EP4626615A1

EP4626615A1 - Mixtures of frothing agents for flotation of ores

Info

Publication number: EP4626615A1
Application number: EP23810391.5A
Authority: EP
Inventors: Graeme Levi STEWART; Bettina Sobotka; Daniel CHIPFUNHU; Frank Dierschke
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2022-12-01
Filing date: 2023-11-24
Publication date: 2025-10-08
Also published as: WO2024115327A1; AU2023399987A1; MX2025006339A; CN120435351A; CL2025001596A1

Abstract

The invention relates to a frothing agent mixture of at least 2 frothing agents, wherein one of the frothing agents is 2,4-diethyl-octane-1,5-diol or a distillation residue derived from the manufac- turing process of 2-ethylhexanol comprising 2,4-diethyl-octane-1,5-diol and at least one of the other frothing agents is not comprised in such distillation residue, which is selected from methyl isobutyl carbinol, a distillation residue obtained by hydro-formylation of 1-propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol. Furthermore, the use of such frothing agent mixture in flotation is described. The invention also relates to a method for flotation of an ore, which comprises the steps of (A) providing an aqueous suspension comprising (i) an ore, which is in the form of particles, (ii) water, (iii) a frothing agent mixture of at least 2 frothing agents, wherein one of the frothing agents is 2,4-diethyl-octane-1,5-diol or a distillation residue derived from the manufacturing pro- cess of 2-ethylhexanol comprising 2,4-diethyl-octane-1,5-diol and at least one of the other frothing agents is not comprised in such distillation residue, which is selected from methyl isobutyl carbinol, a distillation residue obtained by hydro-formylation of 1-propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol in a flotation cell to obtain a provided aqueous suspension, (B) introducing air into the provided aqueous suspension to obtain a froth.

Description

MIXTURES OF FROTHING AGENTS FOR FLOTATION OF ORES

The present invention relates to ore beneficiation technologies in the mining industry. More specifically, the present invention relates to beneficiation compositions used in flotation processes, especially mixtures of frothers, and methods of using the same.

The present invention relates to beneficiation compositions, comprising especially mixtures of frothers characterized in that at least one of the frothing agents is 2,4-diethyloctane-1 ,5-diol derived or isolated from or comprised in a distillation residue derived from the manufacturing process of 2-ethylhexanol, and at least one of the other frothing agents is not comprised in such distillation residue and is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1 -propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB). .

The present invention especially relates as well to the use of 2,4-diethyloctane-1 ,5-diol compound, preferably obtained from or comprised in a distillation residue derived from the manufacturing process of 2-ethylhexanol, in compositions and application methods as foaming or frothing agents in ore and flotation processes, as well as in other industrial processes involving froth flotation.

BACKGROUND OF THE INVENTION

In the mining industry beneficiation is any process that improves (benefits) the value of the treated ore by removing the gangue minerals, which results in a higher-grade product (ore concentrate) and a waste stream (tailings). There are many different types of beneficiation, with each step furthering the concentration of the original ore. Commonly, beneficiation by froth flotation uses the difference in the hydrophobicity (natural or imparted) of the respective components Froth flotation is a process for separating fine solids from other solids by making use of the disparity in hydrophobicity of solid particle-surfaces. This leads to separation of a solid mixture by selective attachment of hydrophobic solid particles to gas bubbles, mostly air, which is generally passed through a liquid (usually water)-ore mixture (slurry) of the crude solids at such a rate as to provide a sustained "froth" or accumulation of bubbles at the slurry-froth surface interface. The density difference between the gas bubbles (loaded with hydrophobic particles) and slurry causes the lifting of the hydrophobic solid particles to the surface and leaving behind non-hydro- phobic (hydrophilic) solids in the (aqueous slurry) bulk liquid mixture. The hydrophobic solid particles at the surface remain attached to the surface froth and can be subsequently separated - by draining the bulk mixture or mechanically skimming the surface froth.

More precisely, during this process, the treated mineral ore is comminuted to a certain small particle size and slurried with water, and the slurry is introduced into a flotation apparatus purged with air. The floated particles are collected, dewatered, and accumulated as a sellable I further processable final product. The hydrophilic particles tend to migrate (settle) to the bottom of the contact vessel from where they can be removed as tailings and processed into waste impoundments. In other processes, such as reverse flotation, the sellable final product may migrate to the bottom. For example, during silica flotation processes, the desired product can sink to the bottom of the slurry and the waste product can rise to the top of the slurry, or in iron ore beneficiation, where often a reverse flotation process is used to separate silica, the silica is skimmed off as froth whereas enriched iron ore settles down in the flotation cell and is further processed as iron ore concentrate.

In order to facilitate this process, several types of conventional reagents are used such as frothers, collectors, promoters and conditioners.

Generally, in froth flotation a frothing or foaming agent is added to stabilize the bubbles which carry the hydrophobic solid particles to the surface. The stabilization of the bubbles or surface froth greatly enhances the separating efficiency of the unwetted hydrophobic particles from the bulk liquid-solid mixture. Most frothing agents or "frother" act by stabilizing the bubbles presumably through the lowering of the liquid surface tension thereby enhancing the performance of - froth flotation processes. Dissolved salts seem to increase as well bubble stability and to reduce bubble size similar to frothers. "Stabilization" in relation to flotation refers to both the increased lifetime of the bubbles and the increased bubble specific surface area generated by lowering the average bubble size.

Froth flotation techniques have been used in the mining industry for more than a century. Many different minerals and non-minerals are processed using froth flotation. These include for example silver, nickel, zinc, titanium, cobalt, and chromium (metals) as well as quartz and kaolinite (non-metals). Nowadays it has become more and more difficult to find high grades of ore. Accordingly, there is a growing demand to provide more effective separation processes for poorer grades of ore. Consequently, there is a constant need for improvements in froth flotation techniques as well as for effective frothing agents.

A frother must possess a number of key properties and must be suitable and adjusted for different applications. Nevertheless, in general terms, a good frother must always be able to promote the formation of stable air bubbles under aerated conditions. Thus, frothers are typically comprised of polar and non polar components. The non-polar or hydrophobic moiety will orient itself into the air phase while the polar or hydrophilic component will tend to the liquid (usually water) phase. The result is an enhanced bubble wall strength and stability due to localized increase in surface tension. This will enhance the ability of the bubbles to hold and concentrate the desired mineral.

The stabilization of the bubbles or the formed surface froth (generally referring to the three phases air vs water vs particles) enhances further the separating efficiency of the hydrophobic particles from the liquid bulk mixture of solids. Therefore, characteristics of a generated foam (generally referring to the two phases air vs water) are important for a success of the flotation method. Several different classes of chemicals have been utilized as foaming agents in froth flotation methods of ores. The requirements discussed hereinabove results in that very often frothers contain a minimum number of carbon atoms (e.g. at least 5) in a straight chain or branched configuration which provide the hydrophobic interaction with the air phase and a polar group which is typically a hydroxyl (-OH) functionality. The balance of these two functionalities will determine the effectiveness of a particular frother for a particular application. Typical frothers include for example aliphatic alcohols like 2-ethyl-3-hexanol, cyclic alcohols (for example, pine oil), 1 ,1 ,3 -triethoxy- butane, and polyalkylene glycols.

One of the most commonly used all purpose flotation frothers for coal, base metal and other non-metal flotation is 4-methyl-2-pentanol, commonly known as "MIBC" (methyl isobutylcarbinol), which displays excellent surface behaviour, especially in applications where the minerals are relatively hydrophobic and readily floatable.

WO 2008/157613 discloses e.g. a method of separating a first material from a second material such, wherein a beneficiation composition is applied, which comprises a methyl isobutyl carbinol mixture derived from a methyl isobutyl ketone and/or methyl isobutyl carbinol manufacturing process.

However, although MIBC has excellent solvency and a relatively high boiling point, it has a flash point of 41°C (106°F). MIBC also emits an unpleasant odour and accordingly is not very pleasant to work with. MIBC is classified as a dangerous good according to the National Standard for the Storage and Handling of Workplace Dangerous Goods [NOHSC; 1015(2001)] and the National Code of Practice: Storage and Handling of Workplace Dangerous Goods [NOHSC: 2017(2001)] and accordingly, requires special care when handled, transported or stored in large volumes. Consequently, this compound poses a substantial occupational, health and safety (OH&S) concern. It is apparent from this that a need exists for a less volatile alternative to MIBC, that has better flammability and odour characteristics and is generally safer to deal with in general use. Optionally, the combination of MIBC with specific other frothing agents may led to reduce its share in compositions, thereby reducing its risks and disadvantages while still maintaining or even improving the frothing efficacy of said composition.

