CN111272750A - Ozone colorimeter calibration method based on potassium iodate and application thereof - Google Patents
Ozone colorimeter calibration method based on potassium iodate and application thereof Download PDFInfo
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Abstract
The invention discloses a calibration method and application of an ozone colorimeter based on potassium iodate, and relates to the technical field of environmental monitoring. The calibration method includes the steps of, S1: preparing potassium iodate solution by taking potassium iodate; s2: adding excess I into potassium iodate solution‑And H+Mixing evenly to ensure that the potassium iodate reacts completely; s3: adjusting the pH value of the solution to 6.2-6.5, and then adding DPD for complete reaction; s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Reduced mass concentration c1Equivalent ozone concentration c of potassium iodate solution2，c2Less than or equal to 1 mg/L; s5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝c2+ -0.02, unit mg/L. The method for calibrating the ozone colorimeter based on potassium iodate can effectively avoid ozoneThe instability of the standard solution and the difficulty in preparing the standard solution improve the accuracy of ozone detection, and the on-line ozone monitoring system is compared and calibrated by an accurate ozone colorimeter, so that the monitoring of CCP points is ensured to be effective.
Description
Technical Field
The invention relates to the technical field of environmental monitoring, in particular to a calibration method of an ozone colorimeter.
Background
Packaged drinking water production uses ozone for sterilization and disinfection, and the concentration of ozone determines the sterilization effect, so that the concentration of ozone is used as a CCP point (key control point) for real-time monitoring.
Because the online ozone monitoring system needs to monitor the concentration of ozone in real time, and is not suitable for taking out of an external calibration, and the detection accuracy of the monitoring probe needs to be ensured after the monitoring probe is replaced or maintained due to faults, a factory needs to have the capability of calibrating or checking the online ozone monitoring system. The online ozone monitoring system does not have a calibration function, needs to be calibrated by another ozone detector, and mostly uses a DPD (N, N-diethyl-1, 4-phenylenediamine sulfate) method handheld ozone colorimeter, so that the accuracy of the handheld ozone colorimeter needs to be ensured to ensure the accuracy of online ozone monitoring.
The ozone colorimeter is a portable single-wavelength spectrophotometer for rapidly detecting ozone on site, and the detection is rapid, accurate and convenient to carry. The existing ozone colorimeter is calibrated by an ozone standard solution, however, ozone is an extremely unstable strong oxidant, and the calibration of the ozone colorimeter by the ozone standard solution has two defects: firstly, because ozone is extremely easy to decompose, an ozone generator needs to be used for preparing ozone on site, and a common factory laboratory does not have the ozone generator; the other is that ozone is dissolved in water to form an ozone solution, the concentration of the ozone needs to be measured to form a standard solution, the ozone decays quickly, and the half-life period of the ozone in the water is 10-15 min usually, so that the ozone solution with the standard concentration is extremely difficult to obtain in factories, and even the ozone standard solution is prepared, the ozone colorimeter is difficult to accurately calibrate. Therefore, the ozone colorimeter calibrated by using the ozone calibration solution cannot check and calibrate the ozone detector in a factory, and the accuracy of online ozone monitoring is difficult to guarantee.
Disclosure of Invention
Ozone colorimeter principle of measuring ozone concentration:
ozone in water can react with potassium iodide to generate free iodine, DPD can react with the free iodine to generate a red compound when the pH value is 6.2-6.5, the absorbance of the red compound is measured by a spectrophotometry (a spectrophotometer or an ozone colorimeter) at the wavelength of 520nm, and the concentration of the ozone in the water is determined by the principle that the absorbance value is in direct proportion to the concentration.
The reaction equation is:
①O3+2H++2I-＝O2+I2+H2O
②2[(C2H5)2NC6H4NH2]+2I2＝(C2H5)2NC6H4N＝NH4C6N(C2H5)2+4H++4I－
since the ozone standard solution is unstable and not readily available, the present invention is based on the reaction intermediate I2And replacing ozone with potassium iodate. The reaction equation is as follows,
①KIO3+5KI+6H2SO4＝3I2+3H2O+3K2SO4，
②2[(C2H5)2NC6H4NH2]+2I2＝(C2H5)2NC6H4N＝NH4C6N(C2H5)2+4H++4I－
potassium iodate is an oxidizing agent which independently exists at normal temperature and is relatively stable, a standard solution with corresponding concentration can be prepared by taking the potassium iodate as a reference through accurate quantification, and the conversion relation between the concentration (mg/L) of the potassium iodate and the concentration (mg/L) of ozone is calculated to be 1.4861:1 through a reaction formula.
