THE SELECTIVE FROTH FLOTATION OF

SULFIDE MINERALS

This invention concerns novel collectors for the recovery of metal containing sulfide minerals and sulfidized metal containing oxide minerals from ores by froth flotation.

Flotation is a process of treating a mixture of finely divided mineral solids, e.g., a pulverulent ore, suspended in a liquid whereby a portion of such solids is separated from other finely divided solids, e.g., clays and other like materials present in the ore, by introducing a gas (or providing a gas in situ) in the liquid to produce a frothy mass containing certain of the solids on the top of the liquid, and leaving suspended (unfrothed) other solid components of the ore. Flotation is based on the principle that introducing a gas into a liquid containing solid par¬ ticles of different materials suspended therein causes adherence of some gas to certain suspended solids and not to others and makes the particles having the gas

thus adhered thereto lighter than the liquid. Accord¬ ingly, these particles rise to the top of the liquid to form a froth.

Various flotation agents have been admixed with the suspension to improve the frothing process.

Such added agents are classed according to the function to be performed: collectors, for sulfide minerals including xanthates, thionocarbamates and the like; frothers which impart the property of forming a stable froth, e.g., natural oils such as pine oil and eucalyp¬ tus oil; modifiers such as activators to induce flota¬ tion in the presence of a collector, e.g., copper sulfate; depressants, e.g., sodium cyanide, which tend to prevent a collector from functioning as such on a mineral which it is desired to retain in the liquid, and thereby discourage a substance from being carried up and forming a part of the froth; pH regulators to produce optimum metallurgical results, e.g., lime, soda ash and the like.

It is of importance to bear in mind that additives of the hereinbefore described types are selected for use according to the nature of the ore, the mineral(s) sought to be recovered, and the other additaments which are to be used in combination therewith.

An understanding of the phenomena which makes flotation a particularly valuable industrial operation is not essential to the practice of the present inven¬ tion. The phenomena appear, however, to be largely associated with selective affinity of the surface of particulated solids, suspended in a liquid containing

entrapped gas, for the liquid on the one hand, the gas on the other.

The flotation principle is applied in a number of mineral separation processes among which is the selective separation of such metal sulfide minerals as those containing copper, zinc, lead, nickel, molyb¬ denum, and other metals from iron containing sulfide minerals such as pyrite and pyrrhotite.

Among collectors commonly used for the recov- ery of metal containing sulfide minerals or sulfidized metal containing oxide minerals are xanthates, dithio- phosphates, and thionocarbamates. Other collectors commonly recognized as useful in the recovery of metal containing sulfide minerals or sulfidized metal con- taining oxide minerals are mercaptans, disulfides

(R-SS-R) and polysulfides [R-(S) -R], wherein n is 3 or greater.

The conversion of metal containing sulfide minerals or sulfidized metal containing oxide minerals to the more useful pure metal state, is often achieved by smelting processes. Such smelting processes can result in the formation of volatile sulfur compounds. These volatile sulfur compounds are often released to the atmosphere through smokestacks, or are removed from such smokestacks by expensive and elaborate scrubbing equipment. Many nonferrous metal containing sulfide minerals or metal containing oxide minerals are found naturally in the presence of iron containing sulfide minerals such as pyrite and pyrrhotite. When the iron containing sulfide minerals are recovered in flotation processes along with the nonferrous metal containing

sulfide minerals and sulfidized metal containing oxide minerals, there is excess sulfur present which is released in the smelting processes resulting in an undesirably high amount of sulfur present during the smelting operations. What is needed is a process for selectively recovering the nonferrous metal containing sulfide minerals and sulfidized metal containing oxide minerals, without recovering the iron containing sulfide minerals such as pyrite and pyrrhotite.

Of the commercial collectors, the xanthates, thionocarbamates, and dithiophosphates do not selec¬ tively recover nonferrous metal containing sulfide minerals in the presence of iron containing sulfide minerals. On the contrary, such .collectors collect and recover all metal containing sulfide minerals. The mercaptan collectors have an environmentally undesir¬ able odor and are very slow kinetically in the flota¬ tion of metal containing sulfide minerals. The disul- fides and polysulfides, when used as collectors, give low recoveries with slow kinetics. Therefore, the mercaptans, disulfides, and polysulfides are not gener¬ ally used commercially. Furthermore, the mercaptans, disulfides and polysulfides do not selectively recover nonferrous metal containing sulfide minerals in the presence of iron containing sulfide minerals.

What is needed is a flotation collector which will selectively recover the nonferrous metal con¬ taining sulfide minerals or sulfidized metal containing oxide minerals in the presence of iron containing sulfide minerals such as pyrite and pyrrhotite.

This invention concerns a froth flotation process for selectively recovering nonferrous metal containing sulfide minerals or sulfidized metal con¬ taining oxide minerals from ores. More particularly, this invention concerns a process for recovering metal containing sulfide minerals or sulfidized metal con¬ taining oxide minerals from an ore which comprises subjecting the ore, in the form of an aqueous pulp, to a froth flotation process in the presence of a flota- ting amount of a flotation collector wherein the col¬ lector has a hydrocarbon containing one or more mono- sulfide units, wherein the carbon atoms to which the sulfur atom(s) are bound are aliphatic or cycloali¬ phatic carbon atoms, and the total carbon content of the hydrocarbon portion of the collector is such that the collector has sufficient hydrophobic character to cause the metal containing sulfide mineral or sulfidized metal containing oxide mineral particles to be driven to the air/bubble interface, under conditions such that the metal containing sulfide mineral or sulfidized metal containing oxide mineral is recovered in the froth.

