Studies of the effects of organic materials on the sorption of uranium(IV) and thorium(IV) on London clay and Caithness flagstones

The effects of the presence of cellulosic degradation products on the sorption of uranium (IV) and thorium(IV) on London clay and Caithness flagstones have been studied using the batch sorption method. Experimental conditions were chosen to simulate both those expected close to a cementitious repository (pH ∼11) and at the edge of the zone of migration of the alkaline plume (pH ∼ 8). Work was carried out (i) under baseline conditions, in the absence of organic materials; (ii) with 2 x 10-3M gluconate, acting as a well-characterised degradation product simulant; (iii) with authentic degradation products. The results show that the presence of authentic degradation products has a small effect on sorption and the presence of gluconate at a high concentration has a marked impact. (author)