Note: Descriptions are shown in the official language in which they were submitted.
104S83~'
1 This application is a divisional application of
Canadian patent application serial number 201,300 filed on
May 30, 1974 entitled: Process for Extraction and Separation
of Metals Using Liquid Cation Exchangers.
It is known that liquid organic cation exchangers such
as fatty acids, naphthenic acids and other carboxylic acids,
and alkyl-phosphoric acids such as di(2-ethylhexyl)phosphoric
acid (DEHPA) can be used for the extraction and separation of
metal ions from aqueous solutions by complex formations between
the metal ions and the said organic components. When the organic
active extractants are dissolved in an organic soluent (diluent)
which is insoluble in the aqueous phase, a contacting between -
the organic phase and the aqueous phase causes the formation of
an organo-metallic complex batween the active organic extractant
and the metal ion in the aqueous phase. The said metal complex
is soluble in the organic phase, but not in the aqueous phase
and the metal is in this manner extracted into the organic phase. -
The formation o thé metal-complex takes place by
a cation exchanger, whereby an equivalent amount of protons
from the organic acid are released corresponding to the amount
of metal extracted from the a~ueous phase. This leads to a
corresponding decrease in pH in the aqueous phase. The formation
of the metal cationic complex will primarily be related to the
pH of the aqueous phase and will take place only above a certain
pH value. As a general rule, in the case of carboxylic acids,
it can be assumed that the lower limit for extraction of metal
ions is somewhat lower than the pH value whereby the respective
metals are precipitated as hydroxides.
This dependency on the pH allows the extraction to
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1 take place selectively, and the separation of the metals is
obtained by adjustment of the pH in the aqueous solution.
As regard to alkyl-phosphoric acids, these are generally
capable of extracting metal ions at lower pH values than the
carboxylic acids. Furthermore, special effects may occur such
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1 as inversion of the selectivity for copper and zinc on transition
from a carboxylic acid to alkyl-phosphoric acid as a cation
exchanger.
As a principle rule, however, the extraction of metal
ions with cation exchangers in their acid form causes an
equivalent amount of protons to be released and only a very
limited amount of metal ions can be extracted, therefore, before
the lower pH value is reached and the extraction ceases. This
can be counteracted by neutralizing the released protons by a
supply of alkali to the system. The pH is thus kept at a value
where the extraction of metal ions can continue.
In practice, however, this means that the use of the
above said cation exchangers for extraction of metal ions will in
many cases be prohibitive or will not permit economic advan~ages
in relation to a precipitation reaction, since the process
requires an equivalent addition of alkali, corresponding to the -
amount of metal extracted.
In accordance with the invention, a process is provided
which utilizes the advantages of the described liquid-liquid
extraction with cation exchangers without requiring the equivalent
addition of alkali which is normally considered prohibitive or
as a significant economic burden. This is achieved in that the
leaching of the metals from the solid metal-containing raw
materials takes place primarily with organic acid ~the above
said cation exchangers). As is known, the conventional technique
for extracting metal values by leaching is to use a mineral acid
such as for instance sulphuric acid which gives aqueous metal
salt solutions.
The inventive idea is based on a combination of leaching
the metal-containing raw materials with an organic acid (cation
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1~45832
1 exchanger) and a subsequent use of the metal cationic complex
formed thereby, in a liquid-liquid extraction process. In the
said liquid-liquid extraction process, the organic solution of
metal complexes is used to recover and separate metal ions from
an aqueous solution of metal salts. The aqueous solution of metal
ions normally originates from leaching the metal-containing raw
materials with a mineral acid such as for instance sulphuric
acid, whereby a number of metals can be dissolved.
To this end, in one of its aspects, the invention pro-
vides a process for the hydrometallurgic production of at
least one desired metal consisting of copper, nickel, cobalt or
zinc, from a metal-containing raw material which may contain
undesired iron, selected from the group consisting of oxide ores,
metal waste products and roasted sulphide ores, which comprises ;~
; leaching the raw material with aqueous mineral acid, thereby - -
forming an aqueous metal salt solution, extracting the metals
including iron from said aqueous solution by contacting said
solution with an organic liquid phase consisting of a cation
exchanger component selected from the group consisting of organic
carboxylic acids and alkyl phosphoric acids in solution in an
organic solvent, said organic liquid phase ~ontaining a complex
between at least one of said desired metals and the cation
exchanger component, said complex having been formed by contacting
said organic liquid phase with a desired metal-containing
material which is different from the starting raw material to be
leached, whereby the metals are exchanged between the organic
phase and the aqueous phase and any iron present is transferred
to the organic phase and forms a complex with the cation exchanger
component and the desired metal of said complex passes from the
organic phase to said aqueous solution, and then recovering desired
metals from said aqueous solution.
