A metal-free activated carbon fiber-based catalyst, a preparation method and application thereof

Abstract

The application provides a metal-free activated carbon fiber-based catalyst and a preparation method and application thereof, which is used for activating peroxymonosulfate (PMS) to efficiently degrade sulfamethoxazole (SMX) in water. The technology combines the functions of adsorption and catalysis, and optimizes the disadvantages of low efficiency and high cost of traditional water treatment methods. By loading polydopamine on the surface of activated carbon fiber and performing carbonization treatment, the structural stability of the material is improved, and by the inherent nitrogen doping characteristics, the catalytic effect is optimized, and efficient degradation of SMX is realized. Experiments show that the SMX removal efficiency of the material can reach more than 90%, and the material can be recycled for multiple times through simple regeneration, effectively reducing the cost and resource consumption, without external metal catalyst, reducing the risk of secondary pollution. The application provides an environmentally friendly, economical and efficient solution, which has an important promoting effect on the development of the field of SMX-containing wastewater treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental engineering water treatment, and relates to a non-metal activated carbon fiber-based catalyst and a preparation method and application thereof, in particular to a novel catalytic material technology for efficiently removing sulfamethoxazole (SMX) in wastewater. The carbonized polydopamine modified activated carbon fiber (PDAC / ACF) is used to realize the activation of persulfate (PMS) and the efficient degradation of pollutants. BACKGROUND

[0002] Sulfamethoxazole (SMX) is a widely used antibiotic that has attracted the attention of environmental scientists due to its high stability and biological activity in natural water bodies. Studies have shown that the presence of SMX in the environment can lead to an increase in bacterial resistance. For example, one study found that the concentration of SMX detected at the outlet of a municipal wastewater treatment plant was often as high as several hundred nanograms per liter, a level that was sufficient to affect the microbial community structure in aquatic ecosystems. In addition, the potential risks of SMX to human health cannot be ignored, as long-term exposure to trace amounts of SMX can lead to allergic reactions and even more serious health problems. Although various technologies have been developed to remove SMX from water, including biodegradation, adsorption, and advanced oxidation processes, these methods often have the disadvantages of low efficiency, high cost, or complex operation. For example, traditional activated carbon adsorption can remove SMX from water, but it has a fast saturation rate and is difficult to regenerate, resulting in low economic benefits. In addition, advanced oxidation processes can effectively degrade SMX, but they are expensive to operate and may produce toxic byproducts. In view of the shortcomings of existing technologies, the present application proposes a novel carbonized polydopamine modified activated carbon fiber (ACF) that combines the functions of adsorption and catalytic activation of persulfate (PMS), aiming to achieve efficient removal of SMX through an economical and efficient method. The introduction of carbonized polydopamine (PDA) not only enhances the structural stability of ACF, but also enhances the catalytic activity through its inherent nitrogen doping properties, allowing it to effectively activate PMS at room temperature and promote the rapid degradation of SMX. Experiments have shown that the removal efficiency of SMX by this material can be more than 90%, which is much higher than that of traditional ACF. Another significant advantage of the present application is environmental friendliness and sustainability. Since PDAC / ACF can activate PMS without the addition of external metal catalysts, it does not introduce heavy metal ions that can cause secondary pollution.

[0003] For the technical research of PMS activated by polydopamine material to degrade sulfamethoxazole (SMX), some researchers first prepared carbonized polydopamine (PDAC), and then modified it with β-cyclodextrin to obtain a β-CD@PDAC catalyst. The host-guest specific adsorption of β-cyclodextrin can assist the nitrogen-doped carbon-based catalyst to selectively oxidize the target pollutant and improve the removal effect of SMX. Jiang Y et al. used Fe(NO3)3·9H2O, hydrochloric acid dopamine and melamine as precursors to prepare a nitrogen-doped carbon material. Under the optimal experimental conditions, SMX has a very good degradation effect. More than 99.00% of SMX is degraded within 30 min. Cao X et al. used expired drugs as an endogenous nitrogen source and DCDA as an exogenous nitrogen source to prepare a carbon-based PMS activator with high nitrogen doping level. It can achieve efficient degradation of SMX in a very short time, and achieve super-fast degradation of SMX within 2 min. SUMMARY

[0004] The purpose of the present application is to improve the shortcomings of the prior art and provide a metal-free activated carbon fiber-based catalyst. Another purpose of the present application is to provide a preparation method of the above-mentioned catalyst. The present application also has the purpose of providing the application of the above-mentioned catalyst in the degradation of SMX in wastewater. The catalyst is a carbonized polydopamine modified activated carbon fiber catalyst (PDAC / ACF). By using a metal-free catalyst, the synergistic effect between ACF and polydopamine is utilized to significantly improve the degradation efficiency of SMX.

