NOVEL COLLECTORS FOR THE FROTH FLOTATION OF MINERAL VALUES

Abstract: A collector and process for recovering metal values from a metal ore by subjecting the metal ore, in the form of an aqueous pulp, to a froth flotation process in the presence of a collector wherein the collector comprises a compound corresponding to the formula and n is an integer from 1 to 6 or (R) n is (CH₂) m C≡ where m is an integer from 0 to 6; R¹ and each R² are independently C₁₋₂₂ hydrocarbyl or a C₁₋₂₂ hydrocarbyl substituted with one or more hydroxy, amino, phosphonyl, alkoxy, imino, car­ bamyl, carbonyl, thiocarbonyl, cyano, carboxyl, hydrocarby­ limino groups, with the proviso that R² can be a divalent radical with both valencies bonded directly to the atom X is -S-, -O-, -N-R³, R³ is H or a C₁₋₂₂ hydrocarbyl; a is an integer of 0, 1 or 2; b is an integer of 0, 1 or 2; with the priviso that the sum of a and b equals 2 except when R² is a divalent radical with both valencies bonded directly to the N atom, in which case, b=1 and a=0 or when (R) is (CH₂) m C≡ in which case, a+b=0, and with the further proviso that when X is the carbonyl moiety is bonded to R¹.

Description: This invention relates to novel collectors for the recovery of mineral values from mineral 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 mineral 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 particles of different materials suspended therein causes the selective 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. Accordingly, these particles rise to the top of the liquid to form a froth. Various agents have been admixed with the suspension to improve the frothing and collection process. Such added agents are classed according to the function to be performed and include, for example; 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 eucalyptus oil, and the like; modifiers such as activators to induce flotation in the presence of a collector, such as copper sulfate; depressants, such as 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, such as 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 sought to be recovered, and the other additaments which are to be used in combination therewith. An understanding of the phenomenon which makes flotation a particularly valuable industrial operation is not essential to the practice of the present invention. It appears, however, to be largely associated with a 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 minerals as sulfide copper minerals, sulfide zinc minerals, sulfide molybdenum minerals and others from iron sulfide minerals, e.g., pyrite. Among collectors commonly used for the recovery of sulfide-containing metal values are xanthates, dithiophosphates,and thionocarbamates. Collectors for the recovery of sulfide-containing metal values are common and used widely. The difficulty is in the recovery of oxide-containing mineral values, as collectors suitable for the recovery of such mineral values are generally not of a commercially acceptable quality. Examples of collectors for oxide-containing mineral values can be found in FR-A-1 136 073 and EP-A-0 070 534. What is needed are collectors which are useful for the recovery of a broad range of metal values from metal ores, including the recovery of sulfide-containing mineral values and oxide-containing mineral values. Furthermore, what is needed are collectors which give high rates of recovery of the mineral values along with good selectivities towards the mineral values over the gangue, that is, the undesired portions of the mineral ore. The invention particularly resides in a collector for recovering metal values from a metal ore by froth flotation, the collector being of the formula: wherein: R is -CH₂- , n is an integer from 1 to 6 or (R) n is (CH₂) m C≡ where m is an integer from 0 to 6; R¹ and each R² are independently C₁₋₂₂ hydrocarbyl or a C₁₋₂₂ hydrocarbyl substituted with one or more hydroxy, amino, phosphonyl, alkoxy, imino, carbamyl, carbonyl, thiocarbonyl, cyano, carboxyl, hydrocarbylthio, hydrocarbyloxy, hydrocarbylamino and/or hydrocarbylimino groups, with the proviso that R² can be a divalent radical with both valences bonded directly to the N atom, wherein a and b are independently an integer of 0, 1 or 2; with the proviso that the sum of a and b = 2 except when R² is a divalent radical with both valences bonded directly to the N atom, in which case a=1 and b=0 or when (R) n is (CH₂) m C≡ in which case, a+b=0. The invention also resides in a process for recovering metal values from a metal ore, comprising the steps of subjecting the metal ore, in the form of an aqueous pulp, to a froth flotation process in the presence of a