Electrochemical detection method for chloride ions in zinc electrolyte

Abstract

The invention relates to the technical field of electrochemical analysis, and discloses an electrochemical detection method for chloride ions in zinc electrolyte, which adopts a glassy carbon substrate-graphene-silver nanocluster-chloride ion imprinted polymer three-layer composite electrode. According to the invention, by constructing a graphene-silver nanocluster-chloride ion imprinted polymer three-layer composite electrode interface, the electrode function is reconstructed from three dimensions of ion recognition, spatial isolation and electron transfer; the problems of sensitivity attenuation and selectivity deterioration caused by synergistic interference of high-concentration Zn < 2 + > and SO4 < 2-> in a zinc electrolyte system in a traditional voltammetry method are fundamentally solved. According to the method, complex sample pretreatment is not needed, expensive instruments and equipment are not needed, in-situ, real-time and high-precision detection of the chloride ions can be achieved on an industrial site, and a key technical support is provided for intelligent control and energy efficiency optimization of a zinc electrolysis process.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical analysis technology and relates to an electrochemical detection method for chloride ions in zinc electrolyte. Background Technology

[0002] As zinc electrolysis systems continue to evolve towards higher current densities and lower impurity tolerance, the inherent physicochemical limitations of traditional voltammetric detection architectures at the principle level are becoming increasingly apparent. The core contradiction lies in the irreconcilable conflict between the electrode interface reaction kinetics upon which the detection system relies and the extreme non-equilibrium environment created by the concentration gradient, adsorption competition, and side reaction pathways of the main components and impurity ions in the electrolyte. (Zn in zinc electrolyte...) 2+ The concentration is typically maintained in the range of 1-2 mol / L, which is more than three orders of magnitude higher than the target analyte chloride ions. Although the theoretical separation window of the standard redox potentials for the two is approximately 2.12 V, the high concentration of Zn... 2+ Strong adsorption occurs in the double-layer region of the electrode, irreversibly occupying the active sites on the electrode surface and forming a physical shielding layer. This causes chloride ions to encounter significant mass transfer resistance before reaching the electrode interface to complete electron transfer. Experimental data show that this effect can reduce the chloride ion oxidation peak current by 30%-50%, severely weakening the detection sensitivity.

[0003] Furthermore, SO4, which is ubiquitous in electrolytes 2- When using a silver-based working electrode, anions will react with Ag dissolved or pre-deposited on the electrode. + A precipitation reaction occurs, producing Ag₂SO₄. This product not only has low solubility, but its crystal structure also easily deposits in electrode micropores or rough surfaces, causing pore blockage and reduction of effective surface area, thus leading to response signal drift and deterioration in reproducibility. The synergistic effect of these two interference mechanisms results in a relative error of over 15% in the traditional voltammetry method in complex zinc electrolyte systems, far exceeding the ±5% accuracy threshold required for industrial process control. Furthermore, this error exhibits a non-linear amplification trend with batch fluctuations in the electrolyte, making it difficult to compensate for through subsequent data correction.

[0004] The fundamental difficulty in existing technologies does not stem from insufficient signal acquisition hardware or algorithm processing capabilities, but rather from the lack of ion-level recognition capabilities and anti-interference barriers at the electrode interface. Traditional bare electrodes or single-modified electrodes rely solely on potential resolution or differences in physical adsorption to achieve selectivity. When faced with coexisting ions of vastly different orders of magnitude and high chemical activity, their mechanism of action is easily suppressed by thermodynamically dominant species.

[0005] Without reconstructing the functional hierarchy of the electrode interface, simply optimizing scanning parameters or signal filtering strategies cannot overcome the physicochemical barriers constructed by ion competitive adsorption and side reaction precipitation. Therefore, the challenge lies in constructing a multi-level composite electrode interface that combines a highly conductive substrate, specific recognition sites, and ion sieving functions to achieve directional enrichment and spatial isolation of chloride ions while maintaining rapid electron transport kinetics, thereby fundamentally avoiding the high-concentration Zn contamination. 2+ With SO4 2- The synergistic interference effect has become a key challenge and a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To achieve the above-mentioned objectives, this invention provides an electrochemical detection method for chloride ions in zinc electrolyte. The core of this method lies in constructing a three-layer composite electrode interface structure possessing ion-level recognition capability, resistance to interference from high-concentration coexisting ions, and rapid electron transport kinetics. Based on this structure, a complete electrochemical detection process is established to achieve the detection of trace chloride ions (2.8 × 10⁻⁶) in the complex zinc electrolyte system. -3 Up to 1.4×10 -2 The system features highly selective, sensitive, and reproducible online detection of mol / L, with a relative detection error controlled within ±3% and a response time of less than 120 seconds, meeting the dual requirements of precision and real-time performance for industrial process control.

