Method for manually detecting chlorine ion content in gas water

Abstract

The invention discloses a method for manually detecting chlorine ion content in gas water. The method comprises the following steps: acquiring to-be-detected gas with a certain volume; introducing the coal gas to be detected into a potassium hydroxide solution until no new precipitate is generated; filtering by using quick quantitative filter paper until the water is clear and has no obvious color; transferring the filtered liquid into a 250mL conical flask, adding two drops of phenolphthalein indicator, and adjusting the pH value by using a nitric acid solution until the pH value is just changed to be colorless from red; and adding a potassium chromate indicator, and titrating with a silver nitrate standard titration solution until brick red appears. Through the systematic pretreatment and manual titration steps, the chlorine ion content in the gas water can be rapidly, accurately and reliably measured; the time of the whole process is controlled within 30 minutes from sampling to titration completion; the pretreatment and determination time required by traditional manual titration is greatly shortened.

Description

Technical Field

[0001] The invention relates to the technical field of chloride ion content detection methods, in particular to a method for manually detecting the chloride ion content in coal gas water. Background Art

[0002] Chloride ions are a harmful element in gas steam water. The main harm of chloride ions to pipelines is that they promote pipeline corrosion and cracking, leading to leakage. Chloride ions will be adsorbed on the metal surface, hindering the formation and regeneration of oxide film, increasing the electrical conductivity of the metal surface, thereby accelerating the corrosion of the metal and the destruction of the oxide film. In addition, chloride ions can also form complexes with other substances. Most complexes are highly active or highly corrosive, further accelerating the corrosion process of the metal. In the process of manual detection of chloride ions, the titration endpoint may be premature or there will be no titration endpoint at all. The application of this invention can not only shield the influence of interfering ions, but also improve the detection efficiency, providing a faster detection method for the detection of chloride ions in gas pipeline steam water. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for manually detecting the chloride ion content in coal gas water.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a method for manually detecting the chloride ion content in coal gas water, comprising the following steps:

[0005] S1: Obtain a certain volume of gas to be tested;

[0006] S2: Pass the gas to be tested into the potassium hydroxide solution until no new precipitate is formed;

[0007] S3: Filter with rapid quantitative filter paper until the water is clear and has no obvious color;

[0008] S4: Pipette the filtered liquid into a 250 mL conical flask, add two drops of phenolphthalein indicator, and adjust the pH with nitric acid solution until the red color just turns colorless.

[0009] S5: Add potassium chromate indicator and titrate with silver nitrate standard solution until brick red appears.

[0010] As a further improvement of the present invention: the concentration of the potassium hydroxide solution in step S2 is 200 g / L.

[0011] As a further improvement of the present invention, the potassium hydroxide solution in step S2 is prepared as follows: 20.0 g of KOH solid is weighed and dissolved in approximately 80 mL of distilled water. After complete dissolution, the volume is adjusted to 100 mL. Shake well before use to check that the solution is not significantly turbid.

[0012] As a further improvement of the present invention: in step S2, the reaction mixture is allowed to stand for 5 minutes.

[0013] As a further improvement of the present invention: the concentration of the phenolphthalein indicator in step S4 is 10 g / L.

[0014] As a further improvement of the present invention: the nitric acid solution in step S4 is a (1+2) nitric acid solution, and 98% concentrated nitric acid is mixed with distilled water in a volume ratio of 1:2: first take 33 mL of concentrated nitric acid, carefully and slowly add 67 mL of distilled water, mix and set aside.

[0015] As a further improvement of the present invention: the concentration of the potassium chromate indicator in step S5 is 50 g / L.

[0016] As a further improvement of the present invention: the amount of potassium chromate added in step S5 is 1.0 mL.

[0017] As a further improvement of the present invention: in step S5, the solution is titrated until a brick-red precipitate appears that lasts for 30 seconds, and the volume V3 of AgNO3 consumed is recorded.

