Manganese sulfide coated manganese carbonate nano composite material and application thereof in detection of heavy metal elements

Abstract

The invention relates to a manganese sulfide coated manganese carbonate nano composite material and application thereof in heavy metal element detection. Wherein the manganese sulfide has good conductivity and a unique electronic structure, the manganese carbonate can provide rich active sites, the composite material formed by combining the manganese sulfide and the manganese carbonate has a special structure and physicochemical properties, the specific surface area is increased, adsorption and enrichment of heavy metal ions are facilitated, electrochemical signal response can be synergistically enhanced, and the electrochemical performance of the composite material is improved. Therefore, high-sensitivity detection of heavy metal ions is realized. After an electrode is modified by the manganese sulfide-coated manganese carbonate nano composite material provided by the invention, the obtained product has good electrochemical activity and conductivity, so that the product has the advantages of wide detection range, high sensitivity, low background current, high selectivity and the like.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional material preparation and pollutant detection, and relates to a manganese carbonate nanocomposite material coated with manganese sulfide and its application in the detection of heavy metal elements. Background Technology

[0002] Mercury ions, as a highly toxic heavy metal ion, pose a serious threat to the ecological environment and human health. They can accumulate in organisms through biomagnification in the food chain, eventually entering the human body. Excessive ingestion of mercury ions can cause irreversible damage to the central nervous system, kidneys, liver, and immune system, leading to a series of serious symptoms such as headaches, insomnia, memory loss, and kidney failure. The concentration of mercury and its compounds in workplace air is strictly controlled to ensure environmental safety and public health.

[0003] In existing technologies, atomic absorption spectrometry and inductively coupled plasma mass spectrometry are commonly used for the detection of heavy metal ions. However, these instruments are not portable and are complex to operate, making them unsuitable for rapid screening and real-time quantitative analysis of heavy metal elements. Electrochemical sensing methods, on the other hand, offer significant advantages such as ease of operation, fast detection speed, high sensitivity, low cost, and the ability to perform rapid on-site detection. By detecting changes in electrochemical signals such as current, potential, or charge, the concentration of target substances can be accurately determined. Therefore, developing a highly sensitive detection method and electrode modification materials that can be effectively applied to the detection of heavy metal ions is of significant practical value. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a manganese carbonate nanocomposite material coated with manganese sulfide and its application in the detection of heavy metal elements.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a manganese carbonate nanocomposite material coated with manganese sulfide.

[0007] Manganese sulfide has good electrical conductivity and a unique electronic structure, while manganese carbonate can provide abundant active sites. The composite material formed by the combination of the two has special structure and physicochemical properties. It not only increases the specific surface area, which is conducive to the adsorption and enrichment of heavy metal ions, but also synergistically enhances the electrochemical signal response, thereby achieving highly sensitive detection of heavy metal ions.

[0008] In a second aspect, a method for preparing manganese carbonate nanocomposite material coated with manganese sulfide according to the first aspect, the preparation method comprising the following steps:

[0009] Manganese salt compounds are mixed with an aqueous ethanol solution to obtain a first solution, and bicarbonate compounds are mixed with water to obtain a second solution. The first and second solutions are combined and stirred to obtain a manganese carbonate support. The manganese carbonate support is mixed with sulfur and heated to obtain the manganese carbonate nanocomposite material coated with manganese sulfide.

[0010] Preferably, the manganese salt compound is selected from any one of manganese sulfate, manganese nitrate, or manganese chloride.

[0011] Preferably, the bicarbonate compound is sodium bicarbonate or potassium bicarbonate.

[0012] Preferably, the concentration of the manganese salt compound in the aqueous ethanol solution is 0.1-0.6 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, etc.

[0013] Preferably, the volume percentage of ethanol in the ethanol-water solution is 20%-50%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0014] Preferably, the concentration of the bicarbonate compound in water is 0.05-0.3 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, etc.

[0015] Preferably, the stirring time is 4-6 hours, for example, 4 hours, 4.2 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc.

[0016] Preferably, after stirring, the mixture is further subjected to centrifugation, removal of supernatant, sediment washing, and drying.

[0017] Preferably, the solvent for washing the precipitate is ethanol and / or water.

