Green synthesis method and application of nano zinc oxide

Abstract

The invention discloses a green synthesis method and application of nano zinc oxide. The method comprises the following steps: dropwise adding a zinc acetate solution into a hippophae rhamnoides leaf extracting solution under continuous stirring; carrying out magnetic stirring and ultrasonic treatment on the mixed solution at room temperature until the color of the mixed solution is changed from dark color to light color and a fluffy precipitate appears; placing the discolored solution in an incubator for incubation; centrifuging the incubated mixed solution, removing an upper liquid phase, and washing the residual solid part with pure water and absolute ethyl alcohol for three times; and drying the obtained solid part in a drying oven, grinding the product into powder, and calcining in a muffle furnace to obtain white nano zinc oxide powder. The prepared nano zinc oxide has very high photocatalytic efficiency, has a remarkable photocatalytic degradation effect on various dyes and organic pollutants, and can be used as an eco-friendly photocatalyst for purified water and other industrial wastes.

Description

Technical Field

[0001] The invention belongs to the field of chemical synthesis, and specifically relates to a method for green synthesis of nano zinc oxide and application thereof. Background Art

[0002] In the past few decades, research and development in the field of nanotechnology has developed rapidly. Among them, nanomaterials have unique physical and chemical properties that other volume forms do not have, such as small size, larger surface area and quantum confinement, due to their nanosize (diameter between 1nm and 100nm). Nanomaterials with special properties are more reactive to other molecules, which makes them outstanding in environmental applications such as photocatalytic processes, cleaning water pollutants, and assisting plants in mitigating the toxicity of pollutants. This provides a new way to solve the challenges of energy consumption, environmental pollution control and health restoration. The basic properties of good biocompatibility, high activity, low toxicity and chemical stability make nano zinc oxide (ZnO-NPs) widely used in various environmental and biological fields. At present, the synthesis methods of nano zinc oxide mainly include physical and chemical methods, but both methods are harmful to humans and the environment. Therefore, the "green synthesis" method using more environmentally friendly, economical and non-toxic bio-source capping agents has emerged. The present invention mainly uses the leaves of the deciduous shrub plant seabuckthorn to prepare nano zinc oxide by a green reduction method, and studies its size and photocatalytic effect, laying the foundation for its market application. Summary of the invention

[0003] The technical problem to be solved by the present invention is a green synthesis method of nano zinc oxide and explores the application of nano zinc oxide in photocatalysis.

[0004] Plant-mediated synthesis strategies are favored due to their rich biodiversity and safest preparation processes. In addition to ecological safety, atom economy, energy efficiency, and reduced derivatives allow for large-scale production of nanomaterials. Plant-mediated synthesis can be performed in three different ways, namely by using living plants (intracellular), plant extracts (extracellular), and phytochemical methods. The living plant method is a very tedious and expensive method. The phytochemical method is an advanced process that involves more control over the phytochemical properties of the nanoparticles. However, this process requires considerable time to recover the nanoparticles. The mechanism of synthesis of nanoparticles from plant extracts depends on the important role played by phytochemicals such as alkaloids, phenols, and flavonoids.

[0005] Plant extracts act as reducing agents, stabilizers, chelating agents, and capping agents, which contribute to the synthesis and stabilization of nanoparticles. Alkaloids, flavonoids, and phenolic substances in plant extracts have enhanced ability to reduce metal ions. The hydroxyl, carbonyl, amine, and methoxy groups of these substances are the main functional groups responsible for reacting with the precursors to participate in the reduction process of ZnO-NPs. At the same time, they can also act as stabilizers for nanoparticles to prevent further growth and agglomeration.

[0006] Generally speaking, there are three stages in the synthesis of metal nanoparticles from plant extracts: (1) the activation stage (bioreduction of metal ions / salts and nucleation of reduced metal ions), (2) the growth stage (spontaneous association of tiny particles with larger particles) in a process known as Ostwald ripening, and (3) the final stage (determining the final shape of the nanoparticles).

[0007] In order to solve the above technical problems, the present invention provides a green synthesis method of nano zinc oxide, comprising the following steps:

[0008] 1) adding the zinc acetate solution dropwise to the seabuckthorn leaf extract under continuous stirring to adjust the pH; the mixed solution is magnetically stirred and ultrasonically treated at room temperature until the color of the mixed solution changes from dark to light and a fluffy precipitate appears;

[0009] 2) The color-changing solution is placed in a constant temperature box for incubation, the incubated mixed solution is centrifuged, the upper liquid phase is removed, and the remaining solid part is washed three times with pure water and anhydrous ethanol;

[0010] 3) Drying the obtained solid part in an oven, grinding the product into powder, and calcining it in a muffle furnace to obtain nano zinc oxide white powder.