WO 2004/052815 in search for alternatives to MIBC found that C3-C9 secondary alcohols having a low degree of ethoxylation have the ability to act as effective frothers, and also have the added advantage of possessing higher flash points over the parent alcohols, from which they derive, making them less flammable and less volatile.

WO 2010/097165 describes a method for separating insoluble components from sylvinite, wherein a foaming agent is applied comprising an ether and/or ester, wherein the ether has linear or branched alkyl or alkenyl groups having 1- respectively 2 - to 30 carbon atoms; the ester is derived from monovalent or multivalent alcohols having 1 to 30 carbon atoms (alcohol radicals); or the ethers and/or esters are cyclic, wherein the ring size is 6 to 30 carbon atoms. Nevertheless, as mentioned above, as each frother must possess a number of key properties but must as well be suitable and adjusted for different applications, there is constant need for a variation of frothing agents for flotation of ore to be selected from. As diverse and individual each mine is presenting itself, as diverse and individually developed the applied agents and compositions needs to be. One fits all is rarely the case.

Hence, a mixture of different frothers may therefore address the heterogeneous challenges in the beneficiation process.

Another aspect generally playing into part as well is the desire to optionally reduce the amount of individual chemicals in a flotation method. Synergistic effects of combinations can lead to a higher efficacy while requiring less of the individual component.

A mixture of frothing agents, which provides a well-suited performance, e.g. regarding froth height, recovery rate or selectivity versus an undesired component, is desirable. A frothing agent mixture, which supports a flotation method towards an improved recovery rate of a desired value component or an improved selectivity versus an undesired component, is especially desirable. These technical effects might be caused or supported by a smaller gas bubble size, which provides a larger bubble surface area at a given foam volume, by a reduced coalescence of once formed gas bubbles respectively an increased lifetime of the once formed gas bubbles or a lower content of water of the foam.

SUMMARY OF THE INVENTION

It has now been surprisingly found that frothing agent mixture of at least 2 frothing agents, which is characterized in that one of the frothing agents is 2,4-diethyloctane-1 ,5-diol derived or isolated from or comprised in a distillation residue derived from the manufacturing process of 2- ethylhexanol and at least one other frothing agents not comprised in such distillation residue, which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1 -propene, or an isomer mix of dipropylene glycol monobutyl ether with butoxy dipropanol (DPnB), shows excellent performance with regard to flotation and improves the efficacy of the mixture compared to its individual components.

It has further been found a method for flotation of an ore, which comprises the steps of

(A) providing an aqueous suspension comprising

(i) an ore, which is in the form of particles,

(ii) water,

(iii) a mixture of at least 2 frothing agents in a flotation cell to obtain a provided aqueous suspension,

(B) introducing air into the provided aqueous suspension to obtain a froth, characterized in that at least one of the frothing agents is 2,4-diethyloctane-1 ,5-diol derived or isolated from or comprised in a distillation residue derived from the manufacturing process of 2- ethylhexanol and at least one of the other frothing agents which is not comprised in such distillation residue and which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1 -propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB).

And it has been found that the distillation residue derived from the manufacturing process of 2- ethylhexanol comprising 2,4-diethyloctane-1 ,5-diol or the compound 2,4-diethyloctane-1 ,5-diol as such can be used to enhance the efficacy of other frothing agents, which are not comprised in such distillation residue. The compound 2,4-diethyloctane-1 ,5-diol may be derived or isolated from said distillation residue derived from the manufacturing process of 2-ethylhexanol, or it may be chemically synthesized.

Especially preferred is a distillation residue comprising 2,4-diethyloctane-1 ,5-diol obtained from the manufacturing process of 2-ethylhexanol with CAS Number: 68609-68-7.

One commercially available product of such distillation residue is Oxooil 800.

Although frothing agent mixtures comprising the distillation residue according to the present invention, have already a significantly enhanced efficacy, the efficacy can be further improved, if the content of one of its key component, the 2,4-diethyloctane-1 ,5-diole, is enriched.

However, as such further processing of the distillation residue is of less economic value, significant improvements can already be obtained, if the distillation residue derived from the manufacturing process of 2-ethylhexanol and comprising the 2,4-diethyloctane-1 ,5-diole is used in the method according to the present invention.

The preparation of 2,4-diethyloctane-1 ,5-diole as such has been described in JP052299730, and, starting from butyraldehyde, in DE10251311.

The compound 2,4-diethyloctane-1 ,5-diole has been widely described for use in film-forming, coating or painting composition, as well as in dispersion formulations, such as in DE19924674, DE19855116, W02001056978, W02000026312 and W02001058903.

It is mentioned as binder for coatings and adhesives in EP940459 and WO2001085820, as hydrophobic additive in dispersions in WO202064652 and as reactive diluents in DE 19826715. It has been described as well for the preparation of (meth)acrylic acids and esters in W02007020200 and US20060009589.

However, from the listed state of the art above it becomes apparent, that none of the art mentioned above is related in any way to the technological field of extraction of ore and flotation, not to mention that its efficacy in froth flotation has ever been discussed.

Distillation residues in general have been described for flotation purposes in the art.

WO 2008157613 discusses mixtures with methyl isobutyl carbinol, one of the most popular frothers. In example 1 the beneficiation composition of WO 2008157613 comprises a blend of the MIBC mixtures and 1-propene hydroformylation product. The 1 -propene hydroformylation product is distillation residue comprising a mixture of the C4 - C8 alcohols such as 2-ethylhexan-1-ol, 2-ethylhexane-1 ,3-diol, iso-butyl and n-butyl alcohol; aldehydes such as 2-ethylhexanal, 2-ethylhex-2-enal and butyraldehyde, and esters, and is used as a frother in flotation operations.

W020201788262 relates to a process for the beneficiation of coal and other hydrophobic materials, wherein a collector composition comprises a distillation residue obtained by hydroformylation of octene isomers as a first component, which contains high boiling by-products from the manufacturing process of 2-ethylhexanol. As a second component diesel, kerosene and/or Cs- 20-olefins is used. 2,4-diethyloctane-1 ,5-diole is mentioned in form of a by-product resulting from the distillation of 2-ethyl-1 -hexanol. 2,4- diethyloctane-1 ,5-diol is also found in a frother composition. Nevertheless, neither the mixtures of 2,4-diethyloctane-1 ,5-diole or the distillation residue of 2-ethyl- 1 -hexanol with one other frothing agent not comprised in such distillation residue, is disclosed, nor the efficacy enhancing role of the distillation residue with regard to other frothers is discussed, not to mention the synergistic role of the 2,4-diethyloctane-1 ,5-diole is to be conveyed by the disclosure in W020201788262.

WO 2022/033868 discloses in one example a flotation process of copper ore with a binary mixture of frothing agents, wherein the frothing agent comprises 30% PolyTHF 250 and 70% of HBF-2EH. The distillation residue discussed herein above is mentioned as well. Although one example shows the use of a product obtained from distillation residues of the 2-ethylhexanol production process, the presence of 2,4- diethyloctane-1 ,5-diol and its specific combination with individually defined other frothing agents according to the present invention is not anticipated.

