efficiencies for different antibiotics, but UV-activated persulfate showed the highest mineralization rate for all four selected sulfonamide antibiotics, demonstrating that this system can generate strong oxidizing free radicals, thereby deeply mineralizing sulfonamide antibiotics. Nfodzo P et al. used metal ions Fe... 2+ Activated PMS degrades SMX in [SMX]:[PMS]:[Fe 2+ The removal rate reached 95% after 180 minutes of treatment under conditions of 1:80:80 ratio, SMX concentration of 9 mg / L, and pH = 7; Co metal ions were used. 2+ Instead of Fe 2+ In [SMX]:[PMS]:[Co 2+ With a ratio of 1:10:10, an SMX concentration of 9 mg / L, and a pH of 7, the removal rate was close to 100% after 180 minutes of treatment. Summary of the Invention

[0006] The purpose of this invention is to provide a modified carbon-based calcium-iron layered bimetallic hydroxide catalyst (CaFe-LDH / ACF, abbreviated as CFLA). Another purpose of this invention is to provide a method for preparing the above catalyst and to provide the application of the above catalyst in activating PMS to degrade SMX in antibiotic wastewater.

[0007] The technical solution of this invention is as follows: A modified carbon-based calcium-iron layered bimetallic hydroxide catalyst, characterized in that the catalyst is composed of a support and a layered bimetallic hydroxide, wherein the support is activated carbon fiber (ACF), and the layered bimetallic hydroxide is a calcium-iron layered bimetallic hydroxide; wherein the mass percentage of Ca element loading is 2.26–5.16%, and Ca… 2+ and Fe 3+ The molar ratio is (2-5):1; the total specific surface area of ​​the catalyst is 1000-1600 m². 2 ·g -1 The pore volume is 0.60-0.90 cm³. 3 ·g -1 The average pore size is 1–3 nm.

[0008] This invention also provides a method for preparing the above-mentioned modified carbon-based calcium-iron layered bimetallic hydroxide catalyst, the specific steps of which are as follows:

[0009] (1) Pretreatment of activated carbon fiber: The original activated carbon fiber was pretreated with acid solution. Before further treatment, the suspension was stirred evenly and fully contacted. After filtration, the activated carbon fiber sample was washed with deionized water until the pH of the filtrate was neutral. Then the sample was vacuum dried. The resulting sample was named ACF.

[0010] (2) Hydrothermal loading of CaFe-LDH on ACF: Calcium salt and iron salt are dissolved in deionized water and stirred to ensure complete dissolution and uniform mixing; then urea is added as the growth solution for layered bimetallic hydroxide to obtain a metal mixture. The pretreated ACF in step (1) is added to the above metal mixture and mixed evenly. The mixture is then transferred to a hydrothermal reactor for hydrothermal treatment. After the reaction is completed and the mixture is allowed to cool naturally, it is filtered and washed with deionized water until neutral (6.5-7.5) to obtain CaFeCO3-LDH / ACF.

[0011] (3) Ion exchange method to change interlayer anions: After cleaning, CaFe-CO3-LDH / ACF is transferred to a round bottom flask, a mixed solution containing hydrochloric acid and NaCl is added, and the reaction is carried out under oil bath reflux at a certain temperature with mechanical stirring to ensure that the reaction is complete; after the reaction is completed, the product is naturally cooled, and the product is taken out and washed with deionized water until neutral (6.5-7.5); vacuum drying is performed to obtain CaFeCl-LDH / ACF, abbreviated as CFLA.

[0012] Preferably, the acid solution in step (1) is hydrochloric acid, sulfuric acid, or nitric acid; the mass concentration of the acid solution is 5-10%; and the mass ratio of activated carbon fiber to the volume of the acid solution is 10-40 g·L. -1 .

[0013] The preferred stirring speed in step (1) is 200-400 rpm, and the stirring time is 2-4 h; the washing is carried out until the pH value of the filtrate is 6.5-7.5; the vacuum drying temperature is 60-100℃, and the vacuum drying time is 8-14 hours.

[0014] The preferred calcium salt in step (2) is CaCl2·2H2O, the iron salt is FeCl3·6H2O, and the molar ratio of calcium salt, iron salt, and urea is (2-5):1:(5-20). 2+ The concentration was 0.2–0.5 mol / L; the mass ratio of pretreated activated carbon fiber (ACF) to pure water was 5–20 g·L. -1 The stirring time is 0.5 to 1 hour.

[0015] The preferred mechanical stirring speed for dissolving calcium and iron salts in deionized water is 280–350 rpm, and the stirring time is 20–40 min; the mechanical stirring time for adding urea to the above mixed solution is 20–40 min; the hydrothermal reaction time is 10–14 h, and the hydrothermal reaction temperature is 150–180 °C.

