FI77791B - SKUMBILDNINGSKOMPOSITION OCH FLOTATIONSFOERFARANDE FOER TILLVARATAGANDE AV MINERALDELAR UR MALM. - Google Patents

Description

1 77791

Foam composition and flotation method for recovering minerals from ore

The invention relates to a foam composition and a flotation method for recovering minerals from ore. The method of the present invention is not only effective in the enrichment of ores in general but is also effective in the enrichment of ores having a particle size of up to 75 μια. Fine-grained ores are commonly referred to in this art as 10 sludges.

By means of the foam composition and method according to the invention, it is possible to selectively recover mineral particles with a fine particle size from ores containing metallic or non-metallic minerals without having to transfer unwanted parts of the mal-15 min, i. side stone, foam.

When recovering fine mineral parts from ore, about 75% by weight of the ore has a particle size of up to 75 .mu.m. Preferably, 80% by weight of the ore has a particle size of up to 75 μια, and most preferably 90% by weight of the ore comprises 20 particles having a particle size of up to 75 μm or less.

The fine ores useful in this invention can be prepared by sorting the ore, i. by separating the fine particles from the medium and large particles.

This can be accomplished using a suitably sized screen or using a hydrocyclone or other methods known in the art. Alternatively, the ore may be finely ground until the ore comprises the desired percentage of fine particles. Fine grinding means reducing the particle size of the ores. This can be accomplished by any of a number of methods known in the art, for example, by grinding ore in a rod mill. Alternatively, flotation can be performed in a two-stage system in which large and medium-sized mineral particles are recovered in the first 35 stages of the flotation process and enrichment bottles containing finely divided mineral particles can then be recovered in the second stage of the flotation process using the present invention. .

The term "ore" as used herein means an ore as taken from the soil and containing mineral components mixed with the side rock. Sidestone here means substances that are worthless and must be separated from the mineral parts. The foam compositions and method of the invention can be used to recover metal oxides, metal sulfides and other metal parts.

Flotation is a commonly used method for enriching mineral parts in ore. In the flotation process, the ore is crushed and ground wet to obtain a slurry. The foam, which is usually used with a collector, is added to the ore's aqueous slurry to help separate the minerals from the unwanted or side rock portions of the ore in subsequent flotation steps. The slurry is then aerated to form a foam on its surface and the collector helps the foam separate the minerals from the ore, causing the minerals to adhere to the bubbles formed during this aeration step. Mi-20 minerals are infected selectively, so that the part of the ore that does not contain minerals, i. side stone, not adhered to bubbles. The mineral-bearing foam is collected and further processed to obtain the desired minerals. The portion of the ore that does not travel with the foam, and is commonly referred to as the "flotation bed", is generally not further processed to separate the mineral portions therefrom. The foam composition and method of the invention are generally applicable to ores containing metallic or non-metallic minerals.

In flotation, it is generally desirable to recover as many minerals as possible from the ore while the recovery is performed in a selective manner, that is, without transferring undesirable portions of the ore, i. side stone, in foam. Although numerous compounds have foam-forming properties, they are foams that are most widely used in commercial flotation operations, monohydroxy

II

3,779,71 cyclized compounds such as C 5-8 alcohols, tall oils, cresols and C 1-4 alkyl ethers of polypropylene glycols as well as dihydroxylates such as polypropylene glycols. The most commonly used foams in flotation operations are compounds containing a non-polar, water-repellent group and a simple, polar, hydrophilic group such as hydroxyl (OH). Typical foams in this group include amyl alcohol mixtures, methyl isobutylcarbolin, hexyl and heptyl alcohols, cresols, terpineol 10, and the like. Other commercially effective foams include C 1-4 alkyl ethers of polypropylene glycol, especially methyl ether and polypropylene glycols having a molecular weight of 140 to 2100, and especially those having a molecular weight of 200 to 500. In addition, certain alkoxyalkanes, e.g., triethoxybutane, are used as foams in the flotation of certain ores.

Although the mineral recovery improvements achieved with one low-cost foam can be as low as only about 1% compared to other foams, this small improvement is of great economic importance because commercial operations often process as much as 50,000 tons of ore daily. The high production rates normally found in commercial flotation processes result in relatively small improvements in mineral recovery rates resulting in the daily recovery of additional tons of minerals. In this case, it is clear that any foam which promotes an improvement in mineral recovery, even if the percentage improvement is small, can be very advantageous in commercial flotation operations.

