Method for measuring content of corrosion and scale inhibitor in water sample and method for controlling concentration of corrosion and scale inhibitor in circulating water system

Abstract

The invention relates to the field of water treatment, and discloses a method for measuring the content of a corrosion and scale inhibitor in a water sample and a method for controlling the concentration of the corrosion and scale inhibitor in a circulating water system. The method comprises the following steps: contacting an extraction agent, a cosolvent and a to-be-detected water sample containing a corrosion and scale inhibitor for extraction, and carrying out first oil-water separation on the obtained mixed solution to obtain an oil phase; wherein the corrosion and scale inhibitor is a polymer containing a sulfonic acid group; the extraction agent is trialkyl tertiary amine, and the carbon atom number of alkyl in the trialkyl tertiary amine is 8-10; the cosolvent is at least one of n-caprylic alcohol, chloroform, carbon tetrachloride, toluene and kerosene; contacting the oil phase with alkali liquor to perform reverse extraction, and then performing second oil-water separation on the obtained mixed liquor to obtain a water phase; and calculating the content c0 of the corrosion and scale inhibitor contained in the water sample to be detected through the formula I. The method can improve the accuracy and precision of content determination of the corrosion and scale inhibitor, so that the concentration of the corrosion and scale inhibitor in a circulating water system is more favorably controlled.

Description

Technical Field

[0001] The present invention relates to the field of water treatment, and specifically to a method for determining the content of corrosion and scale inhibitors in a water sample and a method for controlling the concentration of corrosion and scale inhibitors in a circulating water system. Background Art

[0002] Scaling is a common problem in circulating water systems. The circulating water contains a large amount of ions. Due to the evaporation and concentration of the circulating water, the concentrations of metal ions such as Ca 2+ , Mg 2+ and anions such as CO3 2- , HCO3 - gradually increase, and when combined, they are prone to form calcium carbonate and magnesium carbonate precipitates. Scaling in a circulating water system may cause various hazards such as pipeline blockage, reduced heat transfer efficiency of heat exchangers, and under-scale corrosion, ultimately leading to an increase in the operating cost and a shortening of the lifespan of the system. Adding scale inhibitors is the most economical and effective method to delay scaling and ensure the long-term stable operation of the circulating cooling water system. High-phosphorus scale inhibitors containing phosphonic acid groups were first invented and widely used. However, the use of high-phosphorus scale inhibitors will cause the total phosphorus content in the discharged sewage to exceed the standard, resulting in eutrophication of water bodies. Therefore, at present, the research and use of phosphorus-free scale inhibitors have become a new trend. In actual industrial applications, in order to improve the corrosion inhibition effect while inhibiting scale, a small amount of phosphate or soluble zinc is generally added to the scale inhibitor formulation. However, calcium phosphate is insoluble in water, and soluble zinc is also prone to precipitation in circulating water. Therefore, while phosphorus-free scale inhibitors inhibit the formation of calcium carbonate and magnesium carbonate scale, they also need to have good functions of inhibiting calcium phosphate scale and zinc scale.

[0003] Among the commonly used existing phosphorus-free scale inhibitors, some polycarboxylic polymers have good performance in inhibiting calcium carbonate and magnesium carbonate scale. However, their performance in inhibiting calcium phosphate scale and zinc scale is poor. And scale inhibitors containing both carboxylic acid groups and sulfonic acid groups, such as AA / AMPS, AA / AHPS, AA / APES, AA / SA / SSS, etc. (the molecular formula of AA / AMPS is as follows: ), after adding a concentration of several milligrams per liter to several tens of milligrams per liter according to different circulating water qualities, have good effects on inhibiting calcium carbonate and magnesium scale, calcium phosphate, and zinc scale, and currently have become one of the most widely used scale inhibitors in circulating water systems.

[0004] Testing the concentration of scale inhibitors in circulating water is an important indicator for monitoring the quality of circulating water. By testing the concentration of scale inhibitors in circulating water, it can be judged whether additional dosing is needed in the system and how much the dosing amount is, so as to ensure the scale inhibition effect and lay a foundation for the automation and digital monitoring of circulating water plants. If the concentration of scale inhibitors in circulating water cannot be measured in a timely and accurate manner, it may result in poor scale inhibition effect, leading to the formation of various types of scale, ultimately affecting the maintenance and operation of the system and causing an increase in maintenance and treatment costs.

[0005] For phosphorus-containing scale inhibitors, the concentration of scale inhibitors in circulating water can be quickly monitored by testing the phosphorus content in the circulating water. For the determination of the concentration of non-phosphorus scale inhibitors in circulating water, currently, there are mainly fluorescence substance tracer method, amphoteric surfactant turbidimetry, pinacyanol chloride colorimetry, etc. Among them, if the fluorescent substance is only added to the agent by compounding method, its concentration cannot accurately represent the concentration of the agent itself; if the fluorescent substance is combined with the agent molecule, the cost of agent synthesis is relatively high. And the accuracy of amphoteric surfactant turbidimetry and pinacyanol chloride colorimetry is greatly affected by various ions (such as Ca 2+ , Na + , Cl - , SO4 2- etc.) in the water body.

