Preparation method of sodium carboxymethyl cellulose coated nano-zinc oxide composite material

Abstract

The invention discloses a preparation method of a sodium carboxymethyl cellulose coated nano-zinc oxide composite material. According to the method, by optimizing a reaction process and adopting a green synthesis route, the problems of poor dispersibility and complex synthesis process of zinc oxide nanoparticles in pesticide application are solved. The uniform and stable composite material is successfully prepared by modifying sodium carboxymethyl cellulose and zinc oxide particles and through post-treatment steps such as ultrasonic dispersion, mild chemical reaction and centrifugal cleaning. The method not only improves the stability of the material, but also reduces the production cost, meets the requirements of environmental protection and sustainable development, and has a better agricultural application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural engineering nanomaterials, and particularly to a preparation method of a composite nanomaterial with sodium carboxymethyl cellulose-coated zinc oxide nanoparticles. Background Art

[0002] Under the background of intensified global climate change and resource scarcity, the large-scale application of traditional pesticides has triggered multiple ecological challenges such as soil and water pollution and pest resistance. Taking some pesticides as an example, their long-term accumulation in the environment not only forms residues, but also destroys the soil microbial ecosystem and damages soil health. There is an urgent need to develop new pesticide alternatives. As a potential solution, engineering nanomaterials can precisely release active ingredients, extend the efficacy of pesticides, and reduce the environmental burden. Currently, the synthesis methods of nanomaterials are complex, involving multiple-step reactions, and green synthesis is not yet perfect, still suffering from environmental pressure and energy consumption problems.

[0003] Zinc oxide (ZnO) nanoparticles are widely used in agriculture due to their broad-spectrum antibacterial properties. However, due to their small nanosize, they are prone to aggregation and have insufficient stability, thus affecting the efficacy of pesticides. Researchers have been continuously seeking surface modification strategies to improve the stability and dispersibility of zinc oxide nanoparticles and enhance their efficacy and application potential.

[0004] Sodium carboxymethyl cellulose (CMC-Na), as a natural polymer material, has excellent water solubility, biocompatibility, and good water absorption and swelling properties. It can effectively improve the dispersibility of zinc oxide particles and prevent their aggregation. More importantly, CMC-Na can achieve green synthesis, meeting the requirements of sustainable development. Under mild conditions, CMC-Na can effectively coat zinc oxide, avoiding complex chemical reactions and the use of harmful solvents in traditional synthesis processes. Therefore, developing an engineered agricultural chemical nanoparticle coated with CMC-Na can not only improve its utilization efficiency in agriculture, reduce energy consumption, but also reduce environmental pollution and promote the development of green agriculture. Summary of the Invention

[0005] The present invention proposes an innovative preparation technology for zinc oxide nanoparticles, aiming to overcome the problems of insufficient dispersibility and cumbersome synthesis process of zinc oxide nanoparticles in pesticide use in the prior art. By streamlining the reaction steps, we use sodium carboxymethyl cellulose (CMC-Na) to coat zinc oxide, effectively improving its dispersibility, optimizing the synthesis process, reducing energy consumption and environmental pollution. This environmentally friendly green synthesis technology abandons complex reactions and harmful solvents, bringing a more efficient and green new pesticide carrier material to the agricultural field.

[0006] To achieve the above object, the present invention provides the following technical solutions: A preparation method of a sodium carboxymethyl cellulose-coated zinc oxide nanocomposite, comprising the following steps: Step S1: Weigh 0.5 - 2.5 parts of CMC-Na and add it to 100 parts of ultrapure water. Use an acetic acid solution with a concentration of 10 - 20% to adjust the pH value of the solution to 4.5 - 5.5.

[0007] Step S2: At 25 - 30 °C, use a magnetic stirrer to stir and react. The stirring rate is 200 - 500 rpm, and the reaction time is 10 - 30 minutes to ensure that the CMC-Na molecular chain is moderately broken. The modified CMC-Na has higher hydrophilicity and can better coat zinc oxide nanoparticles.

[0008] Step S3: Preferably, use a membrane with a pore size of 100 - 1000 Daltons to filter and remove the excess acidic substances and small molecule impurities in the above solution to obtain a modified CMC-Na solution.

