Note: Descriptions are shown in the official language in which they were submitted.
2 Dx.31682A
This application is a division of Serial No. 395,390
filed February 2, 1982.
This invention relates to a process for the
extraction of metal values from aqueou3 ~olu~ion~ of metal
salts, and in particular to a proces~ for the extraction
o~ metal values from aqueous solutions in the presence
of halide anions.
The use of solvent extraction techniques for the
hydrometallurgical recovery of metal values from metal
ores has been practised commercially for a number of
years~ For example copper may be recovered from oxide
ores or from ore tailings by treating the crushed ore with
sulphuric acid to give an aqueous solution of copper
fiulphate which is subsequently contacted with a solution
in a water-im~iscible organic solvent of a met~l extractant
whereby the copper values are selectively extracted
Lnto the organic solvent phaseO
The application of solvent extraction techniques
to aqueous solutions containing halide ions however has
hitherto presented numerous technical problems.
Of particular importance in this connection is the
development of hydrometallur~ical routes (as an alternative
to smelting) for the extraction of metal values from
sulphur-containing ores such as chalcopyrite. S~lch ores
may be leached for example using ferric chloride or cupric
chloride solutions; but the solvent extraction of the
result~nt leach solutio~ presents formidable
difIiculties.
The present in~ention provides a proce6s for the
extraction of metal values ~rom aqueous solution~
containing halide ion~ by the use of metal extractants
who~e several properties meet the stringent requirements
imposed on the extractant by the system.
Dx 31682A
According to the present invention there is provided a
process for extracting metal values from aqueous solutions
of metal salts containing halide or pseudo halide anion
which comprises contacting the aqueous solution with a
solution in a water-immiscible organic solvent of a
substituted pyridine of formula:
(~C ~
wherein X is the group -ORl or -NR2R3, Rl being a hydrocarbyl
group containing from 5 to 36 carbon atoms and R2 and R3 being
hydrogen or a hydrocarbyl group, R2 and R3 together containing
from 5 to 36 carbon atoms, and n is 1, 2 or 3.
When n is 2 or 3, the substituent -X in the respective
groups COX may be the same ordifferent. For example, when
n is 2, ~he two groups COX may be -CORl and -CORl' respectively
where Rl and Rl' are both hydrocarbyl groups containing from
5 to 36 carbon atoms. Similarly, when n is 2, the two groups
-COX may be -CORl and -CONR2R3 respectively.
According to a further aspect of the present invention
there is provided a process for extracting metal values from
aqueous solutions of me-tal salts containing halide or pseudo-
halide anion which comprises contacting the aqueous solution
with a solution in a water-immiscible organic solvent of a
3~ or 4-substituted pyridine of formula:
~)
~3;~6'7
Dx 31682A
C - X O
C - X
~ ~ or ~ ~
wherein X is the group -ORl or -NR2R3, Rl being a hydrocarbyl
group containing from 5 to 36 carbon atoms and R2 and R3
being hydrogen or a hydrocarbyl group, R2 and R3 together
S containing from 5 to 20 carbon atoms.
According to a further aspect of the present invention
there is provided novel metal extractants. Thus there is
provided a 3- or 4-substituted pyridine of formula:
O O
C - X 11 - X
10 ~wherein X is the group -ORl or -NR2R3, Rl being an alkyl
group containing from 9 to 24 carbon atoms and having the
formula:
/ R4
- CH - CH
~5
wherein R4 and R5 are alkyl groups, and R4 contains two fewer
15 carbon atoms than R5, and R2 and R3 together containing a
~393~
Dx 31682A
total of from 15 to 36 carbon atoms, provided -that when
R2 is hydrogen, R3 is a branched chain alkyl group.
There is also provided a substituted pyridine of
formula:
~ n
~'N~
wherein X is the group -ORl or -NR2R3, and n is 2 or 3, the
respective groups Rl being alkyl groups containing a total
of from 16 to 36 carbon atoms, and the respective groups
R2 and R3 being alkyl groups wherein the total number of
alkyl carbon atoms contained in all the respective groups
R2 and R3 is from 20 to 70~
The pyridine ring may carry substituents in addi-tion
to the group(s) COX. Examples of suitable substituents are
halo~en ~roups, alkyl groups, aryl groups, alkoxy groups,
aryloxy groups, aralkyl groups, cyano groups and nitro groups.
The pyridine ring may also carry a carboxylic acid group,
ancl the invention includes for example a half ester of a
pyridine dicarboxylic acid.
Substitution in the pyridine ring may for example result
2Q from the method of synthesis. For example bis ester of
4-phenylpyridine-3,5-dicarboxylic acid may be prepared from
methyl propiolate, aromatic aldehydes and ammonium acetate
in acetic acid followed by oxidation to the pyridine
derivative and ester exchange (Chennat and Eisner, J~C~So
Perkin I, 1975).
When n is 1, examples of compounds which may be used in
the process of the invention include esters or amides of
nicotinic acids, isonicotinic acids and picolinic acids.
~32~i7
Dx 31682A
When n is 2, examples of compounds which may be used in the
process of the present invention include bis esters or amides
of pyridine~2,4~dicarboxylic acid, o~ pyridine-2,5-dicarboxylic
acid, and of pyridi.ne-3~5-dicarboxylic acid. ~Ihen n is 3,
examples of compounds which may be used in the process of
the present invention include tris esters or amides of
pyridine-2,4,6-tricarboxylic acid. Mixtures of such compounds
may be used, for example a mixture of bis esters or amides of
isomeric pyridine-dicarboxylic acids.
The substituted pyridines of the present invention
wherein X is the group -ORl may be prepared by conventional
means, for example by the reaction of a pyridine carboxylic
acid, for example isonicotinic acids, nicotinic acids or
picolinic acids respectively with the appropriate alcohol to
form the desired esters. Alternatively the lower esters, for
example methyl or ethyl esters may be subjected to ester
exchange reactions with higher alcohols, or the acid chlorides
may be reacted with the appropriate alcohol or phenol.
Dicarboxylic acid esters of pyridine may conveniently be
prepared from lutidines, for example by oxidation and
esterification.