[0006] In order to reduce the influence of various inorganic ions in water on the test of scale inhibitor concentration, Boak L S et al. (New Developments in the Analysis of Scale Inhibitors[J]. SPE production and operations, 2010, 25(4): p.533 - 544.) separated and enriched the scale inhibitor from circulating water or other industrial water by solid-phase extraction to achieve the purpose of eliminating the influence of various ions in the water body. The specific method is as follows: adjust the solution to low pH so that both carboxyl and sulfonic acid groups are protonated. Then, the organic macromolecules are retained on the solid-phase extraction column by solid-phase extraction. Then, wash the solid-phase extraction column with NaOH solution of known concentration, so that the protonated groups lose protons and become salts, which dissolve in water and are eluted. This process not only completes the enrichment of the agent, but also removes the inorganic ions in the water, which is beneficial to the accurate analysis of the agent concentration. However, in the actual application process, due to the strong polarity of the organic substances containing carboxyl and sulfonic acid groups and their high solubility in the aqueous phase, the recovery rate of the agent obtained by solid-phase extraction is relatively low, and the accuracy and repeatability are poor.

[0007] In summary, in the context of the wide use of non-phosphorus scale inhibitors, a better method for testing the content of scale inhibitors in water is needed to eliminate the influence of various ions in water on the test, overcome the disadvantages of poor accuracy and precision of existing methods, and thus achieve the precise control of the concentration of corrosion and scale inhibitors in the circulating water system. Summary of the Invention

[0008] The object of the present invention is to overcome the problems of poor accuracy and precision in the determination of the content of corrosion and scale inhibitors in water samples by existing methods, so as to achieve the precise control of the concentration of corrosion and scale inhibitors in the circulating water system.

[0009] To achieve the above object, a first aspect of the present invention provides a method for determining the content of corrosion and scale inhibitors in a water sample, the method comprising the following steps:

[0010] (1) Contact an extractant, a cosolvent and a water sample to be tested containing a corrosion and scale inhibitor for extraction, and then perform a first oil-water separation on the obtained mixture to obtain an oil phase; wherein, the corrosion and scale inhibitor is a polymer containing a sulfonic acid group; the extractant is a trialkyl tertiary amine, and the number of carbon atoms of the alkyl group in the trialkyl tertiary amine is 8-10; the cosolvent is at least one of n-octanol, chloroform, carbon tetrachloride, toluene and kerosene;

[0011] (2) Contact the oil phase with an alkali solution for back extraction, and then perform a second oil-water separation on the obtained mixture to obtain an aqueous phase;

[0012] (3) Calculate the content c0 of the corrosion and scale inhibitor contained in the water sample to be tested by formula I:

[0013]

[0014] wherein, c1 is the total S concentration of the aqueous phase, in mg / L; c2 is the organic S content of the corrosion and scale inhibitor; V1 is the volume of the aqueous phase, in L; V2 is the volume of the water sample to be tested, in L.

[0015] For phosphorus-containing scale inhibitors, the concentration of scale inhibitors in the water sample can be quickly monitored by measuring the phosphorus content in the water sample. For non-phosphorus scale inhibitors, especially non-phosphorus scale inhibitors containing sulfonic acid group polymers, the inventors of the present invention found during the research process that in order to exclude the influence of other ions or additives in the water, solid-phase extraction or liquid-liquid extraction is used to purify and enrich the non-phosphorus scale inhibitor, and measuring the S element concentration in the enriched aqueous phase is a better method for testing the concentration of the corrosion and scale inhibitor. However, due to the excessive polarity and high water solubility of the sulfonic acid group polymer, it is difficult to perform liquid-liquid extraction with ordinary organic solvents or solid-phase extraction using common SPE columns, thus making it difficult to accurately determine its content in the water sample.

[0016] To solve the above problems, the method provided by the present invention uses an organic weak base insoluble in water as an extractant in combination with a cosolvent for liquid-liquid extraction, which can effectively avoid the influence of various ions in the water sample on the measurement of the concentration of the corrosion and scale inhibitor, further increase the extraction ratio of the organic phase, and use a strong alkali solution for back extraction to return the extracted scale inhibitor to the aqueous phase, which is beneficial to the determination of its concentration while enriching it, and thus ensures high precision and high accuracy in the measurement of the concentration of the corrosion and scale inhibitor. The method provided by the present invention characterizes the scale inhibitor through the characteristic element (S element) in the corrosion and scale inhibitor molecule, and determines the content of the scale inhibitor by measuring the S element concentration, which can eliminate the influence of organic substances in the water, including other carboxylic acid polymers, on the concentration measurement.

[0017] The second aspect of the present invention provides a method for controlling the concentration of corrosion and scale inhibitors in a circulating water system. The control method includes:

[0018] Determine the content of the corrosion and scale inhibitor in the circulating water system according to the method described in the first aspect, and then control the concentration of the corrosion and scale inhibitor in the circulating water system to a target value according to the determination result.

[0019] Through the above technical solution, the method provided by the present invention for determining the content of the corrosion and scale inhibitor in the water sample can effectively eliminate the influence of various ions in the water body on the determination of the content of the corrosion and scale inhibitor, further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor, thereby being more conducive to controlling the concentration of the corrosion and scale inhibitor in the circulating water system, especially controlling the concentration of the phosphorus-free scale inhibitor in the circulating water system. In addition, the control method provided by the present invention is also conducive to ensuring the scale inhibition effect and reducing the maintenance and treatment costs of the system. Description of the Drawings

[0020] Figure 1 It is a linear relationship diagram of the scale inhibitor concentration and the organic sulfur concentration in the aqueous solution of Embodiment 1 of the present invention. Detailed Embodiments

[0021] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0022] In the present invention, unless otherwise stated, the room temperature means 25 ± 2 °C.

