Method for detecting content of zinc ions in water treatment agent and application

Abstract

The invention provides a method for detecting the content of zinc ions in a water treatment agent and application. The detection method comprises the following steps: S1) pre-treating a water treatment agent by using an acid solution to obtain a pre-treated product; s2) adjusting the pH value of the pretreatment product to 9.0-10.5, and mixing chrome black T with the pretreatment product to obtain a solution to be detected; s3) carrying out first titration on the to-be-detected solution by using the EDTA solution, stopping the first titration until the color of the to-be-detected solution is changed from amaranth to blue green, recording the addition amount of the EDTA solution, and calculating the content of zinc ions in the water treatment agent according to the addition amount of the EDTA solution; wherein the acid solution comprises a sulfuric acid solution and a nitric acid solution; the water treatment agent comprises a corrosion and scale inhibitor, a corrosion inhibitor or a pre-filming agent. The method can solve the problem of low detection accuracy of the zinc ion content in the water treatment agent in the prior art, and is suitable for the field of water treatment agent detection.

Description

Technical Field

[0001] The invention relates to the field of water treatment agent detection, and in particular to a method for detecting zinc ion content in a water treatment agent and an application thereof. Background Art

[0002] In the chemical production process, the circulating cooling water system is an indispensable industrial auxiliary cooling system, which is responsible for removing the waste heat generated in the industrial production process and ensuring the normal operation of each unit device and reaction process. During the operation of the circulating cooling water system, after the cooling water passes through the cooling equipment, cooling tower and pipelines of varying lengths, the water quality will undergo a series of changes such as temperature change, evaporation concentration, and enrichment and oxidation, which can easily cause equipment corrosion and scaling, resulting in reduced heat transfer efficiency and serious equipment wear. At present, the most commonly used method to prevent corrosion is to pre-film the circulating cooling water device before starting or after chemical cleaning, and add a pre-filming agent to form a complete and dense protective film on the metal inner wall of the heat exchange equipment, pipelines, etc.; and when the circulating cooling water system is operating normally, corrosion inhibitors and scale inhibitors or corrosion inhibitors will continue to be added to play a "film replenishment" role.

[0003] Zinc salt is the most commonly used cathode corrosion inhibitor. In the circulating water system, zinc ions can quickly form Zn(OH)2 precipitation film in the high pH area of ​​the cathode, thereby preventing further corrosion of the metal. However, the zinc film is soft and not durable, and is generally not used alone. Currently, commonly used corrosion and scale inhibitors, corrosion inhibitors, pre-filming agents, etc. are all compound agents, with zinc ions as the active ingredient and a high content. After the circulating cooling water is discharged, zinc ions enter the water body and are easily absorbed by organisms due to their active chemical properties, affecting the survival and reproduction of fish and plankton, thereby leading to the destruction of the aquatic ecosystem and the deterioration of the ecological environment. At present, the country limits the concentration of zinc ions discharged from industry to between 2-5ppm (GB 31574-2015 Industrial Pollutant Emission Standards for Recycled Copper, Aluminum, Lead and Zinc), and the prior art usually adopts the method of "Determination of Nickel, Manganese, Copper and Zinc Content in Water Treatment Agents - Inductively Coupled Plasma Emission Spectrometry (ICP-OES) Method" (HGT 5747-2020 or "Boiler Water and Cooling Water Analysis Method - Determination of Zinc Ions - Zinc Reagent Spectrophotometry" (GB / T 10656-2022) to detect corrosion and scale inhibitors, corrosion inhibitors and pre-filming agents. However, the method detects the zinc ion content in corrosion and scale inhibitors, corrosion inhibitors and pre-filming agents, which deviates greatly from the true value. Therefore, the development of an accurate zinc ion detection method is of great significance for controlling the quality of reagents, accurately dosing, and controlling the amount of external water discharged. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for detecting the zinc ion content in a water treatment agent and its application, so as to solve the problem of low accuracy in detecting the zinc ion content in the water treatment agent in the prior art.