The novel collectors of this invention result in surprisingly high recovery of nonferrous metal containing sulfide minerals or sulfidized metal con¬ taining oxide minerals, and a surprisingly high selec¬ tivity toward such nonferrous metal containing sulfide minerals and sulfidized metal containing oxide minerals when such metal containing sulfide minerals or sulfi- dized metal containing oxide minerals are found in the presence of iron containing sulfide minerals. These collectors demonstrate good recovery and good kinetics.

The novel collector of this invention is a hydrocarbon which contains one or more monosulfide units wherein the sulfur atoms of the sulfide units are bound to non-aromatic carbon atoms, i.e., aliphatic or cycloaliphatic carbon atoms. Monosulfide unit refers herein to a unit wherein a sulfur atom is bound to two carbon atoms of a hydrocarbon moiety only. Such hydro¬ carbon compounds containing one or more monosulfide units, as used herein, include such compounds which are substituted with hydroxy, cyano, halo, ether, hydrocar- byloxy and hydrocarbyl thioether moieties-. Non-aromatic carbon atom refers herein to a carbon atom which is not part of an aromatic ring.

Preferred hydrocarbons containing monosulfide units include those corresponding to the formula

wherein

R 1 and R2 are independently a hydrocarbyl radical or a hydrocarbyl radical substituted with one or more hydroxy, cyano, halo, ether, hydro- carbyloxy or hydrocarbyl thioether moieties;

wherein R 1 and R2 may combine to form a heterocyclic ring structure with S; with the proviso that S is bound to an aliphatic or cycloaliphatic carbon atom; with the further proviso that the total carbon content of the sulfide collector be such that the sulfide collector has sufficient hydrophobic character to cause the metal sulfide particles to be driven to the air/bubble inter¬ face.

Preferably, R1 and R2 are independently an aliphatic, cycloaliphatic or aralkyl moiety, unsub- stituted or substituted with one or more hydroxy, cyano, halo, OR 3, or SR3 moieties, wherein R3 i■s a

1 2 5 hydrocarbyl radical; wherein R and R may combine to form a heterocyclic ring with S. R 1 and R2 are more preferably an aliphatic or cycloaliphatic moiety, unsubstituted or substituted with one or more hydroxy, cyano, halo, OR 3, or SR3 moieties; wherei.n R1 and R2

10. may combine to form a heterocyclic ring with S. In a more preferred embodiment, R 1 and R2 do not combine to form a heterocyclic ring with S, and R 1 and R2 are alkyl, alkenyl, alkynyl, cycloalkyl or cycloalkenyl, unsubstituted or substituted with one or more hydroxy,

15 halo, cyano, OR 3 or SR3 moi.eti.es, wherein R3 is ali.¬ phatic or cycloaliphatic. In a most preferred embodi- ment, R 1 and R2 are independently alkyl or alkenyl, particularly R 1 i.s methyl or ethyl and R2 i.s a Cg _^ , alkyl or Cg_,.alkenyl group. In the most preferred

20 embodiment, R and R are not the same hydrocarbon

3 moiety, that is, the monosulfide is asymmetrical. R is preferably aliphatic or cycloaliphatic. R 3 is more preferably alkyl, alkenyl, cycloalkyl or cycloalkenyl.

The total carbon content of the hydrocarbon 25 portion of the hydrocarbon monosulfide collector must be such that the sulfide collector has sufficient hydrophobic character to cause the metal containing sulfide mineral or sulfidized metal containing oxide mineral particles to be driven to the air/bubble inter- 30 face. Preferably, the total carbon content of the hydrocarbon monosulfide collector is such that the minimum carbon number is 4, more preferably 6, and most preferably 8. The maximum carbon content is preferably 20, more preferably 16, and most preferably 12.

Examples of cyclic compounds useful in this invention include the following structures.

wherein R 4 is independently aryl, alkaryl, aralkyl, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, hydroxy, cyano, halo, OR 3 or SR3, wherein the aryl, alkaryl, aralkyl, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl may optionally be substituted with a hydroxy, cyano, OR 3 or SR3 moi.ety, and the li.ke; and R5 is a straight- or branched-alkylene, -alkenylene, or

-alkynylene, unsubstituted or substituted with a hydroxy, cyano, halo, OR 3 or SR3 moiety.

In another preferred embodiment of this invention, the collectors of this invention correspond to the formula

( ^R6 >3-n ^C ( ^H )n- ^S - ^C < ^H )n< ^R6 >3-n wherein

R is independently hydrocarbyl, or hydro- carbyl substituted with a hydroxy, cyano, halo, ether, hydrocarbyloxy or hydrocarbyl thioether moiety; wherein two R moieties may combine to form a cyclic ring or heterocyclic ring with the sulfur atom; n is an integer of 0, 1, 2 or 3; with the proviso that the total carbon content of the hydrocarbon portion of the collector is such that the collector has sufficient hydrophobic character

to cause the metal containing sulfide mineral or sulfidized metal ^' containing oxide mineral particles to be driven to the air/bubble interface.

Preferably, R is aliphatic, cycloaliphatic, aryl, alkaryl or aralkyl, unsubstituted or substituted

3 3 . with a cyano, hydroxy, halo, OR or SR moiety, wherein

-. fi

R is as hereinbefore defined. More preferably, R is an aliphatic or cycloaliphatic moiety, unsubstituted or substituted with a hydroxy, cyano, halo, aliphatic ether, cycloaliphatic ether, aliphatic thioether or cycloaliphatic thioether moiety. Even more preferably, R is an alkyl, alkenyl, cycloalkyl or cycloalkenyl moiety. Most preferably, one -C(H) (R ) ₃ is a methyl or ethyl moiety, and the other is a Cg ., alkyl or ^C ₆ _ιι alkenyl moiety. Preferably, n is 1, 2 or 3, and more preferably 2 or 3.

