Nanometer plastic enrichment method based on inorganic flocculation and quantitative detection method thereof

Abstract

The invention relates to the technical field of nano-plastic detection methods, and discloses a nano-plastic enrichment method based on inorganic flocculation and a quantitative detection method thereof, and the method comprises the following steps: S1, adding an alkaline solution and a polyferric sulfate solution into a water sample to be detected to form ferric hydroxide floc; s2, after centrifugal treatment, collecting a compound formed by the ferric hydroxide floc and the nano plastic; and S3, carrying out ethanol resuspension and drying treatment on the compound. The nano-plastic enrichment method based on inorganic flocculation is simple and convenient to operate, low in cost and high in efficiency, introduction of organic interferents is avoided, the sensitivity and accuracy of Py-GC / MS detection are remarkably improved, and the nano-plastic enrichment method is suitable for environmental monitoring, drinking water safety evaluation and nano-plastic pollution risk research.

Description

Technical Field

[0001] This invention relates to the field of nanoplastic detection methods, specifically to a method for enriching nanoplastics based on inorganic flocculation and a method for quantitative detection thereof. Background Technology

[0002] Nanoplastics, as an emerging environmental pollutant, pose a potential threat to ecosystems and human health due to their small particle size, large surface area, and high mobility. Current methods for detecting nanoplastics mainly rely on microscopy, spectroscopy, and mass spectrometry, but all have certain limitations. For example: 1. Although optical microscopes and electron microscopes can provide morphological information, they lack the ability to quantify components, making it difficult to achieve quantitative analysis of polymer types and contents; 2. Although Raman and infrared spectroscopy can characterize chemical structures, they suffer from problems such as low spatial resolution, weak signal intensity, and fluorescence interference. 3. The pyrolysis gas chromatography-mass spectrometry (Py-GC / MS) method has high specificity and sensitivity, and can effectively identify polymer types. However, its practical application is often limited by the low concentration of nanoplastics in environmental water and the complexity of the matrix.

[0003] To overcome the above shortcomings, researchers have developed a variety of pre-concentration technologies (such as ultrafiltration, cloud spot extraction, protein crown extraction, and magnetic solid phase extraction), but these technologies all have drawbacks such as long processing time, high cost, and easy introduction of organic interferences.

[0004] Therefore, there is an urgent need for a rapid, efficient, and organic-interference-free method for pre-concentrating nanoplastics to improve the accuracy and reliability of Py-GC / MS detection. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for enriching nanoplastics based on inorganic flocculation and a quantitative detection method thereof, which has the advantages of being able to enrich nanoplastics quickly, efficiently, and without organic interference.

[0006] (II) Technical Solution To achieve the aforementioned goal of rapidly, efficiently, and without organic interference enriching nanoplastics, this invention provides the following technical solution: a nanoplastic enrichment method based on inorganic flocculation, comprising the following steps: S1. Add alkaline solution and polyferric sulfate solution to the water sample to be tested to form ferric hydroxide flocs; S2. After centrifugation, collect the complex formed by the ferric hydroxide flocs and nanoplastics. S3. The complex is subjected to ethanol resuspension and drying.

[0007] In a preferred embodiment of the present invention, the alkaline solution in step S1 is a sodium hydroxide solution.

[0008] As a preferred embodiment of the present invention, the concentration of the sodium hydroxide solution is 1 mol / L; the concentration of the polyferric sulfate solution is 2 g / L.

[0009] As a preferred embodiment of the present invention, in step S2, the centrifugation conditions are 10,000 rpm and the time is 5 min.

[0010] In a preferred embodiment of the present invention, in step S3, the complex is resuspended in ethanol and then transferred to a carrier and dried at 80°C.

[0011] As a preferred embodiment of the present invention, the addition ratio of sodium hydroxide solution to polyferric sulfate solution is 0.01-0.03:3.

[0012] As a preferred embodiment of the present invention, the method is applicable to the detection of nanoplastics including polystyrene, polymethyl methacrylate, polypropylene, polyethylene terephthalate, and polyvinyl chloride.

