Method for detecting chloride ions in sulfide

Abstract

The embodiment of the invention discloses a method for detecting chloride ions in sulfide, which comprises the following steps: oxidizing S < 2-> which is easy to interfere by using an oxidizing agent, dissolving the sulfide in a solvent in an inert atmosphere, adding the oxidizing agent to obtain a second solution, and heating the second solution in a water bath under an alkaline condition, the method has the advantages that the residual oxidizing agent is easily decomposed, then the third solution is evaporated and boiled under the acidic condition to form sulfur dioxide gas to escape, the interference of sulfur ions is effectively reduced, the detection error rate is obviously reduced, the repeatability is high, and the test precision is high.

Description

Technical Field

[0001] This application relates to the technical field of ion content testing, specifically to a method for detecting chloride ions in sulfides. Background Technology

[0002] Chloride ions are one of the key impurities affecting material performance, especially in battery materials (such as sulfides and sulfide-based solid electrolytes), where their content directly affects electrochemical performance and safety.

[0003] Currently, most related technologies use colorimetric methods to detect chloride ions in sulfides. A colorimetric reagent reacts with chloride ions to generate a colored compound, which is then quantitatively tested using a spectrophotometer.

[0004] However, in this method, sulfide ions (S...) 2- It will compete with the color developer for binding, leading to an unstable color development reaction. Summary of the Invention

[0005] This application provides a method for detecting chloride ions in sulfides, aiming to solve the problem of chloride ion (S) detection. 2- The problem of unstable colorimetric reactions caused by competition for binding with the colorimetric reagent.

[0006] This application provides a method for detecting chloride ions in sulfides, comprising the following steps: The sulfide was dissolved in a solvent under an inert atmosphere to obtain the first solution; An oxidizing agent is added to the first solution to obtain a second solution; The second solution was heated in a water bath under alkaline conditions to obtain the third solution; The third solution is acidified under acidic conditions, and then evaporated and boiled to obtain the fourth solution; The chloride ion content of the fourth solution was determined by colorimetric method.

[0007] Optionally, in some embodiments of this application, the sulfide includes at least one of lithium sulfide and sulfur-containing solid electrolyte; and / or The solvent includes one of water and dilute acid; and / or The inert atmosphere includes any one of argon, nitrogen, helium, and neon atmospheres; and / or The oxidant includes one of hydrogen peroxide and potassium permanganate.

[0008] Optionally, in some embodiments of this application, the dilute acid includes one of nitric acid, sulfuric acid, acetic acid, and phosphoric acid; and / or The concentration of the dilute acid is less than or equal to 50 wt%.

[0009] Optionally, in some embodiments of this application, the step of adding the oxidant to the first solution includes: Slowly add the oxidant to the first solution. Stop adding the oxidant when the temperature of the first solution rises. After cooling, continue adding the oxidant until there is no heat release after adding the oxidant, then stop adding the oxidant.

[0010] Optionally, in some embodiments of this application, the pH value of the alkaline condition ranges from 7 to 14; Preferably, the pH value of the alkaline conditions is in the range of 9 to 12.

[0011] Optionally, in some embodiments of this application, the temperature range of the water bath heating is 50°C. o C to 100 o C, the water bath heating time ranges from 0.5h to 5h; Preferably, the temperature range of the water bath heating is 60°C. o C to 90 o C, the water bath heating time ranges from 2h to 3h.

[0012] Optionally, in some embodiments of this application, the pH value of the acidic condition ranges from 0 to 7; Preferably, the pH value of the acidic condition is in the range of 3 to 5; The acidification reaction takes 0.5 min to 60 min; Preferably, the acidification reaction takes 5 to 10 minutes.

[0013] Optionally, in some embodiments of this application, the pH value of the acidic condition ranges from 2 to 6; Preferably, the pH value of the acidic condition is in the range of 3 to 5; The acidification reaction takes 0.5 min to 60 min; Preferably, the acidification reaction takes 5 to 10 minutes.

[0014] Optionally, in some embodiments of this application, the detection method further includes: A dispersant was added to the fourth solution, and the chloride ion content was determined by colorimetric method. The dispersant includes at least one of ethylene glycol, glycerol, and anhydrous ethanol.

[0015] Optionally, in some embodiments of this application, the fourth solution is left for more than a week, and the change rate of the chloride ion content is less than 2%.

