Permanganate index on-line monitoring method and system

Abstract

The application discloses a permanganate index online monitoring method and system, and the method comprises the following steps: S1, setting a minimum threshold value A; S2, taking a quantitative sample to be measured, then sequentially adding potassium permanganate solution and acid solution, and bubbling and mixing; S3, heating to 100 DEG C, and the duration is not more than 10 min, and then cooling to 40 DEG C; S4, adding an alkaline solution to the sample to be measured, bubbling and mixing; S5, adding 1 mL of pure water, bubbling and mixing, reacting for 5 min, and reading a received light intensity signal X; S6, comparing X with A; S8, calculating the absorbance of the sample to be measured, and S9, calculating the permanganate index of the water sample; the system comprises a four-channel valve, a heating pipe, a peristaltic pump, a twelve-channel valve and a metering pipe, the digestion is completed at 100 DEG C for 10 min, colorimetric test can be carried out, the reaction system only generates about 5 mL of reaction waste liquid at a time, the system has a self-cleaning function, the detection device does not need to be maintained in a life cycle, and the design achieves the purposes of short test time and low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental water quality analysis, in particular to a permanganate index online monitoring method and system. BACKGROUND

[0002] The permanganate index is one of the comprehensive indicators for indirectly reflecting the pollution of organic matter and inorganic oxidizable substances in water bodies. The measurement methods of existing permanganate index online equipment mainly include ORP electrode titration method, colorimetric titration method, and photometric colorimetric method.

[0003] The ORP electrode titration method uses excess potassium permanganate to completely oxidize the oxidizable substances in the water sample in an acidic solution at 100℃. After cooling to room temperature, a certain amount of sodium oxalate is added to the reaction solution to reduce the remaining potassium permanganate. Finally, the excess sodium oxalate is back-titrated with a potassium permanganate standard solution through a titration pump. The ORP electrode reaction system has strong anti-interference ability for detecting turbidity and color of water bodies. However, the strong acid and high temperature environment of the reaction system greatly affects the service life of the ORP electrode. In addition, during the test process, the electrode surface will have attachments accumulated, which need to be cleaned regularly or even replaced to ensure the accuracy of the test system is not affected. The waste liquid generated by the ORP electrode reaction system is about 3-5 times that of the colorimetric method, greatly increasing the operation and maintenance cost of the online monitoring instrument.

[0004] The colorimetric titration method uses excess potassium permanganate to react with the water sample in an acidic solution at 100℃ for a certain period of time, completely oxidizing certain organic and inorganic reducing substances in the water sample. After cooling to room temperature, a certain amount of sodium oxalate is added to the reaction solution to reduce the remaining potassium permanganate. Then, the excess sodium oxalate is back-titrated with a potassium permanganate standard solution. During the back-titration of the excess sodium oxalate in the potassium permanganate reaction solution, the color of the reaction solution slowly transitions from colorless and transparent to light red, indicating that the reaction has reached the end point. The amount of potassium permanganate standard solution consumed during titration is directly proportional to the amount of oxidizable substances in the water sample, from which the permanganate index of the water sample can be calculated. Because the light intensity changes significantly when a specific wavelength of light source passes through the light red reaction solution, the colorimetric titration method can determine the reaction end point by monitoring the light intensity jump. This scheme reduces the operation and maintenance cost and reagent consumption compared to the electrode titration method. However, the turbidity factor of the water sample itself affects the colorimetric judgment during titration, making it difficult to find an accurate titration end point.

