Preparation of sustained-release nanometer glyphosate based on dopamine modified attapulgite as carrier

Abstract

The present application relates to the field of new pesticides, and load glyphosate on dopamine modified nano-palygorskite (ATP) to prepare slow-release nano-glyphosate (DGlp). It comprises: (1) taking dopamine modified palygorskite as a carrier to obtain DGlp with a loading rate of about 60%, and conducting characterization research on the DGlp; (2) conducting research on the degradation of Glp and DGlp in soil. The results show that the degradation trend of DGlp is increased compared with Glp, which increases the release process of glyphosate from the carrier, and there is no significant difference in the degradation half-life of the two; (3) taking dwarf Bermuda as the research object, applying Glp, DGlp and drop acid · glyphosate (DS · Glp) respectively, conducting a 10-day pot experiment, and measuring the soil physical and chemical properties and the residual glyphosate content on the 10th day. The results show that there is no significant difference in the herbicidal effect of the three herbicides, but due to the slow-release property of DGlp, the persistence is longer, the residual amount in the soil is the least, and the environmental risk is lower. In addition, the present application has low preparation cost and wide practical prospect.

Description

Technical Field

[0001] This invention relates to the field of novel pesticides, specifically to a nano-pesticide based on dopamine-modified attapulgite as a carrier to load glyphosate and its herbicidal effect. Background Technology

[0002] As one of the world's major agricultural countries, my country relies heavily on pesticides for weeding and pest control. However, the development of organic agriculture and green food production in my country urgently requires the scientific use of pesticides to reduce chemical dosage and improve weeding and pest control efficiency. In recent years, my country's zero-growth campaign for pesticide use has steadily progressed, and pesticide utilization rates have gradually improved. Failure to effectively improve pesticide utilization rates will lead to a series of ecological and environmental problems, such as pathogens, non-point source pollution, eutrophication of water bodies, soil degradation, bioaccumulation in the food chain, and loss of biodiversity.

[0003] Glyphosate is a systemic, broad-spectrum, non-selective organophosphorus herbicide widely used due to its advantages such as strong non-selectivity and good weed control. However, traditional glyphosate formulations often drift, miss the target, or even degrade during spraying, resulting in loss into the environment and significantly limiting its routine use in agricultural practices. Furthermore, residual glyphosate and its commercial products in the environment have adverse effects on environmental organisms such as soil animals, aquatic organisms, amphibians, insects, and birds, including oxidative stress, genotoxicity, neurotoxicity, and growth toxicity.

[0004] Therefore, how to utilize new technologies to develop new formulations of pesticides such as water-based, dust-free, and controlled-release pesticides has gradually become a research hotspot and development direction in the agricultural field.

[0005] The development of nanomaterials and related technologies has provided new ideas for the creation of pesticide slow-release agents. Nanopesticides can significantly improve the bioactivity, utilization rate, and duration of action of pesticide active ingredients, reduce pesticide application rates and frequencies, and decrease pesticide runoff and residues. Currently developed nanopesticide formulations mainly include: ① polymer-based nanoformulations, which use nanomaterials as carriers for pesticide active ingredients to load pesticides and construct nano-pesticide delivery systems; ② directly processing pesticide active ingredients into nanoscale particles; ③ inorganic nanoparticles, namely, some metal and metal oxide nanoparticles have bactericidal effects and can be used directly as pesticides. Slow-release pesticides typically use natural organic polymers, porous inorganic small molecules, and other materials as carriers or media for pesticide active ingredients, achieving slow release of the active ingredients through adsorption, desorption, and diffusion principles. Due to their advantages of low dosage, long duration of action, low environmental pollution, and effective protection of active ingredients from environmental impacts, compared to other pesticides with larger dosage forms, they effectively improve pesticide utilization, reduce pesticide residues, and minimize the impact on humans, the application environment, and both target and non-target organisms.

