Low density high surface area copper powder and electrodeposition process for making same

This invention relates to a low density high surface area copper powder having an apparent density in the range of about 0.20 to about 0.60 gram per cubic centimeter, and a surface area of at least about 0.5 square meter per gram. This invention also relates to an electrodeposition process for making the foregoing copper powder by electrodepositing the copper powder from an electrolyte solution using a critical combination of process parameters. These critical parameters include: a copper ion concentration for the electrolyte solution in the range of about 2 to about 7 grams per liter; a free chloride ion concentration for the electrolyte solution in the range of about 8 to about 20 ppm; an impurity level for the electrolyte solution of no more than about 1.0 gram per liter; and an electrolyte solution that is free of organic additives.

TECHNICAL FIELD 
This invention relates to a low density high surface area copper powder, 
and to an electrodeposition process for making the same. 
BACKGROUND OF THE INVENTION 
Copper powder can be used in powder metallurgy applications to make 
sintered products. The copper powder is typically blended with iron or 
graphite powders, often in combination with alloying powders such as tin. 
It is then compacted and sintered to make the desired product. While this 
technology has been used widely for many years, there is a continuing need 
for higher strength products. A problem with obtaining such higher 
strength products relates to the fact that the sintering process used to 
make these products inherently produces products with relatively high 
concentrations of voids. The present invention offers a solution to this 
problem by providing copper powders having lower apparent densities than 
the those currently available. The copper powders of the present invention 
have apparent densities in the range of about 0.20 to about 0.60 grams per 
cubic centimeter. Currently available low density copper powders, on the 
other hand, generally have apparent densities in excess of about 0.65 
grams per cubic centimeter and typically in excess of about 0.8 gram per 
cubic centimeter. The low density copper powders provided by this 
invention permit a more intimate contacting between the copper powder and 
the powders (e.g., iron, powders, graphite powders, etc.) they are blended 
with during compacting and sintering. This more intimate contacting allows 
for higher strength products having lower void concentrations. 
U.S. Pat. Nos. 5,458,746; 5,520,792; and 5,670,033 disclose a process for 
making copper metal powder from copper-bearing material, comprising: (A) 
contacting said copper-bearing material with an effective amount of at 
least one aqueous leaching solution to dissolve copper ions in said 
leaching solution and form a copper-rich aqueous leach solution; (B) 
contacting said copper-rich aqueous leaching solution with an effective 
amount of at least one water-insoluble extractant to transfer copper ions 
from said copper-rich aqueous leaching solution to said extractant to form 
a copper-rich extractant and a copper-depleted aqueous leaching solution, 
said extractant comprising (i) at least one oxime characterized by a 
hydrocarbon linkage with at least one --OH group and at least one .dbd.NOH 
group attached to different carbon atoms on said hydrocarbon linkage, (ii) 
at least one betadiketone, or (iii) at least one ion-exchange resin; (C) 
separating said copper-rich extractant from said copper-depleted aqueous 
leaching solution; (D) contacting said copper-rich extractant with an 
effective amount of at least one aqueous stripping solution to transfer 
copper ions from said extractant to said stripping solution to form a 
copper-rich stripping solution and a copper-depleted extractant; (E) 
separating said copper-rich stripping solution from said copper-depleted 
extractant to form an electrolyte solution; (F) advancing said electrolyte 
solution to an electrolytic cell equipped with at least one anode and at 
least one cathode, and applying an effective amount of voltage across said 
anode and said cathode to deposit copper metal powder on said cathode; and 
(G) removing copper metal powder from said cathode. 
U.S. Pat. No. 5,516,408 discloses a process for making copper wire directly 
from a copper-bearing material, comprising: (A) contacting said 
copper-bearing material with an effective amount of at least one aqueous 
leaching solution to dissolve copper ions into said leaching solution and 
form a copper-rich aqueous leaching solution; (B) contacting said 
copper-rich aqueous leaching solution with an effective amount of at least 
one water-insoluble extractant to transfer copper ions from said 
copper-rich aqueous leaching solution to said extractant to form a 
copper-rich extractant and a copper-depleted aqueous leaching solution; 
(C) separating said copper-rich extractant from said copper-depleted 
aqueous leaching solution; (D) contacting said copper-rich extractant with 
an effective amount of at least one aqueous stripping solution to transfer 
copper ions from said extractant to said stripping solution to form a 
copper-rich stripping solution and a copper-depleted extractant; (E) 
separating said copper-rich stripping solution from said copper-depleted 
extractant; (F) flowing said copper-rich stripping solution between an 
anode and a cathode, and applying an effective amount of voltage across 
said anode and said cathode to deposit copper on said cathode; (G) 
removing said copper from said cathode; and (H) converting said removed 
copper from (G) to copper wire at a temperature below the melting point of 
said copper. In one embodiment the copper that is deposited on the cathode 
during step (F) is in the form of copper powder, and the process includes 
(H-1) extruding the copper powder to form copper rod or wire and (H-2) 
drawing the copper rod or wire to form copper wire with a desired 
cross-section. 
The article by I. D. Enchev et al, "Production of Copper Powder by the 
Method of Electrolytic Extraction Using a Reversing Current", Porosbkovaya 
Metallurgiya, No. 9 (141), September, 1974, pp. 95-98, discloses the 
results of an investigation into the production of copper from 
electrolytes prepared from lean ore solutions by ion exchange and 
reversing electrolytic extraction. Electrolyte solutions prepared by 
leaching ore wastes and subsequent extraction with ABF dissolved in 
kerosene were used. The article reports the following optimum conditions 
for the electrolytic extraction of copper powder: reversing current 
density of 1200 A/m.sup.2, durations of the normal and reversed polarity 
periods of 5 and 1 minute, respectively; electrolyte acidity and 
temperature of 100-160 grams per liter and 40-50.degree. C., respectively; 
copper ion concentration of 10 grams per liter; graphite anodes and 
titanium cathodes; and powder particle size of 100 microns at a purity of 
99.95% copper. The reference also indicates that the electrolyte solution 
that was tested had a chlorine content of 0.01 gram per liter (10 ppm) and 
an iron content of 0.90-1.20 gram per liter. 
SUMMARY OF THE INVENTION 
This invention relates to a low density high surface area copper powder 
having an apparent density in the range of about 0.20 to about 0.60 gram 
per cubic centimeter, and a surface area of at least about 0.5 square 
meter per gram. This invention also relates to an electrodeposition 
process for making the foregoing copper powder by electrodepositing the 
copper powder from an electrolyte solution using a critical combination of 
process parameters. These critical parameters include: a copper ion 
concentration for the electrolyte solution in the range of about 2 to 
about 7 grams per liter; a free chloride ion concentration for the 
electrolyte solution in the range of about 8 to about 20 ppm; an impurity 
level for the electrolyte solution of no more than about 1.0 gram per 
liter; and an electrolyte solution that is free of organic additives.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The low density high surface area copper powder provided for in accordance 
with this invention has a unique combination of properties which makes it 
particularly suitable for a wide range of applications, especially powder 
metallurgy applications. These properties are achieved as a result of the 
process used for making such powder which involves electrodepositing the 
powder from an electrolyte solution using a critical combination of 
process parameters which are referred to above and discussed in greater 
detail below. 
The Copper Powder 
The copper powder provided by this invention is a low density high surface 
area powder. This copper powder is characterized by dendritic growth and 
branching. In one embodiment, the powder is characterized by secondary and 
tertiary dendrite branching. In one embodiment, the inventive copper 
powder has a regular and symmetrical growth of dendritic branches about a 
common spine; see, FIGS. 3-5 and especially FIG. 5. 
The copper powder has an apparent density in the range of about 0.20 to 
about 0.60 grams per cubic centimeter, and in one embodiment about 0.30 to 
about 0.60 grams per cubic centimeter, and in one embodiment about 0.30 to 
about 0.50 grams per cubic centimeter. Apparent density is measured using 
ASTM Test Method B703. 
This copper powder has a surface area of at least about 0.5 square meters 
per gram, and in one embodiment about 0.5 to about 5 square meters per 
gram, and in one embodiment about 0.5 to about 2 square meters per gram, 
and in one embodiment about 0.5 to about 1.5 square meters per gram, and 
in one embodiment about 0.5 to about 1 square meter per gram. Surface area 
is measured using the BET (Bennett, Edward, Teller) procedure. 
In one embodiment, the mean particle size for the copper powder is in the 
range of about 5 to about 50 microns, and in one embodiment about 10 to 
about 35 microns, and in one embodiment about 15 to about 30 microns. In 
one embodiment, at least about 90% by weight of the powder has a particle 
size that is smaller than about 75 microns; at least about 50% by weight 
of the powder has a particle size that is smaller than about 25 microns; 
and at least about 10% by weight of the powder has a particle size that is 
smaller than about 10 microns. Particle size is measured using ASTM Test 
Method B822. 
