Modified activated carbon for promoting degradation of dioxin and preparation method and application thereof

Abstract

This invention discloses a method for preparing modified activated carbon that promotes dioxin degradation, relating to the field of environmental pollutant treatment technology. The method of this invention, through precise control of preparation parameters, effectively preserves the micropores and total specific surface area of ​​the activated carbon, ensuring sufficient adsorption sites for dioxins. It achieves a synergistic effect between the pore structure and FeOx active sites, enabling efficient adsorption of dioxins during waste incineration flue gas purification, ensuring efficient adsorption and removal of gaseous dioxins in the flue. Furthermore, the modified activated carbon adsorbing highly toxic dioxins can degrade the adsorbed dioxins in situ in a liquid system via the Fenton method, and its adsorption performance can be restored through heat treatment, achieving a closed-loop utilization of "adsorption-degradation-regeneration." This effectively reduces the production and disposal costs of hazardous waste, improves dioxin degradation efficiency, and has significant environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of environmental pollutant treatment technology, specifically to a modified activated carbon that promotes dioxin degradation, its preparation method, and its application. Background Technology

[0002] Waste incineration is an important method for treating municipal solid waste, offering advantages such as volume reduction, harmlessness, and resource recovery. However, the incineration process easily generates persistent organic pollutants—dioxins (PCDD / Fs). Dioxins are highly toxic, persistent, and bioaccumulative, and their emissions not only harm the ecological environment but also pose a serious threat to human health. To control dioxin emissions, flue gas purification systems typically employ activated carbon injection for adsorption. Activated carbon has a large specific surface area and abundant pore structure, effectively capturing organic pollutants such as dioxins. However, traditional activated carbon relies solely on physical adsorption, its function limited to transferring gaseous dioxins to the solid phase, ultimately forming "toxic activated carbon." This not only fails to achieve complete elimination of dioxins but also introduces secondary pollution and a burden on subsequent treatment.

[0003] While existing research has explored methods such as metal loading and surface functionalization to modify activated carbon and improve its dioxin removal efficiency, these methods largely focus on the adsorption stage and fail to substantially address the issues of dioxin's stable molecular structure and recalcitrant degradation. Currently, there is no effective technology for advanced oxidation treatment of activated carbon adsorbed with highly toxic dioxins using a liquid-phase system, thereby achieving dioxin degradation and activated carbon regeneration. Traditional activated carbon typically requires incineration or landfill disposal after use, increasing costs, wasting resources, and posing potential environmental risks.

[0004] Therefore, it is necessary to develop a modified activated carbon that can efficiently adsorb dioxins during the purification of flue gas from waste incineration and promote the subsequent degradation of dioxins, thereby achieving the detoxification and recycling of activated carbon. This would overcome the limitations of traditional adsorption technology's "adsorption-pollution transfer" and truly solve the current problem of gas-solid phase dioxin control in waste incineration. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a modified activated carbon for promoting dioxin degradation, its preparation method, and its application.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A method for preparing modified activated carbon that promotes dioxin degradation is provided, comprising the following specific steps:

[0008] S1: Pretreated activated carbon is obtained by immersing activated carbon powder in an ethanol aqueous solution, ultrasonic treatment, and then filtering off the surface free liquid.

[0009] The air bubbles in the activated carbon pores are first removed by using an ethanol-water solution and ultrasound, making it easier for the subsequent ferric nitrate solution to enter the mesoporous region of the activated carbon.

[0010] S2: Dissolve Fe(NO3)3·9H2O in an aqueous ethanol solution to obtain Fe(NO3)3 solution, then immerse the pretreated activated carbon in the Fe(NO3)3 solution and stir for 12~24h.

[0011] S3: After soaking, perform vacuum filtration, place the solid in urea aqueous solution, adjust the pH of the reaction system to 7~7.5 with HNO3 solution, and continue stirring for 2~4 hours.

