Method for measuring COD (Chemical Oxygen Demand) of high chloride ion wastewater

Abstract

The invention discloses a high chloride ion wastewater COD (Chemical Oxygen Demand) determination method which comprises the following steps: preparing silver nitrate standard solutions with different concentrations according to the chloride ion concentration in high chloride ion wastewater; taking a high chloride ion wastewater sample, and titrating with a silver nitrate standard solution until brick-red precipitate is generated; filtering the titrated water sample, metering the volume of the filtrate after filtration, and calculating the dilution ratio N according to the volume of the filtrate, N = the volume of the filtrate / the sampling volume of the chloride ion wastewater sample; preparing a COD (Chemical Oxygen Demand) digestion prefabricated reagent, and mixing a potassium dichromate standard solution with a sulfuric acid-silver sulfate solution; and uniformly mixing the filtrate with a COD digestion prefabricated reagent, carrying out heating digestion, cooling to obtain a digestion solution, measuring the COD measurement value of the digestion solution, and calculating the COD of the high chloride ion wastewater. The COD of the water sample can be directly measured after preliminary simple treatment, a masking agent mercury sulfate is avoided, use of the mercury sulfate is saved, and errors are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of water treatment, and in particular to a method for determining the COD of high chloride ion wastewater. Background Art

[0002] Chemical oxygen demand (COD) is one of the important indicators for water quality detection and evaluation of the degree of water pollution. Therefore, the accuracy of chemical oxygen demand detection is particularly important. At present, the chemical oxygen demand of water quality is usually detected in accordance with the provisions of HJ828-2017 "Determination of Chemical Oxygen Demand of Water Quality by Dichromate Method" or HJT 399-2007 "Determination of Chemical Oxygen Demand of Water Quality by Rapid Digestion Spectrophotometry". The principle is: add a known amount of potassium dichromate solution to the water sample, use mercuric sulfate as a chloride ion masking agent, use sulfuric acid-silver sulfate as a catalyst, heat reflux or high temperature digestion, and then use titration or spectrophotometry to determine the COD value. Chloride ions are the biggest interfering component in COD detection. Mercury sulfate is usually used to mask chloride ions, and the maximum masked chloride ion concentration is 4000 mg / L. However, for water samples with high chloride ion concentration and low COD, the water samples can only be diluted to ensure that the chloride ion concentration is within the masking range, which affects the accuracy of the test results. In addition, mercury sulfate is highly corrosive and toxic, and there are great safety risks during use, and the cost of waste liquid treatment is high. Summary of the invention

[0003] Based on this, it is necessary to provide a method for determining COD of high chloride ion wastewater. The method for determining COD of high chloride ion wastewater of the present invention can directly determine COD of water samples after preliminary simple treatment, avoiding the re-addition of masking agent mercuric sulfate, saving the use of mercuric sulfate, and reducing the error caused by diluting the water sample to determine COD.

[0004] An embodiment of the present application provides a method for determining the COD of high chloride ion wastewater.

[0005] A method for measuring COD of high chloride ion wastewater comprises the following steps:

[0006] According to the chloride ion concentration in the high chloride ion wastewater, prepare silver nitrate standard solutions of different concentrations; take a high chloride ion wastewater sample according to the sampling volume, and titrate it with the silver nitrate standard solution until a large amount of brick red precipitate is produced; filter the titrated water sample until the water sample is clear and transparent, measure the volume of the filtrate after filtration, and calculate the dilution multiple N according to the filtrate volume, N=filtrate volume / sampling volume of the chloride ion wastewater sample;

[0007] Prepare the COD digestion pre-made reagent, mix the potassium dichromate standard solution with the sulfuric acid-silver sulfate solution;

[0008] Take the filtrate and mix it with the pre-made COD digestion reagent, heat it for digestion, cool it to get the digestion solution, measure the COD value of the digestion solution at 600nm, and calculate the COD of high chloride ion wastewater = COD measured value × dilution factor N.

[0009] In some embodiments, during filtration, the titrated water sample is filtered through a slow-speed filter paper until the water sample becomes clear and transparent.

[0010] In some of the embodiments, the COD digestion prefabricated reagent is configured, including configuring a high-concentration COD digestion prefabricated reagent, and mixing a 0.5 mol / L potassium dichromate standard solution and a 10 g / L sulfuric acid-silver sulfate solution in a volume ratio of 1:5 and storing them for standby use.

[0011] In some of the embodiments, the high concentration COD digestion prefabricated reagent is used for COD determination in the range of 20 mg / L to 1000 mg / L.

