A spectroscopic study of uranyl speciation in chloride-bearing solutions at temperatures up to 250 °C

Uranium Transport in F-Cl-Bearing Fluids and Hydrothermal Upgrading of U-Cu Ores in IOCG Deposits

“…They suggest that highly charged uranyl chloride complexes, that is, UO 2 Cl 4 2− and UO 2 Cl 5 3− , are especially important at high temperature (>250°C). The recent in situ UV-Vis study of Migdisov et al [52] was unable to confirm this result in relatively dilute (<1.5 M) NaCl solutions; the discrepancy could be due to the highly concentrated nature of LiCl solutions in the Dargent et al [74] work or to deviations from the Beer-Lambert law caused by the wide range in ionic strengths investigated by Dargent et al [74] (e.g., [75]).…”

“…In general, we use the properties of U complexes selected by Bastrakov et al [30], which are mainly based on the NEA (Nuclear Energy Agency) review of Guillaumont et al [51]. Noticeable exceptions include uranyl chloride complexes, where we use the new properties obtained recently by Migdisov et al [52]. We also use the one-term extrapolation method of Gu et al [53] to propose new T-dependence for uranyl fluoride complexes based on the new knowledge of uranyl chloride complexes and U(VI) chlorides based on the knowledge of U(IV) fluoride complexes.…”

“…There is no experiment for uranyl fluoride complexes at elevated temperature. For UO 2 F + and UO 2 F 2 (aq), we extrapolated properties to 350°C using the one-term extrapolation method of Gu et al [53] based on the properties of UO 2 Cl + and UO 2 Cl 2 (aq) reported by Migdisov et al [52]. The new parameters of MRB model are listed in Table 4.…”

“…However, above 100°C, the logKs from Migdisov et al [52] become much higher than the values extrapolated using Bastrakov et al's [30] MRB model, indicating higher stability of UO 2 Cl + . For UO 2 Cl 2 (aq), the logKs from Migdisov et al[52] are larger than the values calculated using the NEA values[30]. Overall, Migdisov et al's[52] experimental study shows higher stability of UO 2 Cl + and UO 2 Cl 2 (aq) at elevated T (>100°C) compared with recommendations from NEA[51] used by Bastrakov et al[30].In our model, we chose to include only the complexes that were characterised by Migdisov et al[52], namely, UO 2 Cl + and UO 2 Cl 2 (aq).…”

“…For UO 2 Cl 2 (aq), the logKs from Migdisov et al[52] are larger than the values calculated using the NEA values[30]. Overall, Migdisov et al's[52] experimental study shows higher stability of UO 2 Cl + and UO 2 Cl 2 (aq) at elevated T (>100°C) compared with recommendations from NEA[51] used by Bastrakov et al[30].In our model, we chose to include only the complexes that were characterised by Migdisov et al[52], namely, UO 2 Cl + and UO 2 Cl 2 (aq). The UO 2 Cl 3 − complex was present only in small quantities in Migdisov et al's[52] experiments and is therefore not included in our model.3.6.…”