US1808547A

US1808547A - Copper extraction process

Info

Publication number: US1808547A
Application number: US159671A
Authority: US
Inventors: William E Greenawalt
Original assignee: Individual
Current assignee: Individual
Priority date: 1927-01-07
Filing date: 1927-01-07
Publication date: 1931-06-02
Anticipated expiration: 1948-06-02

Description

June 2, 1931. w. E. GREENAWALT ,5

COPPER EXTRACTION PROCESS Original Filed Jan. 7, 1927 Con centrator Tallrgg Hlgh Gra -c Low Grade Concentrate Concencxafe Roasfiing Furnace De-w'atemg Ta nk U mace CuO FulAcId Copper S01.

Foul 61150 601. Storage Tank.

Regenerated. AclcL Solutlon Regcnerafed. Acid Soluflori I 3 a a R 4'3 E E 9 0 E E 0 u c w a 9 6 Q Q a 3 a u '8 U) .5 .46 5 Le W" C 0 1 S QMJ 11 Cus fig Gus A :8 1

Excess c1d cus Solofion.

Impurc Copper L Lean Copper Soluhon wastesoFf C INVBNTQR C 5 Maw/gammy,

as porphyry, or disseminated deposits. It will be understood, however, that the process is not particularly limited to the percentage of copper in the high grade concentrate, but that the higher the grade of the concentrate, the better the process can be operated, as a whole.

Having made the separation of the mineral from the gangue and divided the mineral into a relatively small amount of high grade concentrate and a relatively large amount of low grade concentrate, the method of procedure is as follows,'reference may be made to the accompanying flow sheet of the process, in which it is shown in diagrammatic plan.

The relatively small amount of hi h grade concentrate, which according to t e specific case assumed for illustration purposes, will consist of 1.5 tons of 50% copper concentrate per 100 tons of originalore, is roasted so as to make as much of the copper Water soluble as practical and a high percentage soluble in dilute acid. By careful roasting, from 80% to 85%. of the copper can be made water solubleand from 85% to 97% acid soluble.

vWhen copper ore or concentrate is roasted so as to make a large portion of the copper water soluble, some iron is also made soluble, but, the amount of water soluble iron is small as. compared with the acid soluble iron.

The roasted high grade concentrate is transferred to leaching tank No. 1, where it is leached, preferably first with water and then with dilute acid, although the acid leach may attimes be dispensed with to advantage, especially when the water soluble copper is exceptionally high. The roasted high grade concentrate is;- leached with water or with very dilute acid, which will extract from 80% to 85% of the copper. The resulting copper sulphate solution will be quite pure, although it will contain small amounts of iron and other impurities, but not in suflicient amounts to seriously affect the subsequent electrodeposition of the copper.

The copper solution flows from the leaching tank No. 1 into the settler No. 1. This settler may also act as a storage tank. It may also act as a reducer for ferric iron, when the solution is treated with copper sulphide or sulphur dioxide. High grade 7 copper sulphide for this purpose may be obtained from the original ore, by fusion, asa high grade concentrate, or as Cuspreclpitate obtained from treating lean and foul copper'solutions with hydrogen sulphide.

The copper solution flows into the copper tanks No. 1, where the copper is deposited as the electrolytic metal of greatpurity, with the simultaneous regeneration of acid. Owing to thesmall amount of injurious impurities in the electrolyte, the solution can be fairly impoverished in copper and regenerated in acid. It may then be transferred to the low grade concentrate leaching and electrolytic circuit. A portion .of it may be returned to the roasted high grade concentrate leaching tank No. 1. If the solution issues from the leaching tank No. 1, containing, say 8% or 10% copper, and containing only a small amount of iron, it is quite practical to impoverish the solution down to about 2% copper, with a very high ampere efficiency. It is preferred to deposit most of the copper in the copper tanks No. 1, from a rich copper solution, which will result in the best possible copper and the highest ampere efliciency obtainable under the conditions, andthen pass the impoverished solution to copper tanks No. 2, where the copper may be reduced to the desired-extent, say to 1% or less. This solution, low in copper and high in acid, is then passed to the low grade concentrate leaching and electrolytic circuit. V

