Method for preparing quinone-mediator-modified biochar material and granulation reaction device

Abstract

A method for preparing a quinone-mediator-modified biochar material, aiming to solve the problems that azo dye wastewater is difficult to treat and granular sludge processes have a long granulation time. The preparation method comprises: 1. pyrolyzing residual sludge in a nitrogen atmosphere to obtain sludge biochar; 2. using deionized water to wash the sludge biochar a plurality of times; 3. dissolving sodium anthraquinone-2-sulfonate in dichloromethane and adding thionyl chloride for an acyl chlorination reaction; 4. soaking the washed sludge biochar in deionized water, adjusting the pH value of the system, and then adding diacetyltriamine to obtain aminated sludge biochar; and 5. the aminated sludge biochar reacting with anthraquinone-2-sulfonyl chloride to obtain the quinone-mediator-modified biochar material. In the method, sludge in a secondary sedimentation tank of a sewage plant is used as substrate biochar, and an anthraquinone compound is loaded on the surface of the sludge as an inner core of granular sludge. The condition for microbial aggregation on a carrier is improved, and the formation time of the granular sludge is shortened.

Description

Preparation method of quinone mediator modified biochar material and granulation reaction device Technical Field

[0001] The present invention belongs to the field of sewage biological treatment, and in particular relates to a method for preparing a modified biochar particle core material and an anaerobic granular sludge treatment device. Background Art

[0002] In the dye production and textile dyeing industries, large amounts of dyes are discharged as wastewater, resulting in dye wastewater characterized by high chroma, high strength, high biotoxicity, and resistance to biodegradation. Azo dye wastewater is considered a difficult-to-treat, toxic, and high-concentration industrial wastewater. Of all dyes, azo dyes are currently the most widely used in industry, accounting for over half of all dyes used. Therefore, improving the efficiency of azo wastewater treatment is key to effectively treating printing and dyeing wastewater.

[0003] Biological methods are currently the most widely used methods for treating printing and dyeing wastewater, with a combination of anaerobic hydrolysis and aerobic treatment being the most effective. Due to the low redox potential, complex structure, and steric hindrance of dye molecules, the reduction bond cleavage reaction becomes the rate-limiting step in the mineralization process of azo dyes. The primary limiting factor is the low electron transfer rate, which in turn increases the residence time required to treat the pollutants, increases the reactor volume, and increases manufacturing costs. This also limits the application of anaerobic technology in the treatment of azo printing and dyeing wastewater.

[0004] Certain soluble compounds containing quinone groups can effectively accelerate the biotransformation of azo dyes, increasing the rate by several orders of magnitude and possessing broad application value. However, due to their strong water solubility, quinone mediators are easily removed with the water when added directly to the reaction system, resulting in secondary pollution and high costs.

[0005] Because of the advantages of anaerobic granular sludge such as higher biological concentration, stronger impact resistance, and excellent sedimentation performance, its use in the treatment of printing and dyeing wastewater can improve its treatment capacity. However, the granular sludge process has the main disadvantage of long granulation time. How to quickly achieve sludge granulation is still a bottleneck problem in the research and application of granular sludge technology.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to solve the problems of difficult treatment of azo dye wastewater and long granulation time in granular sludge process, and to provide a preparation method of quinone mediator modified biochar material and a granulation reaction device.

[0008] The preparation method of the quinone mediator modified biochar material of the present invention is achieved by the following steps:

[0009] First, the excess sludge from the secondary sedimentation tank of the sewage treatment plant is placed in a tubular furnace and pyrolyzed under a nitrogen atmosphere to obtain sludge biochar;

[0010] 2. Washing the sludge biochar with deionized water for multiple times, drying it, grinding it, and sieving it to obtain washed sludge biochar;

[0011] 3. Dissolve sodium anthraquinone-2-sulfonate in dichloromethane, add thionyl chloride and carry out chlorination reaction at 55-65°C, and evaporate the solvent to obtain anthraquinone-2-sulfonyl chloride;

[0012] 4. Immerse the washed sludge biochar in deionized water, add ammonia water to adjust the pH of the system to 10, heat to 90-98°C, add diacetyltriamine, and continue stirring the mixed reaction solution for 8-10 hours. After the reaction is completed, filter and dry to obtain ammoniated sludge biochar;

[0013] 5. The amination-modified sludge biochar was placed in a mixed solution of anhydrous ethanol and dichloromethane, anthraquinone-2-sulfonyl chloride was added, and the reaction was carried out at a temperature of 35-40°C for 2-4 hours. After the reaction was completed, the biochar was dried to obtain a quinone mediator-modified biochar material.

