Solubility of amorphous Th(IV) hydroxide – application of LIBD to determine the solubility product and EXAFS for aqueous speciation

• DOI: 10.1524/ract.2002.90.9-11_2002.485
• Publication Date: 2005-09-23T09:54:53Z
• Authors: Volker Neck; R. Müller; M. Bouby; M. Altmaier; J. Rothe; Melissa A. Denecke; Jae-Il Kim
• Keywords: Solubility equilibrium; Coulometry

Summary The solubility of amorphous Th(IV) hydroxide at pH 3.0–13.5 and the aqueous speciation < 4 are investigated in 0.5 M NaCl 25 °C. laser-induced breakdown detection (LIBD) is used to monitor initial formation thorium colloids during coulometric titration 1.2×10 −2 −1.0×10 −5 solutions range 2.7–4.5. accurate limit determined by this method comparable with data measured from undersaturation an X-ray solid precipitated higher dried room temperature. Based on hydrolysis constants selected literature, product Th(OH) (am) calculated be log K′ sp = −44.48 ± 0.24 K° −47.8 0.3 (converted I =0 SIT coefficients NEA-TDB). In other studies or hydrous oxide, considerably concentrations 3.5–5. Therefore, H + prepared careful examined ultrafiltration, LIBD absorption fine structure (XAFS) spectroscopy. These measurements demonstrate presence a large amount small colloids. Th L 3 edge EXAFS spectra these colloidal suspensions similar that solid.