Preparation method of pesticide droplet stabilizer based on corncob

Abstract

The invention discloses a preparation method of a pesticide droplet stabilizer based on corncobs, and in order to realize high-value utilization of the corncobs, the method mainly comprises the following steps: pretreatment of the corncobs, acquisition of corncob cellulose, extraction of cellulose nanocrystals, and extraction of cellulose nanofibers. Characterization of a corncob nanofiber stabilizer and preparation and testing of a corncob-based pesticide droplet stabilizer. The natural cellulose nanocrystals and cellulose nanofibers can be successfully extracted from the corncobs through the method, and the method can be applied to stabilization of pesticide liquid drops and stabilization of the pesticide liquid, which is of great significance to high-value utilization of the corncobs and stabilization of the pesticide liquid.

Description

Technical Field

[0001] The invention belongs to the technical field of high-value utilization of agricultural engineering straw, and more specifically, relates to a method for preparing a pesticide droplet stabilizer based on corncobs. Background Art

[0002] In modern agricultural production, the application of pesticides plays an important role in preventing and controlling crop diseases and pests and ensuring food security. However, there are many problems in the use of pesticides, such as the drift and evaporation of pesticide droplets during spraying, which not only reduces the effective utilization rate of pesticides, but also may pollute the environment. In order to improve the efficiency of pesticide use and reduce its impact on the environment, researchers have developed a variety of pesticide adjuvants to improve the performance of pesticide formulations. Among them, droplet stabilizers, as an important pesticide adjuvant, can effectively increase the surface tension stability of droplets, reduce the evaporation rate of droplets, and enhance the adhesion of droplets on the crop surface. Traditional droplet stabilizers mostly use synthetic chemicals, such as surfactants, but these synthetic chemicals are often expensive and may have adverse effects on the ecological environment.

[0003] In recent years, with the popularization of the concept of sustainable development and the advancement of technology, the use of natural renewable resources as pesticide adjuvants has become a research hotspot. Corncobs, as a common byproduct of agricultural production, are often burned and wasted, but corncobs are rich in cellulose, hemicellulose, and lignin, and are a potential low-cost, environmentally friendly source of raw materials.

[0004] The present invention aims to provide a method for preparing a pesticide droplet stabilizer based on corn cobs, which can effectively utilize agricultural waste, reduce environmental pollution, and improve the economy and effectiveness of pesticide use. Through the technical solution of the present invention, a droplet stabilizer with excellent performance and low cost can be obtained, which is of great significance for the high-value utilization of corn stalks and the stability of pesticide liquid. Summary of the invention

[0005] The purpose of the present invention is to realize the high-value utilization of corn cobs, provide a method for preparing a pesticide droplet stabilizer based on corn cobs, improve the targeted utilization rate of pesticide droplets, and have a simpler production process and lower production costs.

[0006] The preparation method of a corncob-based pesticide droplet stabilizer of the present invention is as follows:

[0007] Step 1: pretreatment of corn cobs, specifically including the following.

[0008] (1) crushing: putting corn cobs with a moisture content of less than 20% into a blender and chopping for 10 minutes;

[0009] (2) filtering, passing the corncob powder through a 35-mesh sieve;

[0010] Step 2: obtaining corncob cellulose, specifically including the following.

[0011] (1) Alkali treatment: the pretreated corncob powder is mixed with a 2% sodium hydroxide aqueous solution at a solid-liquid ratio of 1:20, and stirred at 90-100°C for 4-6 hours. The porous structure of the corncob can be further optimized by temperature pyrolysis to increase its specific surface area. The optimization of pyrolysis conditions can be guided by the Arrhenius equation:

[0012]

[0013] Where k is the thermal decomposition reaction rate constant, A is the frequency factor, and E a is the activation energy, R is the ideal gas constant, and T is the pyrolysis temperature.