WO 2021/140166 discloses a flotation process to enrich apatite, a phosphate ore, contained in a multi-mineral composition, in an aqueous pulp comprising among others parts of a heavy distillation fraction from the industrial manufacturing of 2-ethylhexanol as a froth regulator with parts of distilled tall oil fatty acid as main collector and an amount of a co-collector being a combination of ethoxylated isotridecanols (iC13-3EO/iC13-1 OEO) or isotridecanol/ethoxylated isotridecanol (iC13-OEO/iC13-1 OEO). Although a product obtained from distillation residues of the 2-ethylhexanol production process is mentioned, the presence of 2,4- diethyloctane-1 ,5-diol and its specific combination with individually defined other frothing agents according to the present invention is not anticipated

WO 2016/008554 discloses a beneficiation process of metal sulfides by froth flotation using a stable aqueous emulsion comprising a water-insoluble thionocarbamate collector, water, one or a mixture of surface active agents of a general alcohol/phenol alkoxylate formula and a mixture of at least one alcohol and at least one ether and/or ester. Although a product obtained from distillation residues of the 2-ethylhexanol production process is discussed and claimed, the presence of 2,4- diethyloctane-1 ,5-diol and its specific combination with individually defined other frothing agents according to the present invention is not anticipated. The 2-ethyl-1 -hexanol as such has been described in methods of the mining industry. W02010097165 claims a process for separating insoluble matter from sylvite by suspending the sylvinite in saturated brine, adding a flocculating agent to the suspension, and then adding to the resulting composition a frother comprising at least one ether and I or ester. It is further mentioned therein that the foaming agent may contain in addition to the ether I or ester, at least one alcohol bearing a hydrocarbon radical of from 6 to 16 carbon atoms, and I or at least one polypropylene glycol, wherein, the alcohol may be a mono alcohol or a diol such as 2-ethylhexanol and 2-ethylhexane-1 ,3-diol (1 , 3). However, no further elaboration in that matter is to be found.

WO 2015/050807 describing “Frothers for Mineral Flotation” discusses methods and compositions for improving a froth flotation type separation. The methods use a microemulsion to improve the effectiveness of a frother, wherein the frothers discussed therein include among others aliphatic alcohols such as MIBC (methyl isobutyl carbinol), polyglycols and polyglycol ethers, polypropylene glycol ethers and commercially available alcohol blends such as those produced from the production of 2-ethylhexanol and any combination thereof.

In comparison WO 2015/050808 from the same applicant describes “Collectors for Mineral Flotation” and discusses also methods and compositions for improving a froth flotation type separation using a microemulsion to improve the effectiveness of a collector. Commercially available alcohol blends such as those produced from the production of 2-ethylhexanol are mentioned as well, but - also here as in WO 2015/050807- no further elaboration in that matter is to be found. Both publications emphasize the use of a microemulsion formulation type for mineral flotation, remaining silent on the technical effects of a distillation residue derived from the manufacturing process of 2-ethylhexanol.

Finally, going towards a totally different kind of derivatization, according to WO 2004/052815 it was found and described that C3-C9 secondary alcohols having a low degree of ethoxylation have the ability to act as effective frothers, and also have the added advantage of possessing higher flash points over the parent alcohols, from which they derive, making them less flammable and less volatile. These compounds would also display better odour characteristics than the parent alcohols.

Summarizing the state of the art in this regard, it can be stated, that although distillation residues may have been mentioned in singular cases for flotation, their effective and synergistic use in combination with other frothers has not yet been described as a general inventive concept.

DETAILED DESCRIPTION OF THE INVENTION

The froth height of a generated foam is an indicator of its stability. A stable foam will rise higher due to a higher stability of the bubbles (reduction in bubble coalescence). A bubble, which is more stable respectively possesses a higher strength, which in turn provides a higher probability of supporting a coarse particle (resistance to bubble deformation). An ore, which is in the form of chunks, for example after being mined, is transformed into the form of particles by crushing and/or grinding. A mill for grinding of hard rocks is for example a planetary ball mill, especially at laboratory scale. An ore, which is already in the form of loosely aggregated particles, is transformed into the form of particles by gentle disintegration. Preferably, the ore, which is in form of particles, is not treated with an organic coating or a coating in general, before getting in contact with the water and the frothing agent mixture. Preferably as well, the surface of the ore, which is in the form of particles, is not reacted with a chemical reagent before getting in contact with the water and the frothing agent mixture.

And finally, the surface of the ore, which is in the form or particles, is preferably not grafted with a chemical reagent before getting in contact with the water and the frothing agent mixture.

The particle size of the particles of the ore can be determined by ASTM E276-13, i.e. “Standard test method for particle size or screen analysis at No. 4 (4.75-mm) sieve and finer for metalbearing ores and related materials”.

Preferably, 80 wt.% of the ore particles pass a 500 pm sieve, very preferably a 400 pm sieve, particularly a 300 pm sieve, very particularly a 250 pm sieve and especially a 150 pm sieve. Preferred is a method, wherein at least 80 percent by weight of the ore particles pass a 500 pm sieve.

Preferably, the ore comprises a first mineral. The first mineral consists of an inorganic salt, which has an anionic part and a cationic part. The first mineral can be classified based on one contained chemical element, often a metal forming at least part of the cationic part of the inorganic salt or based on a contained assembly of more than one chemical elements, often an assembly of non-metals forming at least part of the anionic part of the inorganic salt. Accordingly, a specific first mineral can be classified into two or more specific classes out of a list of mineral classes at the same time. In such a list, the specific mineral is a combined mineral. For example, chalcopyrite (CuFeS2) is a copper mineral, an iron mineral and a sulfide mineral at the same time. It is in this meaning a combined mineral, i.e. a copper-iron-sulfide mineral. The first mineral is for example a sulfide mineral (chalcopyrite: CuFeS2; galenite: PbS; sphalerite: ZnS; cinnabarite: HgS), a phosphate mineral (apatite: Cas[(F,OH,CI)/(PO4)3), a silicate mineral (Nepouite: (Ni,Mg)6[(OH)sSi40io]; beryll: BesAh SiCh spodumene: LiAI(SiC>3)2), a carbonate mineral (magnesite: MgCCh), a fluoride mineral, a chloride mineral, an oxide mineral (chromite: (Fe,Mg)Cr2C>4; cassiterite: SnCh), a copper mineral (chalkosine: CU2S; bornite: CusFeS4), a molybdenum mineral (molybdaenite: M0S2), a zinc mineral (smithsonite: ZnCCh), a lead mineral (cerussite: PbCCh), a nickel mineral (pentlandite: (Fe.NQgSs), an iron mineral (magnetite: FesOt; hematite: Fe2Os; siderite: Fe[CC>3]; goethite: FeO(OH)), a manganese mineral (pyrolusite: MnCh; psilomelane: (Ba, FW^MnioCho), a titanium mineral (rutil: TiC>2, ilmenite: FeTiCh), a cobalt mineral (skutterudite: (Co,Ni)As3; cobaltite: CoAsS; coltan: (Fe,Mn)(Nb,Ta)2Oe), a tungsten mineral (wolframite: (Fe,Mn)WC>4, scheelite: CaWOt), a vanadium mineral (vanadinite: Pbs(VO4)3CI; carnotite: K₂(UO2)(VO4)2-3H₂O), a tin mineral (stannite: Cu2FeSnS4), an aluminium mineral (bauxite: AI(OH)3, gibbsite: AI(OH)3, boehmite: gamma-AIO(OH), diaspore: AIO(OH)), a lithium mineral (amblygonite: LiAI[PC>4] F, lepidolith: K(Li,AI)3[(AI,Si)4O ](F,OH)2), a scandium mineral, a yttrium mineral, a lanthanum mineral, a cerium mineral (bastnaesite: (Ce,La,Y)(CC>3)F or (Ce,La,Y)(CC>3)(OH,F)), a praseodymium mineral, a neodymium mineral (monazite: (La,Ce,Nd,Sm)[PO4]), a samarium mineral, an europium mineral, a gadolinium mineral, a terbium mineral, a dysprosium mineral, a holmium mineral, an erbium mineral, a thulium mineral, a ytterbium mineral, a lutetium mineral, a ruthenium mineral, a rhodium mineral, a palladium mineral, a silver mineral (argentite: Ag2S), an osmium mineral, an iridium mineral, a platinum mineral (sperrylith: PtAs2) or a gold mineral (calaverite: AuTe2).

Preferably, the first mineral is a sulfide mineral, a phosphate mineral, a silicate mineral, a carbonate mineral, a fluoride mineral, a chloride mineral, an oxide mineral, a copper mineral, a molybdenum mineral, a zinc mineral, a lead mineral, a nickel mineral, an iron mineral, a manganese mineral, a titanium mineral, a cobalt mineral, a tungsten mineral, a vanadium mineral, a tin mineral, an aluminium mineral, a lithium mineral, a scandium mineral, a yttrium mineral, a lanthanum mineral, a cerium mineral, a praseodymium mineral, a neodymium mineral, a samarium mineral, an europium mineral, a gadolinium mineral, a terbium mineral, a dysprosium mineral, a holmium mineral, an erbium mineral, a thulium mineral, a ytterbium mineral, a lutetium mineral, a ruthenium mineral, a rhodium mineral, a palladium mineral, a silver mineral, an osmium mineral, an iridium mineral, a platinum mineral, a gold mineral or a combined mineral, which has a chemical composition assigning the combined mineral to two or more of the aforementioned minerals at the same time.