The relatively large amount of low grade concentrate, which according to the specific case assumed for illustration purposes will consist of 8.5 tons of 6.2% copper concentrate or 100 tons of original 'ore, is roasted so as to make as much copper water soluble as practical, and a high percentage soluble in dilute acid. From to of the copper can be made water soluble by careful roasting, and from 85% to 97% can be made acid soluble. v

The roasted low grade concentrate is, preferably, first leached with water or with a very dilute acid solution, in leaching tank No. 2, and the rich water soluble copper solution is flowed into the high grade concen-v trate copper solution. If, however, there should be more iron in the water soluble cop per solution than desired, the solution may be treated with the high grade copper oxide, obtained from roasting the high grade copper concentrate. By using the water soluble copper solution from the low grade concentrate as the head solution for leaching the high grade concentrate there can be obtained a veryrichand a quite pure neutral or nearly neutral copper sulphate solution, and the amountof water used will be reduced to a minimum. With care in leaching, a large portion of the iron may be precipitated from the water soluble copper solution-with the roasted high grade copper concentrate. The water soluble copper solution obtained by first leaching the roasted low grade concentrate and then the roasted high grade concentrate, is then electrolyzed to deposit the copper and regenerate acid, as described for the co per sulphate solution 7 obtained by leaching the high grade concentrate. Copper sulphate is quite soluble in water. At 70-deg. (3., which would be a fair temper ture of the water or very dilute acid in leaching roasted concentrate, a water saturated solution of copper sulphate will contam-12.93% copper, and there should be no diiiiculty in keeping the head solution tor copper deposition at from 8% to 10% copper, in leaching the hot roasted concentrate asdescribed. Such a rich copper solution is not necessary, nor may it be desirable, but it is easily obtainable, if desired.

The regenerated acid solution, resulting from the deposition of the copper from the relatively pure water soluble copper solution, is quite free from injurious impurities. A portion ofthis acid solution may be added to the water, for the water soluble copper solution in amount so that the acid will be quickly neutralized by the copper in the roasted concentrate, which is insoluble in water. This copper will be mostly in the formoi oxide. Iron is not readily soluble in a very weak acid solution, but, at the same time, the copper-oxide in the roasted concentrate will be quickly dissolved in a weak acid solution. It is practical, therefore, to leach out the larger portion of the readily soluble oxide of copper with a very weak acid solution, without appreciably increasing the iron content of the solution, and, as already indicated, if the iron occurs in the solution in undesirable amounts, it can easily be precipitated from the neutral solution with an excess of concentratedcopper oxide. It should be practical, in this way, to extract 80% of the copper from the roasted low grade concentrate and 795% of the copper from the roasted high grade concentrate, without appreciably fouling the solution.

lV-ash water, or lean water soluble'copper solution, resulting from leaching of one charge of either roasted high grade or roasted low grade concentrate may be used as the head solution for another charge.

It will be observed. that, water leaching, 01' very dilute acid leaching, so as to obtain neutral, or practically neutral solutions, an amount of water, or regenerated acid solution, is discarded, equal to the amount of water added, and that in this way the in jurious impurities in the rich, or water soluble copper solution may always be maintained so low as not to give :any serious leaching or electrolytic diiiiculties.

Afterthe low grade concentrate has been leached with water .or with very dilute acid solution as'described, it is leached with the regenerated acid solution obtained'irom depositing the copper .from the water soluble copper solution. This strong acid soluble copper solution will usually be quite impure. It will contain the relatively small amount of impurity from :the water soluble copper I leaching andelectrolytic circuit,.and the relatively large amount of impurity resulting from' leaching the roasted low grade concentrate with the relatively strong acid solution.- The strong acid solution will dissolve the copper in the roasted low grade concentrate which Was'not soluble in water or in very dilute acid. If the total extraction is 95%, the leached roasted low grade concentrate residue will contain about;31% copper, based on the weightof the original ore.