In one embodiment, the copper powder has a green density in the range of 
about 4 to about 8 grams per cubic centimeter, and in one embodiment about 
5.4 to about 6.3 grams per cubic centimeter. 
In one embodiment, the copper powder has a green strength in the range of 
about 3,500 to about 7,000 psi, and in one embodiment about 4,500 to about 
6,500 psi. Green strength is measured using ASTM Test Method B312. 
The copper powder, as plated, is non-free flowing as defined in ASTM Test 
Method B417. It is to be understood, however, that subsequent treatment to 
the powder (e.g., agglomerating, etc.,) following plating can render the 
powder flowable. 
The copper powder has a copper content of at least about 99% by weight, and 
in one embodiment at least about 99.2% by weight, and in one embodiment at 
least about 99.8% by weight, and in one embodiment at about 99.9% by 
weight, and in one embodiment at least about 99.99% by weight. 
The foregoing properties of the copper powder of this invention are 
determined when the powder is in an as plated form after washing and 
drying. The term "as plated" refers to the copper powder after it is 
removed from cathode prior to any subsequent sintering, milling, sieving 
or blending operations that the powder might undergo. As plated copper 
powder includes copper powder that has been washed and dried subsequent to 
being removed from the cathode. As plated copper powder also includes 
copper powder that has agglomerated and the agglomerates have been broken. 
The inventive copper powders have a wide variety of uses. They are useful 
in powder metallurgy applications for enhancing the properties of iron 
blends, bronze blends, and the like. The term "iron blend" is used herein 
to refer to blends of elemental powder containing mostly iron. The iron 
blends may also contain other powder elements such as C, Ni, Mo, Ag, and 
the like, as well as small amounts of one or more lubricants which are 
typically in dry powder form. The term "bronze blend" is used herein to 
refer blends of elemental Cu and Sn powders. The bronze blends may contain 
other powder elements such as C and well as small amounts of one or more 
lubricants which are typically in dry powder form. The inventive copper 
powders are useful as additives for enhancing the green strength of the 
foregoing powder blends prior to sintering as well as improving mechanical 
properties such as strength of the sintered products. The powder blends 
are typically placed in a press to shape a part; the part is then sintered 
and thereafter may be subjected to known secondary operations to produce 
the desired final product. The final product is sometimes referred to as 
an iron (or steel) or bronze powder metallurgy (P/M) part. The iron blends 
typically employ the inventive copper powders at concentrations of about 
1% to about 3% by weight. The bronze blends typically employ the inventive 
copper powders at concentrations of about 85% to about 95% by weight. 
The inventive copper powders can be combined with graphite and optionally 
organic binders to make engine, generator and household appliance brushes. 
The low density high surface area characteristics of the copper powder 
provides for enhanced bond strength between the graphite particles. These 
products typically employ the inventive copper powder at a level of about 
20% to about 80% by weight, and in one embodiment about 30% to about 70% 
by weight. 
The copper powders are useful in making friction materials such as brakes, 
clutches, and the like, where the low density high surface area 
characteristics of powder permits the use of smaller concentrations of 
copper powder and higher concentrations of the friction materials (e.g., 
silica, aluminum oxide, etc.). These friction materials typically employ 
the inventive copper powder at a level of about 30% about 90% by weight, 
and in one embodiment about 40% to about 60% by weight. 
The inventive copper powders are useful as lubricant and food additives. 
They are useful in making products having high conductively applications, 
both thermal and electrical. They are useful in making kinetic energy 
penetrators and as biocidal additives for paints and polymers. The 
inventive copper powders are useful in metal injection molding operations 
and in making thermal management devices. They are useful in conductive 
paste applications and as additives for conductive polymer compositions. 
They are useful as alloying additives in metallurgical applications. They 
are useful in making extruded products or as an additive to powder 
feedstocks for making extruded products. They are particularly suitable 
for conversion to cupric oxide and cuprous oxide. 
Electrodeposition Process 
In one embodiment, the inventive copper powder is formed using an 
electrodeposition process which employs as the copper feedstock any 
conventional copper feedstock used for electrodepositing copper, including 
copper shot, scrap copper metal, scrap copper wire, recycled copper, 
cupric oxide, cuprous oxide, and the like. In this embodiment, the copper 
powder is electrodeposited in an electroforming cell equipped with a 
plurality of cathodes and anodes. Typically the cathodes are vertically 
mounted, have flat surfaces, and have square or rectangular shapes. The 
anodes are adjacent to the cathodes and are typically in the form of flat 
plates having the same shape as the cathodes. The gap between the cathodes 
and the anodes is typically from about 1 to about 4 inches, and in one 
embodiment about 1.5 to about 3 inches, and in one embodiment about 1.75 
inches. The anode is a dimensionally stable anode that is made of, for 
example, lead, lead alloy, or titanium coated with a platinum family metal 
(i.e., Pt, Pd, Ir, Ru) or oxide thereof. The cathode is constructed of 
titanium and typically has smooth surfaces on each side for receiving the 
electrodeposited copper powder. The electrolyte solution is formed by 
dissolving the copper feedstock in sulfuric acid. 
The electrolyte solution flows in the gaps between the anodes and cathodes, 
and an electric current is used to apply an effective amount of voltage 
across the anodes and the cathodes to deposit copper on the cathodes. The 
electric current can be a direct current or an alternating current with a 
direct current bias. The flow rate of the electrolyte solution through the 
electroforming cell is generally in the range of about 0.01 to about 0.3 
gallons per minute per square foot of immersed cathode surface area 
(gpm/csa), and in one embodiment about 0.1 to about 0.2 gpm/csa. The 
electrolyte solution has a free sulfuric acid concentration generally in 
the range of about 100 to about 200 grams per liter, and in one embodiment 
about 120 to about 190 grams per liter, and in one embodiment about 165 to 
about 185 grams per liter. In one embodiment, the temperature of the 
electrolyte solution in the electroforming cell is critical and is in the 
range of about 15.degree. C. to about 35.degree. C., and in one embodiment 
about 20.degree. C. to about 30.degree. C. The copper ion concentration is 
critical and is in the range of about 2 to about 7 grams per liter, and in 
one embodiment 3 to about 6 grams per liter, and in one embodiment about 4 
to about 6 grams per liter, and in one embodiment about 5 grams per liter. 
The free chloride ion concentration in the electrolyte solution is also 
critical and is in the range of about 8 to about 20 parts per million 
(ppm), and in one embodiment about 8 ppm to about 15 ppm, and in one 
embodiment about 8 ppm to about 12 ppm, and in one embodiment about 10 
ppm. The current density is in the range of about 80 to about 120 amps per 
square foot (ASF), and in one embodiment about 90 to about 110 ASF, and in 
one embodiment about 100 ASF. 
The impurity level in the electrolyte solution is critical and is 
maintained at a level of no more than about 1.0 gram per liter, and in one 
embodiment no more than about 0.8 gram per liter, and in one embodiment no 
more than about 0.6 gram per liter, and in one embodiment no more than 
about 0.4 gram per liter, and in one embodiment no more than about 0.2 
gram per liter, and in one embodiment no more than about 0.1 gram per 
liter. The term "impurity" refers to any material that is not 
intentionally added to the electrolyte solution during the 
electrodeposition step of the inventive process. Included among the 
impurities that are to be avoided, or limited as indicated above, are 
iron, nickel, bismuth, tin, lead, antimony , arsenic, zinc, silver, 
sodium, nitrates, and the like. In one embodiment, it is critical that the 
concentration of iron be maintained at a level of no more than about 0.2 
gram per liter, and in one embodiment no more than about 0.1 gram per 
liter. 
It is critical that the electrolyte solution be maintained free of organic 
additives. The term "organic additive" refers to any organic material that 
is intentionally added to the electrolyte solution for the purpose of 
altering the properties or characteristics of the copper powder. Examples 
of the organic additives that are to be avoided include: gelatins derived 
from collagen such as animal glue; organic sulfur-containing materials 
such as the thioureas and the iso-thiocyanates (e.g., thiourea, 
thiosinamine (allylthiourea), thiosemicarbazide, etc.); organic sulfonates 
such as ammonium lignosulfonate; and the triazoles such as benzotriazole 
and the substituted benzotriazoles including the alkyl substituted 
benzotriazoles (e.g., tolyltriazole, ethylbenzotriazole, 
hexylbenzotriazole, octylbenzotriazole, etc.) aryl-substituted 
benzotriazole (e.g., phenylbenzotriazoles, etc.) and alkaryl- or 
arylalk-substituted benzotriazole, and substituted benzotriazoles wherein 
the substituents may be, for example, hydroxy, mercapto, alkoxy, halo 
(e.g., chloro), nitro, carboxy or carbalkoxy. Minor or trace amounts of 
the foregoing organic materials may appear as impurities in the 
electrolyte solution, but the amount of such organic material is 
maintained below about 0.5 ppm, and in one embodiment below about 0.05 
ppm. 
