Method and device for testing concentration of chemical detergent in citric acid system

Abstract

The invention relates to the field of decontaminant concentration testing, in particular to a citric acid system chemical decontaminant concentration testing method and a citric acid system chemical decontaminant concentration testing device.The citric acid system chemical decontaminant concentration testing method comprises the steps that iron ions in a decontaminant are removed, and the total concentration of citric acid in the decontaminant is tested; testing the concentration of citric acid complexed with iron ions in the detergent; subtracting the concentration of the citric acid complexed with the iron ions from the total concentration of the citric acid in the decontaminant to obtain the concentration of the decontaminant; the influence of iron ion complexing citric acid on the test result is eliminated, so that the measured citric acid concentration is closer to the actual effective concentration of the detergent, the decontamination process is guided, and the decontamination effect is ensured; meanwhile, since the iron ions in the detergent are removed before testing, the influence of the existence of the iron ions on acid-base neutralization is avoided, so that the measured dosage of the alkaline solution is closer to the actual dosage of the alkaline solution neutralized by citric acid, and the testing accuracy is further improved.

Description

Technical Field

[0001] The present invention relates to the field of detergent concentration testing, and in particular to a method and device for testing the concentration of a chemical detergent in a citric acid system. Background Art

[0002] During the maintenance of a pressurized water reactor nuclear power plant, it is decided whether to carry out chemical decontamination work according to the radioactive level of the equipment to be maintained. At present, oxalic acid is commonly used in widely used chemical detergents, but the corrosion of such detergents is relatively strong, which is not conducive to the corrosion control of the impeller of the martensitic stainless steel pump in the primary loop. The corrosivity of citric acid is weaker than that of oxalic acid, which can avoid the corrosion risk of martensitic stainless steel materials during chemical decontamination. In order to reduce the amount of waste liquid generated during chemical decontamination, low-concentration chemical detergents are generally used, with a concentration less than 2%, or even less than 0.5%. The concentration of the detergent has a significant impact on the decontamination effect. Therefore, it is necessary to monitor the concentration of the detergent during chemical decontamination and take necessary intervention measures based on the concentration analysis results.

[0003] In the existing test methods, the influence of the presence of iron ions on the ability of the chemical detergent in the citric acid system is not considered. Citric acid is prone to complex with iron ions and reduce the decontamination ability, resulting in the actual effective concentration of the chemical detergent in the citric acid system being relatively low compared with the test results, and the actual decontamination effect being worse than the test theoretical effect. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is: the problem that the actual effective concentration of the chemical detergent in the citric acid system is relatively low compared with the test results due to the influence of iron ions.

[0005] The above technical problem is solved by the following technical solution: The present invention provides a method for testing the concentration of a chemical detergent in a citric acid system, including removing iron ions from the detergent and testing the total concentration of citric acid in the detergent; testing the concentration of citric acid complexed with iron ions in the detergent; subtracting the concentration of citric acid complexed with iron ions from the total concentration of citric acid in the detergent to obtain the concentration of the detergent.

[0006] In a preferred embodiment of the method for testing the concentration of the chemical detergent in the citric acid system of the present invention: Take a quantitative original solution of the detergent and dilute it, remove the iron ions therein, then dropwise add an alkaline standard solution and detect the pH value. When the pH value reaches 7, stop titration and record the consumption of the alkaline standard solution. Calculate the total concentration of citric acid in the detergent based on the consumption of the alkaline standard solution.

[0007] In a preferred embodiment of the method for testing the concentration of the chemical detergent in the citric acid system of the present invention: Take an exchange column filled with cation resin, and slowly flow the diluted detergent through the exchange column to remove the iron ions in the detergent.

[0008] In a preferred embodiment of the method for testing the concentration of the chemical detergent in the citric acid system according to the present invention: the stock solution of the detergent is diluted 10 times, the alkaline standard solution is the NaOH standard solution, and the concentration of the NaOH standard solution is 0.05 mol / L or 0.1 mol / L.