[0014] The modified biochar of the present invention typically has a high surface area and porosity, providing a site for microbial growth and attachment. Microorganisms can settle on the surface of the biochar, forming a biofilm and promoting the granulation of sludge particles through adhesion.

[0015] The present invention uses excess sludge from sewage treatment plants as raw material to prepare biochar. The density is reduced by pyrolysis at different temperatures, and the particle size is reduced so that it can be suspended in water bodies. It is suitable as a base material for granular sludge. The present invention subjects the sludge biochar to an amination treatment, and then loads the quinone compound anthraquinone-2-sodium sulfonate (AQS) onto the surface of the biochar to prepare a quinone mediator material, forming the core of the granular sludge. Because AQS undergoes an acyl chloride reaction, acyl chlorides and amino compounds can undergo an amidation reaction to generate amide compounds. After the biochar is aminated, the AQS and the biochar are connected by a covalent bond, resulting in a more stable AQS functionalized biochar material.

[0016] The reaction device for granulating floc sludge of the present invention includes a reactor chamber, a three-phase separator and a circulating water pump. The bottom of the reactor chamber is in an inverted cone shape, the middle of the reactor chamber is cylindrical, the top of the reactor chamber is provided with a three-phase separator, the bottom of the reactor chamber is provided with a water inlet, the middle of the reactor chamber is a sludge area, the sludge area is filled with a mixture of quinone mediator modified biochar material and anaerobic sludge, the upper part of the sludge area is provided with a reflux port, one end of the reflux pipe is connected to the reflux port, the other end of the reflux pipe is connected to the water inlet, a circulating water pump is provided on the reflux pipe, the top of the three-phase separator is provided with an air outlet, and the side wall of the three-phase separator is provided with a water inlet.

[0017] The main body of the flocculent sludge granulation reaction device of the present invention is an upflow anaerobic bioreactor, which is provided with a water inlet and a water distribution plate at the bottom, a sludge area in the middle, a three-phase separator and an internal reflux port at the top, and an air outlet and an overflow weir at the top.

[0018] The present invention uses modified biochar particles as the core material. The rich void structure on the surface of biochar can provide a larger habitat space for microorganisms. The quinone mediators loaded on the surface of biochar can increase the electron transfer rate between microbial species and enhance the mutual synergy between microorganisms, thereby improving the resistance to the external environment and realizing efficient and stable operation of the anaerobic reactor.

[0019] The present invention provides a novel method for preparing the core of granular sludge, using the sludge from the secondary sedimentation tank of a sewage treatment plant as the base biochar, and loading anthraquinone compounds onto its surface as the core of the granular sludge, thereby improving the aggregation carrier conditions of microorganisms, shortening the formation time of granular sludge, and improving the anaerobic reduction capacity of granular sludge, thereby improving the anaerobic biological treatment efficiency of azo dye wastewater. Preparing the residual sludge from the secondary sedimentation tank of a sewage treatment plant into biochar is an integrated way of waste treatment and resource utilization, and is also an effective way to achieve carbon emission reduction. The present invention loads anthraquinone compounds onto biochar through amination pretreatment, and uses quinone mediator materials as cores to be placed in a bioreactor to shorten the formation time of granular sludge, which can enhance the anaerobic biological treatment of azo dyes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a schematic structural diagram of a reaction device for granulating flocculent sludge according to the present invention;

[0021] FIG2 is a scanning electron microscope image of the granular sludge formed in the application example. DETAILED DESCRIPTION

[0022] Specific embodiment 1: The preparation method of the quinone mediator modified biochar material of this embodiment is implemented according to the following steps:

[0023] First, the excess sludge from the secondary sedimentation tank of the sewage treatment plant is placed in a tubular furnace and pyrolyzed under a nitrogen atmosphere to obtain sludge biochar;

[0024] 2. Washing the sludge biochar with deionized water for multiple times, drying it, grinding it, and sieving it to obtain washed sludge biochar;

[0025] 3. Dissolve sodium anthraquinone-2-sulfonate in dichloromethane, add thionyl chloride and carry out chlorination reaction at 55-65°C, and evaporate the solvent to obtain anthraquinone-2-sulfonyl chloride;