[0016] This application embodiment utilizes an oxidant to target easily interfered S 2- Oxidation is performed by dissolving the sulfide in a solvent under an inert atmosphere and adding an oxidant to obtain a second solution. The second solution is then heated in a water bath under alkaline conditions, which helps to decompose the residual oxidant. The third solution is then evaporated and boiled under acidic conditions to form sulfur dioxide gas, which effectively reduces the interference of sulfide ions, thereby significantly reducing the detection error rate, and has high repeatability and high testing accuracy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the detection method of some embodiments of this application; Figure 2 This is a schematic diagram of the initial state of Embodiment 1 of this application; Figure 3 This is a schematic diagram of the oxidation state of the second solution obtained after oxidation in Example 1 of this application; Figure 4 This is a schematic diagram of the state before testing the chloride ion content in Example 1 of this application. Detailed Implementation

[0019] The technical solutions described below in conjunction with the embodiments of this application will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Currently, there are various methods for detecting chloride ions in sulfides, but all of them have certain limitations: 1. Colorimetric method (e.g., CN113640404A): The method involves reacting a chromogenic reagent with chloride ions to form a colored compound, which is then quantified using a spectrophotometer. However, this method requires the presence of sulfide ions (S...). 2- It will compete with the colorimetric reagent for binding, resulting in unstable colorimetric reactions. It requires a complex pretreatment process to remove sulfide interference, and has a large detection error for low concentrations of chloride ions.

[0021] 2. High-performance liquid chromatography (e.g., CN113804860A): After sample pretreatment, chloride ions are separated by a chromatographic column and determined using a conductivity detector. This method offers high precision but requires expensive, large-scale instruments (such as chromatographic columns and conductivity detectors), resulting in high costs and complex procedures.

[0022] 3. Electrochemical sensor method (e.g., CN114113336A): Based on nanomaterial-modified electrodes, this sensor generates a current signal through the specific reaction of chloride ions with the electrode surface for detection. However, the electrode is easily corroded in sulfide environments, leading to poor long-term stability and decreased sensitivity, requiring frequent calibration or electrode replacement. Furthermore, the detection results are easily affected by ambient temperature and humidity, limiting its field application.

[0023] In view of this, the embodiments of this application provide a chloride ion detection method that can effectively eliminate sulfide interference and is suitable for conventional laboratories.

[0024] According to a first aspect of the embodiments of this application, a method for detecting chloride ions in sulfides is provided, please refer to... Figure 1 It includes the following steps: S100. Dissolve the sulfide in a solvent under an inert atmosphere to obtain the first solution; S200. Add an oxidizing agent to the first solution to obtain the second solution; S300. The second solution is heated in a water bath under alkaline conditions to obtain the third solution; S400. The third solution is acidified under acidic conditions, and then evaporated and boiled to obtain the fourth solution. S500, the chloride ion content of the fourth solution was determined by colorimetric method.

[0025] By adopting the above-described scheme, the embodiments of this application utilize oxidants to target easily interfered S 2- Oxidation is performed by dissolving the sulfide in a solvent under an inert atmosphere and adding an oxidant to obtain a second solution. The second solution is then heated in a water bath under alkaline conditions, which helps to decompose the residual oxidant. The third solution is then evaporated and boiled under acidic conditions to form sulfur dioxide gas, which effectively reduces the interference of sulfide ions and thus significantly reduces the detection error rate, resulting in high testing accuracy.

[0026] In this embodiment, if step S100 is performed in a non-inert environment, sulfides can continuously generate hydrogen sulfide, leading to lower detection results and posing certain safety hazards. Step S200, which involves adding an oxidant, converts unstable sulfide ions into stable sulfate ions, helping to reduce detection requirements; furthermore, it reduces the interference of sulfide ions on chloride ions.

[0027] In some embodiments of this application, the sulfide includes at least one of lithium sulfide and sulfur-containing solid electrolyte.

[0028] By adopting the above scheme, lithium sulfide and sulfur-containing solid electrolytes can be used as battery materials. These materials are extremely sensitive to moisture and air, and will react violently to release hydrogen sulfide gas during conventional water dissolution processes. This application utilizes an oxidant under an inert atmosphere to oxidize the sulfide, removing the sulfur (S) from the sulfur. 2- The gradual and controllable oxidation to sulfate ions helps to eliminate S. 2- This ensures that no hydrogen sulfide is generated during subsequent processing.

[0029] In some embodiments of this application, the solvent includes at least one of water and dilute acid.

