Note: Descriptions are shown in the official language in which they were submitted.
WO 93~04208 2 ~ /us~2/~ 8
COPPER RECOVERY PROCESS
~=Y~
5 Field~of the~ Inventic)n:
This inv~ntion rel~es to a proc~ss for the recovery of
copper from chalcocite corlce.ntrates by a proces~ of partial
leaching t~f the cc: ncentrate and ex~raction of the r~sulting
aqueous ammoniacal leach solution.
Statement s:~f Related Art:
Practice in the r~covery of copper from its sulfidic ores
voIves subj~c:ting the ores to a fro~h flotation operation to
~: p~oduce a corc ntrate of the valuable metal sulfidQ~ and to
15 reject in the flotation tailing~ of valueless sul~ides,
silicates, aluminat~s and the like. One of such concentrates
;provided is a chalcocite concentrate containing chalcocit~ and
c~vellite.
In U~ S . Patent 4, 022, 866 to Kuhn and ~biter, and in
20: tlheir ~ubsequent paper, "Physical and Chemical Separations vi~
the Arbiter Proce~s" 11th International Mining Congr ~s,
Aprilr 1975 Cagliari, Italy; Proc.-Int. Miner. Process.
~ongres~, Paper 30; pp~831-847; there is described the
leac:hing of copper sulfide concentrates with am~nonia/ammonium
sulfate and oxygen whereby the sulfide is converted to
sulf~te, and the dissolved copper may then be recovered by
~3UB~;TITOTE ~;HEET
WO 93~04208 2 1 1 ~ ~ 6 0 P~r/llS92/064g~
solvent extraction. In the patent complete leaching of the
copper from the o:re is preferred althollgh Fig. 3 alsc:
descxibes an embodiment in which a partial leaching is
contemplated. The solvent extraction reagents are des::ribed in
the patent only generally a5 those which preferentially lo~ad
copper from alkaline solutions. In the paper, whic:h describes
the operation of the Arbiter process, the focus is on complete
(or nearly complete) leac:hing of the sulfidP corlc:erltrat s~ On
page 834 a chalcocite concentrate is specifically discussed
and diagraDed, with all the copper and associated ~;ulfur
being dissolved.
In another Kuhn and Arbiter paper, "Anaconda ' s Arbiter
Proc~ss ~Eor Copper"/ Hydrometa~lurgy, CII~ Bulletin, Feb. 1974,
pp. 62-73, make5 reference to '~complete dis~olu~ion of c:opper~'
and on page 65, refers to the known conversic:n of chalcocite
to covellite I but points out that th ::halcclcite and
covellite "are observed to be completely attaGked and
dissolved in our leachin~ system within 1 to 1 1/2 hours~'.
U. S . Patent 4, 563, 256 des ::ribes a solv~nt extraction
process for the recovery of zinc values from ammoniacal
solutions, which ma~ al~o corltain c~pper values, employing
various oximes as the extractants.
A paper by Anthony 0. Filmer et al, "Oxidation of Copper
Sulfides in Aqueous Ammonia" part III, ~'Kinetlc
ChararteristiCS", Austr. J. Chem~ 1979,32,pp. 2597-2609, gi~ves
a de~ailed study of the ammoniacal oxidation of chalcocite,
f irst to co~ellite, then to complete dissolution .
U. S Patent 2, 727, 818 descri}:Jes a method of leaching
copper ~;ulf ide materials with ammoniacal leach sslutions,
indicating that the first Cu from Cu2S (chalcocite~ dissolves
without dissolutiorl of sulfur, and the Cu from CllS (covellite)
dissolves only when its sulfur also dissolves. N~ solvent
extras::tion is discussed.
U. S . Patents 4, 065, 502 and 4 ,175, 012 describes beta-
diketones which may be employed as metal extrac:tants in a
~3U~3STITUTE ~iHEET
WO ~3/0'120~ PCr/US92/06~08
2115160
lic~uid i~n exchange process for recovery of metals, such as
ni~kel or copper, from aqueous solutions containing the metal
values, including aqueous ammoniac:al ~olutions.
DESCRIPTION OF THE_DRAWING
Figure 1 is a diagrammatic f low chart illustrating a
partial leaching of a copper c:oncentrate and a liquid-liquid
extractiorl of the coppQr vallles ~rom the resulting leach
solution, followed by recovery of the copper, either in the
f orm of copper sulf ate crystals or as athode copper by
elec:trowinning.