[0007] The working electrode used in the detection method of the present invention consists of a glassy carbon substrate, a graphene conductive layer, a silver nanocluster functional layer, and a chloride ion imprinted polymer selective recognition layer, which are constructed sequentially from bottom to top. The four-layer structure is constructed through a three-step process of physical deposition, chemical reduction, and electrochemical polymerization. The layers are stably bonded at the interface through covalent bonds or strong physical adsorption, ensuring that no interlayer peeling or structural collapse occurs during long-term service in a strongly acidic and high-ionic-strength electrolyte environment.

[0008] The glassy carbon substrate uses a 3.0 mm diameter disc-shaped glassy carbon electrode. Before use, its surface is polished to a mirror finish with a 0.05 μm alumina polishing slurry, and then ultrasonically cleaned for 5 minutes each in anhydrous ethanol and ultrapure water, followed by nitrogen drying before use. This substrate serves as the physical support and electron conduction terminal for the entire electrode structure, and its surface roughness Ra value is controlled below 5 nm to ensure uniform film formation and low interfacial resistance of subsequent modification layers.

[0009] The graphene conductive layer is deposited on the surface of a glassy carbon substrate via electrochemical reduction of graphene oxide. The specific process involves immersing a glassy carbon electrode in a 1.0 mg / mL aqueous dispersion of graphene oxide and performing reduction deposition at a constant potential of -1.2 V (vs. Ag / AgCl) for 300 seconds. After deposition, the electrode is removed, rinsed with ultrapure water to remove unbonded graphene oxide fragments, and dried with nitrogen. The resulting graphene layer has a thickness of 80-120 nm, consists of 3-5 stacked graphene sheets with a sheet spacing of 0.34 nm, a specific surface area of ​​850-950 m² / g, and an electrical conductivity of not less than 800 S / m. This layer provides high electron mobility channels, reduces the overall impedance of the electrode, and provides high specific surface area anchoring points for the upper silver nanoclusters. Simultaneously, its two-dimensional sheet structure can partially shield the electrochemical reaction from surface defects on the underlying glassy carbon.

[0010] The silver nanocluster functional layer was loaded onto the graphene layer surface using a constant current electrodeposition process. The deposition solution was a mixed aqueous solution containing 0.1 mol / L silver nitrate and 0.5 mol / L nitric acid, the deposition current density was 0.5 mA / cm², and the deposition time was 60 seconds. After deposition, the electrode was immersed in ultrapure water for 10 minutes to remove free silver ions and then dried with nitrogen gas. The resulting silver nanoclusters had an average particle size of 3.5 ± 0.8 nm, a particle size distribution standard deviation of less than 0.5 nm, and a unit area loading density of 2.5 × 10¹² particles / cm².

[0011] Ag on the surface of silver nanoclusters + It forms a coordinate bond with chloride ions, with a bond energy of approximately 185 kJ / mol and a coordination number of 2. The coordination configuration is a linear [Ag-Cl-Ag] bridge structure. This structure forms localized high-affinity adsorption sites on the electrode surface, increasing the local concentration of chloride ions at the electrode interface by 4-6 times compared to the bulk solution, thereby overcoming the high concentration of Zn. 2+ This results in a mass transfer inhibition effect. The silver nanoclusters are chemically bonded to the graphene layer via Ag-OC bonds, with a bonding energy of 210 kJ / mol, ensuring that they do not detach in a strongly acidic electrolyte.

