Method for simultaneously measuring fluorine and chlorine content in lead concentrate by ion selective electrode method

Abstract

The invention relates to a method for simultaneously detecting fluorine and chlorine contents in lead concentrate by an ion selective electrode method, and belongs to the technical field of new material detection, and the method specifically comprises the following steps: (1) preparing a sample into a to-be-detected solution; (2) preparing a fluorine ion electrode standard solution and a chloride ion electrode standard solution; (3) calibrating a fluorine ion standard solution and a chloride ion standard solution; and (4) sample determination and data processing. According to the combined measurement method provided by the invention, through a layered coverage method, optimization of the ratio of potassium hydroxide to potassium nitrate and gradient temperature rise, on the premise of ensuring data quality, an accurate result is conveniently obtained; compared with a fluorine or chlorine testing method commonly used in the market, the method is short in time consumption, simple in equipment and accurate in data; in addition, the combined detection method provided by the invention breaks through the pH limit of traditional single ion detection, and provides a reliable solution for synchronous determination of fluorine and chlorine in a complex matrix sample.

Description

Technical Field

[0001] This invention belongs to the field of new material detection technology, specifically, it relates to a method for the determination of fluoride and chlorine content in lead concentrate using the ion-selective electrode method. Background Technology

[0002] Chloride ions in lead concentrate are highly corrosive, affecting equipment, product quality, and environmental protection. Smelting units generally require their content to be ≤1.0%. Currently, national standards lack methods for detecting chloride ions in lead concentrate. Commonly used analytical methods for chloride ions include turbidimetry, molar method, ion chromatography, potentiometric titration, and silver nitrate titration. However, turbidimetry has disadvantages such as a narrow measurement range and interference caused by color blocking light. Molar method is a classic method, but it has large errors in the low concentration range, color discrimination has certain misconceptions, and the endpoint is not obvious. Ion chromatography is too expensive and has a long process, which is not conducive to production. Potentiometric titration suffers from severe interference, is difficult to adjust the instrument, and is complex to operate. The main advantages of silver nitrate titration are its mature method, easy determination of the titration endpoint, and low experimental cost, but it is not suitable for continuous testing of multiple samples. The detection accuracy of potentiometric titration is limited by the accuracy of the probe, and there are problems such as signal drift and poor stability of detection results. Ion electrode selection is a direct, non-destructive analytical method that is unaffected by the color, turbidity, suspended matter, or viscosity of the sample solution. It is simple to operate, has a short procedure time, low cost, and few interferences, making it the optimal analytical method.

[0003] Common methods for determining fluoride ion content include fluoride ion selective electrode method, spectrophotometry, ion chromatography, and volumetric analysis. Spectrophotometry has a narrow detection range, ion chromatography requires transparent samples free of impurities, and the ion selective electrode method has advantages such as good selectivity, simple operation, sensitivity, and a wide detection range.

[0004] Lead concentrate contains a certain amount of fluorides and chlorides. During production, fluorides and chlorides can significantly impact systems, equipment, and the environment. Therefore, accurately determining the content of chlorides and fluorides is crucial for lead concentrate production. Ion electrode methods are suitable for determining both fluoride and chloride ions. Furthermore, employing combined fluoride and chloride ion electrode techniques, which streamline the detection process, improves detection efficiency. While ion chromatography can achieve combined fluoride and chloride determination, it is expensive and complex, making it unsuitable for production. In contrast, ion electrode methods offer high selectivity, sensitivity, and a wide range, addressing current limitations in this technology and meeting production control requirements.

[0005] Therefore, providing a method for the joint determination of fluoride and chlorine content in lead concentrate using ion-selective electrode method, thereby reducing operational steps and merging positions, is of great practical significance in improving efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a method for the joint determination of fluoride and chloride content in lead concentrate using ion-selective electrode method, which solves the problem of difficulty in the joint determination of fluoride and chloride ions in existing new material detection technologies.

[0007] The objective of this application can be achieved through the following technical solutions:

[0008] The first aspect of this application provides a method for determining the fluoride and chloride content in lead concentrate using an ion-selective electrode method, the method specifically comprising the following steps:

[0009] (1) Prepare the sample into a test solution;

[0010] (2) Prepare standard solutions for fluoride ion electrodes and chloride ion electrodes;

[0011] (3) Standardization of fluoride ion standard solution and chloride ion standard solution;

[0012] (4) Sample determination and data processing.