DESCRIPTlON OF_T~ INVENTT~N
In thi~ descriptiorl; except in the operating examples or
where explicitly other-wise indicated, all number~; describ~ ng
..... amounts of ingredients or reaction condiltic3ns are to be
under~tos~d as modif ied by the word "about'l .
It has now b2en disc:c)v~red that t~e combination of a
partial laaching of chalcocite and the use of a high copper-
transfer/ low ammonia-loading extraction reagent provides a
very e~ficient process o~ recovery of copper. Because of the
partial leaching, up to 50% leach, there is no conversion of
the sulur from sulfide to sulfate, which results when
complete dissolution of th concentrate is carried out. With
the conversion t~ sulfate, as practiced in the Arbiter
process~ much of the ammonia is tied up as ammonium sulfate.
: 25 In order to liberate the a~monia, the sulfate must be treated
in an energy int~nsive proces~. In the present invention
a~monia recov~ry i~ simplifi~d as, in the solvent extraction
u ing the reagents employed in the pre~ent nvention, ammonia
is automatically regenerated during extraction and is simply
recycled back via the raffinate for further leaching. Since
the sulfur is not convexted to sulfate in the partial leaching
of the present inv~ntion, the sul~ur, which remains in the
leach residue, is concentrated by flotation and is removed to
a smelting process as ~hown in Figure 1, where sulfuric acid
may con~eniently and efficiently be produced.
~;IVBSTITUTE SHEET
WO 93/04208 2 1 1 5 1 6 0 PCll~lS92/064~8
In the copper recovery process of the present invention,
a chalcocite concentrate is subjected to a par~ial leaching
with ammonia and ammonium sulfate solution. ~hile ammoniu~n
sulfate is preferred in order to mainkairl the sulfate matrix
5 throughout the system and ensure consistent quality of
product, other ammonium cs~mpounds, such as the carbonate,
nitrate and chloride may be employed; however, these may
re~uire specialized eqlaipment or additional proc:essing stages.
Ch2l1cocite cs:nc~ntrate is ltypically compo~ed of about 75-90%
10 chalcocite (Cu2S~, though some may contsin in excess of 90% ,
wi~h the rem~inder bQing substalttially s: ovellite (CuS), with
trace a~aounts of chalcopyrite ~CuFeS2~ or other form~ o~
copper .
~ s shown in the Figure, the chalcoeite concentrate is
15 contacted with ammonium sulfate solution and free ammonia,
prei~erably in the for~a of am~aonium hydroxide, with agitation
to ~o~m a slurry which may r~nge frc~m about 10% to about 7596
~;olids, typically about 30-60%, with 35-50% bein~ preferred.
The higher the percent solids. attained j the smaller the size
20 o~ the leac:hing vessel whis::h is require:31 and the higher the
c:oncentration of the copper contained in the aqueous phase.
The lea ::hing is conducted at a pH in the range of abc3u~ 8 . 5 to
11 to produce cupric: anunonium sulfate and is conducted at
ambient temperature and pres~;ure, until the remaining copper
25 is present as covellite (CuS). Thus the chalc~cite (Cu2S) is
leached so as to rem~ve suffic:ient copper (half of the Cu2) to
leave a residue comprised substantially of CuS ( covellite) ..
While one of the advantages of the pr~sent ir veT~tion lies ~n
the use of ambient temperature and pressure and does not
3 0 require elevated tempsratures or pre~;sur~s, elevated
temperature and pressure may be employed, if desired, or where
specialized ambient conditiorls exist, s~ch as extreme c:old
conditions. Since the sulfur is not being converted to
sulfatg, no oxygen is required, however, air may be sparged
35 into the leach ve5sel which tends to expedite the dissolution
SUBSTITUTE~ 5HEET
WC) 93/lD4~08 P~/US9~/064~g
2 ) ~
of the chalcocite in the presence of free ~mmonia and the
conversion of Cu+ ion to Cu~+ ion to provide the cupric
ammonium sulfate. Leach rekention time is deperldent on the
desired percentage of copper to be solubilized, however,
5 typically 30 to 90 minutes is generally sufficient to
solubilize 20-35% of the total copper c::ontained in the form
of chalcocite, using an air sparge at typical ar~ient
temperatures and pre~;sures, i~e. 20-23 degrees t:~ntigrade and
atmospheric pressure.
