GB2163976A - A frother composition and a froth flotation process for the recovery of mineral values from ore - Google Patents

Abstract

The frother composition is used in a process for recovering mineral values from ore by subjecting the ore, in the form of an aqueous pulp, to a flotation process. The frother composition comprises the reaction product of 1) a polyhydroxy C1-20 alkane (including cycloalkanes) or a mono- or di-saccharide, and 2) propylene oxide or a mixture of propylene oxide and ethylene oxide, with the proviso that at least 50 mole percent of the mixture is propylene oxide, wherein the reaction product has a molecular weight of between 150 and 1400. The frother composition and process of the invention is particularly effective in the flotation of fine mineral values wherein 75 percent or more of the ore comprise particles of a size of 75 micrometers or less.

Description

SPECIFICATION A frother composition and a froth flotation process for the recovery of mineral values from ore The invention resides in a frother composition and a froth flotation process for the recovery of mineral values from ore. The process of this invention is not only effective in beneficiating ores in general but is also effective in the beneficiation of ores having a particle size of 75 micrometers or less. Fine particle size ores are generally referred to in the art as slimes.

The frother composition and process of the invention are aimed at the selective recovery the fine particles of mineral values from ores contai ni ng metallic or non-metallic mineral values without carrying over undesirable portions of the ore, i.e. gangue, in the froth.

in the recovery of fine mineral values from ore, about 75 percent of the ore typically has a particle size of 75 micrometers or less. Preferably, 80 percent of the ore has a particle size of 75 micrometers or less, and most preferably, 90 percent of the ore comprises particles having a size of 75 micrometers or less.

The fine particle size ores useful in this invention can be prepared by classifying the ore, i.e. by separating the fine particles from the medium and large particles. This can be done by the use of a sieve of the appropriate size or the use of a hydrocyclone or other methods known in the art. Alternatively, the ore can be comminuted until the ore comprises the desired percentage of fine particles. Comminution refers to the size reduction of ores. This can be achieved by one of several means known in the art, for example, grinding the ore in a rod mill.Alternatively, flotation can be performed in a two-circuit system wherein the large and medium size mineral value particles are recovered in a first step froth flotation process and the tailings which contain mineral values of a fine particle size can then be recovered by second step froth flotation process using the frother composition and process of this invention.

The term "ore" includes the ore as it is taken out of the ground, in that the ore contains both the mineral values and the gangue. Gangue refers herein to those materials which are of no value and which need to be separated from the mineral values. The froth composition and process of the invention can be used to recover metal oxides, metal sulfides and other metal values.

Froth flotation is a commonly employed process for concentrating mineral values from ores. In a flotation process, the ore is crushed and wet ground to obtain a pulp. A frothing agent, usually employed with a collecting agent, is added to an aqueous ore pulp to assist in separating valuable minerals from the undesired or gangue portions of the ore in subsequent flotation steps. The pulp is then aerated to produce a froth at the surface thereof and the collector assists the frothing agent in separating the mineral values from the ore by causing the mineral values to adhere to the bubbles formed during this aeration step. The adherence of the mineral values is selectively accomplished so that the portion of the ore not containing mineral values, i.e. the gangue, does not adhere to the bubbles.The mineral-bearing froth is collected and further processed to obtain the desired mineral values. That portion of the ore which is not carried over with the froth, usually identified as "flotation tailings", is usually not further processed for extraction of mineral values therefrom. The frother composition and process of the invention is generally applicable to ores containing metallic or non-metallic mineral values.

In froth flotation, it is generally desirable to recover as much of the mineral values as possible from the ore while effecting the recovery in a selective manner, that is, without carrying over undesirable portions of the ore, i.e. the gangue, in the froth. While a large number of compounds have foam or froth producing properties, the frothers most widely used in commercial froth flotation operations are monohydroxylated compounds such as C8 8 alcohols, pine oils, cresols and CiA alkyl ethers of polypropylene glycols as well as dihydroxylates such as polypropylene glycols. The frothers most widely used in froth flotation operations are compounds containing a non-polar, water-repellent group and a single, polar, water-seeking group such as hydroxyl (OH).Typical of this class of frothers are mixed amyl alcohols, methylisobutyl carbinol, hexyl and heptyl alcohols, cresols and terpineol. Other effective frothers used commercially are the Cur 4 alkyl ethers of phypropylene glycol, especially the methyl ether and the polypropylene glycols of 140-2100 molecular weight and particularly those in the 200-500 range. In addition, certain alkoxyalkanes, e.g., triethoxybutane, are used as frothers in the flotation of certain ores.

