The Role of Colloids in the Migration of Radioelements

Ziel

The objectives of the present investigation is to quantify the behaviour of colloids under varying chemical conditions by means of suitable laboratory experiments.
The aim is to derive thermodynamic equations, which may be used for the modelling of their fate in natural systems.
If this is not possible because of the very complicated nature of the system, empirical response functions will be derived.
To narrow the field of interest, the study will focus on humic acids, whose importance in natural systems is well recognized.
Only one humic acid, purchased as sodium humate from Aldrich-Chemie, D-7924 Steinheim, Germany, will be studied.
The objectives of the present investigation is to quantify the behaviour of colloids under varying chemical conditions by means of suitable laboratory experiments. The aim is to derive thermodynamic equations which may be used for themodelling of their fate in natural systems. The study focuses on humic acids, whose importance in natural systems is well recognized. Despite the fact that humic acids isolated from different places deviate in composition and probably also in structure, it is expected that they exert a similar overall behaviour although not identical interaction constants.

A stock solution of the selected humic acid is being characterized and a qualitative reaction pattern established. A stock solution of the selected sodium humate has been dialyzed for 14 days to remove impurities of neutral salts. During this process the continuous leaching of coloured components was observed, which could be the result of a depolyermization reaction in the humate solution.
It has been observed that the humate solution does not form a visible precipitate with a one molar sodium chloride solution, but does so in a saturated solution. Flocculation occurs with the addition of magnesium and calcium salts, in which respect the latter is more effective.
Work programme:

1. To collect useful information on humic acid behaviour, which can support the present investigation.
2. To study and quantify flocculation processes induced by the addition of polyvalent cations in competition with other ions.
3. To follow the distribution of trace elements, R.E. (Rare Earth) between flocculate and solution. If possible the amount of cations bound to dispersed humic acids will also be determined.
4. As a tentative model for the thermodynamic interpretation of the experimental data the humic acids will be modelled as finely dispersed ion-exchangers with a possible limited miscibility of surface phases.
5. If the suggested model is not found satisfactory, an empirical expression describing the behaviour of the selected humic acid will be derived.

Wissenschaftliches Gebiet

Programm/Programme

FP2-RADWASTOM 4C - Specific research and technical development programme (Euratom) in the field of management and storage of radioactive waste, 1990-1994

Thema/Themen

A.4.3 - Radionuclide migration in the geosphere

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

CSC - Cost-sharing contracts

Koordinator

RISOE NATIONAL LABORATORY

EU-Beitrag

Keine Daten

Adresse

Frederiksborgvej 399
ROSKILDE
Dänemark

Gesamtkosten