Solubility and sorption of protactinium in the near-field and far-field environments of a radioactive waste repository

Abstract

The solubility and sorption of protactinium were studied for typical near-field and far-field chemical environments. The apparent solubility limit of protactinium in the near field at pH 11–12 was about 10^–10M. Sorption on to all of the solid phases studied was typically high, with values of the distribution ratio, R_D, ranging from 10² to 10⁶ ml g^–1. These values of R_D varied with the phase separation technique, the initial concentration of protactinium and the water to rock ratio. This variation in R_D was in part attributable to the formation of large polymeric (or agglomerated) species under all the experimental conditions considered.