The impure copper solution, containing salts of iron and other impurities, flows into the settler, or reducer No. 2, where it maybe clarified and'treated with copper sulphide' to reduce ferric iron to ferrous iron. The solution then 'fiows into the SU reducer, and from the reducer into the storage tank, a'nd from the storage tank into the copper tanks No. 3, where a portion of the copper is deposited and acid and ferric iron regenerated. A portion of the electrolyzed solution is returned to the SO reducer No. 1, while another portion,the advance fiowpasses to the S0 reducer No. 2, where the ferric'iron is reduced, and the-solutiontnen flows into the-copper tanks Nomi, where the solution is impoverished 1n copper to the desired extent with the simultaneous regeneration of acid I p and ferric iron. A portion of this solution is returned to the S0 reducer No. 2, another portion is returned to the leaching tank No. 2 to pass through another cycle, while another portion'-the advance low-may be used to dissolve the copper in its oxide (including carbonate and silicate) combinations, in the concentrator tailing or from the originalore.

i f the ore is mixed, that is tosay contains oxides and sulphides, and the concentrator tailing contains enough oxidized "601036? to make its recovery profitable, the concentrator tailing is thickened or dewatered in the dewatering tank. \Vith suitable apparatus the water in the concentrator tailing may be reduced to as low as or of the weight of the tailing; The excess Water maybe returned to the concentrator.

The dewatered, or thickened tailing, containing from 25% to water, is transferred from the dewatering tank to the leaching tank No. 3 and treated with the excess regenerated 'acid solution obtained from electrolyzing the copper solutions obtained from leaching the roasted high grade and low grade concentrate. The/partly dewatered flotation oxidized tailing will usually be in the formof an easy flowing thickened pulp Since the larger portion of the copper in both the roasted high grade and low grade concentrate is water soluble, and since an equivalent of acid is regenerated from the water soluble copper, as well as a certain amount from the acid soluble. copper, the copper in the original ore, in the form of oxide (including carbonate), can be leached out without any acid expense. If, for example, of the copper in the roasted concentrate is Water soluble, or about 2040 pounds, of the total 2550 pounds in the concentrate, an abundance of acid will ordinarily be regenerated to dissolve, say, 70% of the assumed 0.25% of the oxidized copper in the tailing, or about 810 pounds. That is to say, there'will be about seven times as much acid regenerated in depositing about 2550 pounds of copper obtained from the concentrate, as that theoretically required to dissolve the 310 pounds of copper in the tailing, and this will provide an abundance of excess acid to react with the base elements in the tailing. The regenerated acid solution, diluted with from 25% to 100% water remaining in the tailing, will still be strong enough to dissolve the oxidized copper in the tailing in a very short time, in leaching tank No. 3. The resulting foul copper solution flows from the leaching tank No. 3 into the foul solution storage tank, and from the storage into the S0 reducer N o. 3, and from the reducer to the copper tanks No. 5, where a portion of the copper is deposited and acid and ferric iron are regenerated. A portion of the regenerated acid solution, or all of it, is returned to the leaching tank N o. 3, to

pass through another cycle. The lean and foul solution, resulting from leaching the concentrator tailing, or resulting from leaching the roasted low grade concentrate if the concentrator tailing is not leached, is precipitated with hydrogen sulphide in the H S precipitator. The precipitate and foul barren solution flow into the CuS separator, where the C118 is separated from the solution. The barren solution may be wasted, or a portion may be returned to the tailing leaching tank No. 3, if the acid consumption of the tailing is excessive. The CuS may conveniently be transferred to the settlers No.1 and No. 2, where the OuS reacts with ferric iron to reduce it to the ferrous con dition while an equivalent of copper goes into solution. The CuS precipitate may in i this way be converted into the electrolytic copper, while at the same time acting as an effective reducing agent for ferric iron in the electrolyte. The hydrogen sulphide may beconveniently generated in the H 8 generator by the action of FeS with acid, and the acid used may conveniently be that generated in the deposition of the copper from the rich copper solution obtained from leaching the roasted high grade concentrate. If desired, the richer andtpurer portion of the copper solution from leaching tank No. 3 may be flowed into the, low grade concentrate leaching and electrolytic circuit.

