Modeling of Yb(III) Sorption on Kaolinite by Using Single Oxide Surface Complexation Models
- PDF / 369,219 Bytes
- 8 Pages / 414.72 x 648 pts Page_size
- 76 Downloads / 211 Views
MODELING OF Yb(HI) SORPTION ON KAOLINITE BY USING SINGLE OXIDE SURFACE COMPLEXATION MODELS. Nicolas MARMIER,
, Jacques DUMONCEAU*, Jodi CHUPEAU***, Francine FROMAGE*
* Facultd des Sciences de Reims, Laboratoire de chimie de coordination BP 347 51062 Reims cedex ** C.E.A. C.E.N. Fontenay aux roses DCC/DSD/SCS/LCASH Bat 02 BP 6 92265 Fontenay aux roses CEDEX
***ANDRA-DEEC, route du panorama Robert SCHUMAN B.P.38 92266 Fontenay aux roses CEDEX
ABSTRACT
Surface complexation model was used to describe ytterbium sorption on kaolinite using surface acidity constants and surface complexation constants determined on alumina and silica. INTRODUCTION
The rare earth elements present strong chemical analogies with trivalent actinides, and may be used to develop methodologies and to quantify relevant processes. Nevertheless, their sorption behavior is poorly known. In this work, we study the sorption of ytterbium on kaolinite using surface complexation models. These are now widely acknowleged as valuable tools allowing both an understanding and quantification of the chemical reactions responsible for the sorbing properties of solids. Our aim is, in a first step, to determine surface parameters of two single oxides, alumina and silica, by means of an experimental method tested on iron oxides [ 1,2], and in a second step to use these parameters to describe surface reactions on kaolinite surface. This application of single oxide surface parameters to aluminosilicates has been already tested [3,4], and we withextend this approach to study the ytterbium sorption. So we have to make the following hypothesis: - the surface of kaolinite is composed of two differents sites, aluminol sites and silanol sites.
- these two sites keep their chemical properties whatever their environment may be. Using this approach, it is possible to calculate theorical titration curves for kaolinite and theorical Yb(III) sorption curves using a surface complexation model without surface constants fitting. The comparison of these curves with experimental ones will allow the validation of the hypothesis, which are consistent with the theorical model we use. REAGENTS AND APPARATUS Solid Phases.
The specific area, measured by the B.E.T. nitrogen adsorption method, is equal to 135.5 m2 .g"1 for alumina, 384 m2 .g9l for silica and 13.7 m2 .g"1 for kaolinite. We suppose that the hydratation equlibrium is achieved when both surface titration curves and sorption isotherms do not vary any more: this is observed after a stirring time equal to seven days for alumina, silica, and kaolinite. Solutions. The acid, base and sodium nitrate solutions are made from HNO 3, NaOH and NaNO 3 Merck. The Yb(N0 3)3 master solution is made from a 99.99 % pur Johnson Mattey oxide and titrated by E.D.T.A. complexometry with orange xylenol.
Mat. Res. Soc. Symp. Proc. Vol. 353 01995 Materials Research Society
1086
Apparatus. - Orion pI-Imeter 920
- Orion pH triode electrode 9157BN - Beckman UV-VIS Spectrometer 5240 All the measurements are carried out in a thermostated vessel a
Data Loading...