[0012] The chloride ion-imprinted polymer selective recognition layer was constructed in situ on the surface of the silver nanocluster layer via electrochemical polymerization. The polymerization precursor solution consisted of 0.1 mol / L pyrrole monomer, 0.05 mol / L sodium chloride template ions, and 0.1 mol / L lithium perchlorate supporting electrolyte, with a mixed solvent of acetonitrile and water (volume ratio 4:1). The polymerization process was carried out in a three-electrode system, with the working electrode being the modified silver nanocluster electrode, the counter electrode being a platinum wire, and the reference electrode being Ag / AgCl (3.5 mol / L KCl). The polymerization potential was +0.8 V (vs. Ag / AgCl), the polymerization time was 180 seconds, and the polymerization current density was maintained at 0.2 mA / cm².

[0013] After polymerization, the electrode was immersed in a 0.5 mol / L nitric acid solution and eluted at 60°C for 2 hours to remove most of the template chloride ions, forming a three-dimensional cavity structure with chloride ion shape and size matching. The resulting polymer layer has a thickness of 150-200 nm, consisting of a polypyrrole backbone and a cross-linked network. Its cavity size distribution peak is 0.32 nm, which highly matches the chloride ion hydration radius (0.33 nm). Positively charged quaternary ammonium groups (-N) are distributed at the pore entrance. + (CH3)3), with a surface charge density of +1.2 × 10⁻⁶. 15 charges / cm², capable of repelling negatively charged SO4. 2- Ions (hydrated radius 0.38 nm) simultaneously prevent Zn from being contained through size exclusion effect. 2+ Hydrated ions (hydration radius 0.43 nm) enter the pores. This layer achieves selective recognition and spatial isolation of chloride ions at the molecular scale, effectively blocking SO42-. 2- The precipitation reaction pathway with Ag+ is used to shield Zn. 2+ Physical occupation of the active sites on the electrode.

[0014] The specific implementation steps of the detection method described in this invention are as follows: The first step involves using the glassy carbon electrode modified with the aforementioned three-layer composite structure as the working electrode, which, together with the platinum wire counter electrode and the Ag / AgCl reference electrode, forms a three-electrode detection system, placed in the zinc electrolyte to be tested. The zinc electrolyte temperature is controlled at 35±2℃, the pH value is maintained at 4.5-5.0, and the Zn... 2+ The concentration is 1.5 mol / L, SO4 2- The concentration is 1.8 mol / L, and the chloride ion concentration is 2.8 × 10⁻⁶. -3 Up to 1.45×10 -2 A value within the range of mol / L.

[0015] The second step involves applying a pretreatment potential program to the working electrode: first, constant potential polarization at -0.2V (vs. Ag / AgCl) for 60 seconds to reduce any oxidizing impurities that may be adsorbed on the electrode surface; then, five cyclic voltammetric scans at a scan rate of 50mV / s are performed in the range of +0.1V to +0.9V to activate the imprinted channels and stabilize the electrode interface state; finally, the electrode is left to stand at +0.1V for 30 seconds to allow the electrode interface to reach an electrochemical steady state.

[0016] The third step involved performing linear scan voltammetry: the scan initiation potential was +0.1V, the termination potential was +0.9V, and the scan rate was 20mV / s. The oxidation current-potential curve was recorded. Under these scan conditions, chloride ions produced a characteristic oxidation peak at +0.52±0.03V, and the peak current value corresponded to the chloride ion concentration at 2.8×10⁻⁶ mV / s. -3 Up to 1.4×10 -2 The linear relationship exists within the mol / L range, and the linear regression equation is: The correlation coefficient R² = 0.9986, and the detection limit is 8.5 × 10⁻⁶. -4 mol / L (S / N=3).

[0017] The fourth step is data acquisition and quantitative analysis: The original current signal is sampled a second time using the differential pulse voltammetry method, with a pulse amplitude of 50mV, a pulse width of 50ms, and a sampling period of 200ms to suppress background capacitance current interference. The obtained peak current value is substituted into the above linear regression equation to directly calculate the chloride ion concentration.

[0018] After each test, the electrode was polarized at a constant potential of +0.8V for 120 seconds in 0.1 mol / L nitric acid solution to oxidize and remove residual chloride species on the electrode surface, restore the activity of the imprinted channels, and ensure the reproducibility of the next test. The relative standard deviation of 10 consecutive repeated tests was less than 2.1%.

