Two-dimensional layered corncob biomass charcoal adsorbent and preparation method thereof

Abstract

The invention discloses a two-dimensional layered corncob biomass charcoal adsorbent and a preparation method thereof.The preparation method of the two-dimensional layered corncob biomass charcoal adsorbent comprises the following steps that corncobs are cut into pieces, activated through an ammonia / amine activating agent aqueous solution, washed and dried, and activated corncob particles are obtained; and performing low-temperature carbonization and high-temperature heat treatment to obtain the two-dimensional layered corncob biomass charcoal adsorbent. The method is simple to operate, low in cost and low in equipment requirement, and the prepared corncob biomass charcoal adsorbent has a loose two-dimensional layered structure and has excellent adsorption performance on anionic organic dyes. In addition, the corncob biomass charcoal adsorbent is used for treating organic dye sewage, so that the sewage treatment cost can be reduced, and agricultural waste resource conversion and comprehensive utilization are also realized.

Description

Technical Field

[0001] The invention relates to the technical field of waste resource conversion and utilization and sewage purification, and more specifically, to a two-dimensional layered corncob biomass charcoal adsorbent and a preparation method thereof. Background Art

[0002] With the improvement of production level and people's quality of life in today's society, people's requirements for color are also gradually increasing, leading to the continuous expansion and improvement of the printing and dyeing industry. The organic dye wastewater produced has gradually become a major problem in today's society, bringing a lot of trouble to people. my country is a major dye production and consumption country. If these wastewaters are not effectively treated, they will cause serious harm to the ecological environment and human health.

[0003] In recent years, my country has stepped up its efforts in sewage treatment and developed a series of effective measures. Among them, adsorption is currently an important method for treating difficult-to-degrade organic dye wastewater. The purpose of water purification is achieved by fully contacting the adsorbent with the sewage to remove pollutants in the water. Biomass carbon has the advantages of wide sources, low cost and simple preparation. It also has rich pore sizes and surface functional groups and has good adsorption properties for organic dyes. my country is a major corn-growing country, and corn cobs are the main agricultural by-products. Therefore, using them as raw materials for the preparation of biomass carbon adsorbents can turn waste into treasure, achieve a close combination of economic benefits and environmental protection, and is more in line with the theme of development in today's era.

[0004] In recent years, researchers often combine activator pretreatment and high-temperature carbonization / activation to prepare corn cob biomass charcoal adsorbents. However, the activation system and process are relatively complex and energy-intensive. For example, CN114804099A reported that corn cobs were activated twice using HCl / FeCl3 and KOH as activators under high temperature conditions under nitrogen atmosphere protection, and corn cob biomass charcoal adsorbents were obtained after cooling. Although there are many reports on the preparation of corncob biochar adsorbents by one-step activation of acid, alkali and CO2, such as Environmental Science and Pollution Research, 2013, 20(12): 8521-8534; New Carbon Materials, 2018, 33(4): 303-309; BioResources, 2020, 15(4): 7342-7356; Laboratory Research and Exploration, 2019, 38(8): 21-24, etc., the corncob biochar prepared by the above technology has excellent adsorption performance for anionic methyl orange organic dyes and can be used to treat organic dye wastewater. However, the high-temperature carbonization / activation process involved in the preparation technology of the above corncob biochar adsorbent is often carried out under oxygen-limited or oxygen-free conditions, which undoubtedly increases the requirements for equipment and increases the technical parameters that need to be controlled during the preparation process. The preparation process is cumbersome and not simple. In addition, the corncob biochar adsorbents prepared by the above technology are mostly block structures with poor adsorption performance. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and provide a two-dimensional layered corncob biomass charcoal adsorbent and a preparation method thereof.

[0006] In one aspect, a method for preparing a two-dimensional layered corncob biochar adsorbent comprises:

[0007] (1) obtaining soft tissue at the center of a natural corn cob, soaking, filtering, washing, drying, and chopping the soft tissue to obtain corn cob particles;

[0008] (2) soaking the corncob particles in an aqueous solution of an ammonia / amine activator and heating under reflux to obtain activated corncob particles;

[0009] (3) carbonizing the activated corncob particles at low temperature to obtain an amorphous carbon material;

[0010] (4) The amorphous carbon material is subjected to high temperature heat treatment, and after cooling, a two-dimensional layered corn cob biomass carbon adsorbent is obtained.

