Preparation method of CMC-Na modified biochar and its application in ammonia nitrogen wastewater treatment

Abstract

This invention relates to the field of wastewater treatment technology, and discloses a method for preparing CMC-Na modified biochar and its application in ammonia nitrogen wastewater treatment. The method for preparing CMC-Na modified biochar converts reed straw into biochar, achieving not only the resource utilization of agricultural waste, but also the biochar's porous structure and large specific surface area, which are beneficial for adsorption and catalytic reactions. The introduction of CMC-Na further improves the surface properties and pore structure of the biochar, enhancing its electron transport capacity. Furthermore, this invention adds CMC-Na modified biochar powder (CMC-BC) to an anaerobic iron ammonia oxidation sludge system, achieving an ammonia nitrogen removal rate of nearly 100% and near-zero ammonia nitrogen discharge. Simultaneously, it significantly improves the total nitrogen removal efficiency and electron transport rate, positively impacting the functional microorganisms of the anaerobic iron ammonia oxidation system.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for preparing CMC-Na modified biochar and its application in ammonia nitrogen wastewater treatment. Background Technology

[0002] Nitrogenous wastewater leads to eutrophication, causing ecosystem disruption and toxicity that impacts human health. While traditional nitrification, denitrification, and anaerobic ammonia oxidation (Anammox) processes each have their advantages, they also present a series of problems. The former is a mature technology that reduces nitrogen pollution in water bodies, but it consumes a lot of energy and has a complex process flow. The latter can reduce energy consumption and carbon sources to some extent, but it requires harsh conditions and nitrogen removal is unstable. Anaerobic iron ammonia oxidation (Feaammox) is a microbial-mediated reduction of iron into ammonia under anaerobic conditions. Under autotrophic conditions in a single-stage reactor, it reduces NH4+ to iron. + Converted into N2 and NO3 - and NO2 - This process requires no carbon source, consumes little energy, produces low sludge output, eliminates the need for regular sludge removal, and generates no greenhouse gases.

[0003] However, research on the Feammox process is still in its early stages, and the biggest challenges currently faced are its low nitrogen conversion rate and solid Fe(III) reduction rate. Given the uncontrollable environmental factors and reaction substrates, adding exogenous substances that can improve Feammox efficiency has become an effective method. Electron shuttles, as redox-active substances, can play this role and have been shown to accelerate Feammox reaction efficiency. Although some soluble ESs, such as humic substances and riboflavin, can significantly accelerate the reaction rate, their continuous addition and secondary pollution still lead to high costs and environmental problems. Therefore, insoluble ESs have the potential for application in the extracellular microbial reduction of Fe(III) and the recovery of redox mediators. Biochar, as an excellent insoluble electron shuttle, is also rich in quinones, hydroquinones, and fused aromatic (sub)structures with redox-active groups on its surface, which play an important role in electron transfer in biochemical processes. Quinone molecules can enhance the ability of electrons to transfer from ammonium to Fe(III), promoting functional microbial-mediated NH4+. + Oxidation and Fe(III) reduction. Therefore, researching and developing an efficient, low-cost, and environmentally friendly electron shuttle to provide a green and low-energy-consumption new method for the treatment of nitrogen pollution in water bodies is of great engineering significance. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing CMC-Na modified biochar and its application in ammonia nitrogen wastewater treatment, which solves the problem of limited ammonia nitrogen removal by anaerobic iron ammonia oxidation.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a method for preparing CMC-Na modified biochar and its application in ammonia nitrogen wastewater treatment, comprising the following steps:

[0007] Step 1: Rinse the reed stalks with distilled water and dry them, then cut them into small pieces and sieve them to obtain biomass powder;

[0008] Step 2: Weigh a certain amount of biomass powder and place it evenly in a ceramic boat. Place the ceramic boat in a tube furnace, extract the air from the tube furnace to a near-vacuum state, and then introduce N2. Repeat this process 3 to 5 times.

[0009] Step 3: Heat to the preset temperature, maintain the temperature for 100-150 minutes, then start cooling down. Remove the sample after it has cooled to room temperature.

