Coprecipitation of (14)C and Sr with carbonate precipitates: The importance of reaction kinetics and recrystallization pathways.
This study investigated the simultaneous removal of Sr(2+) and (14)CO3(2-) from pH>12 Ca(OH)2 solution by the precipitation of calcium carbonate. Initial Ca(2+):CO3(2-) ratios ranged from 10:1 to 10:100 (mM:mM). Maximum removal of (14)C and Sr(2+) both occurred in the system containing 10mM Ca(2+) and 1mM CO3(2-) (99.7% and 98.6% removal respectively). A kinetic model is provided that describes (14)C and Sr removal in terms of mineral dissolution and precipitation reactions. The removal of (14)C was achieved during the depletion of the initial TIC in solution, and was subsequently significantly affected by recrystallization of the calcite precipitate from an elongate to isotropic morphology. This liberated >46% of the (14)C back to solution. Sr(2+) removal occurred as Ca(2+) became depleted in solution and was not significantly affected by the recrystallization process. The proposed reaction could form the basis for low cost remediation scheme for (90)Sr and (14)C in radioactively contaminated waters (<$0.25 reagent cost per m(3) treated).
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
David J
DJ
Hodkin
School of Civil Engineering, University of Leeds, UK.
Douglas I
DI
Stewart
National Nuclear Laboratory, Sellafield, Cumbria, UK.
James T
JT
Graham
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK. Electronic address: I.T.Burke@leeds.ac.uk.
Ian T
IT
Burke
D002250:Carbon Radioisotopes / Q000737:chemistry*; D002254:Carbonates / Q000737:chemistry*; D011232:Chemical Precipitation; D007700:Kinetics; D008956:Models, Chemical; D013324:Strontium / Q000737:chemistry*
D002250:Carbon Radioisotopes; D002254:Carbonates; D013324:Strontium
Carbonate; Nuclear; Radiocarbon; Remediation; Strontium-90