Very preferably, the first mineral is a sulfide mineral, a phosphate mineral, a silicate mineral, a carbonate mineral, a fluoride mineral, a chloride mineral, a copper mineral, a molybdenum mineral, a zinc mineral, a lead mineral, a nickel mineral, an iron mineral, a scandium mineral, a yttrium mineral, a lanthanum mineral, a cerium mineral, a praseodymium mineral, a neodymium mineral, a samarium mineral, an europium mineral, a gadolinium mineral, a terbium mineral, a dysprosium mineral, a holmium mineral, an erbium mineral, a thulium mineral, a ytterbium mineral, a lutetium mineral, a ruthenium mineral, a rhodium mineral, a palladium mineral, an osmium mineral, an iridium mineral, a platinum mineral, a gold mineral or a combined mineral, which has a chemical composition assigning the combined mineral to two or more of the aforementioned minerals at the same time.

Particularly, the first mineral is a sulfide mineral, a phosphate mineral, a silicate mineral, a carbonate mineral, a fluoride mineral, a copper mineral, a molybdenum mineral, a zinc mineral, a lead mineral, a nickel mineral, an iron mineral, a gold mineral or a combined mineral, which has a chemical composition assigning the combined mineral to two or more of the aforementioned minerals at the same time.

Very particularly, the first mineral is a sulfide mineral, a phosphate mineral, a copper mineral, a gold mineral or a combined mineral, which has a chemical composition assigning the combined mineral to two or more of the aforementioned minerals at the same time.

Preferred is a method, wherein the ore comprises a first mineral, which is a sulfide mineral, a phosphate mineral, a silicate mineral, a carbonate mineral, a fluoride mineral, a chloride mineral, an oxide mineral, a copper mineral, a molybdenum mineral, a zinc mineral, a lead mineral, a nickel mineral, an iron mineral, a manganese mineral, a titanium mineral, a cobalt mineral, a tungsten mineral, a vanadium mineral, a tin mineral, an aluminium mineral, a lithium mineral, a scandium mineral, a yttrium mineral, a lanthanum mineral, a cerium mineral, a praseodymium mineral, a neodymium mineral, a samarium mineral, an europium mineral, a gadolinium mineral, a terbium mineral, a dysprosium mineral, a holmium mineral, an erbium mineral, a thulium mineral, a ytterbium mineral, a lutetium mineral, a ruthenium mineral, a rhodium mineral, a palladium mineral, a silver mineral, an osmium mineral, an iridium mineral, a platinum mineral, a gold mineral or a combined mineral, which has a chemical composition assigning the combined mineral to two or more of the aforementioned minerals at the same time.

Often, an ore comprises beneath a first mineral also a second mineral, which is different to the first mineral. Typically, an ore comprises a desired mineral(s) (= valuable) and an undesired mineral(s) (= gangue). An undesired mineral can consist essentially out of one mineral or can comprise a series of different undesired minerals. Similarly, a desired mineral can consist essentially out of one mineral or can comprise a series of different desired minerals. More often, the desired mineral consists essentially out of one mineral. Flotation is a method often used to increase the relative content of a desired mineral in a concentrate via separating from undesired parts of the ore. Accordingly, the ore is beneficiated. Arbitrarily, the first mineral might be considered the valuable mineral and the second mineral might be considered the undesired mineral. When the obtained froth is removed respectively separated from the flotation cell, for example by skimming of the surface of the provided aqueous suspension while air is introduced or shortly thereafter, i.e. prior to a significant collapsing of the obtained froth, then the removed respectively separated froth represents a froth concentrate. Without a continued introducing of air, the froth in the froth concentrate collapses successively. When the obtained froth is separated from the flotation cell, the remaining parts of the provided aqueous suspension form a cell concentrate. The cell concentrate remains in the flotation cell or is removed from the flotation cell, preferably at a location different to the location of the removal of the froth. For example, the cell concentrate is removed from the bottom of the flotation cell. In a continuous way of running of the method, a respective design to allow an underflow removal of the cell concentrate from the flotation cell is possible. Introducing of air may be continued until no more froth is formed. This might last for example for one minute or up to 15 or 20 minutes. Preferably, the method comprises additionally as step (C) separating the froth from the flotation cell to obtain a froth concentrate and a cell concentrate. It is possible that the weight ratio between the first mineral and the second mineral is higher in the obtained froth concentrate than the weight ratio between the first mineral and the second mineral in the obtained cell concentrate. If the first mineral is the desired mineral, then this is called a direct flotation. It is also possible that the weight ratio between the first mineral and the second mineral is lower in the obtained froth concentrate than the weight ratio between the first mineral and the second mineral in the obtained cell concentrate. If the first mineral is the desired mineral, then this is called an indirect flotation or a reverse flotation. At both possibilities, an enrichment occurs. At this enrichment, a high recovery of the desired first mineral with a high selectivity is targeted. A weight ratio between component (i), i.e. the ore, which is in the form of particles, and component (iii), i.e. the frothing agent mixture, is determined based on the dry weight of component (i). It typically takes only a small amount component (iii). For example, the amount of component (iii) in the aqueous suspension is in the range of 0.00001 to 0.1 parts by weight based on 100 parts by weight of component (i). This is equivalent to a dosage of component (iii) in the range of 0.1 to 1000 g / 1 of dry ore. Preferably, the amount of component (iii) in the aqueous suspension is in the range of 0.0001 to 0.05 parts by weight based on 100 parts by weight of component (i). This is equivalent to a dosage of component (iii) in the range of 1 to 500 g / 1 of dry ore. Very preferably, the amount of component (iii) in the aqueous suspension is in the range of 0.0005 to 0.025 parts by weight based on 100 parts by weight of component (i) (5 to 250 g / 1 of dry ore), particularly in the range of 0.0007 to 0.01 parts by weight (7 to 100 g / 1 of dry ore), very particularly in the range of 0.0008 to 0.007 parts by weight (8 to 70 g / 1 of dry ore), especially in the range of 0.0009 to 0.0045 parts by weight (9 to 45 g / 1 of dry ore) and very especially in the range of 0.001 to 0.0035 parts by weight (10 to 35 g / 1 of dry ore).

Preferred is a method, wherein the amount of component (iii) in the aqueous suspension is in the range of 0.0001 to 0.1 parts by weight based on 100 parts by weight of component (i). Preferred is a method, wherein the amount of component (iii) in the aqueous suspension is in the range of 0.001 to 0.05 parts by weight based on 100 parts by weight of component (i).

A weight ratio between component (i), i.e. the ore, which is in the form of particles, and component (ii), i.e. water, is determined based on the dry weight of component (i). Desired for economic reasons are highly concentrated aqueous suspensions, i.e. a pulp.

Preferably, the amount of component (ii) in the aqueous suspension is in the range of 70 to 1100 parts by weight based on 100 parts by weight of component (i). This is equivalent to a solids content of dry ore in the range of 58.8 wt.% to 8.3 wt.%, if the weight of any other component of the aqueous suspension different to component (i) and component (ii) is neglected for the calculation, i.e. set to zero.

Very preferably, the amount of component (ii) in the aqueous suspension is in the range of 100 to 900 parts by weight based on 100 parts by weight of component (i) (solids content of 50 wt.% to 10 wt.%), particularly in the range of 110 to 800 parts by weight of component (ii) (solids content of 47.6 wt.% to 11.1 wt.%), very particularly in the range of 120 to 600 parts by weight of component (ii) (solids content 45.5 wt.% to 14.3 wt.%), especially in the range of 130 to 420 parts by weight of component (ii) (solids content 43.5 wt.% to 19.2 wt.%) and very especially in the range of 150 to 400 parts by weight of component (ii) (solids content 40 wt.% to 20 wt.%).

Preferred is a method, wherein the amount of component (ii) in the aqueous suspension is in the range of 70 to 1100 parts by weight based on 100 parts by weight of component (i).