Further objects and advantages of the invention will
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1 appear from the following description taken together with the
accompanying drawings in which:
FIGURE 1 illustrates the dissolution and separation of
two metals by the combined leaching and liquid-liquid extraction
process using both an organic cation exchanger (KH) and a mineral
acid (HA) as leaching agents.
FIGURE 2 shows the dissolution of zinc calcine by the
organic phase, and subsequent transfer of zinc to the aqueous
phase and transfer of iron to the organic phase.
FIGURE 3 is a process diagram for recovery and separation
of copper, zinc and iron from mine water.
Reference is made to Figure 1, which illustrates the
principle of the process described. In order to simpllfy the des~
~ cription, it is assumed on the Figure that only two metals are
; dissolved by leaching of the metal-containing raw materials. There
is,however,in principle no limitation to the number of metals which
can be recovered and separated by the use of the present invention.
In the reaction between the solid metal-containing raw
materials and the liquid cation exchanger, preferably the most
basic metal (MeI) in the raw material will react with the cation
exchanger (KH) thus forming the metal cationic complex (K.MeI). By
the subsequent liquid-liquid extraction process the least basic
metal (MeII) will be extracted into the organic phase by exchange
with the metal MeI, which passes into the aqueous phase. The
aqueous phase is thus enriched in the metal MeI during the extrac-
tion process,MeII being exchanged at the same time to the organic
phase.
If, in addition to the metals MeI and MeII, the aqueous
phase also contains other metals, the metals may be extracted
separately, optionally in groups, by a suitable division of the
organic phase and adaption of the number of extraction stages
within the technical procedure of the extraction process.
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1~45832
1 If the aqueous phase is containing free mineral acid,
the said free acid can be neutralized to a suitable extent by
a corresponding increase in the amount of organic phase which is
brought into contact with the aqueous phase during the extraction
process. Protons in the aqueous phase will then be extracted by
an exchange with the bas~c metal from the organic phase.
It may also be pointed out that it is normally advantageous
to dissolve as much as possible of the metals during the primary
leaching of the solid material with the organic phase. Excess `
of metal complex in the organic phase can be stripped directly
with a mineral acid. The ideal system would thus be to obtain
quantitative leaching of the valuable metals by the organic phase,
whereafter the metals are separated by selective stripping from
the organic phase with a mineral acid such as for instance
sulphuric acid.
According to Figure 1, it is assumed, for example,
that the metals are deposited from the stripping solution in
their metallic form by electrolysis. A number of alternative
methods for preparing these aqueous metal salt solutions by
reduction and depositing processes are possible and have to be
evaluated in each single case. By carrying out the stripping
process with excess of a strong mineral acid, it is thus possible
` to achieve direct precipitation of metal salts by the stripping
process.
It may also be possible to precipitate metal salts
directly from the organic phase by contacting and stripping with
a gaseous phase suchas for instance hydrogen chloride, carbon
dioxide, and sulphur dioxide.
The invention thus relates to a process for extraction
and separation of metals from a solid metal-containing raw material
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1 and from an aqueous solution in the presence of or without free
mineral acid, using a liquid cation exchanger dissolved in a
suitable organic solvent, by the combination of leaching the
metal-containing raw material with the liquid cation exchanger
and a subsequent stripping process and/or a liquid-liquid ex-
traction process, the process being characterized in that the
liquid cation exchanger in the organic phase is contacted with
and reacts with the solid metal-containing raw material, whereby
one or more metal cationic complexes are formed which are con-
tacted with a mineral acid for stripping of the metals from themetal complexes, or the organic phase, which contains the metal
complexes, is used in a subsequent liquid-liquid extraction
process for recovery and separation of metal ions from an aqueous
solution of metals.
As will be clear from Figure 1, the invention leads
to a closed process procedure.with the possibility of quantitative
. recovery of the valuable metals in the metal-containing raw
materials, some of the raw materials which do not react with the
liquid cation exchanger being brought to a final leaching with
a mineral acid or another aqueous leaching liquid.
.In the following, it will be illustrated by examples
how the invention can be utilized within the hydro-metallurgic
production of zinc, when the metal-containing raw materials are
. . present in the form known as "calcine" produced by roasting
sulphide concentrates. In this case, the zinc oxide content of
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the calcine reacts with the organic acid during formation of a .
metal complex of zinc which is thereafter used for removing ferric ~ ~
ions from the acid zinc sulphate solution within the hot leaching ~ ~ -
stage of the process.