[0005] The technical solution of the present application is a metal-free activated carbon fiber-based catalyst, characterized in that the metal-free activated carbon fiber-based catalyst is a carbonized polydopamine modified activated carbon fiber catalyst, wherein the mass ratio of carbonized polydopamine PDAC to activated carbon fiber ACF is 1:(10-20).

[0006] The present application also provides a method for preparing the above-mentioned metal-free activated carbon fiber-based catalyst, and the specific steps are as follows:

[0007] (1) Pretreatment of activated carbon fiber: first, add an acid solution to the (original) activated carbon fiber, then stir the suspension uniformly, and perform acid treatment by sufficient contact; then filter, wash the activated carbon fiber sample with distilled water repeatedly until the pH value of the filtrate is neutral (6.5-7.5); then vacuum dry the sample; the obtained sample is named as ACF;

[0008] (2) loading polydopamine: prepare a solution containing ethanol and deionized water in a container, add ammonia water and the ACF pretreated in step (1) to the above mixed solution, and stir at room temperature for a certain time; then add dopamine precursor under magnetic stirring, keep the magnetic stirring for a period of time to make dopamine self-polymerize; then slowly drop acetone while rapidly stirring, and stand after the addition is completed; collect the precipitate after standing, and dry under vacuum, and obtain the ACF loaded with polydopamine (PDA / ACF) by freeze-drying after the acetone volatilizes;

[0009] (3) forming a polymer coating on the ACF: the ACF loaded with dopamine is treated at high temperature under an inert atmosphere to carbonize the dopamine, and the obtained sample is repeatedly washed and vacuum dried after the reaction to obtain a metal-free activated carbon fiber-based catalyst PDAC / ACF.

[0010] Preferably, the acid solution in step (1) is at least one of hydrochloric acid or sulfuric acid; the mass concentration of the acid solution is 5-10%; the mass of the activated carbon fiber to the volume of the acid solution is 20-40 g·L -1 . The stirring speed is 200-400 rpm, and the stirring time is 2-4 h; the pH value of the filtrate after washing is 6.5-7.5; the vacuum drying temperature is 60-90℃, and the vacuum drying time is 12-14 hours.

[0011] Preferably, the volume fraction of ethanol in step (2) is 20-30%; the volume ratio of the added ammonia water to the ethanol aqueous solution is (3-6):100; the mass of the added ACF to the volume of the ethanol solution is 10-30 g·L -1 ; the room temperature stirring time is 30-60 min, and the stirring speed is 250-300 rpm; the dopamine precursor is dopamine hydrochloride; the mass ratio of dopamine hydrochloride to ACF is 1:(1-3), and the stirring time is 18-30 h; the volume ratio of the added acetone to the ethanol aqueous solution is 1.5-2.5:1; the standing time is 18-30 h; the vacuum drying temperature is 50-60℃, and the time is 20-40 min; the freeze-drying time is 10-14 h, and the temperature is -50 to -60℃.

[0012] Preferably, the high-temperature treatment in step (3) is at a temperature of 750-850℃ for 1-3 h; the vacuum drying temperature is 50-60℃, and the time is 12-14 h.

[0013] Preferably, the deionized water in steps (1) and (3) is washed until the pH value of the filtrate is 6.5-7.5.

[0014] The application also provides application of the metal-free activated carbon fiber-based catalyst in degradation of sulfamethoxazole (SMX) in wastewater. The specific steps are as follows: the metal-free activated carbon fiber-based catalyst and PMS are added into simulated SMX wastewater, and the mixture is placed in a constant-temperature shaking bed for shaking reaction; the pH of the simulated wastewater is adjusted to 2.00-12.00, the SMX concentration is 10-40 mg / L -1 , the PMS concentration is 1.00-2.00 mM, the mass of the adsorbent added into the wastewater solution is 0.5-2 g / L -1 , the rotation speed of the shaking bed is set to 150-170 rpm, and the shaking reaction is carried out at 25-55 DEG C for 1-3 h.

[0015] Beneficial effects:

[0016] (1) Synergistic effect of adsorption and PMS activation: by modifying the carbonized polydopamine coating on the activated carbon fiber, the application not only provides excellent adsorption performance, but also significantly enhances the activation ability of PMS. This synergistic effect significantly improves the degradation efficiency of SMX, especially in complex water environments.