Electrodeposition is conducted until the desired build up of copper powder 
on the cathodes is achieved. In one embodiment, electrodeposition is 
continued for about 1 to about 5 hours, and in one embodiment about 1 to 
about 3 hours, and in one embodiment about 1.5 to about 2.5 hours. 
Electrodeposition is then discontinued and the powder is removed from the 
cathodes. The powder can be removed from the cathodes by brushing or 
scraping or using vibration or other mechanical and/or electrical 
techniques known in the art. The powder can be removed by reversing the 
current on the cathodes. The powder can be removed by spraying water or 
electrolyte onto the cathodes as the cathodes are lifted out of the 
electroforming cell, or by spraying electrolyte onto the cathodes without 
removing them from the cell. The powder can be separated from the cathodes 
by inducing turbulent flow in the electrolyte, or by mechanically scraping 
the powder from the cathodes. The powder can be separated by vibrating the 
cathode using ultrasonic energy or by manually or mechanically pounding on 
the cathode. 
In one embodiment, the copper powder that is separated from the cathodes is 
washed sufficiently to remove electrolyte from the powder. Various methods 
can be employed to wash the powder. One method involves washing the powder 
and then dewatering it using a centrifuge. During this process 
antioxidants can be added to prevent or reduce oxidation. The antioxidants 
that can be added include ammonium hydroxide. These antioxidants are added 
to the wash water at a sufficient concentration to provide the wash water 
with a pH of about 7 to about 14, and in one embodiment a pH of about, 9. 
In one embodiment, antioxidants are added at a concentration of about 0.2 
to about 0.9 gram per liter of wash water, and in one embodiment about 0.4 
to about 0.6 gram per liter. 
In one embodiment, an effective amount of a stabilizer is adhered to the 
surface of the copper powder for the purpose of reducing oxidation and 
increasing shelf life. The stabilizer is preferably added to the wash 
water and applied to the surface of the copper powder during washing. 
Examples of the stabilizers that can be used include the triazoles such as 
benzotriazole and substituted benzotriazoles. The substituted triazoles 
include alkyl-substituted benzotriazole (e.g., tolyltriazole, 
ethylbenzotriazole, hexylbenzotriazole, octylbenzotriazole, etc.) 
aryl-substituted benzotriazole (e.g., phenylbenzotriazole, etc.), and 
alkaryl- or arylalk-substituted benzotriazole, and substituted 
benzotriazoles wherein the substituents may be, for example, hydroxy, 
mercapto, alkoxy, halo (e.g., chloro), nitro, carboxy or carbalkoxy. The 
alkylbenzotriazoles include those in which the alkyl group contains 1 to 
about 20 carbon atoms, and in one embodiment 1 to about 8 carbon atoms. 
Benzotriazole is especially useful. The concentration of these triazoles 
in the wash water is, in one embodiment up to about 10,000 ppm, and in one 
embodiment from 0.5 to about 1000 ppm, and in one embodiment from 0.5 to 
about 500 ppm, and in one embodiment from about 0.5 to about 70 ppm. 
In one embodiment, a surfactant is added to the wash water to enhance the 
wetting of the copper powder and/or enhance dispersion of stabilizers in 
the wash water. In one embodiment, the surfactant is a nonionic 
surfactant. The surfactants that can be used include the block copolymers 
of ethylene oxide and propylene oxide generally available for surfactant 
applications. These are sometimes referred to as alkoxylated alcohols. 
Examples of commercially available surfactants that can be used include 
those available from Olin under the trade designation POLY-TERGENT.RTM.. 
Specific examples include POLY-TERGENT.RTM., S-505LF (a nonionic, low 
foaming surfactant identified as a block copolymer of ethylene oxide and 
propylene oxide). The concentration of the surfactant in the wash water is 
generally in the range up to about 500 ppm, and in one embodiment about 5 
to about 500 ppm, and in one embodiment about 100 to about 500 ppm, and in 
one embodiment about 150 to about 250 ppm. 
In one embodiment, the copper powder is washed using an antioxidant 
containing wash water in a first step, and then washed again using a 
stablizer-containing wash water which optionally can also contain a 
surfactant. 
The dewatered copper powder is then dried using conventional copper powder 
drying techniques. The drying techniques that can be used include vacuum 
drying, flash drying, fluidized bed drying, rotary kiln/multi hearth 
drying, or freeze drying. The copper powder can be dried at a temperature 
of about 25 to about 125.degree. C., and in one embodiment about 25 to 
about 85.degree. C., and in one embodiment about 45 to about 55.degree. C. 
The copper powder can be dried in air, in an inert atmosphere, or in a 
vacuum at an absolute pressure in the range of about 0.1 to about 760 
mmHg, and in one embodiment 1 to about 250 mmHg, and in one embodiment 
about 3 to about 10 mmHg. Agglomerates that form during drying can be 
broken using known agglomerate breaking techniques. For example, screens, 
cage mills, cascading screens, and the like, can be used. The powder can 
be separated into desired size fractions using standard separation 
techniques such as screening and then collected and packaged. 
The apparent density of the powder can be increased, if desired, by 
blending it with higher density powders, or by milling (e.g., hammer mill) 
or rolling the powder. These and similar techniques are known in the art. 
Referring now to FIG. 1, a process for electrodepositing the copper powder 
of the invention is disclosed. The apparatus used with this process 
includes a dissolution vessel 100, filters 102 and 104, an electroforming 
cell 106, holding vessel 108, centrifuge 110, drier 112, agglomerate 
breaker 114, screens 116, and storage hoppers 118, 120 and 122. The 
electroforming cell 106 includes vessel 124, vertically mounted anodes 
126, and vertically mounted cathodes 128. An electrolyte solution 130 is 
formed in dissolution vessel 100 by dissolving the copper feedstock in 
sulfuric acid in the presence of air. The copper metal enters vessel 100, 
as indicated by directional arrow 132, in any conventional form which, as 
indicated above, includes copper shot, scrap copper metal, scrap copper 
wire, recycled copper, cupric oxide, cuprous oxide, and the like. The 
sulfuric acid entering vessel 100, as indicated by directional arrow 134, 
typically has a sulfuric acid concentration in the range of about 93% to 
about 98%. Alternatively, the copper feedstock can be dissolved in the 
sulfuric acid in a separate vessel to form a solution and this solution 
can then be advanced to vessel 100. Chloride ions can be added as 
indicated by directional arrow 136. In one embodiment, chloride ions are 
added in the form of hydrochloric acid. Dilution water can be added as 
indicated by directional arrow 138. Electrolyte solution recycled from 
electroforming cell 106, through lines 140 and 142, also enters vessel 
100. The electrolyte may be filtered in filter 104 or it may by-pass 
filter 104 through line 144. The temperature of the electrolyte solution 
130 in vessel 100 is typically in the range of about 15.degree. C. to 
about 35.degree. C., and in one embodiment about 20.degree. C. to about 
30.degree. C. The electrolyte solution 130 is advanced from vessel 100 to 
vessel 124 through lines 146 and 148. The electrolyte solution 130 may be 
filtered in filter 102 prior to entering vessel 124 or, alternatively, it 
may by-pass filter 102 using line 150. Impurities can be removed using 
filters 102 and/or 104. The electrolyte solution 130 used in vessel 108 
has the composition indicated above. 
The electrolyte solution 130 flows between the anodes 126 and cathodes 128. 
The flow rate of the electrolyte through electroforming cell 106 is at a 
rate in the range of about 0.01 to about 0.3 gpm/csa, and in one 
embodiment about 0.1 to about 0.2 gpm/csa. A voltage is applied between 
anodes 126 and cathodes 128 to effect electrodeposition of copper powder 
152 on each side of the cathodes. In one embodiment, the current that is 
used is a direct current, and in one embodiment it is an alternating 
current with a direct current bias. The current density is in the range of 
about 80 to about 120 ASF, and in one embodiment about 100 ASF. 
Electrodeposition of copper powder 152 on cathodes 128 is continued until 
the desired amount of copper powder has deposited on the cathodes. 