[0005] In order to achieve the above-mentioned object, according to a first aspect of the present invention, a method for detecting the zinc ion content in a water treatment agent is provided, the detection method comprising: S1) pre-treating the water treatment agent with an acid solution to obtain a pre-treatment product; S2) adjusting the pH of the pre-treatment product to 9.0-10.5, and mixing chrome black T with the pre-treatment product to obtain a solution to be tested; S3) performing a first titration on the solution to be tested with an EDTA solution, stopping the first titration when the color of the solution to be tested changes from purple-red to blue-green, recording the amount of EDTA solution added, and calculating the zinc ion content in the water treatment agent according to the amount of EDTA solution added; wherein the acid solution comprises a sulfuric acid solution and a nitric acid solution; and the water treatment agent comprises a corrosion and scale inhibitor, a corrosion inhibitor or a pre-filming agent.

[0006] Further, S1) includes: S11) pre-dissolving the water treatment agent to obtain a pre-dissolved product; S12) mixing the pre-dissolved product with an acid solution and heating it to obtain a pre-treated product; preferably, the pre-dissolution includes: mixing the water treatment agent with water, and the mass ratio of the water treatment agent to water is 1:5 to 15.

[0007] Further, S12) includes: adding sulfuric acid solution and nitric acid solution to the pre-dissolved product in sequence, and then heating to obtain a pre-treated product; preferably, the volume ratio of the sulfuric acid solution to the nitric acid solution is 1:10-25; preferably, the volume ratio of the pre-dissolved product to the sulfuric acid solution is 1:0.05-0.15; preferably, the volume ratio of the pre-dissolved product to the nitric acid solution is 1:1.5-2.5.

[0008] Furthermore, the concentration of nitric acid in the nitric acid solution is 20-30%; the concentration of sulfuric acid in the sulfuric acid solution is 50-75%.

[0009] Furthermore, the heating temperature is 90-130° C.; preferably, the heating time is 60-120 min.

[0010] Further, the calculation includes: calculating the zinc ion content using the following formula;

[0011]

[0012] Wherein, ω is the mass fraction of zinc ions, in %;

[0013] c(EDTA) is the concentration of EDTA in the EDTA solution, in moles per liter;

[0014] V1 is the amount of EDTA solution added in the first titration, in milliliters;

[0015] M is the molar mass of zinc in grams per mole;

[0016] m is the mass of the water treatment agent in the solution to be tested, in grams.

[0017] Furthermore, the detection method also includes mixing chrome black T with water to obtain a control solution; performing a second titration on the control solution using an EDTA solution, and stopping the second titration when the color of the control solution changes from purple-red to blue-green, and recording the amount of EDTA solution added.

[0018] Further, the calculation includes: the following formula is used to calculate the zinc ion content;

[0019]

[0020] Wherein, ω is the mass fraction of zinc ions, in %; c(EDTA) is the concentration of EDTA solution, in moles per liter; V1 is the amount of EDTA solution added in the first titration, in milliliters; V2 is the product of the amount of EDTA solution added in the second titration, in milliliters; M is the molar mass of zinc, in grams per mole; m is the mass of the water treatment agent in the solution to be tested, in grams.

[0021] Furthermore, the concentration of EDTA in the EDTA solution is 0.0090 to 0.0200 mol / L.

[0022] Furthermore, the volume of the solution to be tested is 0.5 to 3 mL.

[0023] In order to achieve the above object, according to a second aspect of the present invention, there is provided an application of the above method for detecting zinc ion content in detecting zinc ion content in a water treatment agent.

[0024] The technical solution of the present invention is applied, and the water treatment agent is pre-treated with an acid solution so that the zinc ions in the water treatment agent are fully released, and the pH of the pre-treatment product is adjusted to 9.0-10.5, and chrome black T is dripped into the pre-treatment product as an indicator, and the first titration is performed on it with an EDTA solution, and the first titration is stopped when the color of the solution to be tested changes from purple-red to blue-green, and the amount of EDTA solution added is recorded, and the zinc ion content in the water treatment agent can be calculated according to the amount of EDTA solution added. Compared with the detection method of the prior art, the detection method of the present application has higher accuracy and can accurately detect the zinc ion content in the water treatment agent. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0026] Terminology explanation:

[0027] Relative recovery rate: The relative recovery rate in this application refers to the ratio of the detected value of zinc ions to the actual value, which is used to measure the accuracy of the detection. As mentioned in the background technology, the prior art generally uses the method of "Inductively coupled plasma emission spectrometry (ICP-OES) method for determination of nickel, manganese, copper and zinc content in water treatment agents" (HGT 5747-2020) to detect corrosion inhibitors, scale inhibitors, corrosion inhibitors, and pre-filming agents, but the detection accuracy is low. Therefore, in this application, the inventors try to develop a new method for detecting zinc ion content, based on which, a series of protection schemes of this application are proposed.

