Method for detecting available heavy metal elements in soil
By using iron sulfide nanomaterials to modify paper substrates for enrichment and precipitation of soil extracts, combined with LIBS technology, the problem of insufficient sensitivity in traditional detection techniques was solved, achieving high sensitivity and accuracy in the detection of available heavy metal elements in soil.
Patent Information
- Application Number
- CN202511925647.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-19
- Publication Date
- 2026-02-24
AI Technical Summary
Traditional detection techniques cannot achieve high-sensitivity detection of available heavy metal elements in soil, and LIBS technology is difficult to effectively detect metal chelates.
Iron sulfide nanomaterials were used to modify paper substrates to enrich and precipitate soil extracts obtained after UV photolysis. LIBS technology was then used for detection to eliminate organic matrix interference and improve signal quality.
It achieves high sensitivity and accuracy in detecting available heavy metal elements in soil, overcomes the plasma quenching effect in traditional liquid analysis, and improves the detection limit.
Smart Images
Figure CN121558722A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of analytical testing technology, and in particular to a method for detecting available heavy metal elements in soil. Background Technology
[0002] The bioavailable components of heavy metals copper (Cu) and cadmium (Cd) have a crucial impact on their environmental behavior. These bioavailable components typically account for 5% to 50% of their total composition and directly affect several important areas, including the safe use of farmland, the remediation of industrial contaminated sites, and the formulation of environmental standards. The proportion of bioavailable components more accurately reflects environmental risk. High proportions of bioavailable Cu and Cd can have significant negative impacts, including causing compound pollution in crops and enhancing the inhibition of soil microbial activity. Therefore, the synergistic detection of bioavailable Cu and Cd is crucial. This is a necessary requirement for addressing compound pollution and ensuring the safety of the soil-crop-human system.
[0003] Traditional detection techniques suffer from insufficient sensitivity and low preprocessing efficiency, failing to meet the demands of rapid on-site testing. Spectroscopic analysis methods, however, can rapidly analyze soil samples using instruments such as spectrometers, and are therefore widely used in soil elemental analysis. Laser-induced breakdown spectroscopy (LIBS), as a rapid elemental detection method, features simple sample preparation, the ability to obtain multiple elemental information in a single test, and is non-destructive or minimally invasive. Therefore, it has experienced rapid development in the field of soil testing and demonstrates promising application prospects.
[0004] However, because bioavailable elements need to be extracted from the soil, and the resulting metal chelates have high excitation energies, LIBS technology struggles to achieve high-sensitivity detection. Therefore, given the urgent need for accurate detection of bioavailable heavy metals in soil, developing a rapid and highly sensitive detection method based on LIBS technology is crucial. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a method for detecting available heavy metal elements in soil. This invention enriches and precipitates available heavy metal elements in soil leachate after ultraviolet photolysis by modifying paper substrate with iron sulfide nanomaterials, followed by detection using LIBS technology, achieving rapid detection of available heavy metal elements Cu and Cd in soil with high sensitivity and high accuracy.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] In a first aspect, the present invention provides a method for detecting available heavy metal elements in soil, the method comprising the following steps:
[0008] (1) Soil samples and soil extractants are mixed and extracted to obtain an extract; the extract is mixed with an oxidant and photolyzed to obtain the sample to be tested;
[0009] (2) The modified paper base of iron sulfide nanomaterials is mixed with the sample to be tested in step (1) to enrich and precipitate the available heavy metal elements. Then, the modified paper base of iron sulfide nanomaterials after enrichment and precipitation is detected by laser-induced breakdown spectroscopy. Based on the calibration curve of available heavy metal elements, the content of available heavy metal elements in the soil is obtained.
[0010] In this invention, the target available metal elements in soil samples are first extracted, followed by oxidation and photolysis. The ultraviolet photolysis technology eliminates interference from the organic matrix, allowing the extracted metal chelates to be fully decomposed into metal oxides and metal ions, thus improving the quality of the subsequent LIBS signal. Then, the paper substrate is modified with iron sulfide nanomaterials to enrich and precipitate the target metal elements. The resulting solid-state detection form overcomes the plasma quenching effect in traditional liquid analysis and a series of problems existing in LIBS technology when detecting liquids, improving the element detection limit and achieving high sensitivity and accuracy in detecting available metal elements in soil.
[0011] Preferably, the heavy metal element includes Cu and / or Cd.
[0012] Preferably, the soil extractant in step (1) comprises an aqueous solution of ethylenediaminetetraacetic acid (EDTA) and / or a buffer solution of diethylenetriaminepentaacetic acid-calcium chloride-triethanolamine (DTPA-CaCl2-TEA).
[0013] Preferably, the concentration of the aqueous solution of ethylenediaminetetraacetic acid is 1-5 mM (e.g., it can be 1 mM, 2 mM, 3 mM, 4 mM, 5 mM, etc.).
