Electrolyte interference resistant solid mercury ion electrode, preparation method and use method

Abstract

The invention discloses a solid mercury ion electrode resistant to electrolyte interference, a preparation method and a use method, and belongs to the technical field of electrode preparation. The electrode sequentially comprises a gold wire serving as a base material, a gold amalgam transition conducting layer, a mercury / mercury selenide sensitive film or a mercury / mercuric sulfide sensitive film and a nano microporous polyvinyl chloride film from inside to outside. Firstly, a gold amalgam transition conducting layer is formed on the surface of a gold wire through an electroplating method or a soaking method; immersing in a sodium selenide or sodium sulfide solution to form a mercury / mercury selenide sensitive film or a mercury / mercury sulfide sensitive film on the surface to obtain a mercury ion electrode blank; vertically dipping the mercury ion electrode blank into the film-forming agent, and standing vertically with the detection end facing upwards, so that a nano-microporous polyvinyl chloride film is generated on the surface of the mercury ion electrode blank; and finally, washing to remove the residual film-forming agent, and drying to obtain the electrolyte interference resistant solid mercury ion electrode. The electrode is firm in structure and small in size, is matched with a reference electrode for use, and is sensitive in response to mercury ions in a solution to be detected.

Description

Technical Field

[0001] The invention belongs to the technical field of electrode preparation, and in particular relates to a solid mercury ion electrode resistant to electrolyte interference, and a preparation and use method thereof. Background Art

[0002] Since the Industrial Revolution, the content of mercury in the global atmosphere, water and soil has increased by about three times. Mercury often pollutes the air in the form of vapor. Mercury and its compounds are very toxic and can enter the human body through different pathways such as the respiratory tract, skin or digestive tract. After entering the human body, mercury will be distributed to various organs and tissues throughout the body, including the liver, kidneys, brain, heart and bone marrow, mainly damaging the nervous system, especially the central nervous system and brain tissue, which may cause fetal malformation or intellectual disability. Long-term exposure to a high-mercury environment may cause brain damage and death. The toxicity of mercury is cumulative and often takes several years or more than ten years to react.

[0003] Spectrometers, mass spectrometers, chromatographs, etc. have high sensitivity in detecting mercury ions, but they have many limitations such as large equipment, complex operation, high cost, and unsuitability for in-situ analysis. In order to overcome these problems, it is particularly important to develop a new type of mercury ion selective electrode. This electrode not only needs to achieve high sensitivity and high selectivity for mercury ion detection in complex environments, but also needs to effectively resist electrolyte interference to meet the needs of online monitoring of mercury pollutants in water bodies, providing an economical and efficient solution. Summary of the invention

[0004] The purpose of the present invention is to meet the demand for online detection of mercury pollutants in water bodies and to provide a solid-state mercury ion electrode resistant to electrolyte interference, and a preparation and use method thereof.

[0005] The specific technical solutions adopted by the present invention are as follows:

[0006] In a first aspect, the present invention provides a solid-state mercury ion electrode resistant to electrolyte interference, which comprises, from the inside to the outside, a gold wire as a substrate, a gold amalgam transition conductive layer, a mercury / mercury selenide sensitive membrane or a mercury / mercury sulfide sensitive membrane, and a nanoporous polyvinyl chloride membrane.

[0007] The core of the electrode is the electrode substrate and connecting conductor. It is recommended to use gold wire with a diameter of 0.2 to 0.5 mm. Gold wire is selected as the electrode substrate and conductor because it has very low impedance. Gold amalgam, as an alloy, can be tightly combined with gold wire, which also reduces the interface impedance between the composite film and the substrate.

[0008] The nanoporous polyvinyl chloride (PVC) membrane located on the outermost layer of the electrode plays a shielding and protective role. Due to the presence of a large amount of dissolved salts in seawater, high concentrations of anions and cations will interfere with the selectivity of the mercury ion sensitive membrane to mercury ions in seawater. The nanoporous polyvinyl chloride (PVC) membrane coated on the surface of the electrode is hydrophobic and can block hydrophilic anions and cations outside the electrode without affecting the performance of the electrode, while mercury ions can selectively pass through. In addition, the nanoporous polyvinyl chloride (PVC) membrane can also slow down chemical corrosion and extend the service life of the electrode.