[0010] Step 4: After cleaning and drying the extracted sample, unmodified biochar powder BC is obtained;

[0011] Step 5: Dissolve CMC-Na powder in deionized water at 40~60℃ and stir for 15~30 min to obtain CMC-Na hydrogel;

[0012] Step 6: Add unmodified biochar powder BC to CMC-Na hydrogel and stir in a water bath at 50~100℃ for 1~1.5h to obtain a mixed solution;

[0013] Step 7: After the reaction, let it stand, centrifuge with ultrapure water until the supernatant is neutral and colorless, and then freeze-dry under vacuum.

[0014] Step 8: Grind the vacuum freeze-dried biochar to obtain CMC-Na modified biochar powder CMC-BC.

[0015] A further improvement of the present invention is that, in step 1, the dried reed stalks are cut into small pieces of 1-3 cm, ground, and passed through an 80-mesh sieve to obtain biomass powder.

[0016] A further improvement of the present invention is that, in step 3, the temperature is increased to a preset temperature at a rate of 3~6℃ / min, wherein the preset temperature is 500℃.

[0017] A further improvement of the present invention is that, in step 4, the drying temperature is 50~80℃ and the drying time is 10~15h.

[0018] A further improvement of this invention is that the specific method for obtaining the CMC-Na hydrogel in step 5 is as follows:

[0019] Step 5.1: Measure a certain amount of deionized water and place it in a beaker, then heat it in a water bath to 40~60℃;

[0020] Step 5.2: Weigh a certain amount of CMC-Na powder and dissolve it in deionized water while stirring.

[0021] Step 5.3: Place the magnetic stirrer in a water bath, maintain the water bath temperature at 40~60℃, the stirring speed at 500~700rpm, and the stirring time at 15~30min. After the reaction is complete, a uniformly mixed CMC-Na hydrogel is obtained.

[0022] A further improvement of the present invention is that, in step 5, the concentration of CMC-Na hydrogel is 10 g / L.

[0023] A further improvement of the present invention is that, in step 6, unmodified biochar powder BC is added to the CMC-Na hydrogel, and the mass ratio of CMC-Na / BC is 1:(1~10).

[0024] A further improvement of this invention is that the specific method for obtaining the mixed solution in step 6 is as follows:

[0025] Step 6.1: Weigh a certain amount of unmodified biochar powder BC and place it into a well-mixed CMC-Na hydrogel, and sonicate for 1~5 min until the biochar powder dissolves.

[0026] Step 6.2: Place the magnetic stirrer in a water bath at a temperature of 50-100℃ and a speed of 500-700 rpm for 1-1.5 hours. Once the reaction is complete, a fully reacted and homogeneous mixed solution will be obtained.

[0027] A further improvement of the present invention is that, in step 7, the number of centrifugal washing cycles is 3 to 5.

[0028] This invention also provides an application of CMC-Na modified biochar for the treatment of ammonia nitrogen wastewater.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention provides a method for preparing CMC-Na modified biochar. By converting reed straw into biochar, not only is the resource utilization of agricultural waste realized, but the biochar itself has a porous structure and a large specific surface area, which is beneficial to adsorption and catalytic reactions. The introduction of CMC-Na further improves the surface properties and pore structure of the biochar and enhances its electron transfer capacity. Moreover, the preparation method of this invention has clear steps, is easy to operate, and is easy to apply and promote on an industrial scale.

[0031] This invention also provides an application of CMC-Na modified biochar in ammonia nitrogen wastewater treatment. By directly adding CMC-Na modified biochar to the influent of the anaerobic iron ammonia oxidation process, the ammonia nitrogen removal rate can reach nearly 100%, with near-zero ammonia nitrogen discharge. At the same time, it significantly improves the total nitrogen removal efficiency and electron transfer rate, and has a positive effect on the functional microorganisms of the anaerobic iron ammonia oxidation system. Attached Figure Description

[0032] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components of the invention.

[0033] Figure 1 These are scanning electron microscope (SEM) images of modified biochar CMC-BC with a CMC-Na / BC mass ratio of 1:8 and unmodified biochar BC.

[0034] Figure 2 This is a graph showing the nitrogen changes of biochar with different proportions of CMC-Na added in Examples 1 and 2;

[0035] Figure 3 This is a graph showing the nitrogen changes in Example 1 and Comparative Example 1 after the addition of modified biochar CMC-BC and unmodified biochar BC.

