Method for detecting four anions in hydrometallurgy electrolyte

Abstract

The invention relates to a method for detecting four anions in a hydrometallurgy electrolyte. The detection method comprises the following steps: pretreating resin, cleaning a resin layer, pretreating a sample, carrying out ion exchange, preparing a series of mixed standard solutions, carrying out chromatographic sample introduction, and carrying out chromatographic sample introduction. The method can be used for simultaneously detecting four anions such as F <->, Cl <->, NO3 <-> and SO4 < 2->, is accurate and rapid, and has very high practicability and a satisfactory detection result.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte detection, and relates to a method for detecting four anions in hydrometallurgical electrolytes. Technical Background

[0002] Hydrometallurgical refining refers to the process of leaching the effective components from the ore using a leaching agent, and then obtaining the metal from the purified leachate using chemical extraction or electrolytic extraction. After decades of research and development, hydrometallurgical refining technology has made significant progress in terms of industrial application scale and process maturity, and is rapidly becoming a major method for processing low-grade raw ores, oxide ores, and some complex minerals, demonstrating broad industrial application prospects and significant development value. During the electrolytic process in hydrometallurgical refining, the electrolyte often contains sulfur dioxide (F). - Cl - NO3 - SO4 2- Anions, such as copper, cobalt, and nickel, not only affect the electrolysis process but are also key indicators for evaluating the efficient recovery of metal resources from the electrolyte. However, it is well known that the presence of high concentrations of metal cations such as copper, cobalt, and nickel in actual electrolytes can severely interfere with the accurate determination of anions.

[0003] Ion chromatography, as a highly efficient technique for analyzing inorganic anions, faces significant challenges in practical applications: large amounts of heavy metal ions can easily poison and damage the chromatographic column, making it difficult to directly use for the determination of anions in electrolyte samples. Cation exchange resins, on the other hand, are functional polymers containing ion exchange groups in their cross-linked polymer structure. These polymers are extremely stable and insoluble in acidic, alkaline, and organic solvents, structurally belonging to porous solid polymers that are neither soluble nor molten. Furthermore, each resin particle consists of a cross-linked, three-dimensional network framework with numerous reactive functional groups attached. These functional groups can dissociate ions and exchange with surrounding ions. Therefore, cation exchange resins can utilize heavy metal ions to reduce the concentration of heavy metals in wet electrolytes to an acceptable level, thus pretreating the wet electrolyte. Moreover, cation exchange resins have the advantage of reusability, allowing regeneration after adsorption saturation. The regeneration here utilizes the fact that the ions in the regenerator are in an absolutely dominant concentration to wash away the ions on the ion exchange resin, thereby restoring the ion exchange resin's exchange capacity.

[0004] Currently, commonly used methods for detecting anions in electrolytes include spectrophotometry, ion-selective electrode methods, potentiometric titration, and titration. Among these, spectrophotometry is complex to operate, requires large amounts of reagents, and has poor stability of results. Ion-selective electrode methods have a narrow detection range, and each element requires a specific ion-electrode. However, the complex matrix in the electrolyte also significantly affects ion-selective electrode methods, making them unsuitable for large-scale multi-element analysis. For titration methods, the analytical results are greatly affected by the matrix. If the electrolyte contains a large amount of sulfuric acid, the pH of the matrix will significantly affect the titration, leading to poor accuracy and reproducibility of the results. In contrast, ion chromatography has a lower detection limit and a higher degree of automation than methods such as ion-selective electrodes, offering significant advantages.

[0005] In summary, how to avoid the shortcomings of the above technologies and utilize their advantages to control F in electrolytes is a key issue. - Cl - NO3 - SO4 2- The analysis and detection of anions is a critical issue that urgently needs to be addressed in the field of anion detection technology in hydrometallurgical processes. Summary of the Invention

[0006] To address the problems existing in the aforementioned technologies, the inventors have, through careful research, discovered an accurate, rapid, and highly practical method for detecting four anions in hydrometallurgical electrolytes. This method can simultaneously detect F... - Cl - NO3 - SO4 2- It detects four types of anions, including ions, and provides satisfactory detection results.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for detecting four anions in a hydrometallurgical electrolyte, characterized by the following steps: Step 1: Pretreatment of resin: Activate the cation exchange resin with deionized water, and rinse the cation exchange resin sequentially with 2-7% dilute sodium hydroxide solution and 2-6% dilute hydrochloric acid.

[0008] Step 2, Cleaning the resin layer: The pretreated cation exchange resin from Step 1 is loaded into a polyethylene exchange column, with a resin layer height of 6-12 cm; the resin layer is first backwashed with deionized water, and then cleaned sequentially with sodium hydroxide solution, hydrochloric acid solution, and deionized water. Step 3, Sample pretreatment: Collect the electrolyte sample into a high-density polyethylene bottle that has been washed with deionized water, filter it to remove larger impurities, and store it in a sealed container at 4°C away from light until use.

