Review of uranyl mineral solubility measurements

Evidence of isotopic fractionation of natural uranium in cultured human cells

“…Finally, our protocol made it possible to have Tris-carbonate uranyl complexes in the exposure solutions. Based on the thermodynamic constants available in the literature (43)(44)(45)(46), and from the different literature surveys on biological ligands of U(VI) (47-55), we obtained the theoretical speciation diagram of U in the exposure solution shown in Fig. 1.…”

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

“…Under most natural conditions, however, schoepite is metastable with a strong tendency to undergo structural transformation to more stable secondary phases, such as becquerelite (Ca(UO 2 ) 6 O 4 (OH) 6 Á8H 2 O) or compreignacite (K 2 (UO 2 ) 6 O 4 (OH) 6 Á7H 2 O) after incorporation of Ca and K, respectively (Sandino and Grambow, 1994;Wronkiewicz et al, 1996). A Na analogue of compreignacite (Na 2 (UO 2 ) 6 O 4 (OH) 6 Á7(H 2 O)) was tentatively identified among the alteration phases observed on spent fuel in contact with groundwater for six years , and is an important alteration phase due to the ubiquitous presence of dissolved Na in groundwaters (Gorman-Lewis et al, 2008a). The thermodynamic solubility and dissolution rates of common uranyl oxyhydroxides play a key role in controlling U release and mobility in environmental scenarios (Finch and Murakami, 1999).…”

“…As reviewed by Gorman-Lewis et al (2008a), the solubility of K-and Na-compreignacite has been rarely studied compared to the oxyhydroxide phases schoepite, metaschoepite, and becquerelite (e.g., Sandino and Grambow, 1994;Giammar and Hering, 2004). To our knowledge, there have been only two studies investigating the thermodynamic solubility of the K and Na endmembers, both conducted as batch experiments.…”

“…In solution, uranyl reacts with dissolved carbonate and Ca, forming stable neutral or anionic carbonate, Ca-carbonate, and hydroxo-carbonate aqueous complexes (Grenthe et al, 1992;Guillaumont et al, 2003). These complexes become important above pH 4 and increase mineral solubility (Gorman-Lewis et al, 2008a), creating mobile species that promote U(VI) migration in natural waters. Dissolution rates have not been reported for any uranyl oxyhydroxide minerals, and differences in rates at different pH and carbonate concentrations have not been investigated.…”

Leaching behaviour and the solution consumption of uranium–vanadium ore in alkali carbonate–bicarbonate column leaching

“…Although as it mentioned earlier in the section 2.2, Eh (mV) was determined against SCE, but for ease of comparison purposes it is converted against standard hydrogen electrode (SHE) and values are presented in Volts. The aqueous U(VI) carbonate system has been thoroughly studied (Kumar e al., 2011;Gorman-Lewis et al, 2008;Choppin, 2007;Morss et al, 2006;Sutton, 1999;Newton and Sullivan, 1985;Allard;1983) and there is little doubt about the compositions of the three monomeric complexes of general formula UO2(CO3), UO2(CO3)2 2-and UO2(CO3)3 4-present under the appropriate conditions as seen in Figure 6. In carbonate media, the uranium is converted to a series of carbonate complexes, UO2CO3 (maximum concentration at ca.…”