[0016] The preferred step (3) has a molar ratio of hydrochloric acid, NaCl and iron salt of (1-3):(17-43):1; the oil bath time is 8-16 h and the temperature is 90-120 °C; the mechanical stirring speed is 100-180 rpm; the drying temperature is 60-100 °C and the vacuum drying time is 10-14 h.

[0017] This invention also provides the application of the above-mentioned modified carbon-based calcium-iron layered bimetallic hydroxide catalyst in the degradation of sulfamethoxazole (SMX) in wastewater. The specific steps are as follows: CFLA catalyst is added to simulated SMX wastewater, wherein the pH of the simulated wastewater is adjusted to 2.00–12.00 and the SMX concentration is 10–40 mg·L⁻¹. -1 The concentration of PMS in the wastewater after addition was 1.00–2.00 mM, and the mass ratio of CFLA catalyst to wastewater was 0.5–2 g·L⁻¹. -1 Place it in a constant temperature shaking bed, set the rotation speed to 150-250 rpm, and shake it at 20-55℃ for 1-3 hours.

[0018] Beneficial effects:

[0019] (1) The catalyst of the present invention is green and environmentally friendly, can be synthesized on a large scale, can be recycled and reused, and has high economic benefits.

[0020] (2) The catalyst of this invention uses activated carbon fiber (ACF) as a substrate and supports CaFe-LDH, which has a good activation effect on PMS under a wide range of pH conditions, through singlet oxygen ( 1 The non-radical oxidation pathway (O2) and electron transfer accelerates the reaction process and has a good selective oxidative degradation effect on SMX. Detailed Implementation

[0021] To better understand the present invention, the following embodiments are provided for further illustration. These embodiments are for explanation only and do not constitute any limitation on the present invention.

[0022] Example 1:

[0023] (1) Prepare simulated wastewater containing SMX, with an SMX concentration of 10 mg·L⁻¹. -1 The pH was adjusted to 2 using 0.1M NaOH and HCl.

[0024] (2) Preparation of the adsorbent, the steps are as follows:

[0025] (a) Pretreatment of ACF: Take 5.00 g of untreated activated carbon fiber, cut it into 1*1 cm cubes, and pretreat the activated carbon fiber with 500 ml of 5% HCl solution. Then, before further treatment, stir the suspension at 200 rpm for 4 hours at 298 K. After filtration, wash the ACF sample with distilled water until the pH of the filtrate is 6.5. Then, vacuum dry the sample at 60 °C for 14 h. The obtained sample is named ACF.

[0026] (b) Hydrothermal loading of CaFe-LDH onto ACF: 2.2196 g (0.02 mol) of CaCl2·6H2O and 2.703 g (0.01 mol) of FeCl3·6H2O (molar ratio 2:1) were weighed and dissolved in 100 ml of pure water. The mixture was stirred by gravity for 40 min at 280 rpm until completely dissolved and homogeneous. Then, 3.003 g (0.05 mol) of urea was weighed and added to the metal solution, and stirring was continued for 20 min until completely dissolved. Next, 0.5 g of the dried ACF from step (a) was added to the above solution and stirred at 280 rpm for 0.5 h until completely mixed. Finally, the mixture was transferred to the inner liner of a 250 ml hydrothermal reactor and subjected to hydrothermal treatment at 180 °C for 12 h. After the reaction was complete, the mixture was allowed to cool naturally, filtered, and washed with deionized water until the pH reached 7.0. The product was then transferred to a round-bottom flask, and 100 ml of HCl (0.1 M) and 10 g (0.17 mol) of NaCl were added. The mixture was reacted in an oil bath at 120 °C for 8 h with mechanical stirring at 180 rpm. After the reaction was complete, the mixture was allowed to cool naturally, and the product was removed and washed with deionized water until the pH reached 7.0. Finally, the washed product was vacuum dried at 60 °C for 14 h to obtain CFLA. The total specific surface area of ​​the composite adsorbent before and after modification was 1329.26 m². 2 ·g -1 The average pore size is 1.658 nm, and the average pore volume is 0.607 cm³. 3 ·g -1 The calcium loading in this composite adsorbent is 2.21%.

[0027] Weigh 0.05 g of the composite adsorbent CFLA prepared in this example, and measure 100 ml of the SMX-containing simulated wastewater prepared in step (1). Add CFLA to the simulated wastewater, and the PMS dosage is 1.0 mM. The reaction is carried out at 25°C with constant temperature shaking for 180 min at a shaking speed of 150 rpm. The SMX concentration is detected by high-performance liquid chromatography (HPLC). When the pH is 2, the SMX removal rate is 93.58%. The catalyst is recovered and reused. Under the same conditions, it is reused 5 times, and the removal rate is 91.21%.

