Application of Photoacoustic Spectroscopy in Characterization of Nano-Zerovalent Iron in Soil

Abstract

The present invention discloses a photoacoustic spectroscopy characterization technology for nano-zero-valent iron in soil, that is, the application of photoacoustic spectroscopy to the characterization of nano-zero-valent iron in soil. This characterization technology can eliminate the influence of soil on light absorption and scattering. Another object of the present invention is to obtain the amount of nano-zero-valent iron in soil by using the integral intensity of the photoacoustic signal, so as to quickly estimate the content in the soil. The present invention explores the characteristic photoacoustic spectroscopy signal of nano-zero-valent iron in soil, and provides an important idea for the characterization technology of nano-zero-valent iron in soil. The present invention verifies the correlation between the amount of nano-zero-valent iron in soil and the intensity of the photoacoustic spectroscopy signal, and provides a technical reference and a valuable starting point for the determination and characterization of nano-zero-valent iron in soil.

Description

Technical Field

[0001] The present invention relates to an application of a photoacoustic spectroscopy characterization technology for nano-zero-valent iron in soil, belonging to the field of analysis and detection technology, and particularly relates to an application of a photoacoustic spectroscopy characterization technology for nano-zero-valent iron in specific soil. Background Art

[0002] Nanoscale zero-valent iron (nZVI), due to its strong reducing properties, small particle size, and large specific surface area, primarily undergoes adsorption, ion exchange, redox, coprecipitation, and complexation reactions. It is used for the removal of heavy metals and halogenated organic matter, showing promising application prospects in environmental remediation. Nanoscale zero-valent iron (nZVI) is also playing an increasingly important role in soil pollution control.

[0003] Nano-zero-valent iron is widely used in various environments such as soil and groundwater to remove a variety of pollutants (Wang, CB; Zhang, WX Environmental Science & Technology, 1997, 31, 2154. Lei, C.; Sun, Y.; Khan, E.; Chen, SS; Tsang, DCW; Graham, NJD; Ok, YS; Yang, X.; Lin, DH; Feng, Y.; Li, XDC Chemosphere 2018, 196, 9. Liu, YZ; Wu, T.; White, JC; Lin, DH Nature Nanotechnology 2020, 16, 197. Ryu, A.; Jeong, SW; Jang, A.; Choi, H. Applied Catalysis B 2011, 105, 128.Cao, Z.; Li, H.; Lowry, GV; Shi, XY; Pan, XC; Xu, XH; Henkelman, G.; Xu, J.Environmental Science & Technology 2021, 55, 2628.). However, the study of the changes and fate of nanomaterials in soil has always been a difficult problem, especially the morphological characterization technology of nanomaterials in soil faces bottlenecks such as difficult separation, large interference, weak selectivity, and low sensitivity (Liu, X.; Cao, Z.; Yuan, ZL; Zhang, J.; Guo, XP; Yang, Y.; He, F.; Zhao, YP; Xu, J.Chemical Engineering Journal 2018, 334, 508.Xu, J.; Avellan, A.; Li, H.; Liu, XT; V.; Lou, ZM; Wang, Y.; Kaegi, R.; Henkelman, G.; Lowry, GVAdvanced Materials 2020, 32, No.e1906910. Li, L.; Wang, Q.; Yang, Y.; Luo, L.; Ding, R.; Yang, ZG; Li, HP Analytical Chemistry 2019,91,9442. Zhou, XX; Jiang, LW; Wang, DJ; He, S.; Li, CJ; Yan, B. Analytical Chemistry2020,92,4765). Photoacoustic signals based on photoacoustic spectroscopy have several obvious characteristics and advantages. They are not affected by the transmittance of the substance to be measured, nor by light scattering, and have obvious advantages in the analysis and characterization of solid materials such as soil (Petr K. Krivoshein, Dmitry S. Volkova, Olga B. Rogov, Mikhail A. Proskurnin, Photoacoustics, 2020, 18, 100162. Du Changwen, Raphael Linker, Avi Shaviv, Applied Spectroscopy, 2007, 61, 1063. Jing Huang, Nadia Jin M. Triolo, Georgios Bekiaris, Sander Bruun, and Fei Liu (Science of the Total Environment, 2022, 832, 155040). Using typical nanomaterials such as nano-zero-valent iron as their primary research targets, they established a photoacoustic spectroscopy-based technique for characterizing and detecting nano-zero-valent iron particles in soil. This technique provides an experimental basis and analytical foundation for characterizing the morphology and transformation of nanomaterials in soil. However, in situ analytical methods and techniques are currently lacking for characterizing and analyzing nano-zero-valent iron in soil.