[0011] In another aspect, a two-dimensional layered corncob biomass charcoal adsorbent is prepared by the above-mentioned preparation method of the two-dimensional layered corncob biomass charcoal adsorbent.

[0012] Implementing the embodiments of the present invention will have the following beneficial effects:

[0013] (1) In the present embodiment, ammonia / amine activators are first used for heating and reflux activation. On the one hand, active groups such as amino (-NH2) and hydroxyl (-OH) are introduced, which have excellent adsorption properties for anionic organic dyes such as methyl orange and Congo red. On the other hand, NH4 + Or amine small molecules can strip corn cob biochar by intercalation / de-intercalation, and finally obtain two-dimensional layered corn cob biochar with excellent adsorption performance, and finally optimize the pore structure, specific surface area and functional group type / density of corn cob biochar.

[0014] (2) The present invention converts the activated corn cob particles into an amorphous carbon material with high thermal stability through low-temperature carbonization to avoid ashing during high-temperature heat treatment by reaction with oxygen. The high-temperature heat treatment process can be carried out in an air atmosphere, thereby reducing the high requirements of high-temperature heat treatment on equipment and reaction conditions.

[0015] (3) Using corn cob biochar adsorbent to treat organic dye wastewater can not only reduce the cost of wastewater treatment, but also realize the comprehensive utilization of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] in:

[0018] Figure 1 This is the X-ray diffraction spectrum of the two-dimensional layered corncob biomass charcoal adsorbent of Example 1.

[0019] Figure 2 This is a scanning electron microscope photograph of the two-dimensional layered corncob biomass charcoal adsorbent of Example 1.

[0020] Figure 3 The following are product photos of Example 1 and Comparative Examples 1-4.

[0021] Figure 4 This is a diagram showing the adsorption effect of methyl orange dye by the two-dimensional layered corncob biomass charcoal adsorbent of Example 1 and Comparative Examples 1, 3, and 4. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention discloses a method for preparing a two-dimensional layered corncob biochar adsorbent, comprising the following steps:

[0024] (1) obtaining soft tissue at the center of a natural corn cob, soaking, filtering, washing, drying, and chopping the soft tissue to obtain corn cob particles.

[0025] Specifically, the air-dried natural corn cobs are cracked open, the soft tissue in the middle is taken out, and the soft tissue is soaked, filtered and washed with deionized water to remove dust and soluble impurities, and then dried and chopped to obtain corn cob particles.

[0026] Optionally, the drying temperature is 60°C-110°C.

[0027] (2) Soaking the corncob particles in an aqueous solution of an ammonia / amine activator and heating under reflux to obtain activated corncob particles.

[0028] Specifically, the corn cob particles are immersed in an aqueous solution of an ammonia / amine activator and heated to reflux, naturally cooled to room temperature, filtered to separate the solid and liquid, washed with deionized water until the pH value remains unchanged, and then placed in a drying oven for drying to obtain activated corn cob particles.

[0029] In this embodiment, ammonia / amine compounds are selected as activators. On the one hand, they can introduce active groups such as amino (-NH2) and hydroxyl (-OH) groups into the corncob and promote the breakage of cellulose macromolecules in the corncob to produce abundant pores. On the other hand, NH4 + Or amine small molecules can strip corn cob biochar by intercalation / de-intercalation, and finally obtain two-dimensional layered corn cob biochar with excellent adsorption performance, and finally optimize the pore structure, specific surface area and functional group type / density of corn cob biochar.

[0030] Optionally, the heating temperature during the heating reflux process is 60°C-100°C, the reflux time is 0.5h-5h, and the drying temperature is 60°C-110°C.

[0031] Different activators will result in different functional groups and chemical properties of the activated corncob particles, which will affect the microstructure and thermal stability of the low-temperature carbonized product. Optionally, the activator includes one or more of ammonia water, ethylenediamine, hydrazine hydrate or diethylenetriamine.

[0032] Furthermore, the concentration of the activator aqueous solution is 5 vol%-25 vol%, and the ratio of the mass of the corncob particles to the volume of the activator aqueous solution is 1:(10-50) g / mL.

[0033] (3) Carbonizing the activated corncob particles at low temperature until smokeless to obtain an amorphous carbon material.