The cathodes from copper tanks No. 4 and No. 5 may be too impure for good cathode copper; in such cases the cathodes are transferred to copper tanks No. 1, where they are electrolytically refined with the relatively pure copper solution from the high grade concentrate as the electrolyte.

The water leached high grade concentrate residue in leaching tank N o. 1 may be leached with a strong regenerated acid solution to extract the remaining acid soluble copper. This strong acid solution will also dissolve a considerableamount of acid soluble iron, including that precipitated or hydrolyzed in the process of extracting the water soluble copper. This impure acid soluble copper solution is transferred to the low grade concentrate leaching and electrolytic circuit, preferably by adding it to the water leached low grade concentrate residue in leaching tank No. 2, and then depositing the copper from the resulting impure copper solution, as already described and as set forth more in detail in my Patent No. 1,483,056, Feb. 5, 1924. If the extraction of the copper from the high grade concentrate by water leaching is sufliciently high, acid leaching may be dispensed with.

The residue from leaching the high grade concentrate, containing rare or precious metals if present, is smelted, preferably in an electric furnace to concentrate the residual copper and the rare or precious metals into impure metallic copper, and then this impure copper is electrolytically refined with the relatively pure Water soluble copper solution as the electrolyte. The amount of the leached high grade concentrate residue will usually be quite small and can be easily and conveniently smelted in an electric furnace. If, however, for any reason there is a considerable amount of the high grade concentrate residue, as there would be in large installations or if'the concentrate is of a lower grade than that assumed for the high grade concentrate, it may be desirable to first smelt the residue in an ordinary blast furnace to slag off the greater portion of the impurities, so as to produce a high grade copper matte or copper sulphide, and the copper matte or copper sulphide can then be reduced to the impure metallic copper in the electric furnace.

If the extraction of the copper from the roasted high grade concentrate is and the loss of weight by roasting and leaching is 60%, the high grade concentrate residue will weigh about 0.6 ton and will assay about 6.25% copper, and it will contain all of the rare or precious metals.. If the amount of ore treated is large, so that preliminary blast furnace smelting is desirable,

the leached high grade concentrateresidue, preferably without washing or excessive washing, is treated with an alkali, such. as caustic lime, to destroy, the acid. andprecipitate the copperasthezhydroxidev Theres idue is then. filtered in. an. ordinary filter, after. which; it. is mixed: with the necessary amount of pyrite, preferably containing, lit.- tle. or no copper but containing rare or precious metals. This mixtureisthen sintered; If it. is desired. to add. the. pyrite direct to the smelting furnaceto save sulphur, carbonac.eous fuel, such. as fine coke, coal, or charcoal,.n1ay be added to the. sin: ter. charge to give the necessary. heat for. sintering. The residue; is then smelted to matte or to. aconcentrated copper sulphide, and the resulting relatively; small, amount of. copper sulphideis introducedihot into the electric furnace to be converted into. the impure. copper containing the rare or preciousmetals; In the treatment of-Ithe, matte or concentrated, copper sulphide in the elec tric furnace, the sulphur from. the iron. and from the cupric. sulphide is easily dissoc-i atedor volatilized, b utvpractically a. white heat. is required. to dissociate the copper from the cuprous sulphide. Tov facilitate thereduction of the cupnous sulphide to. metallic copper a. small. amount of. concentrated copper. oxide is added to the. charge in the electric furnace, preferably after the charge has been. reduced to cuprous sulphide. This greatly facilitates: the. reduction. Thev reaction. is Wellknown.' The copper oxide may conveniently be, obtained by roasting high. grade copper concentrate, or. by roasting concentrated copper sulphide.