[0005] The conventional photometric colorimetry adds a quantitative potassium permanganate solution and an acid solution to a water sample and heats to 80-90 DEG C, and after sufficient reaction, the absorbance of the reaction solution is detected at room temperature, and the absorbance has a linear relationship with the permanganate index in the water sample. The photometric colorimetry has a small reaction system, and the reagent consumption and waste liquid volume are very small, and the detection time is short, but the conventional photometric colorimetry increases the acidity of the reaction system required in the national standard method, and at the same time, the reaction temperature of the system is reduced from 100 DEG C to 80-90 DEG C, so that the digestion rate is inconsistent for different reducing substances such as glucose. SUMMARY

[0006] The present application is to overcome the problems of long test time and high cost in the prior art, and provides a permanganate index online monitoring method and system with short test time and low cost.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] A permanganate index online monitoring method, characterized in that it comprises the following steps:

[0009] S1, setting the minimum threshold of the received light intensity signal as A;

[0010] S2, taking a quantitative sample to be measured, and then adding a potassium permanganate solution and an acid solution with the same dosage as the sample to be measured in turn, and bubbling and mixing;

[0011] S3, heating to 100 DEG C, and the duration is not more than 10 min, and cooling to 40 DEG C;

[0012] S4, continuing to add an alkaline solution with the same dosage as the sample to be measured, and bubbling and mixing;

[0013] S5, adding 1 mL of pure water, bubbling and mixing, and the reaction time is not more than 5 min, and reading the received light intensity signal X;

[0014] S6, comparing X and A, if X>A, recording the light intensity signal at this time , discharging the reaction solution and cleaning the reaction vessel, and then injecting 3 mL of pure water, recording the emitted light intensity signal as , and the received light intensity signal is recorded as ;

[0015] S7, if X

[0016] S8, calculating the absorbance of the sample to be measured

[0017] S9, executing the range of S1 to S8 for the zero mark and the quantity mark, and the relationship between the concentration (c) and the absorbance (A) can be obtained ​The relationship formula is: C = (V1-V2) / V2, wherein C is the permanganate index of the water sample, V1 is the volume of the potassium permanganate solution, V2 is the volume of the acid solution, and V is the volume of the sample.

[0018] In S2, the volume of the sample to be measured is 0.5 mL, the volumes of the potassium permanganate solution and the acid solution are both 0.5 mL, and the concentration of the 0.5 mL potassium permanganate solution is 0.14 g / L. The colorimetric reaction system only needs 1.5 mL of reagent, which consumes less reagent and reduces the reaction cost. In S3, the digestion is complete after 10 minutes of reaction at 100 DEG C, and the colorimetric test is performed. Compared with the titration method, the colorimetric test is more time-saving and can compensate for the defects of the conventional colorimetric method that the digestion temperature and acidity do not meet the national standard. In S4, the volume of the alkaline solution is 0.5 mL. The colorimetric reaction system only produces about 5 mL of reaction waste liquid and about 16 mL of cleaning waste water at one time, which is much lower than the waste liquid volume generated by the titration method and the conventional colorimetric method. The colorimetric method effectively reduces the operation and maintenance cost and achieves the purposes of short test time and low cost.

[0019] Preferably, the reactor vessel is a valve-closed heating tube. The heating tube is a valve-closed heating tube, which provides a closed space for the whole reaction process to avoid splashing of liquid droplets during the bubbling process.

[0020] Preferably, in S1, the threshold value A is 0.91-1.11 times the received light intensity signal when the heating tube is filled with pure water.

[0021] Preferably, in S4, the alkaline solution is a mixture of sodium hydroxide and potassium iodide prepared in a certain proportion. The mixed alkaline solution of sodium hydroxide and potassium iodide is a chromogenic agent used for colorimetric test.

[0022] The present application also aims to provide an online monitoring of the permanganate index by the method described above.

[0023] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0024] An online monitoring system of permanganate index comprises a four-channel valve, a heating tube, a peristaltic pump, a twelve-channel valve and a measuring tube. Each channel of the four-channel valve is connected with the heating tube, the measuring tube, the peristaltic pump and air, respectively. One channel of the twelve-channel valve is connected with the measuring tube, and the heating tube is connected with the measuring tube through an external pipeline.