[0014] (2) Remove alkali by washing with distilled water 5 to 8 times;

[0015] (3) bleaching the fibers with equal amounts of acetate buffer (2.7% by mass NaOH and 7.5% by mass acetic acid) and chlorite (1.7% by mass NaClO2 solution) at 80°C for 6 to 8 hours;

[0016] (4) Purification: The bleached fiber is repeatedly washed in distilled water until the pH value of the fiber becomes 7, and then dried in an air circulation drying oven at 40°C for 24 hours. The material obtained after purification is treated pure cellulose.

[0017] Step three: extraction of cellulose nanocrystals, specifically including the following.

[0018] (1) Extracting nanocrystals: Each gram of pure cellulose sample was placed in 15 mL of H2SO4 (9.17 mol / L) for hydrolysis. The hydrolysis was carried out at 45°C for 1 to 2 hours with continuous stirring.

[0019] (2) dilution and acid removal: dilute the suspension 10 times with cold water to stop the hydrolysis reaction, and centrifuge at 7500 rpm for more than 10 minutes to remove excess acid;

[0020] (3) Dialysis: dialyze the precipitate with tap water to remove inactive sulfate groups, salts, and soluble sugars until the pH reaches 7;

[0021] (4) Drying: The dialyzate was ultrasonically treated for 10 minutes and vacuum dried to obtain corncob cellulose nanocrystals.

[0022] Step 4: Extraction of cellulose nanofibers, specifically including the following.

[0023] (1) Tetramethylpiperidine treatment: corncob cellulose was suspended in water containing TEMPO (1 mmol / L) and sodium bromide (10 mmol / L) and stirred continuously at a liquid-to-solid ratio of 100 to 120;

[0024] (2) adjusting the pH value by adding NaOH to adjust the pH of the reaction system to 10.5;

[0025] (3) Tetramethylpiperidine-mediated oxidation: At 25 °C, an aqueous solution of NaClO (10 mmol / g cellulose) was added to initiate TEMPO-mediated oxidation, followed by the addition of NaOH to maintain the pH at 10.5 for 2 h.

[0026] (4) washing, repeatedly adding ethanol 6 times to obtain a solid substance, and then washing it with deionized water 10 times;

[0027] (5) Centrifugal drying: The solid was centrifuged (8000 rpm, 5 minutes) and then vacuum dried for 48 hours to obtain corncob cellulose nanofibers.

[0028] Step 5: Characterization of corncob nanofiber stabilizer, specifically including the following.

[0029] (1) Sample preparation: The corresponding volumes of water phase and oil phase (MCT) were mixed in proportion (total volume 30 mL), and a certain mass of corncob CNC and CNF (1:1) solid samples were added;

[0030] (2) Shear test: using FB-110J high-speed shearing machine, stirring at 12000 rpm for 2 min, with a 1-min operation and a 30-s pause;

[0031] (3) Prepare emulsion samples with different parameters to study the volume fraction of oil Effects on the properties of emulsions: When the concentration of nanocellulose particles was fixed at 1.0% (w / v), different oil phase volume ratios ( 0.5 and 0.7) samples; To study the effect of nanocellulose concentration, emulsion samples were prepared with different concentrations (0.5%, 1.0% and 1.5% w / v) of cellulose particles at a fixed oil phase volume ratio of 0.5;

[0032] (4) Rheological properties analysis: The rheological properties of the emulsion samples were measured at 20 °C using an AR-500 rheometer. The rotor of the rheometer was a 40 mm diameter parallel plate. The shear rate (0.1 to 100 s -1) and apparent viscosity (η). The linear viscoelastic region (LVR) was obtained by strain sweep testing (frequency 1 Hz, strain range 0.1-100%). All dynamic tests were performed in LVR (strain = 1%). Frequency sweeps were performed in the range of 0.1 to 100 rad / s to obtain the storage modulus (G′) and loss modulus (G″). A 5 min equilibrium was performed before each measurement.

[0033] Step 6: Preparation and testing of corncob-based pesticide droplet stabilizer, specifically including the following.

