title: Recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite clay by electrokinetics coupled with a permeable reactive barrier.
abstract: Zero-valent iron (Fe(0)) and magnetite (Fe3O4) were investigated as potential reductants in an electrokinetic/permeable reactive barrier hybrid system (EK/PRB) for the recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite. For the EK/Fe(0) PRB, regardless of the pH in the anode well, the system facilitated the reduction of Cr(VI) into Cr(III), but the recovery of the Cr(III) in the PRB was low. Conversely, the reduction of Cr(VI) occurred only in the PRB for the EK/Fe3O4 PRB. However, when the anode pH was not controlled and the soil pH values correspondingly decreased gradually from the anode side, a greater fraction of Cr(VI) sorbed onto the kaolinite; as a result, a lower amount of Cr(VI) migrated to the Fe3O4 PRB. In addition, it was found that the majority of Cr(VI) migrating to the Fe3O4 PRB retained its oxidation state without being converted into Cr(III). These two adverse effects were mitigated by maintaining the soil pH values at 6.8, but at the same time, 18% of Cr(VI) penetrated through the Fe3O4 PRB. The penetration of Cr(VI) through the Fe3O4 PRB was successfully prevented by increasing the reaction time through the introduction of a cation exchange membrane between the Fe3O4 PRB and the anode well.
authors: Department of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Yamaguchi, Japan. Electronic address: tsuzuki@yamaguchi-u.ac.jp.
authors: Tasuma
authors: T
authors: Suzuki
authors: Department of Sustainable Environmental Engineering, Faculty of Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Yamaguchi, Japan. Electronic address: p018fj@yamaguchi-u.ac.jp.
authors: Katsunori
authors: K
authors: Kawai
authors: Department of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Yamaguchi, Japan. Electronic address: r063vn@yamaguchi-u.ac.jp.
authors: Mai
authors: M
authors: Moribe
authors: Department of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Yamaguchi, Japan. Electronic address: niinae@yamaguchi-u.ac.jp.
authors: Masakazu
authors: M
authors: Niinae
mesh_terms: D002857:Chromium / Q000737:chemistry*; D004563:Electrochemistry; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D007501:Iron / Q000737:chemistry; D007616:Kaolin / Q000737:chemistry*; D007700:Kinetics; D008567:Membranes, Artificial; D010084:Oxidation-Reduction; D012989:Soil Pollutants / Q000737:chemistry*; D018505:Waste Management / Q000379:methods
chemical_list: D008567:Membranes, Artificial; D012989:Soil Pollutants; D002857:Chromium; D007616:Kaolin; D007501:Iron; D052203:Ferrosoferric Oxide
keywords: Electrokinetic remediation; Hexavalent chromium; Magnetite; Permeable reactive barrier; Soil contamination