A kind of slow-release pesticide based on phosphorus and ammonia modified biochar and its preparation method

Abstract

The present invention belongs to the technical field of pesticide preparations, and specifically relates to a phosphorus- and ammonia-modified biochar-based slow-release pesticide and a preparation method thereof. The present invention provides a phosphorus-modified biochar, which is prepared from a biomatrix and phosphoric acid. Compared with unmodified biochar, the specific surface area and pore volume of the biochar after phosphorus modification are increased, indicating that under high temperature and phosphoric acid catalysis, the biochar forms a larger specific surface area and more microporous structures. In addition, phosphorus-ammonia-modified biochar is further modified using ammonia water on the basis of the phosphorus-modified biochar, and its specific surface area and pore volume are further increased, indicating that the phosphate groups in the pores of the biochar after ammonia modification are replaced, resulting in the formation of more tiny pores. Based on the two modified biochars, the present invention further provides two modified biochar slow-release pesticides. The two slow-release pesticides can reduce the phytotoxicity to corn while inhibiting the growth of the radicle and the plumule of Portulaca oleracea, and have important application value.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide preparations, and specifically relates to a phosphorus- and ammonia-modified biochar-based slow-release pesticide and a preparation method thereof. Background Art

[0002] Since most pesticides (such as dinotefuran, 2,4-D, trichlorfon, etc.) have the disadvantages of high water solubility, they are easily lost with water, resulting in low pesticide effectiveness, crop damage and environmental pollution. Therefore, the development of efficient and safe new slow-release pesticides to achieve the improvement of pesticide quality and efficiency, and the reduction of quantity and emission has become a current research hotspot. At present, in response to the above shortcomings, people have developed slow-release pesticide carriers such as natural polymers, synthetic polymers, nano-calcium carbonate, LDHs, mesoporous silica, lignin microspheres, etc. However, the above carriers have the disadvantages of poor adsorption performance, complex manufacturing process, high cost, etc., which are not conducive to actual production applications.

[0003] Biochar is a stable carbon-rich solid material left after the combustible gas is separated from the biomass after being fired at a relatively low temperature of ≤700℃ under completely anaerobic or partially anoxic conditions. It has the characteristics of large specific surface area, high porosity, high physical and chemical stability and good surface reactivity, and is widely used as a functional material. At the same time, its rich microporous structure, aromatic functional groups and surface area can adjust the physical properties of soil porosity, density and particle size distribution, thereby changing the soil oxygen concentration, water storage and nutrient conditions.

[0004] The biochar generated by traditional pyrolysis has a lower specific surface area and smaller porosity, so the adsorption capacity of pesticides is limited, and it cannot achieve the effect of fertilizer while exerting the effect of medicine, which limits its application in production. Therefore, it is necessary to develop a new type of biochar that can efficiently load pesticides and fertilizers, and develop slow-release pesticides based on this biochar. Summary of the invention

[0005] The purpose of the first aspect of the present invention is to provide a phosphorus-modified biochar.

[0006] The second aspect of the present invention aims to provide a method for preparing phosphorus-modified biochar.

[0007] The third aspect of the present invention aims to provide a phosphorus-ammonia modified biochar.

[0008] The fourth aspect of the present invention aims to provide a method for preparing phosphorus-ammonia modified biochar.

[0009] The fifth aspect of the present invention aims to provide an application.

[0010] The sixth aspect of the present invention aims to provide a sustained-release product.

[0011] The seventh aspect of the present invention aims to provide a method for preparing a sustained-release product.

[0012] The eighth aspect of the present invention aims to provide an application of a sustained-release product.

[0013] In order to achieve the above-mentioned purpose of the present invention, the technical solution adopted by the present invention is:

[0014] The first aspect of the present invention provides a phosphorus-modified biochar, characterized in that:

[0015] The specific surface area of ​​the phosphorus-modified biochar is 600-1000m 2 / g; and / or the pore volume of the phosphorus-modified biochar is 1.0 to 1.2 cm 3 / g.

[0016] The second aspect of the present invention provides a method for preparing the phosphorus-modified biochar of the first aspect of the present invention, comprising the following steps: mixing a biological matrix with an acid, and pyrolyzing the mixture to obtain the phosphorus-modified biochar.