Preferably, the amount of component (iii) in the aqueous suspension is in the range of 0.0001 to 0.1 parts by weight based on 100 parts by weight of component (i) and the amount of component (ii) in the aqueous suspension is in the range of 70 to 1100 parts by weight based on 100 parts by weight of component (i).

The flotation cell is a container, which has an opening at its upper side and possesses a gadget to introduce air, which allows the introduced air to flow from the inner bottom side of the container finally to the opening. The opening is designed to allow a removal of froth from the surface. Optionally, the flotation cell comprises a stirrer, for example an impeller, which allows to stir a liquid content of the container. Optionally, the gadget to introduce air is integrated in the impeller. Preferably, the gadget to introduce air generates small bubbles when air is introduced, for example by many small orifices at the outlet of the gadget. For example, the outlet is a frit. Preferably, the gadget to introduce air is equipped with a rotameter. Optionally, the flotation cell is equipped with an automated system for removal of obtained froth.

In a dynamic system, ideally the froth should collapse as soon as it hits the launder Preferred is a method, wherein the ore comprises a first mineral and a second mineral, which is different to the first mineral.

For improvement of an enrichment of a desired mineral contained in the ore, a first flotation auxiliary, which is different to frother(s) according to the present invention, is a possible further component, i.e. component (iv), of the aqueous suspension. A collector attaches to the surface of the ore particles and is preferably a surface-active molecule. Ideally, the collector attaches to the surfaces with a different affinity for the surface of the target primary mineral and the surface of the gangue /further mineral. This leads to a different hydrophobicity of the minerals and hence a different affinity to the air bubbles. For a differentiation of the different possible flotation auxiliaries, it is herein defined that a surface-active molecule possesses a hydrophilic structural element and a lipophilic structural element, a merely hydrophilic molecule possesses only a hydrophilic structural element and a merely lipophilic molecule possesses only a lipophilic structural element. A collector can further be differentiated into an ionic collector, which is a surfaceactive ionic molecule, and a non-ionic collector, which is a non-ionic surface-active molecule. The ionic collector is an anionic surface-active substance, an amphoteric surface-active substance or a cationic surface-active substance. A depressing agent is a merely hydrophilic molecule and attaches to the surface of the ore particles and ideally with a different affinity for the surface of the first mineral and the surface of the second mineral. A possible additional frothing agent is a non-ionic surface-active compound, which supports the froth generating of the frothing agent mixture. An extender oil is a hydrocarbon, which is a merely lipophilic molecule, and ideally allows to reduce the necessary amounts of a collector. A pH-regulating substance is an acid or a base, which is preferably merely hydrophilic, and helps to keep an optimum pH-value of the aqueous suspension, since surface charges are often pH-dependent.

Dependent on the technical requirements, one or more flotation auxiliaries, which are all different to frother(s) according to the present invention, can be employed. In case there is more than one flotation auxiliary, the numbering is continued, i.e. a first flotation auxiliary, which is component (iv), and a second flotation auxiliary, which is component (v). In analogy a third flotation auxiliary is component (vi).

The first flotation auxiliary is for example a collector, a non-ionic surface-active compound, which is a non-ionic collector or a second frothing agent, a depressing agent, an extender oil or a pH-regulating substance. Preferably, the first flotation auxiliary is a surface-active collector, a non-ionic surface-active compound, which is a non-ionic collector or an additional frothing agent, a depressing agent, an extender oil or a pH-regulating substance.

Very preferably, the first flotation auxiliary is an ionic collector, a non-ionic surface-active compound, which is a non-ionic collector or an additional frothing agent, a depressing agent, an extender oil or a pH-regulating substance.

The ionic collector, which is an anionic surface-active substance, an amphoteric surface-active substance or a cationic surface-active substance, is chosen according to the targeted mineral. For a sulfide mineral, the first collector is for example an anionic surface-active substance, which is a xanthate (e.g. S=C(OR)-S" K⁺(Na⁺) with R being an aliphatic hydrocarbon chain, usually 2-5 carbon atoms), a dithiophosphate (e.g. S=P(OR)2-S" K⁺(Na⁺) with R being an aliphatic hydrocarbon chain, usually 2-5 carbon atoms), a dithiocarbamate (e.g. S=C(NR¹R²)-S" K⁺(Na⁺) with R¹ and R² being an aliphatic hydrocarbon chain), a dixanthogene (e.g. S=C(OR)-S-S- C(=S)OR with R being an aliphatic hydrocarbon chain, usually 2-5 carbon atoms), an alkyl thi- onocarbamate (e.g. R¹-NH-C(=S)(OR²) with R¹ and R² being an aliphatic hydrocarbon chain).

For a sulfide mineral, the first collector is for example a cationic surface-active substance, which is an alkyl thioether amine (e.g. R-S-CH2-CH2-NH2 with R being an aliphatic hydrocarbon chain) (for reference: S.R. Rao, chapter 10.1 “Collectors for sulfide minerals”, p. 479 f.) in Surface Chemistry of Froth Flotation, Springer Media, 2004).

For a phosphate mineral, the first collector is for example an anionic surface-active substance, which is a fatty acid, an alkyl sulfonate (for example an alkyl sulfosuccinate), an alkyl sulfate, an alkyl sarcosinate or an alkyl mono- or diester of phosphoric acid. For a phosphate mineral, the first collector is for example an amphoteric surface-active substance, which is a N-(alkyl)-glycine or a N(-3-alkyloxy-2-hydroxy-propyl)glycine.

For an iron oxide mineral, the first collector is for example a cationic surface active substance, which is an alkyl amine, for example a N-(alkoxypropyl) amine or a N’-(N-(alkoxypro- pyl)amino)propyl) amine, or an N-(alkylamido)alkylene diamine.

The non-ionic collector is for example an ethoxylated fatty acid, an ethoxylated fatty amide or an ethoxylated fatty alcohol.

The depressing agent is for example a hydrophilic polysaccharide, particularly a starch, or sodium silicate. The starch is for example a native starch or a modified starch. A native starch is for example a starch from corn, wheat, oat, barley, rice, millet, potato, pea, tapioca or manioc. The native starch is preferably pre-gelled, i.e. warmed for starch gelation. The pH-regulating substance is for example NaOH, Na2COs, KOH, K2CO3, HCI, H2SO4, H3PO4 or HNO₃.

EMBODIMENTS OF THE INVENTION

The frothing agents, which may be used as second and/or third frothing agent in the mixtures with the distillation residue derived from the manufacturing process of 2-ethylhexanol, respectively with 2,4-diethyloctane-1 ,5-diole as such, are selected from a group comprising a distillation residue obtained by hydroformylation of 1 -propene, from a distillation residue obtained by hydroformylation of C8-alkenes (octenes), from a cyclic terpene alcohol, methylisobutyl carbinol, a non-cyclic C6-C12 alcohol, an alcoholic aliphatic ester, triethoxybutane, an ethoxylated and/or propoxylated non-cyclic C1-C6 alcohol, an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol, poly(tetrahydrofuran), polyethylene glycol and/or polypropyl-ene glycol. Commercially available are for instance the distillation residue obtained by hydroformylation of 1 -propene as Oxo Oil 840, the distillation residue obtained by hydroformylation of C8-alkenes (octenes) as Oxo Oil 9N, the methylisobutyl carbinol (“MIBC”), resp. 4-methyl-2-pentanol as Flo- tanol® MTM, the isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (“DPnB”) as Solvenon® DPnB, poly(tetrahydrofuran, polyethylene glycol and polypropylene glycol at different molecular weights such as poly(tetrahydrofuran) (250MW) as PolyTHF® 250 or polypropylene glycol (230MW) as Pluriol® P230.

Preferred is a method, wherein at step

(A) the aqueous suspension comprises as first frothing agent (iii.1) the distillation residue derived from the manufacturing process of 2-ethylhexanol comprising 2,4-diethy- loctane-1 ,5-diole in its original quantity, and at least (iii.2) another frothing agent, which is not comprised in such distillation residue and which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1-pro- pene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB).

