Restoration of cadmium-contaminated paddy soils by washing with ferric chloride: Cd extraction mechanism and bench-scale verification

Tomoyuki Makino, Hiroyuki Takano, Takashi Kamiya, Tadashi Itou, Naoki Sekiya, Makoto Inahara, Yasuhiro Sakurai

研究成果: Article査読

93 被引用数 (Scopus)

抄録

The ability of FeCl3 to extract Cd from three paddy soils was compared with that of various irons, manganese, and zinc salts to elucidate the extraction mechanism. Manganese, zinc and iron salts (including FeCl3) extracted 4-41%, 8-44% and 24-66% of total Cd, respectively. This difference reflected the pH of the extraction solution, indicating that the primary mechanism of Cd extraction by FeCl3 is proton release coupled with hydroxide generation, as iron hydroxides are insoluble. Washing with FeCl3 led to the formation of Cd-chloride complexes, enhancing Cd extraction from the soils. FeCl3 effectively extracted Cd from all of the three soils compared to HCl that is a conventional washing chemical, when the concentrations of the two washing chemicals were between 15 and 60 mMc (at above extraction pH 2.4), while the corresponding extraction pH of FeCl3 was slightly higher than HCl. As HCl is the strong acid of complete dissociation, if excess amount of HCl was added to soil, it is possible to give the dissolution of clay minerals in soils. In contrast, proton release from FeCl3 is controlled by the chemical equilibrium of hydroxide formation. While soil fertility properties were affected by a bench-scale soil washing with 45 mMc FeCl3, adverse effects were not crucial and could be corrected. The bench-scale test confirmed the effectiveness of FeCl3 for removal of soil Cd. The washing had no negative effect on rice yield and lowered the Cd concentration of rice grain and rice straw in a pot experiment.

本文言語English
ページ(範囲)1035-1043
ページ数9
ジャーナルChemosphere
70
6
DOI
出版ステータスPublished - 2008 1月
外部発表はい

ASJC Scopus subject areas

  • 環境工学
  • 環境化学
  • 化学 (全般)
  • 汚染
  • 健康、毒物学および変異誘発

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