Rl may for example be an alkyl group, for example an
octyl, nonyl, decyl, dodecyl, tridecyl, pentadecyl, hexadecyl
or octadecyl group or substituted alkyl group, for example
a group containing one or more propylene oxide residues formed
by reacting propylene oxide with an alcohol before
esterification to give the substituted pyridine, Rl may be a
cyclo alkyl group such as cyclohexyl; Rl may be an aralkyl
group such as benzyl; or Rl may be an aryl, alkylaryl or
alkoxyaryl group for example p-nonylphenyl or p-dodecylphenyl.
When n is 1 and there are no other substituents in the
pyridine ring, R1 is preferably a branched chain alkyl group
containing fxom 9 to 24 carbon atoms.
Rl may be an isomeric mixture of groups con-taining the
same number of carbon atoms or a rnixture of groups containing
, ~j
~3%~i'7
Dx 31682A
different numbers of carbon atoms (which may themselves be
an isomeric mixture), for example a mixture of different
alkyl groups. If Rl is a mixture of groups containing
different numbers of carbon atorns, the average number of
carbon atoms is preferably from 9 to 24.
Highly branched groups Rl may usefully be obtained
by the reaction of the pyridine carboxylic acid with alcohols
prepared by the Guerbet and Aldol condensations. Such
alcohols are characterised by branching at the position beta
~ to the hydroxyl group, and have the general formula:
/ R4
HO - CH2 ~ CH
R5
In general R4 contains 2 fewer carbon atoms than R5, and
groups Rl derived from these alcohols include for example,
C6Hl3
~ CH2 ~ CH
C8H17
/ C8E117
2 CH
Cl oH
/ 7 15
- CH - CH
CgHl g
,
~3~
Dx 31682A
R4 and R5 may be straight chain or branched chain alkyl
groups and may be isomeric mixtures of alkyl groups. A
mixture of highly branched alcohols may be oh~ained by
Guerbet or Aldol condensations of mixtures of alcohols and
aldehydes respectively.
Excellent solubility is conferred upon the
compounds of formula I where the alcohol is the product of
the aldol dimerisation of commercial nonaldehyde. In this
alcohol the group Rl is believed to consist essentially of
a mixture of geometrical isomers of a radical of the formula:
I
fH3 fH3 CH2 IH3 IH3
CH3 - C - CH2 -CH - 2 CH2 - CH - CH2 - f - CH
CH3 CH3
When n is 2, the respective groups Rl (Rl and Rl')
may be any of those groups Rl listed previously. Rl and
Rl' are conveniently the same and are preferably straight
chain or branched chain alkyl groups. When n is 2, we have
found that to achieve the desired solubility of the metal
complex in preferred solvents, Rl and Rl' preferably together
contain a total of from 16 to 36 carbon atoms. The groups
may contain a mixture of isomers, for example a mixture of
nonyl isomers derived from isononanol obtained by the hydro-
formylation of a mixture of octenes, a mixture of decyl
isomers obtained from isodecanol r or a mixture of tridecyl
isomers obtained from tridecanol.
The substituted pyridines of the previous invention
wherein X is the group -NR2R3 may be prepared by conventional
means, for example by reaction of pyridine carboxylic acids
and their lower esters with higher primary or secondary amines.
Alternatively the acid chloride of the pyridine carboxylic
acid may be reacted with the appropriate amine.
~32~;~
Dx 31682A
~ he amide group -NR2R3 may be primary (R2 is
hydrogen) or secondary. R2 and R3, which may be the same
or different may be groups of the type indicated above for
R1. R2 and R3 taken together contain from 5 to 36 carbon
atoms. Thus R2 may be for example a lower alkyl group, ~or
example a methyl group, provided R3 is correspondingly
larger. R2 and R3 taken together are preferably alkyl groups
containing a total of 15 to 36 carbon atoms. For secondary
amides sufficient solubility in preferred organic solvents
may generally be achieved if R2 and R3 are straight chain or
branched chain alky] groups. However for primary amides
(R2 is hydrogen), R3 is pre~erably a branched chain alkyl
group. When n is 2, and the groups R2 and R3 are all alkyl
groups, the total number of alkyl carbcnatoms preferably does
not exceed 70, for example the total number of alkyl carbon
atoms is preferably from 20 to 70.
The process of the present invention mav be applied
to the extraction from aqueous solutions containin~ halide or
pseudochalide ion of any metal capable of forming a stable
halide- or pseudochalide-containing complex with the pyridine
derivative in the water-immiscible organic solvent. Examples
of such metals include copper, cobalt, cadmium and zinc. The
process of the present invention is especially applicable to
the solvent extraction of copper from aqueous solu-tions
obtained by the halide or pseudo halide leaching of sulphur-
containing copper ores, for example from solutions obtained
by the leaching of ores such as chalcopyrite with aqueous
ferric chloride or cupric chloride solutions.
The leaching of ores such as complex sulphide ores,
for example chalcopyrite with for example aqueous ferric
chloride solution containing hydrochloric acid gives rise to
leach solutions containing cuprous and cupric ions, ferrous
and ferric ions and excess chloride anion. The ratio of
cuprous to cupric ion depends on the leach condi-tions
selected. The sulphur content of the ore may be precipitated
, ~
Dx 31682A
as elemental sulphur. Whilst the scope of the present
invention is not to be taken as being limited to the treatment
of any particular halide-containing aqueous solution, -t:~pical
solutions obtained by the leaching o~ chalcopyrite with
acidified ferric chloride may contain between 10 and 60
grams per litre of copper, between 50 and 150 grams per litre
of iron, may typically be between O.lM and lM in hydrochloric
acid and may be between about ~M and 8M in total chloride
ion. Certain leach systems may give total chloride ion
contents as high as lOM or 12M. All leach solu-tions
encoun-tered in practice will also contain varying quantities
of the many other metals present in the ore body. Certain
leach solutions may contain high levels of specific metals,
for example zinc, in addition to copper.
It will be appreciated that the process oE the
present invention may be incorporated into a wide variety of
different methods for the overall recovery of metals from
their ores or from other metal-bearing sources. Details of
these methods will vary depending on the metal concerned
and the nature and composition of the leach solution.