[0009] Step 4, Ion exchange: Take 50 ml of the electrolyte sample after step 3, pack it into the cation exchange resin column after step 2, and perform cation resin exchange. Step 5: Preparation of mixed standard solution series: Transfer 10 mL of the mixed standard stock solution of fluoride, chloride, nitric acid, and sulfate to a 100 mL volumetric flask, dilute to volume, and shake well to obtain the standard stock solution; transfer 0, 0.50, 1.25, 2.50, 5.00, 12.5, and 25.0 mL of the standard stock solution to 25 mL small volumetric flasks, dilute to volume, and shake well to obtain the mixed standard solution series for later use; Step 6: Chromatographic injection Na2CO3 / NaHCO3 was used as the eluent, with a ratio ranging from 2.6:1 to 3.4:1. The eluent was flowed through the column at a flow rate of 0.5-2.0 mL / min, and the column temperature was set to 30-39℃. The sample treated in step 4 was subjected to chromatographic testing with an injection volume ranging from 5 to 25 μL, and the test results were recorded. Step 7: Determine the content of anions; determine the content of various anions in the electrolyte sample based on the mixed standard curve prepared in Step 5 and the chromatographic test results in Step 6.

[0010] Furthermore, in step 1, dilute hydrochloric acid is used to remove inorganic impurities from the resin, which are mainly iron compounds; in addition, sodium hydroxide solution is used to remove organic impurities from the resin, such as halogenated hydrocarbons, esters, oils, proteins, and some nitrogen-containing organic compounds.

[0011] In step 1, the cation exchange resin includes strongly acidic cation exchange resin, weakly acidic cation exchange resin, and chelating cation exchange resin, all of which can be used for the removal of metal ions. However, since the pH of the hydrometallurgical electrolyte sample is less than 2, a strongly acidic cation exchange resin is selected as the optimal resin material for this acidic environment. The strongly acidic cation exchange resin can be a hydrogen-form cation exchange resin, a sodium-form cation exchange resin, or a macroporous cation exchange resin. In this invention, a hydrogen-form cation exchange resin is preferred.

[0012] In step 2, the specific operation of cleaning the resin layer with sodium hydroxide solution, hydrochloric acid solution, and deionized water is as follows: Pass 4% NaOH (2 times the resin volume) through the resin layer at a flow rate of 2-10 mL / min, exceeding the resin layer by 0.2 cm, and soak for 2-4 hours. Then, wash with hydrochloric acid at a flow rate of 10-15 mL / min until the effluent is acidic. Next, pass 4% HCl (2 times the resin volume) through the resin layer, exceeding the resin layer by 0.2 cm, and soak for 2-4 hours. Then, wash with deionized water until the effluent is neutral and no chloride or sulfate ions are detected.

[0013] The purpose of backwashing with deionized water in step 2 is to remove fine resin fragments and impurities generated during the filling process, and to stratify the resin particles according to size, with finer particles at the top and the largest at the bottom, thereby optimizing fluid distribution and reducing pressure drop and channeling. The rinsing with sodium hydroxide, hydrochloric acid, and deionized water in step 1 is mainly to remove fine impurities, compact and balance the column bed, ensuring a uniform and flat cation exchange column bed free of visible bubbles, cracks, and channeling. This allows the cation exchange column to form stable and efficient ion exchange channels for better ion exchange performance.

[0014] In step 3, the electrolyte comes from the hydrometallurgical plant of a hydrometallurgical company. The collected solution is the electrolyte solution after the cathode copper has been electrolyzed. Therefore, the electrolyte mainly contains metal ions such as copper, cobalt, iron, nickel, manganese, and zinc.

[0015] In step 3, the sample processing involves thoroughly shaking the electrolyte sample, observing the color intensity of copper ions in the electrolyte sample, and then diluting the sample 5 to 10 times with deionized water. If the color is light, dilution is not necessary.

[0016] In step 4, the cation exchange resin ion-exchanges the sample several times (generally 3 to 5 times, rinsing until the blue color of the sample solution disappears) through the packed resin column, and the column is washed multiple times with approximately 50 ml of ultrapure water. The solution is then transferred to a volumetric flask and diluted to volume. Finally, 5 mL of the solution is filtered through a 0.45 μm filter membrane. The used cation exchange resin is then soaked in HCl (1+1) to a depth of 0.2 cm above the resin layer for 1-2 hours, followed by repeated rinsing with deionized water until the effluent is neutral and no chloride or sulfate ions are detected.

