A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics
A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics
MONAZITEa mixture of sulfates but the usual process is with alkali [3]. The concentrate is finel ground anddigested with an excess of caustic soda at≈150°C for several hours.(Ln,Th)Po 4 + NaOH => Na 3 PO 4 + Ln(OH) 3 + Th(OH) 4The phosphate portion produces a soluble sodium tripolyphosphate while the lanthanides, alongwith thorium, form insoluble hydroxides (hydrated oxides) that can be recovered.The next step is hydrochloric acid attack, at ≈70 °C and pH 3-4, on the solids portion. Thethorium remains insoluble and a crude thorium hydroxide can be filtered off. (The small amountsof trace contaminants that do carry through into solution, such as uranium and lead as well as somethorium, are removed by coprecipitation with barium sulphate in a deactivation step.) The chloridesolution containing the rare earths, lanthanides, is concentrated by steam heat and can be cast intosolid form.The rare-earth-chloride (RECL 3 ), like monaziteconcentrate, is a material traded commercially not onlyfor further separation processes but also for theproduction of ferro-alloys such as mischmetal.Treatment of the RECL 3 solution with sodium carbonatewill precipitate a RE carbonate that can beconverted to other mixed-lanthanide derivatives, e.g.fluorides, nitrates and, by calcination, a rare-earthoxide. (Rare earth chlorides, whether derived fromBastnasite or from Monazite, have very similarcompositions and can most times be usedinterchangeably in later processes.)Rare Earth Chloridea.k.a. Lanthanide ChlorideLnCl3,6H2OTypical Analysistotal as Ln Oxides ≈46 %CeO2 ≈22-25%La2O3 ≈11 -16%Nd2O3 ≈5-9%Pr6O11 ≈2-3%The thermally stable (m.pt. >2000°C) monazitephosphate structure[4] accommodates the light Ln's,Chloride ≈31 %La to ≈Gd, with an irregular nine-coordinate Ln atom. Within the structure, the Ln(III) and P(V)can be substituted by Th(IV) and Si(IV) somewhat by analogy with Xenotime, YPO 4 , and zircon,ZrSiO 4 . that are isostructural.[3] Processing of Monazite at the Rare Earths Division, Udyogamandal, N.S.Narayananet al., Mater.Sci.Forum, 1988, 30, 45[4] The Structure of Cerium Orthophosphate, a Synthetic Analogue of Monazite,G.W.Beall et al., J.Inorg.Nucl. Chem., 1981, 43, 1019
NEODYMIUMNeodymium is the third most abundant lanthanideand is recovered from the minerals bastnasite andmonazite. This element is of current commercial interestbecause of the development of the Nd-Fe-B alloys aspermanent magnet materials.[1] In addition Nd-basedlasers are becoming more widely used.In all readily prepared compounds Neodyrniurn istrivalent and the Nd 3+ ion shows typical Ln 3+ chemicalproperties, see Lanthanum for a summary. The table onthe next page lists data for some of the commonlyencountered salts and more details can be found underthe appropriate anion heading, e.g. nitrate, oxide, etc.Neodymium salts usually appear pale purple, aconsequence of the spectral absorption of the Nd 3+ ion.(The oxide-in contrast to the salts-is sky-blue, with thesubtle shift from the normal Nd-salt color being causedby the stronger ligand field influences in the oxide.) Ndhas a strong absorption band centred at 580 nm, others at≈740 and ≈8OO nm and several more bands of lesserstrength.[2]NdelementAtomic Number 60Atomic Weight 144.24Electron[Xe]4f 4 6s 2configurationValency 3Ionic radius for 8- 111 pmcoordinationMagnetic moment 3.62 µBmetalCrystal Structure dhcpMelting Point 1021 °CBoiling Point 3074 °CDensity7.01 g/cm3Metallic Radius 182 pmThe 580 nm band is in the yellow and very close tothe position of the eyes' maximum sensitivity. In consequence, the perceived color ofNd-containing glass - being here caused by both reflection and subtraction phenomena - dependson the spectrum of the illuminating light; this creates so-called "dichroism". The Nd-ion colorsartistic glassware and is added, for example, to the glass used in protective goggles worn duringwelding in order to block light of the 580 nm wavelength. Nd- doped glass can be used as acontrast-enhancing filter, clarifying the eye's discrimination between reds and greens, on CRTdisplays.[1] New Permanent Magnet Materials, K.H.J.Buschow, Materials Sc. Rep., 1986, 1, 1: Neodymium-Iron-BoronPermanent Magnets prepared by Rapid Solidification, J.J.Croat, J.Mater.Eng., 1988, 10, 7 : PermanentMagnets, J.F.Herbst, Am.Sci., 1993, 81(3), 252[2] Analysis of Rare Earth Mixtures by a Recording Spectrophotometer, D.C.Stewart and D.Kato, Anal.Chem.,1958, 30(2), 16410