Whilst the process of the present invention is not limiied
to any single overall method for the recovery of metals, the
stringent conditions imposed on the pyridine extractant are
best illustrated if the solvent extraction process is seen
as a step in an integrated process for the recovery of the
metal from the ore. For example an integrated process which
is especially suitable for leach solutions containing high
levels of cupric ion comprises the fol~owing steps:
1. Leaching of the ore with aqueous ferric or cupric
chloride solutions, and removing the elemental sulphur
produced;
2. Contacting the leach solution from step 1 (in which
the ferric ion i9 at least partially reduced to ferrous ion)
with a solution in a water-immiscible solvent of -the
extractant, whereby the copper is trans-ferred into the
;~
~3~:67
11
Dx 31682A
organic phase in the form of a chloride-con-taining complex
with the extractant;
3. Separating the organic phase containing the complex
of copper with the extractant from the aqueous phase
containing the ferric/ferrous chloride;
4. Contacting the organic phase from step 3 with an
aqueous strip solution which is water, or which contains a
reduced concentration of chloride ion, whereby the chloride-
containing complex of copper with the extractant is unstable
and copper transfers into the aqueous strip solution;
5. Separating the organic phase containing the stripped
extractant from the aqueous strip solution containing the
copper chloride; and
6. Electrolysing the strip solution from step 5 to
recover copper. The electrolysis step is suitably arranged
such that oxidation of ferrous ion with transfer of chloride
ion takes place in the anode compartment, such that the
solution leaving the cathode compartment is denuded in both
copper and chloride ion. Alternatively chlorine gas may be
evolved at the anode and optionally used as oxidant to
regenerate the leach solution.
In order to preser~e the overall stoichiometry
of the sequence of reactions, it may be necessary to provide
additional oxidation of ferrous to ferric ion, and to remove
the iron entering the system continuously from the chalcopyrite
(CuFeS2), for example in the form of iron oxide such as
goethite.
For a fully integrated process it is highly desirable
that the solutions be re-circulated between the various stages.
Thus aqueous strip solution used in step 4 is preferably
derived from the electrolysis step 6 and is preferably the
solution leaviny the cathode compartment denuded in both
copper and chloride ion. Similarly the organic phase
containing the stripped extractant which is separated in
step 5 is preferably re-circulated to the extraction stage 2.
~3~
12
Dx 316~2A
The ferric chloride solution derived from the electrolysis
step 6 may be returned for fur-ther leaching of the ore.
Considering first the extraction stage 2 and the
strip stage ~, the extraction of for example cupric ivn
by the extractant may be represented by an equation such
as the following:
2Lorg ~ Cu aq ~ 2Cl aq -~ (L2CuCl2)ory
This equation is a grossly oversimplified representation of
a very complex process and is not to be taken as in any way
limiting the scope of the present invention, but it serves
to illustrate the formation of a neutral organic phase
complex of copper and the extractant (L) which is believed
to predominate in the process of the present invention.
Other equations may be used to represent the extraction and
stripping of cuprous ion or of other metals by the extractant.
~ he above equation assumes that the extractant
acts as a monodentate ligand, and whilst this is believed to
be generally true, esters and amides of 2-carboxypyridines
do at least have the potential of acting as bidentate ligands.
Vnder certain conditions other species, for example oligomeric
complexes such as L2(CuC12)n may be formed. The formation
of oligomeric species is generally undesirable since the
efficiency of copper extraction is reduced and in addition
the oligomeric complexes tend to have a low solubility in
organic solvents. We have found that the tendency to the
formation of oligomeric species is especially low with
esters and amides of 2-carboxypyridines.
The equation also illustrates the reversible na-ture
of the extraction, whereby the cornplex of copper and the
extractant in the organic phase can be stripped on contact
with water or with an aqueous solution containing a reduced
chloride or a reduced copper content such that copper is
332~7
13
Dx 31682A
transferred to the aqueous phase and the free ex-tractant is
at least partially regenerated in the organic phase.
Most efficient stripping will be obtained usiny
water itself as the stripping medium, and the proce~s of the
present invention may be combined with a water stripping
stage. However, i-t will be noted that in a fully integrated
process, it is preferred that the loaded extractant be
stripped with the solution derived fro~ the electrolysis
stage and denuded in copper and chloride ion. In the
extreme case, the aqueous phase may be entering the
electrolytic cell containing about 40 or 50 grams per litre
copper and may leave it still containing as much as 30 grams
per litre copper or more. The requirement that the extractant
will be able to efficiently extract copper from the leach
solution, whilst at the same time be stripped by a solution
containing relatively high levels of copper is exacting.
Preferred extractants for use in the process of the present
invention are capable of being stripped by an aqueous
solution containing relatively high levels of copper, for
example from 20 to 35 grams per litre of copper.
Since the leach solution contains high levels of
iron, it isclearly important that the extractant should have
good selectivity for copper over iron. The extractants of
the present invention have this property. Of particular
importance in an integrated s~stem, where the copper is
recovered by electrolysis of the pregnant aqueous strip
solution, is selectivity for copper over silver and other
minor extractable constituents of the ore~ The reason for
this is that whilst metals such as zinc and cadmium are more
electronegative than copper and are not electrodeposited with
it, silver is both co-deposited with copper and furthermore
adversely affects the physical properties of the copper so
that an expensive electrorefining stage is required. Preferred
extractants of the present invention have excellent selectivity
for copper over silver under appropriate operating conditionsO
.~
~93~
1~
Dx 316~2A
A yet further property which is of importance for
an extractant in ~e process of the present invention is the
absence of significan-t protonation by the acidic leach liquGr.
Such protonation may be represented by an equation such
as:
L + H + Cl ~- ILH Cl )
org aq aq ~-- org
where L is the extractant. Such protonation of the ligand
not only carrles hydrochloric acid into the organic phase,
building up unnecessary chloride concentration on the strip
side, but is also believed to be associated with less of
selectivity for copper over silver and other trace components
such as antimony and arsenic. Again the preferred extractants
of the present invention have excellent resistance to
protonation even in contact with relatively acidic leach
solutions.
