This standard specifies the ammonium ferrous sulfate titration method for the determination of hexavalent chromium in solid waste leachate. This standard is applicable to the determination of hexavalent chromium in solid waste leachate. The method can also be used to determine hexavalent chromium in water and wastewater. GB/T 15555.7-1995 Determination of hexavalent chromium in solid waste by ammonium ferrous sulfate titration GB/T15555.7-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of hexavalent chromium in solid waste
Ammonium ferrous sulfate titration method
Solid waste--Determination of chromium (V)--Titrimetric method
1 Subject content and scope of application
1.1 This standard specifies the ammonium ferrous sulfate titration method for the determination of hexavalent chromium in solid waste leachate. GB/T15555.7--1995
1.2 This standard applies to the determination of hexavalent chromium in solid waste leachate. The method can also be used to determine hexavalent chromium in water and wastewater. 1.2.1 The quantitative limit of the method: 1 mg/L. 1.2.2 Interferencebzxz.net
Vanadium interferes with the determination. Except for vanadium slag leachate, the vanadium content in the general leachate will not affect the determination. The interference of trivalent iron in the determination, when the concentration of trivalent iron (mg/L) is 175 times that of hexavalent chromium, a relative error of 2.8% can be introduced. 2 Principle
Eliminate the interference of trivalent iron in sulfuric acid and phosphoric acid medium, use N-phenyl anthranilic acid as an indicator, titrate with ammonium ferrous sulfate, reduce hexavalent chromium to trivalent chromium, and the excess ammonium ferrous sulfate reacts with the indicator, and the solution turns yellow-green as the end point. The hexavalent chromium content in the solid waste leachate is calculated according to the amount of ammonium ferrous sulfate standard solution. The reaction equation is as follows: 2Na2CrO.+7HzSO4+6FeSO,(NH)2SO-Cr2(SO.):+2NaSO4+6(NH),SO4+3Fe2(SO):+8H2O3 Reagents
Unless otherwise specified, reagents that meet national standards or professional standards, deionized water or water of equal purity are used. 3.1 Sulfuric acid 1+3.
3.2 Sulfuric acid 1+9.
3.3 Phosphoric acid 1+1.
3.4 ​​N-phenyl-1-aminobenzoic acid indicator (abbreviated as chromium indicator, C1sHnNO2) 0.2%: Weigh 0.2g of chromium indicator, dissolve in 100mL 0.2% sodium carbonate solution, shake well, store in a brown bottle, and store at low temperature. 3.5 Hexavalent chromium standard solution (0.4mg/mL): Weigh 1.1316g of potassium dichromate (K,Cr20,, high-grade pure) dried at 120℃ for 2h, dissolve in distilled water and transfer to a 1000mL volumetric flask, dilute to the mark with distilled water, and shake to hook. 3.6 Ammonium ferrous sulfate standard solution: Weigh 25g of analytical pure ammonium ferrous sulfate [Fe (NH,) 2 (SO,) , ·6H,O] and dissolve in 1000mL sulfuric acid (3.2) solution, filter, and calibrate using the following method. Pipette 10.00mL of hexavalent chromium standard solution (3.5) and place it in a 150mL conical flask. Add 50mL of water, 5mL of sulfuric acid solution (3.1) and 5 drops of N-phenyl-o-aminobenzoic acid (3.4). Titrate with ammonium ferrous sulfate solution (3.6) until the solution changes from purple-red to yellow-green. This is the end point. The titration degree of ammonium ferrous sulfate solution on hexavalent chromium is calculated as follows: National Environmental Protection Agency
Approved on March 28, 1995
National Technical Supervision Bureau
Implemented on January 1, 1996
GB/T 15555.7—1995
10.00×0.40
Where: T—1.00 ml of ammonium ferrous sulfate solution is equivalent to the number of milligrams of hexavalent chromium; V—consumption of ammonium ferrous sulfate solution, mL, 0.40-
-the number of milligrams of hexavalent chromium contained in each milliliter of potassium dichromate solution (3.5). Note: Ammonium ferrous sulfate solution is unstable and needs to be recalibrated before use. 4 Instruments
4.1 Pipette: 5mL, 10mL.
4.2 Erlenmeyer flask: 150mL, 250mL.
4.3 Burette (divided into 0.1mL) 25mL. 5 Sample preservation
The leachate should be placed in a polyethylene or hard glass bottle with a smooth inner surface, add sodium hydroxide to adjust the pH to 7~~~9, and analyze as soon as possible. If the sample cannot be analyzed within 24 hours, an equal portion of the sample should be taken and a known amount of Cr (V) should be added, and both should be stored at 4°C. When analyzing the leachate, the leachate sample to which a known amount of Cr (V) has been added should also be analyzed to determine whether Cr (V) has changed during the storage period. If its concentration has not changed, the stored leachate can be used to analyze the Cr (V) content. 6 Determination
6.1 Take an appropriate amount of leachate in a 150mL conical flask, adjust it to neutral with dilute sulfuric acid or alkali, and add water to 50mL. 6.2 Take another 150mL conical flask and add 50mL of water for blank test. 6.3 Add 5 mL of sulfuric acid (3.1), 1 mL of phosphoric acid (3.3) and 5 drops of N-phenyl anthranilic acid indicator (3.4) to the above-mentioned conical flasks, and titrate with ammonium ferrous sulfate standard solution (3.6) until the solution changes from purple-red to yellow-green, which is the end point. Record the amount of standard solution used. And deduct the amount of blank test from the amount of standard titration solution used for the test solution. 7. Expression of results
The hexavalent chromium concentration in the leachate is calculated as follows: c (mg/L) -
Wherein: T is the titer of ammonium ferrous sulfate, mg/mL; TXV
V×1000
V, — the amount of ammonium ferrous sulfate standard solution consumed in the titration, mL; V——the volume of leachate absorbed in the test, mL. 8 Precision and accuracy
For the chromium slag leachate with hexavalent chromium concentration of 185.6mg/L, the relative standard deviation of 6 parallel determinations was 0.3%. For the leachate sample with chromium content of 1855.7ug, 1000ug chromium was added, and the recovery rate of 6 additions was 99.0%~100.8%. 552
GB/T15555.7—1995
Appendix A
Notes
(reference)
A1 Do not use the solution containing Cr20 to wash the device III. A2 The chromium indicator has reducing properties and should not be added too much. It is advisable to prepare a more dilute solution for use, and add it after most of the hexavalent chromium has been titrated (the solution turns light yellow), and the amount of each portion is roughly the same. A3 Vanadium interference determination, when the sample contains vanadium, the determination result is the total amount of chromium and vanadium. The conversion factor 1% vanadium is equivalent to 0.34% chromium, and the vanadium content should be deducted from the determination result.
Note: For the preparation method of the leaching solution, refer to Appendix B of GB/T15555.1-1995 "Determination of total mercury in solid waste by cold atomic absorption spectrophotometry". Additional notes:
This standard was proposed by the Science and Technology Standards Department of the State Environmental Protection Administration. This standard was drafted by the China National Environmental Monitoring Center. The main drafters of this standard are Wang Sufang, Rui Kuisheng, Su Huaqing, and Xing Shucai. This standard is entrusted to the China National Environmental Monitoring Center for interpretation. 553
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