[0009] Step S4: Weigh 5 - 25 parts of zinc oxide (ZnO) and add it to 100 parts of ultrapure water. Use ammonia water with a concentration of 10 - 20% to adjust the pH value of the solution to 8.0 - 9.0.

[0010] Step S5: Add 2 parts of cetyltrimethylammonium bromide (CTAB, concentration 0.01 - 0.05%) to the ZnO solution for surface modification.

[0011] Step S6: Under the stirring condition of 150 - 200 rpm, heat the solution to 40 - 50 °C, and then use an ultrasonic disperser with a power of 200W and a frequency of 20 kHz to process for 10 - 30 minutes.

[0012] Step S7: Preferably, after the reaction is completed, use a membrane with a pore size of 100 - 1000 Daltons to filter and remove the surfactant and unreacted substances to obtain a modified ZnO nanoparticle solution.

[0013] Step S8: Slowly add the modified CMC-Na solution (concentration 0.5% - 2.5%) to the modified ZnO solution, and use a flow pump to control the flow rate (10 - 15 mL / min) to ensure sufficient contact and compounding between the CMC-Na molecular chain and ZnO particles.

[0014] Step S9: Preferably, during the mixing process, the stirring rate is maintained at 200 - 500 rpm to ensure sufficient contact between the CMC-Na molecular chain and ZnO particles. The reaction temperature is controlled at 25 - 30 °C, and the reaction time is 30 - 60 minutes.

[0015] Step S10: Preferably, a small amount of polyvinyl alcohol (PVA, with a concentration of 0% - 0.05%) is added to the solution to further improve the dispersion of the particles.

[0016] Step S11: Preferably, during the mixing process, ammonia water (with a concentration of 10 - 20%) and acetic acid solution (with a concentration of 10 - 20%) are used to adjust the pH value of the solution to neutral (pH value of 6.5 - 7.5) to avoid too strong interaction between CMC - Na and ZnO, which may affect the composite effect.

[0017] Step S12: Unreacted substances, such as excess stabilizers and uncoated ZnO particle impurities, are removed by high - speed centrifugation (3000 - 5000 rpm, for 10 - 15 minutes).

[0018] Step S13: Preferably, it is repeatedly washed 2 - 4 times with ultrapure water to ensure the purity of the composite and remove residual excess chemical substances.

[0019] Step S14: The centrifuged composite is placed in a freeze - dryer for freeze - drying. The temperature of the freeze - dryer is set at - 40~ - 50°C, the vacuum degree is - 0.08~ - 0.20 MPa, and the freeze - drying time is 24 - 48 hours to ensure complete evaporation of water while maintaining the morphology and dispersion of the CMC - Na coated zinc oxide composite particles.

[0020] Step S15: The obtained dried composite is subjected to particle size screening using a 50 - 500 μm sieve, and the carboxymethyl cellulose sodium coated nano - zinc oxide composite agricultural chemical material with a size of 50 - 500 μm is obtained.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention overcomes the problems of cumbersome reaction steps and high synthesis cost in the prior art, and provides a simplified preparation method for carboxymethyl cellulose sodium (CMC - Na) coated nano - zinc oxide composite agricultural chemical materials. By combining multiple traditional reaction steps into a single operation, this method significantly reduces the reaction time and steps, and improves production efficiency. In addition, the present invention uses mild temperature and moderate stirring rate, which effectively reduces energy consumption. By selecting low - cost chemical reagents such as acetic acid and ammonia water, the present invention further reduces the synthesis cost. In the post - treatment stage, high - efficiency centrifugation and freeze - drying are used to remove impurities and water, simplifying the traditional washing and filtration steps, reducing material waste and labor costs. The simplified and optimized process of the present invention not only reduces production costs, but also improves operation efficiency, and is a green agricultural chemical material with broad industrial application prospects. Description of the Drawings

[0022] Figure 1 Process flow chart for the preparation of sodium carboxymethyl cellulose-coated nano-zinc oxide composite pesticide. Detailed implementation manners Example 1

[0023] This example provides a method for preparing a sodium carboxymethyl cellulose (CMC-Na)-coated nano-zinc oxide composite slow-release pesticide. The specific implementation steps are as follows: (1) Weigh 1.5 parts of CMC-Na and add it to 100 parts of ultrapure water. Use 15% acetic acid solution to adjust the pH value of the solution to 4.8. Place the solution in a 30°C water bath and stir it with a magnetic stirrer at a stirring rate of 300 rpm for 45 minutes.