[0019] Furthermore, the electrode structure described in this invention exhibits excellent long-term stability. Under continuous operation for 30 days with 5 tests per day, the peak potential drift of chloride ion oxidation is less than ±5mV, and the peak current decay rate is less than 8%, indicating that the three-layer composite structure possesses excellent structural stability and functional durability in strongly acidic and high-ionic-strength environments. After electrode failure, it can be regenerated by ultrasonic cleaning in 0.5mol / L nitric acid at 60°C for 30 minutes, followed by repeating the silver nanocluster deposition and imprinting polymerization steps. The performance recovery rate after regeneration is over 95%.

[0020] In a preferred embodiment of the present invention, the graphene conductive layer can be pre-treated with nitrogen before deposition to further enhance its interfacial bonding strength with silver nanoclusters. Specifically, a graphene oxide dispersion is mixed with ethylenediamine at a volume ratio of 1:0.1, stirred at 80°C for 4 hours, centrifuged, and then redispersed in water at a concentration adjusted to 1.0 mg / mL before electrochemical reduction deposition. The resulting nitrogen-doped graphene contains 4.2 at% nitrogen atoms, mainly in the form of pyridine nitrogen and graphitic nitrogen. Its bonding energy with silver nanoclusters is increased to 245 kJ / mol, enabling the silver nanoclusters to bond strongly within a 1.5 mol / L Zn atmosphere. 2+ After soaking in the solution for 72 hours, the shedding rate decreased from 12% when undoped to below 3%.

[0021] In another preferred embodiment of the present invention, the chloride ion-imprinted polymer layer may incorporate the crosslinking monomer N,N′-methylenebisacrylamide during electropolymerization, with a molar ratio of 1:20 to the pyrrole monomer, to enhance the mechanical strength and swelling stability of the polymer network. The resulting crosslinked imprinted polymer exhibits a swelling rate of less than 5% within the pH range of 4.5-5.0, and the pore structure shows no significant deformation after 1000 cycles of continuous electrochemical scanning.

[0022] In another preferred embodiment of the present invention, the detection method can be integrated into an online flow-through cell system to achieve continuous automatic detection. The flow-through cell has a volume of 5 mL, and the working electrode, counter electrode, and reference electrode are arranged in a concentric cylindrical structure. The electrolyte flow rate is controlled at 2.0 mL / min, and the detection cycle is once every 3 minutes. The system is equipped with an automatic cleaning module, which automatically injects 0.1 mol / L nitric acid solution to rinse the electrode surface for 60 seconds after each detection, followed by rinsing with ultrapure water for 30 seconds to ensure the cleanliness of the electrode interface. After 720 hours of continuous operation, the system exhibits a data drift of less than ±4%, meeting the requirements for long-term online monitoring in industrial settings.

[0023] In another preferred embodiment of the present invention, the working electrode undergoes a regeneration procedure after every 50 uses: ultrasonic cleaning at 60°C for 30 minutes in 0.5 mol / L nitric acid, followed by sequential redeposition of the graphene conductive layer, the silver nanocluster functional layer, and the chloride ion-imprinted polymer selective recognition layer. The performance recovery rate after regeneration is ≥95%. A new standard curve is established using a five-point calibration method with a concentration gradient of 2.8 × 10⁻⁶. -3 5.6×10 -3 8.5×10 -3 1.1×10 -2 1.4×10 -2 mol / L.

[0024] As another preferred embodiment of the present invention, the detection method is adaptable to different working conditions: When Zn 2+ When the concentration deviates from 1.5 mol / L, the peak current is multiplied by a correction factor. , For actual Zn 2+ concentration; When the temperature deviates from 35°C, the peak current is multiplied by the temperature correction factor. , The actual temperature (°C) is used to control signal drift within ±1.5%; SO4 2- No correction is required for concentrations in the range of 1.5-2.5 mol / L.

