China's Refractories ›› 2021, Vol. 30 ›› Issue (3): 28-32.DOI: 10.19691/j.cnki.1004-4493.2021.03.006
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FU Yuanyuan1,*(), HAN Junhua2, CAO Haijie2, LEI Xiaoyu2, HAN Dan2, XU Xiaoying2
Online:
2021-09-15
Published:
2021-11-26
Contact:
FU Yuanyuan
About author:
Fu Yuanyuan was born in 1987 in Shaanxi Province, China. She majored in Chemistry and Bioinformatics and graduated from Sichuan University in 2015. She worked at the National Quality Supervision and Inspection Center for Refractories from 2015 to 2018, and is now working in CISDI Engineering Co., Ltd., engaging in refractory procurement.
FU Yuanyuan, HAN Junhua, CAO Haijie, LEI Xiaoyu, HAN Dan, XU Xiaoying. Determination of Hexavalent Chromium in Refractories by Diphenylcarbazide Spectrophotometry[J]. China's Refractories, 2021, 30(3): 28-32.
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URL: http://www.cnref.cn/EN/10.19691/j.cnki.1004-4493.2021.03.006
Method No. | Extracting steps | Cr6+ content /(μg · g-1) |
---|---|---|
1 | 150 mL mixed solution of 20 g/L NaOH and 30 g/L Na2CO3, boiling for 30 min | 2.19 |
2 | 50 mL of water, 100 ℃, 30 min | 1.26 |
3 | 50 mL of water, 80 ℃, 60 min | 1.27 |
4 | 150 mL mixed solution of 20 g/L NaOH and 30 g/L Na2CO3, 90-95 ℃, 60 min | 2.27 |
5 | Room temperature, 60 min | 0.65 |
Table 1 Comparison of different extracting methods
Method No. | Extracting steps | Cr6+ content /(μg · g-1) |
---|---|---|
1 | 150 mL mixed solution of 20 g/L NaOH and 30 g/L Na2CO3, boiling for 30 min | 2.19 |
2 | 50 mL of water, 100 ℃, 30 min | 1.26 |
3 | 50 mL of water, 80 ℃, 60 min | 1.27 |
4 | 150 mL mixed solution of 20 g/L NaOH and 30 g/L Na2CO3, 90-95 ℃, 60 min | 2.27 |
5 | Room temperature, 60 min | 0.65 |
Boiling time /min | 10 | 20 | 30 | 40 | 50 | 60 |
---|---|---|---|---|---|---|
Cr6+ content /(μg · g-1) | 126 | 130 | 132 | 131 | 132 | 130 |
Table 2 Effect of boiling time of alkaline solution on extraction
Boiling time /min | 10 | 20 | 30 | 40 | 50 | 60 |
---|---|---|---|---|---|---|
Cr6+ content /(μg · g-1) | 126 | 130 | 132 | 131 | 132 | 130 |
Mass of sample /g | Amount of extraction solution | Absorbance value | Cr6+ content / (μg · g-1) |
---|---|---|---|
1.004 7 | 1/4 | 0.536 | 341 |
2.000 0 | 1/8 | 0.525 | 336 |
3.006 4 | 1/20 | 0.327 | 348 |
4.007 0 | 1/20 | 0.437 | 349 |
5.006 0 | 1/20 | 0.537 | 343 |
Table 3 Sample mass test
Mass of sample /g | Amount of extraction solution | Absorbance value | Cr6+ content / (μg · g-1) |
---|---|---|---|
1.004 7 | 1/4 | 0.536 | 341 |
2.000 0 | 1/8 | 0.525 | 336 |
3.006 4 | 1/20 | 0.327 | 348 |
4.007 0 | 1/20 | 0.437 | 349 |
5.006 0 | 1/20 | 0.537 | 343 |
Cr2O72- | CrO42- | [Cr (H2O6)]3+ or Cr3+ | [Cr (OH)]- | [Cr (H2O6)]2+ or Cr2+ | |
---|---|---|---|---|---|
Valence states of chromium | +6 | +6 | +3 | +3 | +2 |
Color | Orange-red | Yellow | Purple | Bright green | Blue |
pH | pH=2 | pH=6 | Acidic | Strong alkaline | Acidic |
Table 4 Valence states of chromium in solution
Cr2O72- | CrO42- | [Cr (H2O6)]3+ or Cr3+ | [Cr (OH)]- | [Cr (H2O6)]2+ or Cr2+ | |
---|---|---|---|---|---|
Valence states of chromium | +6 | +6 | +3 | +3 | +2 |
Color | Orange-red | Yellow | Purple | Bright green | Blue |
pH | pH=2 | pH=6 | Acidic | Strong alkaline | Acidic |
Cr3+/μg | Cr6+/μg | Absorbance value | Recovered Cr6+/μg | Recovery rate /% |