[0034] Specifically, the activated corncob particles are placed in a porcelain crucible and subjected to low-temperature heat treatment with a universal electric furnace to obtain an amorphous carbon material. The role of low-temperature carbonization is to decompose the polymer structure in the activated corncob particles to release most of the non-carbon elements, retain the rigid carbon skeleton, and convert it into amorphous carbon. This amorphous carbon has high thermal stability, so that the subsequent high-temperature heat treatment process can be carried out in an air atmosphere, reducing the high requirements of high-temperature heat treatment on equipment and reaction conditions. Among them, the carbonization temperature has an important influence on the yield and adsorption performance of corncob biochar. On the one hand, the low temperature causes the polymer structure to be unable to decompose, and the porosity of the obtained corncob biochar is low. On the other hand, it is unable to form a rigid carbon skeleton and ashing occurs in the subsequent high-temperature heat treatment stage. Excessive temperature will cause the corncob particles to ashed during the low-temperature carbonization stage, and cause the structure of the corncob biochar to collapse, destroying its loose structure. Optionally, the low-temperature carbonization temperature is 250°C-350°C. The temperature of low-temperature carbonization will affect the porosity. Too low a carbonization temperature will lead to large losses in high-temperature heat treatment, while too high a carbonization temperature will destroy the loose structure.

[0035] (4) The amorphous carbon material is subjected to high temperature heat treatment, and after cooling, a two-dimensional layered corn cob biomass carbon adsorbent is obtained.

[0036] Specifically, the high-temperature heat treatment atmosphere is an air atmosphere, the heat treatment temperature is 500°C-700°C, the heat treatment time is 0.5h-3h, and the heating rate is 5°C / min-20°C / min.

[0037] Amorphous carbon belongs to transitional carbon with low crystallization degree. The role of high temperature heat treatment is to improve the graphitization crystallization degree of amorphous carbon. Due to the different low temperature carbonization temperatures, the obtained carbonization products have different crystal forms, and thus different thermal stability. The amorphous carbon obtained by low temperature carbonization at 250°C-350°C of the present invention is stable at the high temperature heat treatment temperature of 500°C-700°C of the present invention. Therefore, the high temperature heat treatment process can be carried out in an air atmosphere.

[0038] It should be noted that in the prior art, the activated corn cob particles are directly subjected to high-temperature heat treatment. Since the activated corn cob particles have high chemical activity and are easily reacted with oxygen under high temperature conditions, the high-temperature heat treatment in the prior art must be carried out under anaerobic conditions, which has high requirements on equipment and reaction conditions and low product purity.

[0039] The present invention first carbonizes the activated corncob particles at low temperature to convert them into amorphous carbon with higher thermal stability, thereby improving thermal stability and avoiding reaction with oxygen during high-temperature heat treatment, thereby being able to obtain biomass carbon materials with higher purity (i.e., high graphitization and crystallization degree) through heat treatment under oxygen conditions, thereby reducing the high requirements of high-temperature heat treatment on equipment and reaction conditions. The preparation process is simple to operate, has low requirements on equipment, does not generate other waste, and has the characteristics of low cost, low energy consumption and high efficiency, has good application and industrialization prospects, and is suitable for large-scale industrial production.

[0040] The corncob biomass charcoal adsorbent prepared by the preparation method of the two-dimensional layered corncob biomass charcoal adsorbent in this embodiment can be used to treat anionic organic dye wastewater. Specifically, the anionic organic dye is one or two of methyl orange and Congo red. Among them, the maximum adsorption amount of the two-dimensional layered corncob biomass charcoal adsorbent for the anionic methyl orange organic dye is higher than 1000 mg / g. Specific embodiment:

[0042] In the following examples, natural corn cobs were provided by farmers in Hebei Province; ammonia water, ethylenediamine, hydrazine hydrate and diethylenetriamine were purchased from Beijing Chemical Plant Co., Ltd. and were analytical grade with a purity greater than 99%; and methyl orange organic dye was analytical grade.