The slag from the electric furnace, which wilL usually contain considerable, copper, is added to. a. new blast furnace charge. The blast: furnace slag will. usually be very low in, copper and. may bev wasted, but; provision should. always be made so that; there Will be enough copper inthe-leached= residue or in the furnace charge to make a, high. recovery of. the precious metals. I

Thennpure copper from; the electric furnace. is cast intoanodes, and the anodes; are

refined, preferably, in copper tanks- No.v 1-, with. the relatively. pure water soluble leach solution. as the electrolyte. The copper of the anodes will be transferred to the cathe odes as. the pure electrolytic metal, while the rare or precious metals will drop tothe bottom. of the tanks-v as. anode, mud, from which. they maybe recovered.- or separated, in elemental form by any of the: well; known methods.

Part of the copper in copper tanksNo. 4: and No. 5will be in the form of goodcathode plates, but they are likely to be somewhat impure for thebest quality of cathode copper, andpart of the copper in these copper tanks, isflikely to. be. loosely deposited pure.electrolyticfmetal, so that bothsoluble and insoluble anodes, are used in copper tanks No. 1. Copper, isdepos-ited fromfthe solution with. insoluble anodes. The; in? soluble anodes may conveniently be made of antimonial lead, which meets the require, ments. fairly satisfactorily.

The amount .of. impure copper produced by this, process will be quite small, and. the amount, of. copper requiring chemical pre:'

cipitjationcanbereduced to aminiml m. "Of

the approximately. 3,000, pounds. of copper in the original ore, about. can be re covered. direct as the pure electrolytic metal, and of the. remaining 300, pounds. about200. pounds willberecovered as the imp'ureielece trolytic copper which will. require refining preferably as described, and. about 50 pounds will. be recovered. as a. chemical. pre-. cipitate, suchas copper sulphide, which. is also converted, into. the pure. electrolytic metal as described,preferably, byfusin-g it asa reducing agent, for ferric iron.

Copper ores frequently. contain small amounts. of rare or pI6ClO11SjII18tfilS,: which, i'n-the usual. methods of. treatment by solvent processes, might not. be .worth; the extra. step for their recovery. In the present, process the rare or precious metalsv will be 00.11.6811;- trated. by gravity. or flotation: in. about the same proportion. as thecopper, That. is to say, about three. fifths of the total, precious metal content of the. concentratefwilli be in the, high, grade concentrate, and. about two fifths in, the. low grade concentrate, in the case. assumed for illustration. If. the. original, ore, for example, contains20 centsper ton, of; gold and silver recoverable in the concentrate, the total, recoverable value would be $20.00, resulting from the concentration of, tonsof. original. ore, Of't h'is $20.00, three fifths, or $12.00,,W0l11dib6 in the 1.5 tonsof high grade concentrate, and two. fifths, or $8.00', would be. in; the 8.5, tons ofjlow grade concentrate. The low grade concentrate after roasting. and. leaching would. assay about $15.00 recoverableprecious metal value per ton] The. high. grade: cone centrate would, assay about $8.00. per ton. a d af s m ns e ea hinaa ca 9 per ton, assuming a shrinkage'of 60% in wei ht. If the extraction of the copper by leac ing the roasted high grade'concentrate' is 95%, the $20.00 in gold and silver value in the leach residue will be concentrated by smelting into about 75 pounds of impure copper containing the .rare or precious metals. This impure copper is easily and cheaply cast into anodes, and can be easily and cheaply refined electrolytically as described, giving as end products the copper as the electrolytic metal and the gold and silver in elemental form.

In the treatment of the low grade con centrate there will be no difficulty ordinarily in extracting the copper so closely that there will be no trouble in extracting the gold, silver, or other metals from the copper leached residue by cyanidation or chlorination. The value of $1.00 per ton of precious metal in the residue should make such an extraction profitable, but if not, the loss will not be as great as if all of the precious metal content of the ore had to be wasted. The precious metal content of. the high grade concentrate can at least be profitably recovered, even if the original ore assays as low as five or ten cents per ton.

The roasted and copper leached low grade concentrate may be leached with a solvent for the precious metals. The precious metals are precipitatedfrom the leach solution, and the precipitate maybe refined direct, but as the precipitate is likely to contain considerable copper, it is preferred to smelt the precipitate with the high grade concentrate copper leached residue, so as to recov-v er all of the rare or precious metals together by one simple process.

