US2260670A - Metallurgical process - Google Patents

Description

c. H. HUMPHRIES 2,260,670

METALLURGICAL PROCESS Oct. 28, 1941.

Filed Jan. 19, 1940 Ore +Au Micelle +X R0 H Tem.400C.

05 e Time-lOfol5min.

Comminuror To 100 Mesh Dilure HCI /4 gel. to lgol. per IOO lb. ore

Agitote until oc'rion ceoses 95%No2 CO3+ 5% D.S.P until pH is ll.51o|3 1 -decon'r orange yellow Aerore 4 16 hrs. then settle unTil llquor slime free 0.5.0., 0.5.0. E8. or S .O.A.

s m .01 to 1% No ON in Solution Aero're 4-!6 hrs.

TONS J Cherry red to Recover Au by P p "q known methods Recover Au by known methods e/zz vezzi or' counties, State of 'Michigan.

Patented Oct. 28, 1941 UNITED STATES PATENT OFFICE METALLURGICAL PROCESS Chad H. Humphries, Winnetka, 111-. Application January 19, 1940, Serial No, 314,669 a 22 Claims.

This invention is concerned with methods of extracting gold from sedimentary or argillaceous rocks or like substances, in which themetal is frequently found in finely divided form.

It has been known that gold is to be found in certain sedimentary rocks,-a typical example being-limestone strata in Alpena andPresque Isle Examination of these ores under high power microscopes does not ordinarily disclose any visible gold particles, and it is inferred that the gold particles are ultra-microscopic and of a size ranging from a few millimicrons to perhaps one micron. These particles are hereinafter referred to as micelle. Priorefforts to extract these micelle from the strata in which they are found through conventional methods have proved futile, although assay smelts at times show substantial values of the precious metal, while identical smelts from comparable samples frequently reveal nothing more than a trace.

Methods for treating gold-bearing rock of this type are disclosed in the following patent and copending application: Henry Jefis and Edward J. Dunn, Patent No.- 2\,193,234 issued March 12,

1940; James J. Bonesteel, Serial No. 276,671, filed May 31, 1939. Each of these methods is concerned with transferring gold micelle from the ore'to a'suspensoid of colloid state in Water, and the tails are rejected when-this has been accomplished. I have found that the tails stillmay contain the major proportion of the values, after the ore has been treated by these methods, and that with proper treatment substantial values can be recovered from the tails through conventional methods.

The principal object of this invention then is to present methods for treating gold-bearing material of the type described in such manner that it is amenable to ordinary methods of capture, such as cyanidization, for. example.

It has been found that the limestone strata bearing the gold micelle have a tendency to be acidic, and likewis,e contain deleterious materials composed principally! of hydrocarbons of the paraffin or olefine series, although for the purpose of applying the herein described processes it is not necessary to define precisely the nature of these inhibiting ingredients. These organic compounds may compose from .3% to .5% of the original aggregate by weight. It has been found, however, that, when such deleterious organic compounds are removed by the methods hereinafter described, the gangue may then be treated through conventional cyanide processes with satisfactory recoveries.

These methodsare diagrammatically shown in the attached flow sheet, in which the symbols utilized have the following significance: X refers to various unknowns, organic and inorganic, D. E. 0. refers to di-ethyl oleate E, S. refers to ethyl stearate D. E. G. refers to di-ethyleneglycol S O. A. refers to sucrose-octa-acetate D. S. P. refers to di-sodium hydrogen phosphate The limestone rock containing the micellic gold particles is first broken into lumps roughly one-half inch in diameter and then subjected to roasting Any of the approved roasters may be used, the principal roasting requirement being an application of a temperature of approximtaely 400 C. for a 10t0 15 minute time interval. The application of the degree of heat for the period specified results in driving off a majority of the organic material, leaving the remainder of the ore relatively in itsprevious chemical condition, although the-lumps of ore may be reduced in the roasting to the form of a powder. Not all of the organic material is released, some free carbon remaining, but most, if not all, of the hydrogen present is driven off. It is to be noted that the heat specified is insufficient to reduce the lime, andthat little, if any, carbon dioxide should be given off during the roasting. j I

Where the limestone rock is still lumpy in form after the roasting is completed, it is desirable to comminute the same to pass 100 mesh or less, which assists the action of the hereafter described reagents.

