Method for supplementing nitrogen element to wetland ecosystem based on quartz microsphere loaded nano photocatalyst

Abstract

The invention discloses a method for supplementing nitrogen element to a wetland ecosystem based on a quartz microsphere loaded nano photocatalyst, which comprises the following steps: dissolving tetraethoxysilane in water, adding a pore-forming agent and a dispersing agent, adjusting the pH value to 2-3, and uniformly stirring to form sol; drying the sol, and calcining the sol for 2-4 hours at the temperature of 600-1100 DEG C to obtain microspheres; dispersing a nano photocatalyst in an alcoholic solution, adding the microspheres, uniformly stirring under a hydrothermal condition of 50-80 DEG C, washing, filtering and drying to obtain quartz microspheres loaded with the nano photocatalyst; and dissolving the prepared quartz microspheres in water, performing rotary stirring to prepare a supersaturated solution, and spraying the supersaturated solution on the surface of the wetland. The photocatalyst is loaded on the quartz microspheres as much as possible, under the illumination of natural light, nitrogen in the atmosphere can be stably converted into an inorganic nitrogen supply source of the wetland for a long time, and the content of nitrogen on the surface of the wetland is effectively increased.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic nitrogen production, and particularly relates to a method for supplementing nitrogen elements in wetland ecosystems based on quartz microsphere-supported nano-photocatalysts. Background Art

[0002] Wetlands are unique ecosystems on Earth and play a crucial role in maintaining biodiversity, enhancing carbon sinks, and improving ecosystem functions. Wetland protection work is of great significance. Nitrogen, as a major nutrient element essential for organisms, is also an important participant in the wetland material cycle and the main limiting factor for vegetation growth, directly affecting the productivity level and ecosystem stability of wetland ecosystems.

[0003] In wetland ecosystems, nitrogen exists in the forms of organic nitrogen and inorganic nitrogen. Among them, the inorganic nitrogen that can be absorbed and utilized by plants only accounts for less than 2% of the total soil nitrogen. Organic nitrogen in the soil must undergo mineralization by soil microorganisms to be converted into a form that can be absorbed by plants and ultimately utilized by plants. Therefore, the productivity of plants in wetland ecosystems is significantly restricted by the mineralization and efficiency of organic nitrogen in wetland ecosystems.

[0004] A large amount of exogenous nitrogen input can increase vegetation productivity. However, the efficiency of improving vegetation productivity by a large amount of nitrogen input is limited. The various nitrogen cycle processes and nitrogen form conversions involved after this exogenous nitrogen input instead cause a series of ecological security problems such as soil acidification, biodiversity decline, water eutrophication, and increased greenhouse gas emissions, making wetland protection and sustainable development face huge challenges. The ecological security problems caused by nitrogen fertilizer application lead to the degradation and reduced stability of wetland ecosystems. Due to the complexity in the nitrogen cycle process of wetland ecosystems, the wetland ecosystem is unstable.

[0005] In order to further improve the productivity of wetland ecosystems without causing ecological environment problems, it is urgent to find relatively safe, stable, and effective methods and technologies for supplying nitrogen that can be utilized by wetland ecosystem plants. Nitrogen in the atmosphere accounts for up to 78%, which can stably and continuously provide a nitrogen source. In view of this, converting nitrogen in the atmosphere into an inorganic nitrogen supply source for wetlands can achieve a sustainable model for improving the ecological functions of wetland ecosystems. Summary of the Invention

[0006] Object of the Invention: The present invention provides a method for using a photocatalyst to convert nitrogen in the atmosphere into an inorganic nitrogen supply source for wetlands, and the photocatalyst relies on a quartz microsphere carrier to be able to continuously and stably convert nitrogen in the atmosphere.

[0007] Technical Solution: The method for supplementing nitrogen elements in wetland ecosystems based on quartz microsphere-supported nano-photocatalysts of the present invention includes the following steps:

[0008] (1) Dissolve tetraethyl orthosilicate in water, add a dispersant, and adjust the pH value to 2 - 3. Stir evenly to form a sol; after drying the sol, calcine it at 600 - 1100 °C for 2 - 4 h to obtain microspheres.

[0009] (2) Disperse the nano photocatalyst in an alcohol solution, add the microspheres, and stir evenly under hydrothermal conditions at 50 - 80 °C. After washing, filtering, and drying, quartz microspheres loaded with the nano photocatalyst are obtained.

