Abstract
Ferrous sulfate (FeSO4) and calcium polysulfide (CaS5) stabilization are practical approaches to stabilizing hexavalent chromium (Cr(VI))-contaminated soil. The leachability and stability of Cr(VI) and Cr are important factors affecting the effectiveness of stabilized Cr(VI)-contaminated soil. This study compared the leachability and stability of Cr(VI) and Cr in Cr(VI)-contaminated soil stabilized by using FeSO4 and CaS5. The contaminated soil was characterized before and after stabilization, and the effectiveness of FeSO4 and CaS5 stabilization was assessed using leaching, bioaccessibility, alkaline digestion, sequential extraction, and X-ray diffraction tests. Results showed that FeSO4 and CaS5 significantly reduced the leachability and Cr(VI) content in the contaminated soil. The acid-buffering capacity and stability (leachability, bioaccessibility, speciation distribution, and mineral composition) of the Cr(VI)/Cr and Cr(VI) content of CaS5 were better than those of FeSO4. This study demonstrated that CaS5 had a better effect than FeSO4 on the stabilization of Cr(VI) in Cr(VI)-contaminated soil. The CaS5 significantly enhanced the stabilization and immobilization of Cr(VI) and reduced its leachability and toxicity.
Highlights
Soil contamination by chromium (Cr) is a serious problem in China [1,2,3]
Toxicity characteristic leaching procedure (TCLP), simplified bioaccessibility extraction test (SBET), alkaline digestion, sequential extraction, and X-ray diffraction (XRD) tests were performed on Cr(VI)-contaminated soils
This study compared the leachability and stability of FeSO4 - and CaS5 -stabilized Cr(VI)This studysoils
Summary
Soil contamination by chromium (Cr) is a serious problem in China [1,2,3]. Cr is released into the soil by various industries, including the wood preservation, leather tanning, chromate manufacturing, and electroplating industries [4]. Cr in soil occurs primarily in its Cr(III) and Cr(VI) redox states; Cr(III) is a nutrient for plant growth, whereas Cr(VI) is a dangerous species and human carcinogen [5]. Chemical reduction removes Cr(VI) rapidly and effectively based on the use of reducing agents, such as ferrous sulfate, calcium polysulfide, or sodium bisulfate, followed by precipitation as Cr(OH)3 [6]. Calcium polysulfide (CaS5 ) and ferrous sulfate (FeSO4 ) are promising reagents that have been used at many Cr-contaminated sites and for chromite ore-processing residue (COPR).
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