Electrodeposition is typically continued for about 1 to about 5 hours, and 
in one embodiment about 1 to about 3 hours, and in one embodiment about 
1.5 to about 2.5 hours. Electrodeposition is then discontinued. Spent 
electrolyte solution 130 is drained from vessel 124 and advanced to vessel 
100 through lines 154 and 156. The copper powder 152 is separated from the 
cathodes 128 by spraying electrolyte on to the cathode resulting in the 
formation of a slurry 158 in the lower cone shaped section 160 of vessel 
124. The slurry 158 is advanced from vessel 124 to vessel 108 through 
lines 154 and 162. The slurry 158 is then advanced from vessel 108 to 
centrifuge 110 through line 164. In centrifuge 110, liquid effluent is 
separated from the copper powder and exits centrifuge 110 through line 169 
and is either recycled to vessel 108 through line 170, or removed through 
line 172 where it is discarded or subjected to further processing. In one 
embodiment, an antioxidant is added to the powder in the centrifuge as 
indicated by directional arrow 166. In one embodiment, a stabilizing agent 
is added to the powder in the centrifuge as indicated by directional arrow 
168. In one embodiment, the antioxidant and stabilizing agent are added to 
the powder in the centrifuge in sequential order with the antioxidant 
preceding the stabilizing agent. When the antioxidant and/or stabilizing 
agent is added to the powder in centrifuge 110, the centrifuge is rotated 
at a sufficient rate to place a centrifugal force of about 2 to about 750 
g's on its contents, and in one embodiment about 10 to about 200 g's, and 
in one embodiment about 10 to about 75 g's, and in one embodiment about 10 
to about 20 g's until the pH of the effluent is in the range of about 7 to 
about 14, and in one embodiment about 7 to about 11, and in one embodiment 
about 9. The rotation rate of the centrifuge is then increased to dewater 
the copper powder. During this dewatering step, the rotation rate of the 
centrifuge is increased to a sufficient level to place a centrifugal force 
on its contents in the range of about 200 to about 750 g's, and in one 
embodiment about 500 to about 750 g's, and in one embodiment about 650 to 
about 700 g's. The copper powder remaining in the centrifuge 110 after 
dewatering is advanced to continuous belt 171 which conveys the powder 
through drier 112. Moisture is removed from the copper powder in drier 112 
as indicated by directional arrow 173. The dried copper powder exits drier 
112 and enters agglomerates breaker 114 wherein agglomerates that form 
during drying are broken. The powder is advanced from aggolmerate breaker 
114 to screens 116 wherein the copper powder is separated into desired 
screen fractions and then advanced to storage hoppers 118, 120 and 122. 
Two screens and three storage hoppers are illustrated in FIG. 1, but those 
skilled in the art will recognize that any desired number of separation 
screens and storage hoppers can be used. In one embodiment, the use of 
separation screens is avoided due to the fact that the size of the copper 
powder produced by this method is relatively uniform. 
The foregoing process can be conducted on a continuous basis or a batch 
basis. In one embodiment, the operation of the electroforming cell is 
conducted on a continuous basis, and the operation of the centrifuge is 
conducted on a batch basis. 
The following examples are provided for purposes of illustrating the 
invention. Unless otherwise indicated, in the following example as well as 
throughout the specification and claims, all parts and percentages are by 
weight, all temperatures are in degrees Celsius, and all pressures are 
atmospheric. 
EXAMPLES 1 
An electroforming cell is used to electrodeposit copper powder from an 
electrolyte solution. The electrolyte solution is an aqueous solution 
having a copper ion concentration of 5 grams per liter, a sulfuric acid 
concentration of 150 grams per liter, and a free chloride ion 
concentration of 10 ppm. The cathodes have an immersed surface area of 32 
inches wide and 36 inches long with plating occurring on both sides. The 
anodes have an immersed surface area of 36 inches wide and 38 inches long. 
Four cathodes and five anodes are used in the cell. The spacing between 
the anodes and cathodes is 1.75 inches. The inside dimensions of the cell 
are 48 inches long, 54 inches wide, and 50 inches deep to the beginning of 
a cone. The bottom of the cell is in the form of a cone to allow for 
copper powder collection in the bottom of the cone. Electrical (DC) 
current is fed to the cell to provide a current density of 100 ASF on the 
immersed surface area of the cathodes. The temperature of the electrolyte 
is 32.degree. C. The cathode material of construction is titanium. The 
anodes are dimensionally stable anodes constructed of titanium coated with 
iridium oxide. The electrolyte flows through the cell at a rate of 0.17 
gpm/csa. The plating time is three hours. The copper powder formed on the 
cathodes has an as plated mean particle size of 22 microns, a surface area 
of 0.7 square meters per gram, and an apparent density of 0.44 grams per 
cubic centimeter. 
EXAMPLE 2 
Copper powder is electrodeposited in an electroforming cell from an 
electrolyte solution having a copper ion concentration of 5 grams per 
liter, a sulfuric acid concentration of 150 grams per liter, and a free 
chloride ion concentration of 10 ppm. The spacing between the anodes and 
cathodes in the cell is 1.75 inches. The current density is 100 ASF. The 
temperature of the electrolyte is 22.degree. C. The cathode material of 
construction is titanium. The anodes are dimensionally stable anodes 
constructed of titanium coated with iridium oxide. The electrolyte flows 
through the cell at a rate of 0.17 gpm/csa. The plating time is two hours. 
The copper powder formed on the cathodes is separated from the cathodes by 
spraying electrolyte on to the powder and the cathodes with the result 
being the formation of a slurry containing the powder. The slurry is 
advanced to a centrifuge. A solution of ammonium hydroxide having a pH of 
10 is added to the slurry. The ratio of ammonium hydroxide solution to 
copper powder is 5 gallons of solution per pound of powder. The centrifuge 
is rotated at a sufficient rate to place a centrifugal force of 16 g's on 
the contents of the centrifuge. This is continued until two minutes after 
the effluent from the centrifuge attains a pH of 9. A stabilizing agent 
consisting of an aqueous solution of benzotriazole at a concentration of 
20 ppm and POLY-TERGENT.RTM. S-505LF at a concentration of 200 ppm is then 
added. The ratio of stabilizing agent to powder is two gallons of 
stabilizing agent per pound of copper powder. The centrifuge is rotated at 
a sufficient rate to place a centrifugal force of 16g's on its contents. 
This is continued for two minutes after the effluent from the centrifuge 
attains a pH of 9. The rotation rate of the centrifuge is then increased 
to a sufficient level to place a centrifugal force of 674 g's on the 
contents of the centrifuge with the result being a dewatering of the 
copper powder. The copper powder is removed from the centrifuge, placed in 
a pan and dried overnight in a vacuum oven at a temperature of 50.degree. 
C. and an absolute pressure of 3 mm Hg. The dried powder is screened to 
break up agglomerates and then packaged. The powder has the following 
properties: 
B.E.T. Surface area: 0.60 m.sup.2 /g 
Apparent density: 0.49 g/cc 
Mean particle size: 27.77 microns 
90% Smaller than: 68.52 microns 
50% Smaller than: 15.91 microns 
10% Smaller than: 5.67 microns 
Green density @ 12 tsi: 6.0 g/cc 
Green strength @ 12 tsi: 4300 psi 
EXAMPLE 3 
Copper powder is electrodeposited in an electroforming cell from an 
electrolyte solution having a copper ion concentration of 5 grams per 
liter, a sulfuric acid concentration of 150 grams per liter and a free 
chloride ion concentration of 10 ppm. The cathodes are made of titanium 
and have an immersed surface area that is 33 inches in width, 48 inches in 
length, and 0.25 inch in thickness with plating occurring on both sides. 
The anodes are dimensionally stable anodes constructed of titanium coated 
with iridium oxide. The anodes have an immersed surface area of 37 inches 
in width, 50 inches in length, and 0.25 inch in thickness. The 
electroforming cell contains 4 cathodes and 5 anodes. The spacing between 
the anodes and cathodes is 1.75 inches. The dimensions of the cell are 56 
inches in length, 43 inches in width, and 89.75 inches in depth to the 
base of a cone-shaped bottom. Electric (DC) current is fed to the cell to 
provide a current density of 100 ASF on the immersed surface area of the 
cathodes. The temperature of the electrolyte is 22.8.degree. C. The flow 
rate of the electrolyte through the cell is 0.11 gpm/csa. The plating time 
is two hours. The copper powder formed on the cathodes is separated from 
the cathodes by spraying electrolyte on to the powder and the cathodes 
with the result being the formation of a slurring containing the powder. 
The slurring is advanced to a centrifuge. A solution of ammonium hydroxide 
having a pH of 10 is added to the slurry. The ratio of ammonium hydroxide 
solution to copper powder is 5 gallons of solution per pound of powder. 
The centrifuge is rotated at a sufficient rate to place a centrifugal 
force of 33g's on its contents until two minutes after the effluent from 
the centrifuge attains a pH of 9. A stabilizing agent consisting of an 
aqueous solution of benzotriazole at a concentration of 20 ppm and 
POLY-TERGENT.RTM. S-505LF at a concentration of 200 ppm is then added. The 
ratio of stabilizing agent solution to powder is two gallons of 
stabilizing agent solution per pound of copper powder. The centrifuge is 
rotated at a sufficient rate to place a centrifugal force on its contents 
of 33g's until two minutes after the effluent from the centrifuge attains 
a pH of 9. The rotation rate of the centrifuge is then increased to a 
sufficient level to place a centrifugal force of 500 g's on the contents 
of the centrifuge with the result being a dewatering of the copper powder. 