[0034] (1) mixing solid pesticide granules with distilled water in a certain proportion;

[0035] (2) adding corncob CNC and CNF (1:1) solid samples;

[0036] (3) stirring for 10 minutes;

[0037] (4) Test the stability of pesticide droplets, use Stokes' law to calculate the settling velocity of the droplets, and then evaluate the effect of the stabilizer:

[0038]

[0039] Where v is the droplet settling velocity (m / s), ρ p is the density of the droplet (kg / m 3 ), ρ f is the density of the fluid (kg / m 3 ), g is the acceleration due to gravity (m / s 2 ), d is the diameter of the droplet (m), μ is the viscosity of the fluid (Pa·s);

[0040] (5) If the stabilization effect of the pesticide droplets cannot be achieved, change the ratio parameters of corncob CNC and CNF;

[0041] (6) If the stabilization effect of the pesticide droplets still cannot be achieved after the change, repeat steps 1 to 5 until the parameter requirements are met.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. Using corn cobs, an agricultural waste, as raw materials not only solves the environmental pollution problem caused by corn cob accumulation, but also realizes the recycling of resources. It is in line with the concept of green chemistry and sustainable development, has good environmental benefits and social value, and belongs to "turning waste into treasure";

[0044] 2. The preparation method of the present invention is simple to operate, low in cost, and easy to mass produce. It provides a new type of pesticide droplet stabilizer that is efficient, environmentally friendly, and economical for the pesticide industry, and is expected to be widely used in agricultural production to improve crop yield and quality and promote agricultural production and income increase;

[0045] 3. The cellulose nanocrystals extracted by this method have a high extraction efficiency, with an extraction rate of more than 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Attached Figure 1 Schematic diagram of the overall method steps of the present invention

[0047] Attached Figure 2 This is a schematic diagram of the method for obtaining corncob cellulose of the present invention;

[0048] Attached Figure 3 Schematic diagram of the extraction of cellulose nanocrystals of the present invention;

[0049] Attached Figure 4 Schematic diagram of the extraction of cellulose nanofibers of the present invention;

[0050] Attached Figure 5 It is a schematic diagram of characterization of the corncob nanofiber stabilizer of the present invention;

[0051] Attached Figure 6 This is a schematic diagram of the preparation method of the corncob-based pesticide droplet stabilizer of the present invention;

[0052] Attached Figure 7 Optical microscope images of emulsion samples under different oil phases prepared in Example 1 of the present invention;

[0053] Attached Figure 8 This is a creaming index diagram of emulsion samples with different oil ratios at different storage times prepared in Example 1 of the present invention.

[0054] Attached Fig. 9 These are optical microscope images of emulsions at different nanocellulose concentrations prepared in Example 1 of the present invention.

[0055] Attached Fig.10 This is a milking index diagram of emulsion samples with different nanocellulose concentrations at different storage times prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0057] Example 1: A method for preparing a pesticide droplet stabilizer based on corncobs, see the attached Figure 1 , including the following steps:

[0058] Step 1: Pretreatment of corn cobs, see attached Figure 2 , specifically including the following.

[0059] (1) crushing: put corn cobs with a moisture content of 10% into a blender and chop for 10 minutes;

[0060] (2) filtering, passing the corncob powder through a 35-mesh sieve;

[0061] Step 2: Obtaining corncob cellulose, see attached Figure 2 , specifically including the following.

[0062] (1) Alkali treatment: the pretreated corncob powder was mixed with a 2% sodium hydroxide aqueous solution at a solid-liquid ratio of 1:20 and stirred at 90°C for 4 hours. The porous structure of the corncob can be further optimized by pyrolysis to increase its specific surface area. The optimization of pyrolysis conditions can be guided by the Arrhenius equation:

[0063]

[0064] Where k is the thermal decomposition reaction rate constant, A is the frequency factor, and E a is the activation energy, R is the ideal gas constant, and T is the pyrolysis temperature.