[0025] Compared with the prior art, the beneficial effects of the present invention are: 1. The sensitivity and selectivity of the detection method described in this invention stem from the synergistic mechanism of the three-layer composite structure. The graphene layer provides a highly conductive pathway, reducing charge transfer resistance and increasing the electron transfer rate from chloride ion oxidation sites to the glassy carbon substrate to more than 15 times that of the bare electrode. Silver nanoclusters construct locally high-concentration chloride ion microregions at the electrode interface through specific coordination, overcoming mass transfer limitations. The imprinted polymer layer achieves selective recognition of chloride ions and spatial isolation of coexisting ions at the ionic scale through size-matched pores and electrostatic repulsion. The synergistic effect of these three elements enables the electrode to maintain rapid electron transfer dynamics while possessing ion-level recognition capabilities, thus breaking through the detection bottleneck of traditional voltammetry in high-concentration coexisting ion systems at the principle level.

[0026] 2. The engineering implementation of the detection method described in this invention relies on a standardized set of electrode preparation and detection operating procedures. During electrode preparation, all solutions are prepared using ultrapure water, and all glassware is soaked in aqua regia for 24 hours and rinsed with ultrapure water before use. Electrochemical deposition and polymerization processes are carried out under isothermal and oxygen-free conditions to avoid interference from oxidation side reactions.

[0027] 3. The detection method described in this invention is adaptable to various electrochemical workstations, and its core parameter settings are universally applicable. The scanning potential range is fixed at +0.1V to +0.9V, the scanning rate is fixed at 20mV / s, the preprocessing procedure is fixed at -0.2V polarization for 60 seconds + 5 cycles of CV scanning + 30 seconds of rest, and data acquisition uses differential pulse mode with pulse parameters fixed at amplitude 50mV, width 50ms, and period 200ms. This standardized parameter setting ensures that data obtained from different devices and by different operators are highly comparable and traceable. Detailed Implementation

[0028] The technical solution of this invention is a three-layer composite modified working electrode, which, from bottom to top, consists of a glassy carbon substrate, a graphene conductive layer, a silver nanocluster functional layer, and a chloride ion imprinted polymer selective recognition layer. This electrode structure is constructed sequentially through a three-step process of physical deposition, chemical reduction, and electrochemical polymerization. The layers are stably bonded at the interface through covalent bonds or strong physical adsorption, ensuring that no interlayer delamination or structural collapse occurs during long-term operation in strongly acidic, high-ionic-strength electrolyte environments. Based on this electrode, this invention establishes a complete electrochemical detection process, achieving highly selective, highly sensitive, and highly reproducible online detection of trace chloride ions in zinc electrolytes, with a relative detection error controlled within ±3% and a response time of less than 120 seconds.

[0029] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0030] Example 1 (Basic Scheme): Electrode Structure: Glassy carbon substrate (diameter 3.0 mm, Ra ≤ 5 nm) + undoped graphene conductive layer (thickness 80-120 nm, conductivity ≥ 800 S / m) + silver nanocluster functional layer (particle size 3.5 ± 0.8 nm, loading density 2.5 × 10¹² particles / cm²) + uncrosslinked chloride ion imprinted polymer layer (peak pore size 0.32 nm, surface charge density + 1.2 × 10¹² particles / cm²) 15 charges / cm²); Detection conditions: Zn in zinc electrolyte 2+ Concentration 1.5 mol / L, SO4 2- The concentration was 1.8 mol / L, pH 4.5-5.0, and temperature was 35℃. A three-electrode system was used, and the pretreatment potential program and linear scan voltammetric parameters were set according to the patent standard. Core process: Graphene is deposited by electrochemical reduction of graphene oxide, silver nanoclusters are loaded by constant current electrodeposition, and imprinted polymers are constructed by electrochemical polymerization without the introduction of nitrogen doping and crosslinking monomers.

[0031] Example 2 (Graphene Nitrogen Doping Optimization): Electrode Structure: Same as Example 1, except that the graphene conductive layer is treated with nitrogen doping (graphene oxide and ethylenediamine are mixed at a volume ratio of 1:0.1, reacted at 80°C for 4 hours, and the nitrogen atom content is 4.2 at%, mainly pyridine nitrogen and graphitic nitrogen). Detection conditions: exactly the same as in Example 1; Core process: Adding a nitrogen doping step before graphene deposition increases the interfacial binding energy with silver nanoclusters to 245 kJ / mol.