[0028] In a first typical embodiment of the present application, a method for detecting the zinc ion content in a water treatment agent is provided, and the detection method comprises: S1) pre-treating the water treatment agent with an acid solution to obtain a pre-treatment product; S2) adjusting the pH of the pre-treatment product to 9.0-10.5, and mixing chrome black T with the pre-treatment product to obtain a test solution; S3) performing a first titration on the test solution with an EDTA solution, and stopping the first titration and recording the amount of EDTA solution added when the color of the test solution changes from purple-red to blue-green, and calculating the zinc ion content in the water treatment agent according to the amount of EDTA solution added; wherein the water treatment agent comprises a corrosion and scale inhibitor, a corrosion inhibitor or a pre-filming agent.

[0029] In the circulating cooling water system of chemical production, water treatment agents are often used to treat the circulating cooling water system. Commonly used water treatment agents are corrosion inhibitors and scale inhibitors, corrosion inhibitors and pre-filming agents. Water treatment agents contain a large amount of zinc ions. In order to meet the zinc ion concentration of industrial emissions (2-5ppm), the input amount of the water treatment agent must be calculated before adding it, so that the zinc ion content in the subsequent discharged water meets the industrial emission standards. However, when calculating the input amount, due to the different zinc ion content in water treatment agent samples from different manufacturers and batches, the zinc ion content must be accurately tested to guide precise medication.

[0030] In the prior art, the method of "Determination of Nickel, Manganese, Copper and Zinc Content in Water Treatment Agents by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES)" (HGT 5747-2020) is usually used to detect corrosion and scale inhibitors, corrosion inhibitors and pre-filming agents to guide the use of the drugs. However, this method detects the zinc ion content in corrosion and scale inhibitors, corrosion inhibitors and pre-filming agents, which deviates greatly from the actual value and cannot correctly reflect the zinc ion content in the agent. This standard uses the high temperature generated by argon plasma to completely decompose the sample to form excited atoms and ions. Since excited atoms and ions are unstable, the outer electrons will transition from the excited state to a lower level, emitting characteristic spectral lines. The intensity of the characteristic spectral lines is proportional to the concentration of the element being measured, and the content of the element to be measured in the sample is determined. This standard is applicable to the determination of nickel content in the range of 0.00002% to 0.2%, manganese content in the range of 0.00002% to 0.2%, copper content in the range of 0.00002% to 0.2%, and zinc content in the range of 0.00002% to 0.2% in water treatment agents.

[0031] However, at present, the zinc ion content in commonly used industrial corrosion inhibitors is usually greater than 10%, while the zinc ion content in pre-filming agents is even higher. When using this standard for testing, the dilution multiple needs to be increased. As the dilution multiple increases, the distortion of the test results is further aggravated. In addition, the equipment investment of this standard method is large, and a standard curve needs to be prepared before each test. The operation is cumbersome, the consumption of EDTA solution, reagents, argon gas, etc. is large, and the test cost is high.

[0032] Due to the above-mentioned problems in the above-mentioned standards, the prior art also detects zinc ions by referring to the method of "Analysis Method for Zinc Ions in Boiler Water and Cooling Water - Zinc Reagent Spectrophotometry" (GB / T 10656-2022). The detection method recorded in the standard is "take an appropriate volume of sample for detection", but due to different manufacturers, the zinc ion content in corrosion inhibitors, scale inhibitors, pre-filming agents, and corrosion inhibitors is different, and the standard of "appropriate amount" is difficult to define, so it may lead to different dilution concentrations of samples, different sample amounts, and different test values ​​of each batch, which are quite different and difficult to meet the detection requirements.