[0009] In a second aspect, the present invention provides a method for preparing a solid mercury ion electrode resistant to electrolyte interference, the specific steps are as follows:

[0010] S1: Using electroplating or immersion method, a gold amalgam transition conductive layer is formed at the position where the gold wire is used as an electrode probe;

[0011] S2: immersing the gold wire with a gold-mercury amalgam transition conductive layer on the surface into a sodium selenide or sodium sulfide solution for reaction, forming a mercury / mercury selenide sensitive film or a mercury / mercury sulfide sensitive film outside the gold-mercury amalgam transition conductive layer, and obtaining a mercury ion electrode embryo;

[0012] S3: vertically dipping the mercury ion electrode embryo obtained in step S2 into a film-forming agent, and standing it upright with the detection end facing upward, so that a nano-microporous polyvinyl chloride film is formed on the surface of the mercury ion electrode embryo; the solute in the film-forming agent is polyvinyl chloride, and the solvent is a mixture of tetrahydrofuran and cyclohexanone;

[0013] S4: placing the mercury ion electrode embryo with nanoporous polyvinyl chloride membrane obtained in step S3 in an extracting solution to remove the residual film-forming agent; and obtaining a solid mercury ion electrode resistant to electrolyte interference after drying.

[0014] Preferably, the electroplating method in step S1 is as follows: using an electrochemical workstation, in a 0.01M HgSO4 solution containing 3.3% concentrated sulfuric acid, the working electrode is connected to a gold-plated wire, the counter electrode is connected to another gold wire, and the reference electrode is connected to an Ag / Ag2S electrode, and the parameters are set as follows: step = 1, voltage -1.2V, sensitivity 10 -3 A / V, electroplating time 300 seconds, a gold amalgam transition conductive layer is formed on the surface of the gold-plated wire.

[0015] Preferably, the immersion method in step S1 is to immerse the gold wire in liquid mercury for 30 to 60 minutes.

[0016] Preferably, the concentration of the sodium selenide or sodium sulfide solution in step S2 is 0.05-0.1M.

[0017] Preferably, the mass ratio of tetrahydrofuran to cyclohexanone in the film-forming agent in step S3 is 1:(2-3); and the mass concentration of polyvinyl chloride in the film-forming agent is 5%-10%.

[0018] Preferably, in step S3, after the mercury ion electrode embryo is dipped in the film-forming agent, the probe end is placed upright and allowed to stand for 10 to 30 minutes.

[0019] Preferably, the extractant in step S4 is methanol or ethanol, and the mercury ion electrode embryo with nanoporous polyvinyl chloride membrane is placed in methanol or ethanol for 5 to 15 minutes to remove the residual film-forming agent.

[0020] In a third aspect, the present invention provides a solid mercury ion electrode prepared by the method for preparing a solid mercury ion electrode according to the first aspect.

[0021] In a fourth aspect, the present invention provides a method for using a solid-state mercury ion electrode that is resistant to electrolyte interference, wherein the solid-state mercury ion electrode described in the first aspect or the third aspect is used as a working electrode, and an Ag / Ag2Se or Ag / Ag2S electrode is used as a reference electrode. The working electrode and the reference electrode are placed in a test solution containing mercury ions, and the potential difference between the working electrode and the reference electrode is measured; the concentration of mercury ions in the test solution is obtained by conversion using a calibration formula.

[0022] Usually, the ion selective electrode uses Ag / AgCl electrode as the reference electrode, but in the environment with high ionic strength, such as seawater, salt lake and other high salinity environments, the dissolved Cl in the water - Ions will form a response on the Ag / AgCl electrode, interfering with the potential signal between the reference electrode and the working electrode. In addition, carbonate, sulfate, phosphate, which are common in natural water bodies, and hydrogen sulfide in reducing water bodies, can all combine with silver, and the solubility product of the formed chemical is higher than that of silver chloride, so they can interfere with the Ag / AgCl electrode and corrode the sensitive membrane of the electrode. The solubility product of Ag2Se is 63.7, and the solubility product of Ag2S is 50.1, which are much higher than other silver salt compounds. Therefore, when using Ag / Ag2Se or Ag / Ag2S electrodes as reference electrodes, the possibility of interference from other anions is theoretically very small. This is the theoretical basis for the electrode pairs with Ag / Ag2Se and Ag / Ag2S electrodes as reference electrodes to have higher resistance to electrolyte interference.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The solid-state mercury ion electrode resistant to electrolyte interference provided by the present invention is a fully solid structure and does not contain an internal reference electrolyte solution. The electrode is compact and has a solid structure. The outermost nanoporous polyvinyl chloride membrane can shield the interference of the water-soluble electrolyte in the solution to be tested on the ion selective membrane.