[0023] As described above, the first aspect of the present invention provides a method for determining the content of the corrosion and scale inhibitor in a water sample. The method includes the following steps:

[0024] (1) Contact an extractant, a cosolvent, and a water sample to be tested containing a corrosion and scale inhibitor for extraction, and then perform a first oil-water separation on the obtained mixed solution to obtain an oil phase; wherein, the corrosion and scale inhibitor is a polymer containing a sulfonic acid group; the extractant is a trialkyl tertiary amine, and the number of carbon atoms of the alkyl group in the trialkyl tertiary amine is 8-10; the cosolvent is at least one of n-octanol, chloroform, carbon tetrachloride, toluene, and kerosene;

[0025] (2) Contact the oil phase with an alkali solution for back extraction, and then perform a second oil-water separation on the obtained mixed solution to obtain an aqueous phase;

[0026] (3) Calculate the content c0 of the corrosion and scale inhibitor contained in the water sample to be measured through Formula I:

[0027]

[0028] Wherein, c1 is the total S concentration of the aqueous phase, with the unit of mg / L; c2 is the organic S content of the corrosion and scale inhibitor; V1 is the volume of the aqueous phase, with the unit of L; V2 is the volume of the water sample to be measured, with the unit of L.

[0029] During the research process, the inventors of the present invention found that through the extraction of the scale inhibitor polymer by an organic weak base and the back-extraction by a strong base solution, various ions (Ca 2+ 、Na + 、Cl - 、SO4 2- etc.) and various cationic surfactants in water can be eliminated, and their influence on the scale inhibitor concentration test can be removed. At the same time, the elimination of SO4 2- makes it possible to characterize the scale inhibitor concentration by measuring the S content, and can further exclude the influence of other S-free carboxylic acid anionic surfactants on the test.

[0030] According to some embodiments of the present invention, c2 is the organic S content of the corrosion and scale inhibitor, that is, the organic S content contained in the original corrosion and scale inhibitor added to the water sample. Preferably, the method for measuring the organic S content c2 of the corrosion and scale inhibitor includes the following steps:

[0031] (a) Provide n aqueous solutions containing the corrosion and scale inhibitor, where n ≮ 2, and in different aqueous solutions, the concentration of the corrosion and scale inhibitor is different, and the unit of the concentration is mg / L;

[0032] (b) Measure the concentration of SO4 2- in the n aqueous solutions respectively, with the unit of mg / L, and record them as S 1 无机 、S 2 无机 …S n 无机 in sequence; and measure the total S concentration of the n aqueous solutions respectively, with the unit of mg / L, and record them as S 1 总 、S 2 总 …S n 总 in sequence; Calculate the organic S concentration of the n aqueous solutions respectively through Formula II-1, Formula II-2…Formula II-n, and record them as S 1 有机 、S 2 有机 …S n有机 :

[0033] S 1 有机 = S 1 总 -S 1 无机 / 3 Formula II-1;

[0034] S 2 有机 = S 2 总 -S 2 无机 / 3 Formula II-2

[0035] …

[0036] S n 有机 = S n 总 -S n 无机 / 3 Formula II-n;

[0037] (c) Using the concentration of the corrosion and scale inhibitor in the n aqueous solutions as the abscissa and the organic S concentration in the n aqueous solutions as the ordinate for linear fitting, the obtained slope k is defined as the organic S content c2 of the corrosion and scale inhibitor. Adopting the above preferred implementation manner is beneficial to eliminating the influence of different organic S contents in the agents from different manufacturers and batches on the concentration test results. For the agents from the same manufacturer and the same batch, only one test is required.

[0038] According to some embodiments of the present invention, preferably, in step (a), in any of the aqueous solutions, the concentration of the corrosion and scale inhibitor is 20 - 200 mg / L.

[0039] According to some embodiments of the present invention, preferably, in step (b), the concentration of SO4 in the aqueous solution is measured by anion chromatography (IC). 2- of.

[0040] According to some embodiments of the present invention, preferably, in step (b), the total S concentration in the aqueous solution is measured by inductively coupled plasma optical emission spectrometry (ICP-OES) and / or atomic absorption spectrometry (AAS).

[0041] According to some embodiments of the present invention, in step (1), the extractant is a trialkyl tertiary amine, and the alkyl group in the trialkyl tertiary amine has 8 to 10 carbon atoms; the co-solvent is at least one of n-octanol, chloroform, carbon tetrachloride, toluene, and kerosene. The trialkyl tertiary amine is an organic weak base and can undergo an acid-base reaction with the scale inhibitor of the polycarboxylic acid sulfonic acid type, so that the pharmaceutical polymer enters the organic phase. When the extractant and the co-solvent are used in combination, while promoting the entry of the corrosion and scale inhibitor into the organic phase, it can also make the oil and water phases separate better, which is more conducive to the first oil-water separation.

[0042] According to some embodiments of the present invention, preferably, in step (1), the extractant is triisooctylamine.

[0043] According to some embodiments of the present invention, preferably, in step (1), the co-solvent is n-octanol.

[0044] Using the extractant and co-solvent of the above preferred embodiments is beneficial to further increase the extraction ratio of the organic phase, thereby increasing the recovery rate of the corrosion and scale inhibitor, and is beneficial to further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0045] According to some embodiments of the present invention, preferably, in step (1), the volume ratio of the amounts of the extractant and the co-solvent used is 1 - 9:1, preferably 1 - 4:1. Using the above preferred embodiments is beneficial to avoiding excessive dosage of the pharmaceutical while further increasing the extraction ratio of the organic phase, thereby increasing the recovery rate of the corrosion and scale inhibitor, and is beneficial to further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0046] According to some embodiments of the present invention, preferably, in step (1), the volume ratio of the total amount of the extractant and the co-solvent to the amount of the water sample to be measured is 1:1 - 5, preferably 1:1 - 3, and more preferably 1:1 - 2. Using the above preferred embodiments is beneficial to further increasing the extraction ratio of the organic phase, thereby increasing the recovery rate of the corrosion and scale inhibitor, and thus improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0047] According to some embodiments of the present invention, in step (1), the corrosion and scale inhibitor can be a phosphorus-containing scale inhibitor or a phosphorus-free scale inhibitor. The method provided by the present invention is particularly suitable for the determination of the content of the phosphorus-free scale inhibitor containing a sulfonic acid group polymer in a water sample.