In the leaching step of the present invenl;ion the
leachirls~ should not substarltially exceed the conversion DiE the
chalr::ocite to covellit~, e. g. r~moval of c~ne part of copper
~rom c:halcocite compound which contains 2 parts of copper. If
~ the resulting covellite is leached in the present process,
15 there would occur an oxidation of the contained sulfur to
sulfate, which is to be avoided or minimized in the present
invention, since with any i:ncrease in sulf ate, it is then
required to incorporate a sulf ate bleed stream and a
sub~e~uerlt make-up of ammoni.a 105t in the f orm of amms: nium
20 ~ulfate. Desirably the only :Losses of ammonia in the process
of the presellt invention will be only a small amourlt contained
in the solids which is lost n the solid/liquid ~eparation
step shown in the f low diagram of Figure 1.
The leaching is pref erably conducted in a continuous
25 fashion with the original conc:entrate entering the first stage
of l each and mixing with the raf f irlate from the subsequent
extraction step. Anhydrous ammonia or ammonium hydroxide i~
added as needed to maint~in a leach pH betwean about 8 . 5~11.
Ammonium sulfate ~hould be maintained at a level c: f at least
30 khe stoichiometric quantity rç~uired to solubilize the desired
amount of copper contained in the concentrate. Preferably the
~mmonium sulfate is maintained at a level slightly ill excess
of the stoichiometric amount, typically at about 10-20~6
excess, and pref erably at about 15~ excess . This amount of
3 5 excess will ensure the amount of copper desired to be
SUI~STllrlJTE~ 5HEI~
WO 93/1~4~08 ~ 1 1 5 ~ ) P~/U~92/06408
solubilized (one Cu from the Cu2S), without any substantial
solubilization Cf CU from the c:ovellite and without any
substan~ial conversion of sulfidic sulfur to sulfate.
~s shown in Figure 1, a~ter the leac::hing, t:he leach
slurry is di~charged from the leaching ve~sel and a
li~uid/~;olid separation is performed, whic:h may be simple
dec:antation or a filtration step. The solids are preferably
wash~d with water, and/or ammonia water solu1:ion, free of
copper tc) remove any cc:pper in solution entrained in the
~0 solids. As further shown in Figur~ 1, the washe~ and filtered
solids may be subj0cted to flotation, to produc~ a new copper
concentrate, c:omposed primarily of covellite, CuS. The new
covellite sulfide concentrate will contain a higher fuel value
f or s~absequent pyrometallllrgical treatment than the original
1~ chalcocite concentrate in regard to the copper~sulfur ratio
~herein. Any preciolls metals ~uch as silver or goldr or other
sulfide minerals, suc:h as molybdenite, which were initially
present will also be found in the new ~lotatic)n concentra~e
from whish they may be ~Eurther processed and rec:overed.
The copper pregnant l~ach ~olution, along with the
washing solutions from washing of the solids a~; described
ab~ve, will then be sent to the extraction stage of the
process, preferably after clarification to remove any fine
soll ds which may be present from the previous step . Such
clarif ication is preferably carried ou~ by f iltration . In the
extraction stage, the pr~gnant copper leach solution whis::h now
will c:ontain from about 15 100 grams per liter (g/l) copper,
typically about 3 0~4 0 g/ 1, at abs:~ut pH 9 to 10 is contacted
with a water-immiscible, organic solvent solution of an
extractant compound havin~ a high copper loading, low ammonia
loading, capac:ity so as to result in a tran~f er of the copper
to the organic solvent solution whi~h f orms an organic phase
substantially immisc:ible with the as~U80us copper pregnant
leach solution.