Itwill be observed that the smelting is reduced to a minimum, by this process. Of the ten tons of concentrate, only 1.5 tons are highgrade, in the assumed case, and this 1.5 tons is reduced by roasting and copper leaching to about06 ton; or about 0.5 ton of material would be smelted per 100 tons of original ore, or per 10 tons of concentrate. This amount could be conveniently smelted in a small electric furnace, even for a capacity of 1000 tons of original ore per day. The value of the high grade concentrate may not always be as high as in the assumed case; in that event preliminary blast furnace smelting may be desirable in large installations. 1

It is desirable to extract the copper, as also the precious metals, in the low grade concentrate as completely as possible, since the low grade concentrate leached residue is wasted. With a low grade concentrate this loss will be very small. The extraction of the copper in the high grade concentrate, by leaching, may vary within wide limits, since the copper remaining in the high grade concentrate leached residue is practically all recovered by subsequent smelting. Roasting cannot always be'controlled to get the desired extraction by leaching, and while this may not be embarrassing in roasting the low grade concentrate, it is a serious problem in the treatment of high grade copper concentrate by roasting and leaching, if the leached residue is to be wasted.

Dividing the general concentrate into a high grade and a low grade concentrate for separate parallel treatment results in V at least two distinct advantages; first, it facilitates the recovery of the precious metals, especially in the high grade concentrate if the precious metal content of the original ore is low, and this extra precious metal recovery in the high grade concentrate, without appreciable expense, may be an important factor in determining the general treatment of the ore as also on the profits;

, second, in the roasting and leaching treatment of high grade particles of copper ore, there is likely tobe difficulty ingetting the recovery desired for those particles. If one of the high grade particles is mixed with nine low grade particles, the ten particles will have to be'given the same careful treatinent to get the desired high extraction of the high grade particle as if the high grade particle were treated'alone, and this would be expensive and inconvenient. But if the one high grade particle is separated from the nine low grade particles, the nine low grade particles can be given a quick and cheap treatment, while the more careful treatment would be confined to the one high grade particle. Even if the one high grade particle is given a double treatment to get a very highextraction of the copper or precious metals, the expense would not be appreciably increased in the cost of the treatment of the concentrate, as a whole.

If the low grade roasted copper concentrate is leached with a sulphate solution to extract the copper, the precious metals will remain in the sulphate leached residue. The residue, if leached with a chloride solution, will extract the precious metals and alarge portion of the residual copper. The copper and precious metals may be precipitated from the'resulting chloride solution, preferably as the sulphides, with hydrogen sulphide. The precipitate, whether in the form of sulphide, or in some other form, may be washed to free it from chlorides, and then transferred to the reducers No. 1 and No. 2, where the copper of the precipitate is largely redissolved and is converted intothe electrolytic metal. The residue in the reducers, whether of precipitate, copper concentrate, or, concentrated copper sulphide, is impoverished in copper and enriched in sulphur and the precious metals, and the copper-impoverished residue may be mixed with the leached roasted high grade residue and smelted. It may be desirable at times to heat the copper solution and electrolyte to a higher temperature than that due-tothe chemical reactions of the process to facilitate the re-solution of the copper o1 the precipitate or sulphide concentrate and the reduction of the ferric iron formed by the electrolysis.

This process is a continuation of those describedin my pendin applications, Serial Numbers, 114,477, filed June 8, 1926, and 101,19-l, filed April 10, 1926 (Patent Numbers -1,61 l,670 and 1,614,669, respectively).

I claim:

1. A process comprising, treating copper ore to separate a high grade and a low. grade copper concentrate, separately roasting and leaching the high grade and the low grade concentrate, smelting the leached high grade concentrate residue to concentrate residual metala into impure copper, and electrolytically refining the impure copper with the leach copper solution as-the electrolyte.

2. A process comprising, treating copper ore containing rare or precious metals to separate a high grade and a low grade concentrate, separately roasting and leaching the high grade and the low grade concentrate, smelting the leached high grade concentrate residue to concentrate residual metals into impure copper, and electrolytically refining the impure copper to convert the impure copper into the electrolytic metal and recover the rare or precious metals.