[0028] Example 2

[0029] (1) Prepare simulated wastewater containing SMX, with an SMX concentration of 20 mg·L⁻¹. -1 The pH was adjusted to 6 using 0.1M NaOH and HCl.

[0030] (2) Preparation of the adsorbent, the steps are as follows:

[0031] (a) Pretreatment of ACF: Take 10.00 g of untreated activated carbon fiber, cut it into 1*1 cm cubes, and pretreat the activated carbon fiber with 500 ml of 10% H2SO4 solution. Then, before further treatment, stir the suspension at 298 K and 300 rpm for 3 hours. After filtration, wash the ACF sample with distilled water until the pH of the filtrate is 7. Then, vacuum dry the sample at 70 °C for 12 h. The obtained sample is named ACF.

[0032] (b) Hydrothermal loading of CaFe-LDH onto ACF: 3.3294 g (0.03 mol) of CaCl2·6H2O and 2.703 g (0.01 mol) of FeCl3·6H2O (molar ratio 3:1) were weighed and dissolved in 100 ml of pure water. The mixture was stirred by gravity for 30 min at 300 rpm until completely dissolved and homogeneous. Then, 6.006 g (0.1 mol) of urea was weighed and added to the metal solution, and stirring was continued for 20 min until completely dissolved. Next, 1.0 g of the dried ACF from step (a) was added to the above solution and stirred at 300 rpm for 1 h until completely mixed. Finally, the mixture was transferred to the inner liner of a 250 ml hydrothermal reactor and subjected to hydrothermal treatment at 170 °C for 11 h. After the reaction was complete, the mixture was allowed to cool naturally, filtered, and washed with deionized water until the pH reached 7.0. The product was then transferred to a round-bottom flask, and 100 mL of 0.2 M HCl and 15.0 g (0.26 mol) of NaCl were added. The mixture was reacted in an oil bath at 110 °C for 10 h with mechanical stirring at 160 rpm. After the reaction was complete, the mixture was allowed to cool naturally, and the product was removed and washed with deionized water until the pH reached 7.0. Finally, the washed product was vacuum dried at 70 °C for 12 h to obtain CFLA. The total specific surface area of ​​the composite adsorbent before and after modification was 1417.89 m². 2 ·g -1 The average pore size is 1.732 nm, and the average pore volume is 0.681 cm³. 3 ·g -1 The calcium loading in this composite adsorbent is 3.81%.

[0033] Weigh 0.1g of the composite adsorbent CFLA prepared in this example, measure 100ml of the SMX-containing simulated wastewater prepared in step (1), add CFLA to the simulated wastewater, and add 1.5mM PMS. The mixture is reacted at 35℃ with shaking for 120min at a shaking speed of 150rpm. The SMX concentration is detected by high-performance liquid chromatography (HPLC). At pH 6, the SMX removal rate is 98.91%. The catalyst is recovered and reused. Under the same conditions, it is reused 5 times, with a removal rate of 91.16%.

[0034] Example 3

[0035] (1) Prepare simulated wastewater containing SMX, with an SMX concentration of 30 mg·L⁻¹. -1 The pH was adjusted to 9 using 0.1M NaOH and HCl.

[0036] (2) Preparation of the adsorbent, the steps are as follows:

[0037] (a) Pretreatment of ACF: Take 15.00 g of untreated activated carbon fiber, cut it into 1*1 cm cubes, and pretreat the activated carbon fiber with 500 ml of 5% HNO3 solution. Then, before further treatment, stir the suspension at 298 K and 400 rpm for 4 hours. After filtration, wash the ACF sample with distilled water until the pH of the filtrate is 7.5. Then, vacuum dry the sample at 80 °C for 10 h. The obtained sample is named ACF.