[0033] Moreover, although the EDTA complexometric titration method is also used for the detection of zinc ions in circulating cooling water disclosed in the prior art, the zinc ion content in circulating cooling water is usually low, and the zinc ion content of industrial circulating cooling water generally needs to be controlled at less than 2 mg / L (GB 31574-2015 Pollutant Emission Standards for Regenerated Copper, Aluminum, Lead, and Zinc Industries), while the zinc ion content in most corrosion and scale inhibitors, corrosion inhibitors, and pre-filming agents is usually greater than 5% of the mass fraction of the reagent. Therefore, the EDTA titration method used to detect the zinc ion content of circulating cooling water is not suitable for the detection of the zinc ion content of corrosion and scale inhibitors, corrosion inhibitors, and pre-filming agents.

[0034] The above-mentioned standard method in the prior art is different for the pre-treatment steps of organic water treatment agents and inorganic water treatment agents. For water treatment agents with unknown components, different pre-treatment methods need to be used respectively, different standard solvents are configured, different standard curves are made for detection, and the test results are compared. This process is time-consuming, the operation process is complicated, and it is easy to cause errors in detection. The digestion method in the pre-treatment of the present application is applied to both organic water treatment agents and inorganic water treatment agents to make them completely digested, and the digestion steps are simple, time-consuming, and it is beneficial to improve subsequent test results, simplify the process of pre-treatment, and the reagent cost is low, which further reduces the cost of zinc ion content detection.

[0035] Based on the above-mentioned pretreatment digestion step, the detection method of zinc ion content in the present application adopts EDTA complexometric titration, using EDTA and Zn 2+ The principle of forming a 1:1 complex is to use chrome black T as an indicator and calculate the Zn 2+ The detection method of the present application has simple operation steps, does not require expensive detection equipment, chemical reagents, etc., and the detection results are accurate and highly repeatable. The zinc ion content can be accurately determined even when it is as high as 20%. It is more suitable for use in the detection process of zinc ion content in corrosion and scale inhibitors, corrosion inhibitors, and pre-filming agents.

[0036] In a preferred embodiment, S1) includes: S11) pre-dissolving the water treatment agent to obtain a pre-dissolved product; S12) mixing the pre-dissolved product with an acid solution and heating it to obtain a pre-treated product; preferably, the pre-dissolving includes: mixing the water treatment agent with water, and the mass ratio of the water treatment agent to the water is 1:5-15. Preferably, when the water treatment agent is liquid, the mass ratio of the water treatment agent to the water is 1:5-6, more preferably 1:5; preferably, when the water treatment agent is solid, the mass ratio of the water treatment agent to the water is 1:9-10, more preferably 1:10.

[0037] In a preferred embodiment, S12) comprises: adding sulfuric acid solution and nitric acid solution to the pre-dissolved product in sequence, and then heating to obtain a pre-treated product; preferably, the volume ratio of sulfuric acid to nitric acid is 1:10-25. Preferably, the volume ratio of sulfuric acid to nitric acid is 1:15-20, more preferably 1:20; preferably, the volume ratio of the pre-dissolved product to the sulfuric acid solution is 1:0.05-0.15, more preferably 1:0.1; preferably, the volume ratio of the pre-dissolved product to the nitric acid solution is 1:1.5-2.5, more preferably 1:2.

[0038] In a preferred embodiment, the concentration of nitric acid in the nitric acid solution is 20-30%; the concentration of sulfuric acid in the sulfuric acid solution is 20-30%. + The concentration is 50-75%.

[0039] In a preferred embodiment, the heating temperature is 90-130°C, including but not limited to 90, 100, 110, 120 or 130°C; preferably, the heating time is 60-120min, including but not limited to 60, 70, 80, 90, 100, 110 or 120min; more preferably, the heating temperature is 100-120°C.

[0040] The present application further improves the effect of digestion in the pretreatment by precisely controlling the conditions of the pretreatment process within the above range, which is beneficial to destroying organic matter, dissolving particulate matter, and converting zinc of various valence states in the water treatment agent into easily decomposable inorganic ions, and completely digesting it, which is beneficial to improving the accuracy of subsequent test results.