---|---|---|---|---|
40 | 0 | 0.001 | 0.000 2 | - |
40 | 25 | 0.164 | 26 | 104 |
60 | 50 | 0.322 | 51 | 102 |
120 | 100 | 0.638 | 102 | 102 |
140 | 125 | 0.802 | 128 | 102 |
Table 5 Effect of trivalent chromium
Cr3+/μg | Cr6+/μg | Absorbance value | Recovered Cr6+/μg | Recovery rate /% |
---|---|---|---|---|
40 | 0 | 0.001 | 0.000 2 | - |
40 | 25 | 0.164 | 26 | 104 |
60 | 50 | 0.322 | 51 | 102 |
120 | 100 | 0.638 | 102 | 102 |
140 | 125 | 0.802 | 128 | 102 |
Reagent amount /mL | 10 | 12 | 14 | 16 |
---|---|---|---|---|
Cr6+ content /(μg · g-1) | 56 | 54 | 56 | 57 |
Table 6 Effect of color reagent amount
Reagent amount /mL | 10 | 12 | 14 | 16 |
---|---|---|---|---|
Cr6+ content /(μg · g-1) | 56 | 54 | 56 | 57 |
Equipment No. | Cr6+/μg | Absorbance value (x) | Working curve |
---|---|---|---|
Spectro- photometer 1# | 0 | 0.002 | y = 0.160 0x+0.000 1 R2 = 0.999 8 |
10 | 0.063 | ||
25 | 0.156 | ||
50 | 0.307 | ||
75 | 0.463 | ||
100 | 0.623 | ||
125 | 0.786 | ||
Spectro- photometer 2# | 0 | 0.003 | y = 0.162 7x-0.000 1 R2 = 0.999 7 |
10 | 0.064 | ||
25 | 0.156 | ||
50 | 0.315 | ||
75 | 0.466 | ||
100 | 0.627 | ||
125 | 0.764 |
Table 7 Drawing of working curve
Equipment No. | Cr6+/μg | Absorbance value (x) | Working curve |
---|---|---|---|
Spectro- photometer 1# | 0 | 0.002 | y = 0.160 0x+0.000 1 R2 = 0.999 8 |
10 | 0.063 | ||
25 | 0.156 | ||
50 | 0.307 | ||
75 | 0.463 | ||
100 | 0.623 | ||
125 | 0.786 | ||
Spectro- photometer 2# | 0 | 0.003 | y = 0.162 7x-0.000 1 R2 = 0.999 7 |
10 | 0.064 | ||
25 | 0.156 | ||
50 | 0.315 | ||
75 | 0.466 | ||
100 | 0.627 | ||
125 | 0.764 |
Samples | Sample mass /g | Absorbance value | Cr6+ content /(μg · g-1) | Mean Cr6+ content /(μg · g-1) N=5 |
---|---|---|---|---|
Industrial chromium oxide | 5.003 2 | 0.515 | 329 | 328 |
Fused chromium oxide | 5.007 8 | 0.434 | 280 | 276 |
Industrial chromium oxide | 5.160 4 | 0.574 | 331 | 341 |
High chrome brick | 4.983 9 | 0.173 | 113 | 115 |
High chrome brick | 5.004 9 | 0.098 | 64 | 67 |
Magnesia chrome brick | 5.000 8 | 0.116 | 74 | 72 |
Table 8 Sample determination
Samples | Sample mass /g | Absorbance value | Cr6+ content /(μg · g-1) | Mean Cr6+ content /(μg · g-1) N=5 |
---|---|---|---|---|
Industrial chromium oxide | 5.003 2 | 0.515 | 329 | 328 |
Fused chromium oxide | 5.007 8 | 0.434 | 280 | 276 |
Industrial chromium oxide | 5.160 4 | 0.574 | 331 | 341 |
High chrome brick | 4.983 9 | 0.173 | 113 | 115 |
High chrome brick | 5.004 9 | 0.098 | 64 | 67 |
Magnesia chrome brick | 5.000 8 | 0.116 | 74 | 72 |
Samples | Cr6+ content /(μg · g-1) N=9 | Standard deviation /(μg · g-1) | Reletive standard deviation /% | Cr6+ /μg | Recovered Cr6+/ μg | Recovery rate /% |
---|---|---|---|---|---|---|
Fused chromium oxide | 340 | 4.84 | 1.4 | |||
High chrome brick | 150 | 5.75 | 3.8 | |||
Pure chromium trioxide | 5.00 | 4.94 | 98.8 | |||
5.00 | 5.19 | 103.8 |
Table 9 Precision and recovery rate tests
Samples | Cr6+ content /(μg · g-1) N=9 | Standard deviation /(μg · g-1) | Reletive standard deviation /% | Cr6+ /μg | Recovered Cr6+/ μg | Recovery rate /% |
---|---|---|---|---|---|---|
Fused chromium oxide | 340 | 4.84 | 1.4 | |||
High chrome brick | 150 | 5.75 | 3.8 | |||
Pure chromium trioxide | 5.00 | 4.94 | 98.8 | |||
5.00 | 5.19 | 103.8 |
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