[0012] When ferric nitrate is co-precipitated using urea solution, urea slowly releases OH- ions, allowing Fe... 3+ It can grow in a controlled manner, avoiding clogging of the pores and reducing the adsorption capacity of activated carbon.

[0013] S4: After the reaction is complete, the reaction system is subjected to ultrasonic vibration to remove the Fe(OH)x adhering to the outer surface or macropores of the activated carbon.

[0014] S5: After oscillation, solid-liquid separation is performed. The separated solid is then heat-treated to obtain modified activated carbon.

[0015] The specific method of heat treatment is as follows:

[0016] S51: Calcine the solid at 250~300℃ for 1~2 hours;

[0017] S52: Then, under a nitrogen atmosphere containing 5% H2, perform thermal reduction at 300~350℃ for 0.5~1h;

[0018] S53: After naturally cooling to 120℃, slowly passivate by introducing air for 0.5~1h.

[0019] Furthermore, the ethanol-water solution is prepared by mixing ethanol and water at a volume ratio of 3:1.

[0020] Furthermore, the concentration of Fe(NO3)3 in the Fe(NO3)3 solution is 3~5mM; the ratio of Fe(NO3)3 solution to activated carbon is 10~20mL / g.

[0021] Using a ferric nitrate solution with ethanol and water as solutes not only allows the ferric nitrate solution to enter the mesoporous region of activated carbon uniformly and rapidly, but also ensures that nitrate ions do not affect the subsequent adsorption and degradation of dioxins.

[0022] Furthermore, in step S2, during soaking, magnetic stirring is performed at 20~30℃ and the stirring speed is 100~200 rpm.

[0023] Furthermore, during the stirring and soaking process, ultrasonic vibration is performed for 1 to 2 minutes every 0.5 to 1 hour, with an ultrasonic frequency of 20 kHz and a power of 100 to 200 W.

[0024] Furthermore, the ultrasonic treatment in step S1 specifically involves: 500W~1000W power at 20kHz for 1~3 minutes.

[0025] Furthermore, in step S4, the ultrasonic oscillation frequency is selected as 20kHz, the power as 50~100W, and the ultrasonic oscillation time as 2~5min.

[0026] This invention also provides an application of the modified activated carbon described above, which promotes dioxin degradation, in the adsorption and degradation of dioxins during waste incineration. The modified activated carbon is ground and sieved to obtain iron-based activated carbon powder with a particle size of 10-30 μm. This iron-based activated carbon powder is then sprayed into the flue gas duct between a high-temperature metal bag filter and a low-temperature bag filter in a waste incineration flue gas purification system. The high-temperature metal bag filter is located in the flue gas section of the waste incineration flue gas purification system where the temperature is above 500°C, and the low-temperature bag filter is located in the flue gas section where the temperature is 140-160°C. The dosage of the iron-based activated carbon powder is 20-50 mg / Nm³. 3 .

[0027] After the flue gas from waste incineration is filtered by a high-temperature metal bag filter, a large amount of particulate matter is intercepted. Activated carbon is then injected into the subsequent flue section and captured by a low-temperature bag filter. Therefore, the collected solid particulate matter is mainly iron-based modified activated carbon enriched with highly toxic dioxins, so that the bag filter fly ash is mainly composed of highly toxic activated carbon, which facilitates subsequent targeted detoxification and activated carbon recycling.

[0028] Furthermore, the activated carbon powder containing dioxins is recycled. The specific recycling method is as follows:

[0029] A1: Mix the toxic activated carbon powder with water at a ratio of 10-20 g / L, and adjust the pH to 3.5-4.5 using a 1 mol / L hydrochloric acid solution.

[0030] A2: Add hydrogen peroxide to the mixture and stir to react. After adding hydrogen peroxide, the concentration of H2O2 in the reaction system is 50~100mM. Stir at 200~400rpm for 4~6h, and apply an ultrasonic pulse with a frequency of 20 kHz and a power of 500W for 1min every 19min during the stirring reaction.

