Method for detecting chloride ions in electrolyte of aluminum electrolytic capacitor

Abstract

The invention discloses a method for detecting chloride ions in an electrolyte of an aluminum electrolytic capacitor. The method comprises the following steps: 1) preparing a control group; the method comprises the following steps: (1) putting 1 part by volume of a chloride standard solution with the weight concentration of 1-5ppm into a colorimetric tube, and adding 10 parts by volume of deionized water into the colorimetric tube; (2) adding 10-20 parts by volume of absolute ethyl alcohol into the colorimetric tube in the step (1), uniformly shaking, and then adding 3-10 parts by volume of nitric acid with the concentration of 3-5mol / L; (3) adding 1-5 parts by volume of AgNO3 solution into the solution in the step (2); obtaining a standard tube; 2) pretreating the electrolyte to be detected to obtain liquid to be detected; 3) taking 1 part by volume of the to-be-detected liquid in the step 2), and performing the steps 1)-3) to obtain a sample tube, and 4) comparing the sample tube in the step 3) with the standard tube in the step 1). The detection method provided by the invention can remove the interference of the macromolecular acid on the test, so that whether the chloride ions in the electrolyte containing the macromolecular acid exceed the standard or not can be detected.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of aluminum electrolytic capacitor electrolyte detection method, more particularly to a kind of aluminum electrolytic capacitor electrolyte chloride ion detection method. BACKGROUND

[0002] Aluminum electrolytic capacitor electrolyte must detect chloride ion by batch, since chloride ion has great influence on product life.Chloride ion is the core of the destruction of aluminum electrolytic capacitor, and chloride ion can corrode anodic aluminum oxide, and the specific process is as follows: Cl - Reaction occurs with aluminum oxide film, generating soluble aluminum chloride, resulting in local thinning or perforation of the oxide film, reducing dielectric strength and increasing leakage current.The reaction is as follows:

[0003] Under the action of electric field, electrochemical corrosion will accelerate.Under the action of electric field, Cl - Adsorbed at the defect of the oxide film, causing pitting and accelerating the anodic dissolution of aluminum foil, ultimately leading to capacitor short circuit or open circuit failure.

[0004] At the same time, chloride ion also cooperates with ammonium salt to destroy; the commonly used organic carboxylic acid ammonium salt in electrolyte, such as ammonium formate; may dissociate ammonium ion NH4 + And Cl - Combined to form ammonium chloride, which decomposes into HCl under the action of high temperature and water, further exacerbating corrosion.

[0005] However, some models of electrolyte may interfere with the detection of chloride ions during the detection process; mainly due to the presence of macromolecular organic acids in the electrolyte; resulting in inaccurate results; a new testing scheme is needed to solve this phenomenon. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a detection method for chloride ions in aluminum electrolytic capacitor electrolyte that excludes interference.

[0007] To solve the above technical problems, the technical solution of the present application is as follows: a detection method for chloride ions in aluminum electrolytic capacitor electrolyte, comprising the following steps: 1) Configure a control group; ① Take 1 volume part of a chloride standard solution with a weight concentration of 1 ppm-5 ppm and place it in a colorimetric tube, add 10 volumes of deionized water to the colorimetric tube, and mix well; ② Add 10-20 volumes of anhydrous ethanol to the colorimetric tube of step ① and shake well, then add 3-10 volumes of concentrated nitric acid with a concentration of 3-5 mol / L, and shake well; ③ Add 1-5 volume parts of AgNO3 solution to the solution of step ②, and the weight concentration of the AgNO3 solution is between 1%-3%; Finally, dilute with deionized water to the preset scale line, shake well and stand still; obtain the standard tube; 2) Pretreat the electrolyte to be tested to remove macromolecular acid in the electrolyte, and obtain the liquid to be tested; 3) Take 1 volume part of the liquid to be tested in step 2) to perform steps 1) ①-③; obtain the sample tube; 4) Compare the sample tube in step 3) with the standard tube in step 1), if the turbidity of the sample tube is greater than that of the standard tube, it indicates that the chloride ion in the sample tube is greater than that in the sample tube; if the turbidity of the sample tube is less than that of the standard tube, it indicates that the chloride ion in the sample tube is less than that in the sample tube.