[0036] Figure 4 The graph shows the changes in cytochrome c (cytc) and INT-ETS content before and after culture in the ASBR reactor in Example 1 and Comparative Example 1. Detailed Implementation

[0037] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0038] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0039] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0040] In this article, unless otherwise specified, “contains,” “includes,” “contains,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of”. For example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a”.

[0041] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0042] This invention provides a method for preparing CMC-Na modified biochar, comprising the following steps:

[0043] Step 1: Rinse the reed stalks with distilled water and dry them in an oven. Then, cut them into small pieces of 1-3cm, grind them clockwise, and pass them through an 80-mesh sieve to obtain biomass powder.

[0044] It should be noted that since biomass powder is very easy to float in the air, the stirring force and speed need to be controlled during the grinding process, and the amount of biomass added should be appropriate.

[0045] Step 2: Weigh a certain amount of biomass powder and place it evenly in a ceramic boat. Place the ceramic boat in the center of the constant temperature zone of the tube furnace. Use a vacuum pump to extract the air in the tube furnace to a near-vacuum state and then introduce N2. Repeat this process 3 to 5 times.

[0046] Step 3: Start the heating program and heat to the preset temperature at a rate of 3~6℃ / min. Maintain the temperature for 100~150min and then start cooling. Remove the sample after it has cooled to room temperature.

[0047] Step 4: After thoroughly washing the extracted sample with deionized water and anhydrous ethanol, dry it in a drying oven at 50~80℃ for 10~15h to obtain unmodified biochar powder BC.

[0048] Step 5: Measure a certain amount of deionized water and place it in a beaker. Heat the beaker to 40-60°C in a water bath. Then weigh a certain amount of CMC-Na powder and dissolve it in the deionized water while stirring. Place the magnetic stirrer in the water bath and maintain the water bath temperature at 40-60°C. The stirring speed is 500-700 rpm and the stirring time is 15-30 minutes. After the reaction is complete, a uniformly mixed CMC-Na hydrogel is obtained.

[0049] Step 6: Weigh a certain amount of unmodified biochar powder BC and place it into the uniformly mixed CMC-Na hydrogel, so that the mass ratio of CMC-Na hydrogel to unmodified biochar powder BC is 1:(1~10). Then, sonicate for 1~5 minutes until the biochar powder dissolves. Place the magnetic stirrer in a water bath at a temperature of 50~100℃ and a speed of 500~700 rpm for 1~1.5 hours. After the reaction is completed, a fully reacted and uniform mixed solution is obtained.

[0050] Step 7: After the reaction is complete, let it stand and wash it with ultrapure water by centrifugation 3 to 5 times until the supernatant is neutral and colorless, then perform vacuum freeze drying;

[0051] Step 8: Grind the vacuum freeze-dried biochar to obtain CMC-Na modified biochar powder CMC-BC.

[0052] This invention also provides an application of CMC-Na modified biochar in ammonia nitrogen wastewater treatment. By adding CMC-BC modified biochar to anaerobic iron ammonia oxidation sludge, the ammonia nitrogen removal performance and electron transfer rate of the anaerobic iron ammonia oxidation process can be significantly improved.

[0053] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0054] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0055] Example 1

[0056] This embodiment provides a method for preparing CMC-Na modified biochar, including the following steps:

[0057] Step 1: Rinse the reed stalks with distilled water, dry them in an oven, cut them into 2cm long pieces, grind them clockwise, and pass them through an 80-mesh sieve to obtain biomass powder;

[0058] Step 2: Weigh 2g of biomass powder and place it evenly in a ceramic boat. Place the ceramic boat in the center of the constant temperature zone of the tube furnace. Use a vacuum pump to extract the air from the tube furnace until the furnace is close to a vacuum state, then introduce N2. Repeat three times.

[0059] Step 3: After the heating program is started, the temperature is increased to the preset temperature of 500℃ at a rate of 5℃ / min. The temperature is held constant for 120 minutes and then the temperature is lowered. The sample is removed after the temperature drops to room temperature.

[0060] Step 4: After thoroughly washing the extracted sample with deionized water and anhydrous ethanol, dry it in an oven at 60°C for 12 hours to obtain unmodified biochar powder BC.