[0013] As a preferred technical solution of this application, step (1) specifically includes the following steps:

[0014] (101) Place the sample in a nickel crucible pre-coated with flux A, then cover it with oxidant and flux B in sequence. Heat the covered nickel crucible at a uniform rate and keep it at that temperature. After the heat preservation is completed, remove the nickel crucible and cool it once. Then immerse it in hot water, boil it and keep it for 5 minutes to obtain the melt. Cool it a second time, make the melt to a fixed volume, filter it, and obtain the filtrate.

[0015] (102) Transfer the filtrate to the volumetric flask, add methyl red ethanol indicator, then add nitric acid solution dropwise, add TISAB solution and dilute, shake well to obtain the test solution, put 1 magnetic stir bar into the test solution and set aside.

[0016] As a preferred technical solution of this application, the mass ratio of the sample, flux A, oxidant and flux B in step (101) is 0.4997-0.5003:1.55-1.6:1.9-2.1:3.0-3.1.

[0017] Furthermore, the oxidant includes potassium nitrate, and both flux A and flux B are potassium hydroxide.

[0018] As a preferred technical solution of this application, the sample in step (101) includes lead concentrate, zinc concentrate, and water-quenched slag; the covering method is not specifically limited, as long as it is ensured that each covering can completely cover the covered object to achieve the purpose of this application; the uniform heating and holding is specifically to uniformly heat to 650°C at a rate of 10°C / min and then hold for 14.5-15.5min; the first cooling is to cool to below 200°C; the second cooling is to cool to room temperature; the volume adjustment of the melt is to transfer the melt to a 100mL volumetric flask and adjust the volume with ultrapure water.

[0019] Preferably, the sample comprises lead concentrate.

[0020] As a preferred technical solution of this application, the volumetric flask in step (102) is a 50mL volumetric flask, the amount of methyl red ethanol indicator added is 1 drop, the amount of nitric acid solution added is until the pH of the filtrate is ≈6.0, the volume of the filtrate transferred is 20mL, the amount of TISAB solution added is 10mL, and the dilution is to dilute with ultrapure water to 50mL.

[0021] As a preferred technical solution of this application, the methyl red ethanol indicator in step (102) is 0.1% methyl red ethanol indicator; the molar concentration of the nitric acid solution is 5%.

[0022] As a preferred technical solution of this application, the fluoride ion electrode standard solution and the chloride ion electrode standard solution in step (2) are both three-gradient standard solutions, wherein:

[0023] The standard solution for the fluoride ion electrode is: 1×10 -3 mol / L (pF3), 1×10 -4 mol / L (pF4), 1×10 -5 mol / L (pF5);

[0024] The standard solution for the chloride ion electrode is: 1×10 -2 mol / L (pCl 2), 1×10 -3 mol / L (pCl 3), 1×10 - 4 mol / L (pCl 4);

[0025] Furthermore, the 1×10 -3 The preparation method of mol / L (pF3) is as follows: Take 5 mL of 0.01 mol / L fluoride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0026] The 1×10-4 The preparation method of mol / L (pF4) is as follows: Take 5 mL of 0.001 mol / L fluoride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0027] The 1×10 -5 The preparation method of mol / L (pF5) is as follows: Take 0.5 mL from 0.001 mol / L fluoride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0028] The 1×10 -2 The preparation method of mol / L (pCl 2) is as follows: Take 5 mL of 0.1 mol / L chloride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0029] The 1×10 -3 The preparation method of mol / L (pCl 3) is as follows: Take 5 mL of 0.01 mol / L chloride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0030] The 1×10 -4 The preparation method of mol / L (pCl 4) is as follows: Take 5 mL of 0.001 mol / L chloride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0031] As a preferred technical solution of this application, step (3) specifically includes the following steps:

[0032] Fluoride ion standard solution calibration: Transfer 50 mL of pF5 into a plastic cup, insert the fluoride ion electrode, single salt bridge reference electrode and temperature electrode into pF5 together, turn on the electromagnetic stirring, start the calibration, wait for the instrument to lock automatically, repeat the above steps to calibrate pF4 and pF3 in turn, and save after completing the last calibration;

[0033] Chloride ion standard solution calibration: Transfer 50 mL of pCl4 into a beaker, insert the chloride ion reference electrode, the double salt bridge reference electrode, and the temperature electrode into the pCl4, turn on the electromagnetic stirring, start the calibration, wait for the instrument to automatically lock, repeat the above steps to calibrate pCl3 and pCl2 in sequence, and save after completing the last calibration.