In Figure 1, the extractiorl stage is shown as a single
SUBSTlTlJTI~ SHE~ET
WO 93/042~ 2 1 1 5 1 6 ~lPcr/US92/0640~
block. In practice, the extractiorl would be carried out in a
continuous countercurrent process ~ typically employing up to
three extraction stages, in a series of mixer settler units in
which the outlet of a mixer continuous~y feed~; a large
5 ~ettling ~ank where the organic ~;olvent (orga:n ic pha~;e~, now
c:ontaining the copper extract~nt complex in solution is
separated from the depleted a~ueous ~olution (a~ueous pha~
This part of the process is ref erred to as the phase
separation. Usualïy the extra::tion proGess is repeated thrc:uqh
10 two or more mixer~;ettler UllitS ~ n order to more completely
extract the copper. Where two mixer ~ettler units are
employed, the copper pregnant leach solution will be
introduced to the f irst mixer-settler u~it extraction ~;tage
r~ (often de~ignated E-1) where it is contacked with the organic:
15 phase exiting from th~ sec:on~ mixer-settler extraction stage
toften designat~d E-2), thereby invvlving a count~rcurrent
f low of the orgarlic phase and the aqueous copper solution
phase. The aqueous ph~se ~rom the first extraction unit (E-l)
is introduced into th~ ~econd mixer~settler ex~raction unit
20 (~ 2), which contact the incomin~ organic phase) recycl~d from
the stripping stage of the proces~. The coppar loaded organic
phase exits E-1 and iB introduced to a washing ~tep prior to
stripping of the copper from the organic phase. ~he aqueous
raffinate (a~nonia and ammc:nium sulfate soIution) from the
25 extraction (unit E:~ 2~, now sub~tantially barr~n of copper,
typically containing less than 1 g/l (and preferably about 0.1
g/l) is re~ycled to the leach step and solids wash steps
earlier described.
The wa~hing st~p may consist of only one stage or, as in
30 the s:ase of the extraction step, may consist of more than one.
The purpose of the wa~hing step is primarily to remove any
entrained, or chemically loaded, ammorlia solution which ~nay
have been loa~ed into the or~anic phase along with lthe copper~
If signif icantly low ammonia loading extractant compounds are
35 employ~d, so that no significant amolmts of ammonia are loaded
SUI~STITUTE~ ~;HEl~
WO 93~)4~8 PCr/~JS9~/06408
2~5~ 8
into the organic phase, the washing ~;tep may be oraitted and is
thus an optional step . It is hs:~waver pref erred that at least
one water wa~hing step, pH ~ontrolle~l at a pH of 6-7 with a
suitable pH adjusting acid, be employed to conserve ammonia
and to minimize contamination of :~;tripping agent employed in
the next step of the process~ If washing is employed after
separatie:n of the aqueous washing pha~e from the organic
phase, the resulting aqueous solutil~n from the washing is
returned to the leaching stepr while the c:opper loaded organic
phase is then contacted with a stripping agent to form the
stripping stage of the process, Pagain the stripping step may
be carried out in a singl~ ;tage or, as in the c:ase of the
extractiorl step, may typically be carried out count~rcurrently
in more s~ages or UllitS, i~e~ in two stages.
As in the extraction step lthe stripping, if carried out
in two units, has the loaded organic phase introdu ed int~ the
f irst strippin~ unit ( S-l ~, where it COl~lt2C:tS the strippillg
agent ~pra~erably sulfuric acid) exiting from the seGorld
s~ripping unit ( S-2 ~, again a countercurrent processing r
Sulfuric acid solution corlt~ining about 60 180 g/l sulfuric
~cid is the preferred stripping agent, as it permits ~he
subsequent recovery of the copper either in the form of copper
~ulfate crystal~ or by electrowinning to c:athode c:opper. Other
inorganic min~ral acids may be employed as skripping agents,
such as hydrochloric acid or nitric acid, however s~ch may
require other recovery methods or specialized handling
equipment. The ~tripped organic, now substantially barren of
the copper and typically containing less th~n 1 g/ l copper
will exit unit S-2 and be introduced to the ~mit E-2 of the
extractic~n ~tep. The copper in the acidic ~tripping solution,
now c:ontainiIlg the copper in a concentrated amount ~ about 50-
60 g/ 1, and typically about 50 g/ 1, is then rec:overed in
conventiorlal manner either by crystallization or
electrowinning, as shown in Figure 1. In elec:trowinning, the
3 5 pref erred recovery method, cathode c:opper is recovered as
~E3UE~SlRlTUTE SHEET
_. .. . ... .
WO 93/04208 2 1 1 ~ ) Pcr/~S92/064~8
electrolytic: copper at a 99 . 99%+ copper. The spent
electrolyte, after deposition of the cathode c:opper, is then
returned to stripping unit S-2. As this is being recycled irato
the proc:ess, the amount of copper lpresent in the spent
electrolyte may be relatively high, thou~h lower than the 50
g/l in the ~;olution from the strippi3~g step, and tyE~ically
may contain from about 20-30 g/l c~pperO If recovery is by
c:rystallization, the c:opper is rec:overed in thP form of copper
sulfate crystal~;, which will typic:ally require the
introduction of ~ome water to lprovide the water o~ hydration
for copper sulfate crystals. The spent solutiorl from the
cryE;tallization, aqueous sulfuric acid, will be recycled t~
the stripping ~;tep, into unit S-2.