[0014] Preferably, the mass ratio of the soil sample to the soil extractant in step (1) is 1:2 to 1:10 (for example, it can be 1:2, 1:4, 1:6, 1:8, 1:10, etc.).
[0015] Preferably, the extraction method in step (1) includes oscillation extraction.
[0016] Preferably, the oscillation extraction time is 10-90 min (e.g., 10 min, 20 min, 40 min, 60 min, 80 min, 90 min, etc.).
[0017] In this invention, when the soil extractant is an aqueous solution of ethylenediaminetetraacetic acid, the mass ratio of the soil sample to the soil extractant in step (1) is 1:5-1:10, and the shaking extraction time is 60-90 min; when the soil extractant is a diethylenetriaminepentaacetic acid-calcium chloride-triethanolamine buffer solution, the mass ratio of the soil sample to the soil extractant in step (1) is 1:2-1:4, and the shaking extraction time is 10-15 min.
[0018] Preferably, the oxidant in step (1) includes hydrogen peroxide and / or sodium persulfate.
[0019] Preferably, the photolysis time in step (1) is 20-30 min (e.g., 20 min, 22 min, 25 min, 28 min, 30 min, etc.).
[0020] Preferably, the preparation method of the iron sulfide nanomaterial modified paper substrate in step (2) includes the following steps:
[0021] (a) The paper base and FeCl3 solution were mixed and then dried to obtain intermediate one;
[0022] (b) Intermediate I, NaBH4 solution and Na2S solution are mixed and reacted, and then dried to obtain the iron sulfide nanomaterial modified paper base.
[0023] Preferably, in steps (a) and (b), the paper base has a size of 1 cm. 2 The FeCl3 solution has a concentration of 30-60 mM (e.g., 30 mM, 40 mM, 50 mM, 60 mM, etc.) and a volume of 10-20 mL (e.g., 10 mL, 12 mL, 15 mL, 18 mL, 20 mL, etc.). The NaBH4 solution has a concentration of 200-300 mM (e.g., 200 mM, 220 mM, 250 mM, 280 mM, 300 mM, etc.) and a volume of 10-15 mL (e.g., 10 mL, 11 mL, 12 mL, 13 mL, 14 mL, 15 mL, etc.). The Na2S solution has a concentration of 25-40 mM (e.g., 25 mM, 30 mM, 35 mM, 40 mM, etc.) and a volume of 10-15 mL (e.g., 10 mL, 11 mL, 12 mL, 13 mL, 14 mL, 15 mL, etc.).
[0024] Preferably, the mixing process in step (a) further includes an oscillation process.
[0025] Preferably, the oscillation process takes 5-10 minutes (e.g., 5 minutes, 6 minutes, 7 minutes, 8 minutes, 10 minutes, etc.).
[0026] Preferably, the reaction in step (b) is carried out under shaking treatment.
[0027] Preferably, the temperature of the reaction in step (b) is 20-40°C (e.g., 20°C, 25°C, 30°C, 35°C, 40°C, etc.), and the time is 10-15 min (e.g., 10 min, 11 min, 12 min, 14 min, 15 min, etc.).
[0028] Preferably, the reaction in step (b) is carried out under the protection of an inert gas.
[0029] Preferably, the inert gas includes nitrogen and / or argon.
[0030] Preferably, the enrichment precipitation in step (2) is carried out under shaking treatment.
[0031] Preferably, the oscillation process takes 10-15 minutes (e.g., 10 minutes, 11 minutes, 12 minutes, 14 minutes, 15 minutes, etc.).
[0032] Compared with the prior art, the present invention has at least the following beneficial effects:
[0033] (1) The pretreatment method of the present invention before using LIBS technology to detect the target available metal elements achieves efficient extraction and selective enrichment. Among them, the ultraviolet photolysis technology eliminates the interference of organic matrix, destroys the chelation morphology between EDTA and Cu and Cd, and releases metal ions, thereby ensuring that the iron sulfide nanomaterial modified paper base can effectively capture Cu and Cd, and further improve the LIBS signal quality. The iron sulfide nanomaterial modified paper base can enrich and precipitate the target elements, improve the element detection limit, and realize high sensitivity and accuracy detection of available elements in soil.
[0034] (2) The solid detection form formed by the present invention overcomes the plasma quenching effect in traditional liquid analysis and a series of problems existing in LIBS technology when detecting liquids. Attached Figure Description
[0035] Figure 1 This is the Cd calibration curve from Example 1.
[0036] Figure 2 This is the Cu calibration curve from Example 1.
[0037] Figure 3 This is a flowchart illustrating the detection method in Example 1.
