A COUNTER CURRENT EXPERIMENT FOR THE SEPARATION OF TRIVALENT ACTINIDES AND LANTHANIDES BY THE SETFICS PROCESS

ABSTRACT

The SETFICS process, a variation of TRUEX process, was developed for the recovery of Am and Cm from acidic waste solution and the separation of actinides (III) and light lanthanides. The process uses the general TRUEX solvent as the extracting reagent and a DTPA-sodium nitrate solution for selective stripping of actinides(III). The basic flow sheet is composed of four steps: extraction-scrubbing; acid stripping; actinide(III) stripping; and lanthanide stripping.

To demonstrate the usefulness of the SETFICS process, a counter current experiment was conducted using a real TRUEX product solution. Americium and curium were successfully recovered with a solution of 0.05 M DTPA-4 M NaNO₃ (pH 2.0). Although the actinide(III) product solution contained Sm and Eu, the decontamination factor of ¹⁴⁴Ce/²⁴¹Am was 72, and most of the light lanthanides, specifically La, Ce, Pr, Nd, were removed. At least 80 % of the lanthanides were separated from the Am and Cm end products. In order to minimize the acidity in the actinide(III) stripping step, the nitric acid which extracted with the trivalent metals was previously removed with a solution of 0.5 M NaNO₃ (pH 2.0) in the “acid stripping” step.     

SYNERGISTIC SELECTIVE EXTRACTION OF ACTINIDES(III) OVER LANTHANIDES FROM NITRIC ACID USING NEW AROMATIC DIORGANYLDITHIOPHOSPHINIC ACIDS AND NEUTRAL ORGANOPHOSPHORUS COMPOUNDS

ABSTRACT

New aromatic dithiophosphinic acids (R₂PSSH) with R = C₆H_5?, ClC₆H_4?, FC₆H_4? and CH₃C₆H_4? were synthesized, characterized and tested as potential separating agents for trivalent actinides over lanthanides. The extraction of Am(III), Eu(III) and other lanthanides was carried out from nitric acid medium with mixtures of R₂PSSHS and neutral organophosphorus compounds. There was no detectable extraction when R₂PSSHS were used alone as extractants for either Am(III) or Eu(III) (D_AM,EU.< 10^?3) under the experimental conditions used in this study. High separation factors (D_AM/D_EU > 20) with D_AM > 1 were achieved in the nitric acid range 0.1-1 mol/L by means of a synergistic mixture of bis(chloro-phenyl)dithiophosphinic acid + tributylphosphate (TBP), irioctylphosphine oxide (TOPO) or tributylphosphine oxide (TBPO). The high radiation resistance (up to 10⁶ Gy absorbed γ-doses) of the extractants was also demonstrated.     

COMPARISON OF NAPHTHENIC ACID,VERSATIC ACID AND D2EHPA FOR THE SEPARATION OF RARE EARTHS

Equilibrium data are presented for the separation of selected rare earths Including La, Dy, Yb and Y, using solvent extraction from a chloride system. The solvents examined are Naphthenlc acid, Versatic acid and D2EHPA In shellsol 2016 at 15°C. The data presented show that Yttrium has a similar distribution co-efflclent to the heavy rare earths In D2EHPA but the distribution co-efflclent is similar to the light rare earths In the carboxyllc acid systems (Versatic and Naphthenlc acid). This Indicates that carboxyllc acids could be used to separate yttrium from heavy rare earths and In combination with D2EHPA for the separation from materials containing all the rare earths.     

A MODEL FOR THE DISTRIBUTION OF ACID GASES BETWEEN AN AQUEOUS ALKANOLAMINE SOLUTION AND LPG

The model of Deshmukh and Mather (1981) is a popular method for correlating and predicting the vapor-liquid equilibria in systems containing acid gases (hydrogen sulfide and carbon dioxide) and aqueous solutions of alkanolamines. The model includes phase equilibrium between an aqueous liquid and a gas as well as chemical equilibrium in the aqueous phase. A recent review by Weiland et al. (1993) demonstrated the accuracy of the correlation. Presented here is a model based on that of Deshmukh and Mather (1981) for calculating the distribution of acid gases between two liquid phases - an aqueous phase and a non-aqueous liquid (typically a propane- or butane-rich liquid)

In the new model the phase equilibrium is modeled using a modified Henry's law approach. Fugacities of the components in the non-aqueous phase are calculated using the Peng and Robinson (1976a) equation of state. All of the parameters in the model are taken from the literature. Thus the model represents a prediction of the behavior. It is demonstrated that the predictions are in good agreement with the available experimental data