flotation collector as hereinbefore described under conditions such that the metal values are recovered in the froth. In a preferred embodiment of the invention, the collector comprises an omega-(hydrocarbylthio)alkylamine corresponding to the formula wherein: R¹ is C₁₋₂₂ hydrocarbyl optionally substituted with one or more hydroxy, amino, phosphonyl, or alkoxy moieties; R² is a C₁₋₆ alkyl,a C₁₋₆ alkylcarbonyl,or a C₁₋₆ alkyl group optionally substituted with an amino, hydroxy or phosphonyl moiety,or a C₁₋₆ alkylcarbonyl group optionally substituted with an amino, hydroxy or phosphonyl moiety; and a, b and n are as defined above. Collectors of this invention surprisingly float a broad range of metal values including sulfide ores, oxide ores and precious metals. Furthermore, such collectors give improved recoveries of the mineral values including mineral oxides, mineral sulfides and precious metals. Not only are surprisingly high recoveries achieved, but the selectivity towards the desired mineral values is surprisingly high. In the hereinbefore presented formula of the preferred embodiment, R¹ is preferably C₂₋₁₄ hydrocarbyl and more preferably C₄₋₁₁ hydrocarbyl. R² is preferably C₁₋₆ alkyl or C₁₋₆ alkylcarbonyl, more preferably C₁₋₄ alkyl or C₁₋₄ alkylcarbonyl, and most preferably C₁₋₂ alkyl or C₁₋₂ alkylcarbonyl. Preferably, a is the integer 0 or 1. Preferably, b is the integer 1 or 2. Preferably, n is an integer from 1 to 4, and most preferably the integer 2 or 3. R¹ is preferably C₄₋₁₀ hydrocarbyl. Hydrocarbon means herein an organic compound containing carbon and hydrogen atoms. The term hydrocarbon includes the following organic compounds: 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 saturated and unsaturated cyclic hydrocarbons, that is, cycloalkenes and cycloalkanes. The term aromatic includes biaryl, benzene, naphthene, phenanthracene, anthracene and two aryl groups bridged by an alkylene group. Cycloalkane refers to an alkane containing one, two, three or more cyclic rings. Cycloalkene 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, cycloalkenyl, aryl, aliphatic and cycloaliphatic aralkyl and alkaryl. Aliphatic refers herein to straight- and branched-, and saturated and unsaturated, hydrocarbon radicals, that is, alkyl, alkenyl or alkynyl. Cycloaliphatic refers herein to saturated and unsaturated cyclic hydrocarbon radicals that is, cycloalkenyl and cycloalkyl. The term aryl includes radicals of biaryl, biphenylyl, phenyl, naphthyl, phenanthrenyl, anthracenyl 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, alkenyl or alkynyl group substituted with an aryl group, wherein aryl is as defined hereinbefore. Alkenearyl refers herein to a radical which contains at least one alkene portion and one aromatic portion, and includes those radicals in which more than one alkene radical alternates with more than one aryl radical. C₁₋₂₀ alkyl 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 eicosyl groups. C₁₋₅ alkyl includes methyl, ethyl, propyl, butyl and pentyl. Cycloalkyl refers to alkyl groups containing one, two, three or more cyclic rings. Cycloalkenyl refers to mono-, di- and polycyclic groups containing one or more double bonds. Cycloalkenyl also refers to cycloalkenyl groups wherein two or more double bonds are present. The process of this invention is useful for the recovery by froth flotation of metal values from metal ores. A metal ore includes the metal as it is taken out of the ground and comprises the metal values in admixture with the gangue. Gangue refers herein to those materials which are of no value and need to be separated from the metal values. This process can be used to recover metal oxides, metal sulfides and other metal values. Sulfide ores for which these compounds may be used include copper sulfide-, zinc sulfide-, molybdenum sulfide-, cobalt sulfide-, nickel sulfide-, lead sulfide-, arsenic sulfide-, silver sulfide-, chromium sulfide-, gold sulfide-, platinum sulfide- and uranium sulfide-containing ores. Examples of sulfide ores from which metal sulfides may be concentrated by froth flotation using the process of this invention include copper-bearing ores such as, for example, covellite (CuS), chalcocite (Cu₂S), chalcopyrite (CuFeS₂) valleriite (Cu₂Fe₄S₇ or Cu₃Fe₄S₇), bornite (Cu₅FeS₄), cubanite (Cu₂SFe₄S₅), enargite (Cu₃(As₁Sb)S₄), tetrahedrite (Cu₃SbS₂) tennantite (Cu₁₂As₄S₁₃), brochantite (Cu₄(OH)₆SO₄), antlerite (Cu₃SO₄(OH)₄), famatinite (Cu₃(SbAs)S₄), and bournonite (PbCuSbS₃); lead-bearing ores such as, for example, galena (Pbs); antimony-bearing ores such as, for example, stibnite (Sb₂S₃); zinc-bearing ores such as, for example, sphalerite (ZnS); silver-bearing