[0017] In step 6, the concentrations and ratios of the two eluents (Na2CO3 / NaHCO3) were optimized through a series of experiments. The preferred ratio was 2.7:1 to 3.2:1. Among these, the best anion separation effect in the electrolyte was achieved when the concentration of Na2CO3 in the eluent was in the range of 2.8 to 3.6 mmol / L and the concentration of NaHCO3 was in the range of 0.8 to 1.5 mmol / L.

[0018] In addition, column temperature, flow rate, and optimal injection volume were also examined. Those skilled in the art will know that these parameters have a significant impact on the actual sample test results, and it is necessary to comprehensively consider the elution time of the anion, resolution, sensitivity, and the reproducibility of the overall analytical test results to optimize these key parameters. Specifically, a flow rate of 0.7–1.5 mL / min for the eluent was preferred, along with a column temperature set in the range of 30–39 °C, and an injection volume in the range of 5–20 μL for chromatographic testing.

[0019] Furthermore, this invention utilizes a Metrosep A Supp 5 (150 mm) analytical column and a Metrosep RP 2 Guard guard column. The Metrosep A Supp 5 (150 mm) analytical column provides reliable separation due to its high capacity and excellent peak shape, while the Metrosep RP 2 Guard guard column protects the analytical column by intercepting contaminants. The synergistic operation of these two components is crucial for the analysis and detection of anions in complex hydrometallurgical electrolytes. The Metrosep A Supp 5 series is recommended by the manufacturer for implementing international standard methods such as EPA 300.1 and DIN / ISO 10304-1, ensuring that the analytical results comply with regulatory requirements and that the data is comparable and traceable.

[0020] Specifically, the eluent flow rate affects the ion elution time, resolution, and sensitivity. To determine the optimal flow rate, retention time and peak area were measured at different flow rates. The results showed that when the eluent flow rate was too high (greater than 2.0 mL / min), the ion retention time was shortened, the ion resolution was poor, and the sensitivity decreased; conversely, when the eluent flow rate was too low (less than 0.5 mL / min), the detection time was too long, reducing the measurement efficiency. Therefore, the preferred eluent flow rate range is 0.7–1.5 mL / min. Furthermore, the results indicated that satisfactory results were obtained at the optimal flow rate, and the entire analysis was completed within 26.0 min.

[0021] In addition, column temperature affects the resolution, retention time, column pressure, reproducibility, and instrument stability of chromatographic peaks. The results show that a column temperature range of 30℃ to 39℃ provides good separation of fluoride, chloride, nitric acid, and sulfate ions, while also shortening retention time, reducing column pressure, maintaining good reproducibility, and increasing instrument stability.

[0022] Beneficial effects of the present invention The method for detecting four anions in hydrometallurgical electrolytes according to the present invention has the following beneficial effects: 1. Pretreated cation exchange resin columns can efficiently remove high concentrations of heavy metal cations from electrolyte samples, effectively solving the problem of "poisoning" of these cations on ion chromatography separation columns, and providing a feasible pretreatment solution for direct chromatographic analysis of complex matrix electrolyte samples.

[0023] 2. This invention uses a Metrosep A Supp 5 analytical column and a Metrosep RP 2 Guard protective column, optimizing the injection volume and column temperature, making the invention more practical and widely applicable.

[0024] 3. The entire analysis process of this invention automatically injects, analyzes, and generates test results for the sample, with an analysis time of 26 minutes, saving time and labor, and making it faster and more convenient.

[0025] 4. The entire analytical process of this invention only requires the addition of deionized water, without the need for other chemical reagents. Operators do not need to come into contact with toxic or harmful organic solvents, and sample testing is convenient, saving manpower and time, and is beneficial for the analysis and detection of large batches of samples.

[0026] 5. The analytical method described in this invention has a small standard deviation and a spiked recovery rate of 98.3% to 105.9%, and can be used for the analysis and detection of large batches of samples.

[0027] 6. The operation is relatively simple, the results are accurate and reliable, and the degree of automation is high. It can realize the rapid and simultaneous determination of four anions, which solves the problem of anion detection in complex matrix samples such as hydrometallurgical electrolytes. It provides an effective analytical tool for hydrometallurgical process monitoring, electrolyte purification and metal recovery efficiency evaluation. Attached Figure Description

[0028] Figure 1 The ion chromatogram of the mixed standard solution obtained by injection using the ion chromatography parameters of the present invention is shown. Figure 2 The ion chromatogram of the actual sample in Example 1 is shown below. Figure 3 The linear relationship of the fluoride ion standard curve of the standard solution of the present invention; Figure 4 The relationship between the chloride ion line standard curve of the standard solution of the present invention and the actual situation; Figure 5 The linear relationship of the nitrate ion standard curve of the standard solution of the present invention; Figure 6 This represents the linear relationship of the sulfate ion standard curve of the standard solution of this invention. Detailed Implementation

[0029] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. Each embodiment is merely an example of the technical solutions of the present invention and is not intended to limit the scope of protection. The specific details are as follows: The present invention discloses a method for detecting four anions in an electrolyte, characterized in that the analytical detection method includes the following steps: Step 1: Pretreatment of resin: Activate the cation exchange resin with deionized water, and then rinse the cation exchange resin sequentially with 2-7% dilute sodium hydroxide solution and 2-6% dilute hydrochloric acid. The cation exchange resin is a strongly acidic cation exchange resin.