It is well known in the flotation industry that the recovery of fine particles (sludge) of minerals with moderate selectivity over side minerals is relatively difficult. In general, the problem is not that 35 achieves a valuable ingredient, i. high yield of the mineral, but rather the fact that a much lower yield than the desired 4 77791 of minerals is obtained in order to obtain a product of acceptable quality or degree of sorting (selectivity). In practice, it is generally stated that as the yield of fine particles of minerals improves, the quality of the product (se-5 selectivity) deteriorates dramatically. In this case, there is an economic optimum between increasing the quantity of product recovered and decreasing the value of the product, which is accompanied by a deterioration in the quality of the product.

The present invention provides an improved foam composition and method for obtaining substantially better recovery of fine mineral particles by foaming. The foams of the invention are capable of selectively recovering fine mineral particles having a particle size of up to 75 microns.

In particular, the invention relates to a foam composition for recovering minerals from an aqueous slurry of an ore, wherein at least 75% by weight of the ore comprises particles having a particle size of at most 75. The foam composition according to the invention is characterized in that the foam composition 20 is a reaction product of the following components: 1) a polyhydroxy compound containing 3 or more hydroxy groups, an alkane having 1 to 20 carbon atoms or a cycloalkane having 3 to 20 carbon atoms or a mono- or disaccharide or and a mixture thereof and 2) propylene oxide or a mixture of propylene oxide and ethylene oxide, provided that at least 50 mol% of the mixture is propylene oxide and that the molecular weight of the reaction product is 150-1400.

Another aspect of the present invention relates to a method for recovering minerals from an ore, wherein at least 75% by weight of the ore comprises particles having a particle size of! at least 75 .mu.m, in which the ore in the form of an aqueous slurry is foamed in the presence of a collector and a foam, and the process is characterized in that the foam is a reaction product of the following components:

II

5 77791 1) a polyhydroxy compound containing 3 or more hydroxy groups which is an alkane having 1 to 20 carbon atoms or a cycloalkane having 3 to 20 carbon atoms or a mono- or di-saccharide or a mixture thereof and 2) propylene oxide or a mixture of propylene oxide and ethylene oxide , provided that at least 50 mol% of the mixture is propylene oxide and that the molecular weight of the reaction product is 150-1400.

The foaming composition and foaming method of the present invention surprisingly results in a high yield of minerals and at the same time a high selectivity in favor of the minerals compared to the side rock. Critical to this recovery are foams that are not only useful for flotation of large or medium-sized minerals but are also particularly effective in flotation of fine particles, i. with a particle size of up to 75 yum, resulting in improved selectivity for fine minerals compared to side rock.

In a preferred embodiment, the reaction product of the invention has the formula R 1 R 1 R 2 (HCH-CHOfnH) m i 25 wherein R is a C 3-20 or C 3-20 cycloalkane radical; R 1 is hydrogen or methyl; m is an integer from 3 to 10; and n is a number from 1 to 8; provided that each ether unit may contain only one methyl group, and with the additional proviso that at least 50% of the ether units must have one methyl group.

Any polyhydroxy-C 3-20 cycloalkane which reacts with propylene oxide or a mixture of ethylene oxide and propylene oxide can be used in the present invention. Polyhydroxy-C 3-12 alkanes and polyhydroxy-C 3-6 cycloalkanes are cycloalkyl 77791. Polyhydroxy-C3-8 alkanes and polyhydroxy-C3-8 cycloalkanes are more preferred, while trihydroxypropanes are most preferred.

Polyhydroxyalkanes and polyhydroxycycloalkanes useful in this invention include those corresponding to the formula R-fOH) m, wherein R and m are as defined above. Desirable polyhydroxyalkanes include trihydroxyethanes, trihydroxypropanes, trihydroxybutanes, trihydroxypentates, trihydroxyhexanes, trihydroxyheptanes, trihydroxyoctanes, diglycerol, sorbitol, pentaerythritol, or saccharide, monosaccharide, monosaccharide More preferred polyhydroxyalkanes are trihydroxypropanes, trihydroxybutanes, trihydroxypentanes and trihydroxyhexanes. The preferred polyhydroxyalkane is trihydroxy-1,2,3-propane. Poly here means a number of 3 or greater. Alkane polyols comprise C 1-6 alkanes containing 3 to 10 hydroxyl parts, preferably 3 to 8 hydroxyl parts, even more preferably 3 to 6 hydroxyl and most preferably 3 to 20 hydroxyl.