ores such as, for example, stephanite (Ag₅SbS₄), and argentite (Ag₂S); chromium-bearing ores such as, for example, daubreelite (FeSCrS₃); and platinum- and palladium-bearing ores such as, for example, cooperite (Pt(AsS)₂). Oxide ores for which this process may be used include copper oxide-, aluminum oxide-, iron oxide-, iron titanium oxide-, magnesium aluminum oxide-, iron chromium oxide-, titanium oxide-, manganese oxide-, tin oxide-, and uranium oxide-containing ores. Examples of oxide ore from which metal oxides may be concentrated by froth flotation using the process of this invention include copper-bearing ores, for example cuprite (Cu₂O), tenorite (CuO), malachite (Cu₂OH)₂CO₃), azurite (Cu₃(OH)₂(CO₃)₂), atacamite (Cu₂Cl(OH)₃), chrysocolla (CuSiO₃); aluminum-bearing ores, for example corundum; zinc-containing ores, such as zincite (ZnO), and smithsonite (ZnCO₃); iron-containing ores, for example hematite and magnetite; chromium-containing ores, for example chromite (FeOCr₂O₃); iron- and titanium-containing ores, for example ilmenite; magnesium- and aluminum-containing ores, for example spinel; iron-chromium-containing ores, for example chromite; titanium-containing ores, for example rutile; manganese-containing ores, for example pyrolusite; tin-containing ores, for example cassiterite; and uranium-containing ores, for example uraninite; and uranium-bearing ores such as, for example, pitchblende (U₂O₅(U₃O₈)) and gummite (UO₃nH₂O). Other metal values for which this process may be used include gold-bearing ores, for example sylvanite (AuAgTe₂) and calaverite (AuTe); platinum- and palladium-bearing ores, for example sperrylite (PtAs₂); and silver-bearing ores, such as hessite (AgTe₂), for example. In a preferred embodiment of this invention, oxide- or sulfide-containing values are recovered. In a more preferred embodiment of this invention copper sulfide, nickel sulfide, lead sulfide, zinc sulfide or molybdenum sulfide values are recovered. In an even more preferred embodiment, copper sulfide values are recovered. The collectors of this invention can be used in any concentration which gives the desired recovery of the desired metal values. In particular, the concentration used is dependent upon the particular metal value to be recovered, the grade of the ore to be subjected to the froth flotation process, the desired quality of the metal value to be recovered, and the particular mineral value which is being recovered. Preferably, the collectors of this invention are used in concentrations of from 5 g to 250 g per metric ton of ore, more preferably from 10 g to 100 g of collector per metric ton of ore to be subjected to froth flotation. Froth flotation of this invention usually requires the use of frothers. Any frother well-known in the art, which results in the recovery of the desired metal value is suitable. Further, in the process of this invention it is contemplated that collectors of this invention can be used in mixtures with other collectors,eg. 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 value. Examples of collectors useful in this invention include alkyl monothiocarbonates, alkyl dithiocarbonates, alkyl trithiocarbonates, dialkyl dithiocarbamates, alkyl thionocarbamates, dialkyl thioureas, monoalkyl dithiophosphates, dialkyl and diaryl dithiophosphates, dialkyl monothiophosphates, thiophosphonyl chlorides, dialkyl and diaryl dithiophosphonates, alkyl mercaptans, xanthogen 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. Frothers useful in this invention include any frothers known in the art which give the recovery of the desired mineral value. Examples of such frothers include c₅₋₈ alcohols, pine oils, cresols, C₁₋₄ alkyl ethers of polypropylene glycols, dihydroxylates of polypropylene glycols, glycols, fatty acids, soaps, alkylaryl sulfonates, and the like. Furthermore, blends of such frothers may also be used. All frothers which are suitable for beneficiation of mineral ores by froth flotation can be used in this invention. The omega-(hydrocarbylthio)alkylamines can be prepared by the processes disclosed in Berazosky et al., U.S.