[0017] Preferably, the mass ratio of the biological matrix to the acid is 1:(1.6-8).

[0018] Preferably, the biomatrix comprises agricultural and forestry wastes.

[0019] Preferably, the agricultural and forestry waste includes at least one of wood chips, straw, coconut shells, fungus residues, biogas residues, rice husks, and livestock and poultry manure.

[0020] Preferably, the biomatrix further comprises crushing, and the crushed biomatrix passes through a 60-100 mesh sieve.

[0021] Preferably, the acid includes at least one of phosphoric acid, pyrophosphoric acid, and metaphosphoric acid.

[0022] Preferably, the acid comprises phosphoric acid.

[0023] Preferably, said mixing comprises soaking.

[0024] Preferably, the soaking time is 8 to 10 hours.

[0025] Preferably, the pyrolysis temperature is 300-700°C.

[0026] Preferably, the pyrolysis time is 2 to 6 hours.

[0027] Preferably, the heating rate of the pyrolysis is 5 to 10 °C min -1 .

[0028] Preferably, the pyrolysis is carried out under a protective atmosphere of protective gas.

[0029] Preferably, the protective gas includes at least one of nitrogen, helium and argon.

[0030] The third aspect of the present invention provides a phosphorus-ammonia modified biochar, characterized in that:

[0031] The specific surface area of ​​the phosphorus-ammonia modified biochar is 1000-1400m 2 / g; and / or the pore volume of the phosphorus-ammonia modified biochar is 1.4 to 1.8 cm 3 / g.

[0032] The fourth aspect of the present invention provides a method for preparing the phosphorus-ammonia modified biochar of the third aspect of the present invention, comprising the following steps: mixing the phosphorus-modified biochar of the first aspect of the present invention with ammonia, and pyrolyzing to obtain.

[0033] Preferably, the mass ratio of the phosphorus-modified biochar to ammonia is 1:(4.5-9).

[0034] Preferably, the phosphorus-modified biochar needs to be mixed with a solvent.

[0035] Preferably, the solvent includes at least one of water, ethanol and ethylene glycol.

[0036] Preferably, the solvent comprises ethylene glycol.

[0037] Preferably, the ratio of the phosphorus-modified biochar to the solvent is 80 to 160 mL of solvent per mg of phosphorus-modified biochar.

[0038] Preferably, the ammonia includes at least one of ammonia gas and ammonia water.

[0039] Preferably, the ammonia comprises aqueous ammonia.

[0040] Preferably, the temperature of the pyrolysis reaction is 160-200°C.

[0041] Preferably, the pyrolysis reaction time is 8-10 h.

[0042] The fifth aspect of the present invention provides the use of the phosphorus-modified biochar of the first aspect of the present invention and / or the phosphorus-ammonia-modified biochar of the third aspect of the present invention in preparing products.

[0043] Preferably, the product includes at least one of fertilizers and pesticides.

[0044] Preferably, the product comprises a pesticide.

[0045] Preferably, the pesticide comprises a slow-release pesticide.

[0046] The sixth aspect of the present invention provides a slow-release product, comprising the phosphorus-modified biochar of the first aspect of the present invention, and / or the phosphorus-ammonia-modified biochar of the third aspect of the present invention.

[0047] Preferably, the slow-release product also includes at least one of pesticides and fertilizers.

[0048] Preferably, the sustained-release product further comprises a pesticide.

[0049] Preferably, the pesticide includes at least one of dinotefuran, trichlorfon, and 2,4-D.

[0050] Preferably, the pesticide comprises 2,4-D.

[0051] The seventh aspect of the present invention provides a method for preparing the sustained-release product of the sixth aspect of the present invention, comprising mixing the phosphorus-modified biochar of the first aspect of the present invention and / or the phosphorus-ammonia-modified biochar of the third aspect of the present invention with pesticides or fertilizers, and performing solid-liquid separation to obtain the sustained-release product.

[0052] Preferably, the mixing time is 12-24 hours.

[0053] The eighth aspect of the present invention provides use of the sustained-release product of the sixth aspect of the present invention in reducing product side effects.

[0054] Preferably, the product comprises a pesticide.