[0004] Therefore, developing a method and technology to characterize nanomaterials in soil is of great significance for studying the mechanism and fate of nanomaterials in soil (Shi, ZQ; Fan, D.; Johnson, RL; Tratnyek, PG; Nurmi, JT; Wu, YX; Williams, KHJ Contamination Hydrology 2015, 181, 17. Liu, X.; Cao, Z.; Yuan, ZL; Zhang, J.; Guo, XP; Yang, Y.; He, F.; Zhao, YP; Xu, J. Chemical Engineering Journal 2018, 334, 508). Currently, ICP-based methods based on sample collection and processing have been developed. However, these methods involve the use of large instruments, are inconvenient to carry, have complex sample pretreatment processes, and are expensive to detect. Therefore, developing and establishing rapid characterization methods in soil is very important. Summary of the Invention

[0005] The present invention aims to provide a photoacoustic spectroscopy technique for characterizing nano-zero-valent iron in soil. Specifically, this technique can eliminate the effects of soil on light absorption and scattering. Another objective of the present invention is to use the integrated intensity of the photoacoustic signal to determine the amount of nano-zero-valent iron in soil, enabling rapid estimation of soil content.

[0006] Because nano-zero-valent iron strongly absorbs light in the visible range, it is highly effective for photoacoustic spectroscopy, requiring less sample transparency and exhibiting superior specificity compared to scattering spectroscopy. The present invention provides a strategy for characterizing nano-zero-valent iron using photoacoustic spectroscopy signals. The present invention provides a photoacoustic spectroscopy technique for characterizing nano-zero-valent iron in soil, where photoacoustic spectroscopy signals offer significant advantages for characterizing soil components.

[0007] The present invention uses photoacoustic spectroscopy to characterize nano-zero-valent iron in soil, which is to modify nano-zero-valent iron with organic molecules to obtain functionalized nano-zero-valent iron. The organic molecule is any one of the following structures:

[0008]

[0009] The organic molecules can be prepared by referring to the literature New repertoire of'donor-two-acceptor'NIRfluorogenic dyes, Einat Kisin-Finfer, Bioorganic & Medicinal Chemistry 21 (2013); the nano zero-valent iron particle size is 50-500nm, which can be purchased from professional manufacturers or obtained by some common preparation methods; the functionalized nano zero-valent iron can be obtained by stirring the organic molecules and nano zero-valent iron in anhydrous ethanol at room temperature under vacuum conditions for 10-15 hours. The functionalized nano zero-valent iron structure can be as shown in the attached Figure 5 As shown, this type of structure can make the photoacoustic spectroscopy signal obvious and stable during subsequent detection, which is beneficial to the characterization of nano-zero-valent iron.

[0010] The soil is obtained by collecting common dryland farmland soil with a pH of 5-9, treating it with a phosphate buffer solution with a pH of 6-8, and then air-drying it; the photoacoustic spectroscopy is excited by a xenon lamp with a wavelength of 400-1100nm and frequency modulated at 20-30Hz.

[0011] The present invention prepares three nano-zero-valent iron-spiked soil samples, which are treated with buffer solutions of pH = 6.0, 7.0, and 7.8, respectively, and then air-dried. The nano-zero-valent iron intrinsic photoacoustic signal modulated at 20-30 Hz is obtained. The integrated intensity of the signal has a significant linear correlation with the spiked content, with a correlation coefficient of 0.995, indicating that this method provides a valuable starting point for the in situ characterization of nano-zero-valent iron in soil.

[0012] The sample soil of the present invention is prepared as follows: the same batch of farmland soil is treated with a 1.0 mM sodium phosphate buffer solution with a pH of 6.0-8.0, and then naturally air-dried for use.

