A phosphorus-doped rice straw modified biochar material, its preparation method and application

Abstract

The present invention discloses a phosphorus-doped modified biochar material, its preparation method and application. The raw materials of this material include potassium dihydrogen phosphate and rice straw, and the mass ratio is 1:(100-800). Its preparation method includes the following steps: (1) Wash and dry the rice straw, and crush it into powder; (2) Add potassium dihydrogen phosphate particles into ultrapure water to make a potassium dihydrogen phosphate solution; (3) Add the rice straw powder into the potassium dihydrogen phosphate solution, stir and dry to obtain the dried phosphorus-doped rice straw material; (4) Carbonize the dried phosphorus-doped rice straw material to obtain a phosphorus-doped rice straw carbonized material; (5) Wash the phosphorus-doped rice straw carbonized material to remove ash, dry and crush it to obtain the modified biochar material. By using the rich pore distribution, high specific surface area and abundant surface functional groups of this material, the purpose of removing acetochlor, butachlor and metolachlor in environmental water bodies is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of modified biochar materials, and in particular to a phosphorus-doped rice straw modified biochar material and a preparation method and application thereof. Background Art

[0002] Biochar refers to a solid material with high carbon content and large specific surface area produced by thermal cracking of biomass raw materials in an oxygen-deficient or anaerobic environment and under certain temperature conditions (<700°C). In recent years, the use of biochar prepared from biomass materials (such as wood, animal manure, and agricultural waste gas) for environmental management has gradually been recognized. In addition, a large number of studies have shown that biochar can be used as an economical and effective adsorbent for pollutants in polluted environmental matrices, adsorbing organic pollutants and heavy metals in water bodies, sediments, and soils, and controlling their environmental fate and biological toxicity. It can also be used to adsorb eutrophic elements and control algae outbreaks.

[0003] Rice straw is a cheap industrial and agricultural biomass waste that is easy to obtain in large quantities. Except for a small amount of rice straw used as feed for herbivorous animals, fertilizer for crops, and raw material for biogas fermentation, a large amount of rice straw is used as fuel or waste, causing great waste of resources and environmental pollution.

[0004] Some scholars have used rice straw or rice straw biomass as adsorption materials for wastewater treatment. However, the physical and chemical properties of the surface of the fired biochar (e.g., carbon defect level and functional groups) are limited by the non-stoichiometric properties of the original biomass, resulting in a single selectivity for pollutant adsorption, a small adsorption capacity, and a general adsorption effect, which has led to few actual promotion and application. Therefore, the element doping of biochar has attracted the attention of researchers. Studies have found that doping with heteroatoms such as nitrogen, sulfur or phosphorus is an effective way to improve the functionality of biochar.

[0005] Potassium dihydrogen phosphate is rich in phosphorus, stable in air, and soluble in water. It is a new and ideal biochar modification material. Potassium dihydrogen phosphate is widely used in industry, often used as a buffer, culture agent, bacterial culture agent, flavoring agent for synthetic sake, culture agent, enhancer, bulking agent, and fermentation aid for brewing yeast. In agriculture, it is a high-concentration phosphorus and potassium compound fertilizer with excellent effects such as significantly increasing production and income and optimizing quality.

[0006] At the same time, acetochlor, butachlor and isopropylamine are three typical amide herbicides that can control annual grass weeds and some broadleaf weeds, and are widely used in a variety of crops such as corn, soybeans, cotton and rice. Due to the advantages of this type of agent such as a wide spectrum of weed control, outstanding effect, low price and convenient application, the area of application in production has gradually expanded. However, the long-term and large-scale use of amide herbicides is bound to cause serious pollution to the ecological environment.

[0007] Acetochlor is highly hydrophobic, has weak volatility, and is prone to migration. After being applied to the soil, it can enter surface water and groundwater through diffusion, causing pollution to environmental media such as soil and water bodies. It is reported that acetochlor residues are often detected in groundwater, and its concentration often exceeds the EU drinking water standard of 0.1 μg / L. It is listed as a class B2 carcinogen and a suspected endocrine disruptor by the US Environmental Protection Agency.