[0030] Step 2: Cleaning the resin layer: Fill the polyethylene exchange column with the cation exchange resin pretreated in Step 1 to a height of 6-12 cm. The resin layer is first backwashed with deionized water, and then 4% NaOH (twice the volume of the resin) is passed through the resin layer at a flow rate of 2-10 mL / min, exceeding the resin layer by 0.2 cm, and soaked for 2-4 hours. Then, it is rinsed with hydrochloric acid solution at a flow rate of 10-15 mL / min until the effluent is acidic. Then, 4% HCl (twice the volume of the resin) is passed through the resin layer exceeding the resin layer by 0.2 cm, and soaked for 2-4 hours. Finally, it is washed with deionized water until the effluent is neutral and no chloride or sulfate ions are detected.

[0031] Step 3, Sample pretreatment: Collect the electrolyte sample into a high-density polyethylene bottle cleaned with deionized water, filter, shake thoroughly, and then dilute the sample 5 to 10 times with deionized water by observing the color intensity of copper ions in the electrolyte sample. Store the sample in a sealed container at 4°C away from light for later use.

[0032] Step 4, Ion Exchange: Take 50 ml of the electrolyte sample treated in Step 3 and pass it through the cation exchange resin column treated in Step 2 several times. Wash the column repeatedly with 50 ml of ultrapure water, then transfer it to a volumetric flask and dilute to volume. Finally, take 5 mL of the solution and filter it through a 0.45 μm filter membrane. Separate the used cation exchange resin and soak it in HCl (1+1) solution, ensuring the solution is 0.2 cm above the resin layer, for 1-2 hours. Then rinse repeatedly with deionized water until the effluent is neutral and no chloride or sulfate ions are detected. (The purpose of this cleaning step is to use the ions in the regenerator, where their concentration is absolutely dominant, to elute the ions from the ion exchange resin, restoring its exchange capacity for reuse in the next batch of samples.) Step 5: Preparation of mixed standard solution series: Transfer 10 mL of the mixed standard stock solution of fluoride, chloride, nitric acid, sulfate, etc., to a 100 mL volumetric flask, dilute to volume and shake well to obtain the standard stock solution; transfer 0.50, 1.25, 2.50, 5.00, 12.5, and 25.0 mL of the standard stock solution to a 25 mL volumetric flask, dilute to volume and shake well to obtain the mixed standard solution series, and prepare a standard curve of anion mixed standard for later use; Step 6: Chromatographic injection and parameter selection The chromatographic columns used included a Metrosep A Supp 5 analytical column and a Metrosep RP 2 Guard guard column. Na2CO3 / NaHCO3 was used as the eluent, with a ratio ranging from 2.6:1 to 3.4:1. The operating parameters of the ion chromatograph were as follows: the eluent was flowed through at a flow rate ranging from 0.5 to 2.0 mL / min, the column temperature was set to a range of 30 to 39 °C, and chromatographic tests were performed with an injection volume ranging from 5 to 25 μL. The test results were recorded. Step 7: Determine the content of anions: Determine the content of various anions in the electrolyte sample based on the standard curve of the anion mixed standard prepared in Step 5 and the chromatographic test results in Step 6.

[0033] For the above testing method, the determination of several specific parameters is illustrated with the following examples: In the preferred embodiment of the present invention, the eluent concentration is determined by the following experimental method: taking a 3.2 mmol / L Na2CO3 and 1.0 mmol / L NaHCO3 solution as an example, the eluent concentration is selected under the premise of ensuring that the peak height, peak area, peak shape and resolution of the sample peaks reach the ideal state, so as to ensure analytical accuracy, while reducing the consumption of reagents and saving consumable costs.

