Treatment of Metal Ores

Abstract

A method of refining a metal (e.g. titanium), comprising the following steps: (a) providing (10) an oxide of the metal having a level of impurities of at least 1.0 wt %; (b) reacting (12) the oxide of the metal to form an oxycarbide by providing an electrode comprising the oxide of the metal including calcium oxide and iron oxide. and carbon, and electrolytically reducing the electrode in a molten calcium chloride electrolyte; (c) electrolysing (14) the oxycarbide in an electrolyte, with the oxycarbide configured as an anode; and (d) recovering (16) a refined form of the metal from a cathode in the electrolyte.

Claims

1. A method of refining a metal capable of forming an oxycarbide, comprising the following steps: (a) providing an oxide of the metal; (b) reacting the oxide of the metal to form the oxycarbide by: providing an electrode comprising the oxide of the metal and carbon; and electrolytically reducing the electrode in a molten calcium chloride electrolyte; (c) electrolyzin the oxycarbide in the molten calcium chloride electrolyte by reversing electrolytic cell polarity such that the oxycarbide is configured as an anode; and (d) recovering a refined form of the metal from a cathode in the molten calcium chloride electrolyte; wherein the oxide of the metal has a level of impurities of at least 1.0 wt %; and wherein the impurities are leached from the oxycarbide before step (c) using acid.

2. The method according to claim 1, in which the refined form of the metal is at least 99.5% pure by weight.

3. The method according to claim 1, in which the oxide of the metal is an ore or ore concentrate.

4. The method according to claim 1, in which the oxide of the metal comprises oxides of silicon, aluminum, iron, calcium, chromium and/or vanadium.

5. The method according to claim 1, in which the oxide of the metal includes at least 0.1 wt % calcium oxide and/or at least 0.1 wt % iron oxide.

6. The method according to claim 1, in which the level of the impurities in the oxide of the metal provided in step (a) is less than 20 wt %.

7-12. (canceled)

13. The method according to claim 1, in which a carbon anode is used in step (b).

14. The method according to claim 13, in which the carbon anode is replaced with an inert electrode in step (c).

15. (canceled)

16. The method according to claim 1, in which the metal includes titanium, scandium, chromium, manganese, yttrium, zirconium, niobium, molybdenum, lanthanum, cerium, neodymium, samarium, gadolinium, hafnium, tantalum, tungsten, bismuth and/or uranium.

17. The method according to claim 1, in which the metal includes titanium, scandium, yttrium, lanthanum, cerium, neodymium, samarium, gadolinium, and/or uranium.

18. The method according to claim 1, in which the metal is titanium.

19. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] An embodiment of the invention will now be described in detail, by way of example, and with reference to the accompanying drawings, in which:

[0035] FIG. 1 is a flow chart illustrating steps of a method for refining titanium from an ore comprising titanium dioxide;

[0036] FIG. 2 is a schematic diagram of an electrolytic cell for forming titanium oxycarbide (Ti.sub.2CO) used in one step of the method illustrated in FIG. 1;

[0037] FIG. 3 is a schematic diagram of an electrorefining cell used in another step of the method illustrated in FIG. 1; and

[0038] FIG. 4 is a schematic diagram of an alternative electrorefining cell to the one illustrated in FIG. 3.

SPECIFIC DESCRIPTION OF EMBODIMENT OF INVENTION

[0039] Electrorefining in molten salts is used commercially to produce high purity molten aluminium by dissolving the aluminium into a copper -aluminium alloy. This is made the anode and the aluminium being the most reactive element is ionised into the salt and deposited at the cathode with the impurities remaining in the anode. The ionisation potentials for the pure elements for a chloride melt relative to Na/Na.sup.+, at 1173 K, are [0040] Al=Al.sup.3++3e E?=+1.72 V [0041] Si=Si.sup.4++4e E?=+2.27 V [0042] Mn=Mn.sup.2++2e E?=+1.63 V [0043] Fe=Fe.sup.2++2e E?=+1.98 V In an alloy of these elements, manganese should ionise first followed by Al, Fe and Si.

