Factors Affecting the Detection of Hexavalent Chromium in Cr-Contaminated Soil

Mingtao Huang, Guoyu Ding, Xianghua Yan, Pinhua Rao (), Xingrun Wang (), Xiaoguang Meng and Qiantao Shi
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Mingtao Huang: School of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
Guoyu Ding: Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, School of Environment, Beijing Jiaotong University, Beijing 100044, China
Xianghua Yan: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Pinhua Rao: School of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
Xingrun Wang: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Xiaoguang Meng: Stevens Institute of Technology, Hoboken, NJ 07030, USA
Qiantao Shi: Stevens Institute of Technology, Hoboken, NJ 07030, USA

IJERPH, 2022, vol. 19, issue 15, 1-12

Abstract: The alkali digestion pretreatment method in the United States Environmental Protection Agency (USEPA) Method 3060A could underestimate the content of Cr(VI) in Cr-contaminated soils, especially for soils mixed with chromite ore processing residue (COPR), which leads to a misjudgment of the Cr(VI) level in soils after remediation, causing secondary pollution to the environment. In this study, a new pretreatment method to analyze Cr(VI) concentration in contaminated soils was established. The impacts of soil quality, particle size, alkali digestion time and the rounds of alkali digestion on Cr(VI) detection in contaminated soils was explored and the alkali digestion method was optimized. Compared with USEPA Method 3060A, the alkaline digestion time was prolonged to 6 h and multiple alkali digestion was employed until the amount of Cr(VI) in the last extraction was less than 10% of the total amount of Cr(VI). Because Cr(VI) in COPR is usually embedded in the mineral phase structure, the hydration products were dissolved and Cr(VI) was released gradually during the alkaline digestion process. The amount of Cr(VI) detected showed high correlation coefficients with the percentage of F1 (mild acid-soluble fraction), F2 (reducible fraction) and F4 (residual fraction). The Cr(VI) contents detected by the new alkaline digestion method and USEPA Method 3060A showed significant differences for soil samples mixed with COPR due to their high percentage of residual fraction. This new pretreatment method could quantify more than 90% of Cr(VI) in Cr-contaminated soils, especially those mixed with COPR, which proved to be a promising method for Cr(VI) analysis in soils, before and after remediation.

Keywords: hexavalent chromium; alkali digestion; Cr-contaminated soil; chromite ore processing residue; extraction (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
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