The preferred hydrocarbon containing mono- sulfide units of the formula R 1-S-R2, wherei.n R1 and R2 are defined as above, are prepared by standard methods known in the art, e.g. reacting R 2-H with R1-SH, where R 1 and R2 are defined as above.

Examples of compounds within the scope of this invention include methylbutyl sulfide, methyl- pentyl sulfide, methylhexyl sulfide, methylheptyl sulfide, methyloctyl sulfide, methylnonyl sulfide, methyldecyl sulfide, methylundecyl sulfide, methyl- dodecyl sulfide, methylcyclopentyl sulfide, methyl- cyclohexyl sulfide, methylcycloheptyl sulfide, methyl- cyclooctyl sulfide, ethylbutyl sulfide, ethylpentyl sulfide, ethylhexyl sulfide, ethylheptyl sulfide, ethyloctyl sulfide, ethylnonyl sulfide, ethyldecyl

sulfide, ethylundecyl sulfide, ethyldodecyl sulfide, ethylcyclopentyl sulfide, ethylcyclohexyl sulfide, ethylcycloheptyl sulfide, ethylcyclooctyl sulfide, propylbutyl sulfide, propylpentyl sulfide, propylhexyl sulfide, propylheptyl sulfide, propyloctyl sulfide, propylnonyl sulfide, propyldecyl sulfide, propyl- undecyl sulfide, propyldodecyl sulfide, propylcy- clopentyl sulfide, propylcyclohexyl sulfide, pro- pylcycloheptyl sulfide, propylcyclooctyl sulfide, dibutyl sulfide, butylpentyl sulfide, butylhexyl sulfide, butylheptyl sulfide, butyloctyl sulfide, butylnonyl sulfide, butyldecyl sulfide, butylun- decyl sulfide, butyldodecyl sulfide, butylcyclo- pentyl sulfide, butylcyclohexyl sulfide, butylcy- cloheptyl sulfide, butylcyclooctyl sulfide, dipen- tyl sulfide, pentylhexyl sulfide, pentylheptyl sulfide, pentyloctyl sulfide, pentylnonyl sulfide, pentyldecyl sulfide, pentylundecyl sulfide, pentyl- dodecyl sulfide, pentylcyclopentyl sulfide, pentyl- cyclohexyl sulfide, pentylcycloheptyl sulfide, pen- tylcyclooctyl sulfide, dihexyl sulfide, hexylheptyl sulfide, hexyloctyl sulfide, hexylnonyl sulfide, hexyldecyl sulfide, hexylundecyl sulfide, hexyldo- decyl sulfide, hexylcyclopentyl sulfide, hexylcy- clohexyl sulfide, hexyleyeloheptyl sulfide, hexyl- cyclooctyl sulfide, diheptyl sulfide, heptyloctyl sulfide, heptylnonyl sulfide, heptyldecyl sulfide, heptylundecyl sulfide, heptyldodecyl sulfide, hep- tylcyclopentyl sulfide, heptylcyclohexyl sulfide, heptylcycloheptyl sulfide, heptylcyclooctyl sul¬ fide, dioctyl sulfide, octylnonyl sulfide, octyl- decyl sulfide, octylundecyl sulfide, octyldodecyl sulfide, octylcyclopentyl sulfide, octylcyclohexyl sulfide, octylcycloheptyl sulfide, octylcyclooctyl sulfide, octylcyclodecyl sulfide, dinonyl sulfide,

nonyldecyl sulfide, nonylundecyl sulfide, nonyldo- decyl sulfide, nonylcyclopentyl sulfide, nonylcy- clohexyl sulfide, nonylcycloheptyl sulfide, nonyl- cyclooctyl sulfide, didecyl sulfide, decylundecyl sulfide, decyldodecyl sulfide, decylcyclopentyl sulfide, decylcyclohexyl sulfide, decylcyclohep- tyl sulfide, and decylcyclooctyl sulfide. More preferred sulfides include methylhexyl sulfide, methylheptyl sulfide, methyloctyl sulfide, methyl- nonyl sulfide, methyldecyl sulfide, ethylhexyl sulfide, ethylheptyl sulfide, ethyloctyl sulfide, ethylnonyl sulfide, ethyldecyl sulfide, dibutyl sulfide, dipentyl sulfide, dihexyl sulfide, dihep- tyl sulfide, and dioctyl sulfide.

Hydrocarbon means herein an organic compound containing carbon and hydrogen atoms. The term hydrocarbon includes the following organic com¬ pounds: alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, cycloalkynes, aromatics, aliphatic and cycloaliphatic aralkanes and alkyl-substituted aromatics.

Aliphatic refers herein to straight- and branched-chain, and saturated and unsaturated, hydrocarbon compounds, that is, alkanes, alkenes or alkynes. Cycloaliphatic refers herein to satu¬ rated and unsaturated cyclic hydrocarbons, that is, cycloalkenes and cycloalkanes.

Cycloalkane refers to an alkane contain¬ ing one, two, three or more cyclic rings. Cycloal- kene refers to mono-, di- and polycyclic groups containing one or more double bonds.