[0010] (3) Dissolve the quartz microspheres prepared in step (2) in water, rotate and stir to prepare a supersaturated solution, and spray it on the surface of the wetland after filtration.

[0011] The present invention relies on quartz microspheres capable of transmitting ultraviolet rays, and is formulated into a mixed solution with water under certain temperature and stirring conditions, and dispersed on the surface of the wetland. After a period of time under natural sunlight, it can effectively increase the nitrogen element content on the surface of the wetland. And the present invention modifies the structure of the quartz microspheres, that is, a dispersant is introduced during the preparation process, which not only avoids the aggregation between the silica gel particles formed by the hydrolysis of tetraethyl orthosilicate, makes it shrink more evenly during drying and calcination, reduces surface defects, and improves the sphericity and surface quality of the microspheres; at the same time, based on the pores formed by the decomposition of the pore-forming agent, the addition of the dispersant can further thermally decompose to generate gas in the silica gel system during the subsequent drying and calcination processes. The pores formed by this thermal decomposition can not only further increase the porosity, but also connect the pores formed by the decomposition of the pore-forming agent to form large pores, thereby preparing quartz microspheres with a size pore gradation, effectively increasing the subsequent loading amount of the photocatalyst on the surface and in the pores of the quartz microspheres, improving the durability, and being able to stably convert nitrogen in the air into inorganic nitrogen for a long time.

[0012] Furthermore, in step (1) of the method of the present invention, the addition amount of the dispersant is 1 - 5% of the mass of tetraethyl orthosilicate, and it includes ethylene glycol, polyacrylamide, or methyl pentanol.

[0013] Furthermore, in step (1) of the method of the present invention, the addition amount of the pore-forming agent is 1 - 5% of the mass of tetraethyl orthosilicate, and it includes ammonium carbonate or ammonium bicarbonate.

[0014] Furthermore, in steps (1) and (2) of the method of the present invention, the drying is carried out at 100 - 120 °C for 10 - 14 h.

[0015] Furthermore, in step (2) of the method of the present invention, the nano catalyst is TiO2, ZnO, Ga2O3, Fe2O3, BiO, or C3N4.

[0016] Furthermore, in step (2) of the method of the present invention, the mass ratio of the nano-catalyst to the microspheres is 1:(3 - 5).

[0017] Furthermore, in step (3) of the method of the present invention, the filtration is carried out on the supersaturated mixed solution using a sand core funnel with a pore size of 2 - 5 μm, and the number of filtration times is 1 - 4 times.

[0018] Furthermore, in step (3) of the method of the present invention, the rotational speed of the rotary stirring is 500 - 3000 rpm, and the time is 1 - 20 h.

[0019] Excellent effects: Compared with the prior art, the significant advantages of the present invention are as follows: By loading as much photocatalyst as possible onto quartz microspheres, this method can stably convert atmospheric nitrogen into a wetland inorganic nitrogen supply source under natural light illumination for a long time, effectively increasing the nitrogen content on the wetland surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Diagram of the milky white mixed liquid prepared in Example 1 of the present invention;

[0021] Figure 2 Diagram of the milky white mixed liquid prepared in Example 2 of the present invention;

[0022] Figure 3 Diagram of the milky white mixed liquid prepared in Example 3 of the present invention;

[0023] Figure 4 Diagram of the milky white mixed liquid prepared in Example 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The technical solution of the present invention will be further described in detail below with reference to the drawings and examples.

[0025] It should be noted that the raw materials used in the present invention can all be purchased commercially. The following examples use TiO₂ nano-photocatalyst for experiments to verify the technical effects of the present invention. However, using ZnO, Ga₂O₃, Fe₂O₃, BiO or C₃N₄ photocatalyst still has the ability to convert atmospheric nitrogen into nitrogen.