[0034] Regarding column temperature and injection volume, the column temperature is 30-39℃, preferably 35℃; the injection volume is 5-25μL, preferably 10μL; 0.1mol / L H2SO4 is used as the regeneration solution for the MSM chemical suppressor; and the analysis time is 20-40min, preferably 26min. The aforementioned MSM suppressor is an "ion-exchange membrane reactor" that converts the highly conductive alkaline eluent into water and simultaneously converts the salt of the analyte ion into the corresponding highly conductive acid. In anion analysis, we use alkaline solutions such as sodium carbonate / sodium bicarbonate as eluents. These eluents themselves have high conductivity and can overwhelm the signal of the analyte anions (such as Cl⁻, NO3⁻, SO4²⁻). The suppressor is used to "neutralize" or "eliminate" the conductivity of the eluent. 0.1 mol / L H2SO4 is the most commonly used regeneration solution for the MSM suppressor in anion analysis. The regenerated liquid serves several purposes: First, it provides an H⁺ source, which is its primary function. H⁺ acts as the "fuel" for the inhibition reaction, replacing Na⁺ in the eluent to achieve inhibition. Second, it maintains ion balance by receiving Na⁺ exchanged from the sample chamber while providing H⁺, generating Na₂SO₄, which is then discharged as waste liquid. Third, it drives the flow of waste liquid. The regenerated liquid not only provides ions, but its flow also helps to carry the waste liquid (Na₂SO₄ solution) generated during the exchange out of the suppressor, keeping the system clean and stable.

[0035] The sample injection volume was determined through the following experimental methods: selecting the minimum injection volume while ensuring the peak height, peak area, peak shape, and resolution of the sample peaks are ideal. The mobile phase flow rate and analytical column temperature were determined through the following experimental methods: selecting the most suitable flow rate and temperature values ​​based on previous experience while ensuring the peak height, peak area, peak shape, and resolution of the sample peaks are ideal. In a preferred embodiment of the present invention, the inner diameter of both the Metrosep A Supp 5 analytical column and the Metrosep RP2 Guard guard column is 4 nm.

[0036] Unless otherwise specified, all chemical substances used in this embodiment are of conventional reagent chemical purity level. The experimental equipment used in the embodiment is shown in Table 1.

[0037] Table 1 shows the experimental equipment used in the embodiments.

[0038] Example 1: Analytical Detection Method for Determining Anions in Samples (1) Activate the cation exchange resin (hydrogen-type cation exchange resin) with deionized water, and rinse the cation exchange resin with 4% dilute sodium hydroxide solution and 5% dilute hydrochloric acid in sequence.

[0039] (2) 8 cm of pretreated cation exchange resin is packed into a polyethylene exchange column. The resin layer is first backwashed with deionized water, and then 4% NaOH with a flow rate of 4 mL / min is passed through the resin layer at a flow rate of 2 times the resin volume, and the flow rate exceeds the resin layer by 0.2 cm for 2.5 hours. Then it is rinsed with hydrochloric acid solution at a flow rate of 12 mL / min until the effluent is acidic. After that, 4% HCl with a flow rate of 2 times the resin volume is passed through the resin layer at a flow rate of 0.2 cm, and the flow rate is exceeded for 3 hours. Then it is washed with deionized water until the effluent is neutral and no chloride ions or sulfate ions are detected.

[0040] (3) Shake the pretreated electrolyte sample (the sample solution is the electrolyte solution after the cathode copper has been electrolyzed) thoroughly. If the copper ions in the electrolyte sample are light in color, the electrolyte solution can be used directly without dilution.

[0041] (4) Take 50 ml of the electrolyte sample after step 3 and load it into the cation exchange resin column after step 2 several times. Wash the column several times with 50 ml of ultrapure water, and put it into a volumetric flask and make up to volume. Finally, take 5 mL of the solution and filter it through a 0.45 μm filter membrane. Soak the cation exchange resin after separation in HCl (1+1) for 1-2 hours, 0.2 cm above the resin layer. Then rinse it repeatedly with deionized water until the effluent is neutral and no chloride or sulfate ions are detected. (5) Prepare an anion mixed standard curve: 1) Prepare the anion-mixed standard stock solution F - (200mg / L), Cl -（ 300mg / L), NO3 - (1000mg / L), SO4 2- (1500mg / L), NO2 - (1000mg / L), Br - (1000mg / L), Cl - (300mg / L), PO4 2- (1500mg / L), store in a refrigerator at 4℃.

[0042] 2) Anion-mixed standard working solution: Pipette 10.0 mL of the standard stock solution from step 1) and dilute to 100.0 mL with pure water. This standard working solution contains F. - (20mg / L), Cl - (30mg / L), NO3 - (100mg / L), SO4 2- (150mg / L), NO2 - (100mg / L), Br - (100mg / L), Cl - (30mg / L), PO4 2- (150mg / L), freshly prepared on the same day.

[0043] 3) Standard solutions: Take 0.50, 1.25, 2.50, 5.00, 12.5, and 25.0 mL of the standard stock solution from the steps and dilute to volume in a 25 mL volumetric flask. This series of standard solutions contains fluoride concentrations of 0.40, 1.00, 2.00, 4.00, 10.0, and 20.0 mg / L, chloride concentrations of 0.60, 1.50, 3.00, 6.00, 15.0, and 30.0 mg / L, nitrate concentrations of 2.00, 5.00, 10.0, 20.0, 50.0, and 100.0 mg / L, and sulfate concentrations of 3.0, 7.50, 15.0, 30.0, 75.0, and 150.0 mg / L. These mixed standard solutions should be freshly prepared on the same day.