As indicated earlier, the copper pregnant leach solution
from which the copper is to be recovered by extraction will
c:ontai3l about 15-100 g/l copp~,r, and typically about 30-40 g/l
copper at pH about 8.5-11. The extraction compounds for u~;e in
the prac:~ice of this imrention on these leach solutions, are
those which will load, i . e ,. at least about 15 g/ l, or
extract, ~opper to a high degree, from high ammonia
concenltration solutions preferably without significant loading
of ammonia. Such compounds, which are preferr~d for use as an
extractant reagent in the present invention because of their
low ammonia loading prop~rties, are certain beta-diketones
such as those described in U~ S. Patents 4, 065, 502 and
4, 015, 980. One such extractant found to be particularly
suitable ~or use in the pr~ent inventivn is l~phenyl-3-
heptyl~ 1,3~propanedione, a~railable commercially from Henkel
Corporatioll as LIXR 54~ Other beta-diketone compounds which
may be employed are defined by the following ~ormula:
O O
R ~ CH - C - R~
R"
whe:re R is phenyl or alkyl substituted phenyl, R ' is alkyl,
alkyl substituted phenyl vr chloro substituted phenyl and R"
'~3~
WO 93/0~208 PCY'/VS92/064~8
21~160 lO
is H or CN with the provisos that ( 1 ) when R is phenyl, R ' is
a br~nched chain alkyl group of at least seven carbon atoms
and (2) when R is alkyl substituted phenyl, the number of
carbon atoms in the alkyl substituent is at least 7 and at
5 least one such alJcyl substituent is a branched chain. R is
desirably monoalkyl substitut:ed and preferably contains 9 or
more c:arbon atoms . The various alkyl groups are pref erably
free from substitution and contain less than 20 carbon altc)ms.
Further when R ' is alkyl, the carbon alpha to the carbonyl
10 group is de~;irab~y not tertiaxy,. Preferably, R" is H, R' is a
branched 7, 8, . 9, 12, or 17 ~arbon ::hain or a c~lorophenyl or
short chain ( 1-5 carbon) a7 kyl substitu~ed phe~l and R is
phenyl or a 7, 8, 9, or 12 carbon alkyl substituted phenyl
~ yroup.
While the beta diketorle compounds are preferred for use
in th~ present inverltion as the water insoluble extra6 tant
compound~; b~cause of their :lo~ ammonia loading properties,
uther water in~oluble copper loading extractants capable of
loading copper from aqueou!; aramoniacal solutions may be
20 employed. ~ith such other reagents it may ~ however, be
nece~sary to include additional trea~ment of the organic phase
because of ammonia loadin~f, before stripping and rec::ycling of
materials in the continuous process. Other high copper loading
extractants, which may be desirably employed, either alone or
25 in admixture, are certain oximes, of those ~escribed in U~ S .
Patent 4,563,256, Oximes which may be employed in the pre~ent
invention are those generally conforming to the formula:
OH NOH
3~
~ ~ C --R2
Rla
SU13STITUTE SHEE~
W093/04208 2 1 1 5 1 ~ ~J P~T/US~2~0~0~
where Rl is a saturated aliphatic group of 1-25 carbon atoms
or an ethylenically unsaturated aliphatic group of 3-25 carbon
atoms or =oR3, where R3 is a saturated or ethylenically
- unsaturated group as defined above, a is an integer of 0, l,
2, 3 or ~ and R2 is H or a saturat~d or ethylenically
- unsaturated group as defined above, with the proviso that the
total number of carbon atoms in Rl and R2 i~ from 3-25, or
phenyl or R4 substituted phenyl where R4 is a saturated or
ethylenlcally unsaturated group a5 defined above which may be
the same or different from Rl. Illustrative of some of the
oxime compounds are 5-heptyl ~alicylaldoxime, 5-octyl
salicylaldoxime, 5-nonyl salicylaldoxime, 5-dodecyl
salicylaldoxime,5-nonyl-~-hydroxyacetophenoneoxime,5-nonyl~
~ hydroxyacetophenone oxime, 2-hydroxy-5-nonyl ~enzophenone
oxime and 2-hydroxy-5-dodecyl benzophenone oxime. ~hile it is
preferred that a single ~xtractant compound be employed,
mixture~ of extra~tants may be employed to meet particular
system r~quirement~.