Although mineral value recovery improvements from a preferred frother in the treatment of an ore can be as low as only about 1 percent over other frothers, this small improvement is of great importance economically since commercial operations often handle as much as 50,000 tons of ore daily. With the high throughput rates normally encountered in commercial flotation processes, relatively small improvements in the rate of mineral value recovery result in the recovery of additional tons of mineral values daily. Obviously then, any frother which promotes improved mineral value recovery, even though it is by a small percentage, is very desirable and can be highly advantageous in commercial flotation operations.

It is well-known in the practice of froth flotation, that the recovery of fine (slime) particles of mineral values with a reasonable selectivity in favor of the mineral values over the gangue is quite difficult. Normally, the problem is not one of achieving high recovery of the valuable component, i.e. the mineral value, but rather one of accepting a much lower than desired recovery of the mineral values so as to achieve a product of an acceptable quality or grade (selectivity). In pratice, it is normally found that as the recovery of the fines of the mineral values increases, the quality of the product (selectivity) dramatically increases. Thus, an economic optimization occurs between increasing the amount of recovered product versus the drop in product value with the decreasing product grade.

Accordingly, the present invention aims to provide an improved frother composition and a process for a substantially higher recovery of fine particles of mineral values by froth flotation. Frothers of the invention are capable of the selective recovery of the fine particles of mineral values, having a particle size of 75 micrometers or less.

The invention resides in a flotation frother composition for recovering mineral values from an aqueous ore pulp, wherein 75 percent or more of the raw ore comprises particles of a size of 75 micrometers or less, said frother comprising the reaction product of 1) a polyhydroxy alkane having from 1 to 20 carbon atoms or a mono- or di-saccharide, or mixtures thereof and 2) propylene oxide or a mixture of propylene oxide and ethylene oxide, with the proviso that at least 50 mole percent of the mixture is propylene oxide, and wherein the reaction product has a molecular weight of from 150 to 1400.

Another aspect of this invention resides in a process for recovering mineral values from ore, wherein 75 percent or more of the ore comprises particles of the size of 75 micrometers or less, wherein the ore, in the form of an aqueous pulp, is subjected to a flotation'process in the presence of a flotation collector and a flotation frother, characterized in that the frother comprises the reaction product of 1) a polyhydroxy alkane having from 1 to 20 carbon atoms or a mono- or di-saccharide, or mixtures thereof and 2) propylene oxide, or a mixture of propylene oxide and ethylene oxide, with the proviso that at least 50 mole percent of the mixture is propylene oxide, wherein the reaction product has a molecular weight of from 150 to 1400.

As used herein, the term "alkane" includes cycloalkanes, including alkanes comprising a cyclic and an cyclic portion. The polyhydroxylated cycloalkanes may have from 3 to 20 carbon atoms.

The frother composition and process of this invention results, at least in preferred embodiments, in a surprisingly high recovery of mineral values with a high selectivity toward the mineral values in preference to the gangue. Critical to this recovery are frothers which are not only useful for floating mineral values of large or medium size particles but are also particularly effective in the flotation of the fine particle sizes i.e. a particles size of 75 micrometers or less, resulting in an enhanced selectivity in favor of the fine mineral values over the gangue.

In a preferred embodiment, the reaction product of the invention corresponds to the formula

wherein R is a C1 20 alkane radical or a mono- or di-saccharide radical less its hydroxyl groups; R1 is hydrogen or methyl; m is an integer of from 3 to 10; and n is a number of from 1 to 8; with the proviso that each ether unit can contain only one methyl group, and with the further proviso that at least 50 percent of the ether units must have one methyl group.

Any polyhydroxy Cm 20 alkane (including polyhydroxyC3.20 cycloalkanes) or mono- or di-saccharide which will react with propylene oxide, or a mixture of ethylene oxide and propylene oxide, can be used in this invention. Polyhydroxy C3-,2 acyclic alkanes and polyhydroxy C3 12 cycloalkanes are preferred. Polyhydroxy C3-6 acyclic alkanes and polyhydroxy C5-8 cycloalkanes are more preferred with trihydroxy propanes being most preferred.