Polyhydroxy-C 3-20 cyanos or polyhydroxy-C 3-20 cycloalkanes are reacted with either propylene oxide or a mixture of ethylene and propylene oxide, such mixture containing at least 50 mol% of propylene oxide.

Alkylene oxides generally correspond to the following formula

O

R1C ^ - ^ VCHR1 wherein R · * · is as defined above, with the proviso that only one R * can be methyl. It is preferred to react the polyhydroxy-C 1 -C 4 alkane or polyhydroxy-C 3-20 cycloalkane with propylene oxide. In the above formulas, R is preferably a C 3-8 alkane radical or a C 3-8 cycloalkane radical, more preferably a C 3-8 alkane radical or a C 3-8 cycloalkane radical, and most preferably a C 3-8 alkane radical. Preferably m is an integer from 3 to 8, 7 77791 more preferably an integer from 3 to 6 and most preferably 3. In a preferred case, n is 1 to 4 and most preferably 1 to 3.

The blowing agents of this invention can be prepared by introducing a polyhydroxy-C 1-20 alkane. or poly-hydroxy-C 3-20 cycloalkane in contact with a suitable molar amount of propylene oxide or a mixture of ethylene oxide and propylene oxide in the presence of an alkaline catalyst such as an alkali metal hydroxide, an amine or boron trifluoride. In general, a catalyst of 0.5-1% of the total weight of the reactants can be used. Temperatures up to 150 ° C and pressures up to 689 kPa can generally be used in the reaction. In an embodiment using a mixture of propylene and ethylene oxide, propylene and ethylene oxide may be added simultaneously or sequentially.

The polyhydroxy C 1-20 alkane or polyhydroxy C 3-20 cycloalkane is reacted with a sufficient amount of propylene oxide or a mixture of ethylene oxide and propylene oxide to produce a reaction product of the desired molecular weight, especially one having a molecular weight of between 150 and 20000, more preferably between 150 and 1400, more preferably .

Sulfide ores for which the compounds of the invention are useful include copper sulfide, zinc sulfide, molybdenum sulfide, cobalt sulfide, nickel sulfide, lead sulfide, arsenic sulfide, silver sulfide, chromium sulfide, urine sulfide, platinum sulfide, platinum sulfide, platinum sulfide, Examples of sulfide ores from which metal sulfides can be enriched by flotation using the process of this invention include copper-containing ores such as hard solid (CuS), chalcosite (CU2S), chalcopyrite (CuFeS2) / valerite (Ch ^ Fe ^ Sj), bornite (CugFeS ^), cubanite (Ch ^ SFe ^ g), enargite (CU3 (As ^ Sb) S4), tetrahedral (Cu3SbS2), tennanite (Cu2As4si3) · bronchatite (Cu4 (OH) gSO4), antlerite-35 ti (Cu3SO4 (OH) 4), famatinite (Cu3 (SbAs) S4 and burnonite (PbCuSbS3); lead-bearing ores such as 8 77791 lead flux (PbS); antimony-containing ores such as antimony (Sb zinc-containing ores such as zinc flux (ZnS), silver-containing ores such as stefanite (Ag 2 Sb S 2) and silver-5 luster (Ag 2 S), chromium-containing ores such as daubrelite (FeSCr S 2), and platinum and palladium-containing ores such as cooperite (Pt (AsS) 2).