When the roasting has been completed, the ore is then treated with a very dilute solution of hydrochloric acid, sufficient to react with ap. proximately 1% of its limestone content, Onequarter gallon to one gallon of solution should be used per 100 lbs. of ore. While the hydrochloric acid is working on the limestone, the mixture is agitated, preferably by air, until all action ceases, when the gangue is receptive for the next step in the process. If, however, "the roasting step. has been efficacious in breaking up the organic compounds'the here described treatment with hydrochloric acid may be dispensed with.

While I prefer the preliminary roasting step which has been described, an equivalent is comminuation followed by treatment with hydrochloricacid in water, so, that the hydrochloric acid solution amounts to approximtaely 2% of the entire volume. The mixture should be thoroughly aerated until all action ceases. Nitre cake may be substituted for the hydrochloric acid, the nitre cake added amounting to approximately 244% to 2 of the entire volume. Aeration is the same as with hydrochloric acid. In addition, sulphuric acid may be mentioned as an equivalent for hydrochloric acid.

Whichever of the foregoing preliminary treatments is used, when the step has been completed, a quantity of sodium carbonate is added as a dispersing agent, which tends to disperse the gold micelle into a hydrosol. The quantity of sodium carbonate added must be sufiicient to render the mixture pronouncedly alkaline, with a pH from 11.5 to 13, and to assist the reaction the mixture should be subjected to further agitation, preferably by air, for a period of several hours, after which it is allowed to settle until the top liquor is relatively free from slimes. The reaction of the sodium carbonate plus agitation produces a froth in which all of the residual carbon is carried in a free form. The top liquor has an orange yellow color. In practice, sufiicient sodium carbonate to equal 2% of the entire solution has been found adequate.

In limestone rock which has been treated under this process, iron or its compounds have frequently been found present, and they tend to inhibit the dispersive effect of the sodium carbonate. In addition, it may be impossible to add sufficient sodium carbonate to attain the desired pH of 11.5 to 13. In such cases I have found that the addition of a small quantity of di-sodium hydrogen phosphate, amounting to about 5% of the sodium carbonate employed, will increase the pH or assist in the removal of the contaminating lI'OIl.

Di-sodium hydrogen phosphate may be substituted for sodium carbonate as a dispersing agent, although the cheapness of the sodium carbonate recommends its use where cost is a consideration. Ammonium carbonate and ammonium chloride are other equivalents which may be substituted for sodium carbonate.

The top liquor is then decanted or siphoned from the gangue, where it is ready for additional treatment with a dispersing agent. I prefer to disperse the mixture by adding sufficient diethyl oleate, ethyl stearate, di-ethylene glycol or sucrose-octa-acetate to equal, .01% to .1% of the entire solution. After agitation for a time interval of from 4 to 16 hours, the dispersion is complete, the liquor being characterized by a true colloidal-gold color from cherry red to purple, when, after coagulation of the colloid, the gold is extractable by known methods.

I have found that if much iron is present, the initial color in the second dispersion is rusty brown as a result of partial dispersion of the iron. In counteracting the effect of dispersion of the iron and expediting dispersion of the gold micelle, I have found that the use of sucrose-octa-acetate is especially effective, as it tends to coagulate the iron dispersion, while dispersing the gold.

It is further to be understood that the limestone rock varies in its chemical complexity, and that some one of the organic dispersing agents described will be more effective with one ore than with another. When a new ore presents itself for processing, some experiment with the described dispersing agents is necessary to determine which is the most suitable for the particular ore'which is the subject matter of inquiry. Where sulphur is present in the ore, and sodium poly-sulphides develop as a product of the first dispersion, sucrose-octa-acetate is particularly efficaceous in inhibiting their effects.

Some slimes may be carried in the decantation from the first dispersion to the second, and when they settle out or are captured through filtration, which should precede the coagulation step in recovering the massive gold from the colloid, they may be discarded or added to the original tailings for the hereafter described cyanide leaching process to which the latter are subjected following the first dispersion.

While I believe the foregoing description of the dispersion steps produces the best results, as an alternative, separate dispersions can be dispensed with, and the inorganic and organic dispersing agents can be added simultaneously following the described treatment with hydrochloric acid or nitre cake.

Under this method of procedure, approximately 2% of sodium carbonate and approximately .1% to 1% of one of the described organic dispersing agents may be added, the percentage expressed being of the entire solution. The mixture is agitated, preferably by air, for a substantial period, and then allowed to settle until relatively clear, 18 hours should sufiice, during which the hydrosol', with a characteristic gold colloid color, will form.

After the hereinbefore described pre-treatment of the tails and decantation of the top liquor, following the first dispersion, the tails are now amenable to treatment through recognized cyanide processes. In practice I prefer to use sodium cyanide plus aeration and agitation, all of which steps are well-known in the metallurgical arts.