[0018] Preferably, the drying temperature is 50-70℃, for example, 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃, 70℃, etc.; and the time is 10-24 h, for example, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 24 h, etc.

[0019] Thirdly, the present invention provides an application of manganese carbonate nanocomposite material coated with manganese sulfide as described in the first aspect in the detection of heavy metal elements.

[0020] Fourthly, the present invention provides a method for detecting heavy metal elements using the nanocomposite material as described in the first aspect, the method comprising the following steps:

[0021] (1) The glassy carbon electrode is modified with the nanocomposite material as described in the first aspect to obtain the MnCO3@MnS modified electrode;

[0022] (2) Add the heavy metal ion standard solution dropwise to the electrolyte of the electrolytic cell and plot the standard curve;

[0023] (3) Place the sample to be tested in an electrolytic cell, and use the MnCO3@MnS modified electrode prepared in step (1) as the working electrode, Ag / AgCl as the reference electrode, and Pt wire as the counter electrode to connect to the electrochemical workstation.

[0024] (4) Under stirring conditions, the content of heavy metal elements in the sample to be tested in the electrolytic cell was measured by square wave anodic stripping voltammetry.

[0025] Preferably, the preparation method of the MnCO3@MnS modified electrode in step (1) specifically includes the following steps:

[0026] ① The surface of the glassy carbon electrode is continuously polished with Al2O3 slurry in descending order of particle size until the electrode surface has a mirror effect.

[0027] ② The glassy carbon electrode polished in step ① was ultrasonically cleaned in water and anhydrous ethanol in sequence, and then dried in a protective atmosphere.

[0028] ③ A perfluorosulfonic acid resin dispersion containing manganese carbonate nanocomposite material (MnCO3@MnS) coated with manganese sulfide as described in the first aspect is uniformly drop-coated onto the surface of the glassy carbon electrode after drying in step ②, and then air-dried to obtain a MnCO3@MnS modified electrode.

[0029] Preferably, the polishing process in step ① specifically involves first polishing the glassy carbon electrode surface with Al2O3 powder slurry with a particle size of 1 μm to 3 μm for 200 cycles, and then polishing the glassy carbon electrode surface with Al2O3 powder slurry with a particle size of 30 to 100 nm for 200 cycles.

[0030] Preferably, the ultrasonic cleaning in step ② has a frequency of 30~50 kHz (e.g., 30 kHz, 35 kHz, 40 kHz, 45 kHz, 50 kHz, etc.), a power of 80~120 W (e.g., 80 W, 90 W, 100 W, 110 W, 120 W, etc.), and a time of 10~15 s / cycle (e.g., 10 s / cycle, 11 s / cycle, 12 s / cycle, 13 s / cycle, 14 s / cycle, 15 s / cycle).

[0031] Preferably, the protective atmosphere is nitrogen or argon.

[0032] Preferably, the amount of perfluorosulfonic acid resin dispersion used in step ③ for drop coating is 0.5~2.5 μL / mm. 2 For example, 0.5 μL / mm 2 0.8 μL / mm 2 1 μL / mm 2 1.2 μL / mm 2 1.5 μL / mm 2 1.8 μL / mm 2 2 μL / mm 2 2.2 μL / mm 2 2.5 μL / mm 2 wait.

[0033] Preferably, the preparation method of the perfluorosulfonic acid resin dispersion containing MnCO3@MnS in step ③ is as follows: adding the MnCO3@MnS into the perfluorosulfonic acid resin aqueous solution and dispersing it by ultrasonication.

[0034] Preferably, the ratio of MnCO3@MnS to the aqueous solution of perfluorosulfonic acid resin is 0.5:1 to 1.5:1, mg / mL, for example, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, etc.

[0035] Preferably, the volume ratio of perfluorosulfonic acid resin to water in the aqueous solution is 1:8 to 1:20, for example, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, etc.

[0036] Preferably, the heavy metal element includes any one of lead, cadmium, or mercury.

[0037] Preferably, the pH of the electrolyte in step (2) is 4 to 6, for example, it can be 4, 4.5, 5, 5.5, 6, etc.