The copper powder is placed in a pan and dried overnight in a vacuum oven 
at a temperature of 50.degree. C. and an absolute pressure of about 3 mm 
Hg. The dried powder is screened to break up agglomerates and then 
packaged. The powder has the following properties: 
B.E.T. Surface area: 0.915 m.sup.2 /g 
Apparent density: 0.44 g/cc 
Mean particle size: 21.26 microns 
90% Smaller than: 36.07 microns 
50% Smaller than: 18.82 microns 
10% Smaller than: 8.90 microns 
Green density @ 12 tsi: 5.68 g/cc 
Green strength @ 12 tsi: 6282 psi 
Photomicrographs of samples of the powder are taken at magnification 
factors of 500.times., 1500.times. and 3000.times.. These photomicrographs 
are attached as FIGS. 3-5, respectively. These photomicrographs disclose a 
copper powder having a highly dendritic crystal structure characterized by 
a symmetrical growth of dendritic branches about a common spine. 
Solvent Extraction/Electrodeposition Process 
In one embodiment, the copper powder is formed in a process using solvent 
extraction in combination with electrodeposition. In this embodiment, the 
copper feedstock is any copper-bearing material from which copper may be 
extracted. These feedstocks include copper ore, smelter flue dust, copper 
cement, copper concentrates, copper smelter products, copper sulfate, and 
copper-containing waste. The term "copper-containing waste" refers to any 
solid or liquid waste material (e.g., garbage, sludge, effluent streams, 
etc.) that contains copper. These waste materials include hazardous 
wastes. Specific examples of wastes that can be used are copper oxides 
obtained from treating spent cupric chloride etchants. 
The copper ore can be ore taken from an open pit mine. The ore is hauled to 
a heap-leaching dump which is typically built on an area underlain with a 
liner, such as a thick high-density polyethylene liner, to prevent loss of 
leaching fluids into the surrounding water shed. A typical heap-leaching 
dump has a surface area of, for example, about 125,000 square feet and 
contains approximately 110,000 tons of ore. As leaching progresses and new 
dumps are built on top of the old dumps, they become increasingly higher 
and eventually reach heights of, for example, about 250 feet or more. A 
network of pipes and wobbler sprinklers is laid on the surface of a newly 
completed dump and a weak solution of sulfuric acid is continuously 
sprayed at a rate of, for example, about 0.8 gallon per minute per 100 
square feet of surface area. The leaching solution percolates down through 
the dump, dissolves copper in the ore, flows from the dump base as a 
copper-rich aqueous leach solution, drains into a collection pond, and is 
pumped to a feed pond for subsequent treatment using the inventive 
process. 
With some mining operations in-situ leaching is used to extract copper 
values from copper ore. The copper-rich leach solution obtained by this 
process can be used in the inventive process as the copper-bearing 
material. In-situ leaching is useful when reserves of acid-soluble oxide 
ore lie beneath an open pit area and above the depleted portion of an 
underground mine or when a deposit is buried too deeply to be economically 
developed by open pit methods. Injection wells are drilled into this zone 
at a depth of, for example, about 1000 feet. The wells are cased with 
polyvinylchloride pipe, the bottom portion of which is slotted to allow 
solution into the ore. A leach solution of weak sulfuric acid is injected 
into each well at a rate dependent upon the permeability of the zone into 
which it is drilled. The solution percolates down through the ore zone, 
dissolves the copper minerals, and drains into a prepared collection area. 
The collection area can be, for example, haulage drifts of the underground 
mine. The copper-bearing aqueous leach solution that is produced is pumped 
to the surface by means of a corrosion-resistant pumping system where it 
is available for use as the copper-bearing material for the inventive 
process. Alternatively, the copper-bearing aqueous leach solution can be 
collected through wells that bring the solution to the surface. 
In mining operations wherein both leach dumps and in-situ leaching are 
employed, the copper-bearing leach solution (sometimes referred to as a 
pregnant leach solution) from each can be combined and used as the 
copper-bearing material in the inventive process. 
In this embodiment, the copper powder is made by the steps of: (A) 
contacting the copper-bearing material with an effective amount of at 
least one aqueous leaching solution to dissolve copper ions into said 
leaching solution and form a copper-rich aqueous leaching solution; (B) 
contacting the copper-rich aqueous leaching solution with an effective 
amount of at least one water-insoluble extractant to transfer copper ions 
from said copper-rich aqueous leaching solution to said extractant to form 
a copper-rich extractant and a copper-depleted aqueous leaching solution; 
(C) separating the copper-rich extractant from the copper-depleted aqueous 
leaching solution; (D) contacting the copper-rich extractant with an 
effective amount of at least one aqueous stripping solution to transfer 
copper ions from said extractant to said stripping solution to form a 
copper-rich stripping solution and a copper-depleted extractant; (E) 
separating the copper-rich stripping solution from the copper-depleted 
extractant; (F) flowing the copper-rich stripping solution between an 
anode and a cathode, and applying an effective amount of voltage across 
the anode and the cathode to deposit copper metal powder on the cathode; 
and (G) removing the copper powder from the cathode. 
The aqueous leaching solution used in step (A) of the inventive process is, 
in one embodiment, a sulfuric acid solution, halide acid solution (HCl, 
HF, HBr, etc.) or an ammonia solution. The sulfuric or halide acid 
solution generally has a sulfuric or halide acid concentration in the 
range of about 5 to about 50 grams per liter, and in one embodiment about 
5 to about 40 grams per liter, and in one embodiment about 10 to about 30 
grams per liter. 
The ammonia solution generally has an ammonia concentration in the range of 
about 20 to about 140 grams per liter, and in one embodiment about 30 to 
about 90 grams per liter. The pH of this solution is generally in the 
range of about 7 to about 11, and in one embodiment about 8 to about 9. 
The copper-rich aqueous leaching solution or pregnant leaching solution 
formed during step (A) generally has a copper ion concentration in the 
range of about 0.4 to about 5 grams per liter, and in one embodiment about 
0.4 to about 3 grams per liter, and in one embodiment about 0.4 to about 1 
gram per liter. When the leaching solution used in step (A) is a sulfuric 
acid solution, the concentration of free sulfuric acid in the copper-rich 
aqueous leaching solution is generally from about 5 to about 30 grams per 
liter, and in one embodiment about 10 to about 20 grams per liter. When 
the leaching solution used in step (A) is an ammonia solution, the 
concentration of free ammonia in the copper-rich aqueous leaching solution 
is generally from about 10 to about 130 grams per liter, and in one 
embodiment about 30 to about 90 grams per liter. 
The water-insoluble extractant used in step (B) can be any water-insoluble 
extractant capable of extracting copper ions from an aqueous medium. In 
one embodiment the extractant is dissolved in a water-immiscible organic 
solvent. (The terms "water-immiscible" and "water-insoluble" refer to 
compositions that are not soluble in water above a level of about 1 gram 
per liter at 25.degree. C.) The solvent can be any water-immiscible 
solvent for the extractant with kerosene, benzene, toluene, xylene, 
naphthalene, fuel oil, diesel fuel and the like being useful, and with 
kerosene being preferred. Examples of useful kerosenes are SX-7 and SX-12 
which are available from Phillips Petroleum. 
In one embodiment the extractant is an organic compound containing at least 
two functional groups attached to different carbon atoms of a hydrocarbon 
linkage, one of the functional groups being --OH and the other of said 
functional groups being .dbd.NOH. These compounds can be referred to as 
oximes. In one embodiment the extractant is an oxime represented by the 
formula 
##STR1## 
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.4, R.sup.5, R.sup.6 and 
R.sup.7 are independently hydrogen or hydrocarbyl groups. Compounds with 
this structure are available from Henkel Corporation under the trade 
designation LIX. For example, R.sup.1 and R.sup.4 can each be butyl; 
R.sup.2, R.sup.3 and R.sup.6 can each be hydrogen; and R.sup.5 and R.sup.7 
can each be ethyl. Compounds with this structure are available from Henkel 
Corporation under the trade designation LIX 63. 
In one embodiment the extractant is an oxime represented by the formula 
##STR2## 
wherein R.sup.1 and R.sup.2 are independently hydrogen or hydrocarbyl 
groups. Useful embodiments include those wherein R.sup.1 is an alkyl group 
of about 6 to about 20 carbon atoms, and in one embodiment about 9 to 
about 12 carbon atoms; and R.sup.2 is hydrogen, an alkyl group of 1 to 
about 4 carbon atoms, and in one embodiment 1 or 2 carbon atoms, or 
R.sup.2 is phenyl. The phenyl group can be substituted or unsubstituted 
with the latter being preferred. The following compounds, which are based 
upon the above-indicated formula, are available from Henkel Corporation 
under the trade designations indicated below and are useful with the 
inventive process: 
______________________________________ 
Trade Designation 
R.sup.1 R.sup.2 
______________________________________ 
LIX 65 Nonyl Phenyl 
LIX 84 Nonyl Methyl 
LIX 860 Dodecyl Hydrogen 
______________________________________ 
Other commercially available materials available from Henkel Corporation 
that are useful include: LIX 64N (identified as a mixture of LIX 65 and 
LIX 63); and LIX 864 and LIX 984 (identified as mixtures of LIX 860 and 
LIX 84). 
