372596247

74

RIKEN Accel. Próg. Rep. 24 (1990)

111*3-10. A Multitracer Study of the Adsorption of Metal Elements

on Hydrated Ferric Oxide

S.Y. Chen, S. Ambe, Y. Ohkubo, M. Iwamoto,

Y. Kobayashi, N. Takematsu, and F. Ambe

Adsorption is one of the most important pro-    ume of the suspension was then adjusted to 10 ml

cesses in geochemical behavior of metal elements.    with artificial seawater, and its pH to 7.5. Shaken

A multitracer techniąue using radioactive nuclides    in an 8-shape modę with a shaker at 25°C, the sus-

produced by heavy-ion irradiation is especially    pension was found to attain the adsorption eąuilib-

effective in studying the characteristic behavior of    rium within 60 min. After centrifugation, 5 ml of the

different elements simultaneously. This report    solution was pipetted from the supematant solution.

describes a multitracer study on the adsorption of    The y-ray spectrum of radioactive nuclides in the

various metal elements on hydrated ferric oxide. solution was measured with a Ge detector.

Carrier- and salt-free radioactive multitracer The distribution coefficients (A_d) of Y, Zr, Hf, Solutions were prepared from gold foil irradiated Mo, Re, Ru, Rh, Cu, Hg, In, Eu, Gd, Tb, Tm, with a ¹⁴N beam of 135 MeWnucleon as described Yb, Sn, and Nb were determined from the activities elsewhere.¹¹    of their radioactive isotopes. The results are shown

Eight milliliters of artificial seawater and 10 /u.1 of    in Table 1. The logarithmic plot of K_a against the

a multitracer solution was put into a polyethylene    electron binding energy I₂ of M^{4 2} is given in Fig. 1.

bottle. After pH was adjusted to 7.5 with a 1 mol    These data provide a basis for understanding the

dm^-3 Na2C0_;j solution, 0.5 ml of adsorbent suspen- removal mechanism of metal elements from sea-sion (2 mg/ml) was added to the solution. The vol- water.²⁾

Tabie 1. Distribution coefficients of metal elements for hydrated ferric oxide (ml mg^-1).*

Fe(0H)_:i

Y	2.63 x 10^s
Zr	9.12 x 10^4
Hf	1.07 x 10^5
Mo	6.46 x 10^3
Re	1.35 x 10^4
Ru	1.50 x 10^4
Rh	8.32 x 10^3
Cu	1.41 x 10^B
Hg	1.26 x 10^5
In	1.58 x 10^4
Eu	2.51 x 10^5
Gd	5.75 x 10^5
Tb	1.05 x 10^5
Tm	3.72 x 10^r>
Lu	2.63 x 10^5
Yb	5.27 x 10^4
Sn	2.27 x 10^4
Nb	5.39 x 10^4

* The concentration of a sorbent is 0.1 mg-ml \

OL--1- . 4 A- A , ■ I *■ —-*--¹-->

o 20    40    60    80    100

Electron Binding Energy. I?. (eV>

Fig. 1. Logarithmic distribution coefficients K_d of metal elements are plotted against electron binding energies.

References

1)    S. Ambe, S.Y. Chen, Y. Ohkubo, Y. Kobayashi, M. Iwamoto, and F. Ambe: This Report, p. 73.

2)    S.Y. Chen, S. Ambe, Y. Ohkubo, M. Iwamoto, Y. Kobayashi, N. Takematsu, and F. Ambe: ibid., p.

p. 75.