[0008] Although butachlor has extremely poor mobility in the soil, it is very easy to bioaccumulate in the aquatic ecosystem. Therefore, it can pose a potential threat to the ecosystem and even human health through the food chain. It is highly toxic to the aquatic ecosystem, especially the freshwater aquatic ecosystem. In the terrestrial ecosystem, butachlor is not only toxic to earthworms but also has an adverse impact on soil microbial activity and enzyme activity.

[0009] Due to the low vapor pressure, high water solubility, and relatively low soil adsorption coefficient of metolachlor, it is easy to pollute surface water and shallow groundwater through rainfall and infiltration. Different concentrations of metolachlor have been detected in the seawater of Cape Town, South Africa, the Huangpu River Basin in China, the Dniester River in Ukraine, and the town of Letsitele in South Africa. Although the concentration of metolachlor in the aquatic ecosystem is usually far lower than the established lethal level of aquatic organisms, it may still have sub-lethal harmful effects on aquatic organisms. Some studies have shown that sub-lethal exposure to metolachlor can change the sensory abilities of crayfish to locate food and respond to alarm signals.

[0010] Therefore, it is particularly important to develop a remediation material with significant remediation effect, simple preparation process, and low cost to remove residual acetochlor, butachlor, and metolachlor in the environment. Summary of the Invention

[0011] In view of this, the present invention provides a phosphorus-doped modified rice straw biochar material that is environmentally friendly to agriculture, increases soil nutrients, and has excellent adsorption performance, as well as its preparation method and application. The present invention improves the properties of biochar through phosphorus doping and optimizes the ratio and preparation parameters to endow it with novel structures and surface properties, so as to improve its adsorption effect and environmental benefits.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] A phosphorus-doped rice straw modified biochar material, the raw materials of which include: potassium dihydrogen phosphate and rice straw, the mass ratio of the potassium dihydrogen phosphate to the rice straw is 1:(100 - 800), and the phosphorus-doped rice straw modified biochar material is obtained by carbonizing the powder mixture of the potassium dihydrogen phosphate and the rice straw, and the carbonization temperature is preferably 500 - 800 °C.

[0014] Beneficial effects of adopting the above technical solution: By impregnating rice straw raw materials in a potassium dihydrogen phosphate solution, more micropores and mesopores are generated in the biochar for physical adsorption, and the specific surface area of the material is increased, generating more characteristic surface functional groups for chemical adsorption, thereby improving the performance of the original biochar. The doping of phosphorus elements changes the properties of the biochar, improves the adsorption effect of a single adsorbent, and reduces the repair cost. By optimizing parameters such as the carbonization temperature and doping ratio, the adsorption performance of the phosphorus-doped biochar modified biochar material is improved.

[0015] Preferably, in the above phosphorus-doped biochar modified biochar material, the mass ratio of potassium dihydrogen phosphate to the rice straw is 1:400.

[0016] The present invention also discloses a preparation method of the above phosphorus-doped biochar modified biochar material, which includes the following steps:

[0017] (1) Pretreatment of rice straw: Wash the surface of the rice straw with clear water to remove various adhered impurities, dry it in an oven, and then crush it into powder with a high-speed crusher;

[0018] (2) Preparation of potassium dihydrogen phosphate solution: Add potassium dihydrogen phosphate particles to ultrapure water and stir evenly to make a potassium dihydrogen phosphate solution;

[0019] (3) Add the rice straw powder obtained in step (1) to the potassium dihydrogen phosphate solution prepared in step (2), stir and dry to obtain a dried phosphorus-doped rice straw material;

[0020] (4) Put the dried phosphorus-doped rice straw material obtained in step (3) into a box furnace for carbonization to obtain a phosphorus-doped rice straw carbonized material;

[0021] (5) Wash the phosphorus-doped rice straw carbonized material prepared in step (4) several times with ultrapure water to remove ash until the pH of the filtrate is about 7 (such as pH 6.8 - 7.2, 7.0), then dry and crush it to obtain the above phosphorus-doped rice straw modified biochar material.

[0022] Preferably, in the preparation method of the above phosphorus-doped rice straw modified biochar material, the drying temperature in step (1) is 60 - 90 °C, the time is 6 - 12 h; and it is sieved through a 10 - 18 mesh sieve;

[0023] More preferably, the drying temperature in step (1) is 70 °C, the time is 6 h; and it is sieved through an 18 mesh sieve.