[0013] The present invention uses carbon black powder for calibration, an excitation light scanning wavelength of 400-1100 nm (corresponding to an energy range of 3.10 eV to 1.13 eV), and an excitation light tuning of 20-30 Hz to obtain a background photoacoustic signal. Functionalized nano-zero-valent iron (NPZI) was spiked into soil at a concentration of 50 mg / 50 g to obtain soil containing NPZI. The photoacoustic spectrum was measured under the same parameters, revealing a significant photoacoustic signal at 410-420 nm—specifically, at approximately 417 nm—attributed to the intrinsic NPZI surface plasmon signal.

[0014] The photoacoustic spectroscopy characterization principle of the present invention is as follows: the functionalized nano zero-valent iron of the present invention absorbs light energy from the visible light to the near-infrared light band and converts it into a photoacoustic signal. The integral intensity of the photoacoustic signal changes with the iron content of the nanoparts and the environment.

[0015] The weak acidity and alkalinity of the treated soil had little effect on the photoacoustic signal characteristics of nano-zero-valent iron, with no significant difference. The intensity of the photoacoustic characteristic signal showed a clear linear correlation with the content of spiked nano-zero-valent iron, and can be used to characterize the occurrence of nano-zero-valent iron in soil.

[0016] This study explores the characteristic photoacoustic spectroscopy signals of nano-zero-valent iron in soil, providing important insights into soil characterization techniques. The study also validates the correlation between the amount of nano-zero-valent iron in soil and the intensity of the photoacoustic spectroscopy signal, providing a technical reference and a valuable starting point for the determination and characterization of nano-zero-valent iron in soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the background photoacoustic spectroscopy signal of the soil treated with buffer solution.

[0018] Figure 2 It is the photoacoustic spectrum signal of the nano-valent iron spiked into the above soil (content of 50mg / 50g).

[0019] Figure 3 It is the change of photoacoustic spectrum of different nano-zero-valent iron spiked contents in soil (pH=7.0).

[0020] Figure 4 It is the linear relationship between different nano-zero-valent iron spike contents in soil (pH=7.0) and the photoacoustic spectroscopy signal intensity.

[0021] Figure 5 This is a schematic structural diagram of a functionalized nanometer zero-valent iron according to the present invention. DETAILED DESCRIPTION

[0022] The following embodiments are further descriptions of the present invention to illustrate the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0023] Example 1

[0024] 200 mg of 200-mesh carbon black was evenly spread in the photoacoustic cell as a reference material. A xenon lamp was used as the excitation light source, the scanning wavelength was 400-1100 nm (corresponding to the energy range of 3.10 eV to 1.13 eV), and the instrument background reference photoacoustic signal was obtained by tuning the excitation light at 25 Hz.

[0025] Three portions (500 g) of ground and sieved farmland soil were taken and placed in three 1000 mL beakers respectively. 100 mL of 1 mM phosphate buffer solution (a mixed solution of sodium dihydrogen phosphate and disodium hydrogen phosphate) with pH = 6.0, 7.0, and 7.8 were poured into each beaker respectively. The soil was allowed to stand for 10 minutes, filtered, and the soil was allowed to air dry naturally.

[0026] 10g of the above soil samples were taken respectively, and the photoacoustic signals of the three soils were obtained by using a xenon lamp as the excitation light source, scanning wavelength 400-1100nm, and tuning the excitation light at 25Hz. The experiment found no significant difference. Figure 1 .

[0027] Three dry soil samples (50 g each) were taken, and 50 mg of functionalized nano-zero-valent iron was added to each sample. The samples were shaken and mixed by a vortexer for 60 minutes and allowed to stand in the air for 1 day.

[0028] Using a xenon lamp as the excitation light source, scanning wavelength 400-1100nm, and tuning the excitation light at 25Hz, the photoacoustic signals of three soils spiked with nano-zero-valent iron were obtained. There was an obvious photoacoustic signal at 417nm, but there was no significant difference between the three soil samples, such as Figure 2 Thus, the present invention can be used for the photoacoustic characterization of nano-zero-valent iron in soil.

[0029] Example 2

[0030] Four portions (50 g each) of the dry soil sample prepared in Example 1 were taken, and 25 mg, 50 mg, 65 mg, and 90 mg of nano-zero-valent iron were added, respectively. The mixture was shaken and mixed by a vortexer for 60 minutes and allowed to stand in air for 1 day.