- Page 2 and 3: ALANTHANIDELANTHOLOGYPart II, M - Z
- Page 6 and 7: Compounds of the perovskite, ABO 3
- Page 8 and 9: METALSThe lanthanides, when prepare
- Page 10: METALSMetallo-thermic oxide-reducti
- Page 13: MONAZITEMonazite, a light-lanthanid
- Page 18 and 19: [2] Preparation, Phase Equilibria,
- Page 20 and 21: NOMENCLATURE58 - 71; the term is in
- Page 22 and 23: OXALATESAddition of oxalic acid, or
- Page 24 and 25: OXIDESCalcination in air for the th
- Page 26 and 27: OXIDESFurthermore oxides with Ln IV
- Page 28 and 29: OXYCHLORIDESThermal decomposition o
- Page 30 and 31: OXYSULFIDESAll the elements of the
- Page 32 and 33: PEROVSKITESA very wide range of mat
- Page 34 and 35: PHOSPHATESThe LnPO 4 compounds can
- Page 36 and 37: PRASEODYMIUMtransport of Pr happens
- Page 38 and 39: RESOURCESFor significant resources
- Page 40 and 41: RESOURCESSignificant new resources
- Page 42 and 43: SAMARIUMSamarium metal is made dire
- Page 44 and 45: SILICATESWithin the binary Ln 2 O 3
- Page 46 and 47: SOLVENT EXTRACTIONSome text books s
- Page 48 and 49: SULFATESLanthanide sulfates can be
- Page 50 and 51: SULFIDESThe thermochernistry of CeS
- Page 52 and 53: THULIUMThulium, the rarest of the "
- Page 54 and 55: TITANATES, TITANIUM DIOXIDELanthani
- Page 56 and 57: YTTERBIUMIn broad chemical behavior
- Page 58 and 59: YTTRIUMCompoundIdealFormulaFormula
- Page 60 and 61: YTTRIUM OXIDEThe very stable oxide,
- Page 62 and 63: YTTRIUM OXIDEThe widespread introdu
MONAZITEa mixture of sulfates but the usual process is with alkali [3]. The concentrate is finel ground anddigested with an excess of caustic soda at≈150°C for several hours.(Ln,Th)Po 4 + NaOH => Na 3 PO 4 + Ln(OH) 3 + Th(OH) 4The phosphate portion produces a soluble sodium tripolyphosphate while the lanthanides, alongwith thorium, form insoluble hydroxides (hydrated oxides) that can be recovered.The next step is hydrochloric acid attack, at ≈70 °C and pH 3-4, on the solids portion. Thethorium remains insoluble and a crude thorium hydroxide can be filtered off. (The small amountsof trace contaminants that do carry through into solution, such as uranium and lead as well as somethorium, are removed by coprecipitation with barium sulphate in a deactivation step.) The chloridesolution containing the rare earths, lanthanides, is concentrated by steam heat and can be cast intosolid form.The rare-earth-chloride (RECL 3 ), like monaziteconcentrate, is a material traded commercially not onlyfor further separation processes but also for theproduction of ferro-alloys such as mischmetal.Treatment of the RECL 3 solution with sodium carbonatewill precipitate a RE carbonate that can beconverted to other mixed-lanthanide derivatives, e.g.fluorides, nitrates and, by calcination, a rare-earthoxide. (Rare earth chlorides, whether derived fromBastnasite or from Monazite, have very similarcompositions and can most times be usedinterchangeably in later processes.)Rare Earth Chloridea.k.a. Lanthanide ChlorideLnCl3,6H2OTypical Analysistotal as Ln Oxides ≈46 %CeO2 ≈22-25%La2O3 ≈11 -16%Nd2O3 ≈5-9%Pr6O11 ≈2-3%The thermally stable (m.pt. >2000°C) monazitephosphate structure[4] accommodates the light Ln's,Chloride ≈31 %La to ≈Gd, with an irregular nine-coordinate Ln atom. Within the structure, the Ln(III) and P(V)can be substituted by Th(IV) and Si(IV) somewhat by analogy with Xenotime, YPO 4 , and zircon,ZrSiO 4 . that are isostructural.[3] Processing of Monazite at the Rare Earths Division, Udyogamandal, N.S.Narayananet al., Mater.Sci.Forum, 1988, 30, 45[4] The Structure of Cerium Orthophosphate, a Synthetic Analogue of Monazite,G.W.Beall et al., J.Inorg.Nucl. Chem., 1981, 43, 1019
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