[0061] Step 5: Measure 200ml of deionized water and place it in a beaker. Heat the beaker to 50℃ in a water bath. Then weigh 2g of CMC-Na (sodium carboxymethyl cellulose) powder and add the CMC-Na powder to the deionized water while stirring and dissolving. Place the magnetic stirrer in the water bath and maintain the water bath temperature at 50℃, the stirring speed at 600rpm, and the stirring time at 20min. After the reaction is complete, a uniformly mixed 10g / L CMC-Na hydrogel is obtained.

[0062] Step 6: Set the mass ratio of CMC-Na / BC to 1:8, weigh 16g of unmodified biochar powder BC and place it into 200ml of well-mixed CMC-Na hydrogel. Sonicate for 2min until the biochar powder dissolves. Place the magnetic stirrer in a water bath and maintain the water bath temperature at 90℃, the stirring speed at 600rpm, and the stirring time at 1h. After the reaction is complete, a well-reacted and homogeneous mixed solution is obtained.

[0063] Step 7: After the mixed solution has been allowed to stand and precipitate for 1 hour, it is washed 3 times by centrifugation with ultrapure water until the supernatant is neutral and colorless. Then, the solution is placed in a freezer at -80°C for 24 hours and then placed in a vacuum freezer for freeze-drying for 48 hours.

[0064] Step 8: Grind the vacuum freeze-dried biochar to obtain CMC-Na modified biochar powder CMC-BC.

[0065] Example 2:

[0066] This embodiment provides a method for preparing CMC-Na modified biochar. The mass ratio of CMC-Na to BC is set at 1:2. 4g of unmodified biochar powder BC is weighed and placed in 200ml of a uniformly mixed CMC-Na hydrogel. The mixture is sonicated for 2 minutes until the biochar powder dissolves. A magnetic stirrer is placed in a water bath, maintaining the water bath temperature at 90℃ and the stirring speed at 600rpm for 1 hour. After the reaction is complete, a fully reacted and homogeneous mixed solution is obtained. Details not mentioned in this embodiment are the same as described in Example 1.

[0067] Example 3

[0068] This embodiment provides a method for preparing CMC-Na modified biochar. The mass ratio of CMC-Na to BC is set at 1:4. 8g of unmodified biochar powder BC is weighed and placed into 200ml of uniformly mixed CMC-Na hydrogel. The mixture is sonicated for 2 minutes until the biochar powder dissolves. A magnetic stirrer is placed in a water bath, maintaining the water bath temperature at 90℃ and the stirring speed at 600rpm for 1 hour. After the reaction is complete, a fully reacted and homogeneous mixed solution is obtained. Details not mentioned in this embodiment are the same as described in Example 1.

[0069] Example 4

[0070] This embodiment provides a method for preparing CMC-Na modified biochar. The mass ratio of CMC-Na to BC is set at 1:6. 12g of unmodified biochar powder BC is weighed and placed into 200ml of a uniformly mixed CMC-Na hydrogel. The mixture is sonicated for 2 minutes until the biochar powder dissolves. A magnetic stirrer is placed in a water bath, maintaining the water bath temperature at 90℃ and the stirring speed at 600rpm for 1 hour. After the reaction is complete, a fully reacted and homogeneous mixed solution is obtained. Details not mentioned in this embodiment are the same as described in Example 1.

[0071] Example 5

[0072] This embodiment provides a method for preparing CMC-Na modified biochar. The mass ratio of CMC-Na to BC is set at 1:10. 20g of unmodified biochar powder BC is weighed and placed into 200ml of uniformly mixed CMC-Na hydrogel. The mixture is sonicated for 2 minutes until the biochar powder dissolves. A magnetic stirrer is placed in a water bath, maintaining the water bath temperature at 90℃ and the stirring speed at 600rpm for 1 hour. After the reaction is complete, a fully reacted and homogeneous mixed solution is obtained. Details not mentioned in this embodiment are the same as described in Example 1.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing powdered biochar, comprising the following steps:

[0075] Step 1: Rinse the reed stalks with distilled water, dry them in an oven, cut them into 2cm long pieces, grind them clockwise, and pass them through an 80-mesh sieve to obtain biomass powder;

[0076] Step 2: Weigh 2g of biomass powder and place it evenly in a ceramic boat. Place the ceramic boat in the center of the constant temperature zone of the tube furnace. Use a vacuum pump to extract the air from the tube furnace until the furnace is close to a vacuum state, then introduce N2. Repeat three times.