-A-4,086,273; FR-A-1,519,829; or Beilstein , 4 , 4 Ed., 4th Supp., 1655 (1979). In the following examples, unless otherwise indicated, all parts and percentages 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 wherein: r is the amount of mineral recovered at time t, K is the rate constant for the rate of recovery and R ∞ is the calculated 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 values. The above formula is explained in "Selection of Chemical Reagents for Flotation", Chapter 45, pp. 907-934, Mineral Processing Plant Design , 2nd Ed., 1980, by R. Klimpel AIME (Denver). Example 1 - Froth Flotation of Copper Sulfide In this example several of the collectors of this invention are tested for flotation of copper sulfide values. A 500-g quantity of Chilean copper ore, chalcopyrite copper sulfide ore, previously packaged is placed in a rod mill with 257 g of deionized water. The copper ore comprises 80.2 percent with a particle size of about 75 micrometers of less. A quantity of lime is also added to the rod mill, based on the desired pH for the subsequent flotation. The rod mill is then rotated at 60 rpm for a total of 360 revolutions. The ground slurry is transferred to a 1500 ml cell of an Agitair® Flotation machine. The float cell is agitated at 1150 rpm and the pH is adjusted to 10.5 by the addition of further lime, if necessary. The collector is added to the float cell (at a rate of 50 g/metric ton), followed by a conditioning time of one minute, at which time the frother, DOWFROTH® 250 (Trademark of The Dow Chemical Company) is added (at a rate of 40 g/metric ton). After the additional one-minute conditioning time, the air to the float cell is turned on at a rate of 4.5 liters per minute and the automatic froth removal paddle is started. The froth samples were taken off at 0.5, 1.5, 3, 5 and 8 minutes. The froth samples are dried overnight in an oven, along with the flotation tailings. The dried samples are weighed, divided into suitable samples for analysis, pulverized to insure suitable fineness, and dissolved in acid for analysis. The samples are analyzed using a DC Plasma Spectrograph. The collectors that were tested for flotation of copper sulfide values of a Chilean copper ore are compiled in Table I and demonstrate that a wide variety of compounds within the scope of the invention are effective in the recovery of copper sulfide values. A base case example which employed no collector is included in Table I for comparison. It should be noted that the collectors of the invention in Table I were not selected for optimum performance, but represent arbitrary selection of compounds that show a significant response in the recovery and selectivity of mineral values. Example 2 A Central African copper oxide ore (Cu₂O) is subjected to the froth flotation process described in Example 1 using 40 grams per metric ton of the frother, DOWFROTH® 250 (Trademark of The Dow Chemical Company). The results are compiled in Table II with Collector A being chosen from Table I. Collector Conc. g/ton pH Cu K R R-8 A 160 5.1 2.48 0.335 0.308 A 80 9.5 2.55 0.249 0.234 C 160 5.1 4.08 0.135 0.130 A - C₆H₁₃-S(CH₂)₂-NH₂ C - Sodium isopropyl xanthate, not an embodiment of this invention It is well known in the mining industry that existing commercial collectors such as sodium isopropyl xanthate do not float oxide minerals very effectively. It is therefore surprising that Collector A at a concentration of 80 g/ton will increase the recovery of copper values by 84.4 percent as compared to the Standard Collector C which was employed at a concentration of 160 g/ton, i.e. twice as much. When the performance of Collectors A, employing 160 g/ton is compared against the Standard C it can be seen that the recovery of copper values was increased by 148 percent. The fact that the collectors of this invention will float a substantially greater amount of copper values from copper oxide ore is indicative of the fact that the collectors of the invention are less sensitive to the form of the metal containing mineral, i.e. sulfide or oxide ore as compared to existing collectors. Example 3 A Central Canadian sulfide ore containing copper sulfide, nickel sulfide, platinum, palladium and gold metal values is subjected to a series of froth flotations as described in Example 1 using the collectors of this invention and several collectors known in the art. The frother used is DOWFROTH® 1263 (Trademark of The Dow Chemical Company) at a concentration of 0.00625 lb/ton (3.12 g/metric ton) The collectors are used at a concentration of 0.0625 lb/ton (31.2 9/metric ton). The froths produced are recovered at 0.5, 1.0, 2.0, 4.0, 7.0, 11.0 and 16.0 minutes. The results are compiled in Table III with collectors chosen from Table I. Table III illustrates the use of novel compound of this invention, i.e. OHTEA as compared to three optimized industrial collector standards. The ore was complex containing various metal values. The collectors are comparable in performance in the recovery of copper values. The OHTEA collector was clearly superior in the recovery of nickel, platinum, palladium and gold. In the recovery of nickel, the R-16 value of OHTEA when compared to Z-211® showed a slight increase but a very surprising