The general principle of the invention can, however, be
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1 utilized within any hydrometallurgic process where it is possible
to produce the organic metal complex by a reaction between a solid
metal-containing raw material and the active liquid organic cation
exchanger. In the existing hydrometallurgic processes, reference
can be made by way of example to refining and purification of
metals such as copper,nickel, cobalt and zinc from sulphide or
oxide ores. With sulphide ores, the raw material is most
frequently roasted ~eforehand to metal oxides ~calcine), which
is the most obvious starting material in the present invention.
If the metal-containing raw material is a metallic waste
product, such as for instance an alloy of various metals, or
a cementation product of metals such as obtained from the
purification step within the hydrometallurgical production of
zinc, an oxidizing treatment of this material will give a mixture
of metal oxides which can be extracted and separated by the
process according to the invention.
When the process according to the invention is utilized,
` for example, in the hydrometallurgic production of zinc, where,
as is known, zinc oxide in-the calcine is dissolved in sulphuric
acid and zinc deposited by electrolysis, the process can be used
for removal ofiron from the zinc sulphate solution without en-
tailing any use of alkali or other additives. This is further
elucidated in the following where, for example, it is assumed
that the liquid cation exchanger is a commercial carboxylic acid
such as for instance "Versatic 911*" (Shell), described herein-
below as "Versatic*",and is present as a solution in a suitable
organic solvent such as for instance "Shellsol TD*n.
Reference is made to Figure 2, which illustrates the
principle of the process described hereinbelow. On the Figure,
KH corresponds to "Versatic*" acid.
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1 "Versatic" in its acid form, is reactive to solid zinc
oxide ~calcine). By the reaction, a metal complex is formed
between zinc and "Versatic" (Zn-Versatic). By a subsequent
contacting between the zinc-containing organic phase and an iron-
containing aqueous zinc sulphate solution, an exchange between
zinc and iron takes place. The iron is thereby transferred to
the organic phase where it will be present as the metal complex
Fe-Versatic. By this exchange, an equivalent amount of zinc
passes from the organic phase into the aqueous zinc sulphate
solution. In this manner, the iron is removed quantitatively
from the zinc sulphate solution by contact between the two
immiscible phases in one or more stages depending on the technical
procedure of the liquid-liquid extraction process.
Subsequent to the extraction, iron may be stripped from
the organic phase by contacting with sulphuric acid or another
mineral acid in one or more stages. The liquid cation exchanger
("Versatic") will thereby be regenerated into its acid form and
will again be ready to be loaded with zinc on reaction with the
solid zinc oxide ~calcine). -
As will be clear from the above described process, -~
the raw material, in this case zinc oxide, serves as an alkali
in the process and any use of extra chemicals is unnecessary.
By the reaction between "Versatic" and calcine, zinc is dissolved
in the organic phase and will later be deposited as metal by
the electrolysis after it has been transferred to the aqueous
phase by the liquid-liquid extraction stage.
In Norwegian Patent No. 108.047, a process for separating
iron from metal sulphate solutions and a hydrometallurgic pro-
cess for production of zinc are described. Reference is made
to this patent in regard to the conventional process for hydro-
metallurgic production of zinc.
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1 In the above said patent, it is stated that the leaching
of calcine with sulphuric acid takes place in two stages, the
first stage being characterized as a neutral leachiny and the
second stage as an acid leaching.
In the first stage, calcine is added in excess, so
that the leaching is relatively mild. In this manner, the iron
is not dissolved, and a zinc sulphate solution free from iron is
obtained. The remaining residue of calcine will contain a
significant amount of zinc, however, bound to iron in the form of
zinc ferrites. In order to increase the total zinc yield, the
said residue is subjected to a strong leaching, heating with
excess of sulphuric acid, the so-called acid leaching. The
remaining zinc amount will thereby be dissolved, significant
amounts of iron will, however, accompany the solution.
In Norwegian Patent No. 108.047 it is illustrated how -
the said iron may be deposited as a basic sulphate in acid
solution by the presence of cations such as K , Na or NH4 . The
said deposition product is called jarosite and the said patent
gives the basis of the so-called jarOsite process within the
hydrometallurgic production of zinc. The process is used in
a number of zinc plants, and one of the advantages of the process
in view of previous processes resides in the faat that iron
is not the restricting factor for the leaching yield on acid
treatment of calcine.