[0031] Using a xenon lamp as the excitation light source, scanning wavelength 400-1100nm, and 25Hz excitation light tuning to scan four spiked soil samples, four kinds of soil photoacoustic signals spiked with nano-zero-valent iron were obtained, such as Figure 3 The photoacoustic signal integration, the photoacoustic signal integrated intensity or integrated area (Area) has a linear correlation with the spiked nano zero-valent iron content (Content), the linear equation is: Y = 3.614 + 0.236 * X, Y represents Area, X represents Content, the correlation coefficient R = 0.995, as shown in Figure 4 This can be used to estimate the amount of nano-zero-valent iron in soil.

[0032] It should be noted that the technical contents of the present invention described above are only for the purpose of explaining and illustrating the technical essence of the present invention to enable those skilled in the art to understand the technical essence of the present invention. Therefore, the technical contents described above are not intended to limit the substantial protection scope of the present invention. The substantial protection scope of the present invention shall be based on the claims. Those skilled in the art should be aware that any modifications, equivalent substitutions, and improvements based on the substantial spirit of the present invention shall fall within the substantial protection scope of the present invention.

Claims

1. Application of photoacoustic spectroscopy in characterizing nano-zero-valent iron in soil, characterized by: Functionalized nano-zero-valent iron is obtained by modifying nano-zero-valent iron with organic molecules, wherein the organic molecules are any one of the following structures: The soil is obtained by collecting common dryland farmland soil, treating it with a phosphate buffer solution with a pH of 6-8, and then air-drying it; the photoacoustic spectrum is excited by a xenon lamp with a wavelength of 400-1100nm and frequency modulated at 20-30Hz.

2. The use according to claim 1, characterized in that Use the following steps: (1) Collect soil, treat with phosphate buffer solution (pH 6-8), and then air-dry; (2) Calibrated with carbon black powder, the excitation light scanned a xenon lamp with a wavelength of 400-1100 nm and tuned at 20-30 Hz to obtain the soil background photoacoustic signal; (3) Using a xenon lamp as the excitation light source, scanning wavelengths of 400-1100 nm, and tuning the excitation light at 20-30 Hz, the photoacoustic signal of soil spiked with functionalized nano-zero-valent iron was obtained. There was an obvious photoacoustic signal at 410-420 nm, which can be used for the photoacoustic characterization of nano-zero-valent iron in soil.

3. The use according to claim 2, characterized in that The method further includes step (4) using a xenon lamp as an excitation light source, scanning a wavelength of 400-1100 nm, and tuning the excitation light at 20-30 Hz to scan a series of soil samples spiked with functionalized nano-zero-valent iron at different contents, thereby obtaining a series of soil photoacoustic signals spiked with functionalized nano-zero-valent iron, and integrating the photoacoustic signals; performing a linear correlation analysis between the integrated intensity of the photoacoustic signal and the content of the spiked functionalized nano-zero-valent iron, which can be used to estimate the occurrence of nano-zero-valent iron in the soil.

4. The use according to claim 2, characterized in that Step (1) The concentration of the sodium phosphate buffer solution is 0.8-1.2 mM; Step (2) It is calibrated with 100-300 mesh carbon black powder; Step (3) In the soil spiked with functionalized nano-zero-valent iron, 50 mg of functionalized nano-zero-valent iron is added based on 50 g of dry soil.

5. The use according to claim 3, characterized in that Step (4) uses a xenon lamp as an excitation light source, scans a wavelength of 400-1100 nm, and scans a series of spiked soil samples with 20-30 Hz excitation light tuning to obtain a soil photoacoustic signal spiked with functionalized nano-zero-valent iron, and integrates the photoacoustic signal; performs a linear correlation analysis between the integrated intensity of the photoacoustic signal and the content of the spiked functionalized nano-zero-valent iron; and adds 20-100 mg of functionalized nano-zero-valent iron to the soil spiked with functionalized nano-zero-valent iron based on 50 g of dry soil.

6. The use according to claim 3 or 5, characterized in that The soil sample to be tested is collected, and the photoacoustic signal detection is performed. The content of the functionalized nano-zero-valent iron in the soil sample to be tested is calculated according to a linear correlation equation.

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