Artificial wetland filler, method for its production and use

Abstract

The application relates to an artificial wetland filler and a preparation method and application thereof, and relates to the field of environmental treatment. The filler is composed of pyrite quantum dots PQD and carbon dots CDs. After the carbon dots CDs are made into powder, the powder is dissolved in distilled water, continuous magnetic stirring and boiling to 100 DEG C are carried out, immediately, pyrite quantum dots PQD with the same mass as the carbon dots CDs are added, stirring is carried out in dark conditions, after centrifugation, washing is carried out with distilled water, vacuum freeze-drying is carried out, and the PQD-CDs composite material is obtained. The filler can significantly enhance the pollutant removal efficiency, and has important significance for the treatment of farmland wastewater. The innovative method contributes to the improvement of the efficiency and sustainable development in the field of water treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental treatment, and particularly relates to an artificial wetland filler, a preparation method and application thereof. BACKGROUND

[0002] The accumulation of nano-plastics in artificial wetland systems can easily lead to complex ecological problems. Studies have shown that nano-plastic exposure can affect the growth and metabolism of plants and microorganisms in artificial wetlands, thereby reducing the biological denitrification efficiency of artificial wetlands. Specifically, nano-plastic exposure can inhibit the biosynthesis of plant photosynthetic pigments and significantly affect the activities of antioxidant enzymes and the content of malondialdehyde (MDA) in plant leaves, thereby negatively affecting photosynthesis in plants. At the same time, nano-plastic internalization can induce microorganisms to produce excessive reactive oxygen species (ROS), further disturbing intracellular metabolism and reducing the activities of key enzymes for nitrogen metabolism (NAR, NIR and AMO), leading to dysfunction of microbial nitrogen metabolism.

[0003] Pyrite (FeS2) can secrete Fe(II) and act as an electron donor to reduce NH4 + to NO3 - , NO2 - and N2 to promote autotrophic denitrification, and can also provide iron ions for microorganisms to promote their growth and metabolism, so it can be used as an artificial wetland substrate for wastewater treatment. However, due to some inherent defects such as small specific surface area, low reactivity, limited active sites and easy aggregation, its application in water pollution treatment is limited, and effective means need to be explored to improve its performance in practical application. Studies have shown that carbon dots (CDs) are a new type of carbon-based nanomaterial with abundant functional groups, electronic and optical properties, which can effectively transfer electrons to achieve energy conversion or catalytic reactions; pyrite quantum dots (PQD) have become a nano-material with application potential due to their abundance, non-toxicity, stability and optical properties. CDs and PQD have excellent biocompatibility, making them very suitable for biomedical applications such as photocatalytic processes, biological imaging, cancer treatment, etc., but their application in the environmental field is not widespread.

[0004] CN116239215A discloses a wetland substrate and a wetland pollution control method based on offline. The wetland substrate comprises a first filler layer, a second filler layer and a third filler layer arranged from top to bottom. The filler of the first filler layer is a mixture of purple soil and river sand. The filler of the second filler layer is a mixture of purple soil, river sand and pyrite powder. The filler of the third filler layer is pyrite powder. By using common purple soil / river sand and iron ore filler for enhanced phosphorus removal, the technical problems of limited nitrogen and phosphorus removal effect and high preparation cost of the wetland substrate material in the prior art are solved. Although the patent uses river sand and pyrite powder as the artificial wetland substrate to solve the technical problems of limited nitrogen and phosphorus removal effect and high preparation cost of the wetland substrate material in the prior art, it still cannot achieve efficient nitrogen and phosphorus removal. SUMMARY

[0005] The purpose of the present application is to solve the problem of reducing pollutant removal rate caused by nano-plastic exposure in the current artificial wetland system, and to provide an artificial wetland filler and its application in artificial wetland under nano-plastic exposure. The present application uses PQD-CDs as artificial wetland substrate to further improve microbial electron transfer efficiency, providing a new possible way for efficient and low-cost wastewater treatment.

