Patent GB-779930-A (GB)
Title: Process of separating trivalent rare earths from one another
IPC: C01F17/17
Filed: 1955-07-01
Abstract: Trivalent rare earths are separated from each other by subjecting a mixture of water-soluble rare earth metal salts to a liquid-liquid extraction between an aqueous phase capable of dissolving the rare earth salts and a water immiscible organic phase comprising at least one ketone or aldehyde having 5 to 8 carbon atoms, or a mixture of such a ketone or aldehyde with a water miscible ether having 6 to 10 carbon atoms.  The rare earths are preferably in the form of nitrates but they may be employed as salts of perchloric, alkyl sulphuric, alkyl phosphoric acids or organic acids such as lactic acid.  The aqueous phase preferably contains a salting out agent such as lithium, calcium, zinc or ammonium chlorides or nitrates or magnesium chloride.  Examples, which are confined to the treatment of nitrates (see Group III) refer to the use of n-pentanone, methyl pentanone, n-octanone, cyclohexanone, a -ethylhexyl aldehyde, benzoic aldehyde, pentanol and a 1 : 2 mixture of furfural and cyclohexanone.ALSO:Trivalent rare earths are separated from each other by subjecting a mixture of water soluble rare earth salts to a liquidliquid extraction between an aqueous phase capable of dissolving the rare earth salts and a water immiscible organic phase comprising at least one ketone or aldehyde having from 5 to 8 carbon atoms or a mixture of such a ketone or aldehyde and a water immiscible ether having from 6 to 10 carbon atoms, the proportion of ketone to ether preferably being between 0.5:1 and 1:0.5.  The rare earths are preferably in the form of their nitrates and the aqueous phase may contain a salting out agent such as lithium, calcium, zinc or ammonium chlorides or nitrates, or magnesium chloride.  According to examples (1) an oxide mixture of the yttrium group obtained from gadolinite was converted to nitrates and the mixture subjected to a multi-stage liquid extraction between an aqueous phase consisting of a saturated solution of lithium nitrate and an organic phase consisting of n-pentanone.  The extraction was operated with the aqueous phase stationary but divided into ninety-two stages whilst the organic phase was passed through the aqueous phase from the first stage to the last by passing it in at the bottom of each stage and collecting it at the top.  The rare earth nitrates were added to the first aqueous stage and yttrium nitrate was recovered from the final aqueous stages.  (5) A rare earth nitrate mixture containing lanthanum praseodymium, neodymium and samarium was extracted as in Example (1) with npentanone whereby the lanthanum was concentrated in stages 1 to 26, praseodymium in stages 38 to 44 and neodymium and samarium together with small amounts of lanthanum and praseodymium in the remaining stages.  Further examples relate to the treatment of nitrates of the cerium group with n-pentanone whereby neodymium is recovered in the final aqueous stage, the treatment of yttrium nitrates with a 1:1 mixture of n-pentanone and di-n-butyl ether, the aqueous phase containing either lithium or calcium nitrate, the treatment as in (1) but using as the organic phase methyl pentanone, noctanone, cyclohexanone or a mixture of furfural and cyclohexanone, the treatment of yttrium nitrates with an aqueous phase containing lithium nitrate and with a ethylhexyl aldehyde, benzoic aldehyde pentanal or a 1:2 mixture of furfural and cyclohexanone; the treatment of nitrates of cerium group metal with an aqueous solution containing magnesium chloride, and with pentanone.  The rare earths may be employed in the form of their nitrates or as salts or perchloric acid, alkyl phosphoric acid, alkyl sulphuric acid and organic acids such as lactic acid.