Instruments and procedures for detecting ozone content in water
Generally, drinking water or natural water after ozone disinfection can be directly measured by potassium iodide-DPD on-site colorimetry, and the range is 0.02mg/L-2.50mg/L. The main principle is that ozone in water can react with potassium iodide to generate free iodine, and when the pH value is 6.2-6.5, free iodine can react with N,N diethyl-p-phenylenediamine (DPD) to generate a red compound, which can It selectively absorbs light with a wavelength of 520nm, and you can determine the concentration of ozone according to the degree of absorption of light by the water sample. In addition, everyone should pay attention to the fact that too much iron and copper ions in the water will interfere with the final test results. We can add 0.1mL EDTA disodium solution to the water sample to eliminate it. If there is too much residual chlorine in the water sample, it will also It will have a great impact on the results, which can be eliminated by adding 0.2mL glycine solution to the water sample. 1. Spectrophotometer 2. Colorimetric bottle reagent 1. Potassium iodide reagent tube 2. DPD reagent tube 3. Potassium iodide (KI) 4. EDTA disodium solution Weigh 4g EDTA disodium and dissolve in laboratory pure water In the medium, dilute to 1000mL with laboratory pure water, and mix well. 5. Glycine solution Weigh 10g of glycine and dissolve it in laboratory pure water, dilute to 100mL with laboratory pure water and mix well. 6. Potassium iodate standard stock solution Weigh 0.1486g of high-grade pure potassium iodate that has been baked at 120°C-140°C for 2 hours in advance, dissolve it in laboratory pure water, dilute to 100mL, and mix well. 7. Potassium iodate standard solution Accurately pipette 1.00mL potassium iodate standard stock solution into a 100mL brown volumetric flask, add about 20mL water, add about 1g potassium iodide, 1 drop of 20% sulfuric acid solution, shake well, let stand for 2min, Make up to volume with laboratory pure water and mix well. Prepare just before use. Potassium iodate solution with a concentration of 14.86mg/L is equivalent to ozone with a concentration of 10.0mg/L. Detailed steps of detection 1. Use a straw to pipette the water sample to be tested to the 10mL scale line of the colorimetric bottle, wipe the outer wall of the colorimetric bottle, and put the colorimetric bottle into the colorimetric tank to lock. 2. Adjust zero, perform blank measurement, and the instrument will display '0.00', indicating that the zero calibration is completed. 3. Add a piece of potassium iodide reagent to the colorimetric bottle, pipette the water sample to be tested to the scale line of the colorimetric bottle, add a piece of DPD reagent, tighten the colorimetric bottle positioner, shake to dissolve the reagent, and wipe it clean Put the outer wall of the colorimetric bottle into the colorimetric tank and lock it, and place it for 3min. 4. Take a concentration measurement. According to the built-in standard curve of the instrument, the value displayed on the instrument is the mass concentration of ozone in the water sample (unit, mg/L).