[0024] (2) Add 10 parts of nano-zinc oxide (ZnO) to 100 parts of ultrapure water. Use 15% ammonia water to adjust the pH value of the solution to 8.5 and stir to ensure that the ZnO particles are completely dispersed and stable.

[0025] (3) Add 2 parts of cetyltrimethylammonium bromide (concentration 0.03%) to the ZnO solution for surface modification. Heat it to 40°C at 150 rpm and treat it with a 200W, 20 kHz ultrasonic disperser for 20 minutes to ensure that the ZnO particles are evenly dispersed.

[0026] (4) Slowly add the modified CMC-Na solution (concentration 1.5%) to the modified ZnO solution. Use a flow pump to control the flow rate at 12 mL / min to ensure that the CMC-Na molecular chains are in full contact with the ZnO particles. Under the stirring condition of 200 rpm, control the reaction temperature at 27°C and the reaction time at 45 minutes.

[0027] (5) Add a small amount of polyvinyl alcohol (PVA, concentration 0.02%) to the composite solution to improve the dispersion of the particles, and continue to stir at 30°C for 30 minutes. Use ammonia water and acetic acid solution to adjust the pH of the solution to 6.8, and perform high-speed centrifugation (3500 rpm, time 12 minutes) to remove unreacted substances and impurities.

[0028] (6) After washing the composite with ultrapure water 3 times, perform particle size screening. Use a 50 μm sieve to screen to obtain a composite material with a uniform particle size range, ensuring that the particle size distribution meets the requirements.

[0029] (7) Subject the screened composite to freeze-drying treatment. Set the temperature of the freeze-dryer to -45°C, the vacuum degree to -0.15 MPa, and the freeze-drying time to 36 hours to obtain a dry sodium carboxymethyl cellulose-coated nano-zinc oxide composite agricultural chemical material. Example 2

[0030] This example provides a preparation method of sodium carboxymethyl cellulose (CMC-Na) coated nano-zinc oxide composite slow-release pesticide. Compared with Example 1, the preparation conditions of the CMC-Na solution are optimized, the dosage of ZnO is increased, the ultrasonic treatment time is increased, and at the same time, the flow rate and stirring rate of the composite process are increased and the freeze-drying time is extended: (1) Weigh 1.0 part of CMC-Na and add it to 100 parts of ultrapure water. Use 12% acetic acid solution to adjust the pH value of the solution to 5.2. Place the solution in a 25°C water bath and stir it with a magnetic stirrer at a stirring rate of 400 rpm for 50 minutes.

[0031] (2) Add 15 parts of nano-zinc oxide (ZnO) to 100 parts of ultrapure water. Use 12% ammonia water to adjust the pH value of the solution to 8.3 and stir to ensure that the ZnO particles are completely dispersed.

[0032] (3) Add 2 parts of cetyltrimethylammonium bromide (concentration 0.04%) to the ZnO solution for surface modification. Heat it to 45°C at 150 rpm and treat it with a ultrasonic disperser at 200W and a frequency of 22 kHz for 25 minutes to ensure that the ZnO particles are evenly dispersed.

[0033] (4) Slowly add the modified CMC-Na solution (concentration 1.0%) to the modified ZnO solution. Use a flow pump to control the flow rate at 13 mL / min to ensure that the CMC-Na molecular chains are in full contact with the ZnO particles. Under the stirring condition of 250 rpm, control the reaction temperature at 28°C and the reaction time at 50 minutes.

[0034] (5) Add a small amount of polyvinyl alcohol (PVA, concentration 0.05%) to the composite solution to improve the dispersibility of the particles, and continue to stir at 28°C for 30 minutes. Use ammonia water and acetic acid solution to adjust the pH of the solution to 6.8, and perform high-speed centrifugation (4000 rpm, time 14 minutes) to remove unreacted substances and impurities.

[0035] (6) After washing the composite with ultrapure water 3 times, perform particle size screening. Use a 100 μm sieve to screen to obtain a composite material with a uniform particle size range.