[0018] As a further improvement of the present invention: wherein, the chlorine content is calculated as follows:

[0019]

[0020] Where V0 is the volume of the blank consumed in pure water without adding a sample. A is the AgNO3 concentration, and the sample volume is 50 mL.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Using high concentration KOH precipitation method, Zn 2+ The combination of selective precipitation and pH adjustment-EDTA masking effectively removes Fe 3+ / Fe 2+ Mg 2+ 、Al 3+ 、S 2- 、CO3 2- Various interfering ions such as + The influence of titration endpoint and indicator color development;

[0023] (2) All pretreatment reagents and titration reagents can be prepared on-site or used in conjunction with each other, without the need for complex instrument pretreatment; the entire process only requires four steps: filtration, pH adjustment, indicator addition, and titration;

[0024] (3) From sampling to completion of titration, the entire process time is controlled within 30 minutes; the standing and filtration in the pretreatment stage takes about 10–15 minutes, and the titration and pH adjustment stage takes about 10 minutes, which greatly shortens the pretreatment and measurement time required for traditional manual titration.

[0025] (4) The selected precipitants and masking agents have good removal effects on most common interfering ions; the titration conditions are universally applicable and suitable for gas water samples of different sources and varying compositional complexity

[0026] Through systematic pretreatment and manual titration steps, the chloride ion content in gas water can be determined quickly, accurately and reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to illustrate the technical solution more clearly, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] Chloride ions in gas steam water are the main hazard to pipelines. They promote pipeline corrosion and cracking, which is the main cause of leakage. Chloride ions are adsorbed in the pipeline, hinder the formation of oxide film, increase metal conductivity, and can generate highly corrosive complexes, accelerating pipeline corrosion and cracking, causing leakage risks. Therefore, the chloride ion content in gas water must be accurately monitored. Gas steam water often contains high concentrations of iron (Fe 3+ / Fe 2+ ), magnesium (Mg 2+ ), aluminum (Al 3+ ), carbonate (CO3 2- / HCO3 - ), sulfide (S 2- / HS 2- ) and other heavy metal ions, these components react with the chloride ion determination reagent to form precipitates or complexes, which seriously interfere with the subsequent titration process. In the traditional silver nitrate-potassium chromate (Mohr) method, interfering ions will consume or shield Ag + With Cl - The reaction endpoint of the titration may be advanced, delayed or even disappear, resulting in an inability to interpret or a huge deviation.

[0032] Drawing on similar water quality testing methods, manual water quality testing of chloride ions mostly uses silver nitrate titration, which utilizes the color reaction of potassium chromate on chloride ions and uses a standard silver nitrate solution to titrate the water to be tested. The chloride ion content is determined based on the final titration endpoint reading.

[0033] In order to solve the above problems, the present invention provides a method for manually detecting the chloride ion content in coal gas water, comprising the following steps:

[0034] S1: Obtain a certain volume of gas to be tested;

[0035] S2: Pass the gas to be tested into the potassium hydroxide solution until no new precipitate is formed;

[0036] S3: Filter with rapid quantitative filter paper until the water is clear and has no obvious color;

[0037] S4: Pipette the filtered liquid into a 250 mL conical flask, add two drops of phenolphthalein indicator, and adjust the pH with nitric acid solution until the red color just turns colorless.

[0038] S5: Add potassium chromate indicator and titrate with silver nitrate standard solution until brick red appears.

[0039] The combination of efficient interference removal and simplified operation not only greatly improves the accuracy of chloride ion determination in gas and water, but also shortens the detection time. It has the dual advantages of being suitable for on-site rapid detection and routine laboratory application.

[0040] As an embodiment of the present invention, the concentration of the potassium hydroxide solution in step S2 is 200 g / L. The potassium hydroxide solution in step S2 is prepared as follows: 20.0 g of KOH solid is weighed and dissolved in approximately 80 mL of distilled water. After complete dissolution, the volume is adjusted to 100 mL. Shake well before use to check that the solution is not significantly turbid. The reaction mixture in step S2 is allowed to stand for 5 minutes.