[0032] Example 3 (Optimization of crosslinking of imprinted polymer): Electrode structure: consistent with Example 1, except that the crosslinking monomer N,N′-methylenebisacrylamide (molar ratio of 1:20 with pyrrole monomer) is introduced into the chloride ion imprinted polymer layer. Detection conditions: exactly the same as in Example 1; Core process: Adding crosslinking monomers during electrochemical polymerization enhances the mechanical strength and swelling stability of the polymer network.

[0033] Example 4 (In-line flow cell integration): Electrode structure: Same as Example 1; Detection conditions: Integrated into an online flow cell system (flow cell volume 5 mL, electrodes arranged in concentric cylinders, electrolyte flow rate 2.0 mL / min, detection cycle 3 minutes / time, rinsed with 0.1 mol / L nitric acid for 60 seconds and ultrapure water for 30 seconds after each detection), electrolyte parameters are the same as in Example 1; Core technology: Add an online automatic cleaning and continuous detection module to the basic solution.

[0034] Example 5 (Zn) 2+ Concentration deviation correction): Electrode structure: Same as in Example 1; Detection conditions: Zn in zinc electrolyte 2+ Concentration 2.0 mol / L (deviation from standard 1.5 mol / L), other parameters (SO4) 2- The concentration (1.8 mol / L, pH 4.5-5.0, temperature 35℃) is the same as in Example 1, and the peak current is multiplied by the correction factor k = 1.0 + 0.12 × (2.0 - 1.5) = 1.06; Core technology: using Zn 2+ The concentration deviates from the correction formula, but everything else is the same as in Example 1. Example 6 (Temperature Deviation Correction): Electrode structure: Same as Example 1; Testing conditions: Zinc electrolyte temperature 40℃ (deviating from the standard of 35℃), other parameters (Zn) 2+ Concentration 1.5 mol / L, SO4 2- (Concentration 1.8 mol / L, pH 4.5-5.0) Same as Example 1, peak current multiplied by temperature correction factor.

[0035] Core process: The temperature deviation correction formula is adopted, and the rest is the same as in Example 1.

[0036] Comparative Example 1 (Traditional bare glassy carbon electrode scheme): Electrode structure: Only the glassy carbon substrate in Example 1 is used (without graphene, silver nanoclusters and imprinted polymer layer), and the surface treatment is the same as in Example 1; Detection conditions: exactly the same as in Example 1, using the traditional linear scanning voltammetry method; Core process: No functional layer modification is used; detection is achieved through chloride ion oxidation reaction on the bare electrode surface.

[0037] Comparative Example 2 (Dual-layer modified electrode scheme): Electrode structure: glassy carbon substrate + graphene conductive layer (undoped) + silver nanocluster functional layer (consistent with Example 1), lacking chloride ion imprinted polymer selective recognition layer; Detection conditions: exactly the same as in Example 1; Core technology: Only a double conductive and functional layer is constructed, without an ion recognition and spatial isolation layer.

[0038] Performance data comparison table:

[0039] Example 1, as a basic solution, outperforms traditional solutions and solutions lacking a critical layer in all aspects: Detection limit as low as Compared to bare glassy carbon electrode (Comparative Example 1), The improvement is approximately 18 times, compared to the bilayer modified electrode (Comparative Example 2). The concentration of chloride ions in zinc electrolyte can be increased by approximately 4 times, achieving a reduction of chloride ions ( ) by approximately 4 times. to Accurate detection; The relative error is controlled at ±2.8%, which is much lower than the ±18.5% of the traditional solution and ±9.2% of the double-layer modified electrode, meeting the accuracy requirement of ±5% for industrial control; The response time is 110 seconds, which is 54% shorter than the traditional solution (240 seconds) and 39% shorter than the double-layer modified electrode (180 seconds), enabling real-time detection; Selectivity coefficient (for) The concentration reached 850, effectively inhibiting high concentrations. Interference, solving the signal drift problem caused by Ag2SO4 precipitation in traditional methods.