[0017] (2) Metal-free catalyst, avoiding secondary pollution: using metal-free carbonized polydopamine as an activator avoids the environmental pollution problems that may be caused by traditional metal catalysts. In addition, the catalyst can be recycled multiple times through a simple regeneration process after the reaction, further reducing the treatment cost and resource consumption.

[0018] (3) Improving the degradation efficiency of SMX: by utilizing the synergistic effect between the carrier ACF and polydopamine, the application overcomes the problem of limited PMS activation ability and low catalytic efficiency of single activated carbon fiber-based materials, and realizes efficient degradation of SMX.

[0019] (4) Selective oxidation of non-radical pathway: the catalytic system can selectively oxidize and degrade SMX through a non-radical mechanism in complex water environments, which provides the possibility for targeted treatment of specific pollutants and helps to improve the accuracy and efficiency of treatment.

[0020] (5) Promoting the development of practical applications: the application provides a new way for activated carbon fiber-based materials to activate PMS for selective degradation of typical antibiotics in wastewater in practical applications. This unique technology not only has innovation in academia, but also shows great potential and wide applicability in industrial applications due to its economy. DETAILED DESCRIPTION

[0021] In order to better understand the application, the application is further illustrated by the following examples, which are only used for explanation and do not constitute any limitation on the application.

[0022] Example 1:

[0023] (1) The SMX-containing simulated wastewater was prepared, and the SMX concentration was 10 mg / L -1 The pH was adjusted to 2 using 0.1 M NaOH and HCl.

[0024] (2) The catalyst was prepared, and the steps were as follows:

[0025] (a) Acid treatment of ACF: 10 g of untreated activated carbon fiber was cut into small cubes of 1*1 cm, and the activated carbon fiber was pretreated with 500 ml of 5% mass concentration HCl solution, and then the suspension was stirred at 200 rpm at room temperature for 4 hours before further treatment. After filtration, the activated carbon fiber sample was washed with deionized water until the pH of the filtrate was 6.5. Then the sample was dried at 60°C under vacuum for 14 h, and the obtained sample was named ACF.

[0026] (b) Preparation of PDA / ACF: a. 100 ml of 20% volume fraction ethanol aqueous solution was prepared and transferred into a container; b. 3.0 ml of ammonia water was added dropwise to the above ethanol aqueous solution, and 1.0 g of ACF in step (1) was added, followed by magnetic stirring at room temperature for 30 min at a stirring speed of 300 rpm; c. 1.0 g of dopamine hydrochloride was added under stirring conditions, and the stirring was continued for 18 h; d. Under stirring conditions, 150 ml of acetone was slowly added dropwise into the container, and after the addition was completed, it was left to stand and settle for 18 h; e. The supernatant was removed by suction filtration, and the precipitate was collected and vacuum dried for 40 min at a temperature of 50°C; f. After vacuum drying, it was transferred into a freeze dryer for 10 h at a temperature of -60°C, and a sample PDA / ACF was obtained.

[0027] (c). Formation of polymer coating on ACF: PDA / ACF was calcined at 750°C in a tube furnace under N2 atmosphere for 3 h; after cooling to room temperature, the sample was washed several times with deionized water until the pH of the filtrate was 6.5, and was transferred to a vacuum dryer for 14 h at a temperature of 50°C. The obtained sample was recorded as PDAC / ACF. The mass ratio of carbonized polydopamine (PDAC) to activated carbon fiber (ACF) was 1:10.

[0028] (3) 0.05 g of the catalyst PDAC / ACF prepared in this example was weighed, and 100 ml of the SMX-containing simulated wastewater prepared in step (1) was measured, and the PDAC / ACF was added into the simulated wastewater, and the PMS dosage was 1.0 mM, and the constant temperature shaking reaction was carried out at 25°C for 180 min at a shaking speed of 150 rpm. High performance liquid chromatography was used to detect the SMX concentration, and when the pH was 2, the SMX removal rate was 91.19%. The catalyst was recovered and reused, and under the same conditions, it was reused for 5 times, and the removal rate was 88.69%.

[0029] Example 2:

[0030] (1) The SMX-containing simulated wastewater was prepared, with the SMX concentration being 20 mg / L -1 , and the pH was adjusted to 7 using 0.1 M NaOH and HCl.