[0030] By employing the above method, lithium sulfide undergoes a hydrolysis reaction upon contact with water, slowly releasing hydrogen sulfide and simultaneously generating lithium hydroxide, making the solution alkaline. Adding an oxidant to this alkaline environment allows for the stable oxidization of sulfur. 2- This avoids the instantaneous generation of large amounts of hydrogen sulfide in an acidic environment. Dilute acids are suitable for decomposing sulfides that have poor solubility. Dilute acids can decompose sulfides more quickly and thoroughly, allowing chloride ions to be fully released into the solution, or when rapid detection is required, meaning that the dissolution and reaction efficiency is higher and the speed is faster.

[0031] In some embodiments of this application, the dilute acid includes one of nitric acid, sulfuric acid, acetic acid, and phosphoric acid.

[0032] By adopting the above scheme, different types of dilute acids can be selected according to different needs. For example, nitric acid is both an acid and a strong oxidizing agent; its synergistic effect with hydrogen peroxide greatly accelerates the reaction of sulfur dioxide. 2- To SO4 2- The conversion makes the pretreatment faster and more thorough; sulfuric acid has a high boiling point, which can effectively remove volatile gases and promote solution concentration in the subsequent evaporation and boiling steps; acetic acid can provide a relatively mild acidic environment and has a certain buffering capacity, which can keep the pH relatively stable in the early stage of the reaction; phosphate has a certain complexing ability, which can complex certain metal cations in the solution and prevent these metal ions from hydrolyzing and producing precipitation, thus affecting the detection results of ions.

[0033] In some embodiments of this application, the concentration of the dilute acid is less than or equal to 50 wt%. For example, the concentration of the dilute acid can be 5 wt%, 10 wt%, 12.5 wt%, 15 wt%, 17.5 wt%, 20 wt%, 22.5 wt%, 25 wt%, 27.5 wt%, 30 wt%, 32.5 wt%, 35 wt%, 37.5 wt%, 40 wt%, 42.5 wt%, 45 wt%, 47.5 wt%, 50 wt%, or any value between two adjacent values.

[0034] In some embodiments of this application, the inert atmosphere includes any one of argon atmosphere, nitrogen atmosphere, helium atmosphere, and neon atmosphere.

[0035] By employing the above method, the inert atmosphere primarily removes air, especially oxygen and carbon dioxide, effectively preventing sample oxidation, and thus avoiding sulfur dioxide buildup. 2- It is oxidized into sulfite, thiosulfate, or even elemental sulfur. Furthermore, if not removed promptly, carbon dioxide in the air will react with alkaline solutions to form carbonate ions, which in turn react with silver ions to form silver carbonate precipitate, severely interfering with the detection results of chloride ions.

[0036] In some embodiments of this application, the oxidant includes one of hydrogen peroxide and potassium permanganate.

[0037] By adopting the above method, hydrogen peroxide and potassium permanganate are both commonly used oxidants in the laboratory, and hydrogen peroxide does not introduce any additional metal or halide ions. Excess hydrogen peroxide can be removed by subsequent heating and decomposition.

[0038] In some embodiments of this application, the step of adding an oxidizing agent to the first solution includes: Add an oxidant to the first solution. Stop adding the oxidant when the temperature of the first solution rises. After cooling, continue adding the oxidant until there is no heat release after adding the oxidant, then stop adding the oxidant.

[0039] By adopting the above scheme, since the oxidation of sulfides is an exothermic reaction, this step mainly prevents the solution from splashing due to rapid temperature changes, which would lead to lower results. It controls the redox reaction rate and avoids safety hazards.

[0040] In some embodiments of this application, the pH value of the alkaline condition ranges from 7 to 14. Further, the pH value of the alkaline condition ranges from 9 to 12. Exemplarily, the pH value of the alkaline condition can be 9, 9.5, 10, 10.5, 11, 11.5, 12, or any value between two adjacent values ​​mentioned above.

[0041] By adopting the above scheme and adjusting the appropriate pH range, it is helpful to react with excess oxidant, ensure the complete decomposition and removal of oxidant, and effectively prevent the formation of precipitates due to residual oxidant reaction, which would affect the test results.

[0042] In some embodiments of this application, the temperature range for water bath heating is 50°C. o C to 100 o C. The water bath heating time ranges from 0.5 hours to 5 hours. Furthermore, the water bath heating temperature ranges from 60 degrees Celsius. o C to 90 oC. The water bath heating time ranges from 2 to 3 hours. For example, the water bath heating temperature can be 60°C. o C, 65 o C, 70 o C, 75 o C, 80 o C, 85 o C, 90 o C and any value between the two adjacent values ​​mentioned above.