[0024] Preferably, in the preparation method of the above phosphorus-doped rice straw modified biochar material, the stirring and drying in step (3) are specifically: Stir with a magnetic stirrer for 6 h, and then put it into an oven at 60 - 90 °C and bake for 24 - 48 h;

[0025] Preferably, in step (3), the stirring and drying are specifically as follows: stirring with a magnetic stirrer for 6 h, and then drying in an oven at 70 °C for 24 h.

[0026] Preferably, in the preparation method of the above-mentioned phosphorus-doped rice straw modified biochar material, in step (4), the carbonization temperature is 500-800 °C, and it is heated from room temperature (18-26 °C, such as 25 °C) to the carbonization temperature at a heating rate of 5 °C / min for carbonization, and the carbonization time is 1 h.

[0027] Preferably, in the preparation method of the above-mentioned phosphorus-doped rice straw modified biochar material, in step (5), the drying and crushing are specifically as follows: drying in an oven at 60-90 °C for 1-2 h, and then crushing through a high-speed crusher and screening through a 80-100 mesh sieve;

[0028] Preferably, in step (5), the drying and crushing are specifically as follows: drying in an oven at 70 °C for 2 h, and then crushing through a high-speed crusher and screening through an 80 mesh sieve.

[0029] The beneficial effects of adopting the above technical solution: This method has the characteristics of simple operation, short time consumption, high safety, and no environmental pollution.

[0030] The present invention also discloses the application of the above-mentioned phosphorus-doped rice straw modified biochar material in removing acetochlor, butachlor, and metolachlor in the environment.

[0031] Phosphorus-doped biochar has strong adsorption ability, contains abundant oxygen-containing functional groups and a large specific surface area on the surface, and can combine with acetochlor, butachlor, and metolachlor through pore filling, hydrogen bonding, π-π electron donor-acceptor interaction, and hydrophobic interaction.

[0032] It can be seen from the above technical solution that, compared with the prior art, the beneficial effects of the present invention are: The phosphorus-doped rice straw modified biochar has higher adsorption ability for acetochlor, butachlor, and metolachlor than the unmodified rice straw biochar, and can be widely applied in the field of pollution remediation. Potassium dihydrogen phosphate and rice straw materials are cheap and easily available, environmentally friendly and pollution-free, and improve economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 SEM images of rice straw biochar (a) prepared in Comparative Example 1 and phosphorus-doped rice straw modified biochar (b) prepared in Example 1 of the present invention;

[0034] Figure 2 EDS-Mapping images of rice straw biochar (a) prepared in Comparative Example 1 and phosphorus-doped rice straw modified biochar (b) prepared in Example 1 of the present invention;

[0035] Figure 3 N2 adsorption - desorption curves (a) and pore size distribution diagrams (b) of the rice straw biochar prepared in Comparative Example 1 and the phosphorus - doped rice straw modified biochar prepared in Example 1 of the present invention;

[0036] Figure 4 Adsorption performance diagrams of the phosphorus - doped rice straw modified biochar materials prepared with different amounts of potassium dihydrogen phosphate added and different pyrolysis temperatures;

[0037] Figure 5 Adsorption kinetic schematic diagrams of acetochlor, butachlor and metolachlor by the rice straw biochar prepared in Comparative Example 1 and the phosphorus - doped rice straw modified biochar prepared in Example 1 of the present invention. Detailed implementation manners

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Evaluation method for the adsorption performance of the biochar adsorbent: It is carried out in a 50 - mL sample bottle. 40 mL of 5 mg / L acetochlor, butachlor and metolachlor (containing 0.01 mol / L CaCl2) are added to the sample bottle, and 8 mg of the prepared biochar material is added. The bottle is sealed and placed in a shaker at 180 rpm and 25 °C. Samples are taken after 48 h, filtered through a 0.22 - μm filter membrane, and the concentration is measured by an ultra - high - performance liquid chromatography - tandem mass spectrometry instrument. The removal rate is calculated by the formula:

[0040]

[0041] where C0 is the initial concentration of the target substance, and C is the concentration of the target substance solution measured by timed sampling.