[0006] This invention utilizes natural and environmentally friendly attapulgite as a carrier, and modifies it with dopamine hydrochloride to increase its specific surface area, thereby preparing a nano-pesticide with a sustained-release effect. Summary of the Invention

[0007] This invention prepares a nano-glyphosate pesticide with a slow-release effect. The purpose is to increase the glyphosate loading rate by modifying attapulgite with dopamine to obtain nano-glyphosate with a slow-release effect. Using this as a herbicide, the degradation trend and kinetic parameters of nano-glyphosate in soil are studied. The herbicidal effect and changes in soil physicochemical properties after the weeding process are also studied using dwarf Bermuda grass as the research object for 10 days.

[0008] To achieve the above-mentioned objectives, the technical approach adopted by this invention is as follows:

[0009] (1) Acidified attapulgite (ATP) was placed in Tirs-HCl solution, dopamine was added, and the mixture was stirred for 12 h. After washing, centrifugation, and freeze-drying, dopamine-modified nano-attapulgite (DA) was obtained. DA was added to glyphosate solution, stirred for 12 h, filtered, washed, and freeze-dried for 12 h. The glyphosate content was determined using a UV spectrophotometer, yielding nano-glyphosate (DGlp) with a loading rate of 60%.

[0010] (2) Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) characterization studies of HCl-ATP, DA, and DGlp showed that the attapulgite, after acidification and dopamine modification, had an increased specific surface area and a looser structure, thus improving the glyphosate loading rate. Furthermore, in the EDS spectrum, the characteristic elements of glyphosate only appeared in the DGlp spectrum. Next, X-ray energy dispersive spectroscopy (XPS) analysis revealed a double peak of p in the p2p orbital DGly in the fine spectrum, indicating the presence of the phosphate group of glyphosate. This peak was not detected in ATP and DA, confirming successful glyphosate loading.

[0011] (3) When Glp, DGlp and DA of the same concentration were added to homogeneous soil and the soil was kept at constant temperature and humidity, the degradation trend and kinetic parameters were studied. The results showed that: ① The degradation half-life of Glp and DGlp in soil was 117.9±10.4h, which was not statistically different; ② The DT50 and degradation rate constant of the nano-formulation DGlp were not affected by the carrier ATP, but due to the slow release process of Glp in the nano-formulation, the duration of action of glyphosate active molecules was increased and the efficacy time was prolonged.

[0012] (4) Four treatment groups—control group (CK), Glp, DS·Glp, and DGlp—weed control experiments were conducted. After spraying, the plants were incubated in a constant temperature and humidity incubator. Observations and records were recorded on days 0, 2, 4, 6, and 10. Soil samples were taken from the pots on the last day to determine the soil physicochemical properties and the residual glyphosate content in the soil. The results showed that: ① Compared with DS·Glp, DGlp had no significant difference in weed control effect and left less residue in the soil; ② Through the study of available phosphorus, four forms of phosphorus, phosphatase activity, and total phosphorus in the soil after weed control, the results indicated that DGlp had no significant difference in its effect on the form of phosphorus and phosphorus cycling in the soil compared with Glp and DS-Glp, indicating that no potential risk of DGlp to the soil has been found so far. Attached Figure Description

[0013] Figure 1 (A) is a SEM image of attapulgite (ATP), (B) is a SEM image of dopamine-modified attapulgite (DA), (C) is a SEM image of dopamine-modified attapulgite loaded with glyphosate (DGlp), (a1-a4) are EDS images of attapulgite (ATP), (b1-b6) are EDS images of dopamine-modified attapulgite (DA), and (c1-c7) are EDS images of dopamine-modified attapulgite loaded with glyphosate (DGlp).