The polyhydroxy alkanes (cyclic and acyclic) and saccharides useful in this invention include those which correspond to the formula R(OH)m wherein R and m are as hereinbefore defined. Desirable polyhydroxy alkanes include the trihydroxy ethanes, trihydroxy propanes, trihydroxy butanes, trihydroxy pentanes, trihydroxy hexanes,trihydroxy heptanes, trihydroxy octanes, diglycerol, sorbitol and pentaerythritol. Also desirable are monosaccharides, disaccharides, e.g. sucrose, or mixtures thereof. More preferred polyhydroxy alkanes include the trihydroxy propanes, trihydroxy butanes, trihydroxy pentanes, and trihydroxy hexanes. A most preferred polyhydroxy alkane is trihydroxy 1,2,3-propane. Poly refers herein to 3 or more.

Thealkanepolyols include C1 20 alkanes containing from 3 to 10 hydroxyl moieties, inclusive, more preferably from 3 to 8 hydroxyl moieties, inclusive, even more preferably from 3 to 6 hydroxyls, inclusive, and most preferably 3 hydroxyls.

The polyhydroxy Cm 20 alkanes or mono- or di-saccharides are reacted with either propylene oxide or a mixture of ethylene and propylene oxide wherein such mixture contains at least 50 mole percent of propylene oxide. The alkylene oxides generally correspond to the formula

wherein R1 is as hereinbefore defined, with the proviso that only one R1 can be methyl. Preferably, the polyhydroxy C1 20 alkane or saccharide is reacted with propylene oxide. In the hereinbefore presented formulas, R is preferably a C3 12 acyclic alkane radical, a C3-12 cycloalkane radical or a mono- or di-saccharide radical less its hydroxyl groups, more preferably a C3-6 acyclic alkane radical or C5 8 cycloalkane radical, and most preferably a C3 acyclic alkane radical. Preferably, m is an integer of from 3 to 8; more preferably an integer of from 3 to 6 and most preferably 3. Preferably, n is from 1 to 4, and most preferably from I to 3.

The frother of this invention can be prepared by contacting a polyhydroxy Con 20 alkane or a mono- or di-saccharide with the appropriate molar amount of propylene oxide, or a mixture of ethylene oxide and propylene oxide, in the presence of an alkali catalyst such as an alkali metal hydroxide, an amine, or boron trifluoride. Generally, from 0.5 to 1 percent of the total weight of the reactants of the catalyst can be used. In general, temperatures of up to 1500C and pressures of up to 689 kPa can be used for the reaction. In the embodiment wherein a mixture of propylene and ethylene oxide is used, the propylene and ethylene oxide may be added simultaneously or in a sequential manner.

The polyhydroxy C120 alkane or mono- or di-saccharide is reacted with a sufficient amount of propylene oxide or a mixture of ethylene oxide and propylene oxide so as to prepare a reaction product of the desired molecular weight, in particular, a molecular weight of from 150 to 1400, more preferably from 200 to 800, and most preferably from 250 to 500.

Sulfide ores for which the compounds of the invention are useful include copper sulfide-, zinc suiphide-, 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 (Cur2As4Sa3), brochantite (Cu4(OH)6SO4), antlerite (Cu3SO4(0H)4), famatinite (Cu3(SbAs)S4), and bournonite (PbCuSbS3); lead-bearing ores such as, for example, galena (PbS); antimonybearing 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 is useful 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 ores from which metal oxides may be concentrated by froth flotation using the process of this invention include copper-bearing ores, such as cuprite (Cu2O), tenorite (CuO), malachite (Cu2(OH)2CO3), azurite (Cu3(OH)2(CO3)2), atacamite (Cu2Cl(OH)3), chrysocolla (CuSiO3); aliminum-bearing ores, such as corundum; zinc-containing ores, such as zincite (ZnO), and smithsonite (ZnCo3); iron-containing ores, such as hematite and magnetite; chromium-containing ores, such as chromite (FeOCr2O3); iron- and titanium-containing ores, such as ilmenite; magnesium- and aluminum-containing ores, such as spinel; ironchromium-containing ores, such as chromite; titaniumcontaining ores, such as rutile; manganese-containing ores, such as pyrolusite; tin-containing ores, such as cassiterite; and uranium-containing ores, such as uranite; and uranium-bearing ores such as, for example, pitchblende (U205(U308)) and gummite (UO3nH2O). Other metal values for which this process is useful include gold-bearing ores, such as sylvanite (AuAgTe2) and calaverite (AuTe); platinum- and paladiumbearing ores, such as sperrylite (PtAs2); and silver-bearing ores, such as hessite (AgTe2).

