Characterization of Reaction of Green Rust with Foreign Ions using X-ray Absorption Fine Structure

Abstract

Measurements of X-ray absorption fine structure (XAFS), that is X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), were performed for characterizing the reactions of hydrosulphate green rust (GR) with copper or nickel sulphate ions. Fe K edge XANES spectra showed that a part of Fe(II) in GR2 was oxidized by the addition of copper sulphate ions, while Fe(II) in GR was not oxidized by the addition of nickel sulphate ions. Cu K edge and Ni K edge XANES spectra showed that copper sulphate ions were reduced to zero charge copper in the GR suspension, whereas nickel sulphate ions were not reduced. Radial structural functions for iron obtained from Fe K edge EXAFS spectra indicated that the structure of GR consisted of corner sharing of structural units formed by FeO 6 octahedra. Radial structural functions for copper and nickel also indicated that copper sulphate ions were transformed to metallic copper with the face-centered cubic structure in the GR suspension, whereas the local structure of nickel sulphate ions were unchanged. XANES and EXAFS data of GR oxidized by a H 2 O 2 solution were also investigated for comparison.

Hybridization of Layered Iron Hydroxide Nanoclays and Conducting Polymer for Controlled Oxygen Scavenger

“…The photographic images of both GRs displayed in Figure 3 showed fine powdery state with greenish brown or black color, indicating the existence of Fe 2+ /Fe 3+ (for both samples) and PEDOT:PSS (in GR-PEDOT) in the powders. positions and shapes corresponded well to the EXAFS spectra of previously reported green rust [18,19].…”

“…There could be observed a strong first shell peak at 1.4 Å (non-phase-shift corrected) and a relatively small second shell peak at 2.6 Å (non-phase-shift corrected), attributed to Fe-O and Fe-Fe bonds, respectively. The peak positions and shapes corresponded well to the EXAFS spectra of previously reported green rust [18,19].…”

“…There existed a pre-edge for both GRs, implying the potential Jahn-Teller distortion around Fe. Those kinds of pre-edge could be interpreted as symmetry that allowed 1s → 3d electron transition [18]. Although the Fe(OH) 6 in GR is considered to have octahedral geometry, the real symmetry is rather assigned to D 3d due to the packing of octahedrons [28].…”

Present Status of Various Analytical Techniques for Characterizing the Composition and Structure of Material Surfaces

“…［A］ (a) -(e) は X 線光電子の取り出 し角を変えたときのスペクトルであり (f) は基板の Fe からのスペクトルである 711eV 付近の酸化物によるピ ークは 707eV 付近の金属のピークよりも高い 一方 ) か らオキシ水酸化鉄 (主にα-FeOOH) に構造変化する過程 を調べた結果を示す 16) Fig. 7…”