[0031] Ultrasonic waves highly disperse the aggregated activated carbon. The combined effect of magnetic stirring and ultrasound enhances the homogeneity and mass transfer efficiency of the solution, facilitating the entry of H2O2 into the activated carbon pores to fully contact the active FeOx. Under the action of divalent Fe ions, hydroxyl radicals are generated, which rapidly degrade the dioxins adsorbed in the mesopores through advanced oxidation reactions. Furthermore, under the effect of ultrasonic cavitation, not only are additional hydroxyl radicals generated, but they are also further promoted to enter the micropores from the mesopores, where they undergo in-situ advanced oxidation degradation reactions with the dioxins adsorbed in the micropores. The dioxin degradation rate reaches over 90%.

[0032] A3: After the reaction, solid-liquid separation is performed to obtain detoxifying activated carbon. The detoxifying activated carbon is dried at 105℃ for 12h, and then thermally reduced at 300~350℃ for 0.5~1h under a nitrogen atmosphere containing 5% H2. The powder is ball-milled and sieved to obtain detoxifying activated carbon powder of 10~30μm. The detoxifying activated carbon powder is mixed with iron-based activated carbon powder at a mass ratio of 1:4 and then recycled.

[0033] The beneficial effects of this invention are as follows:

[0034] This invention, through precise control of preparation parameters, effectively preserves the microporous structure and total specific surface area of ​​activated carbon, providing sufficient sites for efficient dioxin adsorption. The modified activated carbon prepared achieves a microporous specific surface area retention rate of over 85% and a total specific surface area retention rate of over 80%. The synergistic effect of micropores and mesopores allows gaseous dioxin molecules to first enter and be enriched in mesopores, and then be firmly captured by micropores. Simultaneously, the highly dispersed FeOx active sites on the mesopore walls further enhance the enrichment and immobilization effect of dioxins, thereby achieving efficient removal of gaseous dioxins from flues, reducing the frequency of activated carbon replenishment, and lowering operating costs.

[0035] More importantly, this invention achieves a closed-loop utilization of adsorption-degradation-regeneration for the first time: modified activated carbon adsorbed with highly toxic dioxins can efficiently degrade the adsorbed dioxins in situ in a liquid system via the Fenton method, ensuring the complete decomposition of toxic components; subsequently, heat treatment restores the pore structure and adsorption capacity of the activated carbon, realizing the recycling and regeneration of the material. Unlike traditional unmodified activated carbon, which can only achieve the physical transfer of dioxins, this process not only breaks through the limitation of traditional activated carbon "only adsorbing but not degrading," but also achieves the complete degradation of adsorbed dioxins and the recycling of activated carbon, significantly reducing the generation of hazardous waste, lowering the cost of solid waste disposal, and truly achieving the efficient removal of dioxins, with outstanding environmental and economic benefits. Detailed Implementation

[0036] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0037] Anhydrous ethanol: AR (Shanghai Test), ≥99.7%, Sinopharm Chemical Reagent Co., Ltd.; Activated carbon: Coal-based activated carbon, BET specific surface area ≥800m². 2 / g, 200 mesh, Fe(NO3)3・9H2O: AR (Shanghai Test), ≥98.5%, Sinopharm Chemical Reagent Co., Ltd., Urea: AR (Shanghai Test), ≥99%, Sinopharm Chemical Reagent Co., Ltd., Nitric Acid: GR (Shanghai Test), 65.0~68.0%, Sinopharm Chemical Reagent Co., Ltd.

[0038] Example 1

[0039] A method for preparing modified activated carbon that promotes dioxin degradation includes the following specific steps:

[0040] S1: Immerse activated carbon powder in an ethanol aqueous solution and sonicate at 20 kHz with an ultrasonic power of 500 W for 3 min. Then filter off the surface free liquid to obtain pretreated activated carbon. The ethanol aqueous solution is prepared by mixing ethanol and water at a volume ratio of 3:1.

[0041] The air bubbles in the activated carbon pores are first removed by using an ethanol-water solution and ultrasound, making it easier for the subsequent ferric nitrate solution to enter the mesoporous region of the activated carbon.