[0012] In some of the embodiments, the preparation of the COD digestion prefabricated reagent includes preparing a low-concentration COD digestion prefabricated reagent, wherein a 0.25 mol / L potassium dichromate standard solution and a 10 g / L sulfuric acid-silver sulfate solution are mixed in a volume ratio of 1:5 and stored for standby use.

[0013] In some of the embodiments, the low concentration COD digestion prefabricated reagent is used for COD determination in the range of 0 mg / L to 150 mg / L.

[0014] In some of the embodiments, the volume ratio of the filtrate and the COD digestion prefabricated reagent when mixed is 2 mL: (5 mL~6 mL).

[0015] In some embodiments, the heating digestion is performed at 160° C. to 165° C. for at least 20 min.

[0016] In some embodiments, the cooling temperature is 20°C to 30°C.

[0017] In some of the embodiments, when a high chloride ion wastewater sample is titrated with a silver nitrate standard solution, the sampling volume of the chloride ion wastewater sample is 10 mL to 20 mL.

[0018] In the above-mentioned method for determining COD of high-chloride ion wastewater, the chloride ion concentration is first determined, and standard silver nitrate solutions of different concentrations are prepared based on the chloride ion concentration for use in titration. The COD of the high-chloride ion wastewater sample can be directly determined after titration treatment, avoiding the need to add the masking agent mercuric sulfate again, saving the use of mercuric sulfate, and reducing the error caused by diluting the water sample to determine COD, so that the COD measurement result is accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0020] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings. In the following description, the same reference numerals represent the same parts.

[0021] Figure 1 The present invention is a schematic flow chart of a method for determining COD in high chloride ion wastewater according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0024] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0026] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0027] Herein, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If multiple "optional" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" item is independent of each other. In this application, descriptions such as "optionally contain", "optionally include", etc. mean "contain or not contain". "Optional component X" means that component X exists or does not exist, or means that component X is contained or not contained.

[0028] In this article, unless otherwise stated, each reaction step may be carried out in the order described herein or may not be carried out in the order described herein. For example, other steps may be included between each reaction step, and the order of the reaction steps may also be appropriately swapped. This can be determined by the technician based on common knowledge and experience. Preferably, the reaction method herein is carried out sequentially.

[0029] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for a broad range of quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] The present application provides a method for determining COD in wastewater with high chloride ion concentration to solve at least one of the following technical problems in the prior art method for determining COD in wastewater: (1) The COD detection accuracy is poor for water samples with high chloride ion concentration and low COD. (2) In COD detection, the masking agent mercuric sulfate is used, which poses a high safety risk and high cost for waste liquid treatment. The method for determining COD in wastewater with high chloride ion concentration will be described below in conjunction with the accompanying drawings.

[0032] The method for determining COD in high chloride ion wastewater provided in the present application is exemplary. Figure 1 As shown, Figure 1 The schematic diagram of the structure of the method for determining COD of high chloride ion wastewater provided in the embodiment of the present application. The method for determining COD of high chloride ion wastewater of the present application can be used for determining COD of high chloride ion wastewater.

[0033] In order to more clearly illustrate the structure of the COD determination method for high chloride ion wastewater, the COD determination method for high chloride ion wastewater will be introduced below in conjunction with the accompanying drawings.

[0034] For example, see Figure 1 As shown, a method for determining COD of high chloride ion wastewater comprises the following steps:

[0035] According to the chloride ion concentration in high chloride ion wastewater, prepare silver nitrate standard solutions of different concentrations. Take high chloride ion wastewater samples according to the sampling volume, and titrate with silver nitrate standard solution until a large amount of brick red precipitate is produced. Filter the titrated water sample until the water sample is clear and transparent, measure the volume of the filtrate after filtration, and calculate the dilution multiple N according to the filtrate volume, N=filtrate volume / sampling volume of chloride ion wastewater sample.

[0036] Prepare the COD digestion pre-made reagent, take the potassium dichromate standard solution and mix it with the sulfuric acid-silver sulfate solution. The reaction chemical formula includes:

[0037] Ag + + Cl - → AgCl ↓

[0038] Ag + + CrO4 - → Ag2CrO4↓

[0039] Take the filtrate and mix it with the pre-made COD digestion reagent, heat it for digestion, and cool it to get the digestion solution. Measure the COD value of the digestion solution at 600nm. Calculate the COD of high chloride ion wastewater = COD measurement value × dilution factor N.

[0040] In some embodiments, during filtration, the titrated water sample is filtered through a slow-speed filter paper until the water sample becomes clear and transparent.