[0026] 4. Immerse the washed sludge biochar in deionized water, add ammonia water to adjust the pH of the system to 10, heat to 90-98°C, add diacetyltriamine, and continue stirring the mixed reaction solution for 8-10 hours. After the reaction is completed, filter and dry to obtain ammoniated sludge biochar;

[0027] 5. The amination-modified sludge biochar was placed in a mixed solution of anhydrous ethanol and dichloromethane, anthraquinone-2-sulfonyl chloride was added, and the reaction was carried out at a temperature of 35-40°C for 2-4 hours. After the reaction was completed, the biochar was dried to obtain a quinone mediator-modified biochar material.

[0028] In step 1 of this embodiment, the sludge is first naturally concentrated for 2 hours.

[0029] This method uses quinone-loaded biochar particles as the core to accelerate the granulation of anaerobic sludge, forming granular sludge with high anaerobic reduction capacity. This provides a new approach for the resource utilization of excess sludge and can be applied to the anaerobic treatment of printing and dyeing wastewater, improving the anaerobic biological treatment of azo dyes.

[0030] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the excess sludge described in step 1 is the settled sludge in the secondary sedimentation tank.

[0031] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that during the pyrolysis treatment process described in step one, the nitrogen flow rate is controlled to 1 L / min, the heating rate is 5°C / min, and the high-temperature pyrolysis is carried out at 800°C for 2h.

[0032] This embodiment controls the temperature of the pyrolysis treatment to reduce the density of the sludge biochar and reduce the particle size so that the biochar can be suspended in the water.

[0033] Specific embodiment 4: The difference between this embodiment and any one of specific embodiments 1 to 3 is that in step 2, the mixture is sieved through an 80-100 mesh screen after grinding.

[0034] Specific embodiment 5: The difference between this embodiment and any one of specific embodiments 1 to 4 is that in step 5, the mass ratio of the amination sludge biochar to anthraquinone-2-sulfonyl chloride is 1:(3-6).

[0035] Specific embodiment 6: This embodiment differs from any one of specific embodiments 1 to 5 in that the reaction is carried out at a temperature of 35-40° C. for 2 h in step 5.

[0036] Specific embodiment seven: The reaction device for granulation of floc sludge in this embodiment includes a reactor chamber 1, a three-phase separator 2 and a circulating water pump 3. The bottom of the reactor chamber 1 is in an inverted cone shape, the middle part of the reactor chamber 1 is cylindrical, and the three-phase separator 2 is arranged on the top of the reactor chamber 1. A water inlet 1-1 is opened at the bottom of the reactor chamber 1. The middle part of the reactor chamber 1 is a sludge area, and the sludge area is filled with a mixture of quinone mediator modified biochar material and anaerobic sludge. A reflux port is opened at the top of the sludge area, one end of the reflux pipe 4 is connected to the reflux port, and the other end of the reflux pipe 4 is connected to the water inlet. A circulating water pump 3 is arranged on the reflux pipe 4, an air outlet 2-1 is opened on the top of the three-phase separator 2, and a water inlet 2-2 is opened on the side wall of the three-phase separator 2.

[0037] In the cultivation stage of this embodiment, the flocculent sludge discharged every day is passed through a 1000-mesh sieve, and the solids on the sieve are returned to the reactor; after 30-40 days of operation, the average particle size of the sludge is 200-800 μm, and the sludge in the reactor is granulated. The formation of granular sludge can improve the ability of the reaction system to operate stably.

[0038] Specific embodiment eight: This embodiment differs from specific embodiment seven in that a water distribution plate is provided at the lower part of the sludge area.

[0039] Specific embodiment 9: This embodiment is different from specific embodiment 7 or 8 in that a plurality of sampling ports 5 are opened in the middle of the reactor chamber 1 along the height direction.

[0040] Specific embodiment ten: This embodiment differs from any one of specific embodiments seven to nine in that the concentration of anaerobic sludge in the sludge zone is 3000-3500 mg / L.

[0041] Specific embodiment eleven: The difference between this embodiment and specific embodiments seven to ten is that the concentration of quinone mediator-modified biochar particles in the sludge zone is 2.5-3.5 g / gMLSS.