[0034] As a preferred technical solution of this application, step (4) specifically includes the following steps:

[0035] (401) Install the chloride ion electrode, rinse the electrode after calibration with distilled water using the chloride ion electrode standard solution, insert the chloride ion electrode, the dual salt bridge reference electrode, and the temperature electrode into the test solution, turn on the stirring, start the measurement, and wait for the instrument to automatically lock and display the chloride ion concentration in the test solution.

[0036] (402) Install the fluoride ion electrode, rinse the electrode after calibration with distilled water using the fluoride ion electrode standard solution, insert the fluoride ion electrode, the double salt bridge reference electrode, and the temperature electrode into the test solution, turn on the stirring, start the measurement, and wait for the instrument to automatically lock and display the fluoride ion concentration in the test solution.

[0037] (403) Calculate the fluoride and chloride ion contents according to the following formula:

[0038]

[0039] In the above formula:

[0040] F(%): Represents the percentage content of F ions in the sample;

[0041] Cl (%): Represents the percentage content of Cl ions in the sample;

[0042] c: Represents the measured concentration value (g / L).

[0043] The beneficial effects of this invention are:

[0044] (1) The joint test method provided in this application obtains accurate results relatively easily while ensuring data quality by using the layered coverage method, optimizing the ratio of potassium hydroxide to potassium nitrate, and gradient heating (i.e., uniformly heating to 650℃). Moreover, compared with the commonly used fluorine or chlorine test methods on the market, this application takes less time, uses simpler equipment, and provides more accurate data.

[0045] (2) The combined detection method provided in this application breaks through the pH limitation of traditional single ion detection and provides a reliable solution for the simultaneous determination of fluoride and chlorine in complex matrix samples.

[0046] (3) In this application, the reference electrode for the determination of F ions is a single salt bridge electrode (filled with saturated NaCl solution). However, for the determination of Cl ions, a small amount of NaCl will permeate, causing contamination of the solution and causing the results to deviate. Therefore, a double salt bridge electrode is selected, with sodium chloride added to the inner electrode and sodium nitrate added to the outer electrode, which can avoid this problem. In addition, chlorine is measured first and then fluorine is measured in the process, which can avoid contamination of the solution.

[0047] (4) The spiked recovery rate under the method of this application can meet the accuracy requirements of raw material analysis; and the RSD value is between 2-5%, which is not much different from the accepted value. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0049] The preparation method of TI SAB (total ionic strength adjusting buffer) solution used in this application is as follows: Accurately weigh 735.0 g of analytical grade sodium citrate and 250.0 g of analytical grade potassium nitrate, dissolve them in ultrapure water, and transfer them to a 2500 mL volumetric flask and make up to volume. This buffer system contains citrate ions that can complex with metal ion interferences, and potassium nitrate is used to maintain a constant ionic strength. After preparation, it should be stored in a polyethylene reagent bottle away from light.

[0050] Preparation method of ion standard solution (0.01mol / L): After constant weight of reference grade sodium fluoride in a vacuum drying oven at 120℃ for 2h, accurately weigh 0.4199g (accurate to 0.0001g), dissolve it in ultrapure water and make up to 1L brown volumetric flask, and store it in a polytetrafluoroethylene container at 4℃.

[0051] Preparation method of fluoride ion standard solution (0.001 mol / L): Take 100.00 mL of 0.01 mol / L fluoride ion standard solution into a 1 L volumetric flask and dilute to volume using the stepwise dilution method;

[0052] Preparation method of chloride ion standard solution (0.1 mol / L): Place the standard sodium chloride in a muffle furnace and ignite at 550℃ until constant weight. Accurately weigh 5.844 g, dissolve it, and then dilute with deionized water to 1 L.

[0053] Chloride ion standard solution (0.01 mol / L): Place the standard sodium chloride in a muffle furnace and ignite at 550°C until constant weight. Accurately weigh 0.5844 g, dissolve it, and then dilute to 1 L with deionized water.