Hydrocarbyl means herein an organic radical containing carbon and hydrogen atoms. The term hydrocarbyl includes the following organic radicals: alkyl, alkenyl, alkynyl, cycloalkyl, cyclo- alkenyl, aryl, aliphatic and cycloaliphatic aralkyl and alkaryl. The term aryl refers herein to biaryl, biphenylyl, phenyl, naphthyl, phenanthrenyl, anthra- cenyl and two aryl groups bridged by an alkylene group. Alkaryl refers herein to an alkyl-, alkenyl- or alkynyl- -substituted aryl substituent, wherein aryl is as defined hereinbefore. Aralkyl means herein an alkyl group, wherein aryl is as defined hereinbefore.

^c l-20 ^a - ^Lk y^ includes straight- and branched- -chain methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicόsyl groups.

Halo means herein a chloro, bromo, or iodo group.

The process of this invention is useful for the recovery, by froth flotation, of metal containing sulfide minerals and sulfidized metal containing oxide minerals from ores. An ore refers herein to the mater¬ ial as it is taken out of the ground and includes the desired metal containing minerals in admixture with the gangue. Gangue refers herein to that portion of the material which is of no value and needs to be separated from the desired metal containing minerals.

In a preferred embodiment, metal containing sulfide minerals are recovered. In a more preferred embodiment of this invention metal sulfide containing minerals containing copper, nickel, lead, zinc, or molybdenum are recovered. In an even more preferred embodiment, sulfide minerals containing copper are recovered. Also preferred metal sulfide containing minerals are those which have high natural hydropho- bicity in the unoxidized state. The term "hydropho- bicity in the unoxidized state" applies to a freshly ground mineral or a mineral having a fresh surface which demonstrates a tendency to float without col¬ lector addition.

Ores for which these compounds are useful include sulfide mineral ores containing, copper, zinc, molybdenum, cobalt, nickel, lead, arsenic, silver, chromium, gold, platinum, uranium and mixtures thereof. Examples of metal containing sulfide minerals which may be concentrated by froth flotation using the process of this invention include copper-bearing minerals such as, for example, covellite (CuS), chalcocite (Cu ₂ S), chal- copyrite (CuFeS ₂ ), valleriite (C ₂ Fe ₄ S ₇ or Cu ₃ Fe ₄ S~), bornite (Cu ₅ FeS ₄ ), cubanite (Cu ₂ SFe ₄ S ₅ ), enargite [Cu ₃ (As ₁ Sb)S ₄ ], tetrahedrite (Cu ₃ SbS ₂ ), tennantite (Cu ₁₂ As ₄ S ₁₃ ), brochantite [Cu ₄ (0H) _g S0 ₄ ], antlerite

[Cu ₃ S0 ₄ (0H) ₄ ], famatinite [Cu ₃ (SbAs)S ₄ ] , and bournonite (PbCuSbS ); lead-bearing minerals such as, for example, galena (PbS).; antimony-bearing minerals such as, for example, stibnite (Sb ₂ S ₃ ); zinc-bearing minerals such as, for example, sphalerite (ZnS); silver-bearing minerals such as, for example, stephanite (Ag ₅ SbS ₄ ), and argentite (Ag ₂ S); chromium-bearing minerals such as, for example, daubreelite (FeSCrS,); nickel-bearing minerals such as, for example, pentlandite [(FeNi) _g Sg];

molybdenum-bearing minerals such as for example, molyb¬ denite (MoS ₂ ); arid platinum- and palladium-bearing minerals such as, for example, cooperite [Pt(asS) ₂ . Preferred metal containing sulfide minerals include molybdenite (MoS ₂ ), chalcopyrite (CuFeS ₂ ), galena

(PbS), sphalerite (ZnS), bornite (Cu ₅ FeS ₄ ), and pent- landite [(FeNi) ₉ Sg] .

Sulfidized metal containing oxide minerals are minerals which are treated with a sulfidization chemical, so as to give such minerals sulfide mineral characteristics, so the minerals can be recovered in froth flotation using collectors which recover sulfide minerals. Sulfidization results in oxide minerals having sulfide characteristics. Oxide minerals are sulfidized by contact with compounds which react with the minerals to form a sulfur bond or affinity. Such methods are well-known in the art. Such compounds include sodium hydrosulfide, sulfuric acid and related sulfur containing salts, such as sodium sulfide.

Sulfidized metal containing oxide minerals for which this process is useful include oxide minerals containing copper, aluminum, iron, tungsten, molybdenum, magnesium, chromium nickel, titanium, manganese, tin, uranium, and mixtures thereof. Examples of metal containing oxide minerals which may be concentrated by froth flotation using the process of this invention include copper-bearing minerals, such as cuprite (Cu ₂ 0), tenorite (CuO), malachite [(Cu ₂ OH) ₂ C0 ₃ ] , azurite [Cu ₃ (OH) ₂ (C0 ₃ ) ₂ ], atacamite [Cu ₂ Cl(OH) ₃ 3, chrysocolla (CuSiO-); aluminum-bearing minerals, such as corundum; zinc-containing minerals, such as zincite (ZnO), and smithsonite (ZnC0 ₃ ); tungsten-bearing minerals such as

wolframite (Fe,Mn)W0 ₄ ; nickel-bearing minerals such as bύnsenite (NiO); molybdenum-bearing minerals such as wulfenite (PbMo0 ₄ ), and powellite (CaMo0 ₄ ); iron-con¬ taining minerals, such as hematite and magnetite; chromium-containing minerals, such as chromite

(FeOCr ₂ 0 ₃ ); iron- and titanium-containing minerals, such as ilmenite; magnesium- and aluminum-containing minerals, such as spinel; iron-chromium-containing minerals, such as chromite; titanium-containing miner- als, such as rutile; manganese-containing minerals, such as pyrolusite; tin-containing minerals, such as cassiterite; and uranium-containing minerals, such as uraninite; and uranium-bearing minerals such as, for example, pitchblende [U ₂ 0 ₅ (U ₃ Og)] and gummite (U0 ₃ nH ₂ 0).