As illustrated by the ~xamples, the extractants of
the present invention provide a range of properties so that
the optimum extractant may be selected for a given leach
solution. In particular, a "strong" extractant, for example,
isooctadecyl nicotinate,is capable of extracting high levels
of copper from a leach solution containing relatively low
chloride ion content (for example about 3.7M) but tends to
undergo undesirable protonation and acid transfer at higher
acid/chloride ion concentrations (for example H~, O.lM; Cl ,
9.8M). On the other hand, a "weak" extractant such as a
diester of pyridine-2~5-dicarboxylic acid is found to transfer
only low level.s of acid, even ~rom solutions concentrated in
chloride ion and acid (for exa~lple lO.7M and lM respectively).
Furthermore, the lower inherent abiiity of the ex~ractant -to
transfer copper into the organic phase is offset by the
irnproved transfer of copper at these higher chloride ion
concentrations.
, ,,
~3;2~7
Dx 31682A
sis esters of pyridine-3,5-dicarboxylic acids, for
example/ the bis-nonyl ester, are weak extractants which
furthermore show high selectivity for copper over zinc, and
provide a potential for recovery of ~inc in leach solutions
containing high levels of both copper and zinc.
Examples of suitable water-immiscible organic
solvents are aliphatic, aromatic and alicyclic hydrocarbons,
chlorinated hydrocarbons such as perchloroethylene, trichloro-
ethane and trichloroethylene. Mixtures of solvents may be
used. Especially preferred in conventional hydrometallurgical
practice are mixed hydrocarbon solvents such as high boiling,
high flash point, petroleum fractions (for example kerosene)
with varying aromatic content. In ~eneral, hydrocarbon
solvents having a high aromatic conten-t, for example ARO~ASOL H
which consists essentially of a mixture of trimethylbenzenes
and is commercially available from Imperial Chemical Industries
PLC (AROMASOL is a registered trade mark), provide a higher
solubility for the extractant and its copper complex, whilst
kerosene having a relatively low aromatic content, for
example ESCAID lQO which is a petroleum distillate comprising
20~ aromatics, 56.6% paraffins and 23.4% naphthenes
con~ercially available from ESSO (ESC~ID is a registered trade
mark) may in certain cases improve the hydrometallurgical
performance of the extractant. Factors influencing the
solubility of the extractant and its copper complex are
complicated, but in general extractants having highly branched
substituents and/or an isomeric mixture of substituents have
comparatively high solubility.
We have found that isonicotinic acid derivatives and
30 their copper complexes, for example (2-hexyldecyl)isonicotinate,
have surprisingly high solubility in both high and low
aromatic content hydrocarbon solvents.
The concentration of the extractant in the water-
immiscible organic solvent may be chosen to sui-t the particular
35 leach solution to be treated. Typical values of extractant
concentration in ~he organic phase are between about ~1 to
2 Molar, and an especially convenient range is from 0.2 to
0.~ Molar in the organic solvent.
2~
16
Dx 31682A
The extraction stage and the strip stage of the
solvent extraction process may conveniently take place at
ambient tempe~ature. However, it is possible to lmprove
net copper transfer from the leach solution to the strip
solution if the extraction s-tage is operated at ambient
temperature, whilst the strip stage is operated at elevated
temperature, for example up to 50C. We have also found that
the undesirable formation and build-up of oligomeric
complexes of the extractant and copper may be alleviated if
the strip stage is operated at elevated temperatures, for
example up to 50C.
The invention is illustrated by the following
Examples in which ali parts and percentages are by weight
unless otherwise stated.
Ex~mple 1
(2-(n)Hexyldecyl)nicotinate was prepared as follows:-
A stirred mixture of nicotinic acid (61.5 parts),dimethylformamide (0.63 parts) and xylene (174 parts) was
heated to 80 below a condenser set for reflux. Thionyl
chloride (65.5 parts) was then added during 1-2 hours, the
temperature of the reaction mixture being allowed to rise ~o
90-95 during the addition. The mixture was then stirred at
90-95 for 3 hours. The condenser was then set for
distillation and the temperature was raised until excess
thionyl chloride had distilled and xylene had begun to distil.
The mixture was then allowed to cool to 80-85 and 2-(n~-
hexyldecanol (112 parts) was added during 30 minutes. The
mixture was stirred at 80-85 for 2 hours and was then cooled
to room temperature, and extracted with a solution of sodium
hydroxide (40 parts) in water (165 parts). The xylene
solution was washed alkali free with more water, and the
xylene was distilled under reduced pressure leaving
(2-hexyldecyl~nicotinate [147 parts] as a brown oil. The
purity was estimated at 95% by titration of a sample with
N/lO perchloric acid in acetic acid medium. The compound was
distilled, b.p. 176-]84 at 0.4 mm pressure, yielding 109
,~;, j~,
~32~
17
Dx 31682A
parts of straw-coloured liquid which was 98-99~ pure.
The ability of (2-(n)hexyldecyl)nicotinate to
extract copper from aqueous solution containing chloride ion
was investigated.
An aqueous solution (A) was made up which was O.lM
in cupric chloride (6.35 gpl copper) t and O.lM in hydrochloric
acid, and which contained in addition 250 g/litre of calciurn
chloride dihyclrate. This solution was then agitated for 15
minutes with an equal volume of a solution (s) which was a
0.2M solution of (2-hexyldecyl)nicotinate in AROMASOL H. The
layers were allowed to separate and settle, and were
separately analysed for copper content. I'he percentage of the
copper initially present in A which had passed into B, w~s
44.5%. The resultant loaded organic solution B was then
stripped with an aqueous solution (C) which was 0.472M in
cupric chloridel i.e. one which contained 30 gpl of copper.
It was found that copper passed from the organic to the
aqueous solution. The percentage of the copper originally
present in ~ which had been transferred to solution C was
25.5%. The transfer of hydrochloric acid from solution A
to solution ~ was negligible.
Extraction of copper by the same extractant from a
more strongly acidic solution was also examined. The same
solutions and procedure as before were used, except that
solution A was l.OM rather than O.lM in hydrochloric acid.