Another embodiment of the invention is a method, wherein at step

(A) the aqueous suspension comprising as first frothing agent (iii.1) the distillation residue derived from the manufacturing process of 2-ethylhexanol, which is enriched in its content of 2,4-diethyloctane-1 ,5-diole, meaning that further 2, 4-diethyloctane-1 , 5- diole has been added, and at least (iii.2) another frothing agent, which is not comprised in such distillation residue and which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1-propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB).

Another embodiment of the invention is a method, wherein at step

(A) the aqueous suspension comprises as first frothing agent the compound 2,4-diethy- loctane-1 ,5-diole (iii.1) isolated from a distillation residue derived from the manufacturing process of 2-ethylhexanol and at least (iii.2) another frothing agent, which is not comprised in such distillation residue and which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1-propene, or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB). Alternatively, the 2,4-diethyloctane-1 ,5-diole used in step A is obtained by synthesis.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.2) a second frothing agent a distillation residue obtained by hydroformylation of 1 -propene.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as (iii.2) a second frothing agent a methylisobutyl carbinol (MIBC).

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.2) a second frothing agent an isomer mix of dipropylene glycol monobutyl ether with butoxy dipropanol (DPnB),

Preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.3) a third frothing agent, which is not comprised in the distillation residue derived from the manufacturing process of 2-ethylhexanol, and which is different to first and second frothing agent, and which is selected from the group consisting of consisting of a distillation residue obtained by hydroformylation of 1-propene, a distillation residue obtained by hydroformylation of C8-alkenes (octenes), a cyclic terpene alcohol, methylisobutyl carbinol, a non-cyclic C6-C12 alcohol, an alcoholic aliphatic ester, triethoxybutane, an ethoxylated and/or propoxylated non- cyclic C1-C6 alcohol, an isomer mix of dipropylene glycol monobutyl ether with butoxy dipropanol, poly(tetrahydrofuran), polyethylene glycol and polypropyl-ene glycol.

More preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.3) a third frothing agent, which is not comprised in the distillation residue derived from the manufacturing process of 2-ethylhexanol, and which is different to first and second frothing agent, and which is selected from the group consisting of a distillation residue obtained by hydroformylation of 1-propene, a distillation residue obtained by hydroformylation of C8-alkenes (octenes), methylisobutyl carbinol, a non-cyclic C6-C12 alcohol, an alcoholic aliphatic ester, triethoxybutane, an ethoxylated and/or propoxylated non-cyclic C1-C6 alcohol, an isomer mix of dipropylene glycol monobutyl ether with butoxy dipropanol, poly(tetrahydrofuran), polyethylene glycol and polypropylene glycol.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as (iii.3) third frothing agent, which is different to first and second frothing agent, a distillation residue obtained by hydroformylation of 1 -propene.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.3) third frothing agent, which is different to first and second frothing agent, a distillation residue obtained by hydroformylation of C8-alkenes (octenes).

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.3) third frothing agent, which is different to first and second frothing agent, methylisobutyl carbinol (MIBC).

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.3) third frothing agent, which is different to first and second frothing agent, a poly(tetra- hydrofuran) with a number-average molecular weight M_n of 250.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprises in the mixture of frothing agents as

(iii.3) a third frothing agent, which is different to first and second frothing agent, an isomer mix of dipropylene glycol monobutyl ether with butoxy dipropanol (DPnB).

Preferred is a method, wherein at step

(A) the aqueous suspension comprising the mixture of frothing agents, the total content of 2,4-diethyloctane-1 ,5-diole within the mixture is at least 40 weight %.

Preferred is a method, wherein at step

(A) the aqueous suspension comprising the mixture of frothing agents, the total content of 2,4-diethyloctane-1 ,5-diole within the mixture is not higher than 90 weight %.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprising the mixture of frothing agents, the total content of 2,4-diethyloctane-1,5-diole within the mixture is between 45 and 85 weight %.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprising the mixture of frothing agents, the total content of 2,4-diethyloctane-1,5-diole within the mixture is between 50 and 80 weight %.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprising the mixture of frothing agents, the total content of 2,4-diethyloctane-1,5-diole within the mixture is between 55 and 75 weight %.

Especially preferred is a method, wherein at step

(A) the aqueous suspension comprising the mixture of frothing agents, the total content of 2,4-diethyloctane-1,5-diole within the mixture is between 60 and 70 weight %.

The aqueous suspension used in the method according to the present invention may not only comprise a (frothing agent mixture according to the present invention, but also other flotation auxiliary compounds, which are different to the frothers of the mixture. Preferred is a method, wherein at step

(A) the aqueous suspension comprises additionally

(iv) a first flotation auxiliary, which is different to frother(s) of the inventive mixture, and is a collector, a depressing agent, an extender oil or a pH-regulating substance.

Preferred is a method, wherein at step

(A) the aqueous suspension comprises additionally

(iv) a first flotation auxiliary, which is different to frother(s) of the inventive mixture and is a collector.

Preferred is a method, wherein at step

(A) the aqueous suspension comprises additionally

(iv) a first flotation auxiliary, which is different to frother(s) of the inventive mixture, and is an ionic collector, which is an anionic surface-active substance, an amphoteric surface-active substance or a cationic surface-active substance, a non-ionic surface active compound, which is a non-ionic collector, a depressing agent, an extender oil or a pH-regulating substance.

Preferred is a method, wherein the first flotation auxiliary is an ionic collector, which is an anionic surface-active substance, an amphoteric surface-active substance or a cationic surfaceactive substance.

Preferred is a method, wherein the first flotation auxiliary is different to frother(s) according to the present invention, and is a non-ionic surface-active compound, which is a non-ionic collector.

Preferred is a method, wherein at step

(A) the aqueous suspension comprises

(iv) a first flotation auxiliary, which is different to frother(s) of the inventive mixture and a ionic collector.

Preferred is a method, wherein at step

(A) the aqueous suspension comprises

(iv) a first flotation auxiliary, which is different to frother(s) of the inventive mixture and is an non- ionic collector.

At step (B), the provided aqueous suspension is preferably stirred during introducing of air. The provided aqueous suspension is preferably kept at atmospheric pressure during introducing of air. Atmospheric pressure means the pressure of the atmosphere at the surrounding of the flotation cell, i.e. barometric pressure, and this is achieved at least by the opening of the container being in exchange with the surrounding pressure. Hence, the head space in the flotation cell, i.e. the space above the upper surface of the aqueous suspension respectively above the upper surface of the froth on top of the aqueous suspension, has the pressure of the atmosphere surrounding the flotation cell. The provided aqueous suspension has preferably a temperature in the range of 0 °C to 50 °C, very preferably 2 °C to 40 °C, particularly 4 °C to 37 °C, very particularly 8 °C to 34 °C, especially 10 °C to 30 °C, very especially 12 °C to 26 °C and most especially at room temperature (around 20 °C).

Preferred is a method, wherein at step

(B) the provided aqueous suspension is stirred during introducing of air.

Preferred is a method, wherein at step

(B) the provided aqueous suspension is kept at atmospheric pressure during introducing of the air.

Preferred is a method, wherein at step

(B) the provided aqueous suspension has a temperature in the range of 0 °C to 50 °C during introducing of the air.

Preferred is a method, wherein the method comprises additionally the step

(C) separating the froth from the flotation cell to obtain a froth concentrate and a cell concentrate.

Preferred is a method, wherein at step (C) the weight ratio between the first mineral and the second mineral is higher in the obtained froth concentrate than the weight ratio between the first mineral and the second mineral in the obtained cell concentrate.

The above described preferences for the method for flotation of an ore are described for the method. These preferences apply also to the further embodiments of the invention, such as compositions, formulations and uses.

A further embodiment of the invention is an aqueous suspension comprising

(i) an ore, which is in the form of particles,

(ii) water, and

(iii) a frothing agent mixture, characterized in that in the frothing agent mixture of at least 2 frothing agents, one of the frothing agents is 2,4-diethyloctane-1 ,5-diol or a distillation residue derived from the manufacturing process of 2-ethylhexanol comprising 2,4-diethyloctane-1 ,5-diole, and at least one of the other frothing agents is not comprised in such distillation residue and which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1-propene, or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB), and wherein the amount of component (iii) in the aqueous suspension is in the range of 0.00001 to 0.1 parts by weight based on 100 parts by weight of component (i), and the amount of component (ii) in the aqueous suspension is in the range of 100 to 1000 parts by weight based on 100 parts by weight of component (i).