[0025] (2) In terms of usage, Ag / Ag2Se or Ag / Ag2S electrode is used as the reference electrode to avoid interference of chloride ions and other anions in the water body to the reference electrode, thereby improving the anti-interference ability of the detection electrode pair. The mercury ion electrode provided by the present invention and the matching reference electrode are suitable for detecting the content of dissolved mercury ions in various water media, and have a wide range of uses in water environment monitoring, mercury mineralization anomaly detection, and real-time online detection in the field of chemistry and chemical engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the solid mercury ion electrode prepared in Example 1, with a magnification of 300 times;

[0027] Figure 2 This is a scanning electron microscope image of the solid mercury ion electrode prepared in Example 1, with a magnification of 5000 times;

[0028] Figure 3 The EDS spectrum analysis result of the surface of the solid mercury ion electrode prepared in Example 1;

[0029] Figure 4 The solid mercury ion electrode in Example 3 is 10 -3 M, 10 -4 M, 10 -5 M, 10 -6 M H 2+ Calibration results in solution;

[0030] Figure 5 is the calibration curve in Example 3;

[0031] Figure 6 This is the test result of the solid mercury ion electrode on the mercury element standard solution in Example 3. DETAILED DESCRIPTION

[0032] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0033] Example 1

[0034] This embodiment provides a method for preparing a solid mercury ion electrode resistant to electrolyte interference, and the specific steps are as follows:

[0035] (1) Cut a 40mm long silver wire with a diameter of 0.5mm, and polish the surface of the silver wire with sandpaper with a polishing degree of 1000 mesh and 5000 mesh respectively. After polishing, place it in 0.1M nitric acid solution, acetone and ultrapure water for ultrasonic cleaning for 10 minutes to remove the oxide layer and oil stains on the metal surface. After cleaning, use dust-free paper to absorb the surface moisture. Use a function signal generator as a power supply, connect the silver wire to the negative pole of the function signal generator, the positive pole to the positive pole of the diode, and the negative pole of the diode to the anode silver wire. The silver wire to be plated and the anode silver wire are placed in a silver nitrate solution with a concentration of 0.01M. The working parameters are set as: sine wave, voltage 1V, frequency 50Hz, and electroplating time 60 seconds. A silver wire with nanosilver plated on the surface is obtained. The part plated with nanosilver was immersed in a 0.1M sodium sulfide solution (pH=10) for 30 minutes to form an Ag2S film on the surface of the nanosilver. The Ag / Ag2S reference electrode was obtained by washing with deionized water and drying.

[0036] (2) Cut a 40 mm long gold wire with a diameter of 0.2 mm and polish the surface of the gold wire with sandpaper with a polishing degree of 5000 mesh. After polishing, ultrasonically clean the wire in 1M nitric acid solution, acetone and ultrapure water for 10 minutes in sequence. After cleaning, dry the surface moisture with dust-free paper.

[0037] (3) Using an electrochemical workstation, chronoamperometry was used in a 0.01 M HgSO4 solution (containing 3.3% concentrated sulfuric acid). The working electrode was connected to a gold-plated wire, the counter electrode was connected to another gold wire, and the reference electrode was connected to an Ag / Ag2S electrode. Step = 1, voltage -1.2 V, sensitivity 10 -3 A / V, electroplating time 300 seconds, a gold-mercury transition conductive layer is formed on the surface of the gold wire.

[0038] (4) The gold wire with the gold-mercury amalgam transition conductive layer formed on the surface is immersed in a 0.01 M sodium sulfide solution (pH = 12) for 0.5 hours to form a mercury / mercury sulfide sensitive film outside the gold-mercury amalgam transition conductive layer; the wire is washed with deionized water and dried to obtain a mercury ion electrode embryo.

[0039] (5) Cyclohexanone and tetrahydrofuran are mixed in a mass ratio of 1:2 to obtain a mixed solvent; 0.5 g of polyvinyl chloride (PVC) is dissolved in 9.5 g of the mixed solvent, and magnetic stirring is performed until it is completely dissolved to obtain a film-forming agent with a concentration of 5%. The film-forming agent solution is dipped into a mercury ion electrode embryo, and the electrode embryo is placed upright with the detection end facing upward at room temperature for 10 minutes, and a nanoporous polyvinyl chloride film is formed on the surface of the mercury ion electrode embryo;

[0040] (6) placing the mercury ion electrode embryo with the nanoporous polyvinyl chloride membrane in methanol for 5 minutes to remove the residual film-forming agent; and after drying, obtaining a solid mercury ion electrode resistant to electrolyte interference.

