Photon Factory Activity Report 2004 #22 Part B (2005)
Chemistry

7C/2002G234

Structural study of Ni complexes in the solvent extraction system
Hirokazu NARITA*1, Mikiya TANAKA1, Tsuyoshi YAITA2, Yoshihiro OKAMOTO2
1
National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba,
Ibaraki 305-8569, Japan
2
Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan

Experimental
The Ni-LIX84I (Ni-L) and Ni-D2EHPA (Ni-D)
solution complexes were prepared by solvent extraction:
LIX84I or D2EHPA in n-dodecane − NiSO4 solutionadjusted to the appropriate pH value using NaOH solution.
The Ni-phthalocyanine (Ni-Pc) and Ni aqueous solution(Ni-Aq) and samples were prepared by pressing the Ni-Pc
solid (Aldrich) and by dissolving NiCl2 into water,
respectively. All of the XAFS spectra were measured intransmission mode at the BL-7C station in the KEK-PF.
The experimental data were analyzed by WinXAS Ver.
3.0 [2] and fit using theoretical phase and amplitudes
calculated from the program FEFF 8 [3].
Results and Discussion
Figure 1 shows the Ni K-edge XANES spectra of theNi-L, Ni-D, Ni-Aq and Ni-Pc samples. The spectrum ofthe Ni-D complex is significantly different from that ofthe Ni-L one but similar to that of Ni-Aq. Since the Ni(II)aqueous solution has six-coordinated Ni ions [4], theNi(II) ion in the Ni-D complex would be octahedral. The
Ni-L complex shows almost the same spectrum as the NiPc complex. In the Ni-Pc complex, the Ni(II) ion isX-ray absorption

Ni-L
Ni-D
Ni-Aq
Ni-Pc

8.32

8.34

8.36

8.38

Energy / keV

Fig. 1 Ni K-edge XANES spectra.

coordinated with nitrogen atoms in a square planar
geometry [5]. Additionally, these XANES spectra have adistinct peak at ~8335 eV, which is attributed to the 1s•4pz
transition. This peak is characteristic of a square planar
metal complex [6]. Therefore, the Ni(II) ion in the Ni-L
complex would be square planar.

Ni-L
Ni-D

| FT |Introduction
The recently growing demand for electroless nickel
plating has increased the need for the recovery of nickel.
We are now studying the nickel(II) extraction properties
using LIX84I (2-hydroxy-5-nonylacetophenone oxime)
and D2EHPA (bis(2-ethylhexyl) phosphoric acid) [1].
However, the structures of their extracted complexes arestill obscure. In this study, we have investigated thecoordination structures of nickel(II) complexes with
LIX84I and D2EHPA by the XAFS method.

012

34R/ ÅFig. 2 Fourier transforms of Ni K-edge EXAFS spectra.
The phase shifts are not corrected.
The Fourier transforms of the Ni K-edge EXAFS
spectra are shown in Fig. 2. The first peak in the spectrumof the Ni-L corresponds to the Ni-O/-N(oxime)
correlations. In the spectrum of the Ni-D, the first peak
appears at a larger R. This peak corresponds to the NiO(phosphoric acid or water) correlations. The results ofthe curve fits for the first peak indicate the presence of
4.1(6) O/N atoms at 1.85(1) Å for the Ni-L and 5.6(9) Oatoms at 2.04(1) Å for the Ni-D. Their coordination
number is consistent with the XANES data; square planar
for the Ni-L and octahedral for the Ni-D. The differencein the bond distance between the Ni-L and Ni-D (0.19 Å)
is similar to that of the ionic radius between the four andsix coordination of Ni(II) (0.14 Å) [7].
References[1] M. Tanaka et al., “Proceedings of EPD Congress
2004”, 2004, TMS, Pennsylvania, p. 681.
[2] T. Ressler, J. Synch. Rad., 5, 118 (1998).
[3] A. L. Ankudinov et al., Phys. Rev. B 58, 7565 (1998).
[4] H. Ohtaki et al., Chem Rev. 93, 1157 (1993).
[5] C. J. Schramm et al., J. Am. Chem. Soc., 102, 6702
(1980).
[6] R. A. Scott, Physica B 158, 84 (1989); L. X. Chen etal., Science, 292, 262 (2001).
[7] R. D. Shannon, Acta Cryst., A 32, 751 (1976).
* hirokazu-narita@aist.go.jp

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