[0040] Nitrogen doping of graphene (Example 2): By enhancing the interfacial bonding energy between graphene and silver nanoclusters through nitrogen doping, the 72-hour detachment rate of silver nanoclusters decreased from 12.0% (Example 1) to 3.0%, while simultaneously reducing the charge transfer resistance, shortening the response time to 105 seconds, and reducing the relative error to ±2.5%, with the detection limit being [missing value]. It is suitable for long-term continuous detection scenarios.

[0041] Imprinted polymer crosslinking (Example 3): Crosslinking monomers improve polymer stability, detection limit is Selectivity coefficient (for) The peak current decay rate decreased to 6.8%, maintaining a value of 790, thus resolving the issue. and Precipitation interference, suitable for high Electrolyte concentration detection.

[0042] Online circulation pool integration (Example 4): Detection limit is With a relative error of ±2.9%, automated continuous detection is achieved under this premise, meeting the needs of in-situ monitoring in industrial sites.

[0043] Correction for deviations from standard operating conditions (Examples 5 and 6): For cases where the Zn²+ concentration (2.0 mol / L) and temperature (40°C) deviate from the standard operating conditions, a correction factor is used to stabilize the relative error within ±2.6% to ±2.7%, thereby improving the adaptability of the method to operating conditions.

[0044] Comparing Example 1 and Comparative Example 2 (without the imprinted polymer layer), it can be seen that the lack of the ion recognition and spatial isolation functions of the imprinted polymer reduces the detection limit from... Deterioration to The relative error increased from ±2.8% to ±9.2%, and the selectivity coefficient decreased from 850 to 300, proving that the imprinted polymer layer is the core solution to the interference of Zn²⁺ adsorption shielding and SO₄²⁻ precipitation.

[0045] By combining the differences between Example 1 and Comparative Example 1 (bare electrode), it is further explained that the synergistic effect of the graphene conductive layer (reducing impedance and improving electron transfer) and the silver nanocluster functional layer (constructing a micro-region with high chloride ion concentration) is the basis for achieving high-sensitivity detection.

[0046] This invention solves the problems of low sensitivity, poor selectivity, and weak anti-interference ability of traditional voltammetry in zinc electrolyte by using a "three-layer composite electrode + standardized detection process + optimized operating conditions". It eliminates the need for complex sample pretreatment and enables in-situ, real-time, and high-precision detection. It provides key data support for the intelligent control of zinc electrolysis process (such as adjusting the amount of dechlorinating agent and optimizing electrolysis parameters), which helps to reduce the risk of corrosion in the electrolytic cell, improve the purity of cathode zinc, and reduce energy consumption.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrochemical detection method for chloride ions in zinc electrolyte, characterized in that, Includes the following steps: S1: Construct a three-layer composite working electrode, which from bottom to top includes a glassy carbon substrate, a graphene conductive layer, a silver nanocluster functional layer, and a chloride ion imprinted polymer selective recognition layer. S2: The working electrode, together with the platinum wire counter electrode and the Ag / AgCl reference electrode, forms a three-electrode system, which is then immersed in the zinc electrolyte to be tested. The zinc electrolyte contains Zn. 2+ Concentration of 1.0-2.0 mol / L, SO4 2- The concentration is 1.5-2.5 mol / L, the pH value is 4.5-5.0, and the temperature is 30-40℃; S3: Apply a pretreatment procedure to the working electrode: first, polarize at a constant potential of -0.2V for 60 seconds, then perform a cyclic voltammetric scan at a scan rate of 50mV / s for 5 cycles in the range of +0.1V to +0.9V, and finally rest at +0.1V for 30 seconds; S4: Perform linear scan voltammetry detection with a scan potential range of +0.1V to +0.9V and a scan rate of 20mV / s. Record the oxidation current-potential curve and identify the characteristic oxidation peak of chloride ions at +0.52±0.03V. S5: The original current signal is sampled a second time using the differential pulse voltammetry method. The pulse amplitude is 50mV, the pulse width is 50ms, and the sampling period is 200ms. The background capacitance current interference is canceled by the second sampling, and the peak current value is extracted. S6: Substitute the peak current value into the preset linear regression equation: Calculate chloride ion concentration The detection range of chloride ions using this method is 2.8 × 10⁻⁶. -3 Up to 1.4×10 -2 The detection limit is 8.5 × 10⁻⁶. -4 mol / L.