[0041] The solid mercury ion electrode resistant to electrolyte interference prepared in Example 1 was subjected to scanning electron microscopy and energy spectrum analysis:

[0042] Figure 1 This is a scanning electron microscope image of the solid-state mercury ion electrode that is resistant to electrolyte interference. The magnification is 300 times, and the overall morphology of the gold wire can be seen. Figure 2 This is a scanning electron microscope image of the solid-state mercury ion electrode that is resistant to electrolyte interference. The magnification is 5000 times. It can be observed that the surface of the gold wire is covered with a layer of sensitive membrane material, and the surface also has nanoscale small holes with a large specific surface area. Figure 3 The EDS energy spectrum analysis result of the surface of the solid mercury ion electrode resistant to electrolyte interference is shown as Hg, Au and S, which can explain that the structure of the mercury ion selective electrode is gold wire-gold amalgam alloy-mercury sulfide sensitive membrane.

[0043] Example 2

[0044] This embodiment provides a method for preparing a solid mercury ion electrode resistant to electrolyte interference, and the specific steps are as follows:

[0045] (1) Cut a 40 mm long gold wire with a diameter of 0.2 mm and polish the surface of the gold wire with 5000-grit sandpaper. After polishing, ultrasonically clean the wire in 1M nitric acid solution, acetone, and ultrapure water for 10 minutes in sequence. After cleaning, dry the surface moisture with dust-free paper.

[0046] (2) immersing the portion of the gold wire used as the electrode probe in liquid mercury for 60 minutes to form a gold-mercury transition conductive layer on the surface of the gold wire;

[0047] (3) The gold wire with the gold-mercury amalgam transition conductive layer formed on the surface is immersed in a 0.01 M sodium selenide solution (pH = 12) for 60 minutes to form a mercury / mercury selenide sensitive film outside the gold-mercury amalgam transition conductive layer; the wire is washed with deionized water and dried to obtain a mercury ion electrode embryo.

[0048] (4) Cyclohexanone and tetrahydrofuran are mixed in a mass ratio of 1:3 to obtain a mixed solvent; 1 g of polyvinyl chloride (PVC) is dissolved in 9 g of the mixed solvent, and magnetic stirring is performed until it is completely dissolved to obtain a film-forming agent with a concentration of 10%. The film-forming agent solution is dipped into a mercury ion electrode embryo, and the probe end is placed upright at room temperature for 10 minutes. The film-forming agent solution is dipped into a mercury ion electrode embryo, and the probe end is placed upright at room temperature for 10 minutes. A nanoporous polyvinyl chloride film is formed on the surface of the mercury ion electrode embryo.

[0049] (6) placing the mercury ion electrode embryo with the nanoporous polyvinyl chloride membrane in methanol for 5 minutes to remove the residual film-forming agent; and after drying, obtaining a solid mercury ion electrode resistant to electrolyte interference.

[0050] Example 3

[0051] This embodiment provides a method for using the solid-state mercury ion electrode resistant to electrolyte interference prepared in Embodiment 1, which is specifically as follows:

[0052] (1) Prepare the mercury ion concentration to be 10 -3 M, 10 -4 M, 10 -5 M, 10 -6 The standard solution is prepared using Dickson seawater.

[0053] Dickson seawater composition: total dissolved inorganic carbon (total carbonate) 2031.90±0.32μM, total alkalinity 2231.59±0.62μM, phosphate 0.25μM, silicate 1.6μM, nitrate 0.99μM.

[0054] (2) The solid mercury ion electrode was used as the working electrode and the Ag / Ag2S electrode was used as the reference electrode to test the above standard solutions. The test time of each standard solution was 60 seconds, and the potential difference between the working electrode and the reference electrode was measured. The potential difference was linearly related to the mercury ion concentration in the standard solution, and the calibration formula E = 35.18lg (Hg 2+ )+674.41.

[0055] like Figure 4 As shown in the figure, it can be seen that the mercury ion selective electrode responds quickly (<15s) in mercury ion solutions with various electrolytes and has good stability. Figure 5 As shown, the solid mercury ion electrode has different concentrations of Hg 2+ The Nernst linear response in the solution is good, with a slope of 35.18 mV / dec (the ideal Nernst slope value of divalent cations is 29.59 mV / dec), R 2 =0.9991.