[0011] Wherein, the concentration of the zinc acetate solution in step 1) is 0.1-0.5M, and the volume ratio of the zinc acetate solution to the seabuckthorn extract is 1:1.

[0012] Wherein, the pH in step 1) is adjusted to 8-11.

[0013] Wherein, the magnetic stirring time in step 1) is 10 min, and the ultrasonic treatment time is 30 min.

[0014] Wherein, the temperature of the constant temperature box in step 2) is 37° C., and the incubation time is 1 hour.

[0015] Wherein, the centrifugation condition in step 2) is centrifugation at 10000 rpm for 10 min.

[0016] Wherein, the oven temperature in step 3) is 100°C.

[0017] Wherein, the muffle furnace calcination condition in step 3) is calcination at 700° C. for 2 hours.

[0018] The extract of Chinese seabuckthorn selected by the present invention is rich in alkaloids, phenols and flavonoids phytochemicals, wherein the alkaloid content is 1.321-1.376 mg / g, the polyphenol content is 19.246-19.511 mg / g, and the flavonoid content is 27.509-28.432 mg / g.

[0019] The second technical solution of the present invention is the application of nano zinc oxide synthesized according to the above method in photocatalysis.

[0020] Beneficial effects of the present invention: The preparation method of the present invention is environmentally friendly and economical, and uses extracts of natural products to replace expensive and toxic chemical reducing agents in chemical synthesis methods to reduce or completely eliminate by-products of chemical synthesis and compensate for the adverse effects caused by chemical synthesis.

[0021] 1. Environmentally friendly: The plant reducing agent used in the present invention is sea buckthorn leaf, which has the advantages of large reserves, easy picking and storage, and rich in flavonoids, polyphenols, vitamins and other natural substances. Developing it as a plant reducing agent avoids the use of toxic chemical reducing agents and reduces environmental pollution and ecological risks.

[0022] 2. Functional enhancement: The active ingredients in seabuckthorn leaves can improve the performance of nano zinc oxide. Some of the ingredients, such as phenolic acid and some functional groups of saponin, can also act as stabilizers to prevent nanoparticles from agglomerating to further enhance their performance.

[0023] 3. Controllable cost: The present invention uses seabuckthorn leaves as raw materials, which may be more economical than traditional chemical synthesis methods, and the plant extract used is easy to prepare, usually using water or ethanol as the extraction solvent, and the cost is relatively low.

[0024] The nano zinc oxide prepared by the present invention has high photocatalytic efficiency, has significant photocatalytic degradation effect on various dyes and organic pollutants, and can be used as an eco-friendly photocatalyst for water purification and other industrial wastes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Preparation flow chart of nano zinc oxide;

[0026] Figure 2 UV-visible absorption spectrum scanning of nano zinc oxide prepared under different pH conditions;

[0027] Figure 3 Energy spectrum scanning diagram of nano zinc oxide;

[0028] Figure 4 Energy spectrum scanning diagram of nano zinc oxide;

[0029] Figure 5 SEM electron microscope characterization image of nano zinc oxide in Example 1;

[0030] Figure 6 SEM electron microscope characterization image of nano zinc oxide of comparative example 1;

[0031] Figure 7 SEM electron microscope characterization image of nano zinc oxide in comparative example 2. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. It is not limited to the best implementation mode described, and does not limit the content and protection scope of the present invention. Any product that is the same or similar to the present invention and is obtained under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the protection scope of the present invention.

[0033] Example 1 Preparation of Nano Zinc Oxide

[0034] Step 1: Take 100mL of 0.3M zinc acetate solution and add it dropwise to 100mL of sea buckthorn leaf extract under continuous stirring. Adjust the pH value of the mixture to 11, stir the mixture magnetically for 10min at room temperature after pH adjustment, and treat it ultrasonically for 30min. Keep observing until the color of the mixture changes from dark to light and a fluffy precipitate appears, indicating the formation of ZnO NPs;

[0035] Step 2: Place the color-changing solution in a 37°C incubator and incubate for 1 hour to fully complete the reaction. Centrifuge the incubated mixture at 10,000 rpm for 10 minutes, remove the upper liquid phase, and rinse the remaining solid part with pure water and anhydrous ethanol three times;

[0036] Step 3: The obtained solid part was dried in an oven at 100°C, and the product was ground into powder using a mortar. The obtained product was calcined at 700°C for 2 hours to obtain nano zinc oxide white powder.

[0037] The prepared nano zinc oxide was scanned by UV-visible absorption spectrum, and there was a maximum absorption peak at 380nm, which was the same as previously recorded, see Figure 2 .

[0038] The energy spectrum scanning diagram of the nano zinc oxide of the present invention is shown in Figures 3-4 .

[0039] Depend on Figures 3-4 It can be seen that the sample contains two elements, Zn and O, and the concentration is relatively high, which proves that nano zinc oxide exists and is presented in a high-purity form.