[0009] In a preferred embodiment of the method for testing the concentration of the chemical detergent in the citric acid system according to the present invention: take a quantitative stock solution of the detergent, inject it into the pretreatment solution, and observe whether the stock solution of the detergent shows a blood-red color. If no blood-red color appears, there is no iron ion in the stock solution of the detergent; if a blood-red color appears, then dilute the stock solution of the detergent, then add an appropriate amount of sulfosalicylic acid solution, slowly dropwise add the EDTA standard solution, and the titration end point is when the diluted detergent changes from purple to light yellow. Record the consumption of the EDTA standard solution, calculate the content of iron ions in the detergent according to the consumption of the EDTA standard solution, and then calculate the concentration of citric acid complexed with iron ions in the remover.

[0010] In a preferred embodiment of the method for testing the concentration of the chemical detergent in the citric acid system according to the present invention: the pretreatment solution includes a potassium thiocyanate solution and an ammonium persulfate solution, wherein the concentration of the potassium thiocyanate solution is 40%, and the concentration of the ammonium persulfate solution is 10%.

[0011] In a preferred embodiment of the method for testing the concentration of the chemical detergent in the citric acid system according to the present invention: the stock solution of the detergent is diluted 10 times, and the concentration of the EDTA standard solution is 0.05 mol / L or 0.1 mol / L.

[0012] In a preferred embodiment of the method for testing the concentration of the chemical detergent in the citric acid system according to the present invention: demineralized water is used to dilute the detergent.

[0013] The present invention also provides a device for testing the concentration of the chemical detergent in the citric acid system, which is used for the above method for testing the concentration of the chemical detergent in the citric acid system, including a titration cell, wherein a stirrer, a pH sensor and a color recognition sensor are arranged in the titration cell; a pretreatment agent adding pipeline, which includes a pretreatment agent bottle, and the pretreatment agent bottle is connected to the titration cell through a pipeline; a titrant adding pipeline, which includes a titrant bottle, and the titrant bottle is connected to the titration cell through a pipeline; a water replenishing pipeline, which includes a pure water tank, and the pure water tank is connected to the titration cell through a pipeline; a sample adding pipeline, which includes a sample bottle, and the sample bottle is connected to the titration cell through a pipeline; a waste liquid discharging pipeline, which includes a waste liquid tank, and the waste liquid tank is connected to the titration cell through a pipeline.

[0014] In a preferred embodiment of the citric acid system chemical decontaminant concentration testing device of the present invention: peristaltic pumps are provided on the pipelines between the titration cell and the pretreatment agent bottle, the pure water tank, and the waste liquid tank; injection pumps are provided on the pipelines between the titration cell and the titrant bottle and the sample bottle.

[0015] The beneficial effects of the present invention are as follows: by detecting the total concentration of citric acid after removing iron ions, and then separately testing the concentration of citric acid complexed with iron ions, the effective concentration of the decontaminant is obtained by subtracting the concentration of citric acid complexed with iron ions from the total detected concentration of citric acid. This eliminates the influence of iron ion-complexed citric acid on the test results, making the measured citric acid concentration closer to the actual effective concentration of the decontaminant, which is beneficial for guiding the decontamination process and ensuring the decontamination effect. At the same time, since iron ions in the decontaminant have been removed before testing, the influence of the presence of iron ions on acid-base neutralization is avoided, making the amount of alkaline solution measured closer to the actual amount of alkaline solution that neutralizes citric acid, further improving the test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present invention and do not limit the present invention. Among them:

[0017] Figure 1 shows a schematic structural diagram of a citric acid system chemical decontaminant concentration testing device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below in conjunction with the specific embodiments and the drawings.

[0019] The terms used in the present invention are those general terms that are currently widely used in the art in consideration of the functions of the present invention. However, these terms may change according to the intentions of those of ordinary skill in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in this case, their detailed meanings will be described in the detailed description of the present invention. Therefore, the terms used in the specification should not be understood as simple names, but based on the meanings of the terms and the overall description of the present invention.

[0020] Referring to Figure 1 , this embodiment provides a method for testing the concentration of a citric acid system chemical decontaminant, including

[0021] removing iron ions from the decontaminant and testing the total concentration of citric acid in the decontaminant;

[0022] testing the concentration of citric acid complexed with iron ions in the decontaminant;

[0023] The concentration of the detergent is obtained by subtracting the concentration of citric acid complexed with iron ions from the total concentration of citric acid in the detergent.