[0043] Example 1

[0044] The preparation method of a two-dimensional layered corncob biochar adsorbent comprises the following steps:

[0045] (1) cracking open an air-dried natural corn cob, taking the soft tissue in the middle, soaking it in deionized water, filtering it, washing it with water three times, drying it in a drying oven at 80° C., and then chopping it into pieces to obtain corn cob particles;

[0046] (2) Weigh 8 g of the corn cob particles into a 500 mL three-necked flask, add 225 mL of 5% ammonia water, stir to completely immerse the corn cob particles in the ammonia water, place the three-necked flask in a constant temperature water bath, heat and reflux at 70° C. for 2 h, cool naturally to room temperature, filter to separate the solid and liquid, wash the corn cob particles with water until the pH remains unchanged, and place in a drying oven to dry at 80° C. to obtain activated corn cob particles;

[0047] (3) The activated corn cob particles are placed in a crucible and carbonized at 300°C in a universal electric furnace until smokeless. The crucible is then covered with a lid and placed in a programmed temperature furnace. The heating rate is set to 10°C / min and heat treated at 600°C for 2h in an air atmosphere. After naturally cooling to room temperature, a two-dimensional layered corn cob biomass charcoal adsorbent is obtained.

[0048] Embodiment 2:

[0049] The preparation method of a two-dimensional layered corncob biochar adsorbent comprises the following steps:

[0050] (1) cracking open an air-dried natural corn cob, taking the soft tissue in the middle, soaking it in deionized water, filtering it, washing it with water three times, drying it in a drying oven at 60° C., and chopping it into pieces to obtain corn cob particles;

[0051] (2) Weigh 4 g of the corn cob particles in a 500 mL three-necked flask, add 200 mL of a 10% ethylenediamine aqueous solution, stir to completely immerse the corn cob particles in the ethylenediamine aqueous solution, place the three-necked flask in a constant temperature water bath, heat and reflux at 60° C. for 4 h, cool naturally to room temperature, filter to separate the solid and liquid, wash the corn cob particles with water until the pH remains unchanged, and dry them in a drying oven at 60° C. to obtain pretreated corn cob particles;

[0052] (3) The pretreated corn cob particles are placed in a crucible and carbonized at 350°C in a universal electric furnace until smokeless. The crucible is then covered with a lid and placed in a programmed temperature furnace. The heating rate is set to 5°C / min and heat treated at 500°C for 3 h in an air atmosphere. After naturally cooling to room temperature, a two-dimensional layered corn cob biomass charcoal adsorbent is obtained.

[0053] Embodiment 3:

[0054] The preparation method of a two-dimensional layered corncob biochar adsorbent comprises the following steps:

[0055] (1) cracking open an air-dried natural corn cob, taking the soft tissue part in the middle, soaking it in deionized water, filtering it, washing it with water three times, drying it in a drying oven at 100° C., and chopping it into pieces to obtain corn cob particles;

[0056] (2) Weigh 10 g of the corn cob particles in a 250 mL three-necked flask, add 100 mL of a 15% hydrazine hydrate aqueous solution, stir to completely immerse the corn cob particles in the hydrazine hydrate aqueous solution, place the three-necked flask in a constant temperature water bath, heat and reflux at 80° C. for 1 h, cool naturally to room temperature, filter to separate the solid and liquid, wash the corn cob particles with water until the pH remains unchanged, and dry them in a drying oven at 100° C. to obtain pretreated corn cob particles;

[0057] (3) The pretreated corn cob particles are placed in a crucible and carbonized at 250°C in a universal electric furnace until smokeless. The crucible is then covered with a lid and placed in a programmed temperature furnace. The heating rate is set to 20°C / min, and heat treated at 700°C in an air atmosphere for 0.5h. After naturally cooling to room temperature, a two-dimensional layered corn cob biomass charcoal adsorbent is obtained.

[0058] Embodiment 4:

[0059] The preparation method of a two-dimensional layered corncob biochar adsorbent comprises the following steps:

[0060] (1) cracking open an air-dried natural corn cob, taking the soft tissue part in the middle, soaking it in deionized water, filtering it, washing it with water three times, drying it in a drying oven at 70° C., and chopping it into pieces to obtain corn cob particles;

[0061] (2) Weigh 10 g of the corn cob particles in a 200 mL three-necked flask, add 100 mL of a 10% diethylenetriamine aqueous solution, stir to completely immerse the corn cob particles in the diethylenetriamine aqueous solution, place the three-necked flask in a constant temperature water bath, heat and reflux at 70° C. for 1.5 h, cool naturally to room temperature, filter to separate the solid and liquid, wash the corn cob particles with water until the pH remains unchanged, and place in a drying oven to dry at 70° C. to obtain pretreated corn cob particles;

[0062] (3) The pretreated corn cob particles are placed in a crucible and carbonized at 300°C in a universal electric furnace until smokeless. The crucible is then covered with a lid and placed in a programmed temperature furnace. The heating rate is set to 10°C / min and heat treated at 600°C for 1 h in an air atmosphere. After naturally cooling to room temperature, a two-dimensional layered corn cob biomass charcoal adsorbent is obtained.