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 amount of the frother used for froth flotation depends upon the type, the grade and the size of the ore particles and the particular frother used. Generally, that amount which separates the desired mineral values from the ore is suitable. It has been discovered that less than 0.05 kg/metric ton can be used. Preferably, an amount of from 0.0025 to 0.05 kg/metric ton is used. Most preferably, an amount of from 0.005 to 0.05 kg/metric ton is used. The froth flotation process of this invention, usually requires the use of collectors. Any collector well-known in the art, which results in recovery of the desired mineral value is suitable. Further, in the process of this invention it is contemplated that the frothers of this invention can be used in mixtures with other frothers known in the art.

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, xantrate 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, quanidine, and alkyl propylene diamines.

Furthermore, blends of such known collectors can be used in this invention also.

The frothers described hereinbefore can be used in admixture with other well-known frothers. Examples of such frothers include C8 alcohols, pine oils, cresols, C14 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 ores by froth flotationcan be used in this invention.

The frothers of this invention result in selectivity improvements of 5 percent or more over those selectivities achieved using e.g. methylisobutyl carbinol (MIBC) at the same recovery levels, preferably 10 percent selectivity increase, and most preferably a 20 percent selectivity increase.

The foliowing examples are included for illustration and are not intended to limit the scope of the Invention or claims. Unless otherwise indicated, all parts and percentages are by weight.

In the following examples, the performance of the frother compositions described herein before 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 1-e-Kt r=R# [1- ] Kt wherein: r is the amount of mineral value recovered attime t; K is the rate constant for the rate of recovery, and RX is the calculated amount of the mineral value 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 Rand K. The above formula is explained in "Selection of Chemical Reagents for Flotation" by R.Klimpel, Chapter 45, pp. 907-934, Mineral Processing Plan Design, 2nd Ed., 1980, AIME (Denver).

Example 1 In this example three frothers are tested for flotation of copper sulfide values. A 500-g quantity of Pinto Valley copper ore, i.e. chalcopyrite copper sulfide ore, 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 or 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 10.0 by the addition offurther lime, if necessary.

A collector, potassium amyl xanthate, is added to the float cell (0.035 kg/metricton), followed by a conditioning time of one minute, at which time the frother is added (0.036 kg/metricton). 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 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, pulverised 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 1.

TABLE 1 Grams Grams Copper Copper Gangue Gangue % Gram Frother Recovery Recovered Recovery Recovered Selectivity7 Selectivity2 DF-2003 0.891 6.68 0.081 39.9 11.0 0.168 MIBC3 0.880 6.60 0.088 43.3 10.0 0.152 DF-2503 0.884 6.63 0.093 45.8 9.5 0.145 DF-10123 0.877 6.58 0.110 54.2 8.0 0.121 Voranols 2025 0.847 6.35 0.048 23.6 17.6 0.269 CP450 0.913 6.85 0.069 34.0 13.2 0.202 Yoranol'2070 0.908 6.81 0.071 35.0 12.8 0.195 50,50DF-1012 0.901 6.76 0.085 41.9 10.6 0.162 + CP 450 'Selectivity is percent recovery of copper percent recovery of gangue grams of copper 2Selectivity is grams of @@@@@@ grams of gangue 3Not an example ofthis invention Table I demonstrates that the frothers of this invention demonstrate good recovery of the copper values with high selectivity towards the copper values. The selectivities of the frothers of this invention are better than the selectivities of the commercial frothers tested side by side with them. In fine mineral particle flotation there is relatively little valuable metal recovery difference when employing the different frothers.

The biggest difference in effectiveness between frothers is the amount of gangue that is recovered in the froth (i.e., selectivity).