[0041] In some of the embodiments, the preparation of the COD digestion prefabricated reagent includes preparing a high-concentration COD digestion prefabricated reagent, wherein a 1 mol / L potassium dichromate standard solution and a 10 g / L sulfuric acid-silver sulfate solution are mixed in a volume ratio of 1:5 and stored for standby use.

[0042] In some of the embodiments, the high concentration COD digestion prefabricated reagent is used for COD determination in the range of 20 mg / L to 1000 mg / L.

[0043] For example, in one specific embodiment, the COD digestion prefabricated reagent is configured, including configuring a high-concentration COD digestion prefabricated reagent, and mixing 150 ml of a 1 mol / L potassium dichromate standard solution and 600 ml of a 10 g / L sulfuric acid-silver sulfate solution in a volume ratio for storage and standby use.

[0044] In some of the embodiments, the preparation of the COD digestion prefabricated reagent includes preparing a low-concentration COD digestion prefabricated reagent, wherein a 0.5 mol / L potassium dichromate standard solution and a 10 g / L sulfuric acid-silver sulfate solution are mixed in a volume ratio of 1:5 and stored for standby use.

[0045] In some of the embodiments, the low concentration COD digestion prefabricated reagent is used for COD determination in the range of 0 mg / L to 150 mg / L.

[0046] For example, in one specific embodiment, the preparation of the COD digestion prefabricated reagent includes preparing a low-concentration COD digestion prefabricated reagent, and mixing 150 mL of a 0.5 mol / L potassium dichromate standard solution with 600 mL of a sulfuric acid-silver sulfate solution for storage.

[0047] In some embodiments, the volume ratio of the filtrate to the COD digestion prefabricated reagent when mixed is 2mL:(5mL~6mL). The volume ratio of the diluted measurement solution to the COD digestion prefabricated reagent when mixed includes but is not limited to: 2mL:5mL, 2mL:5.5mL, 2mL:6mL or a range between any two of the foregoing.

[0048] In some embodiments, the digestion is heated to 160°C-165°C for at least 20 minutes. The temperature of the digestion includes but is not limited to: 160°C, 161°C, 163°C, 164°C, 165°C or a range between any two of the foregoing.

[0049] In some embodiments, the cooling temperature is 20° C. to 30° C. The cooling temperature includes but is not limited to: 20° C., 23° C., 25° C., 28° C., 30° C. or a range between any two of the foregoing.

[0050] In some embodiments, when a high chloride ion wastewater sample is titrated with a silver nitrate standard solution, the sampling volume of the chloride ion wastewater sample is 10 mL to 20 mL. The sampling volume of the chloride ion wastewater sample includes but is not limited to: 10 mL, 13 mL, 15 mL, 18 mL, 20 mL or a range between any two of the foregoing.

[0051] Example 1

[0052] This embodiment provides a method for determining COD of high chloride ion wastewater.

[0053] The method for measuring COD of high chloride ion wastewater in this embodiment comprises the following steps:

[0054] S11. Prepare silver nitrate standard solutions of different concentrations according to the chloride ion concentration in high chloride ion wastewater. Take 10mL of high chloride ion wastewater sample and titrate with silver nitrate standard solution until a large amount of brick red precipitate is produced. Filter the titrated water sample through slow-setting filter paper until the water sample is clear and transparent, measure the volume of the filtrate after filtration, and calculate the dilution factor N according to the filtrate volume, N=filtrate volume / sampling volume of chloride ion wastewater sample.

[0055] S12. Prepare COD digestion prefabricated reagents. Prepare COD digestion prefabricated reagents, including preparing high-concentration COD digestion prefabricated reagents. Mix 150mL of 1mol / L potassium dichromate standard solution with 600mL of 10g / L sulfuric acid-silver sulfate solution and store for standby use. The high-concentration COD digestion prefabricated reagent is used for COD determination in the range of 20mg / L~1000mg / L. Prepare low-concentration COD digestion prefabricated reagents. Mix 150mL of 0.5mol / L potassium dichromate standard solution with 600mL of 10g / L sulfuric acid-silver sulfate solution and store for standby use. The low-concentration COD digestion prefabricated reagent is used for COD determination in the range of 0mg / L~150mg / L.