Oxide ores for which this invention is useful include ores containing copper oxide, alumina, iron taxide, iron titanium oxide, magnesium alumina, iron chromium oxide, titanium oxide, manganese oxide, tin oxide and uranium oxide. Examples of oxide ores from which metal oxides can be enriched by foaming using the process of this invention include copper-containing ores such as cuprite (Cu 2 O), Teno-rite (CuO), malachite (Cu 2 (OH) 2 CO 3), azurite (CU 3 (OH) 2 (CO 3) ) 2) t attackamide (C ^ Cl (OH) 3), chrysococcus (CUS1O3); aluminum-containing ores such as corundum; zinc-containing ores such as zincite (ZnO) and smitsonite 20 (ZnCO 3>; iron-containing ores such as hematite and magnetite; chromium-containing ores such as chromite (FeOCr 2 O 3); iron and titanium-containing ores such as ilmenite; magnesium and aluminum-containing ores such as Spinelli, iron-chromium ores such as Kro-25 mite, titanium-containing ores such as rutile, manganese ores such as pyrolucite, tin-containing ores such as cassiterite, and uranium-containing ores such as uranium ninite, and uranium-containing ores such as uranium pitch (t ^ Ogd ^ Og)) and gummite 30 (UC> 3nH 2 O). Other valuable metal minerals for which this method is useful are gold-bearing ores such as sylvanite (AuAgTe2> and fish ferrite (AuTe)), platinum- and palladium-containing ores such as sperrylite (PtAs2>; and silver-bearing ores such as hessite (35) In a preferred embodiment of the present invention, oxide or sulfide-containing valuable minerals are recovered In an even more preferred embodiment of the present invention, valuable copper sulfide, nickel sulfide, lead sulfide, zinc sulfide or molybdenum sulfide minerals are recovered. copper sulphide minerals are recovered.

The amount of blowing agent used for flotation depends on the type, grade and size of the ore particles and in particular the blowing agent used. A suitable amount is generally one that separates the desired value minerals from the ore. It has been found that foaming agents of less than 0.05 kg / ton can be used. It is preferred to use an amount between 0.0025 and 0.05 kg / ton. It is most preferred to use an amount between 0.005 and 0.05 kg / ton. The flotation method of this invention generally requires the use of a size-15 material. Any builder well known in the art that results in the recovery of a desired valuable mineral is suitable. The method of the present invention further contemplates that the blowing agents of the present invention may be used in admixture with other blowing agents known in the art.

Examples of useful herein size agents are alkyylimonotiokarbonaatit, alkyl dithiocarbonates, alkyylitritiokarbonaatit, dialkyylidi-25 thiocarbamates, alkyylitionokarbamattit, dialkyylitiokar-bamidit, monoalkyyliditiofosfaatit, dialkyl and diaryl dithiophosphates, dialkyylimonotiofosfaatit, thiophosphonyl chlorides, dialkyl and diaryyliditiofosfonaatit, alkyl-mercaptans, xanthogen formates, xanthate esters, mercaptobenzothiazoles, fatty acids and their salts, alkyl sulfuric acids and their salts, alkyl and alkyryl sulfonic acids and their salts, alkyl phosphoric acids and their salts, alkyl and aryl phosphorus acids, alkyl and aryl phosphoric acids and their salts , tertiary amines, quaternary ammonium salts, alkylpyridinium salts, guan-77791 nidine and alkylpropylenediamines. In addition, mixtures of such known builders may also be used in this invention.

The blowing agents described above can be used in admixture with other well known blowing agents. Examples of such blowing agents include C 1-4 alcohols, tall oils, cresols, C 1-4 alkyl ethers of polypropylene glycols, dihydroxylates of polypropylene glycols, glycols, fatty acids, soaps, alkylaryl sulfonates and the like. In addition, mixtures of such blowing agents can also be used. All blowing agents suitable for ore enrichment by flotation can be used in this invention.

The use of the blowing agents of this invention results in improvements in selectivity of 5% or more over the selectivities achieved using e.g. methyl isobutylcarbinol (MIBC) with the same recovery rates, preferably a selectivity of 10%. an increase in selectivity of 20 and most preferably an increase of 20%.

The following examples are intended to illustrate the invention but not to limit in any way the scope of the invention as defined by the claims. Unless otherwise indicated, all parts and percentages are by weight.

The following examples illustrate the effectiveness of the blowing agent compositions described above by indicating the rate constant and recovery rate of the blowing agent over an infinite period of time. 30 These figures have been calculated using the following formula r = F »a -

Kt where r is the amount of the recovered valuation law at time t; 35 u 77791 K is the rate constant at the recovery rate and is calculated as the amount of value mineral that could be recovered over an infinite period of time. The amount recovered at different times is determined experimentally and the series of values are placed in Equation 5 to obtain the quantities R and K. The above formula is described in "Selection of Chemical Reagents for Flotation" (R. Klimpel), paragraph 45, pages 907-934, Mineral Processing Soon Design, 2nd Edition, 1980, ΑΙΜΕ (Denver).