[0042] Example 1: Preparation of the phosphorus - doped rice straw modified biochar material and verification of its adsorption effect

[0043] (1) Wash the surface of the rice straw with clean water to remove various adhered impurities, dry it in an oven at 70 °C for 6 h, and crush the rice straw with a high - speed crusher and pass it through a 18 - mesh sieve;

[0044] (2) Weigh 0.025 g of potassium dihydrogen phosphate particles, add them to 200 mL of ultrapure water, and stir evenly to prepare a potassium dihydrogen phosphate solution;

[0045] (3) Weigh 10 g of the rice straw powder in step (1) and add it to the potassium dihydrogen phosphate solution in step (2), stir with a magnetic stirrer for 6 h, and then place it in an oven at 70 °C and dry for 24 h;

[0046] (4) Put the dried phosphorus-doped rice straw material in step (3) into a box furnace for high-temperature pyrolysis. The carbonization temperature is 800 °C. Heat from room temperature (25 °C) to the carbonization temperature at a heating rate of 5 °C / min for carbonization. The carbonization time is 1 h to obtain the phosphorus-doped rice straw carbonized material;

[0047] (5) Wash the phosphorus-doped rice straw carbonized material prepared in step (4) several times with ultrapure water to remove ash until the pH of the filtrate reaches 6.8 - 7.2. Then dry it in an oven at 70 °C for 2 h and crush it through an 80-mesh sieve with a high-speed grinder to obtain the phosphorus-doped rice straw modified biochar material.

[0048] Take 8 mg of the phosphorus-doped rice straw modified biochar material for the adsorption experiments of acetochlor, butachlor, and metolachlor in a sample bottle. The removal rates of the adsorbent for acetochlor, butachlor, and metolachlor within 48 h are measured to be 93.67%, 88.25%, and 96.15% respectively.

[0049] Example 2

[0050] Replace the 0.025 g potassium dihydrogen phosphate particles in step (2) of Example 1 with 0.0125 g potassium dihydrogen phosphate particles, and other steps are the same as in Example 1.

[0051] Take 8 mg of the phosphorus-doped rice straw modified biochar material for the adsorption experiments of acetochlor, butachlor, and metolachlor in a sample bottle. The removal rates of the adsorbent for acetochlor, butachlor, and metolachlor within 48 h are measured to be 80.41%, 72.54%, and 83.78% respectively.

[0052] Example 3

[0053] Replace the 0.025 g potassium dihydrogen phosphate particles in step (2) of Example 1 with 0.05 g potassium dihydrogen phosphate particles, and other steps are the same as in Example 1.

[0054] Take 8 mg of the phosphorus-doped rice straw modified biochar material for the adsorption experiments of acetochlor, butachlor, and metolachlor in a sample bottle. The removal rates of the adsorbent for acetochlor, butachlor, and metolachlor within 48 h are measured to be 82.15%, 69.27%, and 79.90% respectively.

[0055] Example 4

[0056] Replace the 0.025 g potassium dihydrogen phosphate particles in step (2) of Example 1 with 0.1 g potassium dihydrogen phosphate particles, and other steps are the same as in Example 1.

[0057] 8 mg of phosphorus-doped rice straw modified biochar material was taken in a sample bottle for the adsorption experiments of acetochlor, butachlor and metolachlor. The removal rates of the adsorbent for acetochlor, butachlor and metolachlor within 48 h were measured to be 78.86%, 61.33% and 76.24% respectively.

[0058] Example 5

[0059] The carbonization temperature in step (4) of Example 1 was changed from 800 °C to 500 °C, and other steps were the same as those in Example 1.

[0060] 8 mg of phosphorus-doped rice straw modified biochar material was taken in a sample bottle for the adsorption experiments of acetochlor, butachlor and metolachlor. The removal rates of the adsorbent for acetochlor, butachlor and metolachlor within 48 h were measured to be 57.34%, 50.41% and 63.91% respectively.

[0061] Example 6

[0062] The carbonization temperature in step (4) of Example 1 was changed from 800 °C to 600 °C, and other steps were the same as those in Example 1.

[0063] 8 mg of phosphorus-doped rice straw modified biochar material was taken in a sample bottle for the adsorption experiments of acetochlor, butachlor and metolachlor. The removal rates of the adsorbent for acetochlor, butachlor and metolachlor within 48 h were measured to be 72.18%, 65.93% and 82.84% respectively.

[0064] Example 7

[0065] The carbonization temperature in step (4) of Example 1 was changed from 800 °C to 700 °C, and other steps were the same as those in Example 1.

