A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics

SOLVENT EXTRACTIONin series into a chain. The aqueous feed flows one way while the organic flows the other. Incommercial practice 50 or more cells will form a circuit. The most difficult separation tends to bethat between Nd and Pr, and, in SX behavior, Yttrium fits into the Ln series near Dy or Ho.Passing a mixed-Ln-and-Y feedstock through an SX circuit will result in a cut into twofractions. A single element could be cut off from one end of the group or, alternatively, the mixedfeedstock can be split into two fractions, each still containing several elements. The choice willdepend on economics, on the relative demand for the mixture or the single element. Differentprocessors may well follow different steps to reach an individual pure element although using thesame precursor concentrate.Liquid-Liquid Counter-Current ExtractionSimplified SX-CircuitRecycled OrganicExtraction Feed Scrubbing StrippingCells CellOutputStreamInputFeedProductStream(B + C) (A + B + C) (A)AcidThe diagram indicates the material flow paths within a typical SX circuit. Here the desiredproduct, A, is preferentially concentrated in the organic phase and, after removal of the"contaminants" B and C in the scrub section, is stripped from the organic by an acid stream.42