[0008] The above-mentioned detection method of the chloride ion in the electrolyte of the aluminum electrolytic capacitor is preferably treated by acidification-filtration in step 2); specifically comprising the following steps: I Add dilute nitric acid to the electrolyte to be tested, so that the pH value of the electrolyte to be tested is between 2-3; II Stand still or centrifuge; III Filter with a filter membrane, remove macromolecular acid, collect the filtrate, and obtain the liquid to be tested.

[0009] The above-mentioned detection method of the chloride ion in the electrolyte of the aluminum electrolytic capacitor is preferably treated by acidification-filtration in step 2); specifically comprising the following steps: 2- The anions in the electrolyte to be tested include one or more of organic acid radicals and SO4

[0010] The above-mentioned detection method of the chloride ion in the electrolyte of the aluminum electrolytic capacitor is preferably treated by acidification-filtration in step 2); specifically comprising the following steps:

[0011] Compared with the prior art, the advantages of the present application are that the detection method of the chloride ion in the electrolyte of the aluminum electrolytic capacitor can remove the interference of macromolecular acid on the test, so that the test method of the present application can detect whether the chloride ion in the electrolyte containing macromolecular acid is over standard. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The figure is a comparison between the sample tube and the blank tube.

[0013] Figure 2 The figure is a comparison between the standard tube and the blank tube. DETAILED DESCRIPTION

[0014] For the purpose of understanding the present application, the present application will be described in further detail below with reference to preferred embodiments. However, it is to be understood that the scope of the present application is not limited to the specific embodiments described herein below.

[0015] It should be particularly noted that when an element is described as being "fixed, secured, connected or communicated to" another element, it can be directly fixed, secured, connected or communicated to the other element, or indirectly fixed, secured, connected or communicated to the other element through other intermediate connecting elements.

[0016] Unless otherwise defined, all the technical terms used below have the same meanings as commonly understood by one skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present application.

[0017] Embodiment 1 A method for detecting chloride ions in electrolyte of an aluminum electrolytic capacitor, characterized in that it comprises the following steps: 1) configuring a control group; ① Take 1 ml of a chloride standard solution with a weight concentration of 1 ppm and place it in a colorimetric tube, add 10 ml of deionized water to the colorimetric tube, and mix well; ② Add 15 ml of anhydrous ethanol to the colorimetric tube of step ① and shake well, then add 5 ml of concentrated nitric acid with a concentration of 4 mol / L and shake well; ③ Add 2 ml of AgNO3 solution to the solution of step ②, and the weight concentration of the AgNO3 solution is 2%; Finally, dilute with deionized water to the 50 ml scale, shake well and stand; obtain the standard tube.

[0018] 2) Pretreat the electrolyte to be tested to remove macromolecular acids in the electrolyte, and obtain the test liquid.

[0019] Specifically, it comprises the following steps: I Add dilute nitric acid to the electrolyte to be tested so that the pH value of the electrolyte to be tested is between 2 and 3; II Stand or centrifuge; III Filter with a filter membrane to remove macromolecular acids, collect the filtrate, and obtain the test liquid.

[0020] 3) Take 1 ml of the test liquid of step 2) and perform steps ①-③ of step 1); obtain the sample tube. The difference between step 3) and step 1) is only that 1 ml of the test liquid is used instead of 1 ml of the chloride with a weight concentration of 1 ppm in step 1).

[0021] 4) Compare the sample tube with the standard tube in step 1), and compare the turbidity of the sample tube and the standard tube after shaking. If the turbidity of the sample tube is greater than that of the standard tube, it means that the chloride ion in the sample tube is greater than that in the sample tube; if the turbidity of the sample tube is less than that of the standard tube, it means that the chloride ion in the sample tube is less than that in the sample tube.

[0022] In this embodiment, a blank tube is set up, 1 ml of deionized water is taken, and steps 1) ①-③ are performed; a blank tube is obtained. The blank tube is set up and differs from step 1) only in that 1 ml of deionized water is used instead of 1 ml of 1 ppm weight concentration of chloride in step 1). The blank tube can verify whether the standard reagent is accurate or whether the deionized water contains chloride ions.

[0023] As shown in Figure 1 and Figure 2 , in this embodiment, the turbidity of the standard tube is greater than that of the sample tube, indicating that the concentration of chloride ions in the tested electrolyte is less than 1 ppm; while the blank tube is almost transparent, indicating that the deionized water does not contain chloride ions.

