METHODE POUR SEPARER DES METAUX DU MINERAI

METHOD FOR SEPARATION OF METALS FROM ORE

Abrégé français

Méthode pour séparer une valeur métallique, autre que le titane, d'une solution aqueuse, La méthode consiste à extraire des valeurs métalliques de la solution aqueuse au moyen d'une phase organique et d'assujettir la phase organique ainsi obtenue à la chaleur pour distiller la phase organique et la valeur métallique l'une de l'autre. L'écart des points d'ébullition entre la valeur métallique et la phase organique est suffisant pour permettre une distillation fractionnelle d'au moins 50 degrés celcius. Le trichlorure de gallium, le pentafluoride de tantale et le pentafluoride de niobium sont des exemples de valeurs métalliques . Les éthers couronnes, les oxydes phosphiniques et les sels d'ammonium tertiaires et quaternaires sont des exemples de solvant organique.

Abrégé anglais

A method for the separation of a metal value, other than titanium, from aqueous solution. The method comprises extracting the metal values from the aqueous solution with an organic phase and subjecting the organic phase thus obtained to heat to distill one of the organic phase and the metal value from the other thereof. The difference in boiling points between the metal value and the organic phase is sufficient to permit fractional distillation at least 50°C. Examples of metal values are gallium trichloride, tantallum pentafluoride and niobium pentafluoride. Examples of the organic solvent are crown ethers, phosphine oxides, tertiary and quaternary ammonium salts.

Revendications

1. A method for the separation of a metal value, other than
titanium, from aqueous solution comprising the steps of:
a) extracting the metal values from the aqueous solution with an
organic phase, said organic phase being selected from crown ethers,
phosphine acids, esters and oxides, tertiary and quaternary ammonium salts;
and
b) subjecting the organic solution thus obtained to heat to distil one
of the organic phase and the metal value from the other thereof, the
difference
in boiling points between the metal value and the organic phase permitting
fractional distillation.

2. The method of Claim 1 in which the organic phase is the
distillate.

3. The method of Claim 1 in which the metal value is the distillate.
4. The method of any one of Claims 1 to 3 in which the metal value
is selected from gallium trichloride, tantalum pentafluoride and niobium
pentafluoride.
5. The method of any one of Claims 1 to 4 in which the difference
in boiling points is at least 50°C.

Description

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TITLE
METHOD FOR SEPARATION OF METALS FROM ORE

The present invention relates to a method for the separation of metals,
other than titanium, from an ore or concentrate. In particular embodiments of
the invention, the method relates to the recovery of metal values from
aqueous solutions of those metal values involving extraction of the metal
values with an organic phase and subsequent distillation of the resultant
organic solution in which either the metal value or the organic phase is the
distillate.
In the processing of ores or concentrates, many processes involve the
leaching of ore or concentrate, or of a product derived therefrom, with an
acidic solution, frequently hydrochloric or sulphuric acid. Liquid/solid
separation techniques may then be used to separate tails fractions.
In some instances, aqueous solutions containing metal values are
subjected to extractions using organic phases. In such extractions, metal
values are extracted from the aqueous solution into the organic phase. The
metal values are then recovered from the organic phase by stripping the
metal values from solution, with the metal values being obtained in aqueous
solution. The latter aqueous solution contains the metal values in a
substantially purer form of the metal value than in the aqueous solution prior
to extraction. Such a use of an organic phase is in the purification of the
metal value in the aqueous solution obtained from the liquid/solid separation
step.
An improved method for the separation of metal values from ore using
an organic phase has now been found.
Accordingly, one aspect of the present invention provides a method for
the separation of a metal value, other than titanium, from aqueous solution
comprising the steps of:
a) extracting the metal values from the aqueous solution with an