[0041] High concentration of KOH provides sufficient OH-, which can quickly react with Fe in gas water samples. 3+ 、Fe 2+ 、Al 3+ Mg 2+ The corresponding hydroxide precipitates are formed by cations such as Fe(OH)3, Al(OH)3, Mg(OH)2, etc., thereby efficiently removing these metal ions that have a significant interfering effect on chloride ion titration; the solution concentration is accurate and stable by clarifying the ratio, which is convenient for experimenters to repeat operations and obtain consistent treatment effects; shake well before use and check for obvious turbidity to avoid crystallization of KOH solution after moisture absorption or mixing with impurities, which may cause a decrease in reaction efficiency, thereby ensuring the stability of the reaction system and the treatment effect.

[0042] As an embodiment of the present invention, the concentration of the phenolphthalein indicator in step S4 is 10 g / L. The nitric acid solution in step S4 is a (1+2) nitric acid solution, which is prepared by mixing 98% concentrated nitric acid with distilled water in a volume ratio of 1:2: first taking 33 mL of concentrated nitric acid, carefully and slowly adding 67 mL of distilled water, and mixing for later use.

[0043] The phenolphthalein indicator concentration is 10 g / L. This high concentration allows for rapid color development with even slight pH changes, resulting in a clear, sharp, and intense endpoint signal from colorless to pink during the titration. The (1+2) nitric acid solution, precisely formulated to maintain a moderate acidity, effectively neutralizes residual alkali from the previous step while preventing excessive discoloration of the indicator or system disturbance due to excessive acidity. This optimal acidity range adjusts the solution pH to the optimal range for the Mohr method (≈6.8–7.2). Phenolphthalein develops color at pH ≈ 8.3 and completely fades at around pH ≈ 7. This clear "colored-to-colorless" transition range, perfectly matched to the acidity of the (1+2) nitric acid solution, effectively prevents endpoint drift caused by excessive or insufficient pH, significantly improving the precise location and quantitative accuracy of the chloride titration endpoint.

[0044] As an embodiment of the present invention, in step S5, the concentration of potassium chromate indicator is 50g / L. In step S5, the amount of potassium chromate added is 1.0mL. Step S5 includes adding 1.0mL of 50g / LK2CrO4 solution to 50mL of solution adjusted to pH, oscillating evenly until the solution is light yellow; placing a burette with a prepared AgNO3 standard solution, slowly adding AgNO3 dropwise, titrating until the solution shows a brick-red precipitate (Ag2CrO4) that lasts for 30s, and recording the consumed AgNO3 volume V3 (mL).

[0045] As an embodiment of the present invention, step S5 further includes performing a titration in pure water without adding a sample in the same process, and recording the blank consumption volume V0 for correction.

[0046] As an embodiment of the present invention, the chlorine content is calculated as follows:

[0047]

[0048] Where V0 is the volume of the blank consumed in pure water without adding a sample. A is the AgNO3 concentration, and the sample volume is 50 mL.

[0049] As a specific embodiment of the present invention, the following steps are included:

[0050] S1: Obtain a certain volume of gas to be tested;

[0051] S2: Pass the gas to be tested into 200g / L potassium hydroxide solution until no new precipitate is formed;

[0052] S3: Filter with rapid quantitative filter paper until the water is clear and has no obvious color;

[0053] S4: Pipette the filtered liquid into a 250 mL conical flask, add two drops of 10 g / L phenolphthalein indicator, and adjust the pH with (1+2) nitric acid solution until the red color just turns colorless;

[0054] S5: Add 1.0 mL of 50 g / L potassium chromate indicator and titrate with silver nitrate standard solution until brick red appears. At the same time, perform a blank test.