[0031] (2) The catalyst was prepared, with the following steps:

[0032] (a) Acid treatment of ACF: 15 g of untreated activated carbon fiber was cut into small cubes of 1*1 cm, and the activated carbon fiber was pretreated with 500 ml of 10% mass concentration HCl solution, and then the suspension was stirred at room temperature at 300 rpm for 3 hours before further treatment. After filtration, the activated carbon fiber sample was washed with deionized water until the pH of the filtrate was 7.0. Then the sample was vacuum dried at 80°C for 13 h, and the resulting sample was named ACF.

[0033] (b) Preparation of PDA / ACF: a. 100 ml of 30% volume fraction ethanol aqueous solution was prepared and transferred into a container; b. 5.0 ml of ammonia water was added dropwise to the above ethanol aqueous solution, and 2.0 g of ACF in step (1) was added, followed by magnetic stirring at room temperature at 275 rpm for 45 min; c. 1.0 g of dopamine hydrochloride was added under stirring conditions, and the stirring was continued for 24 h; d. under stirring conditions, 200 ml of acetone was slowly added dropwise into the container, and after the addition was completed, it was left to stand and settle for 24 h; e. the supernatant was removed by suction filtration to collect the precipitate, which was vacuum dried for 30 min at 55°C; f. after vacuum drying, it was transferred into a freeze dryer for 12 h at -55°C to obtain the sample PDA / ACF.

[0034] (c). Formation of polymer coating on ACF: PDA / ACF was calcined at 800°C for 2 h in a tube furnace under N2 atmosphere; after cooling to room temperature, the sample was washed several times with deionized water until the filtrate pH was 7, and was transferred to a vacuum dryer for 12 h at 55°C. The resulting sample was denoted as PDAC / ACF. The mass ratio of carbonized polydopamine (PDAC) to activated carbon fiber (ACF) was 1:15.

[0035] (3) 0.1 g of the catalyst PDAC / ACF prepared in this example was weighed, and 100 ml of the SMX-containing simulated wastewater prepared in step (1) was measured, and the PDAC / ACF was added into the simulated wastewater, with the PMS dosage being 1.0 mM, and the reaction was carried out at 35°C for 120 min with constant temperature shaking at a shaking speed of 160 rpm. High performance liquid chromatography was used to detect the SMX concentration, and the SMX removal rate was 95.47% when the pH was 7. The catalyst was recovered and reused, and under the same conditions, it was reused for 5 times, with the removal rate being 91.42%.

[0036] Example 3:

[0037] (1) The SMX-containing simulated wastewater was prepared, with the SMX concentration being 40 mg·L -1 , and the pH was adjusted to 12 using 0.1 M NaOH and HCl.

[0038] (2) The catalyst was prepared, with the following steps:

[0039] (a) Acid treatment of ACF: 20 g of untreated activated carbon fiber was cut into small cubes of 1*1 cm, and the activated carbon fiber was pretreated with 500 ml of a 5% mass concentration H2SO4 solution, and then the suspension was stirred at a speed of 400 rpm at room temperature for 2 hours before further treatment. After filtration, the activated carbon fiber sample was washed with deionized water until the pH of the filtrate was 7.5. Then the sample was vacuum dried at 90°C for 12 h, and the resulting sample was named ACF.

[0040] (b) Preparation of PDA / ACF: a. 100 ml of an ethanol aqueous solution with a volume fraction of 20% was prepared and transferred into a container; b. 6.0 ml of ammonia water was added dropwise to the above ethanol aqueous solution, and 3.0 g of ACF in step (1) was added, followed by magnetic stirring at room temperature for 60 min at a speed of 250 rpm; c. 1.0 g of dopamine hydrochloride was added under stirring conditions, and stirring was continued for 30 h; d. Under stirring conditions, 250 ml of acetone was slowly added dropwise into the container, and after the addition was completed, it was left to settle for 30 h; e. The supernatant was removed by suction filtration, and the precipitate was vacuum dried for 20 min at a temperature of 60°C; f. After vacuum drying, it was transferred into a freeze dryer for 14 h at a temperature of -50°C, and a sample of PDA / ACF was obtained.

[0041] (c). Formation of a polymer coating on ACF: PDA / ACF was calcined at a high temperature of 850°C in a tube furnace under N2 atmosphere for 1 h; after cooling to room temperature, the sample was washed several times with deionized water until the pH of the filtrate was 7.5, and was transferred to a vacuum dryer for 12 h at a temperature of 60°C. The resulting sample was recorded as PDAC / ACF. The mass ratio of carbonized polydopamine (PDAC) to activated carbon fiber (ACF) was 1:20.