[0026] Example 1

[0027] The method for supplementing nitrogen elements in a wetland ecosystem based on quartz microsphere-supported nano-photocatalyst in this Example 1 includes the following steps:

[0028] (1) Dissolve tetraethyl orthosilicate in water, add ammonium carbonate accounting for 3% of the mass of tetraethyl orthosilicate and ethylene glycol accounting for 3% of the mass of tetraethyl orthosilicate respectively, and adjust the pH value to about 2, then stir evenly to form a sol; dry the sol at 110 °C for 12 h and then calcine it at 900 °C for 3 h to obtain microspheres;

[0029] (2) Disperse the nano-photocatalyst TiO2 in ethanol, add microspheres, and the addition amount is in a mass ratio of 4:1 to the nano-photocatalyst TiO2, and stir for 3 h under hydrothermal conditions at 60 °C, then wash, filter and dry to obtain quartz microspheres loaded with nano-photocatalyst;

[0030] (3) At 25 °C, dissolve the quartz microspheres prepared in step (2) in water according to a mass-volume ratio of 0.6 g / L, and rotate and stir at a rotation speed of 2000 rpm for 8 h to obtain an over-opaque white mixed liquid, as Figure 1 shown. After filtering the supersaturated mixed solution with a sand core funnel with a pore size of 2 - 5 μm, evenly distribute 100 g of wetland soil in a glass container with a diameter of 6.5 cm and a height of 7 cm, and then spray the filtered solution evenly on the surface of the wetland soil at a rate of 10.6 g / m 2 standard, keep the humidity of the soil, and irradiate the sample with simulated sunlight.

[0031] Example 2

[0032] The method for supplementing nitrogen elements in the wetland ecosystem based on quartz microspheres loaded with nano-photocatalyst in this Example 2 includes the following steps:

[0033] (1) Dissolve tetraethyl orthosilicate in water, add ammonium carbonate accounting for 4% of the mass of tetraethyl orthosilicate and ethylene glycol accounting for 4% of the mass of tetraethyl orthosilicate respectively, and adjust the pH value to about 3, then stir evenly to form a sol; dry the sol at 110 °C for 12 h and then calcine it at 1000 °C for 3 h to obtain microspheres;

[0034] (2) Disperse the nano-photocatalyst TiO2 in ethanol, add microspheres, and the addition amount is in a mass ratio of 4:1 to the nano-photocatalyst TiO2, and stir for 3 h under hydrothermal conditions at 60 °C, then wash, filter and dry to obtain quartz microspheres loaded with nano-photocatalyst;

[0035] (3) At 10 °C, dissolve the quartz microspheres prepared in step (2) in water according to a mass-volume ratio of 0.6 g / L, and rotate and stir at a rotation speed of 1000 rpm for 8 h to obtain an over-opaque white mixed liquid as Figure 2As shown, after filtering the supersaturated mixed solution with a sand core funnel with a pore size of 2 - 5 μm, 100 g of wetland soil was evenly distributed in a glass container with a diameter of 6.5 cm and a height of 7 cm, and then the filtered solution was sprayed evenly on the surface of the wetland soil at a rate of 10.6 g / m 2 standard to keep the soil moist, and the sample was irradiated with simulated sunlight.

[0036] Comparative Example 1

[0037] The basic steps are the same as those in Example 1, except that the photocatalyst is directly mixed with water to prepare a mixed solution, which includes the following steps: at 25 °C, the photocatalyst is dissolved in water according to the mass - volume ratio of 0.1 g:50 ml, and stirred at a rotational speed of 1000 rpm for 8 h to obtain a mixed liquid. After filtering the supersaturated mixed solution with a sand core funnel with a pore size of 2 - 5 μm, 100 g of wetland soil was evenly distributed in a glass container with a diameter of 6.5 cm and a height of 7 cm, and then the filtered solution was sprayed evenly on the surface of the wetland soil at a rate of 10.6 g / m 2 standard to keep the soil moist, and the sample was irradiated with simulated sunlight.

[0038] Comparative Example 2

[0039] The basic steps are the same as those in Example 1, except that the preparation process of the quartz microspheres is different, which includes the following steps:

[0040] (1) Tetraethyl orthosilicate was dissolved in water, ammonium carbonate accounting for 3% of the mass of tetraethyl orthosilicate was added, and the pH value was adjusted to about 2, and stirred evenly to form a sol; the sol was dried at 110 °C for 12 h and then calcined at 900 °C for 3 h to obtain microspheres;

[0041] (2) The nano - photocatalyst TiO2 was dispersed in ethanol, and microspheres were added with the mass ratio of the added amount to the nano - photocatalyst TiO2 being 4:1, and stirred at 60 °C under hydrothermal conditions for 3 h, and then washed, filtered, and dried to obtain quartz microspheres loaded with nano - photocatalysts;

