Densities of supercritical fluids containing CO2 and tri-n-butylphosphate

Abstract

The densities of supercritical fluids consisting of CO2 and 1) tri-n-butylphosphate (TBP), 2) a TBP solution containing HNO3, and 3) UO2(NO3)2·2TBP were experimentally measured using a variable-volume-type view cell at 313, 323 and 333 K. The densities of the fluids increased with an increase in pressure, and decreased with an increase in temperature. The densities were expressed as a function of pressure for each mole fraction of TBP in the supercritical fluids consisting of CO2 and the organic solution at 15-30 MPa. When the mole fraction of TBP in the fluid of CO2 and UO2(NO3) 2·2TBP was less than 0.01, the molar volume of the fluid calculated from its densities was smaller than that of CO2 due to negative partial molar volume of the complex, which showed characteristics of a supercritical fluid dissolving solutes. © Atomic Energy Society of Japan.