[0038] In this invention, using an electrolyte with a specific pH is crucial for accurate testing. When the pH value is too low, more H+ will be released. + It is ionized and coexists with heavy metal ions; heavy metal ions on the electrode surface are easily dissolved, and if the pH value is too high, OH... − When present in solution, it readily precipitates with heavy metal ions to form metal hydroxides, and the peak current decreases, affecting the accuracy of the test results.

[0039] Preferably, the detection parameters of the square wave anodic stripping voltammetry in step (4) are as follows: enrichment potential is -1.4 to -1.0 V (e.g., -1.4 V, -1.3 V, -1.2 V, -1.1 V, -1.0 V, etc.); enrichment time is 50 to 500 s (e.g., 50 s, 100 s, 150 s, 200 s, 300 s, 400 s, 500 s, etc.); settling time is 5 to 20 s (e.g., 5 s, 8 s, 10 s, 15 s, 20 s, etc.); initial potential is -1.3 to -1.0 V (e.g., -1.3 V, -1.2 V, -1.1 V, -1.0 V, etc.); termination potential is 0.2 to 0.6 V (e.g., 0.2 V, 0.3 V, 0.4 V, 0.5 V, 0.6 V, etc.). The square wave amplitude is 0.02~0.03 V (e.g., 0.02 V, 0.025 V, 0.03 V, etc.); the potential increment is 0.002~0.005 V (e.g., 0.002 V, 0.003 V, 0.004 V, 0.005 V, etc.); the square wave frequency is 20~30 Hz (e.g., 20 Hz, 22 Hz, 25 Hz, 28 Hz, 30 Hz, etc.).

[0040] Preferably, when the heavy metal element is mercury, the detection method specifically includes the following steps:

[0041] (1) The glassy carbon electrode is modified with the nanocomposite material as described in the first aspect to obtain the MnCO3@MnS modified electrode;

[0042] (2) When plotting the standard curve, the mercury standard solution is added dropwise to the electrolyte of the electrolytic cell to obtain a linear concentration of 2~150 μg / L; or when detecting weak acid or neutral mercury-containing wastewater, the mercury-containing wastewater is placed directly in the electrolytic cell; or when detecting acidic mercury-containing wastewater, the acidic mercury-containing wastewater is added dropwise to the electrolyte of the electrolytic cell to adjust the pH value to 4~6; then, the MnCO3@MnS modified electrode is used as the working electrode, Ag / AgCl is used as the reference electrode, and Pt wire is used as the counter electrode and connected to the electrochemical workstation.

[0043] (3) Under stirring conditions, the content of heavy metal mercury ions in the solution of the electrolytic cell is detected by square wave anodic stripping voltammetry.

[0044] Preferably, in step (2), the concentration of the mercury standard solution is 10~500 μg / mL, for example, it can be 10 μg / mL, 50 μg / mL, 100 μg / mL, 200 μg / mL, 300 μg / mL, 400 μg / mL, 500 μg / mL, etc.

[0045] Preferably, in step (2), the volume ratio of the electrolyte to the mercury standard solution is 25:1 to 1:2, mL:μL, for example, it can be 25:1, 10:1, 5:1, 2.5:1, 1:1, 1:2, etc.

[0046] Preferably, in step (2), the electrolyte is an aqueous solution of acetic acid and sodium acetate.

[0047] In step (2), the pH value of the weakly acidic or neutral mercury-containing wastewater is 4.5 to 7.5. The weakly acidic or neutral heavy metal ion-containing wastewater includes natural water bodies.

[0048] In step (2), the pH value of the acidic mercury-containing wastewater is <4.5. The acidic wastewater containing heavy metal ions includes a digestion solution.

[0049] In step (2), the electrochemical workstation is an RST5000 series; the internal solution of the reference electrode Ag / AgCl is a saturated KCl solution.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The manganese carbonate nanocomposite material electrode coated with manganese sulfide provided by this invention exhibits good electrochemical activity and conductivity, resulting in a wide detection range, high sensitivity, low background current, and high selectivity. The MnCO3@MnS modified electrode used in this invention for heavy metal detection demonstrates stability, anti-interference capabilities, and high accuracy. In particular, it exhibits excellent electrochemical response to mercury ions, displaying high sensitivity, low background current, and high selectivity. The mercury recovery rate is 99%–103%, demonstrating high accuracy, with a detection limit as low as 0.342 μg / L. This indicates that using the MnCO3@MnS modified electrode for heavy metal detection provides a new pathway for the rapid detection of heavy metal ions in e-cigarette digestants. Attached Figure Description

[0052] Figure 1 The images show the morphology and mapping of the MnCO3@MnS material prepared in Example 1.