[0042] S2: Fe(NO3)3·9H2O was dissolved in an ethanol-water solution with a volume ratio of 3:1 to obtain a Fe(NO3)3 solution. Pretreated activated carbon was then immersed in the Fe(NO3)3 solution and stirred for 12 hours. During immersion, magnetic stirring was performed at 30°C and a stirring speed of 200 rpm. Furthermore, ultrasonic vibration was performed for 2 minutes every 0.5 hours, with an ultrasonic frequency of 20 kHz and a power of 100 W.

[0043] The concentration of Fe(NO3)3 in the Fe(NO3)3 solution is 3 mM; the ratio of Fe(NO3)3 solution to activated carbon is 20 mL / g.

[0044] S3: After soaking, vacuum filter the solid and place it in urea solution. Adjust the pH of the reaction system to 7 with HNO3 solution and continue stirring for 2 hours.

[0045] Co-precipitation of ferric nitrate using urea aqueous solution allows urea to slowly release OH- ions, thus allowing Fe...3+ It can grow in a controlled manner, avoiding clogging of the pores and reducing the adsorption capacity of activated carbon.

[0046] S4: After the reaction is completed, the reaction system is subjected to ultrasonic oscillation to remove Fe(OH)x adhering to the outer surface or macropores of the activated carbon; the ultrasonic oscillation frequency is selected as 20kHz, the power is 50W, and the ultrasonic oscillation time is 5min.

[0047] S5: After oscillation, solid-liquid separation is performed. The separated solid is then heat-treated to obtain modified activated carbon. The specific heat treatment method is as follows:

[0048] S51: Calcine the solid at 250℃ for 2 hours;

[0049] S52: Then, under a nitrogen atmosphere containing 5% H2, perform thermal reduction at 300℃ for 1 hour;

[0050] S53: After naturally cooling to 120℃, slowly passivate by introducing air for 0.5h.

[0051] The prepared modified activated carbon was ground and sieved to obtain modified activated carbon powder with a particle size of 10~30μm. The BET / N2 adsorption experiment of the modified activated carbon powder was carried out by a physical gas adsorption performance tester (model: ASAP2460). The original activated carbon powder was used as a comparison. The experimental results showed that the micropore specific surface area retention rate was above 85% and the total specific surface area retention rate was above 80% compared with the original activated carbon.

[0052] The modified activated carbon powder was also subjected to leaching tests. Specifically, it was leached with a nitric acid solution with a pH between 3.5 and 4.5 at a liquid-to-solid ratio of 10:1 (mL / g). The concentration of Fe in the leaching solution was detected using a plasma atomic emission spectrometer (model: PerkinElmer Optima 8300), and the leaching concentration of Fe was found to be below 50 mg / L.

[0053] Example 2

[0054] A method for preparing modified activated carbon that promotes dioxin degradation includes the following specific steps:

[0055] S1: Immerse activated carbon powder in an ethanol aqueous solution and sonicate at 20 kHz with an ultrasonic power of 7500 W for 2 min. Then filter off the surface free liquid to obtain pretreated activated carbon. The ethanol aqueous solution is prepared by mixing ethanol and water at a volume ratio of 3:1.

[0056] The air bubbles in the activated carbon pores are first removed by using an ethanol-water solution and ultrasound, making it easier for the subsequent ferric nitrate solution to enter the mesoporous region of the activated carbon.

[0057] S2: Fe(NO3)3·9H2O was dissolved in an ethanol-water solution with a volume ratio of 3:1 to obtain a Fe(NO3)3 solution. Pretreated activated carbon was then immersed in the Fe(NO3)3 solution and stirred for 18 hours. During immersion, magnetic stirring was performed at 25°C and a stirring speed of 150 rpm. Furthermore, ultrasonic vibration was performed for 1.5 minutes every 0.75 hours, with an ultrasonic frequency of 20 kHz and a power of 15 W.

