Solubility Product of Hexavalent Uranium Hydrous Oxide

Abstract

The solubility of U(VI) hydrous oxide was measured in the hydrogen ion concentration (pH c ) range from 4 to 6 at 25AE1 C in a NaClO 4 solution. The experiment was carried out by oversaturation method at ionic strength I¼0:1, 0.5 and 1.0 and by undersaturation method at I¼1:0. The solid phase was found to be composed of a mixture of UO 3 . 2H 2 O and UO 2 (OH) 2 by XRD. The concentration of U(VI) was measured by inductively coupled plasma mass spectrometry (ICP-MS), and was analyzed to obtain the solubility products (K sp ), by taking into account the participation of the U(VI) hydrolysis species such as (UO 2 ) 2 (OH) 2 2þ . By using the literature values of the hydrolysis species and by using the specific interaction theory (SIT), the log K sp value at the standard state (I¼0) was determined to be log K sp ¼À22:46AE0:10. Possible differences in the log K sp values due to different solid phases were recognized.

Nanoscale UO2 and novel complex U(IV)-sulphate phase formation from electrolytically reduced uranyl sulphate solutions

“…1, experimental data are also shown where attention was paid to control the solute oxidation state and to minimise the effect of colloids present in the solution [11,12,15,16]. The experimental solubility limits for U(VI) agrees well with the calculations.…”

“…1. Theoretical solubility limits of U(IV) and U(VI) species in aqueous solutions [13,14] and experimental determinations for U-chloride solutions [11,12,16]. Compounds shown beside each equilibrium line symbolize the solid phase precipitating on exceeding these conditions.…”

Uranium sorption on bentonite modified by octadecyltrimethylammonium bromide

“…The ionic products values: pI = −log[UO 2 2+ ][OH − ] 2 given in Table 2 are close to 22.46, the value of UO 2 (OH) 2 solubility product [50]. Fig.…”

Systematics of polymeric hydrolysis constants of actinide ions

“…For the lack of information, the ion interaction parameter values for polymeric species are temporarily assumed to 0.5, 0.46, −0.06, 0, −0.09 and −0.16 for net ionic charges of +3, +2, +1, 0, −1 and −2, respectively. Also, the solubility limiting solid phase is assumed to be UO 3 ·2H 2 O with the solubility product value of log K • sp = −22.46 [16] and to be Na 2 U 2 O 7 ·xH 2 O with log K • sp = −29.45 [17]. As shown in Fig.…”

“…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].…”