[0013] (III) Beneficial Effects Compared with existing technologies, this invention provides a method for enriching nanoplastics based on inorganic flocculation and a method for quantitative detection thereof, which has the following beneficial effects: 1. This method for enriching nanoplastics based on inorganic flocculation uses inorganic flocculant polyferric sulfate to form ferric hydroxide flocs under alkaline conditions, which can complete the enrichment treatment of nanoplastics within 15 minutes, significantly shortening the pretreatment time.

[0014] 2. This inorganic flocculation-based method for enriching nanoplastics is simple to operate, low in cost, and highly efficient. It avoids the introduction of organic interferences and significantly improves the sensitivity and accuracy of Py-GC / MS detection. It is suitable for environmental monitoring, drinking water safety assessment, and nanoplastic pollution risk research.

[0015] 3. This inorganic flocculation-based method for enriching nanoplastics shows excellent applicability to various types of nanoplastics (such as PS, PMMA, PP, PET, and PVC), with recovery rates generally greater than 92% and detection limits reaching 0.01-0.02 μg / L.

[0016] 4. This inorganic flocculation-based nanoplastic enrichment method can maintain a high recovery rate even under complex aquatic matrix conditions. It can stably achieve enrichment and detection in natural water bodies such as rivers and lakes, as well as in environments with dissolved organic matter concentrations of 0-30 mg / L. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow for the nanoplastic enrichment method of the present invention; Figure 2 The images show scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDX) analysis diagrams of different types of nanoplastics after flocculation. Figure 3 The results of recovery optimization and Py-GC / MS detection are shown below. Figure 4 The results show the applicability evaluation of the method of the present invention under different conditions. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: Please see Figures 1-4 This invention discloses a method for enriching nanoplastics based on inorganic flocculation, specifically including the following steps: S1. Add an alkaline solution and a polyferric sulfate solution to the water sample to be tested, shake for 10 minutes to form ferric hydroxide flocs; sodium hydroxide solution is preferred as the alkaline solution; the concentration of sodium hydroxide solution is 1 mol / L; the concentration of polyferric sulfate solution is 2 g / L. Using 100 nm polystyrene (PS) nanoparticles as a model, the dosage of polystyrene flocculant (PFS) was optimized. The results showed that when the PFS concentration was 150 mg / L, the PS recovery rate reached 99.5%, which was the optimal dosage (see reference...). Figure 3 ; Figure 3 middle, Figure 3 A represents the recovery curves of PS nanoparticles at different PFS concentrations; Figure 3 B shows the Py-GC / MS total ion chromatogram (TIC) and characteristic ion chromatogram (SIC) obtained after treatment with 150 mg / LPFS. Figure 3 C is the mass spectrum of styrene monomer; Figure 3 D is the mass spectrum of styrene trimer); This step can be completed in just over ten minutes, significantly shortening the pretreatment time before nanoplastic detection and making it far more efficient than methods such as ultrafiltration and protein crown extraction.

[0020] S2. Centrifuge the reaction solution at 10,000 rpm for 5 min, and then collect the complex formed by the ferric hydroxide flocs and nanoplastics. The precipitate obtained after separation is dense and stable, which can effectively prevent the loss of nanoparticles during the operation, thus providing a reliable guarantee for subsequent detection.

[0021] S3. The complex is resuspended in ethanol and dried. Specifically, after being resuspended in ethanol, the complex is transferred to a pyrolysis sample cup and dried at 80°C.

[0022] Preferably, the ratio of sodium hydroxide solution to polyferric sulfate solution is 0.01-0.03:3. Specifically, in this embodiment, 20 μL of NaOH solution and 3 mL of PFS solution are added (the water sample to be tested is 37 mL, placed in a 50 mL centrifuge tube). In this invention, ethanol is used as a resuspension solvent to avoid the introduction of organic substances such as surfactants and proteins, and will not interfere with Py-GC / MS, thereby ensuring the accuracy of the signal and the detection sensitivity. In this invention, by using inorganic flocculant polyferric sulfate to form ferric hydroxide flocs under alkaline conditions, the enrichment treatment of nanoplastics can be completed within 15 minutes, significantly shortening the pretreatment time. This method is applicable to the detection of nanoplastics including polystyrene, polymethyl methacrylate, polypropylene, polyethylene terephthalate, and polyvinyl chloride, with recoveries generally greater than 92.8% and detection limits reaching 0.01-0.02 μg / L, demonstrating its good universality and high sensitivity to different polymers.