[0055] The beneficial effects of the present invention are:

[0056] The invention provides a phosphorus-modified biochar, which is prepared from a biological matrix and phosphoric acid. Compared with the unmodified biochar, the specific surface area of ​​the phosphorus-modified biochar is increased from 60.88 m 2 / g increased to 795.52m 2 / g, pore volume from 0.02cm 3 / g increased to 1.12cm 3 / g, indicating that under high temperature and phosphoric acid catalysis, biochar formed a larger specific surface area and more microporous structures.

[0057] The present invention also provides a phosphorus-ammonia modified biochar, which is further modified with ammonia water on the basis of phosphorus-modified biochar. Compared with phosphorus-modified biochar, the specific surface area and pore volume of phosphorus-ammonia modified biochar are further increased, and the specific surface area is increased from 795.52m 2 / g increased to 1209.42m 2 / g, pore volume from 1.12cm 3 / g increased to 1.63cm 3 / g, which is because the phosphate groups in the pores of biochar are replaced after ammonia modification, resulting in the formation of more tiny pores.

[0058] Based on the two modified biochars, the present invention further provides two modified biochar slow-release pesticides. The two slow-release pesticides can inhibit the growth of radicle and plumule of purslane and reduce the pesticide damage to corn, thus having important application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The scanning electron microscope images of WBC (prepared in Comparative Example 1), P-WBC (prepared in Example 1), and NP-WBC (prepared in Example 2) at a magnification of 2.0k.

[0060] Figure 2 These are infrared spectroscopic images of WBC (prepared in Comparative Example 1), P-WBC (prepared in Example 1), and NP-WBC (prepared in Example 2).

[0061] Figure 3 The relationship between the release rate of P-WBC@2,4-D and NP-WBC@2,4-D prepared in Example 3-4 and time.

[0062] Figure 4 These are the effects of P-WBC@2,4-D and NP-WBC@2,4-D prepared in Example 3-4 on corn germination.

[0063] Figure 5 These are the effects of P-WBC@2,4-D and NP-WBC@2,4-D prepared in Example 3-4 on the germination of Portulaca oleracea. DETAILED DESCRIPTION

[0064] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0065] The pesticide used in the present invention is 2,4-dichlorophenoxyacetic acid (2,4-D), with a molecular formula of C8H6Cl2O3 and a molecular weight of 221.037 g / mol. 2,4-D is a phenoxyacetic acid herbicide with low price, strong systemic effect, high efficiency and low toxicity, and is widely used to prevent and control weeds in the field. The present invention selects 2,4-D for testing, and other pesticides on the market, such as dinotefuran and trichlorfon, can also achieve the technical effects of the present invention. The 2,4-D reagent is produced by Aladdin Company with a purity of 98%.

[0066] Example 1 Preparation of phosphorus-modified biochar

[0067] Add small pieces of pine sawdust to the grinder, and after being fully crushed, pass through a 100-mesh sieve and dry. Then mix the pine sawdust powder with 40% phosphoric acid solution in a beaker, with an impregnation ratio of 1:4 (w material: w 40wt% phosphoric acid solution = 1:4). After soaking at room temperature for 10 hours, put the wet mixture into a 90*90mm ceramic ark, then put the ark into a tube furnace, pass nitrogen for 10 minutes, and then heat it at 10℃·min under a nitrogen protection atmosphere. -1 The product was heated at a heating rate of 100 °C and then kept at 500 °C for 2 h. After the product was cooled to room temperature, it was washed with deionized water for 6 times, and finally dried and ground at 65 °C to obtain phosphorus-modified biochar powder P-WBC.

[0068] Example 2 Preparation of a phosphorus-ammonia modified biochar

[0069] 0.5 g of phosphorus-modified biochar powder was mixed with 60 mL of ethylene glycol and ultrasonicated for 30 min to fully mix it. Then 20 mL of concentrated ammonia water (McLean, 25-28 wt%) was added and stirred with a magnetic stirrer for 30 min to fully mix it. The obtained mixture was then placed in a Teflon-lined reactor and subjected to a solvent thermal reaction at 200 ° C. After reacting for 10 hours, the obtained precipitate was filtered and collected in a vacuum filtration bottle using a 0.22 μm organic filter membrane, rinsed with deionized water 3 times, and dried at 65 ° C for 24 hours for use to obtain phosphorus-ammonia-modified biochar powder NP-WBC