The percentage of copper extracted into the organic solution
(B) and the percentage which finally passed into the aqueous
solution of cupric chloride (C) were 47.8% and 30.6%
respectively. The amount of hydrochloric acid which passed
from solution A to solution B under these extremely acidic
conditions was measured. Expressed as a percentage of that
which would be transferred if every molecule of the ligand
combined with one molecule of hydrochloric acid, the acid
transfer was only 1.9~.
The above results are summarised in Table 1.
~1
. "
~3~
18
Dx 31682A
Example 2
Tridecyl nicotinate was prepared using the method
of Example 1 from commercial tridecanol (an isome~ic mixture)
and nicotinic acid. The procluct had a boiling poin-t of 136
to 140C under 0.05 mm pressure and an estimated purity of
100% based on a molecular weight of 305.5.
The ester was evaluated as an extractant for copper
from aqueous solution containing chloride ion using the me-thod
of Example 1.
The results are presented in Table 1.
Example 3
N,N-di-(n)- octylnicotinamide was prepared using
the method of Example 1 from nicotinic acid and di-(n)-
octylamine. The product had a boiling point of 1~0 to 183C
at 0.15 mm pressure and an estimated purity of 95.5%.
The amide was evaluated as an extractant for copper
from aqueous solution containing chloride ion using the
method oE Example 1.
The results are presented in Table 1.
It will be noted that this compound is a stronger
extractant than those shown inthe previous Examples, and would
be more suitably employed for the extraction and subsequent
recovery of copper from an aqueous solution of lower
concentration of chloride ion. It would also be preferable
to strip the extractant with a strip solution which was lower
in copper and/or in chloride ion than solution C.
Example 4
(2-(_)-hexyldecyl)isonicotinate was prepared using
the method of Example 1 from isonicotinic acid and 2-hexyl-
30 decanol. The product had a boiling point of 180 to 190C at
0.75 mm pressure and an estimated puri-ty of 97.5%.
The ester was evaluated as an extractant for copper
from aqueous solution containing chloride ion using the
method of Example 1.
I'he results are presented in Table 1.
~3~7
19
Dx 316~2A
~::C
o ~
~n h ~ al
X h o
Q~ ~ ~
_ _ ~
U ~O 1 ~
O
q~ _
~ !~ ~o 4
o ~
e
_ __ __ h
1~>
t.) ~ ~ cO h
~¦ h--~ ~ O ll~ O u~ 1~\ ~1
0 4~ h O _ _ _ 0
O ~ ~ ~ ~ t~ O
~ ~ la
. 60
_ _ ~1 ~
~ 0
h E E ~ ~ o
'~J~
,.~ .
321~7
Dx 31682A
Example_5
A solvent extraction circuit was assembled consisting
of small scale mixer settler units. The circult comprised
3 stages of extraction and 2 stages of stripping and purnping
was arranged such that over both the e~trac-tion and stripping
parts of the circuit the organic and aqueous solu-tions flowed
counter current-wise~
The aqueous feed solution had the following
composition of metals:
Copper (Cu ) 16.0 g per litre
Iron (Fe ] 40.4 g per litre
Silver (Ag ) 18.9 mg per litre
In addition, the solution contained 150 g per litre of calcium
chloride added as the dihydrate CaC12.2H20 and contained 3.6 g
per litre of hydrochloric acid giving a total chloride ion
concentration of 4.23 moles per litre.
The strip solu-tion consisted of an aqueous
solution containing 28.9 gpl copper as cupric chloride with
no added acid.
The solvent phase comprised a 19.2% by weight
solution (0.553 moles per litre) of the extractant of
~xample 1 dissolved in~ROMASOL H.
The pumps and agitators in the circuit were started
and the flow rates adjusted to give an organic flow of 33.3
25 ml/min and aqueous flows of 13.3 ml/min (2.5 to 1 organic to
aqueous phase ratio).
After the circuit had been running successfully for
four working days at an average temperature of 15C, samples
taken from the aqueous raffinate; from the extraction circuit;
and of the pregnant strip solution were analysed.
The results obtained are sun~arised in Table 2.
.....
~32~7
21
Dx 31682A
Table 2
__ Fe Ag
gpl gpl rng/l
_ ... , . (~pl~)
Aqueous feed 16.G 40.4 13.9
Raffinate 2.49 3g.8 18.4
Strip solution 28.9 0.24 0
Pregnant strip s~luti~n 44.5 0.3 0.6
Example 6
_
(2-(n)-Octyldodecyl)nicotinate was prepared from
nicotinic acid and 2-(n~octyldodecanol using the general
method of Example 1 with the following minor changes. The
temperature after thionyl chloride addition was maintained
at 80C for 2 hours, and after the esterification reaction,
the solution was diluted with petroleum ether (60-80),
washed with water to remove acidity and the solven-ts removed
by distillation. The product had a boiling range of 190-200C
at 0.05 mm mercury pressure and an estimated purity of 87.9%.
The ability oE (2-(n)octyldodecyl)nicotinate to
extract copper from aqueous solution containing chloride ion
was investigated.
An aqueous solution (A) was made up which was O.lM
in cupric chloride ~6.35 g/l copper), O.lM in hydrochloric
acid and contained 250 g/l of calcium chloride dihydrate,
providing a total chloride ion concentration of 3.7M. This
solution was shaken for 1 minute with an equal volume of a
solution (B) which was a 0.2M solution of (2-(n)-octyldodecyl)-
nicotinate in ESCAID 100. The layers were allowed to
separate~ the aqueous layer was analysed for copper and the
solvent layer for acid transferred with the copper. The
3~
Dx 31682A
percentage of copper initially presen-t in A which had passed
into B was 52%. There was no de-tectable transfer of hydro-
chloric acid into B.
These results are summarised in Table 3.
Example 7
Iso-hexadecyl ni.cotinate was prepared from nicotinic
acid and a commercial material, iso-hexadecyl alcohol, obtained
from Farbwerke ~oechst AG. The general method of Example 1
was used except that the temperature after thionyl chloride
addition was maintained at 80C for 2 hours, and after the
esterification reaction the solution was cooled and washed
with 0.5M sodium hydroxide, 0.5M hydrochloric acid and water.