The collectors of this invention can be used in any concentration which gives the desired recovery of the desired minerals. In particular, the concen¬ tration used is dependent upon the particular mineral(s) to be recovered, the grade of the ore to be subjected to the froth flotation process, the desired quality of the mineral to be recovered, and the particular mineral which is being recovered. Preferably, the collectors of this invention are used in concentrations of 0.001 kg to 1.0 kg per metric ton of ore, more preferably between about 0.010 kg and 0.2 kg of collector per metric ton of ore to be subjected to froth flotation.

Frothers are preferably used in the froth flotation process of this invention. Any frother well-known in the art, which results in the recovery of the desired mineral is suitable.

Frothers useful in this invention include any frothers known in the art which give the recovery of the desired mineral. Examples of such frothers include C ₅ _ ₈ alcohols, pine oils, cresols, C ₁ _ ₄ alkyl ethers of polypropylene glycols, dihydroxylates of polypropylene glycols, glycols, fatty acids, soaps, alkylaryl sul- fonates, and the like. Furthermore, blends of such frothers may also be used. All frothers which are suitable for beneficiation of ores by froth flotation can be used in this invention.

Further, in the process of this invention it is contemplated that collectors of this invention can be used in mixtures with other collectors well-known in the art. Collectors, known in the art, which may be used in admixture with the collectors of this invention are those which will give the desired recovery of the desired mineral. Examples of collectors useful in this invention include alkyl monothiocarbonates, alkyl dithiocarbonates, alkyl trithiocarbonates, dialkyl dithiocarbonates, alkyl thionocarbamates, dialkyl thioureas, monoalkyl dithiophosphates, dialkyl and diaryl dithiophosphates, dialkyl monothiophosphates, dialkyl and diaryl thiophosphonyl chlorides, dialkyl and diaryl dithiophosphonates, alkyl mercaptans, xan- thogen formates, xanthate esters, mercapto benzothiazoles, fatty acids and salts of fatty acids, alkyl sulfuric acids and salts thereof, alkyl and alkaryl sulfonic acids and salts thereof, alkyl phosphoric acids and salts thereof, alkyl and aryl phosphoric acids and salts thereof, sulfosuccinates, sulfosuccinamates, primary amines, secondary amines, tertiary amines, quaternary ammonium salts, alkyl pyridinium salts, guanidine, and alkyl propylene diamines.

Specific Embodiments

The following examples are included for illustration and are not intended to limit the scope of the invention. Unless otherwise indicated, all parts and fractions are by weight.

In the following examples, the performance of the frothing processes described is shown by giving the rate constant of flotation and the amount of recovery at infinite time. These numbers are calculated by using the formula

l-e ^{" t}

wherein: γ is the fractional amount of mineral recov- ered at time t, k is the rate constant for the rate of recovery and R^ is the calculated fractural amount of the mineral which would be recovered at infinite time. The amount recovered at various times is determined experimentally and the series of values are substituted into the equation to obtain the R^ and k. The above formula is explained in Klimpel, "Selection of Chemical Reagents for Flotation", Chapter 45, pp. 907-934, Mineral Processing Plant Design, 2nd Ed., 1980, AIME (Denver) .

Example 1 - Froth Flotation of a Copper Contain¬ ing Sulfide Mineral

In this example several of the collectors of this invention were tested for flotation of copper containing sulfide minerals. A 500 g quantity of Western Canada copper ore, a relatively high grade chalcopyrite

containing ore with little pyrite, was placed in a rod mill having one-inch (2.5 cm) rods, with 257 g of deion- ized water and ground for 420 revolutions at a speed of 60 rpm to produce a size distribution of 25 percent less than 100 mesh. A quantity of lime was also added to the rod mill, based on the desired pH for the sub¬ sequent flotation. The ground slurry was transferred to a 1500 ml cell of an Agitair Flotation machine. The float cell was agitated at 1150 rpm and the pH was adjusted to 8.5 by the addition of further lime.

The collector was added to the float cell (8 g/metric ton), followed by a conditioning time of one minute, at which time the frother, DOWFROTH^ 250, was added (18 g/metric ton). After an additional one-minute conditioning time, the air to the float cell was turned on at a rate of 4.5 liters per minute and the automatic froth removal paddle was started. The froth samples were taken off at 0.5, 1.5, 3, 5 and 8 minutes. The froth samples were dried overnight in an oven, along with the flotation tailings. The dried samples were weighed, divided into suitable samples for analysis, pulverized to insure suitable fineness, and dissolved in acid for analysis. The samples were analyzed using a DC Plasma Spectrograph. The results are compiled in Table I.

to < I wo in to tn oo Φ> to to t MtoωtoωvDooototo to c. Φ> H in VD 00 tO D Φ> l . t U H I Ul W Ul B H H ϊ. in π -J φ> O VD C. O σ>tM vβμuHθnDi. σι o

3

O O O O O O O O O O O O O O O O O O O O M O

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H> tn - 3 00 -J 00 -J 00 -J 131 ω in M O Φ» ι-3 CO f

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-J 00 VD VD oo oo ID D 03 ω ω ύ ωtot ωtncou)tncov. c. I 3 φ> tn o M tn c. o M tn oo Φ> vD U Φ OHn Ulι|. . Ul i. W 00 σ> 00 ω vD O l- _ O W H 0O ω t o vD tπ ω D M M o ω .