[0006] The artificial wetland filler of the present application is composed of pyrite quantum dots PQD and carbon dots CDs.

[0007] Further, the filler is composed of pyrite quantum dots PQD and carbon dots CDs in equal mass ratio.

[0008] Further, the preparation method of the pyrite quantum dots PQD is as follows:

[0009] Dissolve FeCl2 in degassed DMSO and stir with TGA, add Na2S2O3 solution drop by drop, and the solution color changes to wine color after precipitation crystals, then centrifuge the particles and wash with ethanol and acetone to obtain pyrite quantum dots PQD; wherein the molar ratio of FeCl2 to Na2S2O3 solution is 1:1-3.

[0010] The solution color changes from brick color to wine color.

[0011] Further, the molar volume ratio of FeCl2 to degassed DMSO is 1 mmol:40-50 mL.

[0012] Further, the preparation method of the carbon dots CDs is as follows:

[0013] The L-alanine solution is added to the citric acid, the mixture is stirred, and then ultrasonic treatment is performed, and then the mixture is sealed in a microwave oven for microwave treatment, and then the mixture is cooled to room temperature, dissolved in deionized water, stirred uniformly, filtered, and then the obtained filter cake is extracted with ethyl acetate to obtain CDs.

[0014] Further, the mass concentration of the L-alanine solution is 0.2-0.4 g / mL.

[0015] Further, the mass-volume ratio of L-alanine to citric acid is 1 g: 50-70 mL.

[0016] Further, the mass-volume ratio of the product after microwave treatment and cooling to deionized water is 5 g: 8-12 mL.

[0017] The method for preparing the artificial wetland filler of the application is as follows:

[0018] After the carbon dots CDs are made into powder, the powder is dissolved in distilled water, continuously magnetically stirred and boiled to 100 DEG C, and then pyrite quantum dots PQD of the same mass as the carbon dots CDs are immediately added, and stirring is performed in the dark, and then the mixture is centrifuged, washed with distilled water, and vacuum freeze-dried to obtain a PQD-CDs composite material, which is used as an artificial wetland filler.

[0019] The application of the artificial wetland filler of the application is applied to the repair of artificial wetlands under nano-plastic exposure.

[0020] The application of the application combines CDs and PQD to prepare a composite material PQD-CDs, which can improve the electron transfer efficiency of iron ions in PQD and further enhance the pollutant removal efficiency of artificial wetlands. Specifically, the PQD-CDs, as a new type of iron-containing carbon dots, can eliminate the active oxygen accumulated by plants under stress conditions, reduce the inhibition of active oxygen on plant photosynthesis and damage to other organelles to protect the photosynthetic system, and further improve the stress resistance of plants. In addition, the PQD-CDs can accelerate the oxidation of Fe(III), promote the transfer of generated electrons to microorganisms, and promote the synthesis of iron-based cofactors (such as Fe-S clusters and hemoglobin), enhance the synthesis and utilization of iron-containing enzymes (NAR and NIR), which is helpful for the carbon, nitrogen and sulfur element cycle of microorganisms. In summary, the use of the PQD-CDs composite material can reduce the negative effects of nano-plastics on plants and microorganisms in artificial wetlands, and help to maintain the health and balance of the artificial wetland ecosystem.

[0021] The present application is prepared by adopting pyrite quantum dots (PQD) and carbon dots (CDs) composite; the PQD is prepared by composite of FeCl2 and Na2S2O3 solution; the CDs is obtained by pyrolysis method. This green and simple preparation method makes the PQD-CDs composite material possible. The present application can significantly enhance the pollutant removal efficiency by wrapping the PQD-CDs in the polyurethane material and putting it into the constructed wetland, which has important significance for the treatment of farmland wastewater. This innovative method contributes to the efficiency and sustainable development of the water treatment field. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Figure is a horizontal subsurface flow constructed wetland system test device diagram

[0023] Figure 2 Figure is the rhizosphere microbial nitrogen metabolism enzyme activity graph of the PQ-CDs constructed wetland, the left graph is the microbial NAR activity graph, and the right graph is the microbial NIR activity graph;