[0024] In this test method, first, the iron ions in the detergent are removed. On the one hand, the influence of iron ions on acid-base neutralization during the test is removed, improving the test accuracy. On the other hand, after removing the iron ions, the total concentration of citric acid is detected, and then the concentration of citric acid complexed with iron ions is tested separately. Subtracting the concentration of citric acid complexed with iron ions from the detected total concentration of citric acid gives the effective concentration of the detergent, eliminating the influence of iron-ion complexed citric acid on the test result and making the measured citric acid concentration closer to the actual effective concentration of the detergent, which is beneficial for guiding the decontamination process and ensuring the decontamination effect.

[0025] The test method for the total concentration of citric acid in the detergent is as follows: Take a quantitative amount of the original detergent solution and dilute it. Remove the iron ions in it, then add a standard alkaline solution dropwise and detect the pH value. When the pH value reaches 7, stop titration and record the consumption of the standard alkaline solution. Based on the consumption of the standard alkaline solution, calculate the total concentration of citric acid in the detergent.

[0026] The total concentration of citric acid is tested by the method of acid-base neutralization. When the pH value of the solution is 7, citric acid is completely neutralized. By measuring the amount of the alkaline solution used to neutralize citric acid, the total concentration of citric acid is deduced. Since the iron ions in the detergent have been removed before the test, the influence of the presence of iron ions on acid-base neutralization is avoided, making the measured amount of the alkaline solution closer to the actual amount of the alkaline solution for neutralizing citric acid and further improving the test accuracy.

[0027] As an alternative embodiment, take an exchange column filled with cation resin and slowly pass the diluted detergent through the column to remove the iron ions in the detergent.

[0028] In some embodiments, the original detergent solution is diluted 10 times, the standard alkaline solution is the NaOH standard solution, and the concentration of the NaOH standard solution is 0.05 mol / L or 0.1 mol / L.

[0029] As an alternative embodiment, take a quantitative amount of the original detergent solution, inject a pretreatment solution, and observe whether the original detergent solution shows a blood-red color.

[0030] If no blood-red color appears, there are no iron ions in the original detergent solution.

[0031] If it turns blood - red, dilute the stock solution of the detergent, then add an appropriate amount of sulfosalicylic acid solution, and slowly drip the EDTA standard solution. When the diluted detergent changes from purple to light yellow, it is the titration end - point. Record the consumption of the EDTA standard solution, calculate the iron ion content in the detergent according to the consumption of the EDTA standard solution, and then calculate the concentration of citric acid that complexes with iron ions in the remover.

[0032] The EDTA standard solution is an aqueous solution prepared from disodium ethylenediaminetetraacetate. The EDTA standard solution is a commonly used ammonia complexing agent in coordination titration analysis, which can form stable chelates with various metal ions. By recording the consumption of the EDTA standard solution, the iron ion content in the detergent can be deduced, and then the concentration of citric acid complexing with iron ions can be obtained.

[0033] As an alternative embodiment, the pretreatment solution includes a potassium thiocyanate solution and an ammonium persulfate solution. The concentration of the potassium thiocyanate solution is 40%, and the concentration of the ammonium persulfate solution is 10%.

[0034] Since the coordination reaction between ferrous ions and the EDTA standard solution is slow and there are various coordination forms (such as Fe3 +, FeO 2 - etc.), it is easy to form interfering complexes. After pretreatment with ammonium persulfate solution to oxidize Fe2 + to Fe3 +, the reaction selectivity is significantly improved, the occurrence of side reactions is reduced, and the reaction rate is increased. At the same time, the pretreatment solution also includes a potassium thiocyanate solution, which is used as a chromogenic agent. By forming a blood - red complex with ferric ions, it is judged whether there are iron ions in the detergent. If not, subsequent tests are not required. If so, subsequent test work is carried out.

[0035] In some embodiments, the stock solution of the detergent is diluted 10 times, and the concentration of the EDTA standard solution is 0.05 mol / L or 0.1 mol / L.

[0036] As an alternative embodiment, demineralized water is used to dilute the detergent.