3. A process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, separately roasting and leaching the high grade and. the low grade concentrate, and smelting the leached high grade concentrate residue to recover the residual copper.

4. A process comprising, treating-copper ore containing rare or precious metals to separate a high grade and a low grade concentrate, separately roasting and leaching the high grade and the low grade concentrate, and smelting the high grade concentrate leached residue to recover the rare or precious metals associated with another metal in impure elemental form.

5. A process comprising, treating copper ore containing'rare or precious metals. to separate a high grade and a low grade concentrate, separately roastin and leaching the high grade and the low. grade concentrate, and smelting the high grade concentrate leached residue to. recover the residual metals in a concentrated metal product, and electrolytically refining the concentrated metal product with the copper leach. solution as the electrolyte.

6. A process comprising; treatin copper ore containing rare or precious metals to separate a high grade and a low grade concentrate, separately roasting and leaching the high grade and, the low grade concentrate, and concentrating the residual metal Values in the high grade concentrate residue by fusion.

7. A process comprising, treating copper ore to separate a high-grade and adoW- grade copper concentrate,separately roasting and leaching the high grade and the loW grade concentrate, and electrolyzing the resulting. copper solution from leaching the high grade concentrate partly With soluble anodes and partly with insoluble-anodes.

8. A process comprising, treating copper ore containing precious metals to separate a; high grade and a low gradeconcentrate, separately roasting and leaching the high grade and the low grade concentrate to ere tract the copper, leaching the low grade concentrate copper leached residue to extract the preciousmetals, precipitating the precious metals from the leach solution, adding, the precious metal" precipitate to the high grade concentrate copper leachedresidue, and smelting the high grade concentrate leached residue to: concentrate the residual copper and the precious metals into an impure concentrated copper product.

9. A process comprising, treating copper ore containing precious metals to separate a high grade and a low grade concentrate, separately roasting and leaching the high grade and theloW grade concentrate to extract the copper, leaching the low grade concentrate copper leached residue to extract the precious metals, precipitating the precious metals from the resulting solution, adding the precious metal precipitate to the high grade concentrate copper leached residue, smelting the mixture into an impure concentrated copper product containing the precious metals, and electrolytically refining the impure concentrated copper product to separate the copper and the precious metals.

10. A process comprising, treating copper ore to separate a high grade and a low grade concentrate, separately roasting. the low grade and the high grade concentrate to makeaportion oi the copper'water solule, leaching the roasted low grade concentrate to extract the water soluble copper, leaching the roasted high gradeconcentrate With the Water solulole copper solution obtained from leaching the roasted low grade concentrate, and smelting the high grade concentrate leached residue tov recover the residual copper as, an impure copper concentrated' product.

11. A process comprising, treating copper ore to separate a high grade andalow grade concentrate, separately roasting the low grade and the high grade concentrate to make a portion of the copper Water soluble, leaching the roasted low grade concentrate to extract the Water soluble copper, and

leaching the roasted high grade concentrate with the water soluble copper solution obtained from leaching the roasted low grade concentrate. V

7 12A process comprising, treating copper ore containing precious metals to separate a high grade and a low grade concentrate, separately roasting the high grade and the low grade concentrate to make a portion of the copper water soluble, leaching the roasted low grade concentrate to extract the water soluble copper, leaching the roasted high grade concentrate with the water soluble copper solution obtained from leaching the roasted low grade concentrate, smelting the copper leached high grade concentrate residue to concentrate residual copper and the precious metals into a concentrated copper product, and electrolytically refining the concentrated copper product with the copper leach solution as the electrolyte.

13. A process comprising, treating copper ore containlng rare or precious metals to separate a high grade and a low grade con-. centrate, separately roasting and leaching the high grade and the low grade concentrate, and smelting the high grade concentrate leached residue to recover the residual copper and the rare or precious metals.