[0038] Figure 4 This is a comparison of the spectral signals of Cd and Cu detected by LIBS in Example 1 (after photolysis) and Comparative Example 1 (before photolysis).
[0039] Figure 5 This is a comparison of the spectral signals of Cd and Cu detected by LIBS in Example 1 (paper base 1), Example 2 (paper base 2), and Comparative Example 2 (glass slide). Detailed Implementation
[0040] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.
[0041] Preparation Example 1
[0042] This preparation example provides a paper base modified with iron sulfide nanomaterials, and the preparation method includes the following steps:
[0043] (1) Prepare a FeCl3 aqueous solution with a concentration of 40mM and a volume of 15mL. Place the paper base cut to a size of 1cm×1cm into the solution and shake gently for 8min. Then dry it for later use.
[0044] (2) Take a 250mM NaBH4 aqueous solution with a volume of 12mL and mix it with an equal volume of a 30mM Na2S·9H2O aqueous solution. Then, immerse the dried FeCl3-loaded paper base into this mixed solution. Under the conditions of continuous inert gas (nitrogen) and room temperature (25℃), gently shake the reaction for 10 minutes. After the reaction is completed, take out the paper base and dry it again in vacuum drying to finally obtain the iron sulfide nanomaterial modified paper base 1.
[0045] Preparation Example 2
[0046] This preparation example provides a paper base modified with iron sulfide nanomaterials, and the preparation method includes the following steps:
[0047] (1) Prepare a FeCl3 aqueous solution with a concentration of 60mM and a volume of 10mL. Place the paper base cut to a size of 1cm×1cm into the solution and shake gently for 5min. Then dry it for later use.
[0048] (2) Take a 300mM NaBH4 aqueous solution with a volume of 10mL and mix it with an equal volume of a 40mM Na2S·9H2O aqueous solution. Then, immerse the dried FeCl3-loaded paper base into this mixed solution. Under the conditions of continuous inert gas (nitrogen) and room temperature (25℃), gently shake the reaction for 10 minutes. After the reaction is completed, take out the paper base and dry it again in vacuum drying to finally obtain the iron sulfide nanomaterial modified paper base 2.
[0049] In the following examples, the concentrations of DTPA, CaCl2, and TEA in the soil extractant DTPA-CaCl2-TEA aqueous solution were 5 mM, 10 mM, and 100 mM, respectively; the concentration of the EDTA aqueous solution was 2 mM.
[0050] Example 1
[0051] This embodiment provides a method for detecting available heavy metal elements in soil, including the following steps:
[0052] (1) Mix the soil sample and DTPA-CaCl2-TEA aqueous solution at a mass ratio of 1:3 and shake for 10 min. Then centrifuge at 8000 rpm for 10 min and take the supernatant to obtain the extract. Add 400 mM and 0.6 mL of oxidant H2O2 to the extract and photolyze for 25 min to obtain the sample to be tested.
[0053] (2) Mix the iron sulfide nanomaterial modified paper base 1 (provided in preparation example 1) with the sample to be tested in step (1), place it on a shaker and shake it slightly for 10 min to allow it to react fully with the sample solution to obtain the paper base that successfully enriches and precipitates the target metal element. Take out the paper base, dry it and stick it on the surface of a glass slide. Use a LIBS instrument to detect it and analyze the spectral signals at CuⅠ 324.75 nm and Cd Ⅱ 226.5 nm. Based on the calibration curves of CuⅠ and Cd Ⅱ, the contents of Cu and Cd in the soil are obtained.
[0054] Calibration curves for Cu I and Cd II were obtained by gradient addition of Cu and Cd standard solutions of different concentrations to equal sample aliquots using the standard addition method. After photolysis, the target elements were enriched by adsorption precipitation on a paper substrate, followed by detection using LIBS technology. Based on this, calibration curves were established, and the accurate curve equations and original sample concentrations were calculated. The Cd calibration curve is shown below. Figure 1 As shown, the Cu calibration curve is as follows: Figure 2 As shown.
[0055] The flowchart of the detection method in Example 1 is shown below. Figure 1 As shown.
[0056] Example 2
[0057] This embodiment provides a method for detecting available heavy metal elements in soil, including the following steps:
[0058] (1) Mix the soil sample and DTPA-CaCl2-TEA aqueous solution at a mass ratio of 1:4 and shake for 15 min. Then centrifuge at 10000 rpm for 5 min and take the supernatant to obtain the extract. Add 500 mM and 0.7 mL of oxidant H2O2 to the extract and photolyze for 20 min to obtain the sample to be tested.
[0059] (2) Mix the iron sulfide nanomaterial modified paper base 2 (provided in preparation example 2) with the sample to be tested in step (1), place it on a shaker and shake it slightly for 15 min to allow it to react fully with the sample solution to obtain the paper base that successfully enriches and precipitates the target metal element. Take out the paper base, dry it and stick it on the surface of a glass slide. Use a LIBS instrument to detect it and analyze the spectral signals at CuⅠ 324.75 nm and Cd Ⅱ 226.5 nm. Based on the calibration curves of CuⅠ and Cd Ⅱ, the contents of Cu and Cd in the soil are obtained.