[0058] The concentration of Fe(NO3)3 in the Fe(NO3)3 solution is 4 mM; the ratio of Fe(NO3)3 solution to activated carbon is 15 mL / g.

[0059] S3: After soaking, vacuum filter the solid and place it in a urea solution. Adjust the pH of the reaction system to 7.2 with HNO3 solution and continue stirring for 3 hours.

[0060] When ferric nitrate is co-precipitated using urea solution, urea slowly releases OH- ions, allowing Fe... 3+ It can grow in a controlled manner, avoiding clogging of the pores and reducing the adsorption capacity of activated carbon.

[0061] S4: After the reaction is completed, the reaction system is subjected to ultrasonic vibration to remove the Fe(OH)x adhering to the outer surface or macropores of the activated carbon; the ultrasonic vibration frequency is selected as 20kHz, the power is 75W, and the ultrasonic vibration time is 3.5min.

[0062] S5: After oscillation, solid-liquid separation is performed. The separated solid is then heat-treated to obtain modified activated carbon. The specific heat treatment method is as follows:

[0063] S51: Calcine the solid at 275℃ for 1.5h;

[0064] S52: Then, under a nitrogen atmosphere containing 5% H2, perform thermal reduction at 325℃ for 0.75h;

[0065] S53: After naturally cooling to 120℃, slowly passivate by introducing air for 0.75h.

[0066] The prepared modified activated carbon was ground and sieved to obtain modified activated carbon powder with a particle size of 10~30μm. The BET / N2 adsorption experiment of the modified activated carbon powder was carried out by a physical gas adsorption performance tester (model: ASAP2460). The original activated carbon powder was used as a comparison. The experimental results showed that the micropore specific surface area retention rate was above 85% and the total specific surface area retention rate was above 80% compared with the original activated carbon.

[0067] The modified activated carbon powder was also subjected to leaching tests. Specifically, it was leached with a nitric acid solution with a pH between 3.5 and 4.5 at a liquid-to-solid ratio of 10:1 (mL / g). The concentration of Fe in the leaching solution was detected using a plasma atomic emission spectrometer (model: PerkinElmer Optima 8300), and the leaching concentration of Fe was found to be below 50 mg / L.

[0068] Example 3

[0069] A method for preparing modified activated carbon that promotes dioxin degradation includes the following specific steps:

[0070] S1: Immerse activated carbon powder in an ethanol aqueous solution and sonicate at 20 kHz with an ultrasonic power of 1000 W for 1 min. Then filter off the surface free liquid to obtain pretreated activated carbon. The ethanol aqueous solution is prepared by mixing ethanol and water at a volume ratio of 3:1.

[0071] The air bubbles in the activated carbon pores are first removed by using an ethanol-water solution and ultrasound, making it easier for the subsequent ferric nitrate solution to enter the mesoporous region of the activated carbon.

[0072] S2: Fe(NO3)3·9H2O was dissolved in an ethanol-water solution with a volume ratio of 3:1 to obtain a Fe(NO3)3 solution. Pretreated activated carbon was then immersed in the Fe(NO3)3 solution and stirred for 24 hours. During immersion, magnetic stirring was performed at 20°C and a stirring speed of 100 rpm. Additionally, ultrasonic vibration was performed for 1 minute every hour, with an ultrasonic frequency of 20 kHz and a power of 100 W.

[0073] The concentration of Fe(NO3)3 in the Fe(NO3)3 solution is 5 mM; the ratio of Fe(NO3)3 solution to activated carbon is 10 mL / g.

[0074] S3: After soaking, vacuum filter the solid and place it in urea solution. Adjust the pH of the reaction system to 7.5 with HNO3 solution and continue stirring for 4 hours.

[0075] When ferric nitrate is co-precipitated using urea solution, urea slowly releases OH- ions, allowing Fe... 3+ It can grow in a controlled manner, avoiding clogging of the pores and reducing the adsorption capacity of activated carbon.