In one embodiment the extractant is a betadiketone. These compounds can be 
represented by the formula 
##STR3## 
wherein R.sup.1 and R.sup.2 are independently alkyl groups or aryl groups. 
The alkyl groups generally contain 1 to about 10 carbon atoms. The aryl 
groups are generally phenyl. An example of a commercial extractant 
available from Henkel Corporation corresponding to the above formula is 
LIX 54. These betadiketones are useful when the leaching solution used in 
step (A) is an ammonia solution. 
The concentration of the extractant in the organic solution is generally in 
the range of about 2% to about 40% by weight. In one embodiment the 
organic solution contains from about 5% to about 10%, or about 6% to about 
8%, or about 7% by weight of LIX 984, with the remainder being SX-7. 
In one embodiment the extractant is an ion-exchange resin. These resins are 
typically small granular or bead-like materials having of two principal 
parts: a resinous matrix serving as a structural portion, and an 
ion-active group serving as the functional portion. The functional group 
is generally selected from those functional groups that are reactive with 
copper ions. Examples of such functional groups include --SO.sub.3.sup.-, 
--COO.sup.-, 
##STR4## 
Useful resin matrixes include the copolymers of styrene and 
divinylbenzene. Examples of commercially available resins that can be used 
include IRC-718 (a product of Rohm & Haas identified as a tertiary amine 
substituted copolymer of styrene and divinylbenzene), IR-200 (a product of 
Rohm & Haas identified as sulfonated copolymer of styrene and 
divinylbenzene), IR-120 (a product of Rohm & Haas identified as sulfonated 
copolymer of styrene and divinylbenzene), XFS 4196 (a product of Dow 
identified as a macroporous polystyrene/divinylbenzene copolymer to which 
has been attached N-(2-hydroxyethyl)-picolylamine), and XFS 43084 (a 
product of Dow identified as a macroporous polystyrene/divinylbenzene 
copolymer to which has been attached N-(2-hydroxypropyl)-picolylamine). 
These resins are typically used in the inventive process as fixed beds or 
moving beds. During step (B) of the inventive process, the resin is 
contacted with the copper-rich aqueous leach solution from step (A), the 
contacting being sufficient to transfer copper ions from the leach 
solution to the resin. The copper-rich resin is then stripped during step 
(D) to provide a copper-stripped or copper-depleted resin which can be 
used during step (B). 
The copper-rich extractant that is separated during step (C) has a 
concentration of copper in the range of about 1 to about 6 grams per liter 
of extractant, and in one embodiment about 2 to about 4 grams per liter of 
extractant. The copper-depleted aqueous leaching solution that is 
separated during step (C) typically has a copper ion concentration in the 
range of about 0.01 to about 0.8 grams per liter, and in one embodiment 
about 0.04 to about 0.2 grams per liter. When the leaching solution used 
in step (A) is a sulfuric acid solution, the concentration of free 
sulfuric acid in the copper-depleted aqueous leaching solution separated 
during step (C) is generally from about 5 to about 50 grams per liter, and 
in one embodiment about 5 to about 40 grams per liter, and in one 
embodiment about 10 to about 30 grams per liter. When the leaching 
solution used in step (A) is an ammonia solution, the concentration of 
free ammonia in the copper-depleted aqueous leaching solution separated 
during step (C) is generally from about 10 to about 130 grams per liter, 
and in one embodiment about 30 to about 90 grams per liter. 
In one embodiment the contacting and separating steps (B) and (C) are 
conducted in two stages. In this embodiment, steps (B-1) and (B-2) are 
contacting steps, and steps (C-1) and (C-2) are separating steps. Thus, in 
this embodiment, the inventive process involves the following sequence of 
steps: (A), (B-1), (C-1), (B-2), (C-2), (D), (E), (F) and (G) with process 
streams from several of these steps being recirculated to other steps in 
the process. Step (B-1) involves contacting the copper-rich aqueous 
leaching solution formed during step (A) with an effective amount of at 
least one copper-bearing water-insoluble extractant from step (C-2) to 
transfer copper ions from said copper-rich aqueous leaching solution to 
said copper-bearing extractant to form a copper-rich extractant and a 
first copper-depleted aqueous leaching solution. Step (C-1) involves 
separating the copper-rich extractant formed during step (B-1) from the 
first copper-depleted aqueous leaching solution formed during step (B-1). 
The copper-rich extractant that is separated during step (C-1) generally 
has a concentration of copper in the range of about 1 to about 6 grams per 
liter of extractant, and in one embodiment about 2 to about 4 grams per 
liter of extractant. The first copper-depleted aqueous leaching solution 
that is separated during step (C-1) generally has a copper ion 
concentration in the range of about 0.4 to about 4 grams per liter, and in 
one embodiment about 0.5 to about 2.4 grams per liter. When the leaching 
solution used in step (A) is a sulfuric acid solution, the concentration 
of free sulfuric acid in the first copper-depleted aqueous leaching 
solution separated during (C-1) is generally from about 5 to about 50 
grams per liter, and in one embodiment about 5 to about 30 grams per 
liter, and in one embodiment about 10 to about 30 grams per liter. When 
the leaching solution used in (A) is an ammonia solution, the 
concentration of free ammonia in the first copper-depleted aqueous 
leaching solution separated during step (C-1) is generally from about 10 
to about 130 grams per liter, and in one embodiment about 30 to about 90 
grams per liter. 
Step (B-2) involves contacting the first copper-depleted aqueous leaching 
solution separated during step (C-1) with an effective amount of at least 
one copper-depleted extractant from step (E) to transfer copper ions from 
said first copper-depleted aqueous leaching solution to said 
copper-depleted extractant to form a copper-bearing extractant and a 
second copper-depleted aqueous leaching solution. Step (C-2) involves 
separating the copper-bearing extractant formed during step (B-2) from the 
second copper-depleted aqueous leaching solution formed during step (B-2). 
The copper-bearing extractant that is separated during step (C-2) 
generally has a concentration of copper in the range of about 0.4 to about 
4 grams per liter of extractant, and in one embodiment about 1 to about 
2.4 grams per liter of extractant. The second copper-depleted aqueous 
leaching solution that is separated during step (C-2) generally has a 
copper ion concentration in the range of about 0.01 to about 0.8 grams per 
liter, and in one embodiment about 0.04 to about 0.2 grams per liter. When 
the leaching solution used in step (A) is a sulfuric acid solution, the 
concentration of free sulfuric acid in the second copper-depleted aqueous 
leaching solution separated during step (C-2) is generally from about 5 to 
about 50 grams per liter, and in one embodiment about 5 to about 40 grams 
per liter, and in one embodiment about 10 to about 30 grams per liter. 
When the leaching solution used in step (A) is an ammonia solution, the 
concentration of free ammonia in the second copper-depleted aqueous 
leaching solution separated during step (C-2) is generally from about 10 
to about 130 grams per liter, and in one embodiment about 30 to about 90 
grams per liter. 
The stripping solution used in step (D) of the inventive process is a 
sulfuric acid solution which has a free sulfuric acid concentration 
generally in the range of about 80 to about 300 grams per liter. In one 
embodiment, the free sulfuric acid concentration of the stripping solution 
used in (D) is about 100 to about 200 grams per liter, and in one 
embodiment about 150 to about 200 grams per liter. 
The electrodeposition step (F) involves advancing the copper-rich stripping 
solution from step (E) into an electroforming cell and electrodepositing 
copper metal powder on the cathodes in the cell. The copper-rich stripping 
solution treated in the electroforming cell can be referred to as either a 
copper-rich stripping solution or an electrolyte solution. In one 
embodiment, this electrolyte solution is subjected to a purification or 
filtering process prior to entering the cell. The cell is operated in the 
same manner as the electroforming cell discussed above under the subtitle 
"Electrodeposition Process" with the result being the formation of the 
desired copper powder on the cathodes of such cell. The copper powder can 
be separated from the cathodes, and then washed and dried using the 
techniques discussed above. 
The process will now be described with reference to FIG. 2, which is a flow 
sheet illustrating a solvent-extraction, electrodeposition process for 
making the inventive copper powder. In this process copper is extracted 
from copper leach dump 200 and treated in accordance with steps of the 
inventive process to produce the copper powder 152. The process involves 
the use of settlers 202, 204 and 206, collection pond 208, mixers 210, 212 
and 214, vessel 101, electroforming cell 106, filters 102, 104 and 216, 
holding vessel 108, centrifuge 110, drier 112, agglomerate breaker 114, 
screens 116, and storage hoppers 118, 120 and 122. In this embodiment, 
step (A) of the inventive process is conducted at the leach dump 200. 
Steps (B) and (C) are conducted in two stages using mixers 210 and 212, 
and settlers 202 and 204. Steps (D) and (E) are conducted using mixer 214 
and settler 206. Steps (F) and (G) are conducted using electroforming cell 
106. 