[0054] Chloride ion standard solution (0.001 mol / L): Using the stepwise dilution method, take 100.00 mL of 0.01 mol / L chloride ion standard solution and dilute to volume in a 1 L volumetric flask;

[0055] The above will not be repeated hereafter.

[0056] Example 1

[0057] A method for determining the fluoride and chloride content in lead concentrate using an ion-selective electrode method, the method specifically comprising the following steps:

[0058] (1) Prepare the sample into a test solution, specifically including the following steps:

[0059] (101) Place 0.5000g of sample in a nickel crucible pre-coated with 1.5g of flux A, then cover with 2.0g of oxidant and 3.0g of flux B in sequence. Heat the covered nickel crucible to 650℃ at a rate of 10℃ / min and hold for 15min. After holding, remove the nickel crucible and cool it to below 200℃. Then immerse it in hot water, boil and hold for 5min to obtain a melt. After cooling the melt to room temperature, transfer it to a 100mL volumetric flask and dilute to volume with ultrapure water. Filter to obtain the filtrate.

[0060] The sample is lead concentrate; the oxidant is potassium nitrate, and both flux A and flux B are potassium hydroxide; the covering method is not specifically limited, as long as it ensures that each covering completely wraps the object being covered.

[0061] (102) Transfer the filtrate to a 50 mL volumetric flask, add 1 drop of methyl red ethanol indicator, and then add 5% nitric acid solution dropwise until the pH of the filtrate is approximately 6.0. Add TI SAB (total ionic strength adjusting buffer) solution and dilute with ultrapure water to 50 mL. Shake well to obtain the test solution. Place one magnetic stir bar in the test solution for later use.

[0062] (2) Prepare fluoride ion electrode standard solutions and chloride ion electrode standard solutions, wherein both fluoride ion electrode standard solutions and chloride ion electrode standard solutions are three-gradient standard solutions, wherein:

[0063] The standard solution for the fluoride ion electrode is: 1×10 -3 mol / L (pF3), 1×10 -4 mol / L (pF4), 1×10 -5 mol / L (pF5);

[0064] The standard solution for the chloride ion electrode is: 1×10 -2 mol / L (pCl 2), 1×10 -3 mol / L (pCl 3), 1×10- 4 mol / L (pCl 4);

[0065] The 1×10 -3 The preparation method of mol / L (pF3) is as follows: Take 5 mL of 0.01 mol / L fluoride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0066] The 1×10 -4 The preparation method of mol / L (pF4) is as follows: Take 5 mL of 0.001 mol / L fluoride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0067] The 1×10 -5 The preparation method of mol / L (pF5) is as follows: Take 0.5 mL from 0.001 mol / L fluoride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0068] The 1×10 -2 The preparation method of mol / L (pCl 2) is as follows: Take 5 mL of 0.1 mol / L chloride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0069] The 1×10 -3 The preparation method of mol / L (pCl 3) is as follows: Take 5 mL of 0.01 mol / L chloride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0070] The 1×10 -4 The preparation method of mol / L (pCl 4) is as follows: Take 5 mL of 0.001 mol / L chloride ion standard solution into a 50 mL volumetric flask, add 1 drop of 0.1% methyl red ethanol indicator, 1 drop of 5% dilute nitric acid, 10 mL of TISAB solution, and dilute to volume with deionized water.

[0071] (3) The standardization of fluoride ion standard solution and chloride ion standard solution includes the following steps:

[0072] Fluoride ion standard solution calibration: Transfer 50 mL of pF5 into a plastic cup, insert the fluoride ion electrode (model: PF-2-01, manufacturer: Shanghai Leizi), the single salt bridge reference electrode (filled with saturated KCl solution, model: 232-01, manufacturer: Shanghai Leici) and the temperature electrode (model: T-818-B-6, manufacturer: Shanghai Leici) into the pF5, turn on the electromagnetic stirring, start the calibration, wait for the instrument to lock automatically, repeat the above steps to calibrate pF4 and pF3 in sequence, and save after completing the last calibration;

[0073] Chloride ion standard solution calibration: Transfer 50 mL of pCl 4 into a beaker. Insert the chloride ion reference electrode (model: P-Cl-1-01, manufacturer: Shanghai Leizi), the dual salt bridge reference electrode (outer salt bridge filled with 0.1 mol / L KNO3 solution, inner salt bridge with 3 mol / L KCl solution, using a ground glass liquid junction design to effectively reduce potential drift, requires activation with standard solution for 30 min before measurement, model: 217-01, manufacturer: Shanghai Leizi), and the temperature electrode (model: T-818-B-6, manufacturer: Shanghai Leici) into the pCl 4. Turn on the electromagnetic stirring, start the calibration, and wait for the instrument to automatically lock. Repeat the above steps to calibrate pCl 3 and pCl 2 in sequence. Save the instrument after completing the last calibration.

