title: Simultaneous and continuous stabilization of As and Pb in contaminated solution and soil by a ferrihydrite-gypsum sorbent.
abstract: For the increasing need of stabilization both cationic and anionic metal(loid)s simultaneously, we newly developed a metal sorbent (FIXALL), consisting mainly of ferrihydrite and gypsum. The objectives of this study were to determine the molecular mechanisms of Pb and As stabilization in an aqueous system and to examine a simultaneous and long-term (up to 754days) effect on Pb and As stabilization in an anthropogenically contaminated soil using the FIXALL sorbent. When the solution contained a low concentration of Pb (5mgL-1), the mechanisms of Pb removal by FIXALL were based chiefly on the formation of inner-sphere surface complex with ferrihydrite. In the highly concentrated Pb solution (1200mgL-1), contrarily, the removal of Pb by FIXALL was the direct consequence of the dissolution of gypsum and subsequent precipitation of PbSO4, which strengthens the drawback of low capability of ferrihydrite for Pb removal. Regardless of initial concentrations, the primary mechanism of FIXALL for As stabilization is attributed to the formation of inner-sphere surface complex with ferrihydrite. A contaminated soil study demonstrated that FIXALL could decrease the concentration of water soluble As and Pb simultaneously and continuously for 754days without notable changes in their chemical species and soil pH.
authors.affiliation: Tokyo University of Agriculture and Technology, Japan; currently in Obayashi Corporation, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kameda
authors.affiliation: Tokyo University of Agriculture and Technology, Japan. Electronic address: yhashim@cc.tuat.ac.jp.
authors.forename: Yohey
authors.initials: Y
authors.lastname: Hashimoto
authors.affiliation: National Taiwan University, Taiwan.
authors.forename: Shan-Li
authors.initials: SL
authors.lastname: Wang
authors.affiliation: Ishihara Sangyo Kaisha, Ltd, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Hirai
authors.affiliation: Ishihara Sangyo Kaisha, Ltd, Japan.
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Miyahara
keywords: Metal immobilization; Soil pollution; Sorption; XAFS