In Table I and the followng Table II, MIBC refers to methyl isobutyl carbinol. DF-200 refers herein to DOWFROTH200 (Trademark of The Dow Chemical Company) which is a methyl ether of propylene glycol with an average molecular weight of about 200. DF-250 refers herein to DOWFROTH 250 (Trademark of The Dow Chemical Company) which is a methyl ether of polypropylene glycol with an average molecular weight of about 250. DF-1012 refers to DOWFROTH' 1012 (Trademark of The Dow Chemical Company) which is a methyl ether of polypropylene glycol with an average molecular weight of about 400. Voranol 2025 refers herein to the reaction product of glycerol and propylene oxide with an average molecular weight of 250.

VoranolCP450 refers herein to the reaction product of glycerol and propylene oxide with an average molecular weight of 700. Voranols 2070 refers herein to the reaction product of glycerol and propylene oxide with an average molecular weight of 700. Sorbitolpropylene oxide adduct refers herein to the reaction product of Sorbitol and propylene oxide with an average molecular weight of 762 (or equivalent weight of 127). Sucrose/propylene oxide adduct refers herein to the reaction product of sucrose wth propylene oxide with an average molecular weight of 984 (or equivalent weight of 123).

Example 2 An El Teniente copper ore, wherein 91.1 percent comprises particle sizes of 75 micrometers or less, is floated by a froth flotation machine using the procedure of Example 1. The pH of the aqueous pulp in the cell is 8.5. The collector is methyl isopropyl thionocarbamate (Z-200, a Trademark of The Dow Chemical Company) and used in an amount of 0.062 kg/ton. The frothers are used in concentrations of 0.025 kg/ton.

The results are compiled in Table II.

TABLE II Copper Grams % Grams Recovery Copper Gangue Gangue % Gram Frother Recovered Recovery Recovered Selectivity1 Selectivity2 MIBC3 0.914 10.05 0.091 44.5 10.0 0.226 DF-2003 0.908 9.99 0.088 43.0 10.3 0.233 DF-10123 0.867 9.54 0.115 56.2 7.5 0.170 CP-450 0.931 10.24 0.081 39.6 11.5 0.258 Sorbitolpro- pylene oxide 0.935 10.28 0.078 38.1 12.0 0.270 Adduct Sucrose/pro pyleneoxide 0.928 10.21 0.084 41.1 11.0 0.248 Adduct 50/50 DF-1012 0.904 9.94 0.098 47.9 9.2 0.208 + CP 450 Selectivity is percent recovery of copper percent recovery of gangue 2Selectivity is grams of copper grams of gangue 3Not an example of this invention Table II demonstrates that the use of the frothers of this invention result in higher recoveries of copper than the commerical frothers they are compared to. Further, the frothers of this invention result in surprisingly better selectivities for the copper values than the commercial frothers allow.

Example 3 In this example three frothers are tested for flotation of coper sulfide values. A 500-9 quantity of copper ore, chalcopyrite copper sulfide ore, previously packaged in place in a rod mill with 257 g of deionized water.

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 to produce a feed in which 50.1 percent of the particles have a size less than 75 micrometers. The ground slurry is tranferred to a 1500 ml cell of an Agitair Flotation machine. The float cell is agitated at 1150 rpm and the pH is adjusted to the desired pH (10.0) by the addition of further lime, if necessary.

The collector, potassium amyl xanthate, is added to the float cell (0.004 kg/metric ton), followed by a conditioning time of one minute, at which time the frother is added (0.058 kg/metric ton). After an 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. Froth was taken for 8.0 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, pulverised to insure suitable fineness, and dissolved in acid for anaylsis. The samples are analyzed using a DC plasma Spectrograph. The weights of recovered froth and tailings samples and the analyses are used in a computer program to calculate metal and gangue recovery, and the R and K parameters.The results are compiled in Table III.