As an equivalent of cyanidization, the gold may likewise be captured through chlorination, a process which is likewise well-known.

By following the herein described process, it will be found that very substantial values can be recovered from gold-bearing limestone hitherto supposed to have been wholly unamenable to treatment by any commercial process. In numerous tests on limestones from Alpena and Presque Isle Counties in Michigan, I have found an astonishing correlation of the values recovered through dispersion of the top liquor, and the values recovered from the tails by cyanidization after the described pre-treatment of the gangue. Numerous tests on comparable two-pound ore samples have indicated that from 4 to 6 mgm. of gold may be recovered through dispersion of the top liquor, and from 15 to 20 mgm. of gold can subsequently be recovered from the tails by cyanidization, whereas, if the ore were not treated as here described, but immediately subjected to ordinary cyanidization processes, it would be completely irresponsive thereto.

The following tabulation covers the results of fire assays and test runs under the herein described process, on three two-pound samples of ore.

Having fully described my invention, I claim: 1. In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes first removing said compounds without materially decomposing the ore, then treating the ore with a dispersing agent and partially dispersing the gold micelle into a hydrosol, then decanting the top liquor, and recovering'the undispersed micelle from the residue by known methods.

2. In the art of recoveringgold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes first removing said compounds without materially decomposing the ore, then treating the ore with a dispersing agent and partially dispersing the gold micelle into a hydrosol, then decanting the top liquor, recovering the undispersed micelle from the residue by known methods, redispersing the top liquor with a dispersing agent and agitating the same until the gold micelle remaining therein are in a disperse or colloid'state, and then recovering the dispersed gold from the colloid.

3. In theart of recovering gold micelle" from sedimentary or argillaceous rock containing inhibiting organic compounds,'that process which includes first removing said compounds without materially decomposing the ore, then treating the ore with a dispersing agent and partially dispersing the gold micelle into a hydrosol, then decanting the top liquor, redispersing the top liquor with a dispersing agent and'agitatingthe same until the gold micelle remaining therein are in a disperse or colloid state-and then recovering the dispersed gold from the colloid. I

- 4. In the art of recovering gold micelle 'from sedimentary or argillaceous rock containinginhibiting organic compounds and having apH of slightly. less than '7,- that process which includes first removing said compounds without materially decomposing the ore, then. treating the ore with. a-dispersing agent ofa nature and in sufiicient amount to give the pulp a distinctly basic pH, at the same time partially-dispersing the gold micelle into a gold hydrosol, then -de canting the top liquor and recovering the undis persed .micelle 'from the I, residue .-byknown methods. A a

5. In the art of recovering gold micelle from sedimentary or. argillaceous 'rock containing in hibiting organic compounds and having apH of slightly less than 7, that process whichincludes first removing said compounds without materially decomposing the ore, then-treating the ore with a dispersing agent of a natureand in sufficient amount, to give the pulp a-distinctly basicrpH, atthe sametime partially dispersing the gold micelle into a gold hydrosol, then adding a second dispersing agent andv agitating the liquor until the formation of r a gold hydrosol is completed, and then recovering the dispersed gold from the hydrosoL. l 6. In the art of preparingoreghaving, a pH of slightly less than 7 and containing gold micelle and inhibiting. organic compounds for treatmentthose. stepslwhich include, first. removing said vcompounds without materially idecomposing the .ore, followed by treatment of .the ore with adispersing agent of a. nature and in sufficient amount to give.the ore a distinctly basic pH. l '7. In the art of recovering gold micelle from sedimentary or argillaceous rock, that process which includes roasting the ore at a temperature sufficient to break down or free any organic compounds present in the ore, leaving no more than some free carbon remaining after said roasting, saidroasting temperature being insufficient to decompose the ore, oomminuting the ore subsequent to the roasting if in the roasting step the ore has not been sufficiently powdered, subjecting the powdered or comminuted ore to a dilute hydrochloric acid solution sufficient to react with approximately one per cent. of the ores content, if said roasting has not entirely broken down or freed said organic compounds, subsequently treating the comminuted or powdered ore with a dispersing agent and partially dispersing the micelle from the ore into the liquor, decanting the top liquor upon completion of the dispersion step, and recovering the undispersed micelle from the residue through known methods.