[0042] (3) At 25 °C, the quartz microspheres prepared in step (2) were dissolved in water according to the mass - volume ratio of 0.1 g:50 ml, and stirred at a rotational speed of 1000 rpm for 8 h to obtain an off - white milky mixed liquid. After filtering the supersaturated mixed solution with a sand core funnel with a pore size of 2 - 5 μm, 100 g of wetland soil was evenly distributed in a glass container with a diameter of 6.5 cm and a height of 7 cm, and then the filtered solution was sprayed evenly on the surface of the wetland soil at a rate of 10.6 g / m 2 standard to keep the soil moist, and the sample was irradiated with simulated sunlight.

[0043] Efficacy detection - Concentration determination

[0044] The ammonia nitrogen concentration was measured on the wetland soil surface sprayed with the photocatalyst in Example 1 and Example 2, Comparative Example 1 and Comparative Example 2 of the present invention, and the obtained results are shown in Table 1 below.

[0045] Table 1 Ammonia nitrogen concentration on the wetland soil surface of Example 1 and Example 2, Comparative Example 1 and Comparative Example 2 (mg / L)

[0046]

[0047] Combined with the ammonia nitrogen concentration at different time periods in Example 1 and the comparative examples in Table 1, it can be seen that the quartz microspheres prepared by the preparation process of the present invention are loaded with the nano-photocatalyst, and the loading amount is more under the same concentration conditions. Furthermore, more amount is released during application, and the photocatalyst conversion efficiency is high. Compared with Comparative Example 1, without the aid of quartz microspheres for loading, the quartz microspheres that can transmit ultraviolet light further promote the photocatalytic ability.

[0048] Example 3

[0049] The method for supplementing nitrogen elements in the wetland ecosystem based on the quartz microsphere loaded with nano-photocatalyst in this Example 3 includes the following steps:

[0050] (1) Dissolve tetraethyl orthosilicate in water, add ammonium carbonate accounting for 2% of the mass of tetraethyl orthosilicate and ethylene glycol accounting for 2% of the mass of tetraethyl orthosilicate respectively, and adjust the pH value to about 2, and stir evenly to form a sol; dry the sol at 110 °C for 12 h and then calcine it at 800 °C for 4 h to obtain microspheres;

[0051] (2) Disperse the nano-photocatalyst TiO2 in ethanol, add microspheres, and the addition amount is in a mass ratio of 3:1 to the nano-photocatalyst TiO2, and stir for 4 h under hydrothermal conditions at 70 °C, and then wash, filter and dry to obtain quartz microspheres loaded with nano-photocatalyst;

[0052] (3) At 10 °C, dissolve the quartz microspheres prepared in step (2) in water according to a mass-volume ratio of 0.6 g / L, and rotate and stir at a rotation speed of 1000 rpm for 12 h to obtain an over-milky white mixed liquid, as Figure 3 shown. After filtering the supersaturated mixed solution with a sand core funnel with a pore size of 2 - 5 μm, evenly distribute 100 g of wetland soil in a glass container with a diameter of 6.5 cm and a height of 7 cm, and then spray the filtered solution onto the wetland soil surface uniformly at a rate of 10.6 g / m 2 standard, keep the humidity of the soil, and irradiate the sample with simulated sunlight.

[0053] Example 4

[0054] This Example 4 is a method for supplementing nitrogen elements in a wetland ecosystem based on quartz microspheres loaded with nano-photocatalysts, including the following steps:

[0055] (1) Dissolve tetraethyl orthosilicate in water, add ammonium carbonate accounting for 5% of the mass of tetraethyl orthosilicate and ethylene glycol accounting for 5% of the mass of tetraethyl orthosilicate respectively, and adjust the pH value to about 3, then stir evenly to form a sol; after drying the sol at 110 °C for 12 h, calcine it at 1100 °C for 2 h to obtain microspheres;

[0056] (2) Disperse nano-photocatalyst TiO2 in ethanol, add microspheres with the mass ratio of the addition amount to nano-photocatalyst TiO2 being 5:1, and stir for 4 h under hydrothermal conditions at 55 °C, then wash, filter and dry to obtain quartz microspheres loaded with nano-photocatalysts;