[0048] According to some embodiments of the present invention, preferably, in step (1), the corrosion and scale inhibitor is a polymer containing carboxylic acid groups and sulfonic acid groups, preferably at least one of a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (AA / AMPS), a copolymer of acrylic acid and 3-allyloxy-2-hydroxy-1-propanesulfonate (AA / AHPS), a copolymer of acrylic acid and allyloxypolyoxyethylene sulfonate (AA / APES), a copolymer of acrylic acid-allyl sulfonate-styrene sulfonate (AA / SA / SSS), and a copolymer of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate (AA-AMPS-HPA).

[0049] According to some embodiments of the present invention, preferably, the water sample to be tested is circulating cooling water; in the circulating cooling water, the content of calcium ions is 50 - 800 mg / L, the content of chloride ions is 200 - 1200 mg / L, and the content of sulfate ions is 50 - 500 mg / L. The method provided by the present invention can still preferably measure the content of the corrosion and scale inhibitor in the water sample in the case where the water sample to be tested contains a high concentration of inorganic ions, and the recovery rate of the corrosion and scale inhibitor is between 90% and 110%. The method is particularly suitable for the determination of the concentration of the agent in actual circulating water, and the measurement precision is high.

[0050] According to some embodiments of the present invention, preferably, the pH value of the water sample to be tested is 4 - 2, preferably 3 - 2. Within the above range, as the pH value of the water sample to be tested decreases, the protonation degree of the carboxylic acid group and sulfonic acid group of the corrosion and scale inhibitor is higher, which is more conducive to the reaction between the scale inhibitor molecule and the extractant, and the extraction ratio of the organic phase increases accordingly. By adopting the above preferred embodiment, it is beneficial to further increase the extraction ratio of the organic phase, thereby improving the recovery rate of the corrosion and scale inhibitor, and finally improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0051] According to some embodiments of the present invention, preferably, the content of the corrosion and scale inhibitor contained in the water sample to be tested is 5 - 200 mg / L.

[0052] According to some embodiments of the present invention, preferably, in step (1), the contact method includes: mixing the extractant, the cosolvent, and the water sample to be tested containing the above corrosion and scale inhibitor; preferably, the mixing conditions include: the temperature is 20 - 30 °C, the rotation speed is 150 - 250 rpm, and the time is 0.5 - 2 h. There is no particular limitation on the mixing equipment, for example, it can be a conventional shaker, magnetic stirrer, etc.

[0053] According to some embodiments of the present invention, preferably, in step (2), the alkaline solution is an aqueous solution of NaOH and / or an aqueous solution of KOH. NaOH and KOH are stronger bases than trialkyl tertiary amines, which can react with the scale inhibitor polymer containing carboxyl groups and sulfonic acid groups in the organic phase to form corresponding carboxylates and sulfonates, so that the scale inhibitor is back-extracted into the aqueous phase, which is beneficial to improving the recovery rate of the corrosion and scale inhibitor and further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0054] According to some embodiments of the present invention, preferably, in step (2), the concentration of the alkaline solution is 1-5 g / L, preferably 2-5 g / L. Adopting the above preferred embodiment is beneficial to improving the recovery rate of the corrosion and scale inhibitor and further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0055] According to some embodiments of the present invention, preferably, in step (2), the volume ratio of the alkaline solution to the oil phase is 1:3-10, preferably 1:4-8. Adopting the above preferred embodiment is beneficial to improving the recovery rate of the corrosion and scale inhibitor and is beneficial to further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0056] According to some embodiments of the present invention, preferably, in step (2), the contact method includes: mixing the oil phase with the alkaline solution; preferably, the mixing conditions include: the temperature is 20-30 °C, the rotation speed is 150-250 rpm, and the time is 0.5-2 h. There is no particular limitation on the mixing equipment, for example, it can be a conventional shaker, magnetic stirrer, etc.

[0057] According to some embodiments of the present invention, preferably, in step (3), the total S concentration of the aqueous phase is measured by inductively coupled plasma emission spectrometry and / or atomic absorption spectrometry.

[0058] The second aspect of the present invention provides a method for controlling the concentration of the corrosion and scale inhibitor in a circulating water system, and the control method includes:

[0059] Determine the content of the corrosion and scale inhibitor in the circulating water system according to the method described in the first aspect, and then control the concentration of the corrosion and scale inhibitor in the circulating water system to the target value according to the measurement result.

[0060] According to some embodiments of the present invention, it is judged whether it is necessary to continue dosing in the circulating water system according to the measurement result, and the dosing amount is calculated through the difference between the target concentration and the actual concentration and the circulating water volume, so as to control the concentration of the corrosion and scale inhibitor in the circulating water system to the target value.

[0061] According to some embodiments of the present invention, the method for determining the content of the corrosion and scale inhibitor in the water sample can effectively eliminate the influence of various ions in the water body on the determination of the content of the corrosion and scale inhibitor, further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor, and thus being more conducive to controlling the concentration of the corrosion and scale inhibitor in the circulating water system, especially the concentration of the non-phosphorus scale inhibitor in the circulating water system. In addition, the control method is also conducive to ensuring the scale inhibition effect and reducing the maintenance and treatment costs of the system.