The solution was treated with activated carbon (2.5% on the
expected weight of product) at 50C for 1 hour, filtered and
the solvent removed under reduced pressure. The light brown
oil had an estimated purity of 93.4% and was distilled
(boiling range 141-146C at 0.03 mm mercury pressure) to
provide a product of 99.8% estimated purity.
The ester was evaluated as an extractant for copper
from aqueous solution containing chloride ion using the
method of Example 6~
To evaluate the efficiency of the extractant for
use with leach solutions containing higher levels of total
chloride ion, the general test method of Example 6 was
repeated using a solution (A) which contained cupric chloride
(O.lM), hydrochloric acid (O.lM) and 700 g/l calcium chloride
dihydrate giving a total chloride ion concentration of 9.8M.
The results are displayed in Table 3, and indicate
that the extractant is more suitable for use with leach
solutions having relatively low total chloride ion concentra-
tions (3.7M), since relatLvely high acid transfer levels occur
at high total chloride ion concentrations (9.~M)
Example 8
Isooctadecyl nicotinate was prepared using the
method of Example 7 from nicotinic acid and a commercial
product, isooctadecyl alcohol, obtained from Farbwerke
~ioechs-t ~G. The product had an estimated purity 94.5%.
~932~
Dx 31682A
The i.sooctadecyl alcohol starting material was
analysed by capiliary Gas Chromatography and gave traces
showing four peaks each of which was approximately the same
size. The commercial isooctadecyl alcohol is believed
mainly to comprise different geome-tric isomers of
2,2,4,8,10,]0-hexame-thyl-5-methylolundecane.
The ester was evaluated as an extractant for copper
from aqueous solution containing chloride ion, using the
method of Example 7.
The results are displayed in Table 3 and indicate
that the extractant is more suitable for use with leach
solutions having relatively low total chloride ion
concentrations (3.7M), since relatively high acid transfer
levels occur at high total chloride ion concentrations (9.8M).
Example 9
, .. _
l2-~n)Hexyldecyl)picolinate was prepared from
picolinic acid and 2-(n)hexyldecyl alcohol by the general
method of Example 1 with the following differences. The
temperature after thionyl chloride addition was maintained
at 80C for 2 hours and after the esterification reaction,
the solution was diluted with petroleum ether 60-80C, washed
with lM hydrochloric acid and with brine (10% NaCl). The
solvents were removed by evaporation and the dark coloured
oil distilled (boiling range 176-178C at 0.07 mm mercury
pressure) to give a colourless oil of estimated purity 97.5%.
The ester was evaluated as an extractant for copper
from aqueous solutions containing chloride ions by the
general method of Examples 6 and 7, except that AROMASOL H
was used as solvent. The solution A contained the higher
levels of chloride ion (9.8M) indicated in Example 7 and
Table 3. Table 3 shows that the extractant is comparatively
well suited for operation using leach solutions containing
higher levels of total chloride ion since only 9% transfer of
hydrochloric acid took place a~ a total chloride ion
concentration of 9.8M.
~.~r
.~
~3;~
24
Dx 3168
ple 10
Isooctadecyl picolinate was prepared using the
method of Example 7 from picolinic acid and isooc-tadecyl
alcohol, the commercial material obtained from Farbwerke
Hoechst AG and described in Example 8. The light bro~n,
oily product of the reaction had an estimated purity of
93.5%.
The ester was evaluated as an ex-tractant for copper
from aqueous solutions containing chloride ion using the
method of Example 7, except that AROMASOL H was used as
solvent.
The results are displayed in Table 3, and show
that whilst a relatively low extraction of copper takes
place from 3 7M total chloride ion solution, good extraction
of copper with relatively low acid transfer takes place from
9.8M total chloride ion solution.
Example ll
-
The bis isodecyl ester of pyridine~3,5-dicarboxylic
acid was prepared by the method of Example 1 from pyridine-3,5-
dicarboxylic acid and commercial isodecanol (obtained fromICI Petrochemicals Division) using modified amounts of
reactants as required by the stoichiometry. Toluene was used
as reaction solvent in place of xylene and the temperature
was maintained at 80-82C for 4 hours after the thionyl
chloride addition. Following the esterification reaction, the
solution was cooled, washed with dilute sodium hydroxide
solution, lM hydrochloric acid, 0.5M hydrochloric acid and
water~ The solution was treated with activated carbon (8%
on the expected weight of product), the solvent evaporated
at reduced pressure and the residue distilled (boiling range
200-210C at 0.08 mm mercury pressure~ to give a product
having estimated purity of 97.5%.
This bis-ester was evaluated as an extractan-t for
copper from aqueous solutions containiny chloride ion by the
method of Examples 6 and 7.
3~:~7
Dx 31632A
To evaluate the efficiency of the extrac-tallt for
use with leach solutions containing both high levels of total
chloride ion and high acid levels, the general test method
of Examples 6 and 7 was repeated usincJ a solution A which
contained cupric chloride (O.lM), hydrochloric acid (l.OM)
and calcium chloride dihydrate (700 g/l), giving a total
chloride ion concentration of lOo 7M.
The r~sults are displayed in Table 3, and show that
whilst a relatively low extraction of copper takes place
from 3.7M total chloride ion solution, excel~ent extraction
of copper takes place with no acid transfer from solutions
containing a total chloride ion concentration of ~.8M, and
low acid transfer levels are achieved even when the total
chloride ion concentration is 10.7M.
Example 12
The bis nonyl ester of pyridine-2,4-dicarboxylic
acid was prepared using the method of Example 1 from pyridine-2,
4-dicarboxylic acid and commercial nonanol (obtained from
ICI Petrochemicals Division and containing predominantly
3,5,5-trimethylhexanol), with modified amounts of reactants
as required by the stoichiometry. After the thionyl chloride
addition, the temperature was maintained at 84-85C for 2 hours
whilst a~ter the esterification reaction the product was
isolated as described in Example 7. The boiling range of the
product was 200-210C at 0.2 mm mercury pressure and the
estimated purity was 100%.