[0053] Figure 2 The square wave anodic stripping voltammetry response curves and working curves of the MnCO3@MnS modified electrode for detecting mercury ions of different concentrations are shown. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0055] Example 1

[0056] This embodiment provides a manganese carbonate nanocomposite material coated with manganese sulfide (MnCO3@MnS), and the preparation method is as follows:

[0057] (1) Dissolve 2.265g of manganese sulfate in 50 mL of 50% ethanol aqueous solution and mix well; add 100 mL of deionized water containing 1.26g of sodium bicarbonate to the mixed solution and stir for 4 h; centrifuge, wash the precipitate alternately with ethanol and deionized water; collect the washed product and dry it under vacuum at 60℃ for 12 h to obtain product MnCO3.

[0058] (2) Take 114.9 mg of MnCO3 powder and 40 mg of sulfur powder and mix and grind them. After grinding, pour the powder into a corundum boat and put it into a tube furnace. Under the conditions of room temperature (25℃), the heating rate is 5℃ / min, the temperature is raised to 300℃ and held for 2 h, then cooled and the product is collected to obtain the MnCO3@MnS.

[0059] Example 2

[0060] This embodiment provides a manganese carbonate nanocomposite material coated with manganese sulfide (MnCO3@MnS), and the preparation method is as follows:

[0061] (1) Dissolve 3.765 g of manganese nitrate tetrahydrate in 50 mL of 40% ethanol aqueous solution and mix well; add 100 mL of deionized water containing 1.26 g of sodium bicarbonate to the mixed solution and stir for 4 h; centrifuge, wash the precipitate alternately with ethanol and deionized water; collect the washed product and vacuum dry at 60 °C for 12 h to obtain product MnCO3.

[0062] (2) Take 114.9 mg of MnCO3 powder and 40 mg of sulfur powder and mix and grind them. After grinding, pour the powder into a corundum boat and put it into a tube furnace. Under the conditions of room temperature (25℃), the heating rate is 5℃ / min, the temperature is raised to 300℃ and held for 2 h, then cooled and the product is collected to obtain the MnCO3@MnS.

[0063] Example 3

[0064] This embodiment provides a manganese carbonate nanocomposite material coated with manganese sulfide (MnCO3@MnS), and the preparation method is as follows:

[0065] (1) Dissolve 2.79 g of manganese chloride tetrahydrate in 50 mL of 20% ethanol aqueous solution and mix well; add 100 mL of deionized water containing 1.5 g of sodium bicarbonate to the mixed solution and stir for 4 h; centrifuge, wash the precipitate alternately with ethanol and deionized water; collect the washed product and dry it under vacuum at 60 °C for 12 h to obtain product MnCO3.

[0066] (2) Take 114.9 mg of MnCO3 powder and 40 mg of sulfur powder and mix and grind them. After grinding, pour the powder into a corundum boat and put it into a tube furnace. Under the conditions of room temperature (25℃), the heating rate is 5℃ / min, the temperature is raised to 300℃ and held for 2 h, then cooled and the product is collected to obtain the MnCO3@MnS.

[0067] Application Example 1

[0068] This application example provides a MnCO3@MnS modified electrode, which is prepared as follows:

[0069] (1) Polish the glass carbon electrode surface 200 times with Al2O3 slurry with a particle size of 1 μm, and then polish the glass carbon electrode surface 100 times with Al2O3 slurry with a particle size of 50 nm until the electrode surface has a mirror effect.

[0070] (2) The glassy carbon electrode polished in step (1) was ultrasonically cleaned for 10 s in deionized water and anhydrous ethanol respectively, and the electrode surface was blown clean with high-purity nitrogen.