[0056] The reaction formula includes:

[0057] Ag + + Cl - → AgCl ↓

[0058] Ag + + CrO4 - → Ag2CrO4↓

[0059] S13, take 2mL of the filtrate of step S11 and mix it with 5mL of COD digestion prefabricated reagent, heat it to 160℃ and digest it for at least 20min, and cool it to 20℃ to obtain a digestion solution. Observe whether the digestion solution is green. If the digestion solution turns green, it needs to be diluted again before measurement, because the digestion solution turns green, which means it exceeds the measurement range. Measure the COD measurement value of the digestion solution at 600nm. Calculate the COD of high chloride ion wastewater = COD measurement value × dilution factor N.

[0060] Example 2

[0061] This embodiment provides a method for determining COD of high chloride ion wastewater.

[0062] This example uses the high chloride ion wastewater COD determination method in Example 1 to determine the COD content in high chloride wastewater A. The chloride ion concentration in the high chloride ion wastewater sample is 11792 mg / L. The COD mass concentration of the water sample is preliminarily determined to be between 0 mg / L and 150 mg / L.

[0063] S21. Take 10mL of high chloride ion wastewater sample and titrate it with 0.28mol / L silver nitrate standard solution until a large amount of brick red precipitate is produced; filter the titrated water sample through slow-setting filter paper until the water sample is clear and transparent; measure the volume of the filtrate after filtration, which is 21.88mL, and calculate the dilution factor of the water sample, which is 21.88 / 10=2.188.

[0064] S22. Take 2 mL of filtrate, select low-concentration COD digestion prefabricated reagent, take 2 mL of diluted measuring solution and 5 mL of COD digestion prefabricated reagent and mix them in a measuring bottle, tighten the lid, shake to mix evenly, quickly put it into an environment heated to 165°C for digestion for 20 minutes, cool to room temperature 25°C, and obtain a digestion solution; no green color is produced in the digestion solution in the measuring bottle, indicating that the measurement meets the measurement range of the low-concentration COD digestion prefabricated reagent.

[0065] S23. The COD value of the digestion solution was measured at 600 nm and was 80.5.

[0066] S24. Calculate the COD of high chloride ion wastewater = COD measurement 80.5 × dilution factor 2.188.

[0067] Example 3

[0068] This embodiment provides a method for determining COD of high chloride ion wastewater.

[0069] This example uses the high chloride ion wastewater COD determination method in Example 1 to determine the COD content in high chloride wastewater A. The chloride ion concentration in the high chloride ion wastewater sample is 6820 mg / L. The COD mass concentration of the water sample is preliminarily determined to be between 0 mg / L and 150 mg / L.

[0070] S31. Take 10mL of high chloride ion wastewater sample and titrate it with 0.14mol / L silver nitrate standard solution until a large amount of brick red precipitate is produced; filter the titrated water sample through slow-setting filter paper until the water sample is clear and transparent; measure the volume of the filtrate after filtration, 22.65mL, and calculate the dilution factor of the water sample, 2.265, 2.265 = filtrate volume / sampling volume of chloride ion wastewater sample.

[0071] S32. Take 2 mL of filtrate, select low-concentration COD digestion prefabricated reagent, take 2 mL of diluted measurement solution and 5 mL of COD digestion prefabricated reagent and mix them in a measuring bottle, tighten the lid, shake to mix evenly, quickly put it into an environment heated to 165°C for digestion for 20 minutes, cool to room temperature 25°C, and obtain a digestion solution; if the digestion solution in the measuring bottle is green, it means that the measurement does not meet the measurement range of the low-concentration COD digestion prefabricated reagent and needs to be diluted.

[0072] S33, repeat step S31, measure the volume of the filtrate after filtration as 22.65, calculate the dilution factor of the water sample as 2.265, 2.265 = filtrate volume / sampling volume of the chloride ion wastewater sample.

[0073] S34. Repeat step S32.

[0074] S35. The COD value of the digestion solution was measured at 600 nm and was 69.0.

[0075] S36. Calculate the COD of high chloride ion wastewater = COD measurement value 69.0 × dilution factor 2.265.

[0076] Example 4

[0077] This embodiment provides a method for measuring COD of high chloride ion wastewater.

[0078] This example uses the high chloride ion wastewater COD determination method in Example 1 to determine the COD content in high chloride wastewater A. The chloride ion concentration in the high chloride ion wastewater sample is 14560 mg / L. The COD mass concentration of the water sample is preliminarily determined to be between 20 mg / L and 1000 mg / L.

[0079] S21. Take 10mL of high chloride ion wastewater sample and titrate it with 0.28mol / L silver nitrate standard solution until a large amount of brick red precipitate is produced; filter the titrated water sample through slow-setting filter paper until the water sample is clear and transparent; measure the volume of the filtrate after filtration as 24.67, and calculate the dilution factor of the water sample as 2.467, 2.467 = filtrate volume / sampling volume of chloride ion wastewater sample.