According to the principle, the invention provides a calibration method of an ozone colorimeter based on potassium iodate, and the specific scheme is as follows.
A method for calibrating a potassium iodate-based ozone colorimeter includes the steps of,
s1: preparing potassium iodate solution by taking potassium iodate;
s2: adding excess I into potassium iodate solution-And H+Mixing evenly to ensure that the potassium iodate reacts completely;
s3: adjusting the pH value of the solution to 6.2-6.5, and then adding DPD for complete reaction;
s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Reduced mass concentration c1Equivalent ozone concentration c of potassium iodate solution2，c2≤1mg/L；
S5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝c2+ -0.02, unit mg/L.
Preferably, in step S4, the equivalent ozone concentration c2The calculation formula of (a) is as follows: c. C2＝c1/1.4861。
Preferably, in the step S2, I is added-Is potassium iodide.
Preferably, in step S2, H is added+Is H2SO4、H3PO4One or more of (a). Further, said H+The concentration of (2) is 2 mol/L.
Preferably, in step S3, an alkali is added to adjust the pH of the potassium iodate solution, and the alkali may be one or more of NaOH and KOH. Further, the concentration of the alkali is 1 mol/L.
A method for calibrating an online ozone monitoring system by using a potassium iodate-based ozone colorimeter calibration method comprises the following steps: the method comprises the steps of simultaneously measuring the same ozone mixed water sample by using a calibrated ozone colorimeter and an online ozone monitoring system, calibrating the online ozone monitoring system by using the measurement value of the calibrated ozone colorimeter as a standard value, and periodically checking to ensure the accuracy of the online ozone monitoring system.
And (3) monitoring the ozone concentration in real time by using a calibrated online ozone monitoring system, and ensuring that the ozone concentration is always within a key limit value.
According to the calibration method of the ozone colorimeter based on potassium iodate, the standard solution of potassium iodate is used for replacing the standard solution of ozone, the calibration and the verification of the ozone colorimeter are used, the problems that the standard solution of ozone is unstable and the standard solution is difficult to prepare can be effectively solved, the operability of factory internal verification is improved, the accuracy of ozone detection is improved, an online ozone monitoring system is compared and calibrated through the accurate ozone colorimeter, CCP point monitoring is guaranteed to be effective, and the product quality is guaranteed to be qualified.
Detailed Description
In order to more fully understand the technical contents of the present invention, the technical solutions of the present invention will be further described and illustrated with reference to specific embodiments.
Example 1
A method for calibrating a potassium iodate-based ozone colorimeter includes the steps of,
s1: weighing superior pure potassium iodate which is dried to constant weight at the temperature of 120 +/-5 ℃, and preparing a potassium iodate solution;
s2: adding excess I into potassium iodate solution-And H+Mixing evenly to ensure that the potassium iodate reacts completely;
s3: adjusting the pH value of the solution to 6.2-6.5, and then adding DPD for complete reaction;
s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Reduced mass concentration c1Equivalent ozone concentration c of potassium iodate solution2，c2≤1mg/L；
S5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝(c2. + -. 0.02), in mg/L.
Example 2
A method for calibrating a potassium iodate-based ozone colorimeter includes the steps of,
s1: weighing superior pure potassium iodate which is dried to constant weight at the temperature of 120 +/-5 ℃, and preparing a potassium iodate solution;
s2: adding excessive potassium iodide and phosphoric acid into the potassium iodate solution, and uniformly mixing to ensure that the potassium iodate completely reacts;
s3: adjusting the pH value of the solution to 6.2, and then adding DPD for complete reaction;
s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Reduced mass concentration c1Potassium iodate solutionEquivalent ozone concentration c2，c2＝c11.4861; wherein, c2≤1mg/L；
S5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝c2In mg/L.