[0036] (7) Subject the screened composite to freeze-drying treatment. Set the temperature of the freeze-dryer at -50°C, the vacuum degree at -0.20 MPa, and the freeze-drying time at 48 hours to obtain a dry sodium carboxymethyl cellulose coated nano-zinc oxide composite agricultural chemical material.

Claims

1. A method for preparing a composite material of carboxymethyl cellulose sodium (CMC-Na) coated with nano zinc oxide, characterized in that: The following steps are involved: Step S1: add 0.5-2.5 parts of CMC-Na to 100 parts of ultrapure water, adjust the pH value of the solution to 4.5-5.5 with acetic acid solution, and control the pH change rate to 0.1-0.2 units / minute; Step S2: Stirring with a magnetic stirrer at 25-30°C at a rate of 200-500 rpm for 10-30 minutes to ensure that the CMC-Na molecular chain is moderately broken and modified; Step S3: filtering with a membrane having a pore size of 100-1000 Daltons to remove acidic substances and small molecular impurities for 5-10 minutes to obtain a modified CMC-Na solution; Step S4: adding 5-25 parts of nano zinc oxide (ZnO) to 100 parts of ultrapure water, and adjusting the pH value of the solution to 8.0-9.0 using an ammonia solution at a rate of 0.1-0.2 units / minute; Step S5: Add 2 parts of cetyltrimethylammonium bromide (CTAB) to the ZnO solution to ensure that it is completely dissolved for surface modification; Step S6: Heat the solution to 40-50°C under stirring at 150-200 rpm and treat with an ultrasonic disperser at a power of 200 W and a frequency of 20 kHz for 10-30 minutes; Step S7: filtering with a membrane having a pore size of 100-1000 Daltons to remove the surfactant and unreacted substances to obtain a modified ZnO nanoparticle solution; Step S8: slowly add the modified CMC-Na solution (concentration of 0.5%-2.5%) to the modified ZnO solution, and use a flow pump to control the flow rate to 10-15 mL / min to ensure that the CMC-Na molecular chains are fully in contact with the ZnO particles; Step S9: at a stirring rate of 200-500 rpm, the reaction temperature is controlled at 25-30° C., and the reaction time is 30-60 minutes; Step S10: adding polyvinyl alcohol (PVA) to the solution to further improve the dispersibility of the particles; Step S11: During the mixing process, the pH value of the solution is adjusted to neutral (pH 6.5-7.5) using an ammonia solution and an acetic acid solution to avoid excessive interaction between CMC-Na and ZnO, which would affect the composite effect; Step S12: Remove unreacted substances by high-speed centrifugation (3000-5000 rpm, 10-15 minutes); Step S13: Repeatedly wash with ultrapure water 2-4 times to remove excess chemicals; Step S14: placing the complex in a freeze dryer at a temperature of -40 to -50°C, a vacuum degree of -0.08 to -0.20 MPa, and a freeze drying time of 24 to 48 hours; Step S15: The dried composite is subjected to particle size screening using a 50-500 μm sieve to obtain the 50-500 μm sodium carboxymethyl cellulose-coated nano zinc oxide composite agricultural chemical material.

2. The preparation method according to claim 1, wherein The concentration of the acetic acid solution used in step 1 is 10-20%, the concentration of the ammonia water used in step 4 is 10-20%, the concentration of the hexadecyltrimethylammonium bromide used in step 5 is 0.01-0.05%, the concentration of the polyvinyl alcohol used in step 10 is 0%-0.05%, the treatment time is 20 minutes, and the concentrations of the ammonia solution and the acetic acid solution used in step 11 are 10-20%.

3. The preparation method according to claim 1, wherein the power of the ultrasonic disperser is 200 W, the frequency is 20 kHz, and the processing time is 10-30 minutes.

4. The preparation method according to claim 1, wherein the concentration of the modified CMC-Na solution is 0.5%-2.5%.

5. The preparation method according to claim 1, wherein the concentration of nano zinc oxide in the modified ZnO solution is 5-25 parts, and the ultrapure water is 100 parts. The preparation method according to claim 1 , wherein the flow rate of the flow pump is controlled at 10-15 mL / min.

7. The preparation method according to claim 1, wherein the concentration of polyvinyl alcohol (PVA) is 0%-0.05%.

8. The preparation method according to claim 1, wherein the particle size screening in step (15) uses a 50-500 μm sieve.

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