[0071] (3) 5 μL of perfluorosulfonic acid resin dispersion (2 mg / mL) containing MnCO3@MnS (Example 1) was uniformly dropped onto the surface of the glassy carbon electrode after drying in step (2), and air-dried naturally to obtain the MnCO3@MnS modified electrode.

[0072] The preparation method of the perfluorosulfonic acid resin dispersion of MnCO3@MnS in (3) is as follows: 2 mg of MnCO3@MnS (Example 1) is added to 1 mL of perfluorosulfonic acid resin aqueous solution (the volume ratio of perfluorosulfonic acid resin: isopropanol: water is 1:13:24), and ultrasonically dispersed for 5 min.

[0073] Application Example 2

[0074] This application example provides a MnCO3@MnS modified electrode, which differs from Application Example 1 only in that MnCO3@MnS (Example 1) is replaced with MnCO3@MnS (Example 2), while the remaining steps and related parameters are the same as in Application Example 1.

[0075] Test Example 1

[0076] This test example demonstrates the material characterization of the MnCO3@MnS nanomaterials prepared in Examples 1-3. The material characterization results for Example 1 are as follows: Figure 1 As shown.

[0077] Test results show that the materials prepared in Examples 1-3 all exhibit a spherical aggregate morphology under a microscope, with a relatively loose overall structure, a rough surface, and obvious porosity and wrinkles. Combined with the elemental mapping diagram, it can be seen that C, N, O, S, and Mn are all distributed in the material, and the distribution areas of each element correspond to the spherical morphology, indicating that these elements are relatively uniformly dispersed in the MnCO3@MnS material. This further corroborates the material's overall coherent spherical structure from the perspective of elemental distribution, providing sufficient surface sites and space for subsequent reactions.

[0078] Test Example 2

[0079] Heavy metal element detection.

[0080] (1) Application Example 1 test

[0081] a. Add the mercury standard solution dropwise to 50 mL of acetic acid-sodium acetate aqueous solution (0.1 mol / L) in the electrolytic cell, ensuring that the Hg concentration in the solution in the electrolytic cell changes after each addition. 2+ The concentrations were 0, 2, 4, 10, 20, 30, 100, and 150 μg / L, respectively. Then, an electrode modified with MnCO3@MnS (Application Example 1) was used as the working electrode, Ag / AgCl (with a saturated KCl solution inside) was used as the reference electrode, and Pt wire was used as the counter electrode. The electrode was connected to an electrochemical workstation RST5060F.

[0082] b. Under stirring conditions at 350 rpm, the Hg of the solution in the electrolytic cell was determined using square wave anodic stripping voltammetry. 2+ The content was determined, and the response curve and working curve of the voltammetry were plotted. The results are as follows: Figure 2 As shown (detection parameters: enrichment potential: -1.3 V, enrichment time: 240 s, settling time: 10 s, initial potential: -1.2 V, termination potential: 0.4 V, square wave amplitude: 0.025 V, potential increment: 0.004 V, square wave frequency: 25 Hz).

[0083] Depend on Figure 2 From a, we can know that Hg 2+ The response curves of the square wave anodic stripping voltammetry (2~150 μg / L) show that, with Hg... 2+With increasing concentration, the dissolution peak current gradually increases, and although the dissolution peak potential gradually shifts positively, this is likely due to the specific interaction between the modified film and the analyte and will not affect the detection of heavy metal ions. Furthermore, due to… Figure 2 As shown in the low-concentration curve (b), the MnCO3@MnS modified electrode exhibits extremely low background current, which is beneficial for detecting the dissolution of target ions and yields a low limit of detection (LOD). Using the formula: LOD = 3σ / S, Hg was calculated. 2+ The detection limit was 0.342 μg / L (S / N=3). The linear relationship for the MnCO3@MnS modified electrode was calculated as follows:

[0084] ;

[0085] This indicates that the MnCO3@MnS material modified electrode provided by the present invention performs excellently when applied to the electrochemical detection of heavy metal ions.