Preferably, the amount of component (iii) in the aqueous suspension is in the range of 0.0001 to 0.05 parts by weight based on 100 parts by weight of component (i). A further embodiment of the invention is a use of a frothing agent mixture as a component (iii) of an aqueous suspension, which comprises additionally (i) an ore, which is in the form of particles, and (ii) water, for generating froth in a flotation cell, when air is introduced into the aqueous suspension, characterized in that the frothing agent mixture is a mixture of at least 2 frothing agents, wherein one of the frothing agents is 2,4-diethyloctane-1 ,5-diol as such or a distillation residue derived from the manufacturing process of 2-ethylhexanol comprising 2,4-diethy- loctane-1 ,5-diol and at least one of the other frothing agents is not comprised in such distillation residue and which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1 -propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB).

Preferably, the use of the frothing agent mixture generates froth with a high froth height.

EXAMPLES

The following examples illustrate further the invention without limiting it. Percentage values are percentage by weight if not stated differently.

A) Agents

A.1) Collector/Collecting agent

“PAX” is Potassium Amyl Xanthate, the potassium salt of a Dithiocarbonic Acid Ester, also named Potassium O-pentyl carbonodithioate [CAS-No. 2720-73-2] with a molecular mass of 202.38. PAX is commercially available for example from Redox.

A.2) Frother/Frothing agents

“2-EH” is 2-Ethyl-1 -hexanol, also called iso-octylalcohol [CAS-No. 104-76-7], with a molecular mass of 130.23 g/mol is widely commercially available, for example from Sigma-Aldrich Ltd.

“MIBC” is methyl isobutyl carbinol, resp. 4-methyl-2-pentanol [CAS-No. 108-11-2], with a molecular mass of 88.1 g/mol, commercially available for example as Flotanol M™.

“DPnB” is dipropylene glycol monobutyl ether, Butoxy dipropanol, Isomer mix [CAS number 29911-28-2], with a molecular mass of 190.28 g/mol, commercially available as Solvenon® DPnB

“PPG-230” is Polypropylene Glycol (230MW) [CAS-No. 25322-69-4], which is a polymer of the monomer propylene glycol with a molecular weight of 230 g/mol and can be depicted as H(C3HeO)_nOH and is commercially available for instance as Pluriol® P230.

Poly THF 250 is a poly(tetrahydrofuran) resp. H(OCH2CH₂CH₂CH2)xOH [CAS-No. 25190-06-1] as depicted below with a number-average molecular weight M_n of 250. It is commercially available for example from Sigma-Aldrich Ltd. The grade commercially available from Sigma-Aldrich Ltd contains 2,6- di-tert-butyl-4-methyl-phenol as stabilizer in an amount below 0.05 wt.%.

POLYFROTH® H27C is a commercially available but not chemically identified flotation frother available from Huntsman Corp., which provides according to its technical data sheet “a good balance of selectivity and stability in a range of flotation processes, including copper-molyb- denum flotation. The product is practically insoluble in water”.

“DR-1 -Pro” corresponds to the distillate residues from the manufacture of butyraldehyde, which is the hydroformylation product(s) of 1 -Propene [CAS Number: 97281-08-8], to be found under the name of Oxo Oil 840.

“DR-2-EH” is the high-boiling fraction from 2-ethyl-1 -hexanol manufacturing process (HBF-2EH, distillation residues) [CAS 68609-68-7], which is a combination of hydrocarbons in the range of C4 through C16 produced by the distillation of products from a 2-ethyl-1 -hexanol manufacturing process and boiling in the range of 199°C to 308°C (390°F to 586°F), and is commercially obtainable for example under the following trade names as Oxo Oil 800, Montanol® 800, Octyl alcohol F, Oktanol F or Zorgol 8 . In the respective process, butyraldehyde is first enalized with aqueous sodium hydroxide solution to 2-ethylhexenal. After reprocessing, the conjugated aldehyde is hydrogenated to 2-ethylhexanol. The distillation residue of 2-ethylhexanol (DR-2-EH) comprises 2,4-diethyloctane-1 ,5-diol. Based on GC analytics, the average percentage of 2,4- diethyloctane-1 ,5-diol present is about 40% to 45% (w/w), optionally it may be up to 52%. For the calculation in the following examples a content of 40% (w/w) 2,4-diethyloctane-1 ,5-diol was presumed in DR-2-EH.

“DR-Oct” is the high boiling fraction of distillate residues obtained by hydroformylation of C8-al- kenes (octenes) [CAS Number: 68526-89-6], to be found under the name of Oxo Oil HS 9 or Oxo Oil 9N.

“1 ,5-diol” is 2,4-diethyloctane-1 ,5-diol [CAS-No. 94277-83-5] is one of the components of DR-2- EH (see above). It can be obtained by distillation of DR-2-EH, which is to be understood by “derived from” or “isolated from”, as it remains in its distillation residue. It is as well commercially available.

For the purpose of the present invention, 2,4 Diethyl 1 ,5 octandiol was obtained by fractionated batch distillation (performed in glass column) of 2-Ethylhexanol (2-EH) bottoms stream. The 2 EH bottoms starting samples used for the fractionated distillation were obtained from DR-2-EH (Oxo oil 800®) and seven fraction samples were separated. 2,4 Diethyl 1 ,5 octandiol is a high boiler component (vapour pressure of 0.0±1 .3 mmHg at 25°C) in the 2 EH bottoms stream, hence the distillation parameters were adjusted to high vacuum (7 8 mbar abs (heads)), whereby incrementally increasing temperature and adjusting reflux ratio, starting at 2:1. In the following, reflux ratio was increased from 3:1 to 10:1. When 120 C heads temperature was measured and a reduction to 5:1 was chosen for the 6th and 7th sample. In the 7th fractioned sample obtained at 137 C and 8 mbar abs, 2,4 Diethyl 1 ,5 octandiol could be retrieved with a purity grade of 99%.

However 2, 4-diethyloctane-1 ,5-diol can as well be commercially sourced from Pharmaffiliates (https://www.pharmaffiliates.com/en/94277-83-5-2-4-diethyloctane-1-5-diol-pa270019198.html).

A.3) Other agents

Hydrated lime is a powder made when quicklime (CaO) is reacted with water to form hydrated lime (Ca(OH)2). Hydrated lime (Ca(OH)2 [CAS No. 1305-62-0] is commercially available from Millipore Sigma.

The agents were used in the following examples as indicated or as the respective mix- tures/blends as depicted in the tables showing the results.

B) Methodology and conditions

B.1 Flotation of copper ore

The following methodology describes the conditions for each test with copper ore.

Procedure:

1 . A homogenised 1 kg portion of copper ore was milled in a laboratory rod mill to achieve an 80% passing size of 106 microns. The grind was conducted with hydrated lime (500g/t) and 10g/t collector Potassium Amyl Xanthate (PAX).

2. The milled slurry (conducted at 50% solids) was then transferred to a flotation cell (Denver D12, cell size 2.5L) where the resulting density was 34% solids. Agitation speed was set at 900RPM.

3. Additional hydrated lime was added to maintain the pH of 11.0.

4. 10g/t of collector (PAX) was added and conditioned for 3 minutes.

5. 10g/t of the respectively selected testing frothing agent was added and conditioned for 1 minute

6. Flotation was conducted 1 minute with concentrate being recovered after every 10 seconds for 1 minute into tray 1 (Con 1 - stage 1). Flotation was continued for a further 2 minutes and concentrate being recovered into tray 2 (Con 2 - stage 2).

7. Air was stopped, and while agitating additional 10g/t collector was added and conditioned for 2 minutes. Additional 10g/t frothing agent was added and conditioned for a further 1 minute. Flotation was carried out with concentrate being recovered after every 10 seconds for 3 minutes into tray 3 (Con 3 - stage 3)

8. Air was stopped and additional 10g/t frothing agent added and conditioned for 1 minutes. Flotation was conducted with concentrate being recovered after every 10 seconds for 4 minutes into tray 4 (Con 4 - stage 4) 9. In total the selected frothing agent was added at 10g/t for stages 1 , 3, and 4, totalling in an amount of 30g/t.

10. The total flotation time over 4 stages 10 minutes (1 , 3, 6, 10 cumulative flotation time).

11 . Concentrates and tailings were dried at low temperature, weighed, and assayed for copper content.

