Interaction of uranium from seepage water with hydroxyapatite

Column experiments (in a quartz matrix) assisted by batch experiments helped to quantify and characterize the uranium(VI) retardation by hydroxyapatite, regarded as a highly efficient component of reactive barrier concepts for (radio) toxic contaminants. The sorption of uranyl ions onto phosphate groups is as important as their sorption onto silanol groups, outweighing the low phosphate content. In column experiments retardation factors ranging around 30 were observed. The elution of uranium is governed by two processes of different rate (and probably reversibility) which is consistent with the spectroscopic findings.