[0024] Example 2 In this embodiment, anion exchange resin is used to adsorb organic acid radicals in the anion of the electrolyte to be tested in step 2), and the anion includes organic acid radicals, Cl - , SO4 2- , etc. Then deionized water is used to elute the anion exchange resin, and a relatively pure Cl - solution is obtained after elution, thereby obtaining a tested liquid from which organic acid radicals are removed. In this embodiment, the anion exchange resin will adsorb part of the Cl - , so the anion exchange resin needs to be eluted, but when eluting, the flow rate of deionized water should be very slow to prevent the organic acid radicals adsorbed on the anion exchange resin from being washed down. Generally, the flow rate of deionized water is 2-5 cm / h or 0.5-1 BV / h, and a Φ1 cm column is used.

[0025] In this embodiment, the functional group of the anion exchange resin is weakly basic; and the adsorption order of the anion is generally: OH - > SO4 2- > organic acid radical > Cl - ≈ HCO3 - . It can be seen that the adsorption of Cl ⁻ by the weakly basic anion exchange resin is late, and it is more likely to remain in the solution; this is because the functional group (primary amine / secondary amine) is less protonated at near neutral pH, reducing the electrostatic attraction of Cl⁻.

[0026] In this embodiment, the retention of Cl⁻ in the solution can also be enhanced by the following measures: 1. Pretreatment to remove interfering ions: If the feed contains high concentrations of SO4 2- or PO4 ³⁻ , first use a strong acid cation resin (such as 001x7) to remove multivalent cations (such as Ca 2+ , Al 3+ ) to reduce competition with Cl - .

[0027] 2. Add protective colloid: Add 1% dextrin to the feed to coat Cl - and reduce its contact with active sites on the resin.

[0028] 3. Avoid resin dehydration: Soak the resin in 10% NaCl solution when storing to prevent Cl - passive adsorption caused by drying shrinkage.

Claims

1. A method for detecting chloride ions in an aluminum electrolytic capacitor electrolyte, characterized in that: The following steps are involved: 1) Configure a control group; ① Take 1 part by volume of a chloride standard solution with a weight concentration of 1ppm-5ppm and place it in a colorimetric tube. Add 10 parts by volume of deionized water to the colorimetric tube and mix well. ② Add 10-20 parts by volume of anhydrous ethanol to the colorimetric tube in step ① and shake well, then add 3-10 parts by volume of 3-5 mol / L nitric acid and shake well; ③ Add 1-5 parts by volume of AgNO3 solution to the solution in step ②, wherein the weight concentration of the AgNO3 solution is between 1% and 3%; Finally, dilute with deionized water to the preset scale line, shake well and let it stand; Get a standard tube; 2) Pre-treating the electrolyte to be tested to remove the macromolecular acid in the electrolyte to obtain the liquid to be tested; 3) Take 1 volume of the liquid to be tested from step 2) and carry out steps ①-③ in step 1) to obtain a sample tube; 4) Compare the sample tube from step 3) with the standard tube from step 1). If the turbidity of the sample tube is greater than that of the standard tube, it means that the chloride ion content in the sample tube is greater than that in the standard tube; if the turbidity of the sample tube is less than that of the standard tube, it means that the chloride ion content in the sample tube is less than that in the standard tube.

2. The method for detecting chloride ions in an aluminum electrolytic capacitor electrolyte according to claim 1, wherein: In the step 2), the acidification-filtration method is used for treatment; Specifically include the following steps:

1. Add dilute nitric acid to the electrolyte to be tested so that the pH value of the electrolyte to be tested is between 2 and 3; II. Let stand or centrifuge; III. Filter through a filter membrane to remove macromolecular acids, collect the filtrate, and obtain the liquid to be tested.

3. The method for detecting chloride ions in an aluminum electrolytic capacitor electrolyte according to claim 1, wherein: In the step 2), anion exchange resin is used to adsorb anions in the electrolyte to be tested, and the anions include organic acid radicals and SO4 2- One or more of the above; and then eluting the anion exchange resin with deionized water to obtain a test liquid from which the organic acid radicals are removed.

4. The method for detecting chloride ions in an aluminum electrolytic capacitor electrolyte according to claim 1, wherein: When performing the comparison in step 4), the sample tube and the standard tube are shaken thoroughly before comparison.

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