[0066] 8 mg of phosphorus-doped rice straw modified biochar material was taken in a sample bottle for the adsorption experiments of acetochlor, butachlor and metolachlor. The removal rates of the adsorbent for acetochlor, butachlor and metolachlor within 48 h were measured to be 84.82%, 76.81% and 91.17% respectively.

[0067] Example 8

[0068] (1) The rice straw was washed with clean water to remove various impurities adhering to the surface, dried in an oven at 60 °C for 9 h, and crushed by a high-speed crusher through a 10-mesh sieve.

[0069] (2) 0.025 g of potassium dihydrogen phosphate particles were weighed and added to 200 mL of ultrapure water and stirred evenly to prepare a potassium dihydrogen phosphate solution.

[0070] (3) Weigh 10 g of the rice straw powder in step (1) and add it to the solution in step (2). Stir with a magnetic stirrer for 2 h, and then place it in an oven at 60 °C for 32 h to obtain the dried phosphorus-doped rice straw material.

[0071] (4) Place the dried phosphorus-doped rice straw material in step (3) into a box furnace for high-temperature pyrolysis. The carbonization temperature is 800 °C. Heat from room temperature (25 °C) to the carbonization temperature at a heating rate of 5 °C / min for carbonization. The carbonization time is 1 h to obtain the phosphorus-doped rice straw carbonized material.

[0072] (5) Wash the phosphorus-doped rice straw carbonized material prepared in step (4) several times with ultrapure water to remove ash until the pH of the filtrate is around 7 (6.8 - 7.2). Then dry it in an oven at 60 °C for 1 h and pulverize it through a 90-mesh sieve with a high-speed pulverizer to obtain the phosphorus-doped rice straw modified biochar material.

[0073] Take 8 mg of the phosphorus-doped rice straw modified biochar material for the adsorption experiment of acetochlor, butachlor, and metolachlor in a sample bottle. The removal rates of acetochlor, butachlor, and metolachlor by this adsorbent within 48 h are 84.33%, 74.67%, and 90.75%, respectively.

[0074] Example 9

[0075] (1) Wash the surface of the rice straw with clean water to remove various adhered impurities, and dry it in an oven at 90 °C for 12 h. Pulverize the rice straw through a 14-mesh sieve with a high-speed pulverizer.

[0076] (2) Weigh 0.025 g of potassium dihydrogen phosphate particles and add them to 200 mL of ultrapure water, stir evenly to prepare a potassium dihydrogen phosphate solution.

[0077] (3) Weigh 10 g of the rice straw powder in step (1) and add it to the solution in step (2). Stir with a magnetic stirrer for 2 h, and then place it in an oven at 90 °C for 48 h to obtain the dried phosphorus-doped rice straw material.

[0078] (4) Place the dried phosphorus-doped rice straw material in step (3) into a box furnace for high-temperature pyrolysis. The carbonization temperature is 800 °C. Heat from room temperature (25 °C) to the carbonization temperature at a heating rate of 5 °C / min for carbonization. The carbonization time is 1 h to obtain the phosphorus-doped rice straw carbonized material.

[0079] (5) Wash the phosphorus-doped rice straw carbonized material prepared in step (4) several times with ultrapure water to remove ash until the pH of the filtrate is 7.0. Then dry it in an oven at 90 °C for 2 h and pulverize it through a 100-mesh sieve with a high-speed pulverizer to obtain the phosphorus-doped rice straw modified biochar material.

[0080] 8 mg of phosphorus-doped rice straw modified biochar material was taken in a sample bottle for the adsorption experiments of acetochlor, butachlor, and metolachlor. The removal rates of acetochlor, butachlor, and metolachlor by this adsorbent within 48 h were 78.26%, 73.19%, and 84.36%, respectively.

[0081] Comparative Example 1

[0082] (1) The rice straw was washed with clear water to remove various impurities adhering to its surface, dried in an oven at a temperature of 70 °C for 6 h, and then pulverized by a high-speed pulverizer and passed through a 18-mesh sieve.

[0083] (2) 10 g of the rice straw powder obtained in step (1) was added to 200 mL of ultrapure water, stirred with a magnetic stirrer for 2 h, and then placed in an oven at 70 °C for 24 h.

[0084] (3) The dried rice straw material in (2) was placed in a box furnace for high-temperature pyrolysis. The carbonization temperature was 800 °C, the heating rate was 5 °C / min, and the carbonization time was 1 h.