[0014] Figure 2 (A) XPS full spectrum of ATP, DA, and DGlp; (B)(C) XPS fine spectrum of ATP, DA, and DGlp in specific orbitals;

[0015] Figure 3 Glyphosate degradation trend and kinetic curve;

[0016] Figure 4 (a) Weeding effect diagram, (b) Comparison of fresh weight and dry weight of roots and leaves of grass in different experimental groups after weeding;

[0017] Figure 5 (a) Soil available phosphorus content, (b) Soil total phosphorus content, (c) Soil phosphatase activity, (d) Soil residual glyphosate content, (e) Soil phosphorus component content;

[0018] Figure 6 Degradation kinetic parameters of Glp in different treatment groups; Detailed Implementation

[0019] The following experimental schemes enable those skilled in the art to better understand the present invention, effectively improve the precision of pesticide application, reduce pesticide residues in the environment, and extend the duration of pesticide efficacy, laying a research foundation for the future widespread use of nano-pesticides.

[0020] Experimental Scheme 1: Preparation of Glyphosate Nanopesticides

[0021] Acidification of attapulgite: 10g of attapulgite was dispersed in HCl (150ml, 2mol / L) and magnetically stirred at room temperature for 4h. After washing with water, filtration and freeze-drying were performed to obtain acidified attapulgite (ATP).

[0022] Dopamine-modified attapulgite: 3g of acidified ATP was dispersed in Tirs-HCl buffer (150ml, pH=8.5) and stirred for 30min. 0.3g of dopamine hydrochloride was added, and the mixture was stirred for 12h at room temperature in the dark. After centrifugation at 4000rpm for 10min, the sample was washed three times with deionized water to remove monomers and then freeze-dried for 24h to obtain dopamine-modified attapulgite (DA).

[0023] like Figure 1 (a) In comparison with (b), the attapulgite structure modified with dopamine is more loose, with increased specific surface area and pore volume, which can effectively improve the glyphosate loading rate.

[0024] Glyphosate loading: 1.5 g DA was dispersed in 15 ml of glyphosate aqueous solution (5 mg / ml), stirred at 25 °C for 12 h, filtered, the supernatant was washed with deionized water, and the glyphosate content was determined by UV spectrophotometer, and the loading rate was found to be about 60%. After freeze drying for 12 h, the final product DGlp was obtained.

[0025] like Figure 1 Comparing (a1), (b1), and (c1), the characteristic element p of glyphosate only appears in the EDS plot of DGlp, indicating that glyphosate was successfully loaded onto DA. In addition, as... Figure 2 (A) ATP, DA, and DGlp all contain O and C elements, and ATP and DA both contain Si elements, but the characteristic element P of glyphosate only appears in DGlp. Secondly, by scanning the p2p orbitals, a double peak of P was detected in DGlp, which belongs to the phosphate group of glyphosate, while it was not detected in DA and ATP, further demonstrating the successful loading of glyphosate.

[0026] Experimental Scheme 2: Glyphosate Degradation Experiment

[0027] After soil sampling, the soil was air-dried and ground. The samples were sieved and incubated in the dark at 25℃ for 7 days. DA, Glp, and DGlp were added to homogeneous soil at two concentrations of 50 mg / kg and 100 mg / kg, respectively. A control group (CK) was also included. All experimental groups were kept in a dark environment at 25℃ and 60% moisture content. Samples were taken periodically, and the residual amount of Glp in the soil was determined by high-performance liquid chromatography (HPLC).

[0028] like Figure 3(C)(D)(G)(H), regardless of whether the dosage is high or low, when DGlp is added to the soil, Glp will first be released from the attapulgite carrier, with the highest released concentrations reaching 49.72 mg / kg and 97.96 mg / kg, respectively, and maintaining over 90% concentration within 48 hours. Then, it will complete its degradation in the soil through a degradation trend similar to that of Glp. Furthermore, through... Figure 6 The results showed that when the addition levels of Glp were 50 mg / kg and 100 mg / kg, the degradation half-lives of its residues in the soil were 113.63 h and 126.20 h, respectively. For DGlp, the degradation half-lives were 108.30 h and 123.78 h, respectively, when the addition levels were 50 mg / kg and 100 mg / kg. Therefore, there was no statistically significant difference in degradation half-life between the high-dose and low-dose treatment groups. However, compared to Glp, DGlp has a unique sustained-release mechanism, thus effectively prolonging the duration of glyphosate's efficacy without affecting its overall effectiveness.