[0037] Use the above - mentioned method for testing the concentration of the citric - acid - based chemical detergent for experiments. The test conditions are as follows: prepare a citric - acid detergent with a concentration of about 2.0%, and add an Fe standard solution to the solution so that the Fe ion concentration is about 500 mg / L:

[0038] Take 10 mL of the above - mentioned citric - acid detergent, dilute it to 100 mL with demineralized water, prepare an exchange column with a diameter of about 3 cm and filled with cation - exchange resin, slowly flow the diluted detergent through the exchange column to remove the Fe ions in the detergent, and take 20 mL of the filtrate for testing the total concentration of citric acid;

[0039] Take the NaOH standard solution with a concentration of 0.05 mol / L and drip it into the 20 mL filtrate used for the total citric acid concentration test. When the pH value of the filtrate is 7, the consumption of the NaOH standard solution is measured to be 12.42 mL, and the total citric acid concentration is calculated to be 1.99%;

[0040] Take the above 20 mL citric acid detergent, add 2 - 3 mL of potassium thiocyanate solution and 5 mL of ammonium persulfate solution for pretreatment. The concentration of the potassium thiocyanate solution is 40%, and the concentration of the ammonium persulfate solution is 10%. By observation, it is found that the citric acid detergent turns blood - red, indicating that the citric acid detergent contains iron ions;

[0041] Dilute the citric acid detergent to 200 mL with demineralized water, add an appropriate amount of sulfosalicylic acid solution as an indicator, and then drip the EDTA calibration solution. After reaching the titration end point (the solution changes from purple to light yellow), the consumption of the EDTA calibration solution is measured to be 0.89 mL, and then the concentration of citric acid complexed with iron ions is calculated to be 0.17%;

[0042] Subtract the concentration of citric acid complexed with iron ions, 0.17%, from the total concentration of the citric acid detergent, 1.99%, to obtain the effective concentration of citric acid, 1.82%.

[0043] Refer to Figure 1 , a device for testing the concentration of a citric acid - based chemical detergent, used for the above - mentioned method for testing the concentration of a citric acid - based chemical detergent, including,

[0044] A titration cell 1, in which a stirrer 11, a pH sensor 12, and a color recognition sensor 13 are arranged;

[0045] A pretreatment agent addition pipeline 2, which includes a pretreatment agent bottle 21. The pretreatment agent bottle 21 is connected to the titration cell 1 through a pipeline; the pretreatment agent bottle 21 is specifically designed as two, one for containing potassium thiocyanate solution and the other for containing ammonium persulfate solution.

[0046] A titrant addition pipeline 3, which includes a titrant bottle 31. The titrant bottle 31 is connected to the titration cell 1 through a pipeline; the titrant bottle 31 is also designed as two, one for titrating the NaOH standard solution and the other for titrating the EDTA calibration solution.

[0047] A water replenishing pipeline 4, which includes a pure water tank 41. The pure water tank 41 is connected to the titration cell 1 through a pipeline;

[0048] The sample addition pipeline 5 includes a sample bottle 51. The sample bottle 51 is connected to the titration cell 1 through a pipeline. There are also two sample bottles 51. One is used to hold the test sample of the total concentration of the citric acid detergent, and the other is used to hold the test sample of the concentration of citric acid complexed with iron ions.

[0049] The waste liquid discharge pipeline 6 includes a waste liquid tank 61. The waste liquid tank 61 is connected to the titration cell 1 through a pipeline.

[0050] Reference Figure 1 , In some embodiments, peristaltic pumps 7 are provided on the pipelines between the titration cell 1 and the pretreatment agent bottle 21, the pure water tank, and the waste liquid tank 61; injection pumps 8 are provided on the pipelines between the titration cell 1 and the titrant bottle 31 and the sample bottle 51.

[0051] The make-up water pipeline 4 is used on the one hand to make up demineralized water into the titration cell 1 to dilute the test solution, and on the other hand to flush the titration cell 1. The make-up water pipeline 4 is also connected to the injection pump 8 through a pipeline to clean the injection pump 8.

[0052] The decontamination liquid has a certain radioactivity. Reducing the time for analysts to contact the decontamination agent and reducing the radiation dose of personnel during the analysis of the decontamination agent concentration are of great significance for the control of the overhaul dose of nuclear power plants. In this application, by designing a test device corresponding to the above test method, the operation of analysts is reduced, thereby reducing the time for analysts to contact the decontamination agent and reducing the radiation dose of personnel during the analysis of the decontamination agent concentration.

