US 5,787,332 AGranted

Process for recovering tantalum and/or niobium compounds from composites containing a variety of metal compounds

AssigneeFansteel Inc.

InventorsWilliam D. Black, David R. Tierney, Henrietta Notzl-Loiselle

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Abstract

A process for treating composite materials comprising metals and having significant radioactivity for separation into concentrated individual products is provided. The process of the invention recovers valuable metals and semi-metal elements including rare earth, transition metal, radioactive elements, and compounds and composites thereof as commercially viable products while isolating the radioactive components. They key components in the composite material which are desired to be recovered are tantalum, niobium, and scandium due to their high commercial values and significant quantities. The process further includes the capability to recover uranium, thorium, rare earth, and zirconium products. Generally, the process consists of an initial sulfate roast followed by a series of hydrometallurgical unit operations designed to separate and purify the desired components into commercially usable products, such as tantalum and/or niobium in the form of metal oxides, M.sub.2 O.sub.5 ; uranium in the form of yellowcake; thorium oxalate; zirconium oxide; and rare earth sulfates.

Method for recovering constituents from a composite material which comprises tantalum oxides and niobium oxides, and other metals (M) at least a portion of which are present as metal fluoride compounds (MF.sub.y), said method comprising the steps of:

a. reacting said metal fluoride (MF.sub.y) compounds of said composite material with sulfuric acid (H.sub.2 SO.sub.4) to form metal sulfate (M(SO.sub.4).sub.y/2) compounds from said metal fluoride compounds and to form hydrogen fluoride (HF) according to the reaction:
MF.sub.y +(Y/2)H.sub.2 SO.sub.4 .fwdarw.M(SO.sub.4).sub.Y/2 +YHF(1.ltoreq.y.ltoreq.6);
b. washing the composite material with water to remove at least a portion of said metal sulfate (M(SO.sub.4).sub.y/2) compounds from said composite material, whereby said removed portion is leached into said water and forms a leachate solution,
c. solubilizing, in a first acid solution comprising hydrochloric acid (HCl) or nitric acid (HNO.sub.3 ), any metal sulfate compounds remaining in said composite material after step (b), thereby removing at least a portion of said remaining metal sulfate compounds in said first solution;
d. reacting any double sulfate compounds (M.sub.x (SO.sub.4).sub.y .multidot.NaSO.sub.4 .multidot.2H.sub.2 O) among said metal sulfate compounds in said material with caustic soda (NaOH) in a caustic solution to form metal hydroxide compounds (XM(OH)2y) according to:
M.sub.x (SO.sub.4).sub.y .multidot.Na.sub.2 SO.sub.4 .multidot.2H.sub.2 O+(2Y)NaOH.fwdarw.XM(OH).sub.2y +(Y+1)Na.sub.2 SO.sub.4
where 1<y<3, and removing said caustic solution;
e. reacting said metal hydroxide compounds (M(OH).sub.2y) with a second acid solution comprising HCl or HNO.sub.3 to form metal chloride compounds or metal nitrate compounds according to:
XM(OH).sub.2y +2YHCl.fwdarw.MCl.sub.26 +2YH.sub.2 O;
or
XM(OH).sub.2y +2YHNO.sub.3 .fwdarw.M(NO.sub.3).sub.2y +2YH.sub.2 O
where 1.ltoreq.x.ltoreq.2, 1.ltoreq.y.ltoreq.3;
f. removing said metal chloride or metal nitrate compounds from the composite material of step (e) to thereby provide a residue of said composite material where said residue comprises tantalum oxide and niobium oxide in concentrated amounts relative to initial amounts of said oxides in said composite material prior to step (a);
and
g. collecting said residue composite materials.

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Abstract

Claims22