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Effect of anthropogenic organic complexants on the solubility of Ni, Th, U(IV) and U(VI)

Felipe-Sotelo, Monica, Edgar, M., Beattie, T., Warwick, P., Evans, N.D.M. and Read, David (2015) Effect of anthropogenic organic complexants on the solubility of Ni, Th, U(IV) and U(VI) Journal of Hazardous Materials, 300. pp. 553-560.

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Abstract

The influence of anthropogenic organic complexants (citrate, EDTA and DTPA from 0.005 to 0.1 M) on the solubility of nickel(II), thorium(IV) and uranium (U(IV) and U(VI)) has been studied. Experiments were carried out in 95%-saturated Ca(OH)2 solutions, representing the high pH conditions anticipated in the near field of a cementitious intermediate level radioactive waste repository. Results showed that Ni(II) solubility increased by 2–4 orders of magnitude in the presence of EDTA and DTPA and from 3 to 4 orders of magnitude in the case of citrate. Citrate had the greatest effect on the solubility of Th(IV) and U(IV)/(VI). XRD and SEM analyses indicate that the precipitates are largely amorphous; only in the case of Ni(II), is there some evidence of incipient crystallinity, in the form of Ni(OH)2 (theophrastite). A study of the effect of calcium suggests that U(VI) and Ni(II) may form metal-citrate-OH complexes stabilised by Ca2+. Thermodynamic modelling underestimates the concentrations in solution in the presence of the ligands for all the elements considered here. Further investigation of the behaviour of organic ligands under hyperalkaline conditions is important because of the use of the thermodynamic constants in preparing the safety case for the geological disposal of radioactive wastes.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Chemistry
Authors :
NameEmailORCID
Felipe-Sotelo, Monicam.felipe-sotelo@surrey.ac.uk
Edgar, M.
Beattie, T.
Warwick, P.
Evans, N.D.M.
Read, Davidd.read@surrey.ac.uk
Date : December 2015
DOI : 10.1016/j.jhazmat.2015.07.060
Depositing User : Karen Garland
Date Deposited : 26 Sep 2018 13:45
Last Modified : 26 Sep 2018 13:45
URI: http://epubs.surrey.ac.uk/id/eprint/849458

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