[0070] Example 3 Preparation of a phosphorus-modified biochar slow-release pesticide

[0071] In this embodiment, an adsorption method is used to prepare a phosphorus-modified biochar-based slow-release herbicide pesticide. The preparation method is as follows: 0.5 g of dried phosphorus-modified biochar P-WBC is added to 50 mL of a 2,4-D solution with a concentration of 1500 mg / L, and the solution is shaken on a shaker for 18 hours. After the biochar fully adsorbs 2,4-D, the suspension of biochar and 2,4-D is filtered using a 0.22 μm water filter membrane in a vacuum filtration bottle. The obtained solid is dried, collected, and sealed for storage to obtain a phosphorus-modified biochar slow-release pesticide P-WBC@2,4-D.

[0072] Example 4 Preparation of a phosphorus-ammonia modified biochar slow-release pesticide

[0073] In this embodiment, an adsorption method is used to prepare a phosphorus-modified biochar-based slow-release herbicide pesticide. The preparation method is as follows: 0.5 g of dried phosphorus-modified biochar P-WBC is added to 50 mL of a 2,4-D solution with a concentration of 1500 mg / L, and the solution is shaken on a shaker for 18 hours. After the biochar fully adsorbs 2,4-D, the suspension of biochar and 2,4-D is filtered using a 0.22 μm water filter membrane in a vacuum filtration bottle. The obtained solid is dried, collected, and sealed for storage to obtain a phosphorus-ammonia modified biochar slow-release pesticide NP-WBC@2,4-D.

[0074] Comparative Example 1 Unmodified Biochar WBC

[0075] Small pieces of pine sawdust were added to the grinder, and after being fully crushed, they were passed through a 100-mesh sieve and dried. Then they were placed in a 90*90 mm ceramic ark, and then the ark was placed in a tube furnace. After nitrogen was passed through for 10 minutes, the ark was heated at 10°C / min under a nitrogen atmosphere. -1 The product was heated at a heating rate of 100 °C and then kept at 500 °C for 2 h. After the product was cooled to room temperature, it was washed with deionized water for 6 times and finally dried and ground at 65 °C to obtain biochar powder WBC.

[0076] Effect Example 1 Determination of the physicochemical properties of biochar

[0077] 1. Results of the determination of the physical and chemical properties of biochar

[0078] The morphology of the biochar samples prepared in Examples 1-2 and Comparative Example 1 was detected using a scanning electron microscope (Zeiss, EVO MA10).

[0079] The surface morphology of the modified biochars in Examples 1-2 and Comparative Example 1 is as follows: Figure 1 Compared with WBC, the phosphoric acid after P-WBC modification corroded fine pores on the surface of biochar, introduced phosphorus, and increased the oxygen content on the surface. NP-WBC still has the characteristics of phosphoric acid corrosion, with a large surface roughness and a high degree of carbonization.

[0080] The surface elements of the biochars of Examples 1-2 and Comparative Example 1 were determined using an energy dispersive X-ray spectrometer (EDS), and the method was as follows: a scanning electron microscope (Zeiss, EVO MA10) equipped with an X-ray spectrometer (Bruker) was used to perform EDS element analysis on the biochar samples prepared in Examples 1-2 and Comparative Example 1. The biochar with the platinum sample sprayed on the surface was scanned at an accelerating voltage of 10.0 kV, and an EDS element semi-quantitative analysis was performed at an accelerating voltage of 20.0 kV to detect the distribution of each element on the surface of the biochar.

[0081] The results are shown in Table 1. Compared with the unmodified biochar, the surface of the biochar modified with phosphorus-ammonia has the characteristics of high nitrogen and oxygen content.

[0082] Table 1 Relative contents of elements in different biochar materials measured by EDS

[0083]

[0084] nd means the content is lower than the detection range of the instrument and was not detected.

[0085] 2. Elemental analysis

[0086] The C and N element contents in the biochar samples prepared in Examples 1-2 and Comparative Example 1 were measured using an elemental analyzer (Elementar, Vario EL) in combustion mode. The results are shown in Table 2.