[0062] The present invention will be described in detail below through examples.

[0063] In the following examples, unless otherwise specified, the raw materials and instruments used are all commercially available products.

[0064] AA / AMPS was purchased from Shandong Taihe Science & Technology Co., Ltd., and the effective content was 30 wt%;

[0065] Anion chromatography (IC): The test was carried out by an anion chromatograph of model Metrohm Eco IC from Metrohm AG, Switzerland. The test conditions were as follows: using a Metrohm SUPP5-150 anion chromatography column (150 mm × 4.0 mm); the eluent was 1.0 mM NaHCO3 + 3.2 mM Na2CO3 (flow rate was 0.7 mL / min), and the sample injection volume was 20 μL;

[0066] Inductively coupled plasma optical emission spectrometry (ICP-OES): The test was carried out by an inductively coupled plasma optical emission spectrometer of model Optima8300 from Perkin Elmer, and the test wavelength was 180.73 nm.

[0067] Example 1

[0068] The method for determining the organic S content c2 of the corrosion and scale inhibitor (AA / AMPS) is as follows:

[0069] (a) Provide 4 aqueous solutions of the above corrosion and scale inhibitor, and the concentrations of the corrosion and scale inhibitor in the aqueous solutions are shown in Table 1 in turn;

[0070] (b) Respectively determine the concentration of SO4 2- in the above aqueous solutions by anion chromatography (IC), and record them as S 1 无机 , S 2 无机 , S 3 无机 , S 4 无机 in turn;

[0071] The total S concentration of the above aqueous solutions was measured by inductively coupled plasma optical emission spectrometry (ICP-OES), and was denoted as S 1 总 , S 2 总 , S 3 总 , S 4 总 ;

[0072] The organic S concentration of the above aqueous solutions was calculated by Formula II-1, Formula II-2, Formula II-3, and Formula II-4, and was denoted as S 1 有机 , S 2 有机 , S 3 有机 , S 4 有机 :

[0073] S 1 有机 = S 1 总 - S 1 无机 / 3 Formula II-1;

[0074] S 2 有机 = S 2 总 - S 2 无机 / 3 Formula II-2;

[0075] S 3 有机 = S 3 总 – S 3 无机 / 3 Formula II-3;

[0076] S 4 有机 = S 4 总 – S 4 无机 / 3 Formula II-4;

[0077] The specific data are shown in Table 1;

[0078] Table 1

[0079]

[0080] Note: The concentration of the corrosion and scale inhibitor * is the concentration of the corrosion and scale inhibitor in the aqueous solution of the corrosion and scale inhibitor.

[0081] (c) Using the concentration of the corrosion and scale inhibitor in the above aqueous solution (unit: mg / L) as the abscissa and the organic S concentration in the above aqueous solution (unit: mg / L) as the ordinate for linear fitting, the results are shown in Figure 1 , and it can be seen from the figure that the slope k obtained by linear fitting is 0.047, that is, the organic S content c2 of the above corrosion and scale inhibitor is 0.047.

[0082] The method for determining the content of the corrosion and scale inhibitor in the water sample is as follows:

[0083] (1) Contact the extractant (30 mL), the cosolvent, and the water sample to be tested containing the above corrosion and scale inhibitor for extraction, and then pour the obtained mixed solution into a separatory funnel and let it stand for the first oil-water separation to obtain the oil phase; where:

[0084] The water samples to be tested (a total of 5 groups, denoted as A1 - A5 in sequence) are all aqueous solutions obtained by mixing the above corrosion and scale inhibitor with deionized water, and their known concentrations are shown in Table 2; their pH values are all 2;

[0085] The extractant is triisooctylamine; the cosolvent is n-octanol;

[0086] The volume ratio of the extractant to the cosolvent is 1:1;

[0087] The total volume of the extractant and the cosolvent is in a volume ratio of 1:2 to the volume of the water sample to be tested;

[0088] The contact step is: Mix the extractant, the cosolvent, and the water sample to be tested containing the above corrosion and scale inhibitor in a shaker, and the mixing conditions are: temperature is room temperature, rotation speed is 200 rpm, and time is 1 h;

[0089] (2) Contact the above oil phase with the alkali solution for back extraction, and then perform the second oil-water separation on the obtained mixed solution to obtain the water phase; where:

[0090] The alkali solution is an aqueous NaOH solution with a concentration of 5 g / L;

[0091] The volume ratio of the alkali solution to the oil phase is 1:5;

[0092] The contact step is: Mix the above oil phase with the alkali solution in a shaker, and the mixing conditions are: temperature is room temperature, rotation speed is 200 rpm, and time is 1 h;

[0093] (3) Measure the total S concentration c1 of the above water phase by inductively coupled plasma optical emission spectrometry (ICP-OES), and calculate the content c0 of the corrosion and scale inhibitor in the above water sample to be tested through the following formula:

[0094]

[0095] Among them, c1 is the total S concentration in the aqueous phase, with the unit of mg / L; c2 is the organic S content of the corrosion and scale inhibitor; V1 is the volume of the aqueous phase, with the unit of L; V2 is the volume of the water sample to be measured, with the unit of L; the measurement results are shown in Table 2.

[0096] The recovery rate of the corrosion and scale inhibitor is calculated by the following formula, and the results are shown in Table 2:

[0097]

[0098] Table 2

[0099]

[0100] Note: Known concentration ** That is the known concentration of the corrosion and scale inhibitor in the water sample to be measured.