[0057] (3) At 25 °C, dissolve the quartz microspheres prepared in step (2) in water according to the mass-volume ratio of 0.2 g / L, and rotate and stir at a rotation speed of 1000 rpm for 12 h to obtain an over-milky white mixed liquid, as Figure 4 shown. After filtering the supersaturated mixed solution with a sand core funnel with a pore size of 2 - 5 μm, evenly distribute 100 g of wetland soil in a glass container with a diameter of 6.5 cm and a height of 7 cm, then spray the filtered solution evenly on the surface of the wetland soil at a rate of 10.6 g / m 2 standard, keep the humidity of the soil, and irradiate the sample with simulated sunlight.

[0058] Efficacy Detection - Concentration Determination

[0059] Measure the ammonium nitrogen concentration on the surface of the wetland soil sprayed with photocatalyst in Example 3 and Example 4 of the present invention, and the obtained results are shown in Table 2 below.

[0060] Table 2 Ammonium nitrogen concentration on the surface of the wetland soil in Example 3 and Example 4 (mg / L)

[0061]

[0062] By combining Table 1 and Table 2, it can be seen that using the invention of the present invention can increase the ammonium nitrogen concentration on the surface of the wetland soil to 0.35 or above after 6 h, successfully realizing a safe, stable and effective technology for supplying plant-available nitrogen in the wetland ecosystem.

[0063] Except for the above embodiments, adopting the process steps and process parameters defined by the present invention can all achieve the above-mentioned claimed technical effects, and thus will not be listed one by one here.

Claims

1. A method for supplementing nitrogen elements in wetland ecosystems based on quartz microspheres loaded with nano photocatalysts, characterized in that, It includes the following steps: (1) Dissolve tetraethyl orthosilicate in water, add a pore-forming agent and a dispersant, and adjust the pH value to 2-3. Stir evenly to form a sol. After drying the sol, calcine it at 600-1100 °C for 2-4 h to obtain microspheres; (2) Disperse the nano-photocatalyst in an alcohol solution, add the microspheres, and stir evenly under hydrothermal conditions at 50-80 °C. After washing, filtering, and drying, filter to obtain quartz microspheres loaded with the nano-photocatalyst; (3) Dissolve the quartz microspheres prepared in step (2) in water, rotate and stir to prepare a supersaturated solution, and spray it on the surface of the wetland.

2. The method for supplementing nitrogen elements in a wetland ecosystem based on a quartz microsphere-supported nano-photocatalyst according to claim 1, characterized in that In step (1), the addition amount of the dispersant is 1-5% of the mass of tetraethyl orthosilicate, and it includes ethylene glycol, polyacrylamide, or methyl pentanol.

3. The method for supplementing nitrogen elements in a wetland ecosystem based on a quartz microsphere-supported nano-photocatalyst according to claim 1, characterized in that In step (1), the addition amount of the pore-forming agent is 1-5% of the mass of tetraethyl orthosilicate, and it includes ammonium carbonate or ammonium bicarbonate.

4. The method for supplementing nitrogen elements in a wetland ecosystem based on a quartz microsphere-supported nano-photocatalyst according to claim 1, wherein, In steps (1) and (2), the drying is carried out at 100-120 °C for 10-14 h.

5. The method for supplementing nitrogen elements in a wetland ecosystem based on a quartz microsphere-supported nano-photocatalyst according to claim 1, wherein In step (2), the nano-catalyst is TiO2, ZnO, Ga2O3, Fe2O3, BiO, or C3N4.

6. The method for supplementing nitrogen elements in a wetland ecosystem based on a quartz microsphere-supported nano-photocatalyst according to claim 1, wherein In step (2), the mass ratio of the nano-catalyst to the microspheres is 1:(3-5).

7. The method for supplementing nitrogen elements in a wetland ecosystem based on a quartz microsphere-supported nano-photocatalyst according to claim 1, wherein In step (3), the filtration is carried out on the supersaturated mixed solution using a sand core funnel with a pore size of 2-5 μm, and the number of filtration times is 1-4 times.

8. The method for supplementing nitrogen elements in a wetland ecosystem based on a quartz microsphere-supported nano-photocatalyst according to claim 1, characterized in that, In step (3), the rotation speed of the rotation stirring is 500-3000 rpm, and the time is 1-20 h.

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