HJ 551-2016Water quality-Determination of chlorine dioxide and chlorite-Continuous iodometric method (English PDF)

Foreword

In order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on the Prevention and Control of Water Pollution, Protection of human health, regulate the determination of chlorine dioxide and chlorite in wastewater, the development of this standard.

This standard specifies the continuous titration iodometric method for the determination of chlorine dioxide and chlorite in industrial wastewater dyeing and finishing industry.

This standard is a revision of the "Determination of Chlorine Dioxide in Water Quality (Temporary)" (HJ 551-2009).

This standard was first published in 2009, the original standard drafting unit for the Beijing Environmental Protection Monitoring Center. This is the first the main contents of the amendment are as follows.

- revised standard name, scope of application, chlorine dioxide method detection limit, precautions;

- revised the standard solution of sodium thiosulfate standard solution and potassium iodate standard solution, the removal of potassium dichromate calibration method;

- the lower limit of the determination of chlorine dioxide, the detection limit of chlorite and the lower limit of determination;

- increased interference and elimination, sample determination time and environmental conditions, precision, quality assurance and quality control, Waste treatment.

Since the implementation of this standard, the original standard "Determination of chlorine dioxide in water quality iodine method (provisional)" (HJ 551-2009) Abolished.

This standard is organized by the Ministry of Environmental Protection Science and Technology Standards Division.

The drafting of this standard. Beijing Environmental Protection Monitoring Center, Beijing Shijingshan District Environmental Protection Monitoring Station.

The standard verification unit. Beijing Xicheng District Environmental Protection Monitoring Station, Beijing Kangju Environmental Inspection Station, Qingdao City Environment Monitoring center station, Qingdao Environmental Protection Bureau Laoshan Branch monitoring station, Beijing Chaoyang District Environmental Protection Monitoring Station, Beijing Yanqing District Environmental protection monitoring station, Beijing Shijingshan District Environmental Protection Monitoring Station, Beijing Environmental Protection Monitoring Center.

The environmental protection department of this standard approved on May 13, 2016.

This standard has been implemented since August 1, 2016.

This standard is explained by the Ministry of Environmental Protection.

Water quality - Determination of chlorine dioxide and chlorite - Continuous titration of iodine method

1 Scope of application

This standard specifies the continuous titration iodometric method for the determination of chlorine dioxide and chlorite in industrial wastewater dyeing and finishing industry.

This standard applies to the use of sub-bleaching process of textile dyeing and finishing industry emissions of chlorine dioxide and chlorite determination.

When the sampling amount was 150 ml, the detection limit of chlorine dioxide was 0.09 mg/L and the lower limit was 0.36 mg/L.

The detection limit of chlorite (based on chlorite) was 0.08 mg/L and the lower limit was 0.32 mg/L.

2 Principle of the method

Chlorine dioxide and chlorite at different pH conditions, can oxidize iodide ions to precipitate iodine. With the same sample in the middle Under the conditions of the use of sodium thiosulfate solution titration of chlorine dioxide and iodine ion reaction into chlorite precipitation of iodine, and then adjust the pH of the sample is 1 to 3, and the iodide precipitated by the reaction of the chlorite with the iodide ion is titrated with sodium thiosulfate solution.

Titration to determine chlorine dioxide and chlorite content. See reaction formula (1) and reaction formula (2).

2 I2

1ClOIClO -> (1)

O2HHCl2I4HIHClO 222 -> (2)

3 Interference and elimination

3.1 There are other oxygen-containing chlorides, and can react with I2 and I- to cause oxidation and reduction.

3.2 Chroma will cause interference to the titration end point. When the water samples are colored, the same water sample should be used as a reference for the titration endpoint Goods.

4 Reagents and materials

Unless otherwise stated, analytical pure chemical reagents conforming to national standards are used for analysis, and the test water is distilled water or Deionized water.

4.1 Potassium iodide (KI). Crystal.

4.2 Sulfuric acid. rho (H2SO4) = 1.84 g/ml.

4.3 potassium iodate (KIO3). excellent grade pure. Before use, should be 105 °C ~ 110 °C baking 2 h, placed in the dryer to cool to the room Warm, spare.

4.4 Sodium hydroxide (NaOH).

4.5 Potassium dihydrogen phosphate (KH2PO4 · 2H2O).

4.6 Disodium hydrogen phosphate (Na2HPO4 · 2H2O).

4.7 Sodium thiosulfate (Na2S2O3.5H2O).

4.8 anhydrous sodium carbonate (Na2CO3).

4.9 soluble starch [(C6H10O5) n].

4.10 salicylic acid (C7H6O3).

4.11 Zinc chloride (ZnCl2).

4.12 Sulfuric acid solution. 1 1 (v/v), prepared with sulfuric acid (4.2).

4.13 sodium hydroxide solution. c (NaOH) = 0.1 mol/L.

Weigh 4 g of sodium hydroxide (4.4) in a small amount of water and dilute to 1000 ml.