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organic phase; and
b) subjecting the organic solution thus obtained to heat to distill
one of the organic phase and the metal value from the other thereof, the
difference in boiling points between the metal value and the organic phase
permitting fractional distillation.
In one preferred embodiment, the organic phase is the distillate and in
an alternate embodiment, the metal value is the distillate.
In further embodiments, the metal value is selected from gallium
trichloride, tantallum pentafluoride and niobium pentafluoride.
In another embodiment, the organic phase is selected from crown
ethers, phosphine acids, esters and oxides, tertiary and quaternary
ammonium salts. Techniques for treating of ore, optionally to form
concentrate and/or for beneficiation of the ore are known. In some instances,
it is possible to treat the ore or concentrate with concentrated hydrochloric
or
sulphuric acid solution to effect a leaching of metal values from the ore or
concentrate.
The present invention is directed to the step of recovery of metal
values from the leaching solution. The leaching solution may be a mixture of
aqueous acid containing metal values, and other soluble material, and solid
materials, particularly residues of the concentrate and/or slag from which
metal values have been leached. Examples of the acid include hydrochloric
and sulphuric acid, but other acids may be used. Leaching may be
conducted at ambient temperatures or elevated temperatures. A liquid/solid
separation step is then conducted, to separate a leachate solution from
solids.
The leachate so obtained is extracted, according to the present
invention, with an organic phase. The metal values in the leachate may be in
the form of a halide, especially a chloride if hydrochloric acid is used in
the
leaching step. Alternatively, the metal value may be in the form of an oxide
or
sulphate. The organic phase is selected such that the metal value is soluble
in the solvent. Moreover, the organic phase is selected such that the boiling
point of the organic phase differs sufficiently from that of the metal value
to


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permit fractional distillation. In embodiments, the boiling point of the
organic
phase is at least 50 C, and especially at least 75 C, different from the
boiling
point of the metal value. In addition to the above, the organic phase must be
immiscible with the aqueous solution, such that it forms a second layer so
that
separation may be effected.
The metal value is extracted from the aqueous solution into the organic
phase, to effect removal of the metal value from the aqueous solution. Such
extraction may be carried out in a continuous operation or in a batch
operation.
The organic phase containing the metal value is separated from the
aqueous solution and from any solid matter, and is then subjected to
distillation. In the distillation, the organic phase containing the metal
value is
heated to effect the separation of the organic phase and the metal value. As
noted above, the organic phase must be selected so that there is a
differential
in boiling point from the metal value sufficient to permit fractional
distillation
e.g. of at least 50 C and especially at least 75 C although it is understood
that smaller differentials may be possible, depending on the organic phase
and metal value, in order to effect separation of metal value and organic
phase to an acceptable extent. In addition, the organic phase must be
immiscible with water and stable during use.
Separation may be effected by volatilization of the metal value or
distillation of the organic phase, depending on the boiling pint of the metal
value and stability at elevated temperature. The organic phase is selected to
obtain the most effective separation. In addition, the organic phase should be
selected so that it has a flash point that is acceptable under the operating
conditions, especially a flash point above the temperature used in the
separation.
The organic phase may be recycled back to the extraction step, and be
reused.
The metal value may be used as such or subjected to further steps e.g.
to form metal or another derivative of the metal.
Examples of metal values are gallium trichloride (GaCls, b.p. 201.3 C),


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tantallum pentafluoride (TaF5, b.p. 229.5 C) and niobium pentafluoride (NbF5,
b.p. 236 C).
The separation of titanium values using an organic phase is disclosed
in the copending patent application of V.I. Lakshmanan et al. filed
concurrently herewith.
The method of the present invention provides a separation of metal
values that are capable of being dissolved in an organic phase and separated
using distillation procedures. Such metal values must be stable at the
temperatures that are used. The method provides metal values with
improved purity and/or such that related steps in an overall process,
including
recovery and recycle of materials, may be simplified and be more cost
effective. In particular, the volumes of liquid and solids that must be
handled
in the overall separation process may be reduced, and associated hardware
may be reduced in size. Such improvements may be of significant economic
benefit.