[0074] (4) Sample determination and data processing, specifically including the following steps:

[0075] (401) Install the chloride ion electrode, rinse the electrode after calibration with distilled water using the chloride ion electrode standard solution, insert the chloride ion electrode, the dual salt bridge reference electrode, and the temperature electrode into the test solution, turn on the stirring, start the measurement, and wait for the instrument to automatically lock and display the chloride ion concentration in the test solution.

[0076] (402) Install the fluoride ion electrode, rinse the electrode after calibration with distilled water using the fluoride ion electrode standard solution, insert the fluoride ion electrode, the double salt bridge reference electrode, and the temperature electrode into the test solution, turn on the stirring, start the measurement, and wait for the instrument to automatically lock and display the fluoride ion concentration in the test solution.

[0077] (403) Calculate the fluoride and chloride ion contents according to the following formula:

[0078]

[0079] In the above formula:

[0080] F(%): Represents the percentage content of F ions in the sample;

[0081] Cl (%): Represents the percentage content of Cl ions in the sample;

[0082] c: Represents the measured concentration value (g / L).

[0083] Example 2

[0084] Compared with Example 1, the difference in Example 2 lies in step (101), specifically:

[0085] (101) Place 0.4997g of sample in a nickel crucible pre-coated with 1.6g of flux A, then cover with 1.9g of oxidant and 3.1g of flux B in sequence. Heat the covered nickel crucible to 650℃ at a rate of 10℃ / min and hold for 15.5min. After holding, remove the nickel crucible and cool it to below 200℃. Then immerse it in hot water, boil and hold for 5min to obtain a melt. Cool the melt to room temperature and transfer it to a 100mL volumetric flask. Make up to volume with ultrapure water and filter to obtain the filtrate.

[0086] The sample was lead concentrate;

[0087] All other operating steps and parameters remain unchanged.

[0088] Example 3

[0089] Compared with Example 1, the difference in Example 3 lies in step (101), specifically:

[0090] (101) Place 0.5003g of sample in a nickel crucible pre-coated with 1.55g of flux A, then cover with 2.1g of oxidant and 3.05g of flux B in sequence. Heat the covered nickel crucible to 650℃ at a rate of 10℃ / min and hold for 14.5min. After holding, remove the nickel crucible and cool it to below 200℃. Then immerse it in hot water, boil and hold for 5min to obtain a melt. Cool the melt to room temperature and transfer it to a 100mL volumetric flask. Make up to volume with ultrapure water and filter to obtain the filtrate.

[0091] The sample was lead concentrate;

[0092] All other operating steps and parameters remain unchanged.

[0093] Verification Example 1

[0094] To simplify the operation and achieve breakthroughs in sample dissolution, this application incorporates ultrasonic sample dissolution experiments and compares the measured fluorine and chlorine contents using the alkali fusion method (i.e., the scheme of this application, corresponding to Examples 1-3) and distillation method.

[0095] The ultrasonic dissolution method experiment: Weigh 0.5000g of lead concentrate into a 100mL beaker, add 20mL of 50wt% HNO3, set the ultrasonic instrument temperature to 70℃, vibrate for 20min, filter, and obtain the filtrate. Transfer the filtrate to a 50mL volumetric flask, add 1 drop of methyl red ethanol indicator, and then add 5% nitric acid solution dropwise until the pH of the filtrate is approximately 6.0. Add TISAB solution and dilute with ultrapure water to 50mL, shake well, and the test solution is obtained. Place one magnetic stir bar in the test solution and test it using a PXSJ-216F ion meter.

[0096] The distillation sample dissolution experiment was conducted in accordance with GB / T 3884.12-2023 Chemical Analysis Methods for Copper Concentrates, Part 12: Determination of Fluorine and Chlorine Content by Ion Chromatography and Potentiometric Titration, Section 4.5.4.