[0076] S4: After the reaction is completed, the reaction system is subjected to ultrasonic oscillation to remove the Fe(OH)x adhering to the outer surface or macropores of the activated carbon; the ultrasonic oscillation frequency is selected as 20kHz, the power is 100W, and the ultrasonic oscillation time is 2min.

[0077] S5: After oscillation, solid-liquid separation is performed. The separated solid is then heat-treated to obtain modified activated carbon. The specific heat treatment method is as follows:

[0078] S51: Calcine the solid at 300℃ for 1 hour;

[0079] S52: Then, under a nitrogen atmosphere containing 5% H2, perform thermal reduction at 350℃ for 0.5h;

[0080] S53: After naturally cooling to 120℃, slowly passivate by introducing air for 1 hour.

[0081] The prepared modified activated carbon was ground and sieved to obtain modified activated carbon powder with a particle size of 10~30μm. The BET / N2 adsorption experiment of the modified activated carbon powder was carried out by a physical gas adsorption performance tester (model: ASAP2460). The original activated carbon powder was used as a comparison. The experimental results showed that the micropore specific surface area retention rate was above 85% and the total specific surface area retention rate was above 80% compared with the original activated carbon.

[0082] The modified activated carbon powder was also subjected to leaching tests. Specifically, it was leached with a nitric acid solution with a pH between 3.5 and 4.5 at a liquid-to-solid ratio of 10:1 (mL / g). The concentration of Fe in the leaching solution was detected using a plasma atomic emission spectrometer (model: PerkinElmer Optima 8300), and the leaching concentration of Fe was found to be below 50 mg / L.

[0083] Example 4

[0084] The modified activated carbon prepared in Example 1 was ground and sieved to obtain iron-based activated carbon powder with a particle size of 10-30 μm. The iron-based activated carbon powder was then sprayed into the flue gas duct between a high-temperature metal bag filter and a low-temperature bag filter in a waste incineration flue gas purification system. The high-temperature metal bag filter was installed in the flue gas section of the waste incineration flue gas purification system where the temperature was above 500°C, and the low-temperature bag filter was installed in the flue gas section where the temperature was 140-160°C. The dosage of the iron-based activated carbon powder was 20-50 mg / Nm³. 3 Toxic activated carbon powder is collected and obtained using a low-temperature bag filter.

[0085] The activated carbon powder containing dioxins is recycled. The specific recycling method is as follows:

[0086] A1: Mix the toxic activated carbon powder with water at a ratio of 10 g / L, and adjust the pH to 3.5 using a 1 mol / L hydrochloric acid solution;

[0087] A2: Add hydrogen peroxide to the mixture and stir to react. After adding hydrogen peroxide, the concentration of H2O2 in the reaction system is 50mM. Stir at 400rpm for 6h, and apply an ultrasonic pulse with a frequency of 20kHz and a power of 500W for 1min every 19min during the stirring reaction.

[0088] The toxic activated carbon powder and the detoxifying activated carbon powder were pretreated according to the US EPA 1613B standard method, and the dioxin concentration was detected by high resolution gas chromatography-mass spectrometry (GC-MS) (HRGC / MS, model: JMS800D). The calculation results showed that the dioxin degradation efficiency reached more than 90%.

[0089] A3: After the reaction, solid-liquid separation was performed to obtain detoxifying activated carbon. The detoxifying activated carbon was dried at 105℃ for 12h, and then thermally reduced at 300℃ for 1h under a nitrogen atmosphere containing 5% H2. The detoxifying activated carbon powder with a particle size of 10~30μm was obtained by ball milling and sieving. The detoxifying activated carbon powder was mixed with iron-based activated carbon powder at a mass ratio of 1:4 and then recycled.

[0090] Example 5

[0091] The modified activated carbon prepared in Example 1 was ground and sieved to obtain iron-based activated carbon powder with a particle size of 10-30 μm. The iron-based activated carbon powder was then sprayed into the flue gas duct between a high-temperature metal bag filter and a low-temperature bag filter in a waste incineration flue gas purification system. The high-temperature metal bag filter was installed in the flue gas section of the waste incineration flue gas purification system where the temperature was above 500°C, and the low-temperature bag filter was installed in the flue gas section where the temperature was 140-160°C. The dosage of the iron-based activated carbon powder was 20-50 mg / Nm³. 3 Toxic activated carbon powder is collected and obtained using a low-temperature bag filter.