[0101] From the above results, it can be seen that the method provided by the present invention can accurately measure the content of the corrosion and scale inhibitor in the water sample, and the recovery rate of the corrosion and scale inhibitor is 95 - 105%, proving that this method has good accuracy under the conditions of the common reagent concentration in circulating water.

[0102] Analyzing the results of the water samples to be measured A2, A3, and A4 in the table, it is found that the standard deviation of the three repeated tests is 0.2, and its coefficient of variation is calculated by the following formula (the smaller the coefficient of variation, the better the repeatability of this method):

[0103]

[0104] The calculated coefficient of variation of the test results of the above three groups of water samples to be measured is 2%, which is less than 5%, proving that the method provided by the present invention has good repeatability and precision.

[0105] Example 2

[0106] Determine the organic S content c2 of the corrosion and scale inhibitor (AA / AMPS) according to the method of Example 1, which is 0.047;

[0107] Determine the content of the corrosion and scale inhibitor contained in the water sample according to the method of Example 1, the difference is:

[0108] The water samples to be measured (a total of 2 groups, denoted as A6 and A7 in sequence) contain NaCl, Na2SO4, CaCl2 and the above corrosion and scale inhibitor, and their compositions are shown in Table 3 respectively; their pH values are all 2;

[0109] The rest are the same; the measurement results are shown in Table 4.

[0110] Table 3

[0111] Water sample to be measured NaCl <![CDATA[Na2SO4]]> <![CDATA[Calcium chloride]]> AA / AMPS Unit mol / L mol / L mol / L mg / L A6 0.01 0.001 0.002 10 A7 0.03 0.003 0.008 10

[0112] Table 4

[0113]

[0114] From the above results, it can be seen that when the water sample to be tested contains a high concentration of inorganic ions, the method provided by the present invention can still better determine the content of the corrosion and scale inhibitor in the water sample, and the recovery rate of the corrosion and scale inhibitor is between 90% and 110%, proving that this method is applicable to the determination of the concentration of the agent in actual circulating water and has high determination precision.

[0115] Example 3

[0116] Perform extraction according to step (1) of Example 1, with the difference that:

[0117] In step (1), the water samples to be tested (a total of 3 groups, denoted as A8 - A10 in sequence) are all aqueous solutions obtained by mixing the corrosion and scale inhibitor AA / AMPS with deionized water, and their known concentration is 200 mg / L (SO4 2- concentration is 4.8 mg / L); their pH values are shown in Table 5 respectively;

[0118] The dosage of the extractant is 10 mL;

[0119] The total dosage of the extractant and the cosolvent is in a volume ratio of 1:1 to the volume of the water sample to be tested;

[0120] The rest are the same, obtaining the oil phase and the waste aqueous phase;

[0121] Test the total S concentration c4 of the above waste aqueous phase by ICP - OES, and calculate the organic phase extraction ratio of the corrosion and scale inhibitor AA / AMPS through the following formula:

[0122]

[0123] Among them, c3 is the known concentration of the corrosion and scale inhibitor in the water sample to be tested (unit: mg / L), c4 is the total S concentration of the waste aqueous phase (unit: mg / L), and c2 is the organic S content of the corrosion and scale inhibitor; the obtained results are shown in Table 5.

[0124] Table 5

[0125]

[0126] From the above results, it can be seen that as the pH value of the water sample to be measured decreases, the protonation degree of the carboxyl group and sulfonic acid group of the corrosion and scale inhibitor is higher, which is more conducive to the reaction between the scale inhibitor molecule and the extractant, and the extraction ratio of the organic phase increases accordingly. When pH = 2, the extraction ratio of the organic phase is as high as 98%. That is, when the pH value of the water sample to be measured is within the preferred range defined in this application, it is beneficial to further increase the extraction ratio of the organic phase, thereby improving the recovery rate of the corrosion and scale inhibitor, and ultimately improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0127] Example 4

[0128] Perform extraction according to step (1) of Example 1, with the difference that:

[0129] In step (1), the water samples to be measured (a total of 4 groups, denoted as A11 - A14 in sequence) are all aqueous solutions obtained by mixing the corrosion and scale inhibitor AA / AMPS with deionized water, and their known concentration is 200 mg / L (SO4 2- concentration is 4.8 mg / L); its pH = 2;

[0130] The dosages of the extractant and the cosolvent are shown in Table 6 respectively;

[0131] The volume ratio of the total dosage of the extractant and the cosolvent to the volume of the water sample to be measured is 1:1;

[0132] The rest are the same, obtaining an oil phase and a waste water phase;

[0133] Test the total S concentration c4 of the above waste water phase according to the method of Example 3, and calculate the extraction ratio of the corrosion and scale inhibitor AA / AMPS in the organic phase. The results are shown in Table 6.

[0134] Table 6

[0135]

[0136] From the above results, it can be seen that when the volume ratio of the dosages of the extractant and the cosolvent is within the preferred range of the present invention, the extraction ratio of the organic phase is not less than 95%, which is beneficial to further increase the extraction ratio of the organic phase, thereby improving the recovery rate of the corrosion and scale inhibitor, and is beneficial to further improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0137] Example 5

[0138] Perform extraction according to step (1) of Example 1, with the difference that:

[0139] In step (1), the water samples to be measured (a total of 4 groups, denoted as A15 - A17 in sequence) are all aqueous solutions obtained by mixing the corrosion and scale inhibitor AA / AMPS with deionized water, and their known concentration is 200 mg / L (SO4 2-The concentration is 4.8 mg / L); its pH = 2;

[0140] The dosages of the extractant, cosolvent and water sample to be measured are shown in Table 7 respectively;

[0141] The rest are the same, obtaining an oil phase and a waste water phase;

[0142] Test the total S concentration c4 of the above waste water phase according to the method of Example 3, and calculate the organic phase extraction ratio of the corrosion and scale inhibitor AA / AMPS. The results are shown in Table 7.