[0065] (2) Remove alkali and wash with distilled water 5 times;

[0066] (3) bleaching the fibers with equal amounts of acetate buffer (2.7% by mass NaOH and 7.5% by mass acetic acid) and chlorite (1.7% by mass NaClO2 solution) at 80°C for 6 hours;

[0067] (4) Purification: The bleached fiber is repeatedly washed in distilled water until the pH value of the fiber becomes 7, and then dried in an air circulation drying oven at 40°C for 24 hours. The material obtained after purification is treated pure cellulose.

[0068] Step 3: Extraction of cellulose nanocrystals, see Appendix Figure 3 , specifically including the following.

[0069] (1) Extracting nanocrystals: Each gram of pure cellulose sample was placed in 15 mL of H2SO4 (9.17 mol / L) for hydrolysis. The hydrolysis was carried out at 45 °C for 1 hour with continuous stirring.

[0070] (2) dilution and acid removal: dilute the suspension 10 times with cold water to stop the hydrolysis reaction, and centrifuge at 7500 rpm for more than 10 minutes to remove excess acid;

[0071] (3) Dialysis: dialyze the precipitate with tap water to remove inactive sulfate groups, salts, and soluble sugars until the pH reaches 7;

[0072] (4) Drying: The dialyzate was ultrasonically treated for 10 minutes and vacuum dried to obtain corncob cellulose nanocrystals.

[0073] Step 4: Extraction of cellulose nanofibers, see Appendix Figure 4 , specifically including the following.

[0074] (1) Tetramethylpiperidine treatment: corncob cellulose was suspended in water containing TEMPO (1 mmol / L) and sodium bromide (10 mmol / L) and stirred continuously at a liquid-to-solid ratio of 100;

[0075] (2) adjusting the pH value by adding NaOH to adjust the pH of the reaction system to 10.5;

[0076] (3) Tetramethylpiperidine-mediated oxidation: At 25 °C, an aqueous solution of NaClO (10 mmol / g cellulose) was added to initiate TEMPO-mediated oxidation, followed by the addition of NaOH to maintain the pH at 10.5 for 2 h.

[0077] (4) washing, repeatedly adding ethanol 6 times to obtain a solid substance, and then washing it with deionized water 10 times;

[0078] (5) Centrifugal drying: The solid was centrifuged (8000 rpm, 5 minutes) and then vacuum dried for 48 hours to obtain corncob cellulose nanofibers.

[0079] Step 5: Characterization of corncob nanofiber stabilizer, see Appendix Figure 5 , specifically including the following.

[0080] (1) Sample preparation: The corresponding volumes of water phase and oil phase (MCT) were mixed in proportion (total volume 30 mL), and a certain mass of corncob CNC and CNF (1:1) solid samples were added;

[0081] (2) Shear test: using FB-110J high-speed shearing machine, stirring at 12000 rpm for 2 min, with a 1-min operation and a 30-s pause;

[0082] (3) Prepare emulsion samples with different parameters to study the volume fraction of oil Effects on the properties of emulsions: When the concentration of nanocellulose particles was fixed at 1.0% (w / v), different oil phase volume ratios ( 0.5 and 0.7) samples; To study the effect of nanocellulose concentration, emulsion samples were prepared with different concentrations (0.5%, 1.0% and 1.5% w / v) of cellulose particles at a fixed oil phase volume ratio of 0.5;

[0083] (4) Rheological properties analysis: The rheological properties of the emulsion samples were measured at 20 °C using an AR-500 rheometer. The rotor of the rheometer was a 40 mm diameter parallel plate. The shear rate (0.1 to 100 s -1 ) and apparent viscosity (η). The linear viscoelastic region (LVR) was obtained by strain sweep testing (frequency 1 Hz, strain range 0.1-100%). All dynamic tests were performed in LVR (strain = 1%). Frequency sweeps were performed in the range of 0.1 to 100 rad / s to obtain the storage modulus (G′) and loss modulus (G″). A 5 min equilibrium was performed before each measurement.

[0084] Step 6. Preparation and testing of corncob-based pesticide droplet stabilizer, see Appendix Figure 6 , specifically including the following.

