Constructed wetland filler as well as preparation method and application thereof

Abstract

The invention discloses a constructed wetland filler and a preparation method and application thereof, and relates to the field of environmental treatment, and the filler is composed of pyrite quantum dots PQD and carbon dots CDs. The preparation method comprises the following steps: preparing carbon dots CDs into powder, dissolving the powder in distilled water, continuously magnetically stirring and boiling to 100 DEG C, immediately adding pyrite quantum dots PQD of which the mass is equal to that of the carbon dots CDs, stirring and centrifuging under a dark condition, washing with distilled water, and performing vacuum freeze-drying to obtain the PQD-CDs composite material. The filler disclosed by the invention can obviously enhance the pollutant removal efficiency, and has important significance on the treatment of farmland wastewater. The innovative method makes contribution to improvement of efficiency and sustainable development in the field of water treatment.

Description

Technical Field

[0001] The invention belongs to the field of environmental treatment, and in particular relates to an artificial wetland filler and a preparation method and application thereof. Background Art

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

[0003] Pyrite (FeS 2 ) can secrete Fe(II) and act as an electron donor to convert NH 4 + Restore to NO 3 - 、NO 2 - and N 2 It can promote the autotrophic denitrification process and provide iron ions for microorganisms to promote their growth and metabolism. Therefore, it can be used as an artificial wetland matrix in sewage treatment. However, its application in water pollution treatment is limited by some inherent defects, such as small specific surface area, low reaction activity, limited active sites and easy agglomeration. It is necessary to explore effective means to improve its performance in practical applications. Studies have shown that carbon dots (CDs) are a new type of carbon-based nanomaterial with rich functional groups, electronic and optical properties, which can effectively transfer electrons to achieve energy conversion or catalytic reactions; pyrite quantum dots (PQD) have become nanomaterials with application potential due to their richness, non-toxicity, stability and optical properties. CDs and PQD have excellent biocompatibility, making them very suitable for biomedical applications such as photocatalytic processes, bioimaging, cancer treatment, etc. However, their application in the environmental field is not yet widespread.

[0004] Publication number CN116239215A, invention name "A wetland matrix and an offline wetland pollution control method" discloses a wetland matrix, including a first filler layer, a second filler layer and a third filler layer arranged in sequence 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 fillers for enhanced phosphorus removal, the technical problems of limited nitrogen and phosphorus removal effect and high preparation cost of wetland matrix materials in the prior art are solved. Although the patent uses river sand and pyrite powder as artificial wetland matrices to solve the technical problems of limited nitrogen and phosphorus removal effect and high preparation cost of wetland matrix materials in the prior art, it still cannot achieve efficient nitrogen and phosphorus removal. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that nanoplastic exposure in the current artificial wetland system reduces the pollutant removal rate, and to provide an artificial wetland filler and its application in an artificial wetland exposed to nanoplastics. The present invention uses PQD-CDs as an artificial wetland matrix to further improve the efficiency of microbial electron transfer, providing a new possible way to achieve efficient and low-cost sewage treatment.

[0006] The invention discloses an artificial wetland filler, which is composed of pyrite quantum dots PQD and carbon dots CDs.

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

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

[0009] FeCl 2 Dissolve in degassed DMSO and add TGA with stirring, then add Na 2 S 2 O 3 The solution changes to a wine color and then crystals are precipitated. The crystals are centrifuged to separate the particles and washed with ethanol and acetone to obtain pyrite quantum dots PQD. Among them, FeCl 2 with Na 2 S 2 O 3 The molar ratio of the solution is 1:1~3.

[0010] The solution color changes to wine color from brick color to burnt copper color and then to wine color.

[0011] Furthermore, the FeCl 2 The molar volume ratio with degassed DMSO is 1mmol:40~50mL.

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

[0013] The L-alanine solution was added to the citric acid, stirred and mixed, and then ultrasonically treated. The mixture was then sealed in a microwave oven and microwaved. After the treatment, the mixture was cooled to room temperature, dissolved in deionized water and stirred evenly. After filtering, the filter cake was extracted with ethyl acetate to obtain CDs.

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

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

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

[0017] A method for preparing an artificial wetland filler of the present invention is as follows:

[0018] After the carbon dots CDs are made into powder, they are dissolved in distilled water, continuously magnetically stirred and boiled to 100°C, and pyrite quantum dots PQD with the same mass as the carbon dots CDs are immediately added. The mixture is stirred in the dark, centrifuged, washed with distilled water, and vacuum-frozen to obtain a PQD-CDs composite material as a filler for artificial wetlands.