[0025] The double-power system is realized based on the peristaltic pump, the four-channel valve, the measuring tube and the heating tube. The valve port of the four-channel valve connecting the peristaltic pump and the measuring tube is opened, and the valve port connecting the heating tube and air is closed. At this time, the peristaltic pump rotates clockwise to make the liquid enter the measuring tube for measuring the volume of the liquid. After the measurement is completed, the valve port of the measuring tube is closed, and the valve port of the heating tube is opened. At this time, the peristaltic pump rotates counterclockwise to extract the liquid into the heating tube for liquid determination. Such a setting increases the self-cleaning function of the whole system, reduces the waste liquid volume and the operation and maintenance cost, and the detection device does not need to be maintained during the life cycle.

[0026] Preferably, the heating tube is provided with an emission detection device, and the emission detection device is a 420nm parallel light emission detection device.

[0027] Preferably, the 420nm parallel light is a single-wavelength cold light source.

[0028] Preferably, the heating tube is provided with an infrared liquid detection device, and the infrared liquid detection device is mounted on the emission detection device.

[0029] Preferably, each channel of the twelve-channel selector valve is connected with an analysis waste liquid, a cleaning waste water, a zero mark, a reagent one, a reagent two, a reagent three, a reagent four, a metering pipe, pure water, a standard sample, a quantity mark and a sample to be measured.

[0030] The present application has the following advantages: the reaction can be completely carried out by digestion at 100 DEG C for 10 minutes, and the reaction endpoint can be found more quickly than by titration; the reaction system of the present colorimetric method is very simple, only 1.5mL of reagent is needed, and the system only needs one peristaltic pump, the cost is much lower than that of the titration pump and ORP electrode required by the titration method, the waste liquid amount is effectively reduced, the reaction system only produces about 5mL of reaction waste liquid at one time, the system has a self-cleaning function, and the detection device does not need to be maintained in the life cycle, so that the test time is short and the cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0032] Figure 1 is a schematic diagram of the system structure;

[0033] Figure 2 is a twelve-channel selector valve diagram in Figure 1

[0034] ​In the figure: 1. heating tube, 11. infrared liquid detection device, 12. emission detection device, 2. peristaltic pump, 3. twelve-channel discharge valve, 4. metering tube, 5. four-channel discharge valve. Embodiment

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0036] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "middle" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0037] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "connected" and the like should be broadly understood, for example, "connected" can be fixedly connected, or detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium, or can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] The technical solutions of the present application will be further described in detail below in combination with the drawings and specific embodiments of the present application;

[0039] The inventive concept of the present application is as follows, the present application provides a permanganate index online monitoring method, characterized in that, comprising the following steps:

[0040] S1, set the minimum threshold value of the received light intensity signal as A;

[0041] S2, take a certain amount of sample to be measured, then add the same amount of potassium permanganate solution and acid solution as the sample to be measured in turn, and mix by bubbling;

[0042] S3, heat to 100℃, the duration is not more than 10 min, and cool to 40℃;

[0043] S4, continue to add the same amount of alkaline solution as the sample to be measured, and mix by bubbling;

[0044] S5, add 1 mL pure water, bubble mixing, reaction time is not more than 5 min, read the received light intensity signal X;

[0045] S6, compare X and A, if X>A, record the light intensity signal , discharge reaction liquid discharge and clean the reaction vessel, then inject 3 mL pure water, record the emission light intensity signal is , the received light intensity signal is recorded as ;

[0046] S7, if X<A, cycle S5 and S6, until X>A, then the cycle stops;

[0047] S8, calculate the absorbance of the sample to be tested

[0048] S9, the zero mark and the quantity mark execute S1 to S8 range can get the relationship of concentration (c) and absorbance (A) of , so as to calculate the permanganate index of water sample. The reaction vessel is a valve closed heating tube 1.

[0049] The threshold value A in S1 is 0.91~1.11 times the received light intensity signal when the heating tube 1 is filled with pure water.

[0050] The alkaline solution in S4 is prepared by mixing sodium hydroxide and potassium iodide in proportion.

[0051] The four-way valve 5, the heating tube 1, the peristaltic pump 2, the twelve-way valve 3 and the metering tube 4, each channel of the four-way valve 5 is connected with the heating tube 1, the metering tube 4, the peristaltic pump 2 and the air respectively, one channel of the twelve-way valve 3 is connected with the metering tube 4, and the heating tube 1 is connected with the metering tube 4 through the external pipeline.