4.14 Buffer solution. pH = 7.

34.0 g of potassium dihydrogen phosphate (4.5) and 35.5 g of disodium hydrogen phosphate (4.6) were weighed and dissolved in water.

Released to 1000 ml.

4.15 potassium iodate standard solution. c (1/6KIO3) = 0.0500 mol/L.

Weigh 1.7835 g (accurate to 0.0001 g) potassium iodate (4.3), dissolve with water and set to 1000 ml volumetric flask, Shake well Store in a brown glass reagent bottle and keep it dark.

4.16 Sodium thiosulfate standard solution. c (Na2S2O3) ~0.05 mol/L.

12.5 g of sodium thiosulfate (4.7) and 0.1 g of anhydrous sodium carbonate (4.8) were weighed and washed with freshly boiled and cooled to room temperature Dissolved, the volume to 1000 ml, shake. Store in a brown glass reagent bottle and keep it dark.

Before use with potassium iodate standard solution (4.15) calibration. 250 ml iodine bottle, add 80 ml of water and 1 g iodination Potassium (4.1), 10.00 ml potassium iodate standard solution (4.15), shake, then add 2 ml sulfuric acid solution (4.12), immediately add Sealed and shaken, kept in the dark for 6 min. With the sodium thiosulfate standard solution to be calibrated to the solution was pale yellow, Add 1 ml of starch solution (4.18), continue to be calibrated sodium thiosulfate standard solution titrated to blue just disappeared to the end point. Record the titration volume of sodium thiosulfate standard solution. Sodium thiosulfate standard solution concentration calculated by the formula (1).

C 0500.000.10 × = (1) where. C - sodium thiosulfate standard solution concentration, mol/L;

V - titration of potassium iodate standard solution consumption of sodium thiosulfate standard solution volume, ml;

10.00 - the amount of potassium iodate standard solution used, ml;

0.0500 - potassium iodate standard solution concentration, mol/L.

Standard solution of sodium thiosulfate standard titration Remove 10.00 ml of the standard sodium thiosulfate standard solution (4.16), in a 100 ml brown volumetric flask, Boil and cool to room temperature to dilute the volume to the mark. Pro is now available.

4.18 Starch solution. rho = 0.005 g/ml.

Weigh 0.5 g of soluble starch (4.9), with a small amount of water into a paste, add 100 ml of boiling water, stir well, overnight. The supernatant was transferred to a beaker and 0.125 g of salicylic acid (4.10) and 0.4 g of zinc chloride (4.11) were added and stored.

Stored in a reagent bottle.

5 Instruments and equipment

Unless otherwise stated, the use of the national standard A-class glass gauge is used for the analysis.

5.1 Iodine bottle. 250 ml.

5.2 Brown Acid Burets. 50.00 ml.

5.3 Common laboratory equipment and glassware.

6 Samples

Chlorine dioxide and chlorite are unstable in water, volatile and decomposed by reduced substances. Use a hard glass bottle or polyethylene Bottle collection of samples, water samples should be filled with sampling bottles, do not leave space and bubbles, to avoid heat, light and severe vibration.

Samples are not easy to transport and store and should be analyzed within 30 min after sampling.

7 Analysis steps

Measure 150 ml of water to 250 ml of iodine, adjust the pH to near neutral with sodium hydroxide solution (4.13) Add 5 ml of buffer solution (4.14) and 1 g of potassium iodide (4.1), immediately plug and seal and shake, with sodium thiosulfate standard Titration solution (4.17) titrated until the solution was pale yellow, add 1 ml of starch solution (4.18), continue with sodium thiosulfate Titration solution (4.17) titrated to blue just disappeared as the end point, record the titration volume of sodium thiosulfate standard titration solution V1. Add 3 ml of sulfuric acid solution (4.12) to adjust the pH to 1 ~ 3, the solution was blue or dark brown, continue with thioside Sodium titanate titration solution (4.17) titrated to blue or dark brown just disappeared to the end, recorded twice titrated consumption of thiosulfide the total volume of sodium titanate titration solution.

Note 1. Depending on the amount of chlorine dioxide and chlorite in the wastewater, the sampling volume is reduced and diluted to 150 ml with water.

Note 2. Experiments should be carried out under conditions that avoid direct sunlight.

Note 3. During the course of the experiment, the sample should be kept sealed and the sample should be taken out immediately to prevent the release of chlorine dioxide from the sample.

Calculation and representation of results

9 Precision

10 Quality assurance and quality control

Each batch of sample should be measured at least 10% of the parallel sample. When the number of samples is less than 10, at least one parallel should be measured Twin. Parallel to the relative deviation should be <= 20%.

11 Waste treatment

The waste liquid produced in the experiment shall be handled safely according to the relevant requirements.

12 Precautions

Chlorine dioxide is corrosive, the collection of high concentrations of wastewater, should pay attention to protection, to avoid contact with the skin and the skin, and in the upper hand to sample.