Example 1 In this example, 3 blowing agents are tested in the flotation of copper sulfide minerals. An amount of 500 g in Pinto Valley copper ore, i.e. chalcopyrite-copper sulfide ore, is placed in a rod mill together with 257 g of deionized water. Copper ore contains 80.2% of particles 15 with a size of about 75 micrometers or less. A certain amount of lime is also added to the rod mill depending on the desired pH in the next flotation. The rod mill is then rotated at a speed of 60 rpm for a total of 360 rpm. The ground slurry is transferred to a 1500 ml cell of 20 Agitair® flotation machines. The flotation cell is agitated at 1150 rpm and the pH is adjusted to 10.0 by adding more lime if necessary.

The aggregating agent, potassium amyl xanthate, is added to the ‘25 flotation cell (0.035 kg / tonne), followed by a conditioning period of one minute during which the blowing agent is added (0.036 kg / tonne). After a further minute of conditioning, the air supply to the flotation cell is started at a rate of 4.5 liters per minute and the automatic 30 defoamer is started. Foam samples were taken for 8 minutes. The foam samples are dried overnight in an oven along with flotation coats. The dried samples ‘·’ are weighed, divided into suitable samples for analysis, finely ground to ensure suitable fineness and dissolved in acid for analysis. Samples are analyzed using a DC-Plasa Spectrograph. The results are summarized in Table I.

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13 77791

Table I shows that the foaming agents according to the present invention have a good ability to recover valuable parts of copper minerals and at the same time a high selectivity for valuable parts of copper minerals. The selectivities of the blowing agents of this invention are superior to the selectivity of the commercial blowing agents tested in parallel. In the flotation of fine mineral particles, there is a relatively small difference in the recovery capacity of precious metals using different flotation-10 substances. The greatest difference in efficiency between blowing agents is in the amount of side rock recovered in the foam (i.e., selectivity).

In Table I and the following Table II, MIBC means methyl isobutylcarbinol. DF-200 here means DOWFROTIT® '200 (trademark of The Dow Chemical Company), which is a methyl ether of propylene glycol having an average molecular weight of about 200. DF-250 here means DOWFROTHw250 (trademark of The Dow Chemical Company), jo-20 ka is polypropylene glycol methyl ether having an average molecular weight of about 250. DF-1012 means DOWFROTH® '1012 (trademark of The Dow Chemical Company), which is polypropylene glycol methyl ether having an average molecular weight of about 400. Here, Voranorö20 a reaction product of glycerol and propylene oxide having an average molecular weight of 250. Voranol® CP 450 here means a reaction product of glycerol and propylene oxide having an average molecular weight of 700. Voranol® 2070 here means a reaction product of glycerol and propylene oxide having an average molecular weight of 700. ) / rv tolylpropylene sidi adduct as used herein means the reaction product of sorbitol and propylene oxide having an average molecular weight of 762 (or equivalent weight 127). The rose / propylene oxide adduct of precipitate-35 here means the reaction product of sucrose and propylene oxide having an average molecular weight of 984 (or equivalent weight 123).

14 77791

Example 2

El Teniente's copper ore, in which 91.1% comprises particles with a size of 75 micrometers or less, is foamed in a flotation machine using the method of Example 1. The pH of the aqueous slurry in the cell is 8.5. The aggregating agent is methyl isopropylthionocarbamate (Z-20 (trademark of The Dow Chemical Company) and is used at 0.062 kg / tonne. Foaming agents are used at concentrations of 0.025 kg / tonne. The results are summarized in Table II.

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Table II shows that the use of the blowing agents of this invention results in higher copper recoveries than the use of the commercial blowing agents to which they have been compared. Furthermore, the use of the blowing agents according to the present invention surprisingly results in better selectivities for the valuable parts of the copper minerals than the side rock than are achieved with commercial blowing agents.

Example 3 In this example, three blowing agents are tested for flotation of copper sulfide minerals. A 500 g amount of copper ore, chalcopyrite-copper sulfide ore, is pre-placed in a rod mill together with 257 g of deionized water. Depending on the desired pH, a certain amount of lime is also added to the rod mill for the next flotation. The rod mill is then rotated at a speed of 60 rpm for a total of 360 rpm to give a product in which 50.1% of the particles have a size of less than 75 micrometers. The ground slurry is transferred to a 1500 ml cell of 20 Agitair flotation machines. The flotation cell is agitated at 1150 rpm and the pH is adjusted to the desired pH (10.0) by adding more lime if necessary.

