Details
| Original language | English |
|---|---|
| Pages (from-to) | 411-425 |
| Number of pages | 15 |
| Journal | Radiochimica Acta |
| Volume | 96 |
| Issue number | 7 |
| Publication status | Published - 10 Jul 2008 |
| Externally published | Yes |
Abstract
Polynuclear hydroxide complexes play an important role for the hydrolysis of tetravalent thorium ions in aqueous solution, in particular for Th(IV) concentrations exceeding some [Th(IV)] = 10-4 M. Consequently, these polymers must be considered when describing hydrolysis of Th(IV) or dissolution processes of Th(IV) solids. In the past, considerable efforts were made to obtain equilibrium formation constants of these polymers and different stoichiometrics for dimers, tetramers and hexamers have been suggested. However, most information was obtained from indirect methods, in particular, from potentiometric titrations. In the present work, we present an approach of directly quantifying polymeric metal hydroxide complexes in solution. By nano-electrospray mass-spectrometry the degrees of polymerization, i.e. the numbers of Th4+ ions and the numbers of hydroxide ligands, and as a consequence, also the charges of the complexes are measured. All monoand polynuclear species which are present in solution are quantified simultaneously down to species contributing less than 0.1% of the total [Th(IV)] concentration. Solutions of [Th(IV)] = 6 × 10-6-10-1 M are investigated in HCl at [H+] = 10-4-0.1 M. More than 30 different polymeric complexes are observed with the general trend of increasing number of hydroxide ligands with decreasing acidity. A surprising finding is the presence of the pentamer Th5(OH)yz+, which was not described in the literature before. With decreasing Th(IV) concentration the stability field of polymers narrows continuously until polymers can no longer be detected below [Th(IV)] = 10-5 M.
Keywords
- Hydrolysis, Nano-electrospray, Polymerization, Thorium
ASJC Scopus subject areas
- Chemistry(all)
- Physical and Theoretical Chemistry
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In: Radiochimica Acta, Vol. 96, No. 7, 10.07.2008, p. 411-425.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Formation and hydrolysis of polynuclear Th(IV) complexes
T2 - A nano-electrospray mass-spectrometry study
AU - Walther, Clemens
AU - Fuss, Markus
AU - Büchner, Stefanie
PY - 2008/7/10
Y1 - 2008/7/10
N2 - Polynuclear hydroxide complexes play an important role for the hydrolysis of tetravalent thorium ions in aqueous solution, in particular for Th(IV) concentrations exceeding some [Th(IV)] = 10-4 M. Consequently, these polymers must be considered when describing hydrolysis of Th(IV) or dissolution processes of Th(IV) solids. In the past, considerable efforts were made to obtain equilibrium formation constants of these polymers and different stoichiometrics for dimers, tetramers and hexamers have been suggested. However, most information was obtained from indirect methods, in particular, from potentiometric titrations. In the present work, we present an approach of directly quantifying polymeric metal hydroxide complexes in solution. By nano-electrospray mass-spectrometry the degrees of polymerization, i.e. the numbers of Th4+ ions and the numbers of hydroxide ligands, and as a consequence, also the charges of the complexes are measured. All monoand polynuclear species which are present in solution are quantified simultaneously down to species contributing less than 0.1% of the total [Th(IV)] concentration. Solutions of [Th(IV)] = 6 × 10-6-10-1 M are investigated in HCl at [H+] = 10-4-0.1 M. More than 30 different polymeric complexes are observed with the general trend of increasing number of hydroxide ligands with decreasing acidity. A surprising finding is the presence of the pentamer Th5(OH)yz+, which was not described in the literature before. With decreasing Th(IV) concentration the stability field of polymers narrows continuously until polymers can no longer be detected below [Th(IV)] = 10-5 M.
AB - Polynuclear hydroxide complexes play an important role for the hydrolysis of tetravalent thorium ions in aqueous solution, in particular for Th(IV) concentrations exceeding some [Th(IV)] = 10-4 M. Consequently, these polymers must be considered when describing hydrolysis of Th(IV) or dissolution processes of Th(IV) solids. In the past, considerable efforts were made to obtain equilibrium formation constants of these polymers and different stoichiometrics for dimers, tetramers and hexamers have been suggested. However, most information was obtained from indirect methods, in particular, from potentiometric titrations. In the present work, we present an approach of directly quantifying polymeric metal hydroxide complexes in solution. By nano-electrospray mass-spectrometry the degrees of polymerization, i.e. the numbers of Th4+ ions and the numbers of hydroxide ligands, and as a consequence, also the charges of the complexes are measured. All monoand polynuclear species which are present in solution are quantified simultaneously down to species contributing less than 0.1% of the total [Th(IV)] concentration. Solutions of [Th(IV)] = 6 × 10-6-10-1 M are investigated in HCl at [H+] = 10-4-0.1 M. More than 30 different polymeric complexes are observed with the general trend of increasing number of hydroxide ligands with decreasing acidity. A surprising finding is the presence of the pentamer Th5(OH)yz+, which was not described in the literature before. With decreasing Th(IV) concentration the stability field of polymers narrows continuously until polymers can no longer be detected below [Th(IV)] = 10-5 M.
KW - Hydrolysis
KW - Nano-electrospray
KW - Polymerization
KW - Thorium
UR - http://www.scopus.com/inward/record.url?scp=46449128871&partnerID=8YFLogxK
U2 - 10.1524/ract.2008.1509
DO - 10.1524/ract.2008.1509
M3 - Article
AN - SCOPUS:46449128871
VL - 96
SP - 411
EP - 425
JO - Radiochimica Acta
JF - Radiochimica Acta
SN - 0033-8230
IS - 7
ER -