[0085] (1) mixing solid pesticide granules with distilled water in a certain proportion;

[0086] (2) adding corncob CNC and CNF (1:1) solid samples;

[0087] (3) stirring for 10 minutes;

[0088] (4) Test the stability of pesticide droplets, use Stokes' law to calculate the settling velocity of the droplets, and then evaluate the effect of the stabilizer:

[0089]

[0090] Where v is the droplet settling velocity (m / s), ρ p is the density of the droplet (kg / m 3 ), ρ f is the density of the fluid (kg / m 3 ), g is the acceleration due to gravity (m / s 2 ), d is the diameter of the droplet (m), μ is the viscosity of the fluid (Pa·s);

[0091] (5) If the stabilization effect of the pesticide droplets cannot be achieved, change the ratio parameters of corncob CNC and CNF;

[0092] (6) If the stabilization effect of the pesticide droplets still cannot be achieved after the change, repeat steps 1 to 5 until the parameter requirements are met.

[0093] The optical microscope images of the emulsion samples with different oil ratios at a fixed nanocellulose concentration (mass percentage of 1%) prepared by the above method are shown in the attached figure. Figure 7 As shown in (a: oil phase ratio is 0.3; b: oil phase ratio is 0.5; c: oil phase ratio is 0.7); the creaming index under different storage time is shown in the attached Figure 8 shown.

[0094] The optical microscope images of the emulsions with different nanocellulose concentrations prepared by the above method at a fixed oil phase volume ratio (φ=0.5) are shown in the attached figure. Fig. 9 As shown in (a: nanocellulose concentration is 0.5%; b: nanocellulose concentration is 1.0%; c: nanocellulose concentration is 1.5%); the creaming index under different storage time is shown in the attached Fig.10 shown.

Claims

1. A method for preparing a pesticide droplet stabilizer based on corncobs, the steps of the preparation method are as follows: Step 1: pretreatment of corn cobs, specifically comprising the following steps: (1) crushing: putting corn cobs with a moisture content of less than 20% into a blender and chopping for 10 minutes; (2) filtering, passing the corncob powder through a 35-mesh sieve; Step 2: obtaining corncob cellulose; Step 3: Extraction of cellulose nanocrystals; Step 4: Extraction of cellulose nanofibers; Step 5, characterization of corncob nanofiber stabilizer; Step 6. Preparation and testing of corncob-based pesticide droplet stabilizer.

2. The method for preparing a pesticide droplet stabilizer based on corncobs according to claim 1, characterized in that: The specific steps of obtaining corncob cellulose in step 2 are as follows: (1) Alkali treatment: the pretreated corncob powder is mixed with a 2% sodium hydroxide aqueous solution at a solid-liquid ratio of 1:20, and stirred at 90-100° C. for 4-6 hours. The porous structure of the corncob is further optimized by temperature pyrolysis. The optimization of the pyrolysis conditions is guided by the Arrhenius equation: Where k is the thermal decomposition reaction rate constant, A is the frequency factor, and E a is the activation energy, R is the ideal gas constant, and T is the pyrolysis temperature; (2) Remove alkali by washing with distilled water 5 to 8 times; (3) bleaching the fibers with equal amounts of acetate buffer (2.7% by mass NaOH and 7.5% by mass acetic acid) and chlorite (1.7% by mass NaClO2 solution) at 80°C for 6 to 8 hours; (4) Purification: The bleached fiber is repeatedly washed in distilled water until the pH value of the fiber becomes 7, and then dried in an air circulation drying oven at 40°C for 24 hours. The material obtained after purification is treated pure cellulose.

3. The method for preparing a pesticide droplet stabilizer based on corncobs according to claim 1, characterized in that: The specific steps of extracting cellulose nanocrystals in step 3 are as follows: (1) Extracting nanocrystals: Each gram of pure cellulose sample was placed in 15 mL of H2SO4 (9.17 mol / L) for hydrolysis. The hydrolysis was carried out at 45°C for 1 to 2 hours with continuous stirring. (2) dilution and acid removal: dilute the suspension 10 times with cold water to stop the hydrolysis reaction, and centrifuge at 7500 rpm for more than 10 minutes to remove excess acid; (3) Dialysis: dialyze the precipitate with tap water to remove inactive sulfate groups, salts, and soluble sugars until the pH reaches 7; (4) Drying: The dialyzate was ultrasonically treated for 10 minutes and vacuum dried to obtain corncob cellulose nanocrystals.