[0024] Figure 3 Figure is the pollutant removal efficiency of the PQ-CDs constructed wetland;

[0025] Figure 4 Figure is the scanning electron microscope (SEM) graph of the PQD-CDs composite material;

[0026] Figure 5 Figure is the X-ray photoelectron spectroscopy (XPS) of the PQD-CDs composite material;

[0027] Figure 6 Figure is the FT-IR spectrum of the PQD-CDs composite material;

[0028] Figure 7 Figure is the ultraviolet spectrum (A) and infrared spectrum (B) of the PQD-CDs composite material. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear and apparent, the spirit of the present application will be described in detail below, and any person skilled in the art can make changes and modifications to the technology taught by the present application content after understanding the embodiments of the present application content, which does not deviate from the spirit and scope of the present application content.

[0030] The schematic embodiments of the present application and their descriptions are used to explain the present application, but not as a limitation on the present application.

[0031] Example 1: Preparation of PQD-CDs

[0032] Preparation of pyrite quantum dots, FeCl2(1.0 mmol) was dissolved in degassed DMSO (45 mL) and TGA was added with stirring for 30 min. Na2S2O3 solution was added dropwise, and the solution changed color after the crystals were precipitated, centrifuged to separate the particles, washed with ethanol and acetone to obtain PQD, and dried in a vacuum at 55°C for 7 hours.

[0033] During the experiment, 0.3 g of L-alanine was first dissolved in 10 mL of deionized water and 20 mL of citric acid was added, and stirred at 60°C for 40 minutes. Then, ultrasonic treatment was carried out for 30 minutes, and the mixture was sealed in a microwave oven for 15 minutes. After the product was cooled, it was dissolved in 10 mL of deionized water and stirred. Finally, impurities were removed by filtration, and CDs were extracted with ethyl acetate. The optimal storage condition is in a dark environment below 5°C.

[0034] 10 mg of CDs powder was dissolved in distilled water, continuously stirred with magnetic stirring and boiled to 100°C. Then, 10 mg of PQD was added to the CDs solution, and stirred in the dark for 60 minutes. Then the solution was centrifuged at 11000 rpm for 10 min, and the PQD-CDs composite was washed with distilled water for 3 times to remove excess PQD and CDs. Finally, the PQD-CDs composite was collected by freeze-drying under vacuum, and stored at 4°C for subsequent use.

[0035] The following cases are some specific implementation cases and application cases of the present application in actual application, but are not limited thereto.

[0036] Application Example: PQD-CDs as filler to treat artificial wetlands under nano-plastic exposure

[0037] This application example constructs three groups of horizontal subsurface flow artificial wetlands. Quartz sand and pyrite are used as the main substrate layer (uniformly mixed, volume ratio 1:1) in the artificial wetland system, and gravel is filled at the bottom. Acorus calamus L. is used as the test plant, with a planting density of 50 plants / m 2 , and a biomass of 1.0 kg fresh weight / m 2 . After the artificial wetland system is built, simulated farmland wastewater is introduced into the top of the artificial wetland through a peristaltic pump, and nano-plastic is added to two groups, with a hydraulic retention time of 5 days. In addition, PQD-CDs are wrapped in polyurethane material, which is then introduced into one group of artificial wetland systems with nano-plastic. Specifically, the artificial wetland system without adding nano-plastic and PQD-CDs is the CK group, the artificial wetland system with nano-plastic but without PQD-CDs is the NPs group, and the artificial wetland system with both nano-plastic and PQD-CDs is the PQD-CDs group.