[0077] Step 3: After the heating program is started, the temperature is increased to the preset temperature of 500℃ at a rate of 5℃ / min. The temperature is held constant for 120 minutes and then the temperature is lowered. The sample is removed after the temperature drops to room temperature.

[0078] Step 4: After thoroughly washing the extracted sample with deionized water and anhydrous ethanol, dry it in an oven at 60°C for 12 hours to obtain unmodified powdered biochar BC.

[0079] This invention also provides a method for treating ammonia nitrogen wastewater based on CMC-BC modified biochar-enhanced anaerobic iron ammonia oxidation, comprising the following steps:

[0080] Step 1, anaerobic iron ammonia oxidation sludge pretreatment: anaerobic iron ammonia oxidation sludge with long-term stable operation and good performance of ASBR is used, and the concentration of anaerobic iron ammonia oxidation sludge is adjusted to 5200±500mg / L, and the ammonia nitrogen removal rate is maintained at about 40%.

[0081] Step 2, Preparation of simulated wastewater solution containing ammonia nitrogen: Includes the following components at the following mass concentrations: 50 mg N / L NH4+ + -N, 24mg Fe 3+ The solution contains FeCl3 at a concentration of 43 mg / L, KH2PO4 at a concentration of 43 mg / L, glucose at a concentration of 75 mg COD / L, NaHCO3 at a concentration of 500 mg / L, and a trace element concentrate at a concentration of 0.75 mL / L. The trace element concentrate comprises the following sub-components at mass concentrations: 8630 mg / L Na2EDTA, 640 mg / L ZnSO4·7H2O, 360 mg / L CoCl2·6H2O, 490 mg / L MnCl2·4H2O, 130 mg / L CuSO4·5H2O, 330 mg / L Na2MoO4·2H2O, 280 mg / L NiCl2·6H2O, 310 mg / L NaSeO4·10H2O, and 14 mg / L H3BO3.

[0082] Step 3: An anaerobic sequencing batch reactor (ASBR) with an effective volume of 3L is used. The influent and effluent are artificially fed in and out. The water exchange ratio is set at 50%, and the hydraulic retention time is 2 days. The ASBR reactor is mechanically stirred at a speed of 150 rpm. The operating temperature of the ASBR reactor is controlled at approximately 25-30℃, the dissolved oxygen in the influent is less than 0.2 mg / L, and the dissolved oxygen in the reactor is controlled to be less than 0.6 mg / L. The ASBR reactor uses a timer to control a single operating cycle of 24 hours, with the following time intervals for each stage: influent 0.3 hours, stirring 21 hours, sedimentation 2 hours, and effluent 0.3 hours.

[0083] Step 4: Two sets of experiments were set up respectively. In the first set of experiments, 15g of five different CMC-Na / BC modified biochar (Example 1, Example 2, Example 3, Example 4 and Example 5) were added to five reactors at a mass ratio of 5g / L. The control group without added biochar was used as a blank control group. The experiment was run for 36h to explore the short-term effects of adding different modified biochar on anaerobic iron ammonia oxidation.

[0084] Step 5, the second group of experiments: equal amounts of 15g biochar (Example 1 and Comparative Example 1) were added to two different reactors (CMC-BC and BC) at a dosage of 5g / L. The control group without added biochar was used as a blank control group. The experiment was run for 30 days to explore the long-term effect of adding modified CMC biochar on anaerobic iron ammonia oxidation.

[0085] Step 6: After the two sets of experimental reactions are completed, take the supernatant and filter it through a 0.45um filter membrane to measure the changes in the reaction matrix (nitrogen: ammonia nitrogen, nitrite nitrogen and nitrate nitrogen). Take the sludge mixture to measure the energy metabolism level indicators (changes in cytochrome c (cytc) and INT-ETS content) of the second set of experiments.

[0086] like Figure 1 As shown, unmodified reed biochar has a smooth surface, a tubular structure, and irregular grooves between the frameworks, with no obvious pore structure observed. In contrast, CMC-modified biochar has a rough and uneven surface with many small particles attached, is the most dense, and has multiple pore structures. The presence of these abundant pore structures and surface particles provides adsorption sites for the biochar, giving it good physical adsorption capacity.