The bis-ester was evaluated as an extractant for
copper from aqueous solutions containing chloride by the method
of Examples 6 and 11, except that AROMASOL H was used as
solvent.
The results are shown in Table 3.
Example 13
The bis-isodecyl ester of pyridine 2,5-dicarhoxylic
acid was prepared using the method of Example 1 from pyridine-
2,5-dicarboxylic acid and commercial isodecanol, obtained
,.::,.:
~326~
26
Dx 316~2A
from ICI Petrochemicals Division, with modified amounts of
reactants as required by the stoichiometry. Toluene was used
as solvent for the reaction, in place of xylene, and after
the thionyl chloride addition the temperature was maintained
at 77-83C for 1~ hours. After the esteri~ication xeaction
the product was isolated as described in Example 7, and had
a boiling range of 219 221C at 0.08 mm mercury pressure,
and estimated purity of 95.5%.
The bis-ester was evaluated as an extrac-tant for
copper from solutions containing chloride by the method of
Examples 7 and 11.
The resul-ts are displayed in Table 3.
N,N-Di-(n~-octyl picolinamide was prepared using
the method of Example 1 from picolinic acid and di-(n)-
octylamine. A~ter the addition of thionyl chloride, the
temperature was maintained at 79-80~C for 5 hours and then
raised to distil excess thionyl chloride and a little xylene.
The acid chloride suspension was cooled to 48C and the
molten amine was added at 48-74C over lO minutes. The
reaction was continued at 90C for ~ hours and the dark
brown solution was cooled and washed with water to remove
acidity. The solution was treated with activated carbon
(10% on the expected weight of product), filtered, the
solvent evaporated and the dar~ brown oil distilled. The
product had a boiling range of 175-180C at 0.15 mm mercury
pressure and was dark coloured. It was purified by dissolving
in toluene, treating with activated carbon (lO~ on expected
weight of product) and extracting with 2M sodium hydroxide
and water~ The toluene was removed by evaporation under
reduced pressure to give a mid-brown coloured oil of estimated
purity 91~.
The amide ~as evaluated as an extractant for copper
from solutions containing chloride ion as in ~xample 6 and
7, except that AROMASOL H was used as solvent.
The results are displayed in Table 3.
Unable to recognize this page.
932~7
28
Dx.31682 A
A 0.5 molar solution of the extractant of Example 1
in Aromasol H (20 ml) was shaken for 1 minute with an equal
volume of a solution containing 37.6 ~l zinc, 3.65 ~l ~Cl
and 65 ~l calcium (all as chlorides) ha~ing a total chloride
ion concentration of 4.5 molar.
Analysis of the resulting aqueous phase showed that
it contained 2801 ~l zinc, indicating a zinc transfer of
2~.~q.
~
The solvent extraction circuit described in Example 5
was used to eYaluate the extractant of Example 1. The
feed was:
Copper (Cu2+) 25 ~l
Iron ~Fe2 ) 75 ~l
Silver (Ag~) 0.028 ~l
Lead (pb2 ) 1.5 ~l
Arsenic (As3 ) 0.2 g/l
Antimony tsb3+) O.10 ~l
Merc~r~ ) o.005 8~l
With the e~ception of ~ilver, which wa8 added a~
silver nitrate to ~acilitate dissolution, the metals were
in the for~ o~ their chlorides. In additionq the solution
contained 1.8 ~l of hydroge~ chloride, giving a total
c~loride ion concentration of 3.5 moles per litre~
The strip solution consisted of an aqueou~ solution
containiag 29 ~l copper as cupric chloride, adjusted to
p~ 1~0 with hydrochloric acid.
2~
29
Dx.~1682 A
The sol~ent phase eomprised 175 ~ 1 (0.5M) o~
the extractant of Example 1 dissolYed in AROMASOL H.
The operati~g conditions were a6 described
i~ ~xample 5, except that ~he aqueous feed to the fir~t
~trip mixer-~ettlor wa~ heated, and the 8tripped organic
phase returned to the ~xtraction ~ixer-fiettlers was cooled.
~s a result~ the fir6t fitrip 6tage operated at a~ a~erage
temperature o~ 45C, whil~t the second 6trip stage operated
at an ~er~ge te~perature o~ 34C~ ~he extraction 8tage8
operated at 280G.
The ~ircuit was operated for 53.5 honr6 wit~ steady
trans~er o~ copper from the aqueous ~eed solution to the
~trip 801ution throughout the period of operatio~ as
indicated by analysi6 of solutions pASSlng through the
circuit at the ti~es listed below:
Time ~
(hourJ) R~fi~tes ~ ~ r~ S~ln.
12 8 12 45
4~ 10 9 49
45 9 10 4
5~-5 8 10 41
~ _____~ _
During t~e period o operation, analysis for the
minor metals pre~ent i~ the f~ed 6ave the followi~g
results ( ~ l):
~ Pb2~ As3~ Sb3 ~
Strip 601~tion 0.001 00015 0.~040.010 0.0002
Preg~ant ~trip 0.001 000~0 o~too8 0.012 0.0002
solution
B~ way o~ co~tparifiontt the circuit was operated under
identical conditions,t except that no heatL~g of the strip
-t~. " j
",
~32~7
Dx.31682
circuit was U6ed ~ and Rll mi%er-6ettlers operated at
ambie~t tempe~ature (22C). No preci.pitate ~as ob~erved
but a gradual build-up of an oligomeric copper comple~
~pecies was i~ferred from copper loadings on the e~tr~ctant
gre~t0r than that expected for the species L2CuCl2~ where L
5 repres~ts the extractant. Tbe circuit wa~ oporated ~or
30 hours, and during this period, the concentration of
copper in both the raf~inate and the ~tripped organic
phase steadily increa6ed a~ indicated below:
q'ime (hour~) ~finate (CuZ _ ~ ) Stripped or~auic (~u
10.5 11~4
13.4 13.3
33 15.2 15.0
Example 17
The nicotinir acid e6ter of 2,2,4,8,10~10-
he~amethyl-5-methylolundecane (the latter being deriqable
fro~ the self conden~ation of two ~ol~sules o~
~OC~2C ~C~ - C~2C(~3)~ vi~ the Guerbet reaction)
c~3
wa6 prepared U8illg the method o~ E~ample 1~ Tbe product
bad a boilirlg point of 145 to. 150C at Ool mm pressure and
an e6timated purity o~ 90~a~.
qhe ester was evPluated as an extractant for
copper from aqueous solution con~aining chloride ion using
the method o~ E~a~ple 1.