[0041] In a preferred embodiment, the calculation includes: calculating the zinc ion content using the following formula;

[0042]

[0043] Wherein, ω is the mass fraction of zinc ions, in %;

[0044] c(EDTA) is the concentration of EDTA in the EDTA solution, in moles per liter;

[0045] V1 is the amount of EDTA solution added in the first titration, in milliliters;

[0046] M is the molar mass of zinc in grams per mole;

[0047] m is the mass of the water treatment agent in the solution to be tested, in grams.

[0048] In a preferred embodiment, the detection method further includes mixing chrome black T with water to obtain a control solution; performing a second titration on the control solution using an EDTA solution, and stopping the second titration when the color of the control solution changes from purple-red to blue-green, and recording the amount of EDTA solution added.

[0049] In a preferred embodiment, the calculation includes: calculating the zinc ion content using formula I;

[0050]

[0051] Wherein, ω is the mass fraction of zinc ions, in %;

[0052] c(EDTA) is the concentration of EDTA in the EDTA solution, in moles per liter;

[0053] V1 is the amount of EDTA solution added in the first titration, in milliliters;

[0054] V2 is the added volume of EDTA solution in the second titration, in milliliters;

[0055] M is the molar mass of zinc in grams per mole;

[0056] m is the mass of the water treatment agent in the solution to be tested, in grams.

[0057] The above m can be understood as follows: for example, when 2 g of the water treatment agent is taken, and the volume is diluted to 100 mL during the digestion process of the pretreatment, the concentration of the water treatment agent solution is 0.02 g / mL. If the sample volume of the test solution is 2 mL, the mass of the water treatment agent in the test solution is 0.04 g. In a preferred embodiment, the concentration of EDTA in the EDTA solution is 0.0090 to 0.0200 mol / L; preferably, the concentration of the EDTA solution is 0.0095 to 0.0150 mol / L, more preferably 0.010 mol / L.

[0058] In a preferred embodiment, the volume of the solution to be tested is 1-3 mL; preferably, the volume of the solution to be tested is 2 mL.

[0059] The present application helps to improve the accuracy of detection by precisely controlling the titration conditions within the above range.

[0060] In a second typical embodiment of the present application, there is provided an application of the above-mentioned method for detecting the zinc ion content in detecting the zinc ion content of a corrosion and scale inhibitor, a corrosion inhibitor or a pre-filming agent.

[0061] In a preferred embodiment, the mass fraction of zinc ion content in the corrosion and scale inhibitor, corrosion inhibitor and pre-filming agent is 0.1-30%.

[0062] The beneficial effects of the present application will be further explained in detail below in conjunction with specific embodiments.

[0063] Unless otherwise specified, the reagents used in the examples of this application are all conventional commercially available products.

[0064] Example 1

[0065] The detection methods of the embodiments of the present application are as follows:

[0066] (1) Solution preparation

[0067] Concentrated sulfuric acid: mass concentration is 68%.

[0068] Hydrochloric acid: mass concentration is 20%.

[0069] Nitric acid: mass concentration is 20%;

[0070] Ammonia solution: mass concentration 28%;

[0071] Eriochrome Black T indicator: weigh 0.50g Eriochrome Black T and 2.0g hydroxylamine hydrochloride and dissolve in ethanol, dilute to 100mL with ethanol;

[0072] Ammonia-ammonium chloride buffer: weigh 54 g of ammonium chloride and dissolve it in 500 mL of water, add 350 mL of concentrated ammonia water, add 1 g of EDTA disodium magnesium salt, and dilute with water to 1 L. The above weighings are accurate to 0.2 mg.

[0073] Preparation of disodium ethylenediaminetetraacetate standard solution (0.01 mol / L): Weigh 4 g of disodium ethylenediaminetetraacetate, add 1000 mL of water, heat to dissolve, cool, and shake well (refer to "Preparation of Chemical Reagent Titration Solution GB / T601-2016").