[0143] Table 7

[0144]

[0145] From the above results, it can be seen that when the volume ratio of the total dosage of the extractant and cosolvent to the dosage of the water sample to be measured is within the preferred range of the present invention, it is beneficial to further increase the organic phase extraction ratio, thereby increasing the recovery rate of the corrosion and scale inhibitor and improving the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0146] Example 6

[0147] Determine the organic S content c2 of the corrosion and scale inhibitor (AA / AMPS) according to the method of Example 1, which is 0.047;

[0148] Determine the content of the corrosion and scale inhibitor contained in the water sample according to the method of Example 1, except that:

[0149] In step (1), the water samples to be measured (a total of 4 groups, denoted as A18 - A21 in sequence) are all aqueous solutions obtained by mixing the corrosion and scale inhibitor AA / AMPS with deionized water, with a known concentration of 40 mg / L; its pH = 2; the dosages of the extractant, cosolvent and water sample to be measured are shown in Table 8 respectively; the rest are the same, obtaining an oil phase;

[0150] In step (2), the dosage of the lye is shown in Table 8; the rest are the same, obtaining an aqueous phase;

[0151] Step (3) is the same as that in Example 1, obtaining the content c0 of the corrosion and scale inhibitor contained in the water sample to be measured and the recovery rate of the corrosion and scale inhibitor. The results are shown in Table 8.

[0152] Table 8

[0153]

[0154] From the above results, it can be seen that when the volume ratio of the total dosage of the extractant and cosolvent to the dosage of the water sample to be measured is within the preferred range of the present invention, it is beneficial to further increase the recovery rate of the corrosion and scale inhibitor and improve the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0155] Example 7

[0156] The organic S content c2 of the corrosion and scale inhibitor (AA / AMPS) was determined according to the method of Example 1, which was 0.047;

[0157] The content of the corrosion and scale inhibitor in the water sample was determined according to the method of Example 1, except that:

[0158] In step (1), the water samples to be tested (a total of 4 groups, denoted as A22 - A25 in sequence) were all aqueous solutions obtained by mixing the corrosion and scale inhibitor AA / AMPS with deionized water, with a known concentration of 40 mg / L; the pH = 2;

[0159] The dosage of the extractant was 50 mL;

[0160] The volume ratio of the total dosage of the extractant and the cosolvent to the volume of the water sample to be tested was 1:1;

[0161] The rest were the same, and the oil phase was obtained;

[0162] In step (2), the concentration of the alkali solution is shown in Table 9; the volume ratio of the alkali solution to the oil phase was 1:10;

[0163] The rest were the same, and the water phase was obtained;

[0164] Step (3) was the same as in Example 1, and the content c0 of the corrosion and scale inhibitor in the water sample to be tested and the recovery rate of the corrosion and scale inhibitor were obtained. The results are shown in Table 9.

[0165] Table 9

[0166]

[0167] From the above results, it can be seen that when the concentration of the alkali solution is within the preferred range of the present invention, it is beneficial to further improve the recovery rate of the corrosion and scale inhibitor, as well as the accuracy and precision of the determination of the content of the corrosion and scale inhibitor in the water sample.

[0168] Comparative Example 1

[0169] The organic S content c2 of the corrosion and scale inhibitor (AA / AMPS) was determined according to the method of Example 1, which was 0.047;

[0170] The content of the corrosion and scale inhibitor in the water sample was determined according to the method of Example 1, except that:

[0171] Replace steps (1) and (2) of Example 1 with the solid-phase extraction method disclosed in the prior art (Boak L S et al., New Developments in the Analysis of Scale Inhibitors [J]. SPE production and operations, 2010, 25(4): p. 533-544.) as follows:

[0172] (1) Acidify the water samples to be measured (a total of 3 groups, the types, known concentrations, and volumes of the corrosion and scale inhibitors they contain are the same as those of A2 - A4 in Example 1, and are denoted as D1 - D3 in sequence) to pH = 2;

[0173] Activate the NH2 amino SPE solid-phase extraction column (loading capacity 1 g) with 5 mL of methanol; then pass 10 mL of deionized water through the above solid-phase extraction column; then pass 5 mL of hydrochloric acid solution with a concentration of 0.01 mol / L through the above solid-phase extraction column;

[0174] Pass the acidified water samples to be measured through the above solid-phase extraction column;

[0175] (2) Elute the above solid-phase extraction column with 12 mL of NaOH solution with a concentration of 0.1 mol / L, and the obtained eluate is the aqueous phase;

[0176] (3) Measure the total S concentration c1 of the above aqueous phase according to step (3) of Example 1, and calculate the content c0 of the corrosion and scale inhibitor in the water samples to be measured through Equation I; the results are shown in Table 10.

[0177] Table 10

[0178]

[0179] Note: Known concentration ** That is the known concentration of the corrosion and scale inhibitor in the water samples to be measured.