A wide variety of essentially water~immiscible liquid
hydr~carbon solvents can be used in the copper recovsry
process of the present invent.ion. These include aliphatic an~
aromatic hydrocarbons such as kerosenes, benzene, toluene~
xylen~ and the like. A ch~ice of essentially water-immiscible
liquid hydrocarbon solvents, or mixtures thereof for
commercial operations will depend on a numb~r of factors,
including the plan~ design of the solvent extraction plant
~mixer-~ettler unitsr Podbielnak extractor~) and the like. The
pre~erred ~olvents for use in the recovery process of the
present invention, are the allphatic and aromatic hydrocarbons
having flash points of 130 degre~s Fahrenheit and higher~ and
preferably at least ~50 , and solubilities in water of less
than 0.1% by weight. The solvents are essentially chemically
inert. Representative commercial available solvents are
Chevron ion exchange solvent (available from Standard Oil of
California, having a flash point 195 F, Escaid 100 and 110
'~u~ H~n
WO 93/0~120X PCI/US92/0640~s
i 1 6 ~ 12
(available from Exxon-Europe having a flash point of 180 F. ~,
Norpar 12 (available from Exxon-USA, iElash point 160 F. ),
Conoco-C1214 (available from Corloco, flash point 160 F. ),
Aromatic: 150 (an aromatic kerosene available from Exxon~USA~
5 flash point 150 F. ), and the o~her various kerosenes and
petroleum fractions availi~ble from other oil companies.
In the process of the present inverlt ion, the organic
solvent solutions will preferably contain from about 0.005 up
to about 75% by wei~ht of the oxime compounds, which typically
will be employed at abc3ut 10-15~. In the ca~;e of the beta-
diketone compound, it may be used in an amount approaching
100% solid~, but typic:ally will be employed at about 20-30g6 by
weight. Additionally, volume ratios of the organic: aqueous
(V:A) phase Will vary widely ~:ince the cont~cting of any
15 quantity of the diketone organic solution with the c:opper
containing aqueous leach solution will r~sult in e~traction of
the copper values into the organic phas~. For commercial
practi::ality, however, the organic:a~uaous pha~;e ratios for
extraction are preferably in ll:he range of about 50 :1 to 1: 50 .
20 It is desirable to maintain an effec:tive O ~o A ratit~ of about
1:1 in the mixer by recycle of one of the streams. In the
stripping step, the organic: aqueous stripping medium phase
ratio wi.ll preferably be in the range of about 1:2 to 20:1.
For practical purposes, the extractirlg and skripping axe
25 normally conducted at ambient temperatures and pressures,
although higher and/or lower temperakures and/or pressures are
entirely operable. While the entire proces can be carried out
as a batch operation, as described earlier ~ most
advantageously the entire process is carried out contintlc)usly
3 0 with the various solutions or streams being recycled to the
~arious operations in the process for recovery of the copp!r,
includiny the leaching, extraction and stripping steps.
As indicated, in the extract ion process the extr~ctant
reagent should be soluble in the organic water-immiscible
35 solvent. In general the dilcetone compounds, and other
~UB~;TITUTE ~HEE~T
W093/0420X 2 1 l r~ PcT/us92/o~
extractants, described aboYe will be svluble to such extent in
the amounts described above. If necessary or desirable to
promote desired properties of extraction, a solubility
modifier may be employed. Such solubility modifiers, include
long chain ~6-30 carbon~ aliphatic alcohols or esters, such as
n-hexanol, n 2-ethylhexa~ol, isodecanol, dodecanol,
tridecanol, hexadecanol, octadecanol, is~hexad~canol, 2
(1,3,3-trimethyl butyl3-5,7,7-trimethyl octanol and 2,2,4-
trimethyl-1,3-pentanediol mono- or di- isobutyrate; long chain
alkyl phenols, such as heptylphenol, octylphenol~nonylphenol
and dodecylphenol î and organo-pho~phorus compounds, such as
tri-lower alkyl (4-8 carbon) pho~phates, especially tributyl
phosphate and ~ri-(2-ethylhexyl) phosphate.
~ The invention may be illustrated by means of the
following example in which all parts and percentages are ~y
weight unless otherwise indicated. It i5 understood that the
purpose of the ~xample is entirely illustrative and is in no
way int~nded to limit the scope of the inventiQn.