[0044] 4) The series of standard solutions prepared in step 3) were analyzed by injection using an ion chromatograph. A standard curve was plotted using peak height or peak area (Y) against solution concentration (X). The instrument automatically calculated the linear regression curve, as shown below. Figures 3-6 As shown, the linear regression curves of the standard curves for fluoride ions, chloride ions, nitrate ions, and sulfate ions of the standard solution of the present invention are shown in order.

[0045] from Figure 3 , Figure 4 , Figure 5 , Figure 6 It can be seen that the linear relationships of fluoride ions (0.4–20.0 mg / L), chloride ions (0.6–30.0 mg / L), nitrate ions (2.0–100.0 mg / L), and sulfate ions (3.0–150.0 mg / L) are good (r > 0.9995). Therefore, the method of this invention has a wide linear range and good linear relationship, and is considered to have the advantages of wide applicability, high efficiency and labor saving, high quantitative accuracy, reliable results, strong robustness, and good anti-interference ability.

[0046] (6) A Metrosep A Supp 5 anion exchange column and a Metrosep RP 2 Guard anion protection column (4 mm × 50 mm) were used, along with an MSM chemical suppressor, a conductivity detector, 3.2 mmol / L Na2CO3 and 1.0 mmol / L NaHCO3 as eluents, and 0.1 mol / L H2SO4 as suppressor regeneration solution. The flow rate was 0.8 mL / min, the injection volume was 10.0 μL, the column temperature was 35.0℃, and the run time was 26 min. The reagent used was pure water: ultrapure water was prepared using a UPU ultrapure water system, with a resistivity >18.0 MΩ·cm, free of target ions, and filtered through a 0.45 μm filter membrane. The standard solutions prepared in step 5 using the above parameters were injected sequentially in ascending order of resistivity for analysis and detection. Figure 1 The image shows the ion chromatogram of the mixed standard solution obtained by injection using the ion chromatography parameters of this invention.

[0047] from Figure 1 It can be seen that the ion chromatograms obtained using the ion chromatography parameters of the present invention have regular peak shapes and appropriate resolution, which is beneficial for qualitative and quantitative analysis, and the analysis time (the running time is 26 minutes for the processed electrolyte sample) is reasonable.

[0048] (7) Determine the content of the four anions in the sample. Using 3.2 mmol / L Na₂CO₃ and 1.0 mmol / L NaHCO₃ as eluents, 0.1 mol / L H₂SO₄ as the suppressor regeneration solution, a flow rate of 0.8 mL / min, a sample injection volume of 10.0 μL, and a column temperature of 35.0℃, a Metrosep RP 2Guard anion exchange guard column (4 mm × 50 mm) and a Metrosep A Supp 5 (4 mm × 150 mm) anion exchange separation column were used to sequentially inject the six standard solutions prepared in step 5 in ascending order of concentration. The injection type was selected as standard samples. The MagIC Net 4.0 system automatically identified each anion component according to the preset method, integrated the data, and plotted a standard curve with peak area (Y) against solution concentration (X). The instrument automatically calculated the linear regression curves. The linear relationships of fluoride, chloride, nitrate, and sulfate ions are shown below. Figure 3 , Figure 4 , Figure 5 , Figure 6 .

[0049] The samples processed in step 4 were analyzed using a Metrosep RP 2 Guard anion exchange column (4 mm × 50 mm) and a Metrosep A Supp 5 (4 mm × 150 mm) anion exchange column under the following conditions: 3.2 mmol / L Na2CO3, 1.0 mmol / L NaHCO3 as eluent, 0.1 mol / L H2SO4 as inhibitor regeneration solution, a flow rate of 0.8 mL / min, a sample injection volume of 10.0 μL, and a column temperature of 35.0 °C. After the sample is measured, the ion chromatography instrument system will automatically identify each component based on the elution time of the anionic components in the sample, and calculate the concentrations of fluoride, chloride, nitrate, and sulfate in the processed sample based on the peak area and the linear regression curve from step 5. The concentrations are 0.123 mg / L, 2.13 mg / L, 0.76 mg / L, and 32.98 mg / L, respectively. The cathode copper electrolyte solution sample was diluted by 2 times after the treatment in step 4. Therefore, the concentrations of fluoride, chloride, nitrate, and sulfate in the cathode copper electrolyte solution sample are 0.25 mg / L, 4.26 mg / L, 1.52 mg / L, and 65.96 mg / L, respectively. Figure 2The ion chromatograms obtained by the method of this invention for the actual sample of the electrolyte solution after electrolysis of the cathode copper (sample of Example 1) show good separation and high sensitivity of fluoride, chloride, nitrate, and sulfate ion components, with symmetrical, sharp, and baseline-separated peaks. It can be seen that the electrolyte sample treated by this invention (sample of Example 1) proves that this invention can efficiently remove high concentrations of heavy metal cations from electrolyte samples, effectively solving the problem of "poisoning" of these cations on the ion chromatography column. Furthermore, the entire analysis process is automated, involving sample injection, analysis, and result generation. The analysis time is short, and no toxic or harmful chemical reagents need to be added. This method can be applied to the detection of anions in large quantities of complex matrix electrolyte samples.