8. In the art of recovering gold micelle from sedimentary or argillaceous rock, that process which includes roasting the oreat a temperature sufiicient to break down or free any organic compounds present in the ore, leaving no more than some free carbon remaining after said roasting, said roasting temperature being insufficient to decompose the ore, oomminuting the ore subsequent to the roasting if in the roasting step the ore has not been sufliciently powdered, subjecting the powdered or comminuted or'e to a dilute hydrochloric acid solution suificient to react with approximately one per cent. of the ores content, if said roasting has not entirely.

broken down or freed saidorganic compounds, subsequently treating the comminuted or powdered ore with a dispersing agent, decanting the top liquor upon completion of the dispersion step; redispersing the top liquor with a dispersing agentand agitating the same" until the gold micelle are in a disperse or colloid state in the top liquor, and subsequently recovering the gold from thecolloid,

9. In the art of recovering gold micelle from sedimentary or argillaceous rock containing'organic compounds, that process which includes oomminuting the ore, treating the same 'with'a hydrochloric acid solution, said solution amounting to approximately two percent. of'the' entirevolume, or withnitre cake in substantially similar amount, thoroughly agitating the solution-after the hydrochloric acid or nitre cake has been added until all "action ceases, subsequently adding a dispersing agent and partially dispersing the micelle into thetop liquor, decanting the top liquor after the dispersion, and recovering the micelle from the residue by known methods.

10. In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes comminuting'the ore, treating the same with a hydrochloricacid solution, said solution amounting toapproximately two per cent. of the entire volume, or with nitre cake in substantially similar amount, thoroughly agitating the-solue tion until all action ceases, subsequently-adding a dispersing agent to-the top liquor and further agitating the-solution, settling the solution subsequent to the agitation, decanting the top liquor, redispersing the top liquor with a dispersing agent, agitating-and then settling the same until a gold hydrosol is formed, and recovering the dispersed gold from the hydrosol 11. In the art of recoveringgold micelle from, sedimentary or argillaceous rock, thatprocess which includes roasting the ore at a temperature sufiicient to break down or free any organic cornpounds present in the ore, leaving no more than some free carbon remaining after said roasting,

said roasting temperature being insufiicient to decompose the ore, comminuting the ore subsequent to the roasting if in the roasting step the ore has not been sufficiently powdered, subjecting the powdered or comminuted ore to a dilute hydrochloric acid solution sufiicient to react with approximately one per cent .of the ores content if said roasting has not entirely broken down or freed said organic compounds, simultaneously treating the comminuted or powdered ore with an inorganic and an organic dispersing agent, and partially dispersing the micelle from the ore into the top liquor, decanting the top liquor upon completion of the dispersion step, and recovering the undispersed micelle from the residue through known methods.

12. In the art of recovering gold micelle from sedimentary or argillaceous rock, that process which includes roasting the ore at a temperature sufficient to break down or free any organic compounds present in the ore, leaving no more than some free carbon remaining after said roasting, said roasting temperature being insufiicient to decompose the ore, comminuting the ore subsequent to the roasting if in the roasting step the ore has not been sufiiciently powdered, subjecting the powdered or comminuted ore to a dilute hydrochloric acid solution sufiicient to react with approximately one per cent. of the ores content, if said roasting has not entirely broken down or freed said organic compounds, subsequently treating the comminuted or powdered ore with an inorganic dispersing agent of a nature and in sufficient amount to give the top liquor and residue a pronounced alkalinity and partially dispersing the micelle from the ore into the top liquor, decanting the top liquor upon completion of the dispersion step, and recovering the undispersed micelle from the residue through known methods 13. In the art of recovering gold micelle from sedimentary or argillaceous rock, that process which includes roasting the ore at a temperature sufiicient to break down or free any organic compounds present in the ore, leaving no more than some free carbon remaining after said roasting, said roasting temperature being insufiicient to decompose the ore, comminuting the ore subsequent to the roasting if in the roasting step the ore has not been sufficiently powdered, subjecting the powdered or comminuted ore to a dilute hydrochloric acid solution sufiicient to react with approximately one per cent. of the ores content if said roasting has not entirely broken down or freed said organic compounds, subsequently treating the comminuted or powdered ore with an inorganic dispersing agent of a nature and in sufficient amount to give the top liquor and residue a pronounced alkalinity, decanting the top liquor upon completion of the dispersion step, redispersing the top liquor with an organic dispersing agent, combined with agitating the same until a gold hydrosol is formed and sub sequently recovering the dispersed gold therefrom.

