Uranyl nitrate-water system, phase

W. Davis, Jr., J. Mrochek, and R. R. Judkins. 1970. Thermodynamics of the two-phase water-uranyl nitrate-tributyl phosphate-Amsco 125-82 system. J. Inorg. Nucl. Chem. 32 1689. 

The MD simulations D - J focus on the demixing of completely mixed water/ C02/TBP/acid systems, which are "chaotic arrangements", also prepared by MD simulations (see methods). These systems, "perfectly mixed" at the microscopic level (probably more than they are in reality) are highly unstable. We want to investigate how they spontaneously evolve and relax, and in particular to which extent the aqueous and CO2 phases will separate, and how the acid and uranyl nitrate species will distribute once the equilibrium is reached. One critical issue, in relation with assisted extraction, is whether and under which conditions uranyl will be complexed by TBP and finally extracted to CO2. The pH-neutral D and E systems, described in more details in ref (28) are presented here for a purpose of comparison with the acidic ones F-J. 

However, the PIM s stability was accompanied by relatively poor separative performance. The transport of U across the membrane by TOPO proceeds by a similar scheme to that by TBP TOPO forms a neutral complex with uranyl nitrate which is extracted into the membrane. In this case, U was transported from a solution containing only uranyl nitrate and molybdenum nitrate into water. This means that the reaction had no driving force other than the difference in concentration of the respective metal on each side of the membrane. Under these circumstances, uphill transport (Fig. 10.2) and separation is impossible, and this system reflects that limitation. Less than 50% of the U in the source phase was transferred to the receiving phase. Additionally, the system was not able to completely separate U from Mo, leaving an appreciable quantity of Mo and U in both source and receiving phases. Nonetheless, this research clearly demonstrated the superiority of PIMs over SLMs in this application. 

The extraction of uranyl nitrate from an aqueous system Into trlbutyl phosphate (TBP) causes the displacement of water from the organic phase.----- The displacement la roughly... 

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