[0023] In this embodiment, surface water samples were collected from the Pearl River, Baiyun Lake, and West Lake, respectively. The PS nanoplastics were detected using the method of this invention, and the concentration was 0.11-0.36 ug / L, which is consistent with the internationally reported level, thus indicating that the method is applicable to water bodies in complex environments. Please see Figure 4 , Figure 4 middle, Figure 4 A shows the recycling rates of five types of nanoplastics (PS, PMMA, PP, PET, PVC); Figure 4 B shows the recovery rate of PS nanoplastics under different surface charges and particle sizes; Figure 4 C shows the recovery rate of 100 nm PS nanoparticles under different humic acid concentrations (0–30 mg / L DOC), indicating that the method has good tolerance to disturbances from natural water matrix.

[0024] In addition, please see Figure 2 , Figure 2 A shows the FeOOH-PS (polystyrene) composite; Figure 2 B shows the FeOOH-PP (polypropylene) composite; Figure 2 C shows a FeOOH-PVC (polyvinyl chloride) composite; Figure 2 D-2H is the elemental distribution map of the FeOOH–PVC complex, corresponding to Fe, O, C, Cl and the overall signal, respectively; SEM and EDX results further verified the binding effect of flocculant and nanoplastic, proving that the method achieves efficient capture at the microscopic level.

[0025] Example 2: Please see Figure 1 Based on Example 1, this example proposes a method for quantitative detection of nanoplastics, which specifically includes the following steps: A1. The complex was obtained using the enrichment method of Example 1; A2. The complex is placed in a pyrolysis gas chromatography-mass spectrometry system for qualitative and quantitative analysis to determine the polymer type and content. Preferably, the pyrolysis gas chromatography-mass spectrometry analysis adopts a multi-stage heating program with a heating range of 200℃ to 800℃.

[0026] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for enriching nanoplastics based on inorganic flocculation, characterized in that, Includes the following steps: S1. Add alkaline solution and polyferric sulfate solution to the water sample to be tested to form ferric hydroxide flocs; S2. After centrifugation, collect the complex formed by the ferric hydroxide flocs and nanoplastics. S3. The complex is subjected to ethanol resuspension and drying.

2. The method for enriching nanoplastics based on inorganic flocculation according to claim 1, characterized in that: In step S1, the alkaline solution is a sodium hydroxide solution.

3. The method for enriching nanoplastics based on inorganic flocculation according to claim 2, characterized in that: The concentration of the sodium hydroxide solution is 1 mol / L; the concentration of the polyferric sulfate solution is 2 g / L.

4. The method for enriching nanoplastics based on inorganic flocculation according to claim 1, characterized in that: In step S2, the centrifugation conditions are 10,000 rpm and the time is 5 min.

5. The method for enriching nanoplastics based on inorganic flocculation according to claim 1, characterized in that: In step S3, the complex is resuspended in ethanol and transferred to a carrier, and then dried at 80°C.

6. The method for enriching nanoplastics based on inorganic flocculation according to claim 2 or 3, characterized in that: The addition ratio of sodium hydroxide solution to polyferric sulfate solution is 0.01-0.03:

3.

7. The method for enriching nanoplastics based on inorganic flocculation according to any one of claims 1-6, characterized in that: The method is applicable to the detection of nanoplastics including polystyrene, polymethyl methacrylate, polypropylene, polyethylene terephthalate, and polyvinyl chloride.

8. A method for quantitative detection of nanoplastics, characterized in that, Includes the following steps: A1. The complex is obtained by the enrichment method according to any one of claims 1-7; A2. The complex was subjected to qualitative and quantitative analysis using a pyrolysis gas chromatography-mass spectrometry system to determine the polymer type and content.

9. The method for quantitative detection of nanoplastics according to claim 8, characterized in that: The pyrolysis gas chromatography-mass spectrometry analysis employs a multi-stage heating program with a heating range of 200℃ to 800℃.

Images