[0092] The activated carbon powder containing dioxins is recycled. The specific recycling method is as follows:

[0093] A1: Mix the toxic activated carbon powder with water at a ratio of 15 g / L, and adjust the pH to 4 using a 1 mol / L hydrochloric acid solution.

[0094] A2: Add hydrogen peroxide to the mixture and stir to react. After adding hydrogen peroxide, the concentration of H2O2 in the reaction system is 75mM. Stir at 300rpm for 5h, and apply an ultrasonic pulse with a frequency of 20kHz and a power of 500W for 1min every 19min during the stirring reaction.

[0095] The toxic activated carbon powder and the detoxifying activated carbon powder were pretreated according to the US EPA 1613B standard method, and the dioxin concentration was detected by high resolution gas chromatography-mass spectrometry (GC-MS) (HRGC / MS, model: JMS800D). The calculation results showed that the dioxin degradation efficiency reached more than 90%.

[0096] A3: After the reaction, solid-liquid separation was performed to obtain detoxifying activated carbon. The detoxifying activated carbon was dried at 105℃ for 12h, and then thermally reduced at 325℃ for 0.75h under a nitrogen atmosphere containing 5% H2. The detoxifying activated carbon powder with a particle size of 10~30μm was obtained by ball milling and sieving. The detoxifying activated carbon powder was mixed with iron-based activated carbon powder at a mass ratio of 1:4 and then recycled.

[0097] Example 6

[0098] The modified activated carbon prepared in Example 1 was ground and sieved to obtain iron-based activated carbon powder with a particle size of 10-30 μm. The iron-based activated carbon powder was then sprayed into the flue gas duct between a high-temperature metal bag filter and a low-temperature bag filter in a waste incineration flue gas purification system. The high-temperature metal bag filter was installed in the flue gas section of the waste incineration flue gas purification system where the temperature was above 500°C, and the low-temperature bag filter was installed in the flue gas section where the temperature was 140-160°C. The dosage of the iron-based activated carbon powder was 20-50 mg / Nm³. 3 Toxic activated carbon powder is collected and obtained using a low-temperature bag filter.

[0099] The activated carbon powder containing dioxins is recycled. The specific recycling method is as follows:

[0100] A1: Mix the toxic activated carbon powder with water at a ratio of 20 g / L, and adjust the pH to 4.5 using a 1 mol / L hydrochloric acid solution.

[0101] A2: Add hydrogen peroxide to the mixture and stir to react. After adding hydrogen peroxide, the concentration of H2O2 in the reaction system is 100mM. Stir at 200rpm for 4h, and apply an ultrasonic pulse with a frequency of 20kHz and a power of 500W for 1min every 19min during the stirring reaction.

[0102] The toxic activated carbon powder and the detoxifying activated carbon powder were pretreated according to the US EPA 1613B standard method, and the dioxin concentration was detected by high resolution gas chromatography-mass spectrometry (GC-MS) (HRGC / MS, model: JMS800D). The calculation results showed that the dioxin degradation efficiency reached more than 90%.

[0103] A3: After the reaction, solid-liquid separation was performed to obtain detoxifying activated carbon. The detoxifying activated carbon was dried at 105℃ for 12h, and then thermally reduced at 350℃ for 0.5h under a nitrogen atmosphere containing 5% H2. The detoxifying activated carbon powder with a particle size of 10~30μm was obtained by ball milling and sieving. The detoxifying activated carbon powder was mixed with iron-based activated carbon powder at a mass ratio of 1:4 and then recycled.