[0087] The overall carbon content in biochar is relatively high. The carbon content in unmodified biochar WBC, phosphorus-modified biochar P-WBC and ammonia-modified biochar NP-WBC reached 79.03%, 47.05% and 80.64% respectively. The nitrogen content in ammonia-modified biochar increased significantly, reaching 0.64%. This shows that ammonia modification introduces more nitrogen into biochar. After being applied to the soil, the rich carbon and nitrogen content in biochar can improve soil quality and soil fertility.

[0088] Table 2 Carbon and nitrogen contents in WBC, P-WBC, and NP-WBC

[0089]

[0090] 3. Specific surface area

[0091] The specific surface area of ​​the biochars of Examples 1-2 and Comparative Example 1 was measured using a specific surface area meter (BSD, BSD-PS1). The samples were first vacuum degassed at 170°C for 600 min, and then the adsorption and desorption isotherms were measured in liquid nitrogen. The specific surface area was measured by the Brunauer-Emmett-Teller (BET) method, and the pore size distribution and pore volume were calculated from the desorption branch of the isotherm by the Barrett-Joyner-Halenda (BJH) method.

[0092] The measurement results of the specific surface area and pore volume of the biochar of Examples 1-2 and Comparative Example 1 are shown in Table 3.

[0093] Table 3 Determination of specific surface area, pore volume and average pore size in biochar under different modification methods

[0094]

[0095] Phosphorus modification can significantly increase the specific surface area and pore volume of biochar. Compared with the unmodified biochar WBC, the specific surface area of ​​the biochar P-WBC after phosphorus modification increased from 60.88m2 / g to 795.52m2 / g, and the pore volume increased from 0.02cm 3 / g increased to 1.12cm 3 / g, indicating that under high temperature and phosphoric acid catalysis, biochar formed a larger specific surface area and more microporous structures. Compared with phosphorus-modified biochar P-WBC, the specific surface area and pore volume of phosphorus-ammonia biochar NP-WBC further increased, and the specific surface area increased from 795.52m2 / g to 1209.42m 2 / g, pore volume from 1.12cm 3 / g increased to 1.63cm 3 / g, which is due to the replacement of the phosphate groups in the pores of the biochar after ammonia modification, resulting in the formation of more tiny pores. The larger specific surface area and pore volume after modification indicate that the two biochars have strong adsorption capacity and have good application prospects in the adsorption materials of pesticides (such as 2,4-D).

[0096] 4. Functional group structure

[0097] An infrared spectrometer (ThermoFisher Scientific, Nicolet 6700) was used to perform infrared spectroscopy analysis on the biochar samples prepared in Examples 1-2 and Comparative Example 1. The scanning range was 400-4000 cm-1, and the pure KBr sample was subtracted as a blank background.

[0098] The functional group structures of the biochars of Examples 1-2 and Comparative Example 1 were determined. Figure 2 shown.

[0099] All biochars were at 3407, 1439 and 1376 cm –1 There are absorption peaks at 3407cm –1 The absorption peaks at 1439 and 1376 cm are caused by the stretching vibration of the OH bond. –1 The absorption peak at is mainly attributed to the stretching vibration of CH on cellulose, hemicellulose and lignin in biomass.

[0100] The infrared spectrum of the phosphorus-modified biochar P-WBC showed more phosphorus-related characteristic peaks, such as P-WBC at 1219 cm -1 With 1072cm -1 The absorption peak caused by the stretching vibration of O=P or OP bond appears at 1690cm -1 、1560cm -1 、1066cm-1 and 1035cm -1 A new absorption peak appeared at 1690cm -1 The peak at 1560 cm -1 The absorption peak at 1066 cm -1 The appearance of the absorption peak at 1035cm -1 The appearance of the absorption peak at is mainly due to the vibration of the COC bond. This indicates that ammonia modification successfully introduced nitrogen-containing groups into biochar, and these groups mainly exist in the form of CN bonds and amide bonds.

[0101] The rich oxygen-containing functional groups on the surface of biochar and the modified phosphorus and nitrogen-containing functional groups provide more adsorption sites, giving biochar strong adsorption properties, making it widely used as a carrier material for fertilizers and pesticides.