Example 3
A method for calibrating a potassium iodate-based ozone colorimeter includes the steps of,
s1: weighing superior pure potassium iodate which is dried to constant weight at the temperature of 120 +/-5 ℃, and preparing a potassium iodate solution;
s2: adding excessive potassium iodide and 1mol/L sulfuric acid into a potassium iodate solution, and uniformly mixing to ensure that the potassium iodate completely reacts;
s3: adjusting the pH value of the solution to 6.5 by using 1mol/L NaOH, and then adding DPD for complete reaction;
s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Reduced mass concentration c1Equivalent ozone concentration c of potassium iodate solution2，c2＝c1/1.4861, wherein c2≤1mg/L；
S5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝c2+ -0.02, unit mg/L.
Example 4
A method for calibrating a potassium iodate-based ozone colorimeter includes the steps of,
s1: weighing superior pure potassium iodate which is dried to constant weight at the temperature of 120 +/-5 ℃, and preparing a potassium iodate solution;
s2: adding excess potassium iodide and 1mol/L H into potassium iodate solution3PO4Mixing evenly to ensure that the potassium iodate reacts completely;
s3: regulating the pH value of the solution to 6.3 by using 1mol/L KOH, and then adding DPD for complete reaction;
s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Converted mass concentrationc1Equivalent ozone concentration c of potassium iodate solution2，c2＝c1/1.4861, wherein c2≤1mg/L；
S5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝c2In mg/L.
Example 5
A method for calibrating a potassium iodate-based ozone colorimeter includes the steps of,
s1: weighing superior pure potassium iodate which is dried to constant weight at the temperature of 120 +/-5 ℃, and preparing a potassium iodate solution;
s2: adding excessive potassium iodide and 0.5mol/L sulfuric acid into a potassium iodate solution, and uniformly mixing to ensure that the potassium iodate completely reacts;
s3: regulating the pH value of the solution to 6.4 by using 0.5mol/L KOH, and then adding DPD for complete reaction;
s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Reduced mass concentration c1Equivalent ozone concentration c of potassium iodate solution2，c2＝c1/1.4861, wherein c2≤1mg/L；
S5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝c2In mg/L.
Comparative experiment 1
1.4861g of high-grade pure potassium iodide dried at 120 +/-5 ℃ to constant weight is weighed, dissolved in water, transferred into a 1000mL volumetric flask, added with water until the volumetric flask reaches the constant volume marking line, and shaken uniformly for later use, wherein the standard stock solution is equivalent to the mass concentration of ozone (O3) of 1000.0 mg/L.
0.50mL of the standard stock solution of potassium iodate was taken up in a 1000mL brown volumetric flask, 0.1g of potassium iodide was added, and the potassium iodide was rinsed off to the bottom with an appropriate amount (about 50mL) of water.
1.0mL of 1mol/L sulfuric acid solution is added into the volumetric flask and shaken up; after 1 minute, 1mL of 1mol/L NaOH solution was added to the flask (pH value was 6.2-6.5 after diluting the flask with water to a constant volume)Then adding DPD for complete reaction, diluting with water to a constant volume marked line, wherein the solution in the volumetric flask is equivalent to the mass concentration c of ozone2It was 0.50 mg/L.
Taking the solution in the volumetric flask to be equivalent to the mass concentration c of ozone20.50mg/L, measuring the concentration of the potassium iodate solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter so that the measured concentration c of the ozone colorimeter0It was 0.50 mg/L.
Taking the solution in the volumetric flask to be equivalent to the mass concentration c of ozone2The concentration of the solution (in mg/L) was measured 6 times for each of the 0.50mg/L solution, the ozone colorimeter calibrated as described above (verification group 1), and the Cinchaku brand ozone colorimeter (comparative group 1), the Argentina brand ozone colorimeter (comparative group 2), and the Yu vast brand ozone colorimeter (comparative group 3), and the results of the measurements are shown in Table 1 below.
TABLE 1
The detection results show that the absolute deviation of the ozone colorimeter calibrated by the method is less than or equal to 0.02mg/L compared with the accurate measurement results of several ozone colorimeters of different brands, so that the method for calibrating the ozone colorimeter based on the potassium iodate can be used for calibrating the ozone colorimeter.
Comparative experiment 2
The ozone colorimeter calibrated by the contrast experiment 1 and the online ozone monitoring system are used for simultaneously measuring the same ozone mixed water sample, and the online ozone monitoring system is calibrated by taking the measurement value of the ozone colorimeter as a standard value.