[0097] The results are shown in Table 1.

[0098] Table 1

[0099]

[0100] As can be seen from this verification example, the ultrasonic dissolution method does not require high-temperature equipment and can shorten the processing cycle by 60%, making it attractive in terms of ease of operation and time efficiency. However, its incomplete decomposition of complex matrix samples leads to insufficient data reliability. Lead concentrate contains a high amount of impurities, and the sample is not completely dissolved when using this method.

[0101] While distillation can yield highly accurate results, the results are often low for high-silica materials due to incomplete distillation, and the equipment complexity and time cost make it difficult to meet the needs of batch testing.

[0102] The alkaline fusion method provided in this application, through layered covering method, optimized ratio of potassium hydroxide to potassium nitrate, and gradient heating (i.e., uniform heating to 650℃), can conveniently obtain accurate results while ensuring data quality (spiking recovery rate of 90.0-110.0%).

[0103] Furthermore, the data results from this verification example show that the results of the alkali fusion method and the distillation method are similar, while the results of the ultrasonic dissolution method are lower and the sample is not completely dissolved. The distillation method takes too long and the distillation equipment is relatively complex. Therefore, the alkali fusion method of this application is more suitable for sample decomposition than the commonly used methods on the market.

[0104] Verification Example 2

[0105] Fluorine and chloride response acidity experiment: The response acidity of fluorine is pH 6-7, and the response acidity of chloride ions is pH 2-12. Comparison of acidity experiment results in Table 2 shows that the optimal response acidity for chloride ions is pH 4. To achieve the goal of combined fluorine and chloride assay, the same acidity as fluorine was selected, and experiments were conducted according to the steps in Examples 1-3. The results are shown in Table 2.

[0106] Table 2

[0107]

[0108] This validation example demonstrates that by constructing a citrate-phosphate buffer system at pH 6-7, the simultaneous determination of fluoride and chlorine can be successfully achieved. This method overcomes the pH limitation of traditional single-ion detection and provides a reliable solution for the simultaneous determination of fluoride and chlorine in complex matrix samples.

[0109] Verification Example 3

[0110] Recovery experiment: The melt obtained in step (101) of Examples 1-3 was placed in a 100mL beaker, and 1mL, 2mL, 1mL, 2mL, 1mL, 2mL of chloride ion standard solution (1000μg / mL) were added respectively. The solution was then transferred to a 100mL volumetric flask. The subsequent determination method was the same as step (102) of each example. The spiked recovery rate was calculated and the results are shown in Table 3.

[0111] Table 3

[0112]

[0113]

[0114] As can be seen from the table above, the spiked recoveries under the method of this application are between 97.00% and 103.50%, which meets the accuracy requirements for raw material analysis (recovery rate 95%-105%).

[0115] Verification Example 4

[0116] Repeatability test: Seven cups of samples from Examples 1-3 were weighed simultaneously and the experiments were carried out according to the steps of each example. The results are shown in Table 4.

[0117] Table 4

[0118]

[0119] The table above shows that the RSD values ​​of the combined fluoride and chlorine assay are between 2% and 5%, and are not significantly different from the acceptable values.

[0120] Verification Example 5

[0121] Comparative experiment: The detection of fluoride and chlorine content in samples from Examples 1-3 was compared using ion chromatography, potentiometric titration, ion-selective electrode method (the method of this application), and turbidimetry.

[0122] Ion chromatography and potentiometric titration methods refer to parts four and five of GB / T 3884.12-2023 Chemical Analysis Methods for Copper Concentrates, Part 12: Determination of Fluorine and Chlorine Contents (Ion Chromatography and Potentiometric Titration).

[0123] References for turbidimetric method (Yuan Qi. Determination of chlorine in lead-zinc ore by sodium hydroxide fusion-silver chloride turbidimetric method [J]. Metallurgical Analysis);

[0124] The results are shown in Table 5;

[0125] Table 5

[0126]

[0127] The data in Table 5 clearly show that the results obtained using the electrode method, compared with those obtained using ion chromatography and potentiometric titration, are within the acceptable error range. This result strongly demonstrates that the ion-selective electrode method for the joint determination of fluoride and chlorine in lead concentrate is feasible in practical applications.