[0102] Effect Example 2 Slow-release effect of modified biochar-based slow-release pesticide

[0103] The specific method of desorption kinetics is as follows: 0.5g of different types of biochar (Example 1-2) were added to 50mL of 2,4-D solution with a concentration of 1500mg / L, and shaken on a shaker for 18h. After the biochar fully adsorbed 2,4-D, the suspension of biochar and 2,4-D was filtered using a 0.22μm water filter membrane in a vacuum filtration bottle. The filtrate was collected, and the amount of 2,4-D in the obtained filtrate was measured. The difference between the amount of 2,4-D in the 2,4-D solution before adsorption was the amount of 2,4-D adsorbed by the biochar. The obtained biochar was then transferred to 500mL of pure water and shaken on a shaker at a speed of 180rpm. Every 0, 0.5, 1, 2, 4, 8, 16, 24, 32, 40, and 48h, 2.5mL of the suspension was passed through a 0.22μm water filter membrane and the filtrate was collected. The 2,4-D content in the filtrate was measured using an ultraviolet spectrophotometer at a wavelength of 280 nm. The amount of 2,4-D released by the biochar in each time period was calculated by the difference between the 2,4-D content of the supernatant in each time period and the 2,4-D content of the supernatant at 0 hours. The specific formula is as follows:

[0104]

[0105] Among them, w r is the mass of 2,4-D released per gram of biochar@2,4-D (mg / g); w rt w is the mass of 2,4-D in the solution at the corresponding time (mg); r0 w is the mass of 2,4-D in the initial solution at 0 hours (mg); rcis the mass of biochar (g).

[0106] The relationship between the release rate of modified biochar@2,4-D of Example 1-2 and time is as follows: Figure 3 shown.

[0107] All modified biochars @ 2,4-D reached equilibrium in 10 hours for 2,4-D desorption, and the desorption amount in the first 5 hours could reach 90% of the equilibrium desorption amount. The maximum release rate of ammonia-modified biochar was 21.37% (20.94 mg / g), while the maximum release rate of phosphorus-modified biochar was 9.34% (10.06 mg / g), indicating that the adsorption of 2,4-D by modified biochar was not permanent, and the adsorbed 2,4-D could still be detached from the modified biochar. The slow-release effect of 2,4-D on modified biochar indicates that it can be used as a slow-release carrier for herbicides and pesticides.

[0108] The loading rate and application amount of the modified biochar prepared in Example 1-2 were calculated as follows: After the modified biochar fully adsorbed 2,4-D, the biochar solid was collected on a suction flask through a 0.22um filter membrane. During the collection, the surface of the biochar was rinsed with pure water 3 times to wash away the unadsorbed 2,4-D on the surface, and the biochar material loaded with 2,4-D was obtained after drying. The difference between the amount of biochar before adsorption is the loading rate of biochar for 2,4-D, and the specific formula is as follows:

[0109]

[0110] Where, % is the loading rate of biochar; w t is the mass of biochar after loading 2,4-D (mg / g); w0 is the initial mass of biochar (mg).

[0111] The amount of biochar@2,4-D material applied was calculated based on the effective concentration of 2,4-D of 12 mg / L (twice the field application rate) and the loading rate of biochar on 2,4-D. The specific application amount and effective concentration of 2,4-D are shown in Table 4.

[0112] Table 4 Application amount and effective concentration of biochar

[0113]

[0114] Effect Example 3 Biological Activity of Modified Biochar-Based Slow-Release Pesticide

[0115] Sterilized absorbent paper was placed in each culture dish, along with 6 corn seeds and 30 purslane seeds. Then, 5 mL of biochar@2,4-D suspension with an effective 2,4-D concentration of 12 mg / L was added. Pure water (CK) was used as a negative control, and 2,4-D powder (SS) and 2,4-D reagent (SJ) of the same concentration were used as positive controls. Each treatment was repeated 3 times.

[0116] The environment was maintained at 25°C with 14h light and 10h dark. After 72h of cycling, the germination rates of corn and purslane were counted, and the radicle and plumule lengths of corn and purslane were measured to verify the effect of the modified biochar@2,4-D prepared in Example 1-2 on the germination of corn and purslane seeds.

[0117] The results are as follows Figure 4 , Figure 5 And as shown in Table 5.