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The process according to the invention which is based
on the combination of the reaction between the calcine with a
liquid organic cation exchanger and a subsequent liquid-liquid
extraction for removal of iron from the zinc sulphate solution
by means of the organo-metallic zinc complex formedl is parti- ~;
cularly suitable for the hydrometallurgic production of zinc. The
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1 starting point of the invention can be based on the leaching
method in two stages which forms the basis of the jarosite process.
The process according to the invention has obvious
advantages in view of the jarosite process, however, since it
is not necessary to add any chemicals such as ammonia to form a
deposition product. Further, in the present process, it is
possible to remove iron from the process cycle in alternative
forms. The stripping of the charged organic Fe-Versatic is a
very flexible stage, where it is possible, for example, to
produce a suitable starting material for further treatment of iron
to a high-valent iron powder or electrolyte iron. The iron can
be crystallized as iron sulphate directly within the stripping
stage where the concentration of iron sulphate can be maintained
close to the saturation concentration. If the crystallization
is more advantageous as bi-valent iron sulphate, the iron can
be reduced, for example, with sulphur dioxide prior to deposition.
There are no limits in principle to the amount of iron
which can be removed from the zinc sulphate solution. It is
also emphasized that excess of free sulphuric acid from the
strongly acid solution can be neutralized as a step in the liquid-
liquid extraction process. This means that a preceding partial
neutralization with calcine, which is conventional practice in
iron deposition in the jarosite process, becomes unnecessary.
The zinc yield, and the recovery of the remaining metals in the
ores, is limited only by the degree to which it is possible to
dissolve the metals by the leaching process.
A particular advantage of the process according to the
invention is that it has no adverse environmental effects.
It is also emphasized that removal and separation of
30 metals other than iron from the zinc sulphate solution can readily ~ -
be undertaken by the extraction process. It is particularly
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lV45832
1 mentioned that copper can be extracted in accordance with the
same principle described hereinabove for the extraction of iron.
A mixture of copper, zinc and iron may thus be separated in that
the organic solution with zinc as a metal complex is firstly used
for extraction of iron and thereafter for extraction of copper.
This will be further apparent from the fields of utilization
described hereinbelow for treatment of mine water.
If copper is the main component in the metal-containing
raw material, the copper will react with the organic cation
exchanger and can thus be used in the same manner as the organic
zinc complex for liquid-liquid extraction of iron from a metal
salt solutilon.
It is emphasized that the process according to the
invention is not restricted to hydrometallurgical production of
zinc and copper, but comprises all fields where it is possible
to use the described combination of leaching of a metal-
containing solid raw material with a liquid organic cation
exchanger and a subsequent liquid-liquid extraction for recovering
and separation of the metals from the aqueous solution occurring
by conventional leaching of the raw material with mineral acid.
The described combination of leaching and liquid-liquid
extraction can also be used in connection with separation and ~
recovery of metal ions from solutions which are not directly ~`
connected with the production of metals from a solid raw material.
As an example may be mentioned metal-containing waste water and
used pickling baths from chemical surface treatment within the
metal industry and other metal-containing wastes, for example,
from pyrite mines.
In these cases, the solid material, which is reactive
wlth the organic-acid (cation exchanger), must, however, be added
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1 to the process cycle in the form of, for example, lime. If the
metal solution is on a sulphate basis, gypsum will be deposited
equivalent to the metals recovered.
This process is suitable, for example, for recovery and
separation of metal values from mine water, where a typical
composition can be given, for example, as 0.5 - 1.0 g/l copper,
1 - 2 g/l zinc and 5 - 6 g/l iron.
Figure 3 illustrates by way of example a process
diagram for recovery and separation of copper, zinc and iron from
mine water, where the metals are present as sulphates. As an
extraction component the "Versatic" acid can be used, for example.
In a first stage of liquid-liquid extraction, iron will be
separated from the mixture and, in a next stage, copper can be
separated from zinc. The remaining zinc sulphate solution will
- have a zinc concentration which is equivalent to the original
total concentration of zinc, copper and iron and possible
free sulphuric acid. From this zinc sulphate solution, a
branch stream can be treated with lime. In this step the
organo-metallic zinc complex used in the liquid-liquid ex-
traction process will be formed.
If the present process is used for treatment of pickling
baths which contains relatively high concentrations of zinc and
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iron in a mixture, the previously mentioned Zn-Versatic complex
- can, for example, be used in a liquid-liquid extraction for
separation of iron from the pickling bath. After this treatment,
the bath will consist of a zinc salt solution from which zinc
can be deposited and recovered in a pure state.