and significant decline in the recovery of pyrrhotite, i.e. 15.5 percent. A substantial improvement was also realized in the reduction of the tailings for platinum and palladium - the values were about equal for gold. Example 4 - Froth flotation of Copper Sulfide In this example several of the collectors of this invention are tested for flotation of copper sulfide values. A 500 gram quantity of Western Canada copper ore, a relatively high grade chalcopyrite copper sulfide ore with little pyrite, is placed in a rod mill having 1 inch (2.54 cm) rods, with 257 gram of deionized 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 is also added to the rod mill, based on the desired pH for the subsequent flotation. The ground slurry is transferred to a 1500 ml cell of an Agitair® Flotation machine. The float cell is agitated at 1150 rpm and the pH is adjusted to 8.5 by the addition of further lime. The collector is added to the float cell at the rate of 8 g/metric ton, followed by a conditioning time of 1 minute, at which time the frother, DOWFROTH® (Trademark of The Dow Chemical Company) is added at the rate of 18 g/metric ton. After the additional 1 minute conditioning time, the air to the float cell is turned on at a rate of 4.5 liters per minute and the automatic froth removal paddle is started. The froth samples were taken off at 0.5, 1.5, 3, 5 and 8 minutes. The froth samples are dried overnight in an oven, along with the flotation tailings. The dried samples are weighed, divided into suitable samples for analysis, pulverized to insure suitable fineness, and dissolved in acid for analysis. The samples are analyzed using a DC Plasma Spectrograph. The results are compiled in Table IV. The compounds that were used in Examples 1 through 27 in Table IV are separately tabulated herein below: Example 4 is similar to Example 1 except that various different compounds within the scope of the invention were tested on a different copper sulfide ore. No optimization of the collectors was attempted but all of the compounds were found to be clearly superior when compared against "no collector" in the recovery of copper values. The collectors of this invention will show superior recovery and selectivity when compared to the standard known collectors and when optimized with regard to a particular ore under consideration. Example 5 - Froth Flotation of Copper Sulfide and Molybdenum Sulfide Bags of homogeneous ore are prepared with each bag containing 1200 grams. The rougher flotation procedure is to grind a 1200 gram charge with 800 cc of tap water for 14 minutes in a ball mill having a mixed ball charge (to produce appoximately a 13 percent plus 100 mesh grind). This pulp is transferred to an Agitair® 500 flotation cell outfitted with an automated paddle removal system. The slurry pH is adjusted to 10.2 using lime. No further pH adjustments are made during the test. The standard frother is methyl isobutyl carbinol (MIBC). A four-stage rougher flotation scheme is then followed. STAGE 1: Collector - 0.0042 kg/ton MIBC - 0.015 kg/ton - condition - 1 minute - float - collect concentrate for 1 minute STAGE 2: Collector - 0.0021 kg/ton MIBC - 0.005 kg/ton - condition - 0.5 minute - float - collect concentrate for 1.5 minutes STAGE 3: Collector - 0.0016 kg/ton MIBC - 0.005 kg/ton - condition - 0.5 minute - float - collect concentrate for 2 minutes STAGE 4: Collector - 0.0033 kg/ton MIBC - 0.005 kg/ton - condition - 0.5 minute - float - collect concentrate for 2.5 minutes Table V illustrates that a substantially higher grade was achieved for copper and molybdenum as compared to the Standard Collector A. For copper, the minimum increase was over 10 percent and the maximum increase was 77 percent. For molybdenum, the minimum increase in grade was about 30 percent and the maximum optimized increase was about 122 percent. Such improvements place a substantially smaller load on the smelter of a mining operation. The grade for iron with any of the Collectors B of the invention again show a substantial reduction of about 50 percent as compared to the Standard Collector A, indicating that substantially less of the undesirable pyrite is collected. This surprising selectivity in the collection of metal sulfide values over iron sulfide values is highly advantageous in the downstream operation of a mining operation as it reduces sulfur emissions. Example 6 - Froth Flotation of a Nickel/Cobalt Ore from Western Australia A series of 750 gram charges of a nickel/cobalt ore are prepared in slurry form (30 percent solids). The flotation cell is an Agitair® LA-500 outfitted with an automatic paddle for froth removal operating at 60 rpm's. A standard