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M M to to M M M to M O O O O O O M M O M M tO M σi o o t j C. 00 O ^» . D -j 00 σi c. -. C- O vD '-' Oo ω i. ω M 00 00 tn oo oo to tn ω oo VD -J » t vD vD tO vD 00 «J O tn

rt c_ » tn μ n> Φ- tn *» > > « > Φ> tn »{-• . , tn > n> « *> . H-φ < M σ> o to o to oo tn VD M tn Φ> O -^J Φ» C. O tn ω OO tn M OO H-Φ

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-61- osεoo/98sn/iDd T8690/98 OΛV

TABLE I (Cont'd)

Cu Gangue C Gangue Selec¬

Collector K R K R R-8 ¹ R-8 ¹ tivity

7,8-epithio-l,2-octene . 5.75 0.904 3.64 0.182 0.899 0.184 4.9 9,10-epithio-l,2-decene 3.89 0.918 2.50 0.189 0.902 0.186 4.8 ethyloctyl sulfide 4.56 0.920 3.52 0.184 0.891 0.180 5.0 me hyloctyl sulfide 6.68 0.802 4.29 0.158 0.803 0.159 5.1 cyanomethyloctyl sulfide 7.17 0.723 5.32 0.156 0.707 0.155 4.6 1,2-epithio octane 4.13 0.942 2.82 0.206 0.919 0.202 4.5 1,2-epithio dodecane 1.48 0.892 1.24 0.184 0.792 0.162 4.9 1,2-epithio hexane 6.58 0.815 5.29 0.174 0.794 0.170 4.7 3-t-butoxy-l,2-epi- thio propane 4.37 0. 635 3.84 0.132 0.631 0.128 4. 9 3-n-butoxy-l,2-epi- thio propane 5 .85 0. 770 ^" 5.38 0.163 0.751 0.163 4.6 3-phenoxy-l,2-epi- thio propane 5.23 0.477 4.95 0.115 0.464 0.113 4.1 1,2-epithio-5,6-hexene 4.94 0.743 4.36 0.150 0.720 0.148 4.9 4,5-dihydro-2-thia- zolethiol 4.96 0.586 4.04 0.151 0.567 0.148 3.8 2-butylthiophene 3.19 0.363 2.31 0.080 0.350 0.077 4.5 2-benzotKiazolethiol 3.19 0.620 2.49 0.131 0.588 0.125 4.7 3-butoxythietane 8.21 0.907 . 5.11 0.203 0.888 0.200 4.4

TABLE I (Cont'd)

Cu Cu Gangue Selec¬

Collector K R K R R-8 ¹ R-8 ¹ tivity l,2-bis(4-n-butylthio) ethane 2 . 02 0.846 1.59 0.195 0.777 0.178 4.4

2-hydroxyethyloctyl sulfide 6 .50 0 .810 5.17 0.180 0.797 0.180 4.4

2-me hoxyethylhexyl sulfide 6.26 0 .889 4.78 0.188 0.872 0.187 4.7

2-chloroethyl- hexyl sulfide 7 .12 0.676 5.69 0.146 0.662 0.147 4.5

¹ R-8 is experimental fractional recovery after 8 minutes

² Selectivity is calculated as the copper recovery at 8 minutes divided by the gangue at 8 minutes ³ Not an example of the invention

The collectors of this invention demonstrate better rates and equilibrium recovery than mercaptan and polysulfide collectors.

Example 2 - Froth Flotation of a Copper/Molybdenum Ore

Bags of homogeneous ore containing chal¬ copyrite and molybdenite minerals were prepared with each bag containing 1200 g. The rougher flotation procedure was to grind a 1200 g charge with 800 ml of tap water for 14 minutes in a ball mill having a mixed ball charge (to produce approximately a 13 percent plus 100 mesh grind). This pulp was transferred to an Agitair 1500 ml flotation cell outfitted with an auto¬ mated paddle removal system. The slurry pH was adjusted to 10.2 using lime. No further pH adjustments were made during, the test. The standard frother was methyl iso- ^• butyl carbinol ( IBC). A four-stage rougher flotation scheme was then followed.

STAGE 1: Collector - 0.0042 kg/metric ton MIBC - 0.015 kg/metric ton

- condition - 1 minute

- float - collect concentrate for 1 minute

STAGE 2: Collector 0.0021 kg/metric ton MIBC 0.005 kg/metric ton condition - 0.5 minute float - collect concentrate for 1.5 minutes

STAGE 3: Collector - 0.0016 kg/metric ton MIBC - 0.005 kg/metric ton

- condition - 0.5 minute

- float - collect concentrate for 2.0 minutes

STAGE 4: Collector - 0.0033 kg/metric ton MIBC - 0.005 kg/metric ton

- condition - 0.5 minute

- float - collect concentrate for 2.5 minutes

The results are compiled in Table I I

TJABLE I I

Copper/Molybdenum Ore from Western Canada

Col¬ Dosage Ave Ave Ave lec¬ g/metric CU Molyb Cu Mo Fe tor ton R-7 ¹ R-7 ¹ Grade ² Grade ² Grade ²

A 11.2 0.776 0.725 0.056 0.00181 0.254

B 11.2 0.710 0.691 0.093 0.00325 0.149

B 6.7 0.730 0.703 0.118 0.00390 0.155

B 22.4 0.756 0.760 0.105 0.00346 0.161

C 11.2 0.699 0.697 0.107 0.00386 0.164

C 22.4 0.723 0.723 0.112 0.00392 0.142

A - potassium amyl xanthate, not an example of this invention

B - 1,2-epithiooctane C - hexylmethyl sulfide

¹ - R-7 is the experimental fractional recovery after 7 minutes ² - Grade is the fractional content of the specified metal in total weight collected in the froth

The use of the collectors of this invention has a significant influence both on improving the overall concentrate grade (the fraction of desired metal containing sulfide mineral in the final flotation product) as well as a significant lowering of pyrite in the concentrate as measured by the lowering of the Fe assay of the product. This is true regardless of the dosage being used. This means less mass being fed to smelters and less sulfur emissions per unit of metal being produced.