1 1. A process comprising, treating copper ore to separate a highgrade and a low grade concentrate, separately roasting the high grade and the low grade concentrate, leaching the low grade concentrate, and leaching the high grade concentrate With the copper solution obtained from leaching the low grade concentrate.

15. A process of treating mixed oxide and sulphide copper ore comprising, concentrating the ore to separate a high grade and a low grade concentrate and a lean oxidized tailing, separately roasting the high grade and the low grade concentrate, leaching the high grade concentrate to extract the copper, electrolyzing the resulting copper solution to deposit the copper and regenerate acid, leaching the low grade concentrate with the regenerated acid solution obtained from leaching the high grade concentrate, electrolyzing the resultingcopper solution to deposit the copper and regenerate acid, and leaching the lean oxidized concentrator tailing with the regenerated acid solution obtained from leaching the low grade concentrate.

16. A process of treating mixed oxide and sulphide copper ore comprising, concentrating the ore to separate a high grade and a low grade concentrate and a lean oxidized tailing, separately roasting and leaching the high grade and the low grade concentrate, electrolyzin'g the resulting copper solutions to deposit the copper and regenerate acid, and leaching the lean oxidized concentrator tailing with the regenerated acid solution.

17 A process of treating copper ore comprising, treating copper ore to separate a high grade and a low grade concentrate, separately roasting and leaching the high grade and the low grade concentrate, electrolyzing the resulting copper solutions to deposit the copper and regenerate acid, leaching oxidized copper ore withthe regenerated acid solution, precipitating the copper from the resulting foul copper solution, and electrolytically converting the impure copper precipitate into the electrolytic metal with the copper leach solution of the concentrate as the electrolyte.

18. A process comprising, treating copper ore to separate a high grade and a low grade concentrate, separately roasting and leaching the high grade and the low grade concentrate to extract a portion of the copper, precipitating the copper from the lean and toulleach solutions, adding the precipitate to the leached high grade copper concentrate residue, and smelting the mixture.

19. A process comprising, treating copper V ore to separate a high grade and a low grade concentrate, separately roasting and leaching the high grade and the low grade concentrate, electrolyzing the resulting copper solution to deposit the copper, and treating the electrolyzed solution with a portion of the unroasted high grade concentrate and again electrolyzing the solution.

20. A process comprising, treating copper ore to separate a-high grade and a loW grade concentrate, separately roasting and leach ing the high grade and the low grade concentrate, electrolyzing the resulting copper solution to deposit the copper, treating the electrolyzed solution with concentrated copper sulphide and again electrolyzing the solution, and maintaining the solution at a temperature above that due to the chemical reactions of the process.

21. vA process comprising, treating copper ore to separate a high grade and a low grade concentrate, separately roasting. and leaching the high grade and the low grade concentrate, electrolyzing the resulting solution to deposit the copper and regenerate acid and ferric iron, treating the electro lyzed solution with concentrated copper sulphide to dissolve the copper of the copper sulphide with the simultaneous reduction of ferric iron to ferrous iron and again electrolyzing the solution, and when the 'concentrated copper sulphide becomes impoverished in copper mixing the resulting residue with the roasted and leached high grade concentrate residue and smelting the mixture.

22. A copper extraction process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, separately roasting the high grade and the low grade concentrate, leaching the roasted concentrate to extract a portion of the copper as a relatively pure and relatively rich copper solution, then leaching the roasted concentrate to extract the remaining copper as a relatively impure copper solution, electrolyzing the relatively pure and relatively rich copper solution partly with soluble anodes in one electrolytic circuit, and separately electrolyzing the relatively impure copper solution with insoluble anodes in another electrolytic circuit.

A copper extraction process comprising, roasting copper concentrate to make a portion of the copper water soluble and a portion acid soluble, leaching the roasted concentrate to extract a portion of the copper as a relatively pure and relatively rich copper solution, then leaching the roasted concentrate to extract the remaining copper as a relatively impure solution, electrolyzing the relatively rich and relatively pure copper solution with soluble anodes in one electrolytic circuit and electrolyzing the relatively impure copper solution with insoluble anodes in another electrolytic circuit.

WILLIAM E. GREENAWALT.