The results are as ~o}low~:
~3~
31
Dx . 316 o2A
%
Transfer of copper ~rom 0.1M ~Cl to B42~5
Tran6fer of copper fro~ 0.1M ~Cl to C2~.6
Transfer o~ copper from 100M ~Cl to B48.o
Tran~f~r o~ copper from 1~0M ~Cl to C~0.2
Acid co-extracted from 1.0M ~Cl to B 2.6
Th~ acid co-extracted rrom 0~1M ~Cl to B was negligible.
t~ a~
The effect of different ester groups on the
solubility of a ligand-copperII chloride complex in
10 concentr~ted ~olution in a non-polar solvent was examined
as follows: Pyridine 3,5-dicarboxylic acid bis esters
were prepared by esterifying pyridine 3,5-dicarboxylic acid
with a series of different alcohols according to the
procedure of Example 11 (see Table 4). Each ester in turn
was made up as a 0.5M solutio~ in ESCAID 100 and loaded
with copperII chloride (to approximately 75~ of the theoretical
amount according to the stoichio~etry of L2CUCl~ where L
is the bis ester) by shaking with twice its ~olume of an
aqueous 60lution which was 0.1M in ~Cl, 0.4M in CuC12 aud
which in addition contained 250 g/l of calcium chloride
dihydrate. Any separation of the metal ligand complex
from the organic solution was noted (Test 1). If no
separation occurred, the organic solution was loaded to
approximately 100% of theoretical by shaking with a second
aqueous solution which differed from the first only in
containing 500 ~l of calcium chloride dihydrate. Again
any separation of complex from the organic solution was
noted (Test 2). Results are listed below in Tabl~ 4~
326~
32
Dx.31682 A
Table 4
Alcohol used Test 1 Test 2
18 Mixed isomer Immediate
iso-octanol precipitation
occurred
19 2-e-thylhexanol
Commercial nonanol
(3,5,5-trimethyl-
hexanol)
21 Diisobutyl No Precipitation
carbinol precipitation occurred
a~ter 2 weeks
22 Mixed iso~er ll No
isononanolC precipitation
after 2 weeks
2~ Mixed isomer
isodecanol
24 Mixed isomer Some
tridecanol precipitation
occurred but
only after
. 2 weeks
_~_ _ _ _ . _.
~ The mixed isomer isononanol was obtained by h~drofor~ylation
of a mixed octene stream.
The results indicate that the bis esters of
Example6 18, 19, 20, 21 and 24 would require to be used
in more dilute solution or in a more polar solvent than
ESCAID 100, for example a solvent having a higher aromatic
content, but that the bis esters of Examples 22 and 2~ and
their copper complexes have excellent solubility even in
conce~trated solution in a very weakly polar solvent of low
aromatic co~tent.
~5
3;~
33
Dx.31682A
N1N,NI,N~-tetraisoamyl pyridine-2,5-dicarboxamide
was prepared using the method of EXample 1 from pyridL~e-
2,5-dicarboxylic acid and diisoamylamine. The crude product
in toluene 60lution was washed several times with 005M aqueous
sodium hydroxide ~nd then with 0.5M aqueous hydrochloric acid
and water. The solution was then treated with charcoal
and filtered. The solvent was distilled under reduced
pressure, but the product, a brown oil, wa6 not itself
distilled. It was made up as a 0.2M solution in AROMASOL
and tested for extraction of copper in the presence of
chloride ion using the method o~ Examples 6 and 7 except
that AROMAS0~ ~ was used as solvent. The results are given
in Table 3. The results indicate that this is a very
weak extracta~t suitable for recovering copper from aqueous
solution of high chloride ion concentrations.
3-hexylundecylamine was prepared from Z-hexyldecanol
as follows~ The alcohol was heated to 96-107J
ZO and stirred whilst a stream of hydrogen bromide gas was
bubbled through it for 4 hours~ The organic layer was
separated, and washed first with SS~ sulphuric acid and then
with water, aqueous ammonia u~til neutral, and water1 and then
distilled yielding 1-bromo-2-hexyldecane (b.p~140 at 1 mm
pressure). The bro~o compound was conYerted to 1-cyano-2-
hexyldecane by stirring it at the reflux temperature with
excess of a 44~ aqueous solution of sodiu~ cyanide, in the
presence of methyl trioctyl ammoniu~ chloride as a ~haRe
transfer catalyst, following C.M.Starks (Journal of the
American Chemical Society, 93, page 195, 1971). After
washing with dilute aqueous sodium hydroxide sol~ltion and
'''`i:~,
, ~
32~7
34
Dx.31682A
water, the cyano compound (141 gram6) was di6solved in
ethanol (1~0 ml~ and poured into an autoclave~ Liquid
am~onia (150 6) was added and the autoclave was pressurified
to 50 at~ospheres with hydrogen7 sealed, and heated to
170 for 24 hours. The autoclave w~s cooled, a~d most of
the ammonia allowed to evaporate. The ~olution was
filtered and the solvent was distilled under reduced
pressure. It was found by gas chromatography that complete
conversion to 3-hexylundecylamine had taken place.
N,N~-bis(3-hexylundecyl)pyridine-2,5 dicarboxamide
was prepared using the method of Example 1 from 3-hexyl-
undecylamine and pyridine 2,5-dicarboxylic acid. The
product which was a brown oil was not distilled but was
analysed as being 92~o of theoretical strength (based on
MW 642) by titration of an aliquot in acetic aGid with
perchloric acid. It was made up as a 0.2M solution
in AROMASOL ~ and tested for extraction of copper in the
presence of chloride ion using the method of Examples 6
and 7. The results are given in Table 3. They indicated
that this compound is a strong extractant for copper which
would be best employed in extracting copper fron solutions
of relatively low chloride ion concentration and relati~ely
low acidity.