14. In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes comminuting the ore, treating the same with a hydrochloric acid solution, said solution amounting to approximately two per cent. of the entire volume, or with nitre cake in substantially similar amount, thoroughly agitating the solution until all action ceases, subsequently adding an inorganic dispersing agent to the top, liquor of a nature and in sufiicient amount to give the top liquor and residue a pronounced alkalinity, and partially dispersing the micelle from the ore into the top liquor, further agitating the solution until the dispersion is completed, and settling the solution subsequent to the agitation, decanting the top liquor after the dispersion, and recovering the undispersed micelle from the residue by known methods.

l5.-In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes comminuting the ore, treating the same with a hydrochloric acid solution, said solution amounting to approximately two per cent. of the entire volume, or with nitre cake in substantially similar amount, thoroughly agitating the solution until all action ceases, subsequently adding an inorganic dispersing agent of a nature and in sufficient amount to give the top liquor and residue a pronounced alkalinity, further agitating the solution and settling the same subsequent to the agitation, decanting the top liquor, redispersing the top liquor with an organic dispersing agent, agitating and then settling the same until a gold hydrosol is formed, and recovering the dispersed gold from the hydrosol.

16. In the art of recovering gold micelle from sedimentary or argillaceous rock, that process which includes roasting the ore at a temperature of approximately 400 C. for a period of from 10 to 15 minutes, without decomposing the ore, comminuting the ore subsequent to the roasting if in the roasting step the ore has not been sufliciently powdered, subjecting the powdered or comminuted ore to a dilute hydrochloric acid solution suflicient to react with approximately one per cent. of the ores content, subsequently treating the comminuted or powdered ore with a dispersing agent, decanting the top liquor upon completion of the dispersion step, recovering the micelle remaining in the residue after dispersion and decantation through known methods, redispersing the top liquor with a dispersing agent, agitating and then settling the same until a gold hydrosol is formed and recovering the dispersed gold from the hydrosol.

1'7. In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes roasting the ore at a temperature sufficient to break down or free said organic compounds, leaving no more than some free carbon remaining after said roasting, said roasting temperature being insufficient to decompose the ore, comminuting the ore subsequent to the roasting if the roasting step in the'process has not sufliciently powdered the same, subjecting the powdered or comminuted ore to a dilute hydrochloric acid solution sufficient to react with approximately one per cent. of its content, if said roasting has not entirely broken down or freed said organic compounds, subsequently treating the comminuted or powdered ore with an inorganic dispersing agent of suificient alkalinity to give the top liquor and residue a pH of from 11.5 to 13, and partially dispersing the micelle into the top liquor, decanting the top liquor upon completion of the dispersion step, and recovering the undispersed micelle from the residue through known methods.

18. In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which ing the ore subsequent to the roasting if the roasting step in the process has not sufficiently the same until a gold hydrosol is formed, and

subsequently recovering the gold therefrom.

19. In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes comminuting the ore, treating the same with a hydrochloric acid solution, said solution amounting to approximately two per cent. of the entire volume, or with nitre cake in substantially similar amount, combined with thorough agitation until all action ceases, dispersing with an inorganic dispersing agent of sufficient alkalinity to give the top liquor and residue a pH of from 11.5 to 13, combined with further agitation until the micelle are partially dispersed into the top liquor, settling subsequent to the agitation, de- 7 canting the top liquor after the dispersion and recovering the undispersed micellefrom the residue by known methods.

20. In the art of recovering gold micelle from sedimentary or argillaceous rock containing inhibiting organic compounds, that process which includes comminuting the ore, treating the same with a hydrochloric acid solution, said solution amounting to approximately two per cent. of the entire volume, or with nitre cake in substantially similar amount, combined with thorough agitation until all action ceases, dispersing with an inorganic dispersing agent of sufficient alkalinity to give the top liquor and residue a pH of from 11.5 to 13, combined with further agitation and settling subsequent to the agitation, decantation of the top liquor, redispersing with an organic dispersing agent, and then settling the same until a gold hydrosol is formed, and recovering the dispersed gold from the hydrosol.

21. In the art of recovering gold micelle from ores having a pH of slightly less than 7, those steps comprising subjecting the ore to an inorganic dispersing agent in sufficient amounts to give the ore and top liquor a pronouncedly alkaline pH, decanting the top liquor and redispersing the same with an organic dispersing agent.

22. In the art of recovering gold micelle from sedimentary or argillaceous rock having a pH of slightly less than 7, the use of a dispersing agent composed of sodium carbonate and di-sodium hydrogen phosphate in the proportions of approximately 95 of the former to 5 of the latter.

CHAD H. HUNLPHRIES.

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