[0038] As Figure 2As shown, the pollutant removal rates of the constructed wetland system decreased significantly after adding NPs, and adding PQD-CDs significantly improved the pollutant removal efficiency of the constructed wetland system compared with the NPs group. Specifically, the COD, TN, NH4 + -N and NH3 - removal rates of the PQD-CDs group were 37.91%, 49.35%, 70.74% and 54.05%, respectively, which were 1.38, 1.76, 1.21 and 1.28 times the pollutant removal rates of the group without adding PQD-CDs Figure 2 . In addition, adding NPs significantly reduced the activities of nitrogen metabolic enzymes, and the NAR and NIR activities of the PQD-CDs group were 1.73 and 1.72 times those of the NPs group, indicating that adding PQD-CDs in the constructed wetland system increased the activities of microbial nitrogen metabolic enzymes. As observed by SEM Figure 3 , the synthesized PQD-CDs nanocomposites had good uniformity, indicating that the PQD-CDs nanocomposites had good crystallinity and a relatively smooth surface with small pore structures. The chemical composition of the PQD-CDs nanocomposites was analyzed by X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopy Figure 4 and Figure 5 . In the FTIR analysis of the PQD-CDs nanocomposites, several characteristic peaks were identified, including 3415 cm -1 and 3175 cm -1 , corresponding to the stretching mode of N-H / O-H, indicating that the PQD-CDs nanocomposites had high hydrophilicity. 2380 cm -1 , 1670 cm -1 and 1410 cm -1 corresponded to S-H groups, COO- groups and C=S vibrations, respectively. XPS measurements were performed to determine the elemental composition of the PQD-CDs, and the results showed that the PQD-CDs nanocomposites were composed of S, C and Fe elements, and after modification, the percentages of S and Fe elements decreased by 10.55% and 6.03%, respectively, while the percentage of C element increased by 16.58%. The UV spectroscopy results showed that the adsorption peak centered at 390 nm belonged to the surface / molecular center, and the introduction of oxygen atoms from glucose may have expanded the conjugated system and changed the surface state of the carbon quantum dots, consistent with the UV-visible absorption characteristics of the PQD-CDs nanocomposites Figure 7 A). The infrared spectroscopy results showed that the reduction of intermolecular forces after pyrite modification simplified the characteristic frequencies of chemical bonds, resulting in a narrowing of the absorption peak, and the decrease in disulfide bonds led to hydrophobic interactions and ion exchange interactions Figure 7 B).

Claims

1. A method of preparing a constructed wetland fill material, characterised by: The artificial wetland filler is composed of pyrite quantum dots PQD and carbon dots CDs in equal mass ratio; the artificial wetland filler preparation method is as follows: After the carbon dots CDs are made into powder, they are dissolved in distilled water, continuously magnetically stirred and boiled to 100°C, and then the same mass of pyrite quantum dots PQD is immediately added, stirred in the dark, centrifuged, washed with distilled water, vacuum freeze-dried, and the PQD-CDs composite material is obtained as the artificial wetland filler; The pyrite quantum dots PQD preparation method is as follows: FeCl2 is dissolved in degassed DMSO and stirred with TGA, Na2S2O3 solution is added dropwise, the solution color changes to wine color, and then the precipitated crystals are obtained, centrifuged, and the particles are washed with ethanol and acetone to obtain the pyrite quantum dots PQD; wherein the molar ratio of FeCl2 to Na2S2O3 solution is 1:1~3; the molar volume ratio of FeCl2 to degassed DMSO is 1mmol:40~50mL; The carbon dots CDs preparation method is as follows: L-alanine solution is added to citric acid, stirred and mixed, then ultrasonically treated, and then sealed in a microwave oven for microwave treatment, cooled to room temperature after treatment, dissolved in deionized water and stirred uniformly, filtered, and the obtained filter cake is extracted with ethyl acetate to obtain CDs.

2. A method of preparing a constructed wetland media according to claim 1, characterised in that The mass concentration of the L-alanine solution is 0.2~0.4g / mL.

3. The method of claim 1, wherein The mass-volume ratio of L-alanine to citric acid is 1g:50~70mL.

4. The method of claim 1, wherein The mass-volume ratio of the product after microwave treatment and cooling to deionized water is 5g:8~12mL.

5. Use of a constructed wetland filler prepared according to claim 1, characterized in that The artificial wetland filler is applied to artificial wetland remediation under nano-plastic exposure.

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