TABLE III Selectivity1 Selectivity1 Copper Gangue +200 -200 Frother R8min(+200) R8min(-200) R8min(+200) R8min(-200) RCu/Rgangue RCu/Rgangue DF-2002 .835 .936 .071 .095 11.8 9.9 MIBC2 .830 .923 .074 .110 11.2 8.4 DF-10122 .935 .889 .084 .148 11.1 6.0 CP-450 .802 .930 .062 .079 12.9 11.8 CP-450/DF-1012 .917 .907 .077 .098 11.9 9.3 (50/50) % recovery of Cu 1Selectivity = % recovery of gangue 2Not an example of the invention Table Ill demonstrates that the use of CP-450 frothers of this invention resulted in a substantially higher recovery of copper particles having a size of less than about 200 microns. The recovery of gangue in the coarse particle size of greater than 200 microns as well as in the recovery of gangue in the fine particle size below 200 microns was substantially less. Accordingly, the selectivity recovered for both coarse and fine particles was substantially greater. The percentage selectivity for fine particles is improved by at least 19 percent.

Claims (16)

1. A flotation frother composition for recovering mineral values from an aqueous ore pulp, wherein 75 percent or more of the raw ore comprises particles of a size of 75 micrometers or less, said frother comprising the reaction product of 1) a polyhydroxy alkane having from 1 to 20 carbon atoms or a mono- or di-saccharide, or mixtures thereof and 2) propylene oxide or a mixture of propylene oxide and ethylene oxide, with the proviso that at least 50 mole percent of the mixture is propylene oxide, and wherein the reaction product has a molecular weight of from 150 to 1400.

2. A composition as claimed in claim 1, wherein the polyhydroxy alkane corresponds to the formula R(OH)rn, wherein R is-an acyclic alkane having from 3to 12 carbon atoms, a cycloalkane having from 3 to 12 carbon atoms or a mono- or di-saccharide radical less its hydroxyl groups, and m is an integer of from 3 to 10.

3. A composition as claimed in claim 1 or claim 2, wherein the frother is the reaction product of trihydroxy 1,2,3-propane and propylene oxide.

4. A composition as claimed in any one of the preceding claims, wherein the reaction product has a molecular weight of from 200 to 800.

5. A composition as claimed in any one of the preceding claims, wherein the frother is added in an amount of less than 0.055 kg/mt of ore.

6. A composition as claimed in claim 5, wherein the frother is added in an amount of from 0.0025 to 0.05 kg/mt.

7. A composition as claimed in claim 1 and substantially as hereinbefore described or exemplified.

8. A process for recovering mineral values from ore, wherein 75 percent or more of the ore comprises particles of a size of 75 micrometers or less, wherein the ore, in the form of an aqueous pulp, is subjected to a flotation process in the presence of a flotation collector and a flotation frother, wherein the frother is as defined in any one of claims 1 to 4 or 7.

9. A process as claimed in claim 8, wherein the selectivity of the process for mineral values over gangue of a particle size of 75 micrometers or less is 50 percent or more greater than the selectivity which is achieved by using methylisobutyl carbinol at the same recovery level.

10. A process as claimed in claim 8 or claim 9, wherein the 75 percent by weight or greater of the metal values recovered in the froth is of a particle size of 75 micrometers or less.

11. A process as claimed in any one of claims 8 to 10, wherein the ore is a metal sulfide ore, metal oxide ore, gold-bearing ore, platinum-bearing ore, palladium bearing ore, or silver-bearing ore.

12. A process for recovering fine mineral values from ore, comprising the steps of classifying the ore such that 75 percent or greater of the ore comprises particles of a size of 75 micrometers or less, subjecting the ore in the form of an aqueous pulp to a froth flotation process in the presence of a flotation collector and a flotation frother under conditions such that mineral values of a particle size greater than 75 micrometers are recovered in the froth, wherein the 75 percent of the mineral values in the aqueous pulp after the flotation is of a particle size of 75 micrometers or less, or comminuting the ore under conditions such that 75 percent or greater of the ore comprises particles of a size of 75 micrometers or less; and recovering the fine mineral values fron the ore by subjecting the ore, in the form of an aqueous pulp, to a flotation process in the presence of a flotation collector, and a flotation frother, wherein the frother is as defined in any one of claims 1 to4or7.

13. A process as claimed in any one of claims 8 to 12 wherein the frother is added to the aqueous pulp in an amount of less than 0.055 kg/mt of ore.

14. A process as claimed in claim 13 wherein the frother is added in an amount of from 0.0025 to 0.05 kg/mt.

15. A process for recovering mineral values using a frother as claimed in any one of claims 1 to 4 or 7 and substantially as hereinbefore described.

16. Mineral whenever recovered by a process as claimed in any one of claims 8to 15.