run is to first add 0.2 kg/metric ton of CuSO₄, condition for 7 minutes, add 0.1 kg/ton collector, condition for 3 minutes, add 0.14 kg/ton guar depressant for talc, and 0.16 kg/metric ton collector, add a frother (e.g., triethoxybutane) to form a reasonable froth bed. Concentrate collection is initiated for 5 minutes (denoted as rougher concentrate). Then 0.16 kg/metric ton collector plus 0.07 kg/metric ton guar is added to remaining cell contents along with whatever frother is necessary and concentrate collection is initiated for 9 minutes (denoted as middlings) with the remaining cell contents denoted as flotation tails. After this, the rougher concentrate is transferred to a smaller cell, 0.08 kg/metric ton collector plus 0.14 kg/metric ton guar is added to the cell with no frother, concentrate collection is initiated for 3 minutes (denoted as cleaner concentrate) with the cell contents denoted as cleaner tails. Samples are filtered, dried, and assayed using X-ray analysis methodology. Recoveries are calculated using standard metallurgical procedures. The results of this test are compiled in Table VI. The compounds that were used for Examples 1 to 3 in Table VI are tabulated hereinbelow: Collector 1 - Sodium ethyl xanthate 2 - C₆H₁₃S(CH₂)₂NH₂ 3 - The data in Table VI represents a full scale simulation of a continuous industrial flotation process. The data in the column entitled "Flotation Tail" is the most significant data since it shows actual metal loss, i.e. the lower the value in the Flotation Tail column, the lower the metal loss. The superiority of the experimental collectors of the invention over the industrial standard in this category is apparent. At a minimum, the Flotation Tail for nickel recovery showed an 8 percent drop, at a maximum, the flotation tail drop showed a surprising 81 percent drop. For cobalt, similar improvements were realized except for Collector 3. Example 7 - Froth Flotation of a Complex Pb/Zn/Cu/Ag Ore from Central Canada Uniform 1000 gram samples of ore are prepared. For each flotation run, a sample is added to a rod mill along with 500 cc of tap water and 7.5 ml of SO₂ solution. 6-1/2 minutes of mill time are used to prepare a feed in which 90 percent of the particles have a size of less than 200 mesh (75 microns). After grinding, the contents are transferred to a cell fitted with an automated paddle for froth removal. The cell is attached to a standard Denver flotation mechanism. A two-stage flotation procedure is then performed. In Stage I, a copper/lead/silver rougher, and in Stage II, a zinc rougher. To start the Stage I flotation, 1.5 g/kg Na₂CO₃ is added and the pH adjusted to 8.5, followed by the addition of the collector(s). The pulp is then conditioned for 5 minutes with air and agitation. This is followed by a 2-minute condition period with agitation only. MIBC frother is then added (standard dose of 0.015 ml/kg). Concentrate is collected for 5 minutes of flotation and labeled as copper/lead rougher concentrate. The Stage II flotation consists of adding 0.3 kg/metric ton of CuSO₄ to the cell remains of Stage I. The pH is then adjusted to 9.5 with lime addition. This is followed by a condition period of 5 minutes with agitation only. The pH is then rechecked and adjusted back to 9.5 with lime. At this point, the collector(s) is added, followed by a 5-minute condition period with agitation only. MIBC frother is then added (standard dose of 0.020 ml/kg). The concentrate is collected for 5 minutes and labeled as zinc rougher concentrate. Concentrate samples are dried, weighed, and appropriate samples prepared for assay using X-ray techniques. Using the assay data, recoveries and grades are calculated using standard mass balance formulae. Table VII illustrates the performance of optimized industrial standard collectors when compared to the collector of the invention in the recovery of metal values. Stage I of test 1 employed a combination of standard collectors A and B, while Stage II employed a combination of standard collectors A and C. Stage I of test 2 employed a mixture of a standard collector B and collector D of the invention in approximate equal amounts. Stage II of test 2 employed collector D of the invention. The goal in this test was to maintain the recovery level for silver and copper in Stage I and to increase the zinc recovery in Stage II. The results show that collector D approximately maintained the level of recovery for silver and copper with an accompanying improvement in grade. Most importantly, both the recovery (R-5) and grade of zinc in Stage II of test 2 were increased by 3 percent and 6 percent, respectively, over the standard collectors of test 1.