[0118] Table 5 Effects of commercially available 2,4-D reagents, phosphorus-modified biochar, and phosphorus-ammonia-modified biochar-based slow-release pesticides on the germination of corn and purslane

[0119]

[0120] The same column without the same letter indicates significant difference (P<0.05).

[0121] The commercially available 2,4-D reagent, phosphorus-modified biochar, and phosphorus-ammonia-modified biochar-based slow-release pesticide materials all significantly reduced the radicle length and plumule length of corn. Compared with the commercially available 2,4-D, the radicle of phosphorus-modified biochar and phosphorus-ammonia-modified biochar-based slow-release pesticide materials was longer, indicating that the slow release of 2,4-D by biochar-based slow-release pesticide materials can reduce the damage to corn to a certain extent.

[0122] The commercially available 2,4-D reagent, phosphorus-modified biochar, and phosphorus-ammonia-modified biochar-based slow-release pesticide materials all significantly reduced the radicle length and plumule length of Portulaca oleracea. In addition, there was no significant difference in the inhibitory effect of phosphorus-modified biochar, phosphorus-ammonia-modified biochar-based slow-release pesticide materials and commercially available 2,4-D on the radicle and plumule length of weeds, indicating that the slow release of 2,4-D by biochar-based slow-release pesticide materials did not reduce its weed control effect.

[0123] The above experimental results show that phosphorus-modified biochar and phosphorus-ammonia-modified biochar-based slow-release pesticide materials not only inhibit the growth of radicle and plumule of Portulaca oleracea, but also reduce the pesticide damage to corn.

Claims

1. A method for preparing phosphorus-ammonia modified biochar, comprising the following steps: S1: mixing the biomass with acid and pyrolyzing it to obtain phosphorus-modified biochar; S2: mixing the phosphorus-modified biochar with ammonia and pyrolyzing the mixture to obtain; In S1, the mass ratio of the biological matrix to the acid is 1:(1.6-8); The acid includes at least one of phosphoric acid, pyrophosphoric acid, and metaphosphoric acid; The mixing includes soaking; The soaking time is 8 to 10 hours; The pyrolysis temperature is 300-700°C; The pyrolysis time is 2 to 6 hours; The heating rate of the pyrolysis is 5 to 10 °C min -1 ; The specific surface area of ​​the phosphorus-modified biochar is 600-1000m 2 / g; The pore volume of the phosphorus-modified biochar is 1.0 to 1.2 cm 3 / g; In S2, the mass ratio of the phosphorus-modified biochar to ammonia is 1:(4.5-9); The pyrolysis temperature is 160-200°C; The reaction time of the pyrolysis is 8-10h; The phosphorus-modified biochar also needs to be mixed with a solvent; The solvent includes at least one of water, ethanol and ethylene glycol; The specific surface area of ​​the phosphorus-ammonia modified biochar is 1000-1400m 2 / g; The pore volume of the phosphorus-ammonia modified biochar is 1.4 to 1.8 cm 3 / g.

2. The preparation method according to claim 1, characterized in that: In S1, the biological matrix includes agricultural and forestry waste; The agricultural and forestry wastes include at least one of wood chips, straw, coconut shells, fungus residues, biogas residues, rice husks, and livestock and poultry manure.

3. The preparation method according to claim 1, characterized in that: In S1, the biomatrix further comprises crushing, and the crushed biomatrix passes through a 60-100 mesh sieve.

4. The preparation method according to claim 1, characterized in that: In S1, the pyrolysis is carried out under a protective atmosphere of protective gas; The protective gas includes at least one of nitrogen, helium and argon.

5. The preparation method according to claim 1, characterized in that: In S2, the ratio of the phosphorus-modified biochar to the solvent is 80 to 160 mL of solvent per mg of phosphorus-modified biochar.

6. The preparation method according to claim 1, characterized in that: In S2, the mixing includes ultrasonic mixing.

7. A method for preparing a slow-release pesticide, characterized in that: The phosphorus-ammonia modified biochar prepared by the method according to any one of claims 1 to 6 is mixed with pesticides, and the solid-liquid separation is performed to obtain.

8. The preparation method according to claim 7, characterized in that: The pesticide includes at least one of dinotefuran, trichlorfon and 2,4-D.

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