[0042] Example 1: The preparation method of the quinone mediator-modified biochar material of this embodiment is carried out according to the following steps:

[0043] First, the sludge after gravity concentration was separated and dried in an oven at 60°C. It was then placed in a tube furnace and pyrolyzed at 800°C for 2 h under a nitrogen atmosphere with a controlled flow rate of 1 L / min and a heating rate of 5°C / min to obtain sludge biochar.

[0044] 2. Wash the sludge biochar with deionized water 5 times, dry it at 80°C, and grind it through a 50-80 mesh sieve to obtain washed sludge biochar;

[0045] 3. Add anthraquinone-2-sulfonate sodium AQS to a three-necked flask, then add 40 mL of dichloromethane, place the three-necked flask in a constant temperature water bath, and add 2.2 mL of thionyl chloride when the temperature reaches 60 ° C. After reacting for 2 hours, turn off the constant temperature water bath and cool to room temperature. Filter the resulting reaction solution, rotary evaporate, and then dissolve it with 60 mL of dichloromethane, filter again, and rotary evaporate to obtain solid anthraquinone-2-sulfonyl chloride;

[0046] 4. Add 5 g of washed sludge biochar into 5000 mL of deionized water, adjust the pH of the system to 10 with ammonia water, heat the mixture to 98 ° C, add 20 mL of diacetyltriamine, and stir at 98 ° C for 8 hours. After the reaction is completed, filter and dry the filtered solid matter in a vacuum oven for 24 hours to obtain ammoniated sludge biochar;

[0047] 5. Place 1g of aminated biochar in a solution of equal volumes of anhydrous ethanol and dichloromethane, then add 4g of anthraquinone-2-sulfonyl chloride, place it in a constant temperature drying oven at 35°C to react for 2h, and after the reaction is completed, place the solution in an oven at 60°C to dry to obtain quinone mediator-modified biochar material.

[0048] Example 2: Anaerobic flocculent sludge from a municipal sewage treatment plant was inoculated into an upflow anaerobic reactor (UASB). The sludge concentration was 24.31 g / MLSS, the concentration of quinone mediator-modified biochar was 3.15 g / gMLSS, and the specific surface area of ​​quinone mediator-modified biochar was 325.5 m 2 / g, the particle size of biochar particles is 0.18-0.27mm. After mixing, it is added to the sludge area and then the simulated wastewater is introduced. The main components of the simulated wastewater are glucose, ammonium chloride, potassium dihydrogen phosphate, sodium bicarbonate and trace elements. The COD:N:P ratio is 200:5:1. The COD concentration is initially 1000mg / L and gradually increases to 10000mg / L. The hydraulic retention time is 18h, the reaction temperature is 35±2℃, and the pH is maintained at around 7.0. The COD concentration changes, gas production changes and sludge particle size after 50 days of reaction are continuously monitored.

[0049] Before the wastewater enters the reactor, nitrogen is introduced for 20 minutes to ensure that no oxygen remains in the reactor and to achieve uniform mixing of the sludge and biochar particles. The pH is maintained at approximately 8.0, the reaction temperature is approximately 35°C, and the hydraulic retention time is 24 hours. The COD concentration of the influent is gradually increased from 400 mg / L to 15,000 mg / L. Changes in COD concentration and gas production are monitored continuously for 64 days.

[0050] During the implementation process, a control group was set up, in which no quinone-modified biochar was added. Compared to the control group, the COD removal rate of the experimental group with quinone-modified biochar stabilized at 97.25% after 21 days, while the COD removal rate of the control group stabilized at 89.23%. After 50 days, the average particle size of the sludge in the experimental group was 512.25μm, while the average particle size of the control group was 414.56μm. The methane content of the biogas produced by the reactor with quinone-modified biochar was approximately 56%, while that of the control group was approximately 44%, indicating that the addition of quinone-modified biochar can improve the efficiency of the anaerobic reaction system.

[0051] Example 3: In this example, granular sludge was removed and added to an expanded granular sludge bed (EGSB) reactor to treat simulated printing and dyeing wastewater containing the azo dye Reactive Red 2 (Reactive Brilliant Red X-3B). The EGSB reactor was equipped with a water inlet at the bottom, an air outlet at the top, a water outlet at the top side, and an internal reflux port at the top side. After the granular sludge was added to the reactor, the influent Reactive Red 2 concentration was 100 mg / L and the COD was approximately 1000 mg / L. The reactor used an internal circulation method to increase the upward flow rate to 3 m / h. After 14 days of acclimation, the influent dye concentration was gradually increased in steps of 100 mg / L, with each concentration increase cycle lasting 20 days, until it reached 400 mg / L.