[0085] (4) The carbon material prepared in (3) was washed several times with ultrapure water to remove ash until the pH of the filtrate was about 7. Subsequently, it was dried in an oven at 70 °C for 2 h and then pulverized by a high-speed pulverizer and passed through an 80-mesh sieve to obtain the rice straw biochar material.

[0086] Figure 1 SEM images of the rice straw biochar (a) prepared in Comparative Example 1 and the phosphorus-doped rice straw modified biochar (b) prepared in Example 1 of the present invention. It can be Figure 1 seen that the surface of the rice straw biochar has a porous structure. It can be seen from Figure (b) that the phosphorus-doped rice straw biochar has richer pores and larger pore sizes.

[0087] Figure 2 EDS-Mapping images of the rice straw biochar (a) prepared in Comparative Example 1 and the phosphorus-doped rice straw modified biochar (b) prepared in Example 1 of the present invention. It can be Figure 2 seen that the phosphorus element content of the phosphorus-doped rice straw modified biochar has increased significantly compared with that of the rice straw biochar.

[0088] Figure 3 N2 adsorption-desorption curves (a) and pore size distribution diagrams (b) of the rice straw biochar prepared in Comparative Example 1 and the phosphorus-doped rice straw modified biochar prepared in Example 1 of the present invention. It can be Figure 3 seen that mesopores (2 - 50 nm) are the main pore structures of both biochars.

[0089] The results of Examples 1-7 above show that different carbonization temperatures and different addition amounts of potassium dihydrogen phosphate have significant effects on the adsorption performance of phosphorus-doped rice straw modified biochar materials. The effect of carbonization temperature is particularly significant. When the carbonization temperature is 800 °C, it is significantly better than 500 °C. Below 500 °C, the adsorption performance is severely affected. When the mass ratio of potassium dihydrogen phosphate to rice straw is between 1:(100-800), the adsorption performance is better. The results are as Figure 4 shown: In the method of Example 1, the modified rice straw biochar material prepared with a mass ratio of potassium dihydrogen phosphate to rice straw of 1:400 and pyrolysis conditions at 800 °C has the highest adsorption effect on acetochlor, butachlor, and metolachlor, and is significantly better than Examples 2-7.

[0090] The results of Examples 1, 8, and 9 show that the pre-treatment drying temperature of rice straw in step (1) and the drying temperature in step (5) also have significant effects on the modified rice straw biochar material. The optimal temperature is 70 °C. When the temperature is too high or too low, the adsorption performance of the modified rice straw biochar material will be affected. As described in Example 9, when the temperature is 90 °C, the adsorption performance is significantly different from that of Example 1. Above 90 °C or below 60 °C will significantly affect the adsorption performance.

[0091] The adsorption kinetics study of the phosphorus-doped rice straw modified biochar adsorbent prepared in the present invention was carried out in a 50 mL sample bottle. 40 mL of 5 mg / L acetochlor, butachlor, and metolachlor (containing 0.01 mol / L CaCl2) was added to the sample bottle, and the prepared rice straw biochar material was added. The bottle was sealed and placed in a shaker at 180 rpm and 25 °C. Samples were taken at 0, 0.25, 0.5, 1, 2, 4, 6, 9, 12, 24, and 48 h respectively. After filtration through a 0.22 μm filter membrane, the concentration was measured by an ultra-high performance liquid chromatography-tandem mass spectrometry instrument, and the adsorption amount (mg / g) was calculated by the formula:

[0092]

[0093] where C i is the initial concentration of the target substance, C t is the concentration of the target substance solution measured by timed sampling, V is the volume of the suspension, and m is the mass of the biochar.

[0094] Figure 5 is the adsorption kinetics diagram of the rice straw biochar prepared in Comparative Example 1 and the phosphorus-doped rice straw modified biochar prepared in Example 1 of the present invention for acetochlor, butachlor, and metolachlor. From Figure 5It can be seen that: for the rice straw biochar (BC) prepared in Comparative Example 1 and the phosphorus-doped rice straw modified biochar (PBC) prepared in Example 1, the removal of acetochlor, butachlor, and metolachlor increased rapidly within the first two hours. The adsorption amount of metolachlor was higher than that of acetochlor and butachlor, and the adsorption amount of the phosphorus-doped rice straw modified biochar (PBC) prepared in Example 1 was significantly higher than that of the rice straw biochar (BC) prepared in Comparative Example 1.