[0052] The emission detection device 12 is installed on the heating tube 1, and the emission detection device 12 is a 420 nm parallel light emission detection device 12.

[0053] 420nm parallel light is a single wavelength cold light source.

[0054] The infrared liquid detection device 11 is arranged on the heating tube 1, and the infrared liquid detection device 11 is installed on the emission detection device 12.

[0055] Each channel of the twelve-way valve 3 is connected with the analysis waste liquid, the cleaning waste water, the zero mark, the reagent one, the reagent two, the reagent three, the reagent four, the metering tube 4, the pure water, the standard sample, the quantity mark and the sample to be tested respectively, the reagent one is filled with potassium permanganate solution, the reagent two is filled with acid solution, the reagent three is filled with potassium hydroxide solution, and the reagent four is filled with sodium iodide solution.

[0056] ​

[0057] One embodiment of the present application:

[0058] S1, set the minimum threshold value of the light intensity signal of the 420nm parallel light receiving side of the heating tube 1 ;

[0059] S2, open the valve port of the four-way valve 5 connecting the metering tube 4 and the peristaltic pump 2, close the valve port connecting the heating tube 1 and the air, rotate the peristaltic pump 2 clockwise, extract 0.5mL of the sample to be tested from the pipeline connecting the reagent to be tested on the twelve-way valve 3, close the valve port of the four-way valve 5 connecting the metering tube 4 and the air, open the valve port connecting the heating tube 1 and the peristaltic pump 2, rotate the peristaltic pump 2 counterclockwise, and then the sample to be tested in the metering tube 4 is discharged into the heating tube 1; follow the above steps to extract 0.5mL of 0.14g / L potassium permanganate solution and 0.5mL of acid solution from the pipelines connecting reagent one and reagent two on the twelve-way valve 3 in turn, and then discharge them into the heating tube 1, and then close the valve ports of the four-way valve 5 and mix them by bubbling;

[0060] S3, heat the mixed solution in the heating tube 1 to 100℃ in S2 for 10 minutes, and then cool it to 40℃;

[0061] S4, only open the valve port of the four-way valve 5 connecting the metering tube 4 and the peristaltic pump 2, rotate the peristaltic pump 2 clockwise, extract 0.5mL of sodium hydroxide and potassium iodide solution from the pipelines connecting reagent two and reagent three on the twelve-way valve 3, close the metering tube 4 valve port, open the heating tube 1 valve port, rotate the peristaltic pump 2 counterclockwise, and then add the metered 0.5mL of sodium hydroxide and potassium iodide mixed and configured alkaline solution to the digestion solution in the heating tube 1 in S3, close the four-way valve 5, and mix them by bubbling;

[0062] S5, only open the valve port of the four-way valve 5 connecting the metering tube 4 and the peristaltic pump 2, rotate the peristaltic pump 2 clockwise, extract 1mL of pure water from the pure water pipeline connected to the twelve-way valve 3, close the metering tube 4 valve port of the four-way valve 5, rotate the peristaltic pump 2 counterclockwise, add 1mL of pure water to the reaction solution in S4, close the four-way valve 5, mix them by bubbling, react for 5 minutes, and read the light intensity signal of the 420nm light source receiving side of the heating tube 1 ;

[0063] S6, compare the light intensity signal in S5 with the minimum light intensity signal threshold value set in S1 , if , record the light intensity signal of the 420nm light source emitting side of the heating tube 1 at this time , open the four-way valve 5 to connect the heating tube 1 and the valve port of the peristaltic pump 2, the heating tube 1 is connected with the bottom of the metering tube 4 through the external pipeline, and then connected with the twelve-way valve 3, rotate the peristaltic pump 2 counterclockwise, the reaction liquid in the heating tube 1 is discharged and the heating tube 1 is cleaned, according to the above water extraction steps, 3mL pure water is injected into the heating tube 1, and the light intensity of the heating tube 1 at the 420nm light source emission side and the receiving side is recorded respectively as and ;

[0064] S7, if S6 , then loop S5 and S6, record time stop the loop;

[0065] S8, calculate the absorbance of the sample to be tested ;

[0066] S9, execute the range of S1 to S8 with zero mark and quantity mark, the relationship between the concentration (A) ) and the absorbance (A ) of the sample can be obtained, and the permanganate index of the water sample can be calculated. The test data is shown in the following table.