[0060] Comparative Example 1
[0061] This comparative example provides a method for detecting available heavy metal elements in soil. The only difference between this method and Example 1 is that no oxidant is added and no photolysis (light-avoided oxidation) is performed in step (1). Otherwise, the method is the same as in Example 1.
[0062] Comparative Example 2
[0063] This comparative example provides a method for detecting available heavy metal elements in soil. The only difference between this method and Example 1 is that in step (2), the paper base modified with iron sulfide nanomaterials is not used for enrichment and precipitation. Instead, the sample solution to be tested in step (1) is directly dropped onto a glass slide, dried, and then detected using a LIBS instrument. Other steps are the same as in Example 1.
[0064] Test case
[0065] The comparison of the spectral signals of Cd and Cu detected by LIBS in Example 1 (after photolysis) and Comparative Example 1 (before photolysis) is shown in the figure below. Figure 4 As shown, the LIBS signal is stronger after UV photolysis, indicating that the UV photolysis step can effectively release Cd and Cu ions and improve the enrichment and precipitation ability of the paper substrate.
[0066] The spectral signals of Cd and Cu detected by LIBS in Example 1 (paper base 1), Example 2 (paper base 2), and Comparative Example 2 (glass slide) are compared as follows: Figure 5 As shown, the LIBS signal intensity of Cd and Cu elements in soil leachate adsorbed and precipitated by modifying paper-based materials with iron sulfide nanomaterials is higher.
[0067] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A method for detecting available heavy metal elements in soil, characterized in that, The detection method includes the following steps: (1) Soil samples and soil extractants are mixed and extracted to obtain an extract; the extract is mixed with an oxidant and photolyzed to obtain the sample to be tested; (2) The modified paper base of iron sulfide nanomaterials is mixed with the sample to be tested in step (1) to enrich and precipitate the available heavy metal elements. Then, the modified paper base of iron sulfide nanomaterials after enrichment and precipitation is detected by laser-induced breakdown spectroscopy. Based on the calibration curve of available heavy metal elements, the content of available heavy metal elements in the soil is obtained.
2. The detection method according to claim 1, characterized in that, The heavy metal elements include Cu and / or Cd.
3. The detection method according to claim 1 or 2, characterized in that, The soil extractant in step (1) includes an aqueous solution of ethylenediaminetetraacetic acid and / or a diethylenetriaminepentaacetic acid-calcium chloride-triethanolamine buffer solution; Preferably, the concentration of the aqueous solution of ethylenediaminetetraacetic acid is 1-5 mM.
4. The detection method according to any one of claims 1-3, characterized in that, The mass ratio of the soil sample to the soil extractant in step (1) is 1:2 to 1:10; Preferably, the extraction method in step (1) includes oscillation extraction; Preferably, the oscillation extraction time is 10-90 minutes.
5. The detection method according to any one of claims 1-4, characterized in that, The oxidant in step (1) includes hydrogen peroxide and / or sodium persulfate; Preferably, the photolysis time in step (1) is 20-30 min.
6. The detection method according to any one of claims 1-5, characterized in that, The preparation method of the iron sulfide nanomaterial modified paper substrate in step (2) includes the following steps: (a) The paper base and FeCl3 solution were mixed and then dried to obtain intermediate one; (b) Intermediate I, NaBH4 solution and Na2S solution are mixed and reacted, and then dried to obtain the iron sulfide nanomaterial modified paper base.
7. The detection method according to claim 6, characterized in that, In steps (a) and (b), the paper base has a size of 1 cm. 2 The FeCl3 solution has a concentration of 30-60 mM and a volume of 10-20 mL, the NaBH4 solution has a concentration of 200-300 mM and a volume of 10-15 mL, and the Na2S solution has a concentration of 25-40 mM and a volume of 10-15 mL.
8. The detection method according to claim 6 or 7, characterized in that, The mixing process described in step (a) further includes an oscillation process; Preferably, the oscillation process takes 5-10 minutes.
9. The detection method according to any one of claims 6-8, characterized in that, The reaction described in step (b) is carried out under shaking. Preferably, the reaction in step (b) is carried out at a temperature of 20-40°C for 10-15 minutes. Preferably, the reaction in step (b) is carried out under the protection of an inert gas; Preferably, the inert gas includes nitrogen and / or argon.
10. The detection method according to any one of claims 1-9, characterized in that, The enrichment precipitation described in step (2) is carried out under shaking treatment; Preferably, the oscillation process takes 10-15 minutes.