Claims

1. A method for producing a modified activated carbon for promoting degradation of dioxins, characterized by, The specific steps include the following: S1: Pretreated activated carbon is obtained by immersing activated carbon powder in an ethanol aqueous solution, ultrasonic treatment, and then filtering off the surface free liquid. S2: Dissolve Fe(NO3)3·9H2O in an aqueous ethanol solution to obtain Fe(NO3)3 solution, immerse pretreated activated carbon in Fe(NO3)3 solution and stir for 12~24h; S3: After soaking, perform vacuum filtration, place the solid in urea aqueous solution, adjust the pH of the reaction system to 7~7.5 with HNO3 solution, and continue stirring for 2~4 hours. S4: After the reaction is complete, the reaction system is subjected to ultrasonic vibration to remove the Fe(OH)x adhering to the outer surface or macropores of the activated carbon. S5: After oscillation, solid-liquid separation is performed. The separated solid is then heat-treated to obtain modified activated carbon. The specific method of heat treatment is as follows: S51: Calcine the solid at 250~300℃ for 1~2 hours; S52: Then, under a nitrogen atmosphere containing 5% H2, perform thermal reduction at 300~350℃ for 0.5~1h; S53: After naturally cooling to 120℃, slowly passivate by introducing air for 0.5~1h; The ethanol-water solution was prepared by mixing ethanol and water at a volume ratio of 3:

1. The concentration of Fe(NO3)3 in the Fe(NO3)3 solution is 3~5mM; the ratio of Fe(NO3)3 solution to activated carbon is 10~20mL / g. In step S2, during soaking, magnetic stirring is performed at 20~30℃ and the stirring speed is 100~200rpm.

2. The production method according to claim 1, characterized by, During the stirring and soaking process, ultrasonic vibration is performed for 1 to 2 minutes every 0.5 to 1 hour, with an ultrasonic frequency of 20 kHz and a power of 100 to 200 W.

3. The preparation method according to claim 2, characterized in that, The ultrasonic treatment in step S1 is specifically as follows: at 20kHz, with a power of 500W~1000W, ultrasonic treatment for 1~3 minutes.

4. The preparation method according to claim 3, characterized in that, In step S4, the ultrasonic oscillation frequency is selected as 20kHz, the power is 50~100W, and the ultrasonic oscillation time is 2~5min.

5. Modified activated carbon for promoting dioxin degradation prepared by any of the preparation methods described in claims 1 to 4.

6. The use of the modified activated carbon for promoting dioxin degradation according to claim 5 for adsorbing and degrading dioxin in waste incineration, characterized in that, Modified activated carbon was ground and sieved to obtain iron-based activated carbon powder with a particle size of 10-30 μm. This powder was then sprayed into the flue gas duct between a high-temperature metal bag filter and a low-temperature bag filter in a waste incineration flue gas purification system. The high-temperature metal bag filter was installed in the flue gas section of the system where the temperature was above 500°C, while the low-temperature bag filter was installed in the section where the temperature was between 140-160°C. The dosage of the iron-based activated carbon powder was 20-50 mg / Nm³. 3 ; The activated carbon powder containing dioxins is also recycled. The specific recycling method is as follows: A1: Mix the toxic activated carbon powder with water at a ratio of 10-20 g / L, and adjust the pH to 3.5-4.5 using a 1 mol / L hydrochloric acid solution. A2: Add hydrogen peroxide to the mixture and stir to react. After adding hydrogen peroxide, the concentration of H2O2 in the reaction system is 50~100mM. Stir at 200~400rpm for 4~6h, and apply an ultrasonic pulse with a frequency of 20 kHz and a power of 500W for 1min every 19min during the stirring reaction. A3: After the reaction, solid-liquid separation is performed to obtain detoxifying activated carbon. The detoxifying activated carbon is dried at 105℃ for 12h, and then thermally reduced at 300~350℃ for 0.5~1h under a nitrogen atmosphere containing 5% H2. The powder is ball-milled and sieved to obtain detoxifying activated carbon powder of 10~30μm. The detoxifying activated carbon powder is mixed with iron-based activated carbon powder at a mass ratio of 1:4 and then recycled.