Claims: A collector for recovering metal values from a metal ore by froth flotation, the collector being of the formula: wherein: R is -CH₂- , n is an integer from 1 to 6 or (R) n is (CH₂) m C≡ where m is an integer from 0 to 6; R¹ and each R² are independently C₁₋₂₂ hydrocarbyl or a C₁₋₂₂ hydrocarbyl substituted with one or more hydroxy, amino, phosphonyl, alkoxy, imino, carbamyl, carbonyl, thiocarbonyl, cyano, carboxyl, hydrocarbylthio, hydrocarbyloxy, hydrocarbylamino and/or hydrocarbylimino groups, with the proviso that R² can be a divalent radical with both valences bonded directly to the N atom, wherein a and b are independently an integer of 0, 1 or 2; with the proviso that the sum of a and b = 2 except when R² is a divalent radical with both valences bonded directly to the N atom, in which case a=1 and b=0 or when (R) n is (CH₂) m C≡ in which case, a+b=0. A collector of the formula as claimed in claim 1 wherein: R is -CH₂- R² is a C₁₋₆ alkyl, C₁₋₆ alkylcarbonyl or a C₁₋₆ alkyl group optionally substituted with an amino, hydroxy or phosphonyl moiety, or a C₁₋₆ alkylcarbonyl group optionally substituted with an amino, hydroxy or phosphonyl moiety; and R¹,a, b and n are as defined in Claim 1. The collector of Claim 2, wherein R¹ is C₂₋₁₄ hydrocarbyl; R² is C₁₋₆ alkyl or C₁₋₆ alkylcarbonyl; a and b are independently the integer 0 or 1; and n is an integer of from 1 to 4. The collector of Claim 3, wherein R¹ is C₄₋₁₁ hydrocarbyl; R² is C₁₋₄ alkyl or C₁₋₄ alkylcarbonyl; n is the integer 2 or 3. The collector of Claim 1 which is an omega-(hydrocarbylthio)-alkylamine. A process for recovering metal values from a metal ore, comprising the steps of subjecting the metal ore, in the form of an aqueous pulp, to a froth flotation process in the presence of a flotation collector as claimed in Claim 1 under conditions such that the metal values are recovered in the froth. The process of Claim 6, wherein the collector is as defined in any one of Claims 2 to 5. The process of Claim 6 or 7, wherein the collector is added in an amount of from between 5 to 250 grams per metric ton of ore. The process of Claims 6, 7 or 8, wherein the metal value recovered is a metal sulfide, metal oxide or precious metal. A composition for the recovery of mineral values from mineral ores by froth flotation, which comprises: a) a collector as defined in any one of Claims 1 to 5; and b) an alkylmonothiocarbonate, alkyl dithiocarbonate, alkyl trithiocarbonate, dialkyl dithiocarbamate, alkyl thionocarbamate, dialkyl thiourea, monoalkyl dithiophosphate, dialkyl or diaryl dithiophosphate, dialkyl monothiophosphate, thiophosphonyl chloride, dialkyl or diaryl dithiophosphonate, alkyl mercaptan, xanthogen formate, xanthate ester, mercapto benzothiazole, fatty acid or a salt of a fatty acid, alkyl sulfuric acid or a salt thereof, alkyl or alkaryl sulfonic acid or a salt thereof, alkyl phosphoric acid or a salt thereof, alkyl or aryl phosphoric acid or a salt thereof, sulfosuccinate, sulfosuccinamate, primary amine, secondary amine, tertiary amine, quaternary ammonium salt, alkyl pyridinium salt, guanidine or an alkyl propylene diamine.

Inventors: HANSEN, ROBERT D., KLIMPEL, RICHARD R.
Applicants: THE DOW CHEMICAL COMPANY
Application year: 1985
Main classification: B03D1
IPC codes: B03D1, C01G39, C01G1, C09K3, C01G53, C01G3