[0095] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same and similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0096] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A phosphorus-doped rice straw modified biochar material for removing acetochlor, butachlor and / or metolachlor in the environment, characterized in that, Its raw materials include rice straw and potassium dihydrogen phosphate. The mass ratio of potassium dihydrogen phosphate to rice straw is 1:

400. The phosphorus-doped rice straw modified biochar material is obtained by carbonizing the powder mixture of potassium dihydrogen phosphate and rice straw. The carbonization temperature is 800 °C. The preparation method of the phosphorus-doped rice straw modified biochar material includes the following steps: (1) Pretreatment of rice straw: Wash the rice straw and then dry it, and then crush it to obtain rice straw powder. The drying temperature is 60-90 °C and the time is 6-12 h. Crush it through a 10-18 mesh sieve; (2) Pretreatment of potassium dihydrogen phosphate: Add potassium dihydrogen phosphate particles to ultrapure water and stir evenly to make a potassium dihydrogen phosphate solution; (3) Add the rice straw powder obtained in step (1) to the potassium dihydrogen phosphate solution prepared in step (2), stir and dry to obtain the dried phosphorus-doped rice straw material. Stirring and drying specifically are: Stir with a magnetic stirrer for 6 h, and then put it into an oven at 60-90 °C and bake for 24-48 h; (4) Put the dried phosphorus-doped rice straw material obtained in step (3) into a box furnace for carbonization to obtain a phosphorus-doped rice straw carbonized material. The carbonization temperature is 800 °C. Heat it from room temperature to the carbonization temperature at a rate of 5 °C / min and then carry out carbonization. The carbonization time is 1 hour; (5) Wash the phosphorus-doped rice straw carbonized material prepared in step (4) several times with ultrapure water to remove ash until the pH of the filtrate reaches 6.8-7.2, and then dry and crush it to obtain the phosphorus-doped rice straw modified biochar material. The mass ratio of potassium dihydrogen phosphate to the added rice straw powder is 1:

400. Drying and crushing specifically are: Dry it in an oven at 60-90 °C for 1-2 h and then crush it through an 80-100 mesh sieve with a high-speed crusher.

2. The preparation method of the phosphorus-doped rice straw modified biochar material according to claim 1, characterized in that, It includes the following steps: (1) Pretreatment of rice straw: Wash the rice straw and then dry it, and then crush it to obtain rice straw powder. The drying temperature is 60-90 °C and the time is 6-12 h. Crush it through a 10-18 mesh sieve; (2) Pretreatment of potassium dihydrogen phosphate: Add potassium dihydrogen phosphate particles to ultrapure water and stir evenly to make a potassium dihydrogen phosphate solution; (3) Add the rice straw powder obtained in step (1) to the potassium dihydrogen phosphate solution prepared in step (2), stir and dry to obtain the dried phosphorus-doped rice straw material. Stirring and drying specifically are: Stir with a magnetic stirrer for 6 h, and then put it into an oven at 60-90 °C and bake for 24-48 h; (4) Put the dried phosphorus-doped rice straw material obtained in step (3) into a box furnace for carbonization to obtain a phosphorus-doped rice straw carbonized material. The carbonization temperature is 800 °C. Heat it from room temperature to the carbonization temperature at a rate of 5 °C / min and then carry out carbonization. The carbonization time is 1 hour; (5) Wash the phosphorus-doped rice straw carbonized material prepared in step (4) several times with ultrapure water to remove ash until the pH of the filtrate reaches 6.8 - 7.2, and then dry and crush it to obtain the phosphorus-doped rice straw modified biochar material; the mass ratio of potassium dihydrogen phosphate to the added rice straw powder is 1:400; the drying and crushing are specifically as follows: dry in an oven at 60 - 90 °C for 1 - 2 h and then crush through a high-speed crusher and sieve through an 80 - 100 mesh sieve.

3. Use of the phosphorus-doped rice straw modified biochar material according to claim 1 for removing acetochlor, butachlor and / or metolachlor in the environment.

4. Use of the method according to claim 2 for preparing a phosphorus-doped rice straw modified biochar material for removing acetochlor, butachlor and / or metolachlor in the environment.

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