[0038] (b) Hydrothermal loading of CaFe-LDH onto ACF: 4.7392 g (0.04 mol) of CaCl2·6H2O and 2.703 g (0.01 mol) of FeCl3·6H2O (molar ratio 4:1) were weighed and dissolved in 100 ml of pure water. The mixture was stirred by gravity for 20 min at 310 rpm until completely dissolved and homogeneous. Then, 9.009 g (0.15 mol) of urea was weighed and added to the metal solution, and stirring was continued for 30 min until completely dissolved. Next, 1.5 g of the dried ACF from step (a) was added to the above solution and stirred at 310 rpm for 1.5 h until completely mixed. Finally, the mixture was transferred to the inner liner of a 250 ml hydrothermal reactor and subjected to hydrothermal treatment at 160 °C for 12 h. After the reaction was complete, the mixture was allowed to cool naturally, filtered, and washed with deionized water until the pH reached 7.5. The product was then transferred to a round-bottom flask, and 100 mL of 0.3 M HCl and 20.0 g (0.34 mol) of NaCl were added. The mixture was reacted in an oil bath at 100 °C for 12 h with mechanical stirring at 140 rpm. After the reaction was complete, the mixture was allowed to cool naturally, and the product was removed and washed with deionized water until the pH reached 7.5. Finally, the washed product was vacuum dried at 80 °C for 11 h to obtain CFLA. The total specific surface area of ​​the composite adsorbent before and after modification was 1386.64 m². 2 ·g -1 The average pore size is 1.706 nm, and the average pore volume is 0.678 cm³. 3 ·g -1 The calcium loading in this composite adsorbent is 4.69%.

[0039] Weigh 0.15 g of the composite adsorbent CFLA prepared in this example, measure 100 ml of the SMX-containing simulated wastewater prepared in step (1), add CFLA to the simulated wastewater, and add 1.5 mM PMS. The mixture is reacted at 45°C with constant temperature shaking for 120 min at a shaking speed of 150 rpm. The SMX concentration is detected by high performance liquid chromatography. When the pH is 9, the SMX removal rate is 98.36%. The catalyst is recovered and reused. Under the same conditions, it is reused 5 times, and the removal rate is 90.66%.

[0040] Example 4

[0041] (1) Prepare simulated wastewater containing SMX, with an SMX concentration of 40 mg·L⁻¹. -1 The pH was adjusted to 12 using 0.1M NaOH and HCl.

[0042] (2) Preparation of the adsorbent, the steps are as follows:

[0043] (a) Pretreatment of ACF: Take 20.00 g of untreated activated carbon fiber, cut it into 1*1 cm cubes, and pretreat the activated carbon fiber with 500 ml of 10% HCl solution. Then, before further treatment, stir the suspension at 300 rpm for 2 hours at 298 K. After filtration, wash the ACF sample with distilled water until the pH of the filtrate is 6.5. Then, vacuum dry the sample at 100 °C for 8 hours. The obtained sample is named ACF.

[0044] (b) Hydrothermal loading of CaFe-LDH onto ACF: 5.549 g (0.05 mol) of CaCl2·6H2O and 2.703 g (0.01 mol) of FeCl3·6H2O (molar ratio 5:1) were weighed and dissolved in 100 ml of pure water. The mixture was stirred by gravity for 20 min at 350 rpm until completely dissolved and homogeneous. Then, 12.012 g (0.2 mol) of urea was weighed and added to the metal solution, and stirring was continued for 40 min until completely dissolved. Next, 2.0 g of the dried ACF from step (a) was added to the above solution and stirred at 350 rpm for 2 h until completely mixed. Finally, the mixture was transferred to the inner liner of a 250 ml hydrothermal reactor and subjected to hydrothermal treatment at 150 °C for 14 h. After the reaction was complete, the mixture was allowed to cool naturally, filtered, and washed with deionized water until the pH reached 7.0. The product was then transferred to a round-bottom flask, and 100 mL of HCl (0.3 M) and 25.0 g (0.43 mol) of NaCl were added. The mixture was reacted in an oil bath at 90 °C for 16 h with mechanical stirring at 100 rpm. After the reaction was complete, the mixture was allowed to cool naturally, and the product was removed and washed with deionized water until the pH reached 7.0. Finally, the washed product was vacuum dried at 90 °C for 10 h to obtain CFLA. The total specific surface area of ​​the composite adsorbent before and after modification was 1389.26 m². 2 ·g -1 The average pore size is 1.719 nm, and the average pore volume is 0.669 cm³. 3 ·g -1 The calcium loading in this composite adsorbent is 5.16%.

[0045] Weigh 0.2 g of the composite adsorbent CFLA prepared in this example, measure 100 ml of the SMX-containing simulated wastewater prepared in step (1), add CFLA to the simulated wastewater, and add 2.0 mM PMS. The mixture is reacted at 55°C with constant temperature shaking for 60 min at a shaking speed of 150 rpm. The SMX concentration is detected by high performance liquid chromatography. When the pH is 12, the SMX removal rate is 99.28%. The catalyst is recovered and reused. Under the same conditions, it is reused 5 times, and the removal rate is 91.35%.