[0074] Calculation of the calibration concentration of the disodium ethylenediaminetetraacetic acid standard solution: weigh 0.03g zinc oxide, add a small amount of water to moisten it, add 2mL hydrochloric acid solution, adjust the pH to 7-8 with ammonia solution, add 10mL of ammonium chloride buffer and 5 drops of chrome black T indicator, and titrate with the prepared 0.01mol / L solution until the color changes from purple to pure blue. At the same time, do a blank experiment. This is the calibration concentration of the disodium ethylenediaminetetraacetic acid standard solution.

[0075]

[0076] m: the mass of zinc oxide, in grams (g);

[0077] V1: Volume of disodium EDTA standard solution, in milliliters (mL);

[0078] V2: Blank consumption of disodium EDTA standard solution volume, in milliliters (mL);

[0079] M: molar mass of zinc oxide, in grams per mole (g / mol) [M(ZnO)=81.408].

[0080] The blank experiment is as follows: add 2 mL of hydrochloric acid solution to 2 mL of deionized water, adjust the pH to 7-8 with an ammonia solution, add 10 mL of ammonium chloride buffer, add 5 drops of chrome black T indicator, and titrate with the prepared disodium ethylenediaminetetraacetic acid standard solution until the purple-red color changes to blue-green.

[0081] (2) Sample digestion (pretreatment)

[0082] Weigh 2g of liquid sample or 1g of solid sample into a 250mL round-bottom flask, accurate to 0.2mg. Add 10mL of water to pre-dissolve and disperse the sample. Slowly add 1mL of sulfuric acid, then add 20mL of nitric acid, install a reflux condenser, heat to a slight boil to reflux the solution, until the sample solution is not turbid after adding water after cooling, then digestion is complete. The digestion temperature is 110℃ and the digestion time is 90min. After cooling to room temperature, add water to dissolve in a 100mL volumetric flask.

[0083] Use a pipette to transfer 2.00 mL of the above solution into a conical flask, add 2 drops of ammonia water, 80 mL of deionized water, 10 mL of ammonia-ammonium chloride buffer, adjust the pH to between 9.0 and 10.5, add 3-5 drops of chrome black T indicator, and perform a blank test at the same time. Finally, titrate with EDTA until the solution changes from purple-red to blue-green, which is the titration endpoint. Repeat the test 3 times in parallel, record the volume of EDTA consumed, and calculate the content according to the following formula:

[0084]

[0085] ω: is the mass fraction of zinc ions, in %.

[0086] c(EDTA): concentration of EDTA, in moles per liter (mol / L);

[0087] V1: Volume of disodium EDTA standard solution, in milliliters (mL);

[0088] V2: Blank consumption of disodium EDTA standard solution volume, in milliliters (mL);

[0089] M: molar mass of zinc, in grams per mole (g / mol) [M(Zn) = 65.38];

[0090] m: The mass of the water treatment agent sample in the test solution, in grams (g, accurate to 0.2 mg).

[0091] The blank experiment is as follows: add 2 drops of ammonia water and 10.mL of ammonium chloride buffer to 80mL of deionized water, adjust the pH to 9.0-10.5, add 3-5 drops of chrome black T indicator, and titrate with the prepared disodium ethylenediaminetetraacetic acid standard solution until the purple-red color changes to blue-green.

[0092] The slow-release scale inhibitor 1 (experiments 1-5) whose components are all organic components and whose zinc ion content is 5.17%, and the corrosion inhibitor 1 (experiments 6-9) whose components are all inorganic components and whose zinc ion concentration is greater than 15% with technical parameters provided by the manufacturer were digested under different digestion conditions. The sampling amount was 2g. After the digestion, the digestion system was cooled to room temperature, and water was added to dissolve it in a 100mL volumetric flask to observe the digestion results. The different digestion conditions and digestion results in experiments 1-5 are shown in Table 1. The different digestion conditions and digestion results in experiments 6-9 are shown in Table 2.

[0093] Table 1

[0094]

[0095] Table 2

[0096]

[0097] Example 2

[0098] The corrosion and scale inhibitor 2 (zinc ion content of 3.84%) and the corrosion and scale inhibitor 3 (zinc ion content of 4.80%) containing organic components and inorganic components were tested for zinc ion content using the industry standard (HG / T 5747-2020) and the detection method of the present application, and the test results are shown in Tables 3 and 4, respectively.