[0063] Comparative Example 1:

[0064] Compared with Example 1, in step (2) of Comparative Example 1, the corncob particles were not activated by aqueous solution of ammonia / amine activator, but were directly subjected to low-temperature carbonization and high-temperature heat treatment. The other steps were the same as those of Example 1.

[0065] Comparative Example 2:

[0066] Compared with Example 1, Comparative Example 2 lacks the low-temperature carbonization process of step (3). The other steps are the same as Example 1. Comparative Example 2 does not have a low-temperature carbonization process. The high-temperature heat treatment is carried out in an air atmosphere, which will cause the carbon in the corn cob particles to react with oxygen and become carbon dioxide gas and ash to obtain white ash, which is mainly oxides of impurities other than carbon, such as calcium oxide, silicon oxide, etc. Therefore, the lack of a low-temperature carbonization process makes it impossible to directly obtain biomass carbon by high-temperature heat treatment in an air atmosphere.

[0067] Comparative Example 3:

[0068] Compared with Example 1, the temperature of the low-temperature carbonization process in step (3) of Comparative Example 3 is too low, which is 200° C. The other steps are the same as those in Example 1.

[0069] Comparative Example 4:

[0070] Compared with Example 1, the temperature of the low-temperature carbonization process in step (3) of Comparative Example 4 is too high, which is 400° C. The other steps are the same as those in Example 1.

[0071] Test Example 1

[0072] An adsorption experiment was conducted on the two-dimensional layered corncob biomass charcoal adsorbents prepared in Examples 1 to 4 and Comparative Examples 1, 3 to 4. The specific steps are as follows:

[0073] (1) Place 40 mL of 300 mg / L methyl orange dye aqueous solution in a 100 mL beaker and wrap the beaker with aluminum foil to achieve the effect under dark conditions.

[0074] (2) Accurately weigh 5 mg of two-dimensional layered corn cob biochar adsorbent, add it to the methyl orange dye aqueous solution in step (1), ultrasonically disperse for 2 min until a uniform suspension is formed, put in a magnetic bar, set the speed to 800 rpm, and stir and adsorb on a magnetic stirrer at room temperature (20-40°C) for 1.5 h.

[0075] The adsorption results are shown in Table 1.

[0076] Table 1: Adsorption results of Examples 1-4, Comparative Examples 1, 3, and 4

[0077] Adsorption capacity mg / g Example 1 1050 Example 2 844 Example 3 824 Example 4 890 Comparative Example 1 203 Comparative Example 3 302 Comparative Example 4 590

[0078] It can be seen that the adsorption capacity of the two-dimensional layered corncob biomass charcoal adsorbent prepared by the present invention is higher than 800 mg / g, and the adsorption effect is significantly increased compared with each comparative example.

[0079] Test Example 2

[0080] Corresponding detection and analysis were performed on the two-dimensional layered corncob biomass carbon adsorbents prepared in Example 1 and Comparative Examples 1-4:

[0081] Figure 1 This is an X-ray diffraction spectrum of a two-dimensional layered corncob biochar adsorbent. It can be seen from the figure that the diffraction peak at 2θ≈23.5° matches the standard spectrum of carbon, and there are no diffraction peaks of other impurities, indicating that the product of the present invention has high crystal purity. In addition, the diffraction peak at 2θ≈8.5° shows that the corncob biochar has a layered structure.

[0082] Figure 2This is a scanning electron microscope photo of a two-dimensional layered corncob biochar adsorbent. It can be seen from the figure that the corncob biochar is actually an ultra-thin nanosheet with wrinkles, and the lateral size is greater than 30μm.

[0083] Figure 3 The product photos of Example 1 and Comparative Examples 1-4 are shown in the figure. It can be seen from the figure that the products obtained in Example 1 and Comparative Example 1 are all black corn cob biomass charcoal, while the product obtained in Comparative Example 2 is almost entirely white ash, and the corn cob biomass charcoal obtained in Comparative Examples 3 and 4 contains a small amount of white ash. In addition, compared with Comparative Example 1, the corn cob biomass charcoal obtained in Example 1 has a larger volume and a looser structure.