[0019] The invention discloses an application of an artificial wetland filler, wherein the artificial wetland filler is applied to the restoration of artificial wetlands exposed to nano plastics.

[0020] The present invention combines CDs and PQD to form a composite material PQD-CDs, which can enhance the removal efficiency of pollutants in artificial wetlands by improving the electron transfer efficiency of iron ions in PQD. Specifically, PQD-CDs, as a new type of iron-containing carbon dots, can act as electron transfer bodies to eliminate reactive oxygen species accumulated in plants under stress, reduce the inhibition of photosynthesis by reactive oxygen species and damage to other organelles to protect the photosynthetic system, and thus improve the stress resistance of plants. In addition, PQD-CDs can accelerate the oxidation of Fe(III), promote the transfer of generated electrons to microorganisms, promote the synthesis of iron-based cofactors (such as Fe-S clusters and heme), and enhance the synthesis and utilization of iron-containing enzymes (NAR and NIR), which contributes to the carbon, nitrogen, and sulfur element cycles of microorganisms. In summary, the use of PQD-CDs composite materials can reduce the negative impact of nanoplastics on artificial wetland plants and microorganisms, and help maintain the health and balance of artificial wetland ecosystems.

[0021] The present invention adopts pyrite quantum dots (PQD) and carbon dots (CDs) to prepare the composite; the PQD is composed of FeCl 2 and Na 2 S 2 O 3 The solution composite is prepared; the CDs are obtained by a pyrolysis method. This green and simple preparation method makes PQD-CDs composite materials possible. The present invention can significantly enhance the pollutant removal efficiency by wrapping PQD-CDs in polyurethane materials and placing them in artificial wetlands, which is of great significance for the treatment of agricultural wastewater. This innovative method contributes to improving the efficiency and sustainable development in the field of water treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Figure 1. Horizontal subsurface flow artificial wetland system test device

[0023] Figure 2 The left picture shows the activity of nitrogen metabolism enzymes in rhizosphere microorganisms in artificial wetlands with PQ-CDs added. The right picture shows the activity of microorganisms NIR.

[0024] Figure 3 The pollutant removal efficiency of artificial wetlands with PQ-CDs added;

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

[0026] Figure 5 X-ray photoelectron spectroscopy (XPS) of PQD-CDs composites;

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

[0028] Figure 7 Ultraviolet spectrum (A) and infrared spectrum (B) of PQD-CDs composite materials. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention more clearly understood, the spirit of the contents disclosed by the present invention will be described in detail below. After understanding the embodiments of the contents of the present invention, any technician in the relevant technical field can change and modify them according to the techniques taught by the contents of the present invention without departing from the spirit and scope of the contents of the present invention.

[0030] The exemplary embodiments of the present invention and the description thereof are used to explain the present invention but are not intended to limit the present invention.

[0031] Example 1: Preparation of PQD-CDs

[0032] Preparation of pyrite quantum dots, FeCl 2 (1.0 mmol) was dissolved in degassed DMSO (45 mL) and TGA was added and stirred for 30 min. Na 2 S 2 O 3 The solution was dissolved in water, and crystals were precipitated after the solution changed color. The particles were separated by centrifugation, washed with ethanol and acetone to obtain PQDs, and dried under vacuum at 55 °C for 7 h.

[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 performed 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 best storage condition is in a dark environment below 5 ° C.

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

[0035] The following cases are some specific implementation cases and application cases of the present invention in practical applications, but are not limited to them.

[0036] Application example: Treating artificial wetlands exposed to nanoplastics using PQD-CDs as fillers

[0037] This application example constructs three groups of horizontal subsurface flow artificial wetlands. The artificial wetland systems all use quartz sand and pyrite as the main matrix layer (evenly mixed, volume ratio of 1:1), and the bottom layer is filled with gravel. Acorus calamus L. is used as the test plant, with a planting density of 50 plants / m 2 , biomass is 1.0kg fresh weight / m 2. After the artificial wetland system was built, simulated farmland wastewater was introduced from the top of the artificial wetland through a peristaltic pump, and nanoplastics were added to two of the groups with a hydraulic retention time of 5 days. In addition, PQD-CDs were wrapped in polyurethane material and then placed in a group of artificial wetland systems with nanoplastics added. Specifically, the artificial wetland system without nanoplastics and PQD-CDs was the CK group, the artificial wetland system with nanoplastics but no PQD-CDs was the NPs group, and the artificial wetland system with both nanoplastics and PQD-CDs added was the PQD-CDs group.