[0128] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0129] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for determining the fluoride and chloride content in lead concentrate using an ion-selective electrode method, characterized in that, The method specifically includes the following steps: (1) Prepare the sample into a test solution; (2) Prepare standard solutions for fluoride ion electrodes and chloride ion electrodes; (3) Standardization of fluoride ion standard solution and chloride ion standard solution; (4) Sample determination and data processing.

2. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 1, characterized in that, Step (1) specifically includes the following steps: (101) Place the sample in a nickel crucible pre-coated with flux A, then cover it with oxidant and flux B in sequence. Heat the covered nickel crucible at a uniform rate and keep it at that temperature. After the heat preservation is completed, remove the nickel crucible and cool it once. Then immerse it in hot water, boil it and keep it for 5 minutes to obtain the melt. Cool it a second time, make the melt to a fixed volume, filter it, and obtain the filtrate. (102) Transfer the filtrate to the volumetric flask, add methyl red ethanol indicator, then add nitric acid solution dropwise, add TISAB solution and dilute, shake well to obtain the test solution, put 1 magnetic stir bar into the test solution and set aside.

3. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 2, characterized in that, The mass ratio of the sample, flux A, oxidant and flux B in step (101) is 0.4997-0.5003:1.55-1.6:1.9-2.1:3.0-3.

1.

4. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 2, characterized in that, The oxidant includes potassium nitrate, and flux A and flux B are both potassium hydroxide.

5. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 2, characterized in that, The samples mentioned in step (101) include lead concentrate, zinc concentrate, and water-quenched slag.

6. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 5, characterized in that, The sample in step (101) includes lead concentrate.

7. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 2, characterized in that, In step (102), the volumetric flask is a 50 mL volumetric flask, the amount of methyl red ethanol indicator added is 1 drop, the amount of nitric acid solution added is until the pH of the filtrate is ≈6.0, the volume of the filtrate transferred is 20 mL, the amount of TISAB solution added is 10 mL, and the dilution is to dilute with ultrapure water to 50 mL.

8. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 1, characterized in that, The fluoride ion electrode standard solution and the chloride ion electrode standard solution mentioned in step (2) are both three-gradient standard solutions, wherein: The standard solution for the fluoride ion electrode is: 1×10 -3 mol / L (pF3), 1×10 -4 mol / L (pF4), 1×10 -5 mol / L (pF5); The standard solution for the chloride ion electrode is: 1×10 -2 mol / L (pCl 2), 1×10 -3 mol / L (pCl 3), 1×10 -4 mol / L (pCl 4).

9. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 1, characterized in that, Step (3) specifically includes the following steps: Fluoride ion standard solution calibration: Transfer 50 mL of pF5 into a plastic cup, insert the fluoride ion electrode, single salt bridge reference electrode and temperature electrode into pF5 together, turn on the electromagnetic stirring, start the calibration, wait for the instrument to lock automatically, repeat the above steps to calibrate pF4 and pF3 in turn, and save after completing the last calibration; Chloride ion standard solution calibration: Transfer 50 mL of pCl4 into a beaker, insert the chloride ion reference electrode, the double salt bridge reference electrode, and the temperature electrode into the pCl4, turn on the electromagnetic stirring, start the calibration, wait for the instrument to automatically lock, repeat the above steps to calibrate pCl3 and pCl2 in sequence, and save after completing the last calibration.

10. The method for determining the fluoride and chloride content in lead concentrate using the ion-selective electrode method according to claim 1, characterized in that, Step (4) specifically includes the following steps: (401) Install the chloride ion electrode, rinse the electrode after calibration with distilled water using the chloride ion electrode standard solution, insert the chloride ion electrode, the dual salt bridge reference electrode, and the temperature electrode into the test solution, turn on the stirring, start the measurement, and wait for the instrument to automatically lock and display the chloride ion concentration in the test solution. (402) Install the fluoride ion electrode, rinse the electrode after calibration with distilled water using the fluoride ion electrode standard solution, insert the fluoride ion electrode, the double salt bridge reference electrode, and the temperature electrode into the test solution, turn on the stirring, start the measurement, and wait for the instrument to automatically lock and display the fluoride ion concentration in the test solution. (403) Calculate the fluoride and chloride ion contents according to the following formula: In the above formula: F(%): Represents the percentage content of F ions in the sample; Cl (%): Represents the percentage content of Cl ions in the sample; c: Represents the measured concentration value (g / L).

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