[0099] Table 3

[0100]

[0101] From the results in Table 3, it can be seen that the standard deviation between the three parallel samples of corrosion and scale inhibitor 2 is greater than 1, and the standard deviation between the three parallel samples of corrosion and scale inhibitor 3 is less than 1. This shows that the detection method proposed in the standard (HGT 5747-2020) has low precision and accuracy during detection, and the detection results are distorted when the zinc ion concentration in corrosion and scale inhibitors, corrosion inhibitors, and pre-filming agents is high.

[0102] The samples of corrosion and scale inhibitor 2 and corrosion and scale inhibitor 3 were tested according to the test method of Example 1 of the present application, and the test results are shown in Table 4. From the test results, the standard deviations between the three parallel samples of corrosion and scale inhibitor 1 and corrosion and scale inhibitor 2 are all less than 1. This shows that the detection method of Example 1 of the present application has high precision and accuracy when the zinc ion concentration in the corrosion and scale inhibitor, corrosion inhibitor, and pre-filming agent is high.

[0103] Table 4

[0104]

[0105] The zinc ion contents of corrosion inhibitor 4, corrosion inhibitor 5, corrosion inhibitor 6 (zinc ion content>5% in the report provided by the manufacturer) containing organic components and inorganic components, and corrosion inhibitor 2 with a zinc ion content>15% were tested using the standard (HGT 5747-2020) and the detection method of the present application, respectively, and compared with the zinc ion content parameters in the factory products provided by the manufacturer. The results are shown in Table 5.

[0106] Table 5

[0107]

[0108] It can be seen from Table 5 that the detection method of the present application is more consistent with the zinc ion content parameters in the factory products provided by the manufacturer, which shows that the detection method of the present application has a higher accuracy at high concentrations of zinc ions.

[0109] Comparative Example 1

[0110] The zinc ions in corrosion and scale inhibitors are detected with reference to the standard "Analysis method for boiler water and cooling water - Determination of zinc ions - Zinc reagent spectrophotometry" (GB / T10656-2022).

[0111] Take 0.5266g of corrosion and scale inhibitor whose components are all organic components, with a theoretical zinc ion content of 2.2%, and dilute it 1000 times in a 500mL volumetric flask for later use. At this time, the concentration of the solution is 1053.2mg / L. Use the above standard to detect the zinc ion content of the corrosion and scale inhibitor. According to the method described in the above standard, draw a standard curve, R 2 =0.999, which meets the standard requirements.

[0112] The test results of different sampling volumes, sample mass (m), concentration (ρ) and zinc ion content in the sampling solution are shown in Table 6.

[0113] Table 6

[0114]

[0115]

[0116] It can be seen from Table 6 that when the corrosion inhibitor and scale inhibitor is diluted 1000 times, the measured zinc ion content is different due to different sampling amounts, and the test results of different sampling amounts vary greatly, with low accuracy and consistency.

[0117] Take 1.151g of water treatment agent whose components are all organic components, the theoretical zinc ion content is 5.17%, after dilution 100 times, the solution concentration is 11.51g / L, and the zinc ion content of the corrosion inhibitor and scale inhibitor is detected using the above standard. The detection results of different sampling amounts, sample mass, concentration, and zinc ions in the sampling solution are shown in Table 7. 0.1mL is transferred, and the zinc ion content in the test result is 7.04%; after dilution 1000 times, the solution concentration is 1.151g / L, and 0.1mL is transferred, and the zinc ion content in the test result is 9.56%. It can be seen that when the dilution multiple is different, even if the sampling amount is the same, the results will be quite different, the repeatability is poor, and the accuracy is low. Therefore, the method of this standard is not suitable for the detection of zinc ion content in water treatment agents.