[0056] (3) The solid mercury ion electrode was used as the working electrode and the Ag / Ag2S electrode was used as the reference electrode. 2+ The test was conducted with a standard solution of mercury element with a concentration of 1000ug / mL (0.005M). The standard solution of mercury element was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0057] The stable data value of the solid-state mercury ion electrode is determined by a change of less than 1mV within 1 minute. The solid-state mercury ion electrode measures Hg 2+ The voltage of the 0.005M standard solution sample when it is stable is 567.2mV. Substituting into the calibration formula E = 35.18lg (Hg 2 +)+647.41mV(R 2 =0.9991), we can get the Hg content in the measured solution 2+ The concentration is about 0.00525 M. Compared with the known concentration of 0.005 M, the measured difference of the electrode is 0.00025 M, and the relative error is 5%. This indicates that the solid-state mercury ion electrode resistant to electrolyte interference prepared by the present invention can perform online mercury ion detection with high sensitivity and high selectivity.

[0058] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A solid mercury ion electrode resistant to electrolyte interference, characterized in that: From the inside to the outside, there are gold wire as a substrate, a gold amalgam transition conductive layer, a mercury / mercury selenide sensitive film or a mercury / mercury sulfide sensitive film and a nano-microporous polyvinyl chloride film.

2. A method for preparing a solid mercury ion electrode resistant to electrolyte interference, characterized in that: The specific steps are as follows: S1: Using electroplating or immersion method, a gold amalgam transition conductive layer is formed at the position where the gold wire is used as an electrode probe; S2: immersing the gold wire with a gold-mercury amalgam transition conductive layer on the surface into a sodium selenide or sodium sulfide solution for reaction, forming a mercury / mercury selenide sensitive film or a mercury / mercury sulfide sensitive film outside the gold-mercury amalgam transition conductive layer, and obtaining a mercury ion electrode embryo; S3: vertically dipping the mercury ion electrode embryo obtained in step S2 into a film-forming agent, and standing it upright with the detection end facing upward, so that a nano-microporous polyvinyl chloride film is formed on the surface of the mercury ion electrode embryo; the solute in the film-forming agent is polyvinyl chloride, and the solvent is a mixture of tetrahydrofuran and cyclohexanone; S4: placing the mercury ion electrode embryo with nanoporous polyvinyl chloride membrane obtained in step S3 in an extracting solution to remove the residual film-forming agent; and obtaining a solid mercury ion electrode resistant to electrolyte interference after drying.

3. The method for preparing a solid mercury ion electrode according to claim 2, characterized in that: The electroplating method described in step S1 is as follows: using an electrochemical workstation, in a 0.01MHgSO4 solution containing 3.3% concentrated sulfuric acid, the working electrode is connected to a gold-plated wire, the counter electrode is connected to another gold wire, and the reference electrode is connected to an Ag / Ag2S electrode. The parameters are set as follows: step = 1, voltage -1.2V, sensitivity 10 -3 A / V, electroplating time 300 seconds, a gold amalgam transition conductive layer is formed on the surface of the gold-plated wire.

4. The method for preparing a solid mercury ion electrode according to claim 2, characterized in that: The immersion method in step S1 is to immerse the gold wire in liquid mercury for 30 to 60 minutes.

5. The method for preparing a solid mercury ion electrode according to claim 2, characterized in that: The concentration of the sodium selenide or sodium sulfide solution in step S2 is 0.05-0.1M.

6. The method for preparing a solid mercury ion electrode according to claim 2, characterized in that: The mass ratio of tetrahydrofuran to cyclohexanone in the film-forming agent in step S3 is 1:(2-3); the mass concentration of polyvinyl chloride in the film-forming agent is 5%-10%.

7. The method for preparing a solid mercury ion electrode according to claim 2, characterized in that: In step S3, after the mercury ion electrode embryo is dipped in the film-forming agent, it is placed upright with the detection end facing upward for 10 to 30 minutes.

8. The method for preparing a solid mercury ion electrode according to claim 2, characterized in that: The extractant in step S4 is methanol or ethanol. The mercury ion electrode embryo with nanoporous polyvinyl chloride membrane is placed in methanol or ethanol for 5 to 15 minutes to remove the residual film-forming agent.

9. A solid mercury ion electrode prepared by the method for preparing a solid mercury ion electrode according to any one of claims 2 to 8.

10. A method for using a solid mercury ion electrode resistant to electrolyte interference, characterized in that: The solid mercury ion electrode according to claim 1 or 9 is used as a working electrode, and the Ag / Ag2Se or Ag / Ag2S electrode is used as a reference electrode. The working electrode and the reference electrode are placed in a solution to be tested containing mercury ions, and the potential difference between the working electrode and the reference electrode is measured; The concentration of mercury ions in the solution to be tested is calculated using the calibration formula.

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