[0029] Experimental Scheme 3: Glyphosate Herbicide Experiment

[0030] Using dwarf Bermuda grass as the research subject, four experimental groups were set up: a control group, Glp, diethyl glyphosate (DS·Glp), and DGlp. Except for the control group, the other three groups were sprayed with a glyphosate concentration of 50 mg / kg and cultured in an incubator under constant temperature and humidity. The plants were photographed and observed on days 0, 2, 4, 6, and 10. Soil samples were taken from the potted plants on day 10 to determine their physicochemical properties and the residual glyphosate content in the soil.

[0031] like Figure 4 Treatments (a), Glp, DS·Glp, and DGlp showed similar results to pre-spray levels for 2 days after application. However, after 4 days, the weeds turned from green to yellow, and by day 6, large areas of weeds had wilted, dried, and turned brown. By day 10, almost all weeds had dried up and died, turning brown and breaking easily when pulled. All three treatments achieved good weed control by day 10. Figure 4 (b) In terms of fresh weight, compared to the control group, the biomass of both the aboveground and belowground parts decreased in all three treatment groups, with the Glp treatment group having the shortest root length. There was no significant difference in root and leaf biomass between the DS·Glp and DGlp treatment groups. In terms of dry weight, compared to the control group, the biomass of both the aboveground and belowground parts also decreased in all three treatment groups, with the Glp treatment group having the shortest root length. There was no significant difference in root and leaf biomass between the DS·Glp and DGlp treatment groups.

[0032] like Figure 5 (d) By measuring the glyphosate residue in the soil after weeding, it was found that DGlp residue in the soil was the lowest. Figure 5(a)(b) The addition of the three herbicides had no significant effect on the content of available phosphorus and total phosphorus in the soil; such as Figure 5 (e) The addition of herbicides had no significant effect on CaCl2-P in the soil, but the addition of DS·Glp and DGlp reduced the Citrate-P content in the soil. Furthermore, the addition of the three herbicides significantly affected the HCl-P and Enzyme-P contents. Figure 5 (c) Although the addition of the three herbicides did not significantly affect the activity of acid phosphatase in the soil, they all reduced the activity of alkaline phosphatase in the soil.

[0033] In summary, the nano-glyphosate prepared in this invention has a similar herbicidal effect to that of commercially available glyphosate-based products. However, due to its slow-release properties, it can effectively improve the pesticide's persistence and utilization rate, while also leaving lower residues in the environment. Furthermore, the carrier used is a low-cost, environmentally friendly material. Therefore, this invention has broad application prospects.

Claims

1. A method for preparing a sustained-release nanopesticide based on a dopamine-modified attapulgite as a carrier, characterized in that, The preparation method includes the following steps: (1) Acidification of attapulgite: attapulgite is dispersed in HCl solution and magnetically stirred at room temperature. After washing with water, filtering and freeze drying, acidified attapulgite is obtained. (2) Dopamine-modified attapulgite: The acidified attapulgite was dispersed in Tris-HCl buffer and stirred. Dopamine was added and stirred at room temperature in the dark. The mixture was centrifuged, washed with deionized water, and freeze-dried to obtain dopamine-modified attapulgite. (3) Loading of glyphosate: The dopamine-modified attapulgite was dispersed in an aqueous solution of glyphosate, stirred, filtered, the supernatant was washed with deionized water, and freeze-dried to obtain a slow-release nano-pesticide.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the HCl solution is 2 mol / L, and the stirring time is 4 h.

3. The preparation method according to claim 1, characterized in that, Step (2) Tris-HCl buffer pH=8.5, after adding dopamine, the stirring time is 12h, the centrifugation speed is 4000rpm, and the freeze drying time is 24h.

4. The preparation method according to claim 1, characterized in that, The stirring time in step (3) is 12 hours, and the freeze-drying time is 12 hours.

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