Taking 6 groups of sample water samples (samples 1-6) on site at an ozone mixed water storage tank; the ozone colorimeter (verification group 1), the online ozone monitoring system (verification group 2) and the circinese brand ozone colorimeter (comparison group 1), the larvada brand ozone colorimeter (comparison group 2) and the limo vast brand ozone colorimeter (comparison group 3) which are calibrated by the comparison experiment 1 respectively measure the ozone concentration of each group of sample water samples at the same time, and the measurement results are shown in the following table 2.
TABLE 2
| Item | Verification group 1 | Verification group 2 | Comparative group 1 | Comparative group 2 | Comparative group 3 |
| Sample 1(mg/L) | 0.45 | 0.46 | 0.45 | 0.46 | 0.45 |
| Sample 2(mg/L) | 0.51 | 0.53 | 0.50 | 050 | 0.51 |
| Sample 3(mg/L) | 0.48 | 0.51 | 0.50 | 0.48 | 0.47 |
| Sample 4(mg/L) | 0.46 | 0.45 | 0.45 | 0.44 | 0.45 |
| Sample 5(mg/L) | 0.54 | 0.56 | 0.55 | 0.54 | 0.56 |
| Sample 6(mg/L) | 0.50 | 0.51 | 0.51 | 0.49 | 0.50 |
The detection results show that the absolute deviation of the ozone colorimeter calibrated by the method is less than or equal to 0.02mg/L compared with the measurement results of ozone colorimeters of different brands with accurate measurement; the measurement result of the online ozone monitoring system has deviation within an allowable range compared with the measurement result of several ozone colorimeters of different brands with accurate measurement. Therefore, the ozone colorimeter calibrated by the calibration method of the invention can be used for accurately determining the concentration of ozone in the solution, and the online ozone monitoring system calibrated by the ozone colorimeter,
the technical contents of the present invention are further illustrated by the examples, so as to facilitate the understanding of the reader, but the embodiments of the present invention are not limited thereto, and any technical extension or re-creation based on the present invention is protected by the present invention.
Claims (8)
1. A calibration method of an ozone colorimeter based on potassium iodate is characterized by comprising the following steps,
s1: preparing potassium iodate solution by taking potassium iodate;
s2: adding excess I into potassium iodate solution-And H+Mixing evenly to ensure that the potassium iodate reacts completely;
s3: adjusting the pH value of the solution to 6.2-6.5, and then adding DPD for complete reaction;
s4: calculating the mass concentration c of potassium iodate in the solution obtained in the step S1 according to the mass of potassium iodate in the step S11(ii) a Reduced mass concentration c1Equivalent ozone concentration c of potassium iodate solution2，c2≤1mg/L；
S5: measuring the concentration of the solution with an ozone colorimeter to be calibrated, calibrating the ozone colorimeter such that the measured concentration c of the ozone colorimeter0＝c2±0.02。
2. The method of claim 1, wherein in step S4, the equivalent ozone concentration c is calculated2The calculation formula of (a) is as follows: c. C2＝c1/1.4861。
3. The method of claim 1, wherein in step S2, I is added-Is potassium iodide.
4. The method of claim 1, wherein in step S2, H is added+Is H2SO4、H3PO4One or more of (a).
5. The method of claim 4, wherein the H is measured by a computer and the H is measured by a computer using a computer-implemented method+The concentration of (2) is 2 mol/L.
6. The method for calibrating a potassium iodate-based ozone colorimeter as claimed in claim 1 wherein in step S3 a base is added to adjust the pH of the potassium iodate solution, said base being selected from one or more of NaOH and KOH.
7. The method for calibrating a potassium iodate-based ozone colorimeter according to claim 6 wherein the concentration of the base is 1 mol/L.
8. A method of calibrating an on-line ozone monitoring system using a potassium iodate-based ozone colorimeter calibration method comprising calibrating an ozone colorimeter using the potassium iodate-based ozone colorimeter calibration method of claim 1; the method comprises the steps of simultaneously measuring the same ozone mixed water sample by using a calibrated ozone colorimeter and an online ozone monitoring system, and calibrating the online ozone monitoring system by using the measurement value of the calibrated ozone colorimeter as a standard value.
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| CN2482081Y (en) * | 2001-03-23 | 2002-03-13 | 广东省微生物研究所 | Total chlorine, residual chlorine and ozone quick measuring reagent box for water |
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