[0050] Figure 1 The chromatogram of the standard solution obtained by injection using the ion chromatography parameters of the present invention in step 5 is shown as an example of the sample ion chromatogram of the standard solution, illustrating the separation of each anionic component under the optimal conditions optimized by the method of the present invention. Figure 2 The image shows the ion chromatograms of an actual sample of the electrolyte solution after electrolysis of the cathode copper (sample of Example 1) after being processed by the method of the present invention. As can be seen from the image, the electrolyte sample processed by the method of the present invention can efficiently remove high concentrations of heavy metal cations in the sample and can remove interference from complex matrices. Therefore, it is very easy to detect the four anions simultaneously at each corresponding displacement in the detection of hydrometallurgical electrolyte samples.

[0051] Example 2 Methodological Validation 1) Limit of detection and limit of quantification Following the method in step 5, mixed standard solutions of different concentrations were prepared. The ion chromatograph was switched to anion exchange system, started, and after the baseline stabilized for 30 minutes, the instrument operating conditions were set. The peak area and retention time were measured under the same chromatographic conditions. A standard curve was plotted using peak area against ion concentration (mg / L). The linear regression equation and correlation coefficient of the method are shown in Table 2. Under the same conditions, the peak area (A) and response value of the blank sample were measured, and the slope S of the standard curve and the standard deviation S0 of the response values ​​of the blank sample for 11 consecutive injections were calculated. A (Fluorine: 0.002008, Chlorine: 0.00227, Nitrate: 0.001889, Sulfate: 0.00278), according to the formula QL=3S A The detection limits for each component were calculated to be 0.0192–0.0482 mg / L (see Table 2). The results indicate that the method has a wide linear range, good correlation, and low detection limits.

[0052] Table 2 Linear regression equations and correlation coefficients

[0053] 2) Precision and Spike Recovery Experiment The electrolyte sample solution (sample of Example 1) was processed according to the above steps. The same electrolyte sample was injected eight times consecutively for precision testing. After determining its baseline value, a standard solution of a certain concentration was added and processed in the same way as the sample. The samples were then injected eight more times for recovery testing (see Table 3). The results showed that the relative standard deviation (RSD) of the electrolyte samples was 0.72%, 1.26%, 0.68%, and 2.40%. These low values ​​indicate that the detection method of the present invention has low dispersion and high precision. The spiked recoveries were 98.30%, 105.90%, 99.60%, and 98.70%. A spiked recovery within this range indicates good accuracy of the test method of the present invention. Furthermore, the results in Table 3 also show that the analytical detection method of the present invention has good reproducibility, low standard deviation, and a spiked recovery of 98.3%-105.9%. This method can be applied to the analysis and detection of large quantities of hydrometallurgical electrolyte samples.

[0054] Table 3 Precision and Spike Recovery Experiments

[0055] Example 3: Actual Sample Testing Using the testing method of this invention, eight electrolyte samples (1-8) were collected from different locations in the hydrometallurgical plant of a hydrometallurgical company. The concentrations of four inorganic anions were determined according to the method and conditions of this invention. Because the company uses a sulfuric acid leaching process, the sulfate concentration at some sampling points was particularly high. The actual samples needed to be diluted to an appropriate multiple for retesting. The test results are shown in Table 4.

[0056] Table 4. Results of anion determination in samples of hydrometallurgical electrolyte.

[0057] Depend on Figure 4 The actual concentrations of fluoride ions in the electrolyte solution samples after electrolysis of the cathode copper were found to be 0.18–1.62 mg / L, chloride ions 3.23–8.19 mg / L, nitrate ions 0.56–1.23 mg / L, and sulfate ions 261–4561 mg / L. These results are consistent with the actual conditions of the electrolyte solution samples after electrolysis of the cathode copper. The concentrations of the four anions fluctuate depending on the ore properties and the hydrometallurgical process. Furthermore, the sulfate ion concentration tends to be higher due to the use of dilute sulfuric acid leaching in the hydrometallurgical process, requiring most samples to be diluted to an appropriate ratio for retesting. The test results from actual electrolyte solution samples demonstrate that this invention enables rapid and simultaneous determination of the four anions, solving the problem of anion detection in complex matrix samples such as hydrometallurgical electrolytes. This provides an effective analytical tool for hydrometallurgical process monitoring, electrolyte purification, and metal recovery efficiency evaluation.