[0084] Figure 4 The figure is a diagram of the adsorption effect of the two-dimensional layered corncob biomass charcoal adsorbent on methyl orange dye. It can be seen from the figure that the two-dimensional layered corncob biomass charcoal adsorbent exhibits a rapid and efficient adsorption effect on anionic methyl orange organic dyes. The adsorption effect of the two-dimensional layered corncob biomass charcoal obtained in Example 1 on methyl orange organic dyes is significantly higher than that of the products obtained in Comparative Examples 1, 3 and 4. The adsorption amount can reach 1050 mg / g when stirred and adsorbed for 90 minutes at room temperature.

[0085] Test Example 3

[0086] The masses of the final products of Example 1, Comparative Example 3 and Comparative Example 4 were weighed respectively, and the results are shown in Table 2.

[0087] Table 2: Weight of the final product of Example 1, Comparative Example 3 and Comparative Example 4

[0088] Weight of final product (in g) Example 1 0.9356 Comparative Example 3 0.2841 Comparative Example 4 0.5917

[0089] It can be seen that when the low-temperature carbonization temperature of Comparative Example 3 is too low, or when the low-temperature carbonization temperature of Comparative Example 4 is too high, the quality of the final product obtained is lower than that of Example 1, and the adsorption performance of Comparative Examples 3 and 4 is also lower than that of Example 1, because the low-temperature carbonization temperature will affect the porosity, and too low carbonization temperature will lead to large losses in high-temperature heat treatment, and too high carbonization temperature will lead to the destruction of the loose structure and also affect the adsorption amount.

[0090] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a two-dimensional layered corncob biochar adsorbent, characterized in that: The steps include: (1) obtaining soft tissue at the center of a natural corn cob, soaking, filtering, washing, drying, and chopping the soft tissue to obtain corn cob particles; (2) soaking the corncob particles in an aqueous solution of an ammonia / amine activator and heating under reflux to obtain activated corncob particles; (3) carbonizing the activated corncob particles at low temperature to obtain an amorphous carbon material; (4) The amorphous carbon material is subjected to high temperature heat treatment, and after cooling, a two-dimensional layered corn cob biomass carbon adsorbent is obtained.

2. The method for preparing the two-dimensional layered corncob biochar adsorbent according to claim 1, characterized in that: The temperature of the low-temperature carbonization in step (3) is 250°C-350°C.

3. The method for preparing the two-dimensional layered corncob biochar adsorbent according to claim 1, characterized in that: The ammonia / amine activator in step (2) includes one or more of ammonia water, ethylenediamine, hydrazine hydrate and diethylenetriamine.

4. The method for preparing the two-dimensional layered corncob biochar adsorbent according to claim 3, characterized in that: The concentration of the aqueous solution of the ammonia / amine activator in step (2) is 5 vol%-25 vol%, and the ratio of the mass of the corn cob particles to the volume of the aqueous solution of the ammonia / amine activator is 1:(10-50) g / mL.

5. The method for preparing the two-dimensional layered corncob biochar adsorbent according to claim 3 or 4, characterized in that: The heating reflux temperature in step (2) is 60°C-100°C, and the reflux time is 0.5h-5h.

6. The method for preparing the two-dimensional layered corncob biochar adsorbent according to claim 1, characterized in that: The drying temperature in step (1) is 60°C-110°C.

7. The method for preparing the two-dimensional layered corncob biochar adsorbent according to claim 1, characterized in that: The atmosphere of the high-temperature heat treatment in step (4) is an air atmosphere, the heat treatment temperature is 500°C-700°C, the heat treatment time is 0.5h-3h, and the heating rate is 5°C / min-20°C / min.

8. A two-dimensional layered corncob biochar adsorbent, characterized in that: The two-dimensional layered corncob biomass charcoal adsorbent is prepared by the preparation method of any one of claims 1 to 7.

9. The two-dimensional layered corncob biochar adsorbent according to claim 8, characterized in that: The two-dimensional layered corncob biomass carbon adsorbent is used in treating anionic organic dye wastewater.

10. The two-dimensional layered corncob biochar adsorbent according to claim 9, characterized in that: The anionic organic dye is one or both of methyl orange and Congo red.

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