[0040] The SEM electron microscope characterization diagram of the nano zinc oxide of the present invention is shown in Figure 5 , presenting a stable spherical structure.

[0041] Example 2 Preparation of Nano-ZnO

[0042] Step 1: Take 100 mL of 0.3 M zinc acetate solution and add it dropwise to 100 mL of sea buckthorn leaf extract under continuous stirring. Adjust the pH value of the mixture to 10. After adjusting the pH, stir the mixture magnetically for 10 min at room temperature and ultrasonically treat it for 30 min. Keep observing until the color of the mixture changes from dark to light, and a fluffy precipitate appears, indicating the formation of ZnO NPs.

[0043] Step 2: Place the color-changing solution in a 37°C incubator and incubate for 1 hour to fully complete the reaction. Centrifuge the incubated mixture at 10,000 rpm for 10 minutes, remove the upper liquid phase, and rinse the remaining solid part with pure water and anhydrous ethanol three times;

[0044] Step 3: The obtained solid part was dried in an oven at 100°C, and the product was ground into powder using a mortar. The obtained product was calcined at 700°C for 2 hours to obtain nano zinc oxide white powder.

[0045] Example 3 Preparation of Nano-ZnO

[0046] Step 1: Take 100mL of 0.5M zinc acetate solution and add it dropwise to 100mL of sea buckthorn leaf extract under continuous stirring. Adjust the pH value of the mixture to 11, stir the mixture magnetically for 10min at room temperature after pH adjustment, and treat it ultrasonically for 30min. Keep observing until the color of the mixture changes from dark to light, and fluffy precipitates appear, indicating the formation of ZnO NPs;

[0047] Step 2: Place the color-changing solution in a 37°C incubator and incubate for 1 hour to fully complete the reaction. Centrifuge the incubated mixture at 10,000 rpm for 10 minutes, remove the upper liquid phase, and rinse the remaining solid part with pure water and anhydrous ethanol three times;

[0048] Step 3: The obtained solid part was dried in an oven at 100°C, and the product was ground into powder using a mortar. The obtained product was calcined at 700°C for 2 hours to obtain nano zinc oxide white powder.

[0049] Example 4 Preparation of Nano-ZnO

[0050] Step 1: Take 100mL of 0.5M zinc acetate solution and add it dropwise to 100mL of sea buckthorn leaf extract under continuous stirring. Adjust the pH value of the mixture to 10. After adjusting the pH, stir the mixture magnetically for 10min at room temperature and ultrasonically treat it for 30min. Keep observing until the color of the mixture changes from dark to light and a fluffy precipitate appears, indicating the formation of ZnO NPs.

[0051] Step 2: Place the color-changing solution in a 37°C incubator and incubate for 1 hour to fully complete the reaction. Centrifuge the incubated mixture at 10,000 rpm for 10 minutes, remove the upper liquid phase, and rinse the remaining solid part with pure water and anhydrous ethanol three times;

[0052] Step 3: The obtained solid part was dried in an oven at 100°C, and the product was ground into powder using a mortar. The obtained product was calcined at 700°C for 2 hours to obtain nano zinc oxide white powder.

[0053] Comparative Example 1 Preparation of Nano-ZnO

[0054] Step 1: Take 100mL of 0.3M zinc acetate solution and add it dropwise to 100mL of sea buckthorn leaf extract under continuous stirring. Adjust the pH value of the mixture to 8. The pH-adjusted mixture is magnetically stirred for 10min at room temperature and ultrasonically treated for 30min. Keep observing until the color of the mixture changes from dark to light and a fluffy precipitate appears, indicating the formation of ZnO NPs.

[0055] Step 2: Place the color-changing solution in a 37°C incubator and incubate for 1 hour to fully complete the reaction. Centrifuge the incubated mixture at 10,000 rpm for 10 minutes, remove the upper liquid phase, and rinse the remaining solid part with pure water and anhydrous ethanol three times;

[0056] Step 3: The obtained solid part was dried in an oven at 100°C, and the product was ground into powder using a mortar. The obtained product was calcined at 700°C for 2 hours to obtain nano zinc oxide white powder.

[0057] The UV-visible absorption scanning spectrum of the nano zinc oxide prepared in Comparative Example 1 is as follows: Figure 2 As shown, the maximum absorption peak appears at 379 nm and is not obvious.

[0058] The SEM electron microscope characterization of the nano zinc oxide prepared in Comparative Example 1 is as follows Figure 6 As shown, the shape is irregular and the structure is flat.

[0059] Comparative Example 2 Preparation of Nano-ZnO

[0060] Step 1: Take 100mL of 0.3M zinc acetate solution and add it dropwise to 100mL of sea buckthorn leaf extract under continuous stirring. Adjust the pH value of the mixture to 6. After adjusting the pH, stir the mixture magnetically for 10min at room temperature and ultrasonically treat it for 30min. Keep observing until the color of the mixture changes from dark to light and a fluffy precipitate appears, indicating the formation of ZnO NPs.