[0058] In summary, the analytical method described in this invention exhibits a small standard deviation and a spiked recovery rate of 98.3%-105.9%, which is beneficial for the analysis of large batches of samples. Furthermore, this invention utilizes a Metrosep A Supp 5 anion separation column and a Metrosep RP 2 Guard anion protection column, optimizing the injection volume and column temperature, thus enhancing its practicality and scalability. In practical applications, it has yielded reliable results in the analysis of electrolyte samples from hydrometallurgical plants. The method of this invention is relatively simple to operate, provides accurate and reliable results, and has a high degree of automation. It enables the rapid and simultaneous determination of four anions, solving the challenge of anion detection in complex matrix samples such as hydrometallurgical electrolytes, and has significant practical application value.

Claims

1. A method for detecting four anions in a hydrometallurgical electrolyte, characterized in that, This method has the following steps: Step 1: Pretreatment of resin: Activate the cation exchange resin with deionized water, and rinse the cation exchange resin sequentially with 2-7% dilute sodium hydroxide solution and 2-6% dilute hydrochloric acid. Step 2, Cleaning the resin layer: The pretreated cation exchange resin from Step 1 is loaded into a polyethylene exchange column, with a resin layer height of 6-12 cm; the resin layer is first backwashed with deionized water, and then cleaned sequentially with sodium hydroxide solution, hydrochloric acid solution, and deionized water; Step 3, Sample pretreatment: Collect the electrolyte sample into a high-density polyethylene bottle that has been washed with deionized water, filter it to remove larger impurities, and store it in a sealed container at 4°C in the dark until use. Step 4, Ion exchange: Take 50 ml of the electrolyte sample after step 3 and fill it into the cation exchange resin column after step 2 for cation resin exchange. Step 5: Preparation of mixed standard solution series: Transfer 10 mL of the mixed standard stock solution of fluoride, chloride, nitric acid, sulfate, etc. to a 100 mL volumetric flask, dilute to volume and shake well to obtain the standard stock solution; transfer 0.50, 1.25, 2.50, 5.00, 12.5, and 25.0 mL of the standard stock solution to a 25 mL small volumetric flask, dilute to volume and shake well to obtain the mixed standard solution series, and prepare the mixed standard chromatogram for later use; Step 6, Chromatographic injection: Use Na2CO3 / NaHCO3 as the eluent, with a ratio of 2.6:1 to 3.4:

1. The eluent is passed through the column at a flow rate of 0.5 to 2.0 mL / min, and the column temperature is set to 30 to 39°C. The sample treated in Step 4 is subjected to chromatographic testing with an injection volume of 5 to 25 μL, and the test results are recorded. Step 7: Determine the content of anions; based on the mixed standard curve in Step 5 and the chromatographic test results in Step 6, determine the content of various anions in the electrolyte sample.

2. The test method according to claim 1, characterized in that, In step 1, the cation exchange resin is a strongly acidic cation exchange resin.

3. The test method according to claim 1, characterized in that, In step 2, the specific procedures for cleaning the resin layer with sodium hydroxide solution, hydrochloric acid solution, and deionized water are as follows: First, pass 4% NaOH, twice the volume of the resin, through the resin layer at a flow rate of 2-10 mL / min, exceeding the resin layer by 0.2 cm, and soak for 2-4 hours. Then, wash with hydrochloric acid at a flow rate of 10-15 mL / min until the effluent is neutral. Next, pass 4% HCl, twice the volume of the resin, through the resin layer exceeding the resin layer by 0.2 cm, and soak for 2-4 hours. Then, wash with deionized water until the effluent is neutral.

4. The test method according to claim 1, characterized in that, In step 4, the cation exchange resin ion exchange sample is passed through the packed resin column several times, and the column is washed multiple times with about 50 ml of ultrapure water. The sample is then placed in a volumetric flask and diluted to volume. Finally, 5 mL of the solution is filtered through a 0.45 μm filter membrane. The used cation exchange resin is then soaked in HCl (1+1) for 1-2 hours, with the HCl layer being 0.2 cm above the resin layer. The solution is then rinsed repeatedly with deionized water until the effluent is neutral and no chloride or sulfate ions are detected.

5. The test method according to claim 1, characterized in that, In step 6, a Metrosep A Supp 5 analytical column and a Metrosep RP 2 Guard protective column were used.

6. The test method according to claim 1, characterized in that, In step 6, the concentration of Na2CO3 in the rinsing solution is in the range of 2.8~3.6 mmol / L and NaHCO3 is in the range of 0.8~1.5 mmol / L.

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