[0042] (3) 0.2 g of the catalyst PDAC / ACF prepared in this example was weighed, 100 ml of the SMX-containing simulated wastewater prepared in step (1) was measured, the PDAC / ACF was put into the simulated wastewater, the PMS dosage was 2.0 mM, and the reaction was carried out at 45°C for 60 min under constant temperature oscillation at a shaking speed of 170 rpm. The SMX concentration was detected by high performance liquid chromatography, and when the pH was 12, the SMX removal rate was 93.22%. The catalyst was recovered and reused, and under the same conditions, it was reused for 5 times, and the removal rate was 89.46%.

Claims

1. A metal-free activated carbon fiber-based catalyst, characterized by The metal-free activated carbon fiber-based catalyst is a carbonized polydopamine modified activated carbon fiber catalyst, wherein the mass ratio of carbonized polydopamine PDAC to activated carbon fiber ACF is 1:(10-20), and is prepared by the following method, and the specific steps are as follows: (1) Pretreatment of activated carbon fiber: first, add an acid solution to the activated carbon fiber, then stir the suspension uniformly, and perform acid treatment by sufficient contact; then filter, wash the activated carbon fiber sample repeatedly with distilled water until the pH value of the filtrate is neutral; then vacuum dry the sample; the obtained sample is named ACF; (2) Load polydopamine: prepare a solution containing ethanol and deionized water in a container, add ammonia water and the pretreated ACF in step (1) to the above mixed solution, and stir for a certain time; then add dopamine precursor under magnetic stirring condition, and keep the magnetic stirring condition for a period of time to make dopamine self-polymerize; Then drop acetone, and after the addition is completed, stand still; After standing still, collect the precipitate, and dry it under vacuum condition, and then freeze-dry to obtain the ACF loaded with polydopamine after the acetone volatilizes; (3) Form a polymer coating on the ACF: treat the ACF loaded with dopamine at high temperature under an inert atmosphere to carbonize the dopamine, and after the reaction is completed, repeatedly wash and vacuum dry the obtained sample to obtain the metal-free activated carbon fiber-based catalyst PDAC / ACF.

2. The metal-free activated carbon fiber-based catalyst according to claim 1, characterized by The acid solution in step (1) is at least one of hydrochloric acid or sulfuric acid; the mass concentration of the acid solution is 5-10%; the mass of the activated carbon fiber to the volume of the acid solution is 20-40 g·L -1 ; the stirring speed is 200-400 rpm, the stirring time is 2-4 h; the pH value of the filtrate after washing is 6.5-7.5; the vacuum drying temperature is 60-90℃, and the vacuum drying time is 12-14 hours.

3. The metal-free activated carbon fiber-based catalyst according to claim 1, characterized by The volume fraction of ethanol in step (2) is 20-30%; the volume ratio of the ammonia water and the ethanol aqueous solution is (3-6):100; the mass ratio of the added ACF and the ethanol solution is 10-30 g·L -1 ; the stirring time is 30-60 min, the rotating speed is 250-300 rpm; the dopamine precursor is dopamine hydrochloride; the mass ratio of dopamine hydrochloride and ACF is 1:(1-3), the stirring time is 18-30 h; the volume ratio of the added acetone and the ethanol aqueous solution is 1.5-2.5:1; the standing and settling time is 18-30 h; the vacuum drying temperature is 50-60℃, the time is 20-40 min; the freeze-drying time is 10-14 h, the temperature is-50--60℃.

4. The metal-free activated carbon fiber-based catalyst according to claim 1, characterized by The temperature of the high-temperature treatment in step (3) is 750-850 DEG C, and the holding time is 1-3 h; the vacuum drying temperature is 50-60 DEG C, and the time is 12-14 h.

5. The metal-free activated carbon fiber-based catalyst according to claim 1, wherein The deionized water in steps (1) and (3) is washed until the pH value of the filtrate is 6.5-7.

5.

6. Use of the metal-free activated carbon fiber-based catalyst in claim 1 in degradation of sulfamethoxazole SMX in wastewater.

7. Use according to claim 6, characterized in that The specific steps are: adding non-metal activated carbon fiber-based catalyst and PMS into simulated SMX wastewater, and placing in a constant temperature shaking bed for shaking reaction; wherein the pH of the simulated wastewater is adjusted to 2.00-12.00, the SMX concentration is 10-40 mg·L -1 , the PMS addition concentration is 1.00-2.00 mM, the adsorbent addition mass and wastewater solution are 0.5-2 g·L -1 ; the rotation speed in the shaking bed is set to 150-170 rpm, and the shaking reaction is carried out at 25-55℃ for 1-3h.