[0180] From the above results and the comparison between Example 1 and Comparative Example 1, it can be seen that the recovery rate of the corrosion and scale inhibitor in Comparative Example 1 is lower than 80%, and the accuracy of the solid-phase extraction method in Comparative Example 1 is lower than that of Example 1 of the present invention. And the standard deviation of the three parallel tests in Comparative Example 1 is 0.76, and the coefficient of variation is 10.6%, which is greater than 5%. The method provided by the present invention has better repeatability, measurement accuracy, and precision, and a higher recovery rate of the corrosion and scale inhibitor.

[0181] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including the combination of each technical feature in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for determining the content of corrosion and scale inhibitor in a water sample, the method comprising the following steps: (1) Contact the extractant, cosolvent and the water sample to be tested containing corrosion and scale inhibitors for extraction, and then perform a first oil-water separation on the obtained mixed solution to obtain an oil phase; wherein, The corrosion and scale inhibitor is a polymer containing a sulfonic acid group; the extractant is a trialkyl tertiary amine, and the number of carbon atoms in the alkyl group of the trialkyl tertiary amine is 8-10; the cosolvent is at least one of n-octanol, chloroform, carbon tetrachloride, toluene and kerosene; (2) Contact the oil phase with an alkali solution for back extraction, and then perform a second oil-water separation on the obtained mixed solution to obtain an aqueous phase; (3) Calculate the content c0 of the corrosion and scale inhibitor contained in the water sample to be measured by formula I: Wherein, c1 is the total S concentration of the aqueous phase, with the unit of mg / L; c2 is the organic S content of the corrosion and scale inhibitor; V1 is the volume of the aqueous phase, with the unit of L; V2 is the volume of the water sample to be measured, with the unit of L.

2. The method according to claim 1, wherein, The method for determining the organic S content c2 of the corrosion and scale inhibitor comprises the following steps: (a) Provide n aqueous solutions containing the corrosion and scale inhibitor, n≮2, and in different aqueous solutions, the concentrations of the corrosion and scale inhibitor are different, and the unit of the concentration is mg / L; (b) Measure the concentration of SO4 in each of the n aqueous solutions, in mg / L, and denote them as S 2- in sequence, and measure the total S concentration in each of the n aqueous solutions, in mg / L, and denote them as S 1 无机 、S 2 无机 …S n 无机 ; and calculate the organic S concentration in each of the n aqueous solutions respectively through Formula II-1, Formula II-2... Formula II-n, and denote them as S 1 总 、S 2 总 …S n 总 ; as follows: 1 有机 、S 2 有机 …S n 有机 : S 1 有机 = S 1 总 -S 1 无机 / 3 Formula II-1; S 2 有机 = S 2 总 -S 2 无机 / 3 Formula II-2 … S n 有机 = S n 总 -S n 无机 / 3 Formula II-n; (c) Perform linear fitting with the concentration of the corrosion and scale inhibitor in the n aqueous solutions as the abscissa and the organic S concentration in the n aqueous solutions as the ordinate, and the obtained slope k is defined as the organic S content c2 of the corrosion and scale inhibitor.

3. The method according to claim 2, wherein, In step (a), in any of the aqueous solutions, the concentration of the corrosion and scale inhibitor is 20-200 mg / L.

4. The method according to any one of claims 1-3, wherein, In step (b), the concentration of SO4 in the aqueous solution is determined by anion chromatography. 2- of; Preferably, the total S concentration of the aqueous solution is determined by inductively coupled plasma emission spectrometry and / or atomic absorption spectrometry.

5. The method according to any one of claims 1 to 4, wherein In step (1), the extractant is triisooctylamine; the cosolvent is n-octanol; Preferably, in step (1), the volume ratio of the amounts of the extractant and the cosolvent used is 1-9:1, preferably 1-4:

1.

6. The method according to any one of claims 1-5, wherein, In step (1), the total amount of the extractant and the cosolvent used and the amount of the water sample to be measured have a volume ratio of 1:1-5, preferably 1:1-3, more preferably 1:1-2.

7. The method according to any one of claims 1-6, wherein, In step (1), the corrosion and scale inhibitor is a polymer containing a carboxylic acid group and a sulfonic acid group, preferably at least one of a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, a copolymer of acrylic acid and 3-allyloxy-2-hydroxy-1-propanesulfonate, a copolymer of acrylic acid and allyloxypolyoxyethylene sulfonate, a copolymer of acrylic acid-allyl sulfonate-styrene sulfonate, and a copolymer of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and hydroxypropyl acrylate; Preferably, the water sample to be measured is circulating cooling water; in the circulating cooling water, the content of calcium ions is 50-800 mg / L, the content of chloride ions is 200-1200 mg / L, and the content of sulfate ions is 50-500 mg / L; Preferably, the pH value of the water sample to be measured is 4-2, preferably 3-2; Preferably, the content of the corrosion and scale inhibitor contained in the water sample to be measured is 5-200 mg / L.

8. The method according to any one of claims 1-7, wherein, In step (2), the alkali solution is an aqueous solution of NaOH and / or an aqueous solution of KOH; Preferably, the concentration of the alkali solution is 1-5 g / L, preferably 2-5 g / L.

9. The method according to any one of claims 1-8, wherein, In step (2), the volume ratio of the lye to the oil phase is 1:3 - 10, preferably 1:4 - 8.

10. The method according to any one of claims 1-9, wherein, In step (3), the total S concentration of the aqueous phase is determined by inductively coupled plasma emission spectrometry and / or atomic absorption spectrometry.

11. A method for controlling the concentration of corrosion and scale inhibitors in a circulating water system, the control method comprising: Determine the content of the corrosion and scale inhibitor in the circulating water system according to the method described in any one of claims 1 - 10, and then control the concentration of the corrosion and scale inhibitor in the circulating water system to the target value according to the measurement result.

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