[0053] Finally, it should be pointed out that the methods and devices described in detail above are only examples, and those skilled in the art can modify these examples in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A method for testing the concentration of a chemical decontaminant in a citric acid system, characterized in that: include, Remove iron ions from detergents and test the total concentration of citric acid in detergents; Test the concentration of citric acid in the detergent to complex the iron ions; The concentration of the detergent was obtained by subtracting the concentration of citric acid complexed with iron ions from the total concentration of citric acid in the detergent.

2. The method for testing the concentration of the chemical decontaminant in the citric acid system according to claim 1, wherein: Take a quantitative detergent stock solution and dilute it to remove the iron ions, then add alkaline standard solution and test the pH value. When the pH value reaches 7, stop the titration and record the consumption of alkaline standard solution. Based on the consumption of alkaline standard solution, calculate the total concentration of citric acid in the detergent.

3. The method for testing the concentration of the chemical decontaminant in the citric acid system according to claim 2, wherein: Take an exchange column filled with cationic resin and slowly pass the diluted detergent through the exchange column to remove the iron ions in the detergent.

4. The method for testing the concentration of the chemical detergent in the citric acid system according to claim 2, wherein: The detergent stock solution is diluted 10 times, the alkaline standard solution is NaOH standard solution, and the concentration of NaOH standard solution is 0.05 mol / L or 0.1 mol / L.

5. The method for testing the concentration of a citric acid system chemical detergent according to claim 1, wherein: Take a certain amount of detergent stock solution, inject it into the pretreatment solution, and observe whether the detergent stock solution turns blood red. If a blood-red color does not appear, there are no iron ions in the detergent stock solution; If a blood red color appears, dilute the detergent stock solution, then add an appropriate amount of sulfosalicylic acid solution, and slowly add EDTA standard solution. The titration end point is when the diluted detergent changes from purple to light yellow. Record the consumption of EDTA standard solution. Calculate the iron ion content in the detergent based on the consumption of EDTA standard solution, and then calculate the citric acid concentration in the detergent that complexes the iron ions.

6. The method for testing the concentration of the chemical detergent in the citric acid system according to claim 5, wherein: The pretreatment solution includes a potassium thiocyanate solution and an ammonium persulfate solution, wherein the concentration of the potassium thiocyanate solution is 40% and the concentration of the ammonium persulfate solution is 10%.

7. The method for testing the concentration of a citric acid-based chemical detergent according to claim 5, wherein: The detergent stock solution was diluted 10 times, and the concentration of the EDTA standard solution was 0.05 mol / L or 0.1 mol / L.

8. The method for testing the concentration of the chemical decontaminant in the citric acid system according to claim 2 or 5, characterized in that: Dilute the detergent with demineralized water.

9. A concentration testing device for a chemical decontamination agent in a citric acid system, which is used for the method for testing the concentration of the chemical decontamination agent in a citric acid system according to any one of claims 1 to 8, and is characterized in that: include, A titration cell (1), wherein a stirrer (11), a pH sensor (12) and a color recognition sensor (13) are provided in the titration cell (1); A pretreatment agent adding pipeline (2), comprising a pretreatment agent bottle (21), wherein the pretreatment agent bottle (21) is connected to the titration cell (1) via a pipeline; a titrant addition pipeline (3), wherein the titrant addition pipeline (3) comprises a titrant bottle (31), and the titrant bottle (31) is connected to the titration cell (1) via a pipeline; A water supply pipeline (4), wherein the water supply pipeline (4) comprises a pure water tank (41), and the pure water tank (41) is connected to the titration cell (1) via a pipeline; A sample addition pipeline (5), wherein the sample addition pipeline (5) comprises a sample bottle (51), and the sample bottle (51) is connected to the titration cell (1) via a pipeline; A waste liquid discharge pipeline (6), wherein the waste liquid discharge pipeline (6) comprises a waste liquid tank (61), and the waste liquid tank (61) is connected to the titration cell (1) via a pipeline.

10. The citric acid system chemical decontamination agent concentration testing device according to claim 9, characterized in that: Peristaltic pumps (7) are provided on the pipelines between the titration tank (1) and the pretreatment agent bottle (21), the pure water tank, and the waste liquid tank (61); The pipelines between the titration cell (1), the titration liquid bottle (31) and the sample bottle (51) are all provided with injection pumps (8).

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