Example 3 - Froth Flotation of Copper/Nickel

Ore from Eastern Canada Containing Very High Amounts of Iron Sulfide Mineral in the Form of Pyrrhotite A series of samples were drawn from the feeders to plant rougher bank and placed in buckets to give approximately 1200 g of solid. The slurry con¬ tained chalcopyrite and pentlandite minerals. The contents of each bucket were then used to perform a time-recovery profile on a Denver cell using an auto¬ mated paddle and constant pulp level device with indivi¬ dual concentrates selected at 1.0, 3.0, 6.0 and 12.0 minutes. The collectors were added once with a con¬ dition time of one minute before froth removal was started. The dosage of the collectors was 0.028 kg/- metric ton of flotation feed. Individual concentrates were dried, weighed, ground and statistically represen¬ tative samples prepared for assay. Time-related recover¬ ies and overall head grades are calculated using standard mass balance equations.

TABLE III Cu/Ni Ore from Eastern Canada

Cu Ni Pyrrho¬

Cu Ni tite Selec¬

Collector K R K R R-12 ¹ R-12 ¹ R-12 ¹ tivity ²

CsHuOCSgNa 5.71 0.943 3.35 0.866 0.931 0.849 0.393 2.16 ( sodium amyl xanthate )

H

I

^C ₆ ^H i ₃ -C-CH ₂ 8.22 0.938 2.24 0.790 0.927 0.751 0.247 3.04 s

C ₄ H ₉ SC ₄ H ₉ 9.61 0.937 2.95 0.656 0.928 0.630 0.190 3.32

¹ R-12 is experimental fractional recovery after 12 minutes ² Selectivity is calculated as the nickel recovery at 12 minutes divided by the pyrrhotite recovery at 12 minutes

The collectors of this invention give a copper recovery comparable to sodium amyl xanthate; the collectors of this invention result in much higher rates of flotation. The collectors of this invention result in a lower nickel recovery than sodium amyl xanthate, but also provide a much lower recovery of undesired iron sulfide pyrrhotite. This is indicated by the R, ₂ value of pyrrhotite and the about 50 percent increase in selectivity of nickel sulfide mineral over the undesired iron sulfide mineral pyrrhotite.

Example 4 - Froth Flotation of A complex Pb/Zn/Cu/Ag Ore from Central Canada

Uniform 1000 g samples of ore were prepared. The ore contained galena, sphalerite, chalcopyrite, and argentite minerals. For each flotation run, a sample was added to a rod mill along with 500 ml of tap water and 7.5 ml of S0 ₂ solution. Six and one-half minutes of mill time were used to prepare a feed of 90 percent less than 200 mesh (75 microns). After grinding, the contents were transferred to a cell fitted with an automated paddle for froth removal, and the cell was attached to a standard Denver flotation mechanism.

A two-stage flotation was then performed. In Stage I, a copper/lead/silver rougher float was carried out, and in Stage II, a zinc rougher float was carried out. To start the Stage I flotation, 1.5 g/kg Na ₂ C0 ₃ was added (pH of 9 to 9.5), followed by the addition of collector(s). The pulp was then conditioned for 5 minutes with air and agitation. This was followed by a 2-minute condition period with agitation only. MIBC frother was then added (standard dose of 0.015 ml/kg).

Concentrate was collected for 5 minutes of flotation and labeled as copper/lead rougher concentrate.

The Stage II flotation consisted of adding 0.5 kg/metric ton of CuS0 ₄ to the cell remains of Stage I. The pH was then adjusted to 10.5 with lime addition. This was followed by a condition period of 5 minutes with agitation only. pH was then rechecked and adjusted back to 10.5 with lime. At this point, the collector(s) were added, followed by a 5-minute con- dition period with agitation only. MIBC frother was then added (standard dose of 0.020 ml/kg) . Concentrate was collected for 5 minutes and labeled as zinc rougher concentrate.

Concentrate samples were dried, weighed, and appropriate samples prepared for assay using X-ray techniques. Using the assay data, recoveries and grades were calculated using standard mass balance formulae.

In addition to the above procedure, tests were also run at lower pH in Stage I (no Na ₂ CO_ was added, giving a pH of 8.5) and in Stage II only enough lime was added to give a pH of 9.5. Also with the lower pH, 0.3 kg/metric ton of CuS0 ₄ was added.