An aqueous leach solution from line 220 is sprayed on the surface of leach 
dump 200. The leach solution is a sulfuric acid solution having a free 
sulfuric acid concentration generally in the range of about 5 to about 50, 
and in one embodiment about 5 to about 40, and in one embodiment about 10 
to about 30 grams per liter. The leach solution percolates down through 
the dump and extracts copper from the ore. The leach solution flows 
through dump space 222 as a copper-rich aqueous leach solution (sometimes 
referred to as a pregnant leach solution), and through line 224 into 
collection pond 208. The leach solution is pumped from collection pond 208 
through line 226 to mixer 212. The copper-rich leach solution that is 
pumped to mixer 212 has a copper ion concentration generally in the range 
of about 0.4 to about 5, and in one embodiment about 0.4 to about 3 grams 
per liter; and a free sulfuric acid concentration generally in the range 
of about 5 to about 30, and in one embodiment about 10 to about 20 grams 
per liter. In mixer 212, the copper-rich aqueous leach solution is mixed 
with a copper-bearing organic solution which is pumped into mixer 212 
through line 228 from weir 230 of settler 204. The concentration of copper 
in the copper-bearing organic solution that is added to mixer 212 is 
generally from about 0.4 to about 4 grams of copper per liter of 
extractant in the organic solution, and in one embodiment about 1 to about 
2.4 grams of copper per liter of extractant in the organic solution. 
During the mixing in mixer 212, an organic phase and an aqueous phase form 
and intermix. Copper ions transfer from the aqueous phase to the organic 
phase. The mixture is pumped from mixer 212 through line 232 to settler 
202. In settler 202, the aqueous phase and organic phase separate with the 
organic phase forming the top layer and the aqueous phase forming the 
bottom layer. The organic phase collects in weir 234 and is pumped through 
line 236 to mixer 214. This organic phase is a copper-rich organic 
solution (which can be referred to as a loaded organic). This copper-rich 
organic solution generally has a copper concentration in the range of 
about 1 to about 6 grams of copper per liter of extractant in the organic 
solution, and in one embodiment about 2 to about 4 grams of copper per 
liter of extractant in the organic solution. 
The copper-rich organic solution is mixed in mixer 214 with a 
copper-depleted stripping solution. The copper-depleted stripping solution 
(which can be referred to as a lean electrolyte) is produced in the 
electroforming cell 106 and is pumped from the cell 106 through lines 237 
and 238 to mixer 214. This copper-depleted stripping solution generally 
has a free sulfuric acid concentration in the range of about 80 to about 
300, and in one embodiment about 150 to about 200 grams per liter; and a 
copper ion concentration in the range of generally about 2 to about 5, and 
in one embodiment about 2 to about 4 grams per liter. Fresh stripping 
solution make-up can be added to line 238 through line 240. The 
copper-rich organic solution and copper-depleted stripping solution are 
mixed in mixer 214 with the result being the formation of an organic phase 
intermixed with an aqueous phase. Copper ions transfer from the organic 
phase to the aqueous phase. The mixture is pumped from mixer 214 through 
line 242 to settler 206. In settler 206, the organic phase separates from 
the aqueous phase with the organic phase collecting in weir 244. This 
organic phase is a copper-depleted organic solution (which is sometimes 
referred to as a barren organic). This copper-depleted organic solution 
generally has a copper concentration in the range of about 0.5 to about 2 
grams per liter of extractant in the organic solution, and in one 
embodiment about 0.9 to about 1.5 grams per liter of extractant in the 
organic solution. The copper depleted organic solution is pumped from 
settler 206 through line 246 to mixer 210. Fresh organic solution make-up 
can be added to line 246 through line 248. 
Copper-containing aqueous leach solution is pumped from settler 202 through 
line 250 to mixer 210. This copper-containing aqueous leach solution has a 
copper ion concentration generally in the range of about 0.4 to about 4, 
and in one embodiment about 0.5 to about 2.4 grams per liter; and a free 
sulfuric acid concentration generally in the range of about 5 to about 50, 
and in one embodiment about 5 to about 30, and in one embodiment about 10 
to about 20 grams per liter. In mixer 210, an organic phase and aqueous 
phase form, intermix and copper ions transfer from the aqueous phase to 
the organic phase. The mixture is pumped through line 252 to settler 204. 
In settler 204, the organic phase separates from the aqueous phase with 
the organic phase collecting in weir 230. This organic phase, which is a 
copper-containing organic solution, is pumped from settler 204 through 
line 228 to mixer 212. This copper-containing organic solution has a 
copper concentration generally in the range of about 0.5 to about 4 grams 
per liter of extractant in the organic solution, and in one embodiment 
about 1 to about 2.4 grams per liter of extractant in the organic 
solution. The aqueous phase in settler 204 is a copper-depleted aqueous 
leaching solution which is pumped through line 220, to the leach dump 200. 
Fresh leaching solution make-up can be added to line 220 from line 254. 
The aqueous phase which separates out in settler 206 is a copper-rich 
stripping solution. This copper-rich stripping solution has a copper ion 
concentration generally in the range of about 5 to about 15 grams per 
liter, and in one embodiment about 7 to about 10 grams per liter; and a 
free sulfuric acid concentration generally in the range of about 50 to 
about 200, and in one embodiment about 150 to about 200 grams per liter. 
It is pumped from settler 206 through line 260 to filter 216 and from 
filter 216 through line 262 and then either: through line 264 to 
electroforming cell 106; or through line 140 to filter 104 and from filter 
104 through line 142 to vessel 101. Filter 216 can be by-passed through 
line 217. Similarly, filter 104 can be by-passed through line 144. The 
copper-rich stripping solution entering electroforming cell 106 or vessel 
101 can be referred to as electrolyte solution 130. If the composition of 
the electrolyte solution 130 requires adjustment (e.g., increase or 
decrease in copper ion concentration, etc.) the electrolyte solution is 
advanced to vessel 101 prior to being advanced to electroforming cell 106. 
If no adjustment in the composition of the electrolyte solution is 
required, the electrolyte solution is advanced directly to electroforming 
cell 106. In electroforming cell 106, the electrolyte solution 130 flows 
between anodes 126 and cathodes 128. When voltage is applied between the 
anodes 126 and cathodes 128, electrodeposition of copper powder 152 on 
each side of the cathodes 128 occurs. 
In electroforming cell 106, electrolyte solution 130 is converted to a 
copper-depleted electrolyte solution and is withdrawn from cell 106 
through line 237. The copper-depleted electrolyte solution in line 237 has 
a copper ion concentration generally in the range of about 2 to about 5 
grams per liter, and in one embodiment about 2 to about 4 grams per liter; 
and a free sulfuric acid concentration generally in the range of about 80 
to about 300 grams per liter, and in one embodiment about 150 to about 200 
grams per liter. This copper-depleted electrolyte solution is either: (1) 
pumped through lines 237 and 140 to filter 104 (which optionally can be 
by-passed through line 144) and from filter 104 (or line 144) to line 142, 
through line 142 to vessel 101, and from vessel 101 through line 146 to 
filter 102, through filter 102 (which can be by-passed through line 150) 
to line 148 and through line 148 back to cell 106; or (2) pumped through 
line 237 to line 238 and through line 238 to mixer 214 as the 
copper-depleted stripping solution. Optionally, additional copper 
feedstock as indicated by directional arrow 131, sulfuric acid as 
indicated by directional arrow 132, chloride ions as indicated by 
directional arrow 133, or dilution water as indicated by directional arrow 
134, can be added to the electrolyte solution in vessel 101. The 
additional copper feedstock entering vessel 101, can be in any 
conventional form which includes copper shot, scrap copper metal, scrap 
copper wire, recycled copper, cupric oxide, cuprous oxide, and the like. 
In one embodiment, the copper feedstock entering vessel 101 is initially 
dissolved in sulfuric acid in a separate vessel prior to being added to 
vessel 101. Also, impurities may be removed from the electrolyte solution 
130 using either or both of filters 102 and 104. Electrolyte solution 130 
recycled from electroforming cell 106 also enters vessel 101 through line 
142. Spent electrolyte from cell 106 may be advanced to vessel 101 through 
lines 154 and 156. The temperature of the electrolyte solution 130 in 
vessel 101 is typically in the range of about 15.degree. C. to about 
40.degree. C., and in one embodiment about 20.degree. C. to about 
30.degree. C. The electrolyte solution 130 is advanced from vessel 101 to 
vessel 124 through lines 146 and 148. The electrolyte solution 130 may be 
filtered in filter 102 prior to entering vessel 124 or, alternatively, it 
may by-pass filter 102 through line 150. 
