TTA extractions

Stability constants of the complexes formed between Pu(III), Pu(IV), and HSOi, were determined in 1 M acid media by measuring the decrease in extraction (either into TTA-toluene or ion-exchange resin) with increasing concentration of HSO4 in the aqueous solution. Because of very different degrees of extraction for Pu(III) and Pu(IV) and the imposed requirement of 1 M acidity, Pu(IV)-HSOit complexation was studied by TTA extraction, while the Pu(III)-HSOit system was studied by cation exchange. 

The Pu(IV)-HS0u System. In the Pu(IV)-HS0i system, a series of preliminary experiments was necessary to establish the stoichiometry of the TTA extraction process with respect to [H+] and... 

After the stipulated leaching period, the waters were sampled before and after filtration through 0.05 ym Nuclepore filters and the oxidation-state distribution of plutonium in the filtrates was determined as follows PrF3 carrier precipitation for Pu(III) and (IV), PrF3 precipitation following NaHS03 reduction for total plutonium, and thenoyltrifluoroacetone (TTA) extraction... 

All experiments were done in an atmospheric control chamber (initially nearly 100% Ar, <60 ppm 02, and undetectable levels of 002) Aliquots of the Np(IV) stock solution were adjusted with NaOH to an approximate pH value of 12 to precipitate the brown Np(IV) hydrous oxide(11). These suspensions were centrifuged and the supernatants were discarded. The Np solids were resuspended and the pH of the suspensions (approximately 10 mg Np solid/30 ml solution) were adjusted with HC1 or NaOH to pH values between 4 to 12. No further adjustments in the pH values were made. Some of the freshly precipitated Np(IV) hydrous oxide was redissolved in acid and the Np oxidation state was analyzed by the TTA extraction procedure. As before, approximately 90% of the Np was measured to be in the reduced state. 

The extraction of Pa(IV) by benzoylacetone (HBA) from perchloric acid and sodium perchlorate was investigated in a recent study of the equilibria in diketone extraction. The indicated reaction is reported to be the same as that given in Eq. (8), where M = PaO or Pa(0H) + (79). Diketones have also been used in the study of aqueous complexation. Oxalate (80), sulfate, and fluoride complexing of Np(IV), Pu(IV) and Th(IV) have been studied by thenoyl trifluoroacetone (TTA) extraction. The Dj is always higher when TTA is dissolved in benzene than when it is dissolved in ii-hexane (81), which is contrary to the usual observation of higher D s in aliphatic diluents. 

Figure X-1 Experimental distribution coefficients of Th(IV) in the TBP extraction study of [2006NEC/ALT] (aqueous phase 0.05-3 M NaNOs + 0.02 M HNO3, 22°C) and the TTA extraction study of [1950DAY/STO] (aqueous phase 0.5 M H(C104-N03), 25°C) and data evaluation using both the ion interaction model (dashed lines) and the nitrate complexation model (solid lines).

These authors determined the parameters of Eq. (3) for all available experimental data on TTA extractions and calculated pHgQ, the pH at which 50% of the ion is extracted by equal volume phases into 0.2 M TTA in benzene. They displayed some of these data in the form of a periodic table to show the trends in extractability of the elements (see Fig. 35). In cases in which the pH q value is negative only HCl data are given, while other data may be for a variety of acids and acid-salt combinations. The reader is referred to the original paper for more detail. However, this figure shows that the quadrivalent ions are much more extractable than others. 

U-fission product mixtiires (extraction of quaternary alkylammonium-plutonyl nitrate complex into hexone-TTA extraction... 

Rider U and Pu determination in highly irradiated fuel. (Hexone extraction, TTA extraction) 126... 

Rydberg Separation of Pu from U and fission products (adsorption of Zr-Nb on silica gel, preciditation of CuS, TTA extraction) 132... 

Sheidhauer Pu from environmental water samples (chemisorption on CaFg, TTA extraction) 137... 

Perkins Determination of Pu in urine (PrFn precipitation, TTA extraction) 155... 

The sample is pre-treated if necessary, with either H Og or by precipitating LaF3 and dissolving in A1(N03)3-HN03. The pre-treatment destroys any polymer vidiich may be present and assures the proper valence state (IV) for the TTA extraction. Pu(IV) is extracted from 2 M HNO3 and stripped into 10 M HNO3, evaporated onto a plate, and counted. Yield is quantitative. 

Extract immediately the Pu two times for 20 min with 2-nnl portions of 0.2 M TTA (thenoyltrifluoroacetone) in xylene. Scrub each in turn vrith solutions prepared in step 6. Save the aqueous phase for U. Combine the TTA extracts and add a few crystals of trichloroacetic acid. 

Mount the combined TTA extracts on a Pt plate for or-pulse analysis. 

Pu(IV) is spearated by chemisorption on solid CaFg as the concentration stepj and further purified with two TTA extraction cycles. The chemisorption step has been shown to be quantitative and very efficient. The sensitivity can be made very great, as low as 0.7 X 10" p Ci/ml by taking a large sample. 

Micro amounts of Pu are isolated by lanthanum fluoride coprecipitation, thenoyltrifluoroacetone (TTA) extraction, and electrodeposition. The a activity is measured by proportional counting or by autoradiography. 

A comprehensive review of TTA extraction by Poskanzer and Foreman has recently appeared which summarizes known extraction coefficients (P4). The pH values corresponding to 50 extraction Into 0.2 M TTA dissolved In benzene are shown In Figure 23. Using these values and the curves of per cent extraction vs. pH-pH Q shown In Figure 24 the optimum pH for separation of two or more elements can be determined (P4). In In most cases the value of X to be used In Figure 24 should be the oxidation state of the species extracted. The values of X to be used for exceptions to this rule are shown In parenthesis in Figure 23. pH-pH Q represents the variation of the pH of the aqueous phase from the pH for 50 per cent extraction. 

Separation factors for TTA extraction of trivalent lanthanides and actinides from Stary (1966) (TTA/toluene) and Alstad etal. (1974) (TTA/Caj. 

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