TABLE IV

Pb/Zn/Cu/Ag Ore from Central Canada

Test Stage Col¬ Dosage Ag Cu Pb Zn No. (Rougher) lector (g/metric t) PH R-5 ¹ Grade ² R-5 ¹ Grade ² R-5 ¹ Grade ² R-5 ¹ Grade ²

₉ Cu/Pb D 12.5 9.5 0.869 0.294 0.930 0.120 0.709 0.050 0.207 Zn D 35 10.5 0.079 0.039 0.154 0.772 0.447

, Cu/Pb E 12.5 9.5 0.871 0.264 0.936 0.106 0.748 0.049 0.234 ^J Zn E 35 10.5 0.067 0.031 0.114 0.741 0.460

A 5 r- Cu/Pb .843 0.286 0.926 0.120 0.738 0.053 0.179 - B 7.5 8.5 0

4

L Zn A 20 09 - 0.057 - 0.155 - 0.808 0.314 C 15 9.5 0.1

TABLE IV (Cont'd)

Pb/Zn/Cu/Ag Ore from Central Canada a T _* es .t. cS _÷ t.age -Coιl- _T D _X osage Ag ^δ Cu Pb Zn '

No. (Rougher) lector (g/metric t) pH R-5 ¹ Grade ² R-5 ¹ Grade ² R-5 ¹ Grade ² R-5 ¹ Grade ²

Cu/Pb D 12.5. 8.5 0.792 0.337 0.912 0.142 0.593 0.061 0.151 -

Zn D 35 9.5 0.145 - 0.068 - 0.275 - 0.829 0.414

, Cu/Pb E 12.5 8.5 0.748 0.382 0.860 0.159 0.567 0.060 0.104

Zn E 35 9.5 0.158 - 0.105 - 0.276 - 0.873 0.451

A - sodium ethyl xanthate

B - dithiophosphate

C - thionocarbamate

A, B and C are not examples of this invention

D - 1,2-epithio octane

E - octylmethyl sulfide

^• -.-5 is the actual fractional recovery after 5 minutes ² Grade is the fractional content of the specified metal in total weight collected in the froth

This is a complicated flotation which shows tlie rather remarkable result that the collectors of this invention can be substituted for a complex mixture of 3 commercially optimized collectors and essentially match the metal recoveries and grades at the normal pH and CuS0 ₄ selected as optimal for the commercial col¬ lectors (tests 1, 2, 3). The corresponding tests (4, 5, 6) at lower pH and CuS0 ₄ also show that the collec¬ tors of this invention are capable of giving signifi- cantly improved metal grades over the 3 commercial col¬ lectors. This result can represent significant savings in lime arid CuS0 ₄ costs to a plant operation. (The main reason pH was controlled to 10.5 in Stage I and 9.5 in Stage II was to improve selectivity. The main reason for adding CuS0 ₄ was to improve Zn recovery while maintaining grade. ) Note that at the lower CuS0 ₄ runs (5, 6) the collectors of this invention actually increased Zn recovery and maintain good grade.

Example 5 - Froth Floatation of a Copper/ Molybdenum Ore

A 500 g quantity of a copper/molybdenum ore from South America was placed in a rod mill having one-inch (2.5 cm) rods along with 257 g of deionized water and a quantity of lime. The mixture was ground for 360 revolutions at a speed of 60 rpm to produce a size distribution of suitable finess (about 25 percent less than 100 mesh). The ground slurry, containing various copper containing sulfide minerls and molyb¬ denite, was transferred to a 1500 ml cell of an Agitair Flotation machine. The float cell was agitated at 1150 rpm and the pH was adjusted to 8.5 by the addition of either lime or hydrochloric acid.

The collector was added to the float cell (45 g/metric ton), followed by a conditioning time of one minute, at which time the frother, DO FROTH 250, was added (36.4 g/metric ton). After an additional conditioning time of one minute, the air to the float cell was turned on at a rate of 4.5 liters per minute and the automatic froth removal paddle was started. Samples of the froth were collected at 0.5, 1.5, 3, 5, and 8 minutes. The froth samples were dried overnight in an over along with the flotation tailings. The dried samples were weighed, divided into suitable samples for analysis, pulverized to insure suitable fineness, and dissolved in acid for analysis on a DC Plasma Spectrograph. The results are compiled in Table V.

TABLE V

Cu Mo Fe

Collector ppHH R R--88 ²² R R--88 ²² R R--88 ²² .

Xanthate/thio- nocarbamate ¹ 10.5 0.891 0.742 0.398

Octyl ethyl sulfide 10.5 0.854 0.791 0.278

Xanthate/thio- nocarbamate ¹ 8.0 0.912 0.780 0.422

Octyl ethyl sulfide 8.0 0.887 0.822 0.394

^x Not an example of the invention (50/50 w/w mixture of sodium ethyl xanthate and isopropyl ethyl thionocarbamate)

² R-8 is experimental fractional recovery after 8 minutes

The collectors of this invention show a significant increase in molybdenum recovery over the standard reagent; however, there is a decrease in the copper recovery. Also a very significant desired decrease is shown in the recovery of iron-bearing sulfide minerals.

Example 6 - Froth Flotation of a Copper Ore

When the procedure of Example 1 was repeated using a relatively high grade chalcopyrite containing ore with little pyrite from a different location in the same mine as Example 1, the following results were obtained as compiled in Table VI.

TABLE VI

Cu Gangue

Collector K R K R ethyl isopropyl 4.21 0.369 3.01 0.092 0. sulfide ethyl butyl sulfide 9.52 0.765 6.46 0.174 0 1,2-epithio octane 1.49 0.969 1.34 0.200 0 ethyl octyl sulfide 2.51 0.909 2.27 0.179 0. methyl dodecyl sulfide 1.78 0.615 1.23 0.152 0 sodium sulfide ³ 1.39 0.215 1.34 0.439 0

^x R-8 is experimental fractional recovery after 8 minutes

² Selectivity is calculated as the copper recovery at 8 minutes the gangue at 8 minutes ³ Not an example of this invention

This example illustrates two fractors: 1) the influence of the hydrophobic portion of the collector; 2) the comparison of the compounds of this invention to a simple inorganic sulfide (Na ₂ S).