Exlample
This example will serve to illu~trate the utility and general
operation of the present invention. For this purpose a sample
of chalcocite conc~ntrate, greater than 90% chalcocite,
containing 29.~3% copper was obtained from Mexicana de
Cananea, in Cananea, Son~ra, Mexico.
The dry concentrate (350 grams) was slurried in a
baffled, one liter beaker with 525 milliliter~ (mls) of
ammonia sulfate and ammonium hydroxide solution. The ammonium
~ulfate concentration was 150 grams/liter (g/l) as ammonium
sulfate and the ammonium hydroxide concentration was 25 g/l ~s
ammonium hydroxide. The pH of the ammonium sulfat*-ammonium
hydroxide mixture was 9.5. The slurry was agitated with a six
vaned, single shrouded impeller to keep the solids suspended
in the liquid phase for the duration of the leaching phase.
Air was sparged through a glas5 frit to add some air to the
SUB5TITLITE~ 5HEIET
WO93/(1420X PCT/US9~/0~08
21151G~J
14
slurry and expedite the leaching of the copper. The test was
conducted at ambient tPmperature, about 23 c., and ambient
pressure. ~mmonium hydroxide was added as necessary to
maintain a pH range of 9.3-9.8 for the duration of the
leaching activity. Th~ concentrate was leached in the
described fashion for 90 minutes.
The unleached copper solids were filtered and washed with
distilled water to ~ecover essentially all of the dissolved
copper. The filtrate was collected as pregnant leach solution
with some wash water and a second volume that was essentially
wash water with some contained copper in solution. The higher
grade filtrate has a volume of 780 ml5 and contained 20.3 g/l.
The weaker wash solution had a volume of 490 mls and contain2d
. 0.93 g/l copper.
The wa~hed solids from the leaching 5tage were treated by
flotation t~ produce a second copper concentrate. The solids
were slurried with tap wate:r and the pH was adju~ted with
cal ium oxide to pH 10.5 pr:ior to flotation. The float was
conducted at about 11% sol:ids and Aerofloat 208 Promoter
(sodium diethyl and sodium di-secondary butyl dithiophosphate)
was used at 0.15 pounds per ton as collector. DQwfroth 250 was
used a~ a frother and the dosage was also Onl5 pounds per ton.
Flotation time was 10 minutes and a new concentrate and
tailings were produced. The concentrate ~305.1 grams)
contained 26~85% coppQr and the tailings (24.3 ~rams)
contained 22.0% copper. The new con~entrate is suitable for
processing at a smelter~
The higher grade filtrate, which contained about 20 g/l
copper was used as the aqueous feed to solvent extraction. The
organiG extractant was 1-phenyl-3-heptyl-1.3-propanedione
(LIXR 54) t a~ 20 weight percent, diluted in Escaid 100, a high
flash point keros2ne.
The aqueous solution of cupric ammonium sulfate was
adjusted to pH 9O5 and containing 20.1 g/l copper. This
solution was contacted wi~h the mixed kero~ene-diketone
5U E~STITUTE~ lEET
WO 93/0~208 2 1 l C) 1 6 !) PCI/US92/06~OX
organic solution ~t an organic to aqueous ratio o~ 1 in a
separatory funnel fc)r 10 minutes. The volumes used were 500
mls of aqueous and 500 mls of organic. The solutions were
allowed to separate and analyzed for copper. The copper loaded
5 organic contained 15. 0 g/l and the aqueous or raffinate
contained 5 .1 g/ 1 copper The copper loaded organic phase was
c:ontacted with a synthel:ic spent electrolyte con~aining 30. 3
g/ 1 c:opper and 17 0 g/ 1 sul~uric acid at an organic to aqueous
ratio o~ 1:1 for lO minutes. The phases were allowed ~o
10 separa~e and then analyzed for copper. The stripped organic
contained 0. 08 ~/l copper and the rich electrolyte contained
44.8 g/l copper. The stripped organic was then contac:ted with
the a~ueo~s raffinate (5.1 g/l c:opper) from the first contact
~ to extract additional copper. The secorld contact was also f~sr
15 10 minutes and the two lphases were analyzed a~ter separation.
The second loaded organic contained 5. û2 g~l copper and the
finaI aqueous raffinate cc)ntained 0.35 g/l copper,. The copper
may be remoYed from the rich electrolyte by electrowinning or
~opper ~;ulf ate crystalliæatio;n .
S`UE3 5TlT.l~TE ~E~ET
