EluEx

Bufflex [from Buffelsfontein (South Africa), extraction] A process for extracting uranium from its ores, using a solution of an amine (Alamine 336). It was developed in South Africa, and was later replaced by Purlex. See also Eluex. 

Finally, structure-based predictive software is commercially available (such as CHROMDREAM, CHROMSWORD or ELUEX) for mobile phase optimisation in RPC. This software incorporates some features of the expert system, as it predicts the retention on the basis of the molecular structures of all sample components (which should be known) and the known behaviour of model compounds on various HPLC columns. No initial experimental runs are necessary as the retention data are calculated from the additive contributions of the individual structural elements to the retention, contained in the software databa.se and consequently optimum composition of the mobile phase is suggested. Such predictions are necessarily only approximate, do not take into account stereochemical and intramolecular interaction effects, and predicted separation conditions can be used rather as the recommendation for the initial experimental run in the subsequent optimisation procedure. 

Structure-based commercial optimization softwar (e.g., Chromdream, Chromsword, or Eluex) incorporate some features of the expert system, as the retention is predicted based on the additive contributions of thdS... 

Solvent extraction is applied either directly to the weakly acidic leach hquor (the method is known as the Purlex process in South Africa, and the Amex process in the USA) or to the strongly acidic eluate obtained from a preliminary ion-exchange treatment of the leach liquor (known as the Bufflex process in South Africa, and the Eluex process in the USA). In the Purlex process, a 5 /(i solution of a tertiary amine in kerosene is typically used to treat a leach liquor containing up to 1 g of uranium per litre (although concentrations as low as 0.04 g 1 may be encountered) at a pH value of 1 to 2. A modifier such as isodecanol (2-5%) is usually incorporated into the organic phase to prevent the formation of a third phase and to inhibit the formation of an emulsion. The extraction of uranium(VI) is usually considered to proceed according to reactions such as ... 

The combination of ion exchenge and liquid extraction is not new in the uranium industry and many enrly plants in the United Slates heve used this technique. Merritt hes written a comprehensive review of the extractive metallurgy of uranium with particular reference to North America. The Eluex plants operated in (he Untied States were eerentially similar to the Rossing plant described above, bot the ion-exchenge equipment was far less elegant. 

Federal Amencan Gas Hills, Wyoming 950 Continuous RIP (NHfJjSOi-H SO, Eluex + NHj... 

Lucky Me Uranium Gas Hills, Wyoming 1650 Moving bed (NH,),S04-H,S0, Eluex + NH,... 

Union Carbide Gas Hills, Wyoming 1200 Continuous RIP (NH ),S0,-H,S04 Eluex NH,... 

Western Nuclear Jeffrey Gty, Wyoming 1700 Continuous RIP (NH,)jS04-HiSO, Eluex -t- NH2... 

Disadvantages of sulfuric acid are (1) the low luranium concentration of eluate, (2) the high volume of eluant needed for complete elution, and (3) the high acid concentration to be neutralized if uranium is to be recovered from eluant by precipitation. The advantages of sulfuric acid are that it leaves the resin in the sulfate form, which adsorbs uranium more readily than the nitrate or chloride form, and it introduces no extraneous anions that must later be purged from the system. To facilitate use of sulfuric acid, the Eluex process, to be described later, was developed in this process uranium is removed from sulfuric acid eluate by solvent extraction rather than by neutralization and precipitation, and the acid is recycled to a subsequent elution cycle. 

Eluex process. Although it would be possible to recover uranium from the eluate leaving Fig. 

Figure 5.19 is a schematic flow sheet showing the Eluex process as used at the Federal-American Partners uranium miU, and the final steps for precipitating and calcining its uranium product. The Eluex process is a variant of the amine extraction (Amex) process described in Sec. 8.6. 

Figure 5.19 Eluex solvent extraction and yellow cake precipitation at Federal-American Partners uranium mill.

Expert systems to predict best initial separation conditions on the basis of sample component molecular structures ELUEX, CHROMDREAM, HPLC- METABOLEXPERT, ProDigest-LC, LABEL 165, 166,172, 173... 

Structure-based commercial optimization software (e.g., Chromdream, Chromsword, or Eluex) incorporate... 

Amine systems achieve higher uranium purity than organophosphorus systems (due to the greater selectivity of amines for uranium) and have lower extractant losses due to their lower aqueous-phase solubility. SX is applied either directly to the weakly acidic leach liquor (also known as the Purlex or Amex process, Vaal River West, South Africa) or to the strongly acidic eluate from an ion-exchange preconcentration treatment of the leach liquor (the Bufflex or Eluex process, Vaal River South, South Africa) (Nicol et al. 1987). A more modem variation (such as at Southern Cross Resources Uranium One, South Africa) is to treat the ore by pressure leaching followed by SX. 

---