Claims

1. A method for preparing a modified carbon-based calcium-iron layered bimetallic hydroxide catalyst, characterized in that, The specific steps are as follows: (1) Pretreatment of activated carbon fiber: The original activated carbon fiber was pretreated with acid solution, and the suspension was stirred evenly before further treatment; after filtration, the activated carbon fiber sample was washed with deionized water until the pH of the filtrate was neutral, and then the sample was vacuum dried; the resulting sample was named ACF. (2) Hydrothermal loading of CaFe-LDH on ACF: Calcium salt and iron salt are dissolved in deionized water and stirred to ensure complete dissolution and uniform mixing; then urea is added to obtain a metal mixture. The pretreated ACF in step (1) is added to the above metal mixture and mixed evenly. The mixture is then transferred to a hydrothermal reactor for hydrothermal treatment. After the reaction is completed and the mixture is allowed to cool naturally, it is filtered and washed with deionized water until neutral to obtain CaFeCO3-LDH / ACF. (3) Ion exchange method to change interlayer anions: After cleaning, CaFeCO3-LDH / ACF is transferred to a round bottom flask, a mixed solution containing hydrochloric acid and NaCl is added, and the reaction is carried out under oil bath reflux at a certain temperature and mechanical stirring is performed to ensure that the reaction is complete. After the reaction was complete, the product was allowed to cool naturally, then removed and washed with deionized water until neutral. It was then dried under vacuum to obtain CaFeCl-LDH / ACF, abbreviated as CFLA.

2. The method according to claim 1, characterized in that, The acid solution mentioned in step (1) is hydrochloric acid, sulfuric acid, or nitric acid; the mass concentration of the acid solution is 5-10%; and the mass ratio of activated carbon fiber to the volume of the acid solution is 10-40 g·L. -1 .

3. The method according to claim 1, characterized in that, The stirring speed mentioned in step (1) is 200~400 rpm. The stirring time is 2-4 hours; the filtrate is washed until the pH value is 6.5-7.5; the vacuum drying temperature is 60-100℃ and the vacuum drying time is 8-14 hours.

4. The method according to claim 1, characterized in that, The calcium salt mentioned in step (2) is CaCl2·2H2O, the iron salt is FeCl3·6H2O, and the molar ratio of calcium salt, iron salt and urea is (2~5):1:(5~20). 2+ The concentration was 0.2~0.5 mol / L; the mass ratio of pretreated activated carbon fiber (ACF) to pure water was 5~20 g·L. -1 The stirring time is 0.5 to 1 hour.

5. The method according to claim 1, characterized in that, The mechanical stirring speed for dissolving calcium and iron salts in deionized water is 280-350 rpm, and the stirring time is 20-40 min; the mechanical stirring time for adding urea to the above mixed solution is 20-40 min; the hydrothermal reaction time is 10-14 h, and the hydrothermal reaction temperature is 150-180℃.

6. The method according to claim 1, characterized in that, The molar ratio of hydrochloric acid and NaCl in step (3) to iron salt in step (2) is (1~3):(17~43):1; the oil bath time is 8~16h and the temperature is 90~120℃; the mechanical stirring speed is 100~180rpm; the drying temperature is 60~100℃ and the vacuum drying time is 10~14h.

7. A modified carbon-based calcium-iron layered bimetallic hydroxide catalyst prepared by the preparation method according to any one of claims 1-6.

8. The modified carbon-based calcium-iron layered bimetallic hydroxide catalyst according to claim 7, characterized in that, The catalyst consists of a support and a layered bimetallic hydroxide. The support is activated carbon fiber (ACF), and the layered bimetallic hydroxide is a calcium-iron layered bimetallic hydroxide. The mass percentage of Ca loaded is 2.26–5.16%. 2+ and Fe 3+ The molar ratio is (2~5):1; the total specific surface area of ​​the catalyst is 1000~1600 m². 2 ·g -1 ; The pore volume is 0.60-0.90 cm³. 3 ·g -1 The average pore size is 1~3nm.

9. The application of the modified carbon-based calcium-iron layered bimetallic hydroxide catalyst as described in claim 8 in the degradation of sulfamethoxazole (SMX) in wastewater.

10. The application according to claim 9, characterized in that, The specific steps are as follows: CFLA catalyst is added to the simulated SMX wastewater, wherein the pH of the simulated wastewater is adjusted to 2.00~12.00 and the SMX concentration is 10~40 mg·L. -1 The concentration of PMS in the wastewater after addition was 1.00~2.00 mM, and the mass ratio of CFLA catalyst to wastewater was 0.5~2 g·L⁻¹. -1 Place it in a constant temperature shaking bed, set the rotation speed to 150-250 rpm, and shake it at 20-55℃ for 1-3 hours.