期刊
JOURNAL OF HAZARDOUS MATERIALS
卷 360, 期 -, 页码 17-23出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jhazmat.2018.07.086
关键词
Chromate; FeS; Coating; X-ray absorption near-edge structure (XANES); Permeable reactive barrier (PRB)
资金
- National Research Foundation of Korea [NRF-2016R1D1A1B04931643]
- KEITI [2014001810003]
- Ministry of Education, Science and Technology of the Korean Government
- Pohang University of Science and Technology (POSTECH)
This study investigates the feasibility of mackinawite (FeS)-coated sand in permeable reactive barrier applications to treat Cr(VI)-contaminated groundwater under anoxic conditions. For this, Cr(VI) sorption experiments were conducted using both coated and uncoated sands. Solution-phase Cr speciation and Cr K-edge X-ray absorption near-edge structure (XANES) analysis indicated the complete reduction of Cr(VI) to Cr(III) by coated sand. At pH 4.7, substantial amounts of Cr(III) remained in solution due to its unfavorable cationic adsorption at acidic pH. At pH 7.1 and 9.8, it was quantitatively immobilized by forming Cr(III)-bearing precipitates. In contrast, uncoated sand showed the decreasing Cr(VI) sorption with pH. In uncoated sand, magnetite impurities would mediate the partial reduction of Cr(VI). Thus, the pH-dependent sorption by uncoated sand was due to both unfavorable anionic Cr(VI) adsorption and its lesser reduction to Cr(III) with pH. Compared to uncoated sand, coated sand showed significantly increased Cr(VI) sorption at neutral to basic pH. By Fe K-edge XANES analysis, FeS was mainly responsible for Cr(VI) reduction by coated sand, with a green rust-like phase being the major Fe product. Since Fe(OH)(3) is not thermodynamically stable under the redox conditions favoring formation of green rust, Fe(III)-substituted Cr(OH)(3) likely represents a Cr(III)-bearing phase.
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