[0080] S22. Take 2 mL of filtrate, select high-concentration COD digestion prefabricated reagent, take 2 mL of diluted measuring solution and 6 mL of COD digestion prefabricated reagent and mix them in a measuring bottle, tighten the lid, shake to mix evenly, quickly put it into an environment heated to 160°C for digestion for 20 minutes, cool to room temperature 20°C, and obtain a digestion solution; no green color is produced in the digestion solution in the measuring bottle, indicating that the measurement meets the measurement range of the low-concentration COD digestion prefabricated reagent.

[0081] S23. The COD value of the digestion solution was measured at 600 nm and was 780.4.

[0082] S24. Calculate the COD of high chloride ion wastewater = COD measurement value 780.4 × dilution factor 2.467.

[0083] In summary, in the above-mentioned method for determining COD of high-chloride ion wastewater, the chloride ion concentration is first determined, and standard silver nitrate solutions of different concentrations are prepared based on the chloride ion concentration for use in titration. The COD of the high-chloride ion wastewater sample can be directly determined after titration treatment, avoiding the need to add the masking agent mercuric sulfate again, saving the use of mercuric sulfate, and reducing the error caused by diluting the water sample to determine COD, so that the COD measurement result is accurate.

[0084] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0085] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for determining COD of high chloride ion wastewater, characterized in that: The steps include: According to the chloride ion concentration in the high chloride ion wastewater, prepare silver nitrate standard solutions of different concentrations; take a high chloride ion wastewater sample according to the sampling volume, and titrate it with the silver nitrate standard solution until a large amount of brick red precipitate is produced; filter the titrated water sample until the water sample is clear and transparent, measure the volume of the filtrate after filtration, and calculate the dilution multiple N according to the filtrate volume, N=filtrate volume / sampling volume of the chloride ion wastewater sample; Prepare the COD digestion pre-made reagent, mix the potassium dichromate standard solution with the sulfuric acid-silver sulfate solution; Take the filtrate and mix it with the pre-made COD digestion reagent, heat it for digestion, cool it to get the digestion solution, measure the COD value of the digestion solution at 600nm, and calculate the COD of high chloride ion wastewater = COD measured value × dilution factor N.

2. The method for measuring COD of high chloride ion wastewater according to claim 1, characterized in that: During filtration, the titrated water sample is filtered through slow-setting filter paper until the water sample is clear and transparent.

3. The method for measuring COD of high chloride ion wastewater according to claim 1, characterized in that: When configuring COD digestion prefabricated reagents, including configuring high-concentration COD digestion prefabricated reagents, take a 0.5 mol / L potassium dichromate standard solution and a 10 g / L sulfuric acid-silver sulfate solution in a volume ratio of 1:5 and mix them for storage for later use.

4. The method for measuring COD of high chloride ion wastewater according to claim 3, characterized in that: The high-concentration COD digestion prefabricated reagent is used for COD determination in the range of 20 mg / L to 1000 mg / L.

5. The method for measuring COD of high chloride ion wastewater according to claim 1, characterized in that: When configuring the COD digestion prefabricated reagent, including configuring the low-concentration COD digestion prefabricated reagent, take a 0.25 mol / L potassium dichromate standard solution and a 10 g / L sulfuric acid-silver sulfate solution in a volume ratio of 1:5 and mix them for storage for later use.

6. The method for measuring COD of high chloride ion wastewater according to claim 5, characterized in that: The low-concentration COD digestion prefabricated reagent is used for COD determination in the range of 0 mg / L to 150 mg / L.

7. The method for measuring COD of high chloride ion wastewater according to any one of claims 1 to 6, characterized in that: The volume ratio of the filtrate and the COD digestion prefabricated reagent when mixed is 2mL: (5mL~6mL).

8. The method for measuring COD of high chloride ion wastewater according to any one of claims 1 to 6, characterized in that: When heating digestion, heat to 160℃~165℃ and digest for at least 20 minutes.

9. The method for measuring COD of high chloride ion wastewater according to any one of claims 1 to 6, characterized in that: When cooling, the cooling temperature is to 20℃~30℃.

10. The method for measuring COD of high chloride ion wastewater according to any one of claims 1 to 6, characterized in that: When using silver nitrate standard solution to titrate high chloride ion wastewater samples, the sampling volume of chloride ion wastewater samples is 10mL~20mL.

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