[0038] like Figure 2 As shown in the figure, after adding nanoplastics, the pollutant removal rate of the constructed wetland decreased significantly, and compared with the NPs group, the addition of PQD-CDs significantly improved the pollutant removal efficiency of the constructed wetland system. 4 + -N and NH 3 - The removal rates of -N were 37.91%, 49.35%, 70.74% and 54.05%, respectively, which were 1.38, 1.76, 1.21 and 1.28 times of those without PQD-CDs. Figure 2 ). In addition, the addition of nanoplastics significantly reduced the activity of nitrogen metabolism enzymes, and the NAR and NIR activities of the PQD-CDs group were 1.73 and 1.72 times that of the NPs group, indicating that the addition of PQD-CDs to the artificial wetland system would increase the activity of microbial nitrogen metabolism enzymes. SEM observation showed that ( Figure 3 ), the synthesized PQD-CDs nanocomposite has good uniformity, which indicates that the PQD-CDs nanocomposite has good crystallinity, a relatively smooth surface and a small pore structure. The chemical composition of the PQD-CDs nanocomposite was analyzed by X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopy ( Figure 4 and Figure 5 In the FTIR analysis of PQD-CDs nanocomposites, several characteristic peaks were identified, among which 3415 cm -1 and 3175cm -1 2380cm, corresponding to the stretching mode of NH / OH, indicating that the PQD-CDs nanocomposite has high hydrophilicity. -1 、1670cm -1 and 1410cm -1The corresponding positions are SH group, COO- group and C=S vibration respectively. XPS measurement was performed to determine the elemental composition of PQD-CDs. The results showed that PQD-CDs nanocomposites consisted of S, C and Fe elements, and the percentages of S and Fe elements decreased by 10.55% and 6.03% respectively after modification, while the percentage of C element increased by 16.58%. The UV spectrum results showed that the adsorption peak centered at 390nm belonged to the surface / molecular center. The introduction of oxygen atoms from glucose may expand the conjugated system and change the surface state of carbon quantum dots, which is consistent with the UV-visible absorption characteristics of PQD-CDs nanocomposites ( Figure 7 A). The infrared spectrum results show that the reduction of intermolecular forces after pyrite modification simplifies the characteristic frequency of chemical bonds, resulting in a narrowing of the absorption peak, a decrease in disulfide bonds, and the presence of hydrophobic interactions and ion exchange interactions ( Figure 7 B).

Claims

1. An artificial wetland filler, characterized in that: The filler is composed of pyrite quantum dots PQD and carbon dots CDs.

2. The artificial wetland filler according to claim 1, characterized in that The filler is composed of pyrite quantum dots PQD and carbon dots CDs in equal weight ratio.

3. An artificial wetland filler according to claim 1 or 2, characterized in that The preparation method of pyrite quantum dots PQD is as follows: Dissolve FeCl2 in degassed DMSO and add TGA for stirring, add Na2S2O3 solution dropwise, and crystals are precipitated after the solution changes color to wine color. After the precipitated crystals, the particles are separated by centrifugation and washed with ethanol and acetone to obtain pyrite quantum dots PQD; wherein the molar ratio of FeCl2 to Na2S2O3 solution is 1:1-3.

4. The artificial wetland filler according to claim 3, characterized in that The molar volume ratio of the FeCl2 to the degassed DMSO is 1 mmol:40-50 mL.

5. An artificial wetland filler according to claim 1 or 2, characterized in that The method for preparing the carbon dots CDs is as follows: The L-alanine solution was added to the citric acid, stirred and mixed, and then ultrasonically treated. The mixture was then sealed in a microwave oven and microwaved. After the treatment, the mixture was cooled to room temperature, dissolved in deionized water and stirred evenly. After filtering, the filter cake was extracted with ethyl acetate to obtain CDs.

6. The artificial wetland filler according to claim 5, characterized in that The mass concentration of the L-alanine solution is 0.2-0.4 g / mL.

7. The artificial wetland filler according to claim 5, characterized in that The mass volume ratio of L-alanine to citric acid is 1g:50-70mL.

8. The artificial wetland filler according to claim 5, characterized in that The mass volume ratio of the product after microwave treatment and cooling to deionized water is 5g:8-12mL.

9. A method for preparing a constructed wetland filler according to claim 1, characterized in that The 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 pyrite quantum dots PQD with the same mass as the carbon dots CDs are immediately added. The mixture is stirred in the dark, centrifuged, washed with distilled water, and vacuum-frozen to obtain a PQD-CDs composite material as a filler for artificial wetlands.

10. The use of an artificial wetland filler as claimed in claim 1 or 2, characterized in that The artificial wetland filler is used for repairing artificial wetlands exposed to nanoplastics.

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