4. The method for preparing a corncob-based pesticide droplet stabilizer according to claim 1, characterized in that: The specific steps of extracting cellulose nanofibers in step 4 are as follows: (1) Tetramethylpiperidine treatment: corncob cellulose was suspended in water containing TEMPO (1 mmol / L) and sodium bromide (10 mmol / L) and stirred continuously at a liquid-to-solid ratio of 100 to 120; (2) adjusting the pH value by adding NaOH to adjust the pH of the reaction system to 10.5; (3) Tetramethylpiperidine-mediated oxidation: At 25 °C, an aqueous solution of NaClO (10 mmol / g cellulose) was added to initiate TEMPO-mediated oxidation, followed by the addition of NaOH to maintain the pH at 10.5 for 2 h. (4) washing, repeatedly adding ethanol 6 times to obtain a solid substance, and then washing it with deionized water 10 times; (5) Centrifugal drying: The solid was centrifuged (8000 rpm, 5 minutes) and then vacuum dried for 48 hours to obtain corncob cellulose nanofibers.

5. The method for preparing a corncob-based pesticide droplet stabilizer according to claim 1, characterized in that: The specific steps of characterizing the corncob nanofiber stabilizer in step 5 are as follows: (1) Sample preparation: The corresponding volumes of water phase and oil phase (MCT) were mixed in proportion (total volume 30 mL), and a certain mass of corncob CNC and CNF (1:1) solid samples were added; (2) Shear test: using FB-110J high-speed shearing machine, stirring at 12000 rpm for 2 min, with a 1-min operation and a 30-s pause; (3) Prepare emulsion samples with different parameters to study the volume fraction of oil Effects on the properties of emulsions: When the concentration of nanocellulose particles was fixed at 1.0% (w / v), different oil phase volume ratios ( 0.5 and 0.7) samples; emulsion samples were prepared with different concentrations (0.5%, 1.0% and 1.5% w / v) of cellulose particles at a fixed oil phase volume ratio of 0.5; (4) Rheological properties analysis: The rheological properties of the emulsion samples were measured at 20 °C using an AR-500 rheometer. The rotor of the rheometer was a 40 mm diameter parallel plate. The shear rate (0.1 to 100 s -1 ) and apparent viscosity (η). The linear viscoelastic region (LVR) was obtained by strain sweep testing (frequency 1 Hz, strain range 0.1-100%). All dynamic tests were performed in LVR (strain = 1%). Frequency sweeps were performed in the range of 0.1 to 100 rad / s to obtain the storage modulus (G′) and loss modulus (G″). A 5 min equilibrium was performed before each measurement.

6. The method for preparing a corncob-based pesticide droplet stabilizer according to claim 1, characterized in that: The specific steps for preparing and testing the corncob-based pesticide droplet stabilizer in step 6 are as follows: (1) mixing solid pesticide granules with distilled water in a certain proportion; (2) adding corncob CNC and CNF (1:1) solid samples; (3) stirring for 10 minutes; (4) Test the stability of pesticide droplets, use Stokes' law to calculate the settling velocity of droplets, and evaluate the effect of stabilizers: Where v is the droplet settling velocity (m / s), ρ p is the density of the droplet (kg / m 3 ), ρ f is the density of the fluid (kg / m 3 ), g is the acceleration due to gravity (m / s 2 ), d is the diameter of the droplet (m), μ is the viscosity of the fluid (Pa·s); (5) If the stabilization effect of the pesticide droplets cannot be achieved, change the ratio parameters of corncob CNC and CNF; (6) If the stabilization effect of the pesticide droplets still cannot be achieved after the change, repeat steps 1 to 5 until the parameter requirements are met.

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