[0055] Directly passing coal gas into a high-concentration (200 g / L) KOH solution not only completely absorbs chloride in the gas and particulate phases to form Cl-, but the strong alkaline environment also causes residual H2S, CO2, and other gases to precipitate as corresponding hydroxides or carbonates, completely eliminating gas-phase interference. Filtration with rapid quantitative filter paper until the filtrate is clear and colorless removes all generated precipitates and suspended impurities, providing a clean chemical environment for subsequent indicator color development and endpoint determination, preventing turbidity or particulates from obscuring the endpoint color. In a 250 mL conical flask, two drops of 10 g / L phenolphthalein indicator combined with (1+2) nitric acid solution are used to adjust the pH of the solution from a weakly alkaline (pink) to a precisely neutral (colorless) pH, ensuring the optimal pH (≈7) for the Mohr titration and preventing the influence of acid-base deviation on endpoint color development. After adding 1.0 mL of 50 g / L K2CrO4 indicator, AgNO3 is titrated until a brick-red Ag2CrO4 precipitate appears, indicating the endpoint. Perform blank titration experiment to deduct trace Ag in the indicator, solvent and other systems. + Consumption, further correct the measured value to ensure the authenticity and comparability of the results.

[0056] The main functions of the present invention are:

[0057] The gas-water to be tested is passed through a high-concentration (200g / L) KOH solution to achieve efficient gas-liquid absorption. It is then filtered through a rapid quantitative filter paper until clear. The pH is precisely adjusted using phenolphthalein / (1+2) nitric acid and titrated using potassium chromate / Mohr method. Chloride ion quantification is achieved at the brick-red endpoint, supplemented by blank correction. The entire process requires only five steps and can be completed within 30 minutes, completely removing H2S, CO2, and Fe 3 + / Fe 2+ Mg2 + It can eliminate multiple interferences such as HCl and HCl, and realize sensitive, stable and accurate endpoint judgment at the optimal pH. The method is simple, reproducible and suitable for on-site rapid detection and routine laboratory analysis.

[0058] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method of the present invention and its core ideas. The above are only preferred implementation methods of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of the present invention.

[0059] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical solutions and technical concepts of the present invention without creative mental work, and all of them fall within the scope of protection of the present invention.

Claims

1. A method for manually detecting the chloride ion content in gas water, characterized in that: The following steps are involved: S1: Obtain a certain volume of gas to be tested; S2: Pass the gas to be tested into the potassium hydroxide solution until no new precipitate is formed; S3: Filter with rapid quantitative filter paper until the water is clear and has no obvious color; S4: Pipette the filtered liquid into a 250 mL conical flask, add two drops of phenolphthalein indicator, and adjust the pH with nitric acid solution until the red color just turns colorless. S5: Add potassium chromate indicator and titrate with silver nitrate standard solution until brick red appears.

2. A method for manually detecting chloride ion content in gas water according to claim 1, characterized in that: The concentration of the potassium hydroxide solution in step S2 is 200 g / L.

3. A method for manually detecting chloride ion content in gas water according to claim 2, characterized in that: In step S2, the reaction mixture was allowed to stand for 5 minutes.

4. A method for manually detecting chloride ion content in gas water according to claim 1, characterized in that: The concentration of the phenolphthalein indicator in step S4 is 10 g / L.

5. A method for manually detecting chloride ion content in gas water according to claim 1, characterized in that: The concentration of the potassium chromate indicator in step S5 is 50 g / L.

6. A method for manually detecting chloride ion content in gas water according to claim 5, characterized in that: The amount of potassium chromate added in step S5 is 1.0 mL.

7. A method for manually detecting chloride ion content in gas water according to claim 6, characterized in that: In step S5, the solution is titrated until a brick-red precipitate appears that lasts for 30 seconds, and the volume V3 of AgNO3 consumed is recorded.

8. A method for manually detecting chloride ion content in gas water according to claim 7, characterized in that: in, The chlorine content is calculated as follows: Where V0 is a titration in pure water without adding sample, and the blank consumption volume V0 is recorded; C A is the AgNO3 concentration, and the sample volume is 50 mL.

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