YAOYan-dan,LAIYong-zhong,WUYue,et al.Detection Method of Hexavalent Chromium in Industrial Wastewater with Abnormal Absorption Spectrum[J].China Water & Wastewater,2023,39(24):145-154.
Detection Method of Hexavalent Chromium in Industrial Wastewater with Abnormal Absorption Spectrum
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第39卷
Number:
第24期
Page:
145-154
Column:
Date of publication:
2023-12-17
- Keywords:
- hexavalent chromium; spectral interference; spectral absorption curve; linear fitting; slope
- Abstract:
- After pretreatment with zinc hydroxide coprecipitation-acid potassium permanganate digestion method specified in Water Quality-Determination of Chromium(Ⅵ)-1,5 Diphenylcarbohydrazide Spectrophotometric Method (GB/T 7467-1987), the samples of industrial wastewater containing hexavalent chromium still have interferences which are incomplete or difficult to be digested, and the absorption spectrum is brown after color development, resulting in higher detection results or qualitative errors. The two printing and dyeing wastewater samples with and without obvious absorption spectrum interferences were quantitatively analyzed by spectral absorption curve-linear fitting slop-spectrophotometry (SAC-LFS-S). The measuring wavelength in the range of 518-523 nm and the corresponding reference wavelength ranges (554-569 nm, 542-577 nm, 539-579 nm, 540-580 mm and 534-584 nm) with good accuracy indexes such as digestion blank, sample results and recoveries and detection limits were selected, so as to reduce or eliminate the interferences. The quantitative results of single-wavelength method (standard detection method with measuring wavelength of 540 nm), dual-wavelength method (measuring wavelength of 540 nm and reference wavelength of 660 nm) and the optimized SAC-LFS-S method were compared. Both the single-wavelength and dual-wavelength methods had poor accuracy in detecting No.1 printing and dyeing wastewater (8.2-8.9 μg/L, standard recovery less than 80%) and No.3 landfill wastewater (3.7-4.0 μg/L, standard recovery less than 90%) with obvious interference in absorption spectrums. However, the results of the optimized SAC-LFS-S method were all lower than the detection limits (1.5-1.8 μg/L), and the recoveries were 85.0%-86.0% and 93.0%-93.5%, respectively. After optimization, the results of other 4 printing and dyeing wastewater without absorption spectrum interference measured by SAC-LFS-S method ranged from 2.3 μg/L to 13.3 μg/L with recoveries between 87.5% and 94.5%, which had no significant difference with the results detected by the dual-wavelength method. However, the result was significantly lower than that detected by single-wavelength method. The SAC-LFS-S method corrected by reference wavelength band was suitable for quantitative analysis of industrial wastewater pretreatment by zinc hydroxide coprecipitation-acid potassium permanganate digestion, especially the samples with obvious absorption spectral interference.
Last Update:
2023-12-17