The effect of ionic strength and Sraq upon the uptake of Ra during the recrystallization of barite

Felix Brandt, Martina Klinkenberg, Jenna Poonoosamy, Juliane Weber, Dirk Bosbach

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Recrystallization and solid-solution formation with barite is considered as relevant retention mechanism for 226Ra in long-term scenarios of nuclear waste management. Here, we studied the effect of ionic strength and the presence of Sr in solution upon the Ra-uptake kinetics and final Ra concentrations in solution by recrystallizing barite in solution with varying Sr and NaCl concentration and temperature for up to 1000 days. Final Ra-concentrations were interpreted based on thermodynamic modelling. Our results indicate a slight decrease of the retention potential of barite for Ra but little effect on the uptake kinetics due to the increase of ionic strength from. 0.1 mol/kg to 1.0 mol/kg of NaCl. The final concentrations at solid/liquid ratio of 0.5 g/kg are well described based on available thermodynamic models whereas at 5 g/kg additional Ra uptake probably due to kinetic effects was observed. On the contrary, the presence of Sr in solution can have a significant inhibiting kinetic effect on the uptake kinetics and lower the final Ra-uptake. In some cases, with low solid/liquid ratio or at ambient conditions, Sr completely inhibits barite recrystallization. In all other cases, Ra, Ba and Sr were taken up as thermodynamically predicted at the end of the experiments.

Original languageEnglish
Article number502
JournalMinerals
Volume8
Issue number11
DOIs
StatePublished - Nov 2 2018
Externally publishedYes

Funding

The research leading to these results has received partial funding from the German Federal Ministry of Education and Research (BMBF) ImmoRad project (project number 02NUK019C) and ThermAc project (project number 02NUK039D). We are grateful to F. Sadowski, K. Dahmen, A. Wilden, R. König and G. Modolo for their support. The authors would also like to thank five anonymous reviewers for their careful and constructive reviews which improved this publication.

Keywords

  • (Sr,Ba,Ra)SO solid solution
  • Barite
  • Celestine
  • Ionic strength
  • Nuclear waste management
  • Radium uptake
  • Recrystallization
  • Ternary solid solutions

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