2. The electrochemical detection method according to claim 1, characterized in that, The glassy carbon substrate is a 3.0 mm diameter disc-shaped electrode. The surface is polished to a mirror finish with 0.05 μm alumina polishing slurry, and then ultrasonically cleaned for 5 minutes each with anhydrous ethanol and ultrapure water, and dried with nitrogen before use.

3. The electrochemical detection method according to claim 1, characterized in that, The graphene conductive layer is deposited on the surface of a glassy carbon substrate by electrochemical reduction of graphene oxide: the glassy carbon electrode is immersed in a 1.0 mg / mL aqueous dispersion of graphene oxide and reduced and deposited for 300 seconds at a constant potential of -1.2 V. The resulting graphene layer has a thickness of 80-120 nm and is composed of 3-5 stacked graphene sheets.

4. The electrochemical detection method according to claim 3, characterized in that, Graphene oxide was treated with nitrogen doping before deposition: the graphene oxide dispersion was mixed with ethylenediamine at a volume ratio of 1:0.1, stirred at 80°C for 4 hours, and then redispersed to 1.0 mg / mL after centrifugation. The nitrogen content in the obtained nitrogen-doped graphene was 4.2 at.

5. The electrochemical detection method according to claim 1, characterized in that, The silver nanocluster functional layer was loaded onto the surface of the graphene conductive layer by constant current electrodeposition: the deposition solution was a mixed aqueous solution containing 0.1 mol / L silver nitrate and 0.5 mol / L nitric acid, the deposition current density was 0.5 mA / cm², and the deposition time was 60 seconds.

6. The electrochemical detection method according to claim 1, characterized in that, A chloride ion-imprinted polymer selective recognition layer was constructed in situ on the surface of a silver nanocluster functional layer via electrochemical polymerization. The polymerization solution contained 0.1 mol / L pyrrole monomer, 0.05 mol / L sodium chloride template ions, and 0.1 mol / L lithium perchlorate supporting electrolyte. The solvent was acetonitrile:water = 4:1 (v / v). The polymerization potential was +0.8 V, and the polymerization time was 180 seconds. After polymerization, the mixture was eluted in 0.5 mol / L nitric acid at 60 °C for 2 hours with shaking to form a three-dimensional cavity structure with a peak pore size of 0.32 nm. Quaternary ammonium groups were distributed at the pore inlets.

7. The electrochemical detection method according to claim 6, characterized in that, The crosslinking monomer N,N′-methylenebisacrylamide is introduced into the polymerization solution, with a molar ratio of 1:20 to the pyrrole monomer.

8. The electrochemical detection method according to claim 1, characterized in that, The detection method is integrated into an online flow cell system: the flow cell volume is 5 mL, the working electrode, counter electrode, and reference electrode are arranged in concentric cylinders, the electrolyte flow rate is 2.0 mL / min, the detection cycle is 3 minutes / time, and after each detection, 0.1 mol / L nitric acid is automatically injected for 60 seconds to rinse, followed by ultrapure water for 30 seconds to rinse.

9. The electrochemical detection method according to claim 1, characterized in that, The working electrode undergoes a regeneration procedure after every 50 uses: ultrasonic cleaning at 60°C for 30 minutes in 0.5 mol / L nitric acid, followed by sequential redeposition of the graphene conductive layer, silver nanocluster functional layer, and chloride ion-imprinted polymer selective recognition layer. The performance recovery rate after regeneration is ≥95%. A new standard curve is established using a five-point calibration method with a concentration gradient of 2.8 × 10⁻⁶. -3 5.6×10 -3 8.5×10 -3 1.1×10 -2 1.4×10 - 2 mol / L.

10. The electrochemical detection method according to claim 1, characterized in that, The testing method is adaptable to different working conditions: When Zn 2+ When the concentration deviates from 1.5 mol / L, the peak current is multiplied by a correction factor. , For actual Zn 2+ concentration; When the temperature deviates from 35°C, the peak current is multiplied by the temperature correction factor. , The actual temperature (°C) is used to control signal drift within ±1.5%; SO4 2- No correction is required for concentrations in the range of 1.5-2.5 mol / L.

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