[0043] By employing the above method, under alkaline conditions, excess hydrogen peroxide will decompose into water and oxygen. Water bath heating can accelerate this decomposition reaction, helping to completely remove oxidants of different dosages and concentrations within a certain time range. Under alkaline heating conditions, the intermediate products in the oxidation process will continue to undergo disproportionation reactions, thereby converting into inert sulfate ions, ensuring that this conversion reaction is more complete.

[0044] In some embodiments of this application, the pH value of the acidic condition ranges from 2 to 6. Further, the pH value of the acidic condition ranges from 3 to 5. Exemplarily, the pH value of the acidic condition can be 3, 3.5, 4, 4.5, 5, or any value between two adjacent values ​​mentioned above.

[0045] By adopting the above scheme, the acidic pH can ensure the removal of sulfite ions. This method is universal and reliable, and the pH range of 3-5 can create the best reaction conditions for silver chloride, achieving complete precipitation and thus ensuring the accuracy of the measurement.

[0046] In some embodiments of this application, the acidification reaction time is from 0.5 min to 60 min. Further, the acidification reaction time is from 5 min to 10 min. Exemplarily, the acidification reaction time can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any value between two adjacent values ​​mentioned above.

[0047] By employing the above method, once the solution is adjusted to acidity, sulfite ions immediately react with hydrogen ions to form sulfurous acid, which rapidly decomposes and releases sulfur dioxide gas. Providing a suitable acidification time helps the sulfur dioxide gas to fully dissolve and diffuse in the solution. However, if the acidification reaction is too prolonged, it may trigger unnecessary side reactions, forming precipitates and affecting the accuracy of the detection results.

[0048] In some embodiments of this application, the evaporation amount of the third solution in the boiling reaction is 10 wt% to 60 wt%. Further, the evaporation amount of the third solution in the boiling reaction is 30 wt% to 50 wt%.

[0049] By employing the above method, the boiling reaction helps promote the escape of gas from the solution, which in turn helps to carry away most of the residual sulfur-containing products, thus ensuring the removal of interfering substances. The third solution, with an evaporation rate of 30wt% to 50wt%, achieves effective concentration, significantly improving detection sensitivity, while also avoiding the precipitation of other salts, thereby ensuring the purity of the reaction system.

[0050] In some embodiments of this application, the detection method further includes: A dispersant was added to the fourth solution, and the chloride ion content was determined by colorimetric method. The dispersant includes at least one of ethylene glycol, glycerol, and anhydrous ethanol.

[0051] By adopting the above scheme, the dispersant can increase the viscosity of the solution, slow down the Brownian motion and anisotropic collisions of the precipitated particles, effectively prevent the occurrence of agglomeration, and further hinder the particles from approaching each other through intermolecular interactions, ultimately forming a reaction system with uniform particles, stable distribution, and constant stability over a long period of time.

[0052] In some embodiments of this application, the fourth solution is left for more than a week, and the rate of change in chloride ion content is less than 2%.

[0053] By adopting the above scheme, the detection method of this application embodiment has long-term storage stability, can be stored for more than a week for testing, and has high detection accuracy.

[0054] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0055] Example 1 Lithium sulfide was dissolved in water under a nitrogen atmosphere to obtain the first solution; Slowly add 30% hydrogen peroxide to the first solution. If the temperature of the first solution rises, stop adding hydrogen peroxide. After cooling, continue adding hydrogen peroxide until there is no more exothermic phenomenon, then stop adding hydrogen peroxide to obtain the second solution. The second solution was heated in a water bath at pH 10 for 3 hours to obtain the third solution; The third solution was acidified at pH 3, and after 40 wt% of the third solution was evaporated, the fourth solution was obtained. After adding 1 mL of ethylene glycol to the fourth solution, the chloride ion content was determined by colorimetric method.

[0056] Examples 2 to 5 Except for adjusting the pH of the water bath as shown in Table 1, everything else remains the same as in Example 1.

[0057] Table 1

[0058] Example 6 The difference from Example 1 lies in the water bath heating time. In this example, the water bath heating time is 2 hours, while the rest remains the same as in Example 1.

[0059] Example 7 The difference from Example 1 is that the evaporation amount of the acidification reaction is 60 wt% of the third solution, while the rest is the same as in Example 1.

[0060] Example 8 The difference from Example 1 is the absence of a dispersant; otherwise, it remains the same as Example 1.

[0061] Comparative Example 1 The difference from Example 1 is that the water bath heating process is omitted under alkaline conditions, while the rest of the steps are the same as in Example 1.

[0062] Comparative Example 2 The difference from Example 1 is that the acidification, evaporation and boiling process is omitted, while the rest of the steps are the same as in Example 1.