The invention is further described in the following by
means of examples.
EXAMPLE
200 g of technical calcine produced by roasting of zinc ~
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1 sulphide concentrate was contacted with 1 litre of an organic
phase consisting o~ 30% "Versatic 911" dissolved in "Shellsol TD".
After agitation for 20 minutes at 50C, the solid phase and the
liquid phase were separated. The organic phase then had a zinc
concentration of 40 g/l.
In a stirring vessel, 100 ml of an aqueous sulphate
solution containing 120 g/l zinc and 18 g/l iron were contacted
with 317 ml of the above said 30% Versatic solution. 83 ml
of the zinc loaded Versatic solution containing 40 g/l zinc were
gradually added and after a contact period of 1 hour at 20C,
the aqueous and organic phases were separated.
Analysis of the two phases showed the following results:
Aqueous phase: 152.0 g/l Zn 0.3 g/l Fe
Organic phase: 0.4 g/l Zn 4.42 g/l Fe
EXAMPLE II -~
From an aqueous sulphate solution containing 120 g/l -
zinc and 18 g/l iron, the iron was extracted by continuous
operation inan apparatus consisting of three mixer-settlers in
series at a temperature of 50& . The organic phase was divided
into two streams, a pure 30% Versatic solution (Org.-l) and a
- zinc loaded 30% Versatic solution (Org.-2) containing 40 g/l zinc.
The organic solvent (diluent) was "Shellsol TD".
The aqueous phase and the Org.-l-solution was added to
the first and last stage, respectivel~, while the Org.-2-solution
was distributed over the three stages. Relative volumetric
proportions of the feed streams:
-~ Aqueous: Org.-l : Org.-2 = 1 : 2.2 : 0.8.
The resulting aqueous zinc sulphate solution contained
152 g/l Zn, and less than 0.1 g/l Fe.
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~J45832
1 EXAMPLE III
From a sulphate solution containing 120 g/l zinc and
18 g/l iron with 25 g/l free sulphuric acid, both the iron and
the free protons were extracted by continuous operation in a
corresponding manner to that of example II. Relative volumetric
proportions of the feed streams:
Aqueous: Org.-l : Org.-2 = 1 : 1.8 : 1.2.
The resulting aqueous zinc sulphate solution contained
169 g/l Zn and less than 0.1 g/l Fe.
EXAMPLE IV
100 g metal oxide was contacted with 1 litre of an organic
phase consisting of 30% cation exchanger dissolved in "Shellsol
TD". After stirring for 20 minutes at 50C, the solid phase and
the liquid phase were separated and the metal concentration
measured in the organic phase.
The results are given in the following table 1.
Table 1. Metal Concentration, g/l, in Organic
Phase after Contact with Metal Oxides.
_._
Cation Exchanger
Metal Oxide _
. Versatic 911 Di-ethyl-hexyl-phos-
phoric acid (DEHPA)
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CuO 1.56 0.53
Ni23 1.50 0.57
NiO 0.22 0.15
EXAMPLE V
A mixture of 75 g ZnO and 75 g CuO was contacted with
1 litre of organic phase consisting of 10% "Versatic 911" in
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1 "Shellsol TD". After stirring for 20 minutes at 50C, the
organic phase contained 27 g/l Zn and 0.02 g/1 Cu.
EXAMPLE VI
A mixture of 25 g Ni203 and 25 g CuO was contacted at
30C with the organic phase as in example V. The metal con-
centration in the organic phase after 20 minutes was 0.35 g/l Ni
and 0.03 g/l Cu.
EXAMPLE VII
To 1 litre zinc sulphate solution containing 15 g/l Zn
and equivalent amount of solid calcium hydroxide corresponding
to 9.2 g Ca was added. After stirring for 5 hours at 20C,
the sediment was filtered from the aqueous phase.
The filter cake which consisted of gypsum and deposited
zinc hydroxide was divided into two equa] sized parts and trans-
ferred to two stirring vessels. The two parts were contacted
with 400 ml of 30% "Versatic 911" and 30% DEHPA dissolved in
"Shellsol TD", respectively. After stirring for 30 minutes at
20C, the concentrations of zinc in the two organic solutions
were:
30% Versatic 911 : 15.1 g/l Zn
30% DEHPA : 14.9 g/l Zn.
Although the disclosure describes and illustrates
a preferred embodiment of the invention, it is to be understood
the invention is not restricted to this particular embodiment.
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