[0061] Step 2: Place the color-changing solution in a 37°C incubator and incubate for 1 hour to fully complete the reaction. Centrifuge the incubated mixture at 10,000 rpm for 10 minutes, remove the upper liquid phase, and rinse the remaining solid part with pure water and anhydrous ethanol three times;

[0062] Step 3: The obtained solid part was dried in an oven at 100°C, and the product was ground into powder using a mortar. The obtained product was calcined at 700°C for 2 hours to obtain nano zinc oxide white powder.

[0063] The UV-visible absorption scanning spectrum of the nano zinc oxide prepared in Comparative Example 2 is as follows: Figure 2 As shown, the maximum absorption peak appears at 372 nm, which is slightly shifted compared with previous reports.

[0064] The SEM electron microscope characterization of the nano zinc oxide prepared in Comparative Example 2 is as follows Figure 7 As shown, the shapes are irregular, and there is obvious agglomeration between the particles, forming large particles with a layered structure.

[0065] Example Study on the Photocatalytic Performance of Nano-ZnO

[0066] Determination of the removal rate of methylene blue by nano zinc oxide

[0067] Take 50ml of the prepared 5mg / L methylene blue solution in three quartz colorimetric tubes, and use a UV-visible spectrophotometer to measure the initial absorbance of methylene blue at a wavelength of 664nm. Then add 25mg of nano zinc oxide prepared under different pH to the three colorimetric tubes, place the colorimetric tubes in the dark for 30min before irradiation, so that methylene blue and nano zinc oxide reach adsorption-desorption equilibrium, and then irradiate with an 8W ultraviolet lamp (λ=265nm) for 180min, take the upper clear liquid every 30min, centrifuge and measure the absorbance, according to the Lambetr-beer law Calculate the mass concentration of methylene blue.

[0068] Removal rate of methylene blue by green synthesized nano zinc oxide at different pH values ​​(%)

[0069]

[0070] It can be seen from the above table that the photocatalytic performance of Example 1 under the preferred strongly alkaline pH conditions of the present invention is the best. Compared with Comparative Example 1 under weakly alkaline pH conditions and Comparative Example 2 under acidic pH conditions, Example 1 under strongly alkaline pH conditions has the highest removal rate for the dye methylene blue.

[0071] Finally, it should be noted that the above-described embodiments are only examples for the purpose of clarifying the invention, and are not intended to limit the embodiments. Although the invention has been described in detail with reference to the above-described embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the above-described embodiments, or to replace some of the technical features therein with equivalents. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A green synthesis method of nano zinc oxide, characterized in that: The following steps are involved: 1) adding zinc acetate solution dropwise to the seabuckthorn leaf extract under continuous stirring to adjust the pH; The mixture was magnetically stirred and ultrasonically treated at room temperature until the color of the mixture changed from dark to light and a fluffy precipitate appeared; 2) placing the solution obtained in step 1) in a constant temperature box for incubation, centrifuging the incubated mixed solution, removing the upper liquid phase, and washing the remaining solid part with pure water and anhydrous ethanol; 3) drying the obtained solid part in an oven, grinding the product into powder, and calcining in a muffle furnace to obtain nano zinc oxide white powder; The concentration of the zinc acetate solution in step 2) is 0.1-0.5M, and the volume ratio of the zinc acetate solution to the seabuckthorn extract is 1:1; The pH in the step 1) is adjusted to 8-11; The seabuckthorn leaf extract is rich in alkaloids, phenols and flavonoids phytochemicals, wherein the alkaloid content is 1.321-1.376 mg / g, the polyphenol content is 19.246-19.511 mg / g, and the flavonoid content is 27.509-28.432 mg / g.

2. The green synthesis method of nano zinc oxide according to claim 1, characterized in that: The magnetic stirring time in step 2) is 10 min, and the ultrasonic treatment time is 30 min.

3. The green synthesis method of nano zinc oxide according to claim 1, characterized in that: The temperature of the incubator in step 3) is 37° C., and the incubation time is 1 h.

4. The green synthesis method of nano zinc oxide according to claim 1, characterized in that: The centrifugation condition in step 3) is centrifugation at 10000 rpm for 10 min.

5. The green synthesis method of nano zinc oxide according to claim 1, characterized in that: The oven temperature in step 4) is 100°C.

6. The green synthesis method of nano zinc oxide according to claim 1, characterized in that: The muffle furnace calcination condition in step 4) is calcination at 700° C. for 2 hours.

7. Use of nano zinc oxide synthesized according to the method of any one of claims 1 to 6 in photocatalysis.

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