Formation of Goethite and Hematite from Neodymium-Containing Ferrihydrite Suspensions

Tetsushi Nagano1, †, Hisayoshi Mitamura1, †, Shinichi Nakayama1, ‡ and Satoru Nakashima2, §
1 Department of Environmental Safety Research, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki 319-1195, Japan
2 Department of Earth and Planetary Materials Science, Graduate School of Science, Hokkaido University, N10 W8, Sapporo 060-0810, Japan
Present address: Department of Environmental Sciences, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki 319-1195, Japan.
Present address: Department of Fuel Cycle Safety Research, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki 319-1195, Japan.
§ Present address: Interactive Research Center for Science, Tokyo Institute of Technology, O-okayama 2-12-1, Meguro, Tokyo 152-8551, Japan. E-mail of corresponding author: nagano@sparclt.tokai.jaeri.go.jp

Abstract: The effects of neodymium (Nd) on the transformation of ferrihydrite to iron oxides was studied. The possible isomorphous substitution of Nd3+ for Fe3+ in iron oxides was examined also. Nd was used as an inactive substitute of trivalent radioactive actinide elements. Hydrolysis of ferric nitrate solution containing 0–30 mole % of Nd formed Nd, Fe-rich ferrihydrite as initial precipitates, which were poorly crystalline. Aging of the Nd-containing ferrihydrite in 0.3 M OH at 40°C and at pH 9.2 at 70°C formed Nd-free goethite and Nd-substituted hematite. The abundance of these crystalline phases was related to Nd in the parent solutions. Phase abundance, unit-cell parameters, and peak width were estimated by use of the Rietveld method.

Key Words: Ferrihydrite • Goethite • Hematite • Neodymium • Powder X-ray Diffractometry • Rietveld Refinement • Transmission Electron Microscopy

Clays and Clay Minerals; December 1999 v. 47; no. 6; p. 748-754; DOI: 10.1346/CCMN.1999.0470609
© 1999, The Clay Minerals Society
Clay Minerals Society (www.clays.org)