[0063] Chloride ion content test: The chloride ion content of the samples from the examples and comparative examples was tested using the turbidimetric method according to GB / T 5750.5-2023.

[0064] The test results are shown in Table 1. Table 1

[0065] Comparing Examples 1-8 with Comparative Examples 1-2, Examples 1-8 employed water bath heating under alkaline conditions and acidification evaporation and boiling under acidic conditions, while Comparative Example 1 lacked water bath heating under alkaline conditions, and Comparative Example 2 lacked acidification evaporation and boiling under acidic conditions. As shown in Table 1, the use of oxidants to treat easily interfered S... 2- Oxidation is performed by dissolving the sulfide in a solvent under an inert atmosphere and adding an oxidant to obtain a second solution. The second solution is then heated in a water bath under alkaline conditions, which helps to decompose the residual oxidant. The third solution is then evaporated and boiled under acidic conditions to release sulfur dioxide gas, which effectively reduces the interference of sulfide ions and thus significantly reduces the detection error rate, resulting in high test accuracy and high repeatability, making it suitable for chloride ion detection in routine laboratories.

[0066] Figure 2This is a schematic diagram of the initial state of the solution before detection in Example 1 of this application. Figure 3 This is a schematic diagram of the oxidation state of the second solution obtained after oxidation in Example 1. Figure 4 This is a schematic diagram of the final state of the solution during the test in Example 1. Figure 2-4 It is known that the solution obtained by heating in a water bath under alkaline conditions and evaporating and boiling under acidic conditions is clear and transparent with few impurity ions, which helps to reduce interference with chloride ions.

[0067] Compared to Examples 1 and 6, the shortened water bath heating time led to higher test results, indicating interference from impurities. The 24-hour test results were relatively stable. Compared to Examples 1 and 7, Example 7 had excessive evaporation, resulting in chloride ion volatilization and lower test results. Based on Examples 1 and 8, the lack of a dispersant negatively impacted solution consistency, leading to unstable test results.

[0068] The above provides a detailed description of a method for detecting chloride ions in sulfides provided by the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and its core ideas. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for detecting chloride ions in sulfides, characterized in that, Includes the following steps: The sulfide was dissolved in a solvent under an inert atmosphere to obtain the first solution; An oxidizing agent is added to the first solution to obtain a second solution; The second solution was heated in a water bath under alkaline conditions to obtain the third solution; The third solution is acidified under acidic conditions, and then evaporated and boiled to obtain the fourth solution; The chloride ion content of the fourth solution was determined by colorimetric method.

2. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, The sulfide includes at least one of lithium sulfide and sulfur-containing solid electrolyte; and / or The solvent includes one of water and dilute acid; and / or The inert atmosphere includes any one of argon, nitrogen, helium, and neon atmospheres; and / or The oxidant includes one of hydrogen peroxide and potassium permanganate.

3. The method for detecting chloride ions in sulfides according to claim 2, characterized in that, The dilute acid includes one of nitric acid, sulfuric acid, acetic acid, and phosphoric acid; and / or The concentration of the dilute acid is less than or equal to 50 wt%.

4. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, The step of adding the oxidant to the first solution includes: Add an oxidant to the first solution. Stop adding the oxidant when the temperature of the first solution rises. After cooling, continue adding the oxidant until there is no heat release after adding the oxidant, then stop adding the oxidant.

5. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, The pH value of the alkaline conditions ranges from 7 to 14; Preferably, the pH value of the alkaline conditions is in the range of 9 to 12.

6. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, The temperature range for the water bath heating is 50°C. o C to 100 o C, the water bath heating time ranges from 0.5h to 5h; Preferably, the temperature range of the water bath heating is 60°C. o C to 90 o C, the water bath heating time ranges from 2h to 3h.

7. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, The pH value of the acidic conditions is in the range of 2 to 6; Preferably, the pH value of the acidic condition is in the range of 3 to 5; The acidification reaction takes 0.5 min to 60 min; Preferably, the acidification reaction takes 5 to 10 minutes.

8. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, The evaporation and boiling process involves a third solution with an evaporation rate of 10 wt% to 60 wt%. Preferably, the evaporation amount of the third solution is 30wt% to 50wt%.

9. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, The detection method further includes: A dispersant was added to the fourth solution, and the chloride ion content was determined by colorimetric method. The dispersant includes at least one of ethylene glycol, glycerol, and anhydrous ethanol.

10. The method for detecting chloride ions in sulfides according to claim 1, characterized in that, When the fourth solution is left for more than a week, the change rate of the chloride ion content is less than 2%.

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