Solubility Products and Complex Formation Equilibria in the Systems Uranyl Hydroxide and Uranyl Carbonate at 25°C and I = 0.1 M

Abstract

Uranyl hydroxide / Uranyl carbonate j Solubility products / Complexation SummaryThe solubility of uranyl hydroxide and uranyl carbonate and the formation constants of the complexes present in the supematant Solution were determined at 25°C in 0.1 M NaClOi solutions. The solubility products were found to be logA^,p= -22.21 and log/Csp= -13.29. respectively. In the pH ränge from 4.5 to 5.5 the hydroxo complexes (U02)2(0H)r (lg/? = 22.16), and (U02)3(0H)5^ (lg^ = 53.05) were found. Under the condition -11 <lg(C03")<-6 three mononuclear uranyl carbonate complexes. UO2CO3 (lg/J = 8.70), U02(C03)r (lg^= 16.33), and U02(C03)r (Ig/? = 23.92) exist.

Review of uranyl mineral solubility measurements

“…The discrepancy of the K sp values produced by Meinrath and Kimura [21] and Kramer-Schnabel [23] under an open atmosphere highlights the difficulty in obtaining consistent results. Meinrath et al [22] did characterize their mineral phase more thoroughly and obtained better-constrained data by measuring the solubility from supersaturated conditions as well as undersaturated conditions.…”

“…Another study that reports rutherfordine solubility measurements, performed by Kramer-Schnabel et al [23], conducted experiments from undersaturated conditions in an open system with CO 2 equilibrated with the atmosphere and in a closed system at constant CO 2 partial pressure. Characterization of pre-and post-experimental mineral phases by XRD confirmed the starting mineral as rutherfordine and that it was stable under the experimental conditions.…”

“…Kramer-Schnabel et al [23] measured the solubility of metaschoepite from supersaturation in 0.1 M NaClO 4 . The authors gathered data from pH 4.36 to 5.71 by adjusting the pH of uranyl nitrate solutions with sodium hydroxide and allowing the subsequent precipitate to reach equilibrium (3 to 14 days).…”

Solubility Product of Hexavalent Uranium Hydrous Oxide

“…Kramer-Schnabel et al 17) reported the log K sp value of À22:21 at 0.1 M NaClO 4 which would be extrapolated to log K sp value of À22:81 by the SIT correction. 9) They took into consideration the formation of a number of hydrolysis species including the (UO 2 ) 2 (OH) 2 2þ in the pH range 4.5-5.5.…”

Systematics of polymeric hydrolysis constants of actinide ions

“…Fig. 3 shows a comparison of the predicted solubility curve with the experimental results of U(VI) [15][16][17]. In this case, the predicted solubility curve and its component concentrations are calculated with the hydrolysis constants, which are predicted by the present model and are corrected by the specific ion interaction theory (SIT) [9,10].…”