Study on uptake of europium by the thin film of apatite and smectite mixture using RBS and micro-PIXE

Uptake of Eu, one of the rare earth elements, by a thin film of apatite and smectite mixture has been studied. The thin film of approximately few tens of im in thickness was contacted with Eu solution between 1.0 x 10(-5) and 1.0 X 10(-3) mol l(-1) for 2 days at 25 degreesC and at pH 4.5. After sepa rating the thin film from the solution, depth and spatial distributions of Eu were determined by Rutherford backscattering spectroscopy (RBS) system a nd micro-proton-induced X-ray emission (mu -PIXE) analyzing system, respect ively, in the TIARA facility of Japan Atomic Energy Research Institute. RBS spectrum shows that Eu is distributed from the surface to deeper position. This indicates that Eu is not only sorbed on the surface of the thin film, but also penetrates to deeper from the surface. The spatial distribution o f Eu obtained by mu -PIXE does not correspond to Si but to P. This is the d irect evidence that most of the sorbed Eu are associated with apatite in th e thin film. Therefore, it is concluded that RBS and mu -PIXE analyses are effective to examine the sorption behavior of elements on the mixture. (C) 2001 Elsevier Science B.V. All rights reserved.