[0052] After long-term operation (150 days), the reaction system can achieve a removal rate of 83-95% for Reactive Red 2. As the dye concentration increases, the COD removal rate can also reach 81-95%, showing a good decolorization effect on Reactive Red 2.

[0053] In summary, the present invention utilizes quinone-modified biochar particles as the core, improving the rapid granulation of anaerobic sludge and forming granular sludge with high anaerobic reduction capacity. This method provides a new approach for the resource utilization of excess sludge and can be applied to the anaerobic treatment of printing and dyeing wastewater, improving the anaerobic biological treatment of azo dyes.

Claims

1. A method for preparing a quinone-modified biochar material, characterized in that The preparation method is achieved by the following steps:

1. The residual sludge from the secondary sedimentation tank of the sewage treatment plant is placed in a tubular furnace and pyrolyzed under a nitrogen atmosphere to obtain sludge biochar; 2. Washing the sludge biochar with deionized water for multiple times, drying, grinding and sieving to obtain washed sludge biochar; 3. dissolving sodium anthraquinone-2-sulfonate in dichloromethane, adding thionyl chloride to carry out chlorination reaction at a temperature of 55-65° C., and evaporating the solvent to obtain anthraquinone-2-sulfonyl chloride; Fourth, immerse the washed sludge biochar in deionized water, add ammonia water to adjust the pH of the system to 10, heat to 90-98°C, add diacetyltriamide, and continue to stir the mixed reaction solution for 8-10 hours. After the reaction is completed, filter and dry to obtain amination sludge biochar; 5. Place the amination sludge biochar in a mixed solution of anhydrous ethanol and dichloromethane, add anthraquinone-2-sulfonyl chloride, react at a temperature of 35-40°C for 2-4h, and dry after the reaction to obtain a quinone mediator modified biochar material.

2. The method for preparing the quinone mediator modified biochar material according to claim 1, characterized in that The excess sludge described in step 1 is the settled sludge in the secondary sedimentation tank.

3. The method for preparing the quinone mediator modified biochar material according to claim 1, characterized in that During the pyrolysis treatment process described in step 1, the nitrogen flow rate was controlled to be 1 L / min, the heating rate was 5° C. / min, and the high-temperature pyrolysis was carried out at 800° C. for 2 h.

4. The method for preparing the quinone mediator modified biochar material according to claim 1, characterized in that In step five, the mass ratio of the amination sludge biochar to anthraquinone-2-sulfonyl chloride is 1:(3-6).

5. The method for preparing the quinone mediator modified biochar material according to claim 1, characterized in that In step 5, the reaction is carried out at a temperature of 35-40° C. for 2 h.

6. The reaction device for granulating floc sludge is characterized by The reaction device comprises a reactor chamber (1), a three-phase separator (2) and a circulating water pump (3); the bottom of the reactor chamber (1) is in an inverted cone shape, the middle of the reactor chamber (1) is in a cylindrical shape, the top of the reactor chamber (1) is provided with the three-phase separator (2), the bottom of the reactor chamber (1) is provided with a water inlet (1-1), the middle of the reactor chamber (1) is a sludge zone, the sludge zone is filled with a mixture of quinone mediator-modified biochar material and anaerobic sludge, the top of the sludge zone is provided with a reflux port, one end of a reflux pipe (4) is connected to the reflux port, the other end of the reflux pipe (4) is connected to the water inlet, the circulating water pump (3) is provided on the reflux pipe (4), the top of the three-phase separator (2) is provided with an air outlet (2-1), and the side wall of the three-phase separator (2) is provided with a water inlet (2-2).

7. The reaction device for granulating floc sludge according to claim 6 is characterized in that A water distribution plate is arranged at the lower part of the sludge area.

8. The reaction device for granulating flocculent sludge according to claim 6, characterized in that A plurality of sampling ports (5) are provided in the middle of the reactor chamber (1) along the height direction.

9. The reaction device for granulating flocculent sludge according to claim 6, characterized in that The concentration of anaerobic sludge in the sludge area is 3000-3500 mg / L.

10. The reaction device for granulating floc sludge according to claim 6, characterized in that The concentration of quinone mediator-modified biochar particles in the sludge area was 2.5-3.5 g / gMLSS.

Images