[0067]

[0068]

[0069] Although the specific embodiments of the present application are described in detail with reference to the exemplary embodiments thereof, it must be understood that those skilled in the art can design a variety of other improvements and embodiments, which will fall within the spirit and scope of the principles of the present application. Specifically, within the scope of the foregoing disclosure, drawings and claims, reasonable variations and improvements can be made in the arrangement of parts and / or dependent combination layout without departing from the spirit of the present application; in addition to the variations and improvements in parts and / or layout, the scope is defined by the appended claims and their equivalents.​

Claims

1. A method for on-line monitoring of permanganate index, characterized in that, It comprises the following steps: S1, setting the minimum threshold of the received light intensity signal as A, wherein the threshold A in S1 is 0.91-1.11 times of the received light intensity signal when the heating tube (1) is filled with pure water; S2, taking a certain amount of sample to be measured, then adding the same amount of potassium permanganate solution and acid solution in sequence, and mixing by bubbling; S3, heating to 100℃ for no more than 10 min, and then cooling to 40℃; S4, continuously adding the same amount of alkaline solution as the sample to be measured, and mixing by bubbling, wherein the alkaline solution in S4 is a mixture of sodium hydroxide and potassium iodide prepared in proportion; S5, adding 1 mL of pure water, mixing by bubbling, and reading the received light intensity signal X for no more than 5 min; S6, compare X with A, if X > A, record the light intensity signal at this time , discharge and clean the reaction vessel, then inject 3 mL of pure water, record the emitted light intensity signal as , receive the light intensity signal as ; S7, if X<A, repeating S5 and S6 until X>A, then stopping the cycle; S8, calculate absorbance of the sample to be tested ; S9, the zero mark and the quantity mark are executed S1 to S8, the range of the quantity can be obtained about the concentration (c) and the absorbance (A) of the relationship formula, thereby calculating the permanganate index of water sample. ​​ 2. The permanganate index online monitoring method according to claim 1, characterized in that, The reactor is a valve-closed heating tube.

3. A permanganate index on-line monitoring system which implements the permanganate index on-line monitoring method according to any one of claims 1 and 2, characterized by, It comprises a four-channel valve (5), a heating tube (1), a peristaltic pump (2), a twelve-channel valve (3), and a metering tube (4), wherein each channel of the four-channel valve (5) is connected to the heating tube (1), the metering tube (4), the peristaltic pump (2), and air, respectively, one channel of the twelve-channel valve (3) is connected to the metering tube (4), and the heating tube (1) is connected to the metering tube (4) through an external pipeline.

4. The permanganate index on-line monitoring system according to claim 3, characterized in that, The heating tube (1) is provided with an emission detection device (11), and the emission detection device is a 420 nm parallel light emission detection device.

5. The permanganate index on-line monitoring system according to claim 4, characterized in that, The 420 nm parallel light is a single-wavelength cold light source.

6. The permanganate index on-line monitoring system according to claim 3, characterized in that, The heating tube (1) is provided with an infrared liquid detection device (12), and the infrared liquid detection device (12) is installed on the emission detection device (11).

7. The permanganate index on-line monitoring system according to claim 3, characterized in that, Each channel of the twelve-channel valve (3) is connected to analysis waste liquid, cleaning waste water, zero mark, reagent one, reagent two, reagent three, reagent four, the metering tube (4), pure water, standard sample, volume mark, and sample to be measured, respectively, wherein the reagent one contains potassium permanganate solution, the reagent two contains acid solution, the reagent three contains potassium hydroxide solution, and the reagent four contains sodium iodide solution.

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