The aggregating agent, potassium amyl xanthate, is added to 25 flotation cells (0.004 kg / ton), followed by a conditioning period of one minute, during which the blowing agent (0.058 kg / tonne) is added. After an additional conditioning time of one minute, the air is blown into the flotation cell at a rate of 4.5 liters per minute and the automatic defoaming scraper is started. The foam is taken for 8.0 minutes. The foam samples are dried overnight in an oven along with flotation coats. The dried samples are weighed, divided into suitable samples for analysis, finely ground to ensure suitable fineness and dissolved in acid for analysis. The samples are analyzed

II

17 77791 using a DC Plasma Spectrograph. The weights and analysis results of the recovered foam and concentrate samples are utilized in a computer program to calculate the metal and side rock recovery and the R and K parameters. The results are summarized in Table III.

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II

77791 19

Table III shows that the use of the CP 450 blowing agents of this invention results in a substantially higher recovery of copper particles having a size of less than about 200 microns. The recovery of side rock with a coarse particle size greater than 200 microns, as well as the recovery of a side rock with a fine particle size of less than 200 microns, was significantly lower. The selectivity achieved for both coarse and fine particles was accordingly significantly higher. The percentage selectivity for fine particles has improved by at least 19 9.

Claims (10)

77791 A foam composition for recovering minerals from an aqueous slurry of an ore, wherein at least 75% by weight of the ore comprises particles having a particle size of up to 75 μm, characterized in that the foam composition is a reaction product of the following components: 1) a polyhydroxy compound containing 3 or more hydroxy groups which is 1 to 20 carbon atoms or 10 to 20 carbon atoms or a cycloalkane or mono- or disaccharide or a mixture thereof and 2. propylene oxide or a mixture of propylene oxide and ethylene oxide, provided that at least 50 mol% of the mixture is propylene oxide, and that the molecular weight of the reaction product is 150-1400. Composition according to Claim 1, characterized in that the polyhydroxyalkane or polyhydroxycycloalkane has the formula R- (OH) m, in which R is an alkane having 3 to 12 carbon atoms or a cycloalkane having 3 to 20 carbon atoms, and m is an integer 3 10. Composition according to Claim 1 or 2, characterized in that the foam is the reaction product of trihydroxy-1,2,3-propane and propylene oxide. Composition according to Claim 1, 2 or 3, characterized in that the reaction product has a molecular weight of 200 to 800. Composition according to one of the preceding claims, characterized in that the foam is added in an amount of less than 0.055 kg / t of ore. Composition according to Claim 5, characterized in that the foam is added in an amount of 0.0025 to 0.05 kg / t of ore. 7. A process for recovering minerals from an ore, wherein at least 75% by weight of the ore comprises particles with a particle size of up to 75 by foaming the ore as an aqueous slurry in the presence of a collector and a foam, characterized in that the foam is a reaction product: A polyhydroxy compound containing 3 or more hydroxy groups which is a cycloalkane of 1 to 20 carbon atoms or a cycloalkane of 3 to 20 carbon atoms or a mono- or disaccharide or a mixture thereof, and 2. Propylene oxide or a mixture of propylene oxide and ethylene oxide, provided that at least 50 mol% of the mixture is propylene oxide, and that the molecular weight of the reaction product is 150-1400. Process according to Claim 8 or 9, characterized in that the ore is a metal sulphide ore, a metal oxide ore, a gold-bearing ore, a platinum-containing ore, a palladium-containing ore or a silver-containing ore. 9. A method for recovering finely divided minerals from ore, characterized in that the ore is sorted so that at least 75% by weight of the ore comprises particles with a particle size of not more than 75 / am, the aqueous slurry is foamed in a first step so that 20 minerals is more than 75 yum is recovered in the foam while valuable minerals with a particle size not exceeding 75 yum remain in the non-foamed part of the aqueous slurry and fine minerals are recovered from the ore by foaming the remaining slurry in a second step in the presence of a collector and foam ) A polyhydroxy compound containing 3 or more hydroxy groups which is an alkane having 1 to 20 carbon atoms or a cycloalkane or 3 to 20 carbon atoms or a mono- or disaccharide or a mixture thereof and 2. propylene oxide or a mixture of propylene oxide and ethylene oxide, provided that at least 50 mol% of the mixture esta is propylene oxide, and that the molecular weight of the reaction product is 150-1400. Process according to Claim 10, characterized in that the foam is added to the aqueous slurry in an amount of less than 0.055 kg / t of ore. 77791