[0044] The same principle can be applied to the refining of other metals but in this invention, the reactions are not the refining from liquid metals but the refining of metal from metal oxides. A typical composition of a titanium ore is given in Table 1 below:

TABLE-US-00002 Oxide Wt. % TiO.sub.2 96.5 SiO.sub.2 1.4 Al.sub.2O.sub.3 0.26 Fe.sub.2O.sub.3 0.55 MgO 0.07 CaO 0.66 Na.sub.2O 0.08 K.sub.2O 0.01 Cr.sub.2O.sub.3 0.31 V.sub.2O.sub.5 0.30 LOI 0.07

[0045] If this material is reacted with C it will form TiC.sub.XO.sub.y and other oxycarbides, but these dissolve in the titanium oxycarbide at very low concentrations so that when an anodic potential is applied only the titanium will ionise and plate out on the cathode.

[0046] Once in the electrolyte, the deposition potentials should be given by Table 2 below and the order of deposition chromium, iron, titanium magnesium and, finally, calcium.

TABLE-US-00003 Reaction Potential relative to Na+ + e? = Na (V) Cr.sup.2+ + 2e.sup.? = Cr 2.07 Mg.sup.2+ + 2e.sup.? = Mg 0.83 Ti.sup.2+ + 2e.sup.? = Ti 1.68 Fe.sup.2+ + 2e.sup.? = Fe 1.99 Ca.sup.2+ + 2e.sup.? = Ca ?0.18

[0047] These potentials will be influenced by the activities of the ions in the salt so that if the activity of the species is low, it will be more difficult to deposit the metal form that species.

[0048] The overall conclusion of these calculations is that it is very likely the calcium, being highly electropositive, will be retained by the electrolyte.

[0049] Surprisingly, it was found that by electrorefining the oxycarbide, made from an ore with the composition given in Table .sub.1, titanium with a very low impurity content of the other elements was deposited on the cathode.

EXAMPLE

[0050] A broad method of producing titanium from an ore (such as the ore whose composition is given in Table 1) is illustrated in FIG. 1. Having provided the ore at step 10, a titanium oxycarbide is formed at step 12. The titanium oxycarbide is electrolysed at step 14, and refined titanium metal recovered at the cathode at step 16.

[0051] The oxycarbide is prepared (step 12) by mixing an ore of the composition shown in Table 1, in powder form, with carbon powder in accordance with the stoichiometry given by the equation: 2TiO.sub.2+C+6e=Ti.sub.2CO+3O.sup.2-. The powders are pressed into pellets 2 mm diameter and 2 mm thickness using an uniaxial pressure of 2.65 tons cm.sup.?2.

[0052] FIG. 2 shows schematically an electrolytic cell for electrolytically reducing an electrode formed from the pressed powder pellets. The mixed TiO.sub.2 and C electrode is configured as the cathode and electrolysed in a molten calcium chloride (CaCl.sub.2)) electrolyte to form titanium oxycarbide. With a carbon anode, the following reactions occur:

2TiO.sub.2+C+6e.sup.-=Ti.sub.2CO+3O.sup.2-

2O.sup.2-+CCO.sub.2+4e.sup.-

[0053] At this stage, the only intention is to form the titanium oxycarbide: there is no intention to electrolytic refine the titanium ore. However, once the titanium oxycarbide has been formed, electrolytic refining may be carried in a number of ways, as explained below:

[0054] Option 1

[0055] FIG. 3 shows schematically an electrorefining cell. The titanium oxycarbide (Ti.sub.2CO) is configured as the anode and electrolysed in a molten salt electrolyte (step 14), such as eutectic NaClKCl or eutectic LiClNaClKCl, containing some TiCl.sub.2 and TiCl.sub.3. Metal deposited at the cathode during electrolysis (step 16) was collected.

[0056] Option 2

[0057] FIG. 4 shows an alternative electrorefining cell which is derived from the electrolytic cell of FIG. 2, and so retains molten calcium chloride as the electrolyte. The carbon anode has been replaced with an inert electrode, and the polarity has been reversed so that the newly formed titanium oxycarbide electrode is re-configured as the anode. During electrolysis, titanium from the titanium oxycarbide will be ionised, with the resultant titanium ions diffusing through the electrolyte to the inert electrode which is cathodic and where electrolytically refined titanium metal is deposited (e.g. by plating the inert electrode) for subsequent recovery (step 16). The reactions are: [0058] (i) at the anode, Ti.sub.2CO=.sub.2Ti.sup.2++CO(g)+4e.sup.-; and [0059] (ii) at the cathode, 2Ti.sup.2++4e.sup.-=2Ti