[0118] Table 7

[0119] Sampling volume 0.1mL 0.1mL m(mg) 0.081 0.011 ρ(mg / L) 810 110 Zinc ion content (%) 7.04 9.56

[0120] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: by utilizing the detection method of zinc ion content of the present application, the zinc ion content in corrosion inhibitors, scale inhibitors, corrosion inhibitors, and pre-filming agents used as water treatment agents for circulating cooling water is detected. The method is simple, the reagent consumption is small, and the pre-treatment digestion method is applicable to both agents containing organic components and agents containing inorganic components. The detection results are highly accurate and repeatable. It can accurately and quickly detect the zinc ion content in corrosion inhibitors, scale inhibitors, corrosion inhibitors, and pre-filming agents, can assist in determining whether the agents are qualified, and guide the precise dosing of subsequent products to control the zinc ion content of the discharged circulating cooling water.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting the zinc ion content in a water treatment agent, characterized in that: The detection method comprises: S1) pre-treating the water treatment agent with an acid solution to obtain a pre-treated product; S2) adjusting the pH of the pre-treatment product to 9.0-10.5, and mixing chrome black T with the pre-treatment product to obtain a solution to be tested; S3) performing a first titration on the solution to be tested using an EDTA solution, stopping the first titration when the color of the solution to be tested changes from purple-red to blue-green, recording the amount of the EDTA solution added, and calculating the zinc ion content in the water treatment agent according to the amount of the EDTA solution added; Wherein, the acid solution includes sulfuric acid solution and nitric acid solution; The water treatment agent includes a corrosion inhibitor and scale inhibitor, a corrosion inhibitor or a pre-filming agent.

2. The detection method according to claim 1, characterized in that: Said S1) comprises: S11) pre-dissolving the water treatment agent to obtain a pre-dissolved product; S12) mixing the pre-dissolved product with the acid solution and heating them to obtain the pre-treated product; Preferably, the pre-dissolution comprises: mixing the water treatment agent with water, and the mass ratio of the water treatment agent to water is 1:5-15.

3. The detection method according to claim 2, characterized in that: The S12) comprises: sequentially adding the sulfuric acid solution and the nitric acid solution to the pre-dissolved product, and then heating to obtain the pre-treated product; Preferably, the volume ratio of the sulfuric acid solution to the nitric acid solution is 1:10-25; Preferably, the volume ratio of the pre-dissolved product to the sulfuric acid solution is 1:0.05-0.15; preferably, the volume ratio of the pre-dissolved product to the nitric acid solution is 1:1.5-2.

5.

4. The detection method according to claim 3, characterized in that: The concentration of nitric acid in the nitric acid solution is 20-30%; The concentration of sulfuric acid in the sulfuric acid solution is 50-75%.

5. The detection method according to claim 3, characterized in that: The heating temperature is 90-130°C; Preferably, the heating time is 60 to 120 minutes.

6. The detection method according to any one of claims 1 to 5, characterized in that: The calculation includes: calculating the zinc ion content using the following formula; Wherein, ω is the mass fraction of zinc ions, in %; c(EDTA) is the concentration of EDTA in the EDTA solution, in moles per liter; V1 is the amount of EDTA solution added in the first titration, in milliliters; M is the molar mass of zinc in grams per mole; m is the mass of the water treatment agent in the solution to be tested, in grams.

7. The detection method according to any one of claims 1 to 5, characterized in that: The detection method further comprises mixing the chrome black T with water to obtain a control solution; performing a second titration on the control solution using the EDTA solution, When the color of the control solution changes from purple-red to blue-green, the second titration is stopped and the amount of the EDTA solution added is recorded.

8. The detection method according to claim 7, characterized in that: The calculation includes: calculating the zinc ion content using the following formula; Wherein, ω is the mass fraction of zinc ions, in %; c(EDTA) is the concentration of EDTA in the EDTA solution, in moles per liter; V1 is the amount of EDTA solution added in the first titration, in milliliters; V2 is the amount of EDTA solution added in the second titration, in milliliters; M is the molar mass of zinc in grams per mole; m is the mass of the water treatment agent in the solution to be tested, in grams.

9. The detection method according to claim 1, characterized in that: The concentration of EDTA in the EDTA solution is 0.0090-0.0200 mol / L; Preferably, the volume of the solution to be tested is 0.5-3 mL.

10. Use of the method for detecting zinc ion content according to any one of claims 1 to 9 in detecting zinc ion content in a water treatment agent.

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