[0087] like Figure 2 As shown, adding different proportions of CMC-BC all resulted in less residual ammonia nitrogen in the anaerobic iron ammonia oxidation system compared to not adding biochar. Among them, the modified biochar with a CMC / BC mass ratio of 1:8 produced NH4+. + -N removal efficiency is the highest, reaching 99.36%.

[0088] like Figure 3As shown, compared with the blank control group and the group with unmodified biochar (BC), when 5 g / L CMC-BC was added to the ASBR reactor, the ammonia nitrogen concentration in the effluent of the ASBR reactor was significantly reduced, with an average NH4+ concentration of [missing information]. + -N removal rate reached 95.10%. In addition, a decrease in nitrate concentration in the effluent was observed, and the total nitrogen removal performance was further improved, with an average TN removal rate of 74.05%, which was significantly higher than that of the control group (54.48%) and the BC group (67.86%).

[0089] like Figure 4 As shown, the energy metabolism level indicators before and after ASBR reactor culture are shown. When 5 g / L CMC-BC is added to the ASBR reactor, the cytochrome C (c-Cyts) content is significantly increased compared with the blank control group and the group with unmodified biochar BC, and the electron transport system activity (INT-ETS) is 68.58% and 21.94% higher than the blank group and BC, respectively.

[0090] In conclusion, adding 5 g / L of CMC-BC modified biochar to anaerobic iron ammonia oxidation sludge at a concentration of 5200±500 mg / L can significantly improve the ammonia nitrogen removal performance and electron transfer rate of the anaerobic iron ammonia oxidation process.

[0091] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing CMC-Na modified biochar, characterized in that, Includes the following steps: Step 1: Rinse the reed stalks with distilled water and dry them, then cut them into small pieces and sieve them to obtain biomass powder; Step 2: Weigh a certain amount of biomass powder and place it evenly in a ceramic boat. Place the ceramic boat in a tube furnace, extract the air from the tube furnace to a near-vacuum state, and then introduce N2. Repeat this process 3 to 5 times. Step 3: Increase the temperature to 500℃ at a rate of 3~6℃ / min, maintain the temperature for 100~150min, then start cooling down. Remove the sample after it has cooled to room temperature. Step 4: After cleaning and drying the extracted sample, unmodified biochar powder BC is obtained; Step 5: Measure a certain amount of deionized water and place it in a beaker. Heat the beaker to 40-60°C in a water bath. Weigh a certain amount of CMC-Na powder and dissolve it in the deionized water while stirring. Place a magnetic stirrer in the water bath, maintain the water bath temperature at 40-60°C, the stirring speed at 500-700 rpm, and the stirring time at 15-30 minutes. After the reaction is complete, a uniformly mixed CMC-Na hydrogel with a concentration of 10 g / L is obtained. Step 6: Weigh a certain amount of unmodified biochar powder BC and place it into a uniformly mixed CMC-Na hydrogel. Sonicate the mixture for 1-5 minutes until the biochar powder dissolves. Place a magnetic stirrer in a water bath at a temperature of 50-100℃ and a speed of 500-700 rpm for 1-1.5 hours. Once the reaction is complete, a fully reacted and homogeneous mixed solution is obtained. The mass ratio of CMC-Na to BC is 1:(1-10). Step 7: After the reaction, let it stand, centrifuge with ultrapure water until the supernatant is neutral and colorless, and then freeze-dry under vacuum. Step 8: Grind the vacuum freeze-dried biochar to obtain CMC-Na modified biochar powder CMC-BC.

2. The method for preparing CMC-Na modified biochar according to claim 1, characterized in that, In step 1, the dried reed stalks are cut into small pieces of 1-3 cm, ground, and passed through an 80-mesh sieve to obtain biomass powder.

3. The method for preparing CMC-Na modified biochar according to claim 1, characterized in that, In step 4, the drying temperature is 50~80℃ and the drying time is 10~15h.

4. The method for preparing CMC-Na modified biochar according to claim 1, characterized in that, Its features are, In step 7, the centrifugal washing is performed 3 to 5 times.

5. An application of CMC-Na modified biochar prepared by the method described in claim 1, characterized in that, CMC-Na modified biochar for ammonia nitrogen wastewater treatment.

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