Removal of plutonium and americium from waste matrices by supercritical carbon dioxide extraction

Experimental determination and model correlation for the solubilities of trialkyl phosphates in supercritical carbon dioxide

The solubilities of a series of trialkyl phosphates in supercritical carbon dioxide have been investigated.

Supercritical fluid extraction and separation of uranium from other actinides

The feasibility of separating U from nitric acid solutions of mixed actinides using tri-n-butylphosphate (TBP)-modified supercritical fluid carbon dioxide (sc-CO2) was investigated. The actinides U, Np, Pu, and Am were extracted into sc-CO2 modified with TBP from a range of nitric acid concentrations, in the absence of, or in the presence of, a number of traditional reducing and/or complexing agents to demonstrate the separation of these metals from U under sc-CO2 conditions. The separation of U from Pu using sc-CO2 was successful at nitric acid concentrations of less than 3M in the presence of acetohydroxamic acid (AHA) or oxalic acid (OA) to mitigate Pu extraction, and the separation of U from Np was successful at nitric acid concentrations of less than 1M in the presence of AHA, OA, or sodium nitrite to mitigate Np extraction. Americium was not well extracted under any condition studied.

A rapid online estimation method for radiostrontium in soil samples using crown ether and supercritical fluid extraction

Crown ethers dissolved in suitable medium are well known to promote the extraction of alkali (M(+)) and alkaline-earth (M(2+)) cations from aqueous to organic phases. Di-tert-butyl-cyclohexano18crown6 (DTBDCH18C6) has been identified as an effective and selective extractant for Sr(II) from nitric acid medium. An attempt was made to evaluate the feasibility of (85,89)Sr recovery from synthetic soil samples (0.5 g; particle size: <100 μm) by SFE route (pressure: 200 kg/cm(2); T: 40 °C) employing DTBDCH18C6 dissolved in methanol/nitric acid medium as phase modifier. The effect of various experimental parameters such as (i) dynamic/static mode of extraction, (ii) time of equilibration (15-150 min during static mode of extraction using 3 mL of modifier), (iii) nitric acid concentration (1-6M), (iv) picrate as counter-anion, and (v) crown ether concentration in the modifier phase (2×10(-4)-2×10(-3) M) on Sr(II) extraction was studied. Based on these studies, 2×10(-4) M DTBDCH18C6 dissolved in methanol/4M HNO(3) was chosen as modifier and 30 min as equilibration time for batch mode employing 3 mL modifier solution in the static mode. Three successive batches employing 3 mL modifier solution (after each extraction stage) showed near quantitative recovery (>95%) of (85,89)Sr from soil samples. Dynamic mode extraction using 2×10(-4) M DTBDCH18C6 dissolved in methanol/4M HNO(3) as modifier suggested that near quantitative recovery (>95%) of (85,89)Sr could be achieved within 1h. By contrast, ~10% (137)Cs extraction was observed from soil samples under identical experimental conditions. These studies demonstrate the potential of the SFE technique for the analysis of (90)Sr in different environmental samples.

Design and adaptation of a novel supercritical extraction facility for operation in a glove box for recovery of radioactive elements

The design and development of a novel supercritical extraction experimental facility adapted for safe operation in a glove box for the recovery of radioactive elements from waste is described. The apparatus incorporates a high pressure extraction vessel, reciprocating pumps for delivering supercritical fluid and reagent, a back pressure regulator, and a collection chamber. All these components of the system have been specially designed for glove box adaptation and made modular to facilitate their replacement. Confinement of these materials must be ensured in a glove box to protect the operator and prevent contamination to the work area. Since handling of radioactive materials under high pressure (30 MPa) and temperature (up to 333 K) is involved in this process, the apparatus needs elaborate safety features in the design of the equipment, as well as modification of a standard glove box to accommodate the system. As a special safety feature to contain accidental leakage of carbon dioxide from the extraction vessel, a safety vessel has been specially designed and placed inside the glove box. The extraction vessel was enclosed in the safety vessel. The safety vessel was also incorporated with pressure sensing and controlling device.