[0086] (2) Application of Example 2 test

[0087] The heavy metal ions in the e-cigarette digestion liquid samples were detected using the MnCO3@MnS modified electrode and inductively coupled plasma mass spectrometry (ICP-MS) provided in Application Example 2. Before testing, the e-cigarette digestion liquid samples were diluted 50-fold with deionized water and the pH was adjusted to 5. The detection method for the MnCO3@MnS modified electrode was as described in (1). The detection results are shown in the table below. The recovery rate was calculated using the formula: (three parallel Hg...) 2+ Average amount found / Hg 2+ concentration.

[0088] Table 1

[0089]

[0090] According to the results in the table, in Hg 2+ Within the concentration range of 0–50 μg / L, Pb 2+ Cd 2+ The recovery rate was 92.3%–100.6%, indicating that the MnCO3@MnS modified electrode exhibited good performance in the detection of actual samples of e-cigarette digestion liquid, and showed good resistance to Hg in complex environmental systems. 2+ It also exhibits good selectivity. Furthermore, the detection results of the MnCO3@MnS modified electrode provided by this invention are similar to those of ICP-MS, demonstrating that the modified electrode has good stability, anti-interference, and accuracy when applied in practical environments.

[0091] The applicant declares that the technical solution of this invention is illustrated by the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

[0092] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0093] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A manganese carbonate nanocomposite material coated with manganese sulfide.

2. A method for preparing manganese carbonate nanocomposite material coated with manganese sulfide according to claim 1, characterized in that, The preparation method comprises the following steps: Manganese salt compounds are mixed with an aqueous ethanol solution to obtain a first solution, and bicarbonate compounds are mixed with water to obtain a second solution. The first and second solutions are combined and stirred to obtain a manganese carbonate support. The manganese carbonate support is mixed with sulfur and heated to obtain the manganese carbonate nanocomposite material coated with manganese sulfide.

3. The preparation method according to claim 2, characterized in that, The manganese salt compound is selected from any one of manganese sulfate, manganese nitrate or manganese chloride; Preferably, the bicarbonate compound is sodium bicarbonate or potassium bicarbonate.

4. The preparation method according to claim 2, characterized in that, The concentration of the manganese salt compound in the aqueous ethanol solution is 0.1-0.6 mol / L; Preferably, the volume percentage of ethanol in the aqueous ethanol solution is 20%-50%; Preferably, the concentration of the bicarbonate compound in water is 0.05-0.3 mol / L.

5. The preparation method according to claim 2, characterized in that, The stirring time is 4-6 hours; Preferably, after stirring, the mixture is further subjected to centrifugation, removal of supernatant, sediment washing, and drying. Preferably, the solvent for washing the precipitate is ethanol and / or water; Preferably, the drying process is carried out at a temperature of 50-70°C for 10-24 hours.

6. The application of a manganese carbonate nanocomposite material coated with manganese sulfide as described in claim 1 in the detection of heavy metal elements.

7. A method for detecting heavy metal elements using the nanocomposite material as described in claim 1, characterized in that, The method includes the following steps: (1) The glassy carbon electrode is modified with the nanocomposite material as described in claim 1 to obtain the MnCO3@MnS modified electrode; (2) Add the heavy metal ion standard solution dropwise to the electrolyte of the electrolytic cell and plot the standard curve; (3) Place the sample to be tested in an electrolytic cell, and use the MnCO3@MnS modified electrode prepared in step (1) as the working electrode, Ag / AgCl as the reference electrode, and Pt wire as the counter electrode to connect to the electrochemical workstation. (4) Under stirring conditions, the content of heavy metal elements in the sample to be tested in the electrolytic cell was measured by square wave anodic stripping voltammetry.

8. The method according to claim 7, characterized in that, The heavy metal element includes any one of lead, cadmium, or mercury.

9. The method according to claim 7, characterized in that, The pH of the electrolyte in step (2) is 4 to 6.

10. The method according to claim 7, characterized in that, The detection parameters for the square wave anodic stripping voltammetry in step (4) are as follows: enrichment potential is -1.4 to -1.0 V; enrichment time is 50 to 500 s; settling time is 5 to 20 s; initial potential is -1.3 to -1.0 V; termination potential is 0.2 to 0.6 V; square wave amplitude is 0.02 to 0.03 V; potential increment is 0.002 to 0.005 V; and square wave frequency is 20 to 30 Hz.

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