The electrolyte solution 130 that is treated in the electroforming cell 106 
has a free sulfuric acid concentration generally in the range of about 100 
to about 200 grams per liter, and in one embodiment about 120 to about 190 
grams per liter, and in one embodiment about 140 to about 185 grams per 
liter. The copper ion concentration is critical and is in the range of 
about 2 to about 7 grams per liter, and in one embodiment about 3 to about 
6 grams per liter, and in one embodiment about 5 grams per liter. The free 
chloride ion concentration in the electrolyte solution is critical and is 
in the range of about 8 ppm to about 20 ppm, and in one embodiment about 8 
ppm to about 15 ppm, and in one embodiment about 8 ppm to about 12 ppm, 
and in one embodiment about 10 ppm. The impurity level is critical and is 
at a level of no more than about 1.0 gram per liter, and in one embodiment 
no more than about 0.6 gram per liter, and in one embodiment no more than 
about 0.1 gram per liter. The temperature of the electrolyte solution in 
electroforming cell 106 is in the range of about 15.degree. C. to about 
35.degree. C., and in one embodiment about 20.degree. C. to about 
30.degree. C. 
The flow rate of the electrolyte solution through the electroforming cell 
106 is at a rate in the range of about 0.01 to about 0.3 gpm/csa, and in 
one embodiment about 0.1 to about 0.2 gpm/csa. The electrolyte solution 
130 flows between the anodes 126 and cathodes 128. A voltage is applied 
between anodes 126 and cathodes 128 to effect electrodeposition of the 
copper powder 152 on to the cathodes 128. In one embodiment, the current 
that is used is a direct current, and in one embodiment it is an 
alternating current with a direct current bias. The current density is in 
the range of about 80 to about 120 ASP, and in one embodiment about 90 to 
about 110 ASF, and in one embodiment about 100 ASF. Electrodeposition of 
copper powder 152 on cathodes 128 is continued for about 1 to about 5 
hours, and in one embodiment about 1 to about 3 hours, and in one 
embodiment about 1.5 to about 2.5 hours. Electrodeposition is then 
discontinued. Spent electrolyte solution 130 is drained from vessel 124 
and advanced to vessel 101 through lines 154 and 156. The copper powder 
152 is separated from the cathodes 128 by spraying electrolyte on to the 
cathode resulting in the formation of a slurry 158 in the lower cone 
shaped section 160 of vessel 124. The slurry 158 is advanced from vessel 
124 to vessel 108 through lines 154 and 162. The slurry 158 is then 
advanced from vessel 108 to centrifuge 110 through line 164. In centrifuge 
110, liquid effluent is separated from the copper powder and exits 
centrifuge 110 through line 169 and is either recycled to vessel 108 
through line 170, or removed through line 172 where it is discarded or 
subjected to further processing. In one embodiment, an antioxidant is 
added to the powder in the centrifuge as indicated by directional arrow 
166. In one embodiment, a stabilizing agent is added to the powder in the 
centrifuge as indicated by directional arrow 168. In one embodiment, the 
antioxidant and stabilizing agent are added to the powder in the 
centrifuge in sequential order with the antioxidant preceding the 
stabilizing agent. Alternatively, the antioxidant and/or stabilizing agent 
can be added to the slurry 158 in vessel 108. When the antioxidant and/or 
stabilizing agent is added to the powder in centrifuge 110, the centrifuge 
is rotated at a sufficient rate to place a centrifugal force of about 2 to 
about 750 g's on its contents, and in one embodiment about 10 to about 200 
g's, and in one embodiment about 10 to about 75 g's, and in one embodiment 
about 10 to about 20 g's. The centrifuge is rotated until the pH of the 
effluent is in the range of about 7 to about 14, and in one embodiment 
about 7 to about 11, and in one embodiment about 9. The rotation rate of 
the centrifuge is then increased to dewater the copper powder. During this 
step, the rotation rate of the centrige is increased to a sufficient level 
to place a centrifugal force on its contents in the range of about 200 to 
about 750 g's, and in one embodiment about 500 to about 700 g's, and in 
one embodiment about 650 to about 700 g's. The copper powder remaining in 
the centrifuge 110 after dewatering is advanced to continuous belt 171 
which conveys the powder through drier 112. Moisture is removed from the 
copper powder in drier 112 as indicated by directional arrow 173. The 
dried copper powder exits drier 112 and enters agglomerate breaker 114 
wherein agglomerates that form during drying are broken. The powder is 
advanced from agglomerate breaker 114 to screens 116 wherein the copper 
powder is separated into desired screen fractions and then advanced to 
storage hoppers 118, 120 and 122. 
The foregoing process can be conducted on a continuous basis or a batch 
basis. In one embodiment, the operation of the electroforming cell is 
conducted on a continuous basis, and the operation of the centrifuge is 
conducted on a batch basis. 
EXAMPLE 4 
Copper powder 152 is made using the process illustrated in FIG. 2. The 
aqueous leaching solution sprayed on leach dump 200 from line 220 is a 
sulfuric acid solution having a sulfuric acid concentration of 20 grams 
per liter. The copper-rich aqueous leach solution that is pumped to mixer 
212 through line 226 has a copper ion concentration of 1.8 grams per liter 
and a free sulfuric acid concentration of 12 grams per liter. The organic 
solution is a 7% by weight solution of LIX 984 in SX-7. The concentration 
of copper in, the copper-bearing organic solution that is added to mixer 
212 from settler 204 has a copper concentration of 1.95 grams per liter. 
The copper-rich organic solution that is pumped to mixer 214 from settler 
202 has a copper concentration of 3 grams per liter of LIX 984. The 
copper-depleted stripping solution added to mixer 214 from line 238 has a 
free sulfuric acid concentration of 175 grams per liter and a copper ion 
concentration of 4 grams per liter. The copper-depleted organic solution 
that is pumped from settler 206 to mixer 210 has a copper concentration of 
1.25 grams per liter of LIX 984. The copper-containing aqueous leach 
solution pumped from settler 202 to mixer 210 has a copper ion 
concentration of 0.8 grams per liter and a free sulfuric acid 
concentration of 12 grams per liter. The copper-depleted aqueous solution 
pumped from settler 204 through line 220 has a copper concentration of 
0.15 grams per liter and a free sulfuric acid concentration of 12 grams 
per liter. The copper-rich stripping solution taken from settler 206 has a 
copper ion concentration of 7 grams per liter and a free sulfuric acid 
concentration of 175 grams per liter. This copper-rich stripping solution 
is advanced to vessel 101 wherein the composition of such solution is 
adjusted to provide a copper ion concentration of 5 grams per liter, a 
free sulfuric acid concentration of 175 grams per liter, and a free 
chloride ion concentration of 10 ppm. The copper-rich stripping solution 
(which can be referred as electrolyte 130) is advance to electroforming 
cell 106. The temperature of the electrolyte solution in cell 106 is 
maintained at 24-27.degree. C. The current density is 100 ASF. The cathode 
material of construction is titanium. The anodes are dimensionally stable 
anodes constructed of titanium coated with iridium oxide. The electrolyte 
flows through the cell 106 at a rate of 0.17 gpm/csa. The plating time is 
three hours. The copper powder formed on the cathodes is separated from 
the cathodes by spraying electrolyte on to the powder and the cathodes 
with the result being the formation of a slurring containing the powder. 
The slurry is advanced to vessel 108 and from there to centrifuge 110. A 
solution of ammonium hydroxide having a pH of 10 is added to the powder in 
the centrifuge. The ratio of ammonium hydroxide solution to copper powder 
is 5 gallons of solution per pound of powder. The centrifuge is rotated at 
a sufficient rate to place a centrifugal force of 16 g's on its contents 
until two minutes after the effluent from the centrifuge attains a pH of 
9. A stabilizing agent consisting of an aqueous solution of benzotriazole 
at a concentration of 20 ppm and POLY-TERGENT S-505LF at a concentration 
of 200 ppm is then added. The ratio of stabilizing agent to powder is two 
gallons of stabilizing agent per pound of copper powder. The centrifuge is 
rotated at a sufficient rate to place a centrifugal force of 16 g's on its 
contents until two minutes after the effluent from the centrifuge attains 
a pH of 9. The rotation rate of the centrifuge is increased to a 
sufficient level to place a centrifugal force of 674 g's on the contents 
of the centrifuge with the result being a dewatering of the copper powder. 
The copper powder remaining in the centrifuge 110 after dewatering is 
advanced to continuous belt 171 which conveys the powder through drier 
112. Moisture is removed form the copper powder in drier 112 as indicated 
by directional arrow 173. The dried copper powder exits drier 112 and 
enters agglomerate breaker 114 wherein agglomerates that formed during 
drying are broken. The powder is advanced from agglomerate breaker 114 to 
screens 116 wherein the copper powder is separated into desired screen 
fractions and then advanced to storage hoppers 118, 120 and 122. 
While the invention has been explained in relation to its preferred 
embodiments, it is to be understood that various modifications thereof 
will become apparent to those skilled in the art upon reading the 
specification. Therefore, it is to be understood that the invention 
disclosed herein is intended to cover such modifications as fall within 
the scope of the appended claims.