B.2 Flotation of gold ore

The following methodology describes the conditions for each test with gold ore.

Procedure:

1 . A homogenized 2kg portion of gold ore was milled in a rod mill to achieve 80% particles passing 150 microns.

2. The milled ore (conducted at 50% solids in sea water) was then transferred to a 4L Denver flotation cell and filled to the mark with sea water to obtain 30% solids. The impeller agitation speed was set at 800RPM.

3. At this stage, reagents were added to condition: a. 120g/t CuSC>4 was added and conditioned for 5 minutes. b. As collector potassium amyl xanthate (PAX) was added at 150g/t and conditioned for 2 minutes. This step was repeated multiple times as described herein below.

4. Flotation was conducted for 2 minutes while scrapping or recovering concentrate after every 10 seconds. A first sample (“Concentrate 1”) was collected.

5. Additional collector PAX at 25 microliters was added at 30g/t and conditioned for 1 minute.

6. Flotation was conducted for 5 minutes while scrapping or recovering concentrate after every 10 seconds. A second sample (“Concentrate 2”) was collected.

7. Additional collector PAX at 25 microliters was added this time at 20g/t and conditioned for 1 minute.

8. Flotation was conducted for 8 minutes while scrapping or recovering concentrate after every 10 seconds. A third sample (“Concentrate 3”) was collected.

9. Additional collector PAX at 25 microliters was added at 20g/t and conditioned for 1 minute.

10. Flotation was conducted for 10 minutes while scrapping or recovering concentrate after every 10 seconds. A fourth sample (“Concentrate 4”) was collected.

11 . The 4 concentrates samples and the tailings were low temperature dried, weighed, and assayed for gold, and optionally sulphur.

C) Results

Table C.l: Recovery values and grades of single frother components (100%) regarding copper: ^b) comparative values of single components

It can be seen that from the known frothers, the bottoms distillate DR-2-EH shows the best results for copper, which is reached with regard to copper recovery only by the use of one of its single components, namely the pure 2,4-diethyloctane-1 ,5-diol, when tested solely as frothing agent.

In comparison others pure and known frothers (MIBC, DPnB and 2-EH) are tested, as well as the bottoms distillate DR-1 -Pro.

Table C.l I : Recovery values and grades of single frother components (100%) regarding gold: ^b) comparative values of single components

For gold, best value is shown for 2-EH, which is as well a portion of DR-2-EH, nevertheless, here the pure 2,4-diethyloctane-1 ,5-diol shows the best gold recovery.

In comparison other pure and known frothers (MIBC, H27, Poly-THF, DPnB and 2-EH) are tested, as well as the bottoms distillates DR-1 -Pro and DR-Oct.

C.1 Results of copper flotation with frother mixtures according to the invention

The flotation results are shown below in Tables C.1.1.1 , C.1.1.2, C.1.1.3 and C.1.1.4.

Example 1 : Enhancement of frothing efficacy of frother compounds by addition of

2,4-diethy-loctane-1 ,5-diol Table C.1.1 (Comparative recovery values and grades of single components on copper) ^b) comparative values of single components

Table C.1.2 (Recovery values and grades of comparative/inventive mixtures on copper) Footnotes: ^a) according to invention c) for illustrative purpose: DR-2-EH with added 2,4-diethyloctane-1,5-diol (in total 64% (w/w) 2,4-diethyloctane-1 ,5-diol, under the presumption of 40% (w/w) content in DR-2-EH)

*) comprising 2,4-diethyl-octane-1,5-diol

Table C.1.1 displays the copper recovery rate and grade of single components, and Table C.1.2 for mixtures of 2,4-diethyloctane-1,5-diol with the different frothers.

Not only the efficacy of a classical frother such as MIBC can be improved, also the efficacy of its original source, meaning the overall distillation residue DR-2-EH, can be improved (see ^c) for il- lustration purpose).

Also, for the distillation residue DR-1 -Pro an improvement of efficacy could be demonstrated. At a higher percentage rate of 2,4-diethyloctane-1,5-diol, the performance is affected as the synergistic effects becomes weaker. Thus, the weight concentration of overall 2,4-diethy- loctane-1,5-diol needs to be within a certain range, preferably below 80 wt %, as the efficacy diminish at higher concentration ranges probably due to higher viscosity, which can be seen at the 100 % wt value. High viscosity of individual components of a composition may as well cause formulation issues, thereby affecting their efficacy.

Table C.1.3: Flotation Results for ternary mixtures of DR-2-EH with DPnB and MIBC

Footnotes: a) according to invention b) comparative:

*) comprising 2,4-diethyl-octane-1,5-diol

Table C.1.4.: Flotation Results for binary mixture of DR-2-EH with DPnB

Footnotes: a) according to invention b) comparative

*) comprising 2,4-diethyl-octane-1,5-diol

Summary: It can be seen in all examples presented above, that the efficacy of various frothers may be significantly enhanced for copper flotation by the addition of DR-2-EH as such, of DR-2- EH further enriched with its component 2,4-diethyloctane-1 ,5-diol or by the addition the individual component 2,4-diethyloctane-1,5-diol as such. C.2 Results of gold flotation with frother mixtures according to the invention

The flotation results for gold ore are shown below in Tables C.2.1

Example 2.: Enhancement of frothing efficacy of by addition of DR-2-EH

Footnotes: a) according to invention b) comparative:

*) comprising 2,4-diethyl-octane-1 ,5-diol

Table C.2.1 shows evidence that the results for gold ore tested with the ternary mixture has a clear higher recovery rate at 82.34% compared to the individual ones for MIBC, PolyTHF and DR-2-EH respectively. Hence, the ternary blend gives better valuable recovery compared to individual mixtures.

Summary: The combination of 2,4-diethyloctane-1 ,5-diol and other frother components results in improved gold flotation performance as represented by valuables recovery and grade.

Conclusion

The addition of DR-2-EH to single frothers enhances their efficacy, which can be even further improved, when the DR-2-EH is enriched of one of its already present component, which is 2,4- diethyloctane-1 ,5-diol. The individual synergistic effect of the isolated 2,4-diethyloctane-1 ,5-diol could be demonstrated as well for several other frother components. These results in improved flotation performance show a valuable metal recovery. And even if the valuable metal recovery is comparable, other positive effects, such as better selectivity can be observed.

Claims

1 . A method for flotation of an ore, which comprises the steps of

(A) providing an aqueous suspension comprising

(i) an ore, which is in the form of particles,

(ii) water,

(iii) a frothing agent mixture in a flotation cell to obtain a provided aqueous suspension,

(B) introducing air into the provided aqueous suspension to obtain a froth, characterized in that the frothing agent mixture is a frothing agent mixture of at least 2 frothing agents, wherein one of the frothing agents is 2,4-diethyloctane-1 ,5-diol or a distillation residue derived from the manufacturing process of 2-ethylhexanol comprising 2,4-diethy- loctane-1 ,5-diol, and at least one other frothing agent not comprised in such distillation residue, which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1 -propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB).

2. A method according to claim 1 , wherein the amount of component (iii) in the aqueous suspension is in the range of 0.00001 to 0.1 parts by weight based on 100 parts by weight of component (i).

3. A method according to claim 1 or 2, wherein the amount of component (iii) in the aqueous suspension is in the range of 0.0001 to 0.05 parts by weight based on 100 parts by weight of component (i).

4. A method according to any preceding claim, wherein the amount of component (ii) in the aqueous suspension is in the range of 70 to 1100 parts by weight based on 100 parts by weight of component (i).

5. A method according to any preceding claim, wherein the ore comprises a first mineral, which is a sulfide mineral, a phosphate mineral, a silicate mineral, a carbonate mineral, a fluoride mineral, a chloride mineral, an oxide mineral, a copper mineral, a molybdenum mineral, a zinc mineral, a lead mineral, a nickel mineral, an iron mineral, a manganese mineral, a titanium mineral, a cobalt mineral, a tungsten mineral, a vanadium mineral, a tin mineral, an aluminium mineral, a lithium mineral, a scandium mineral, a yttrium mineral, a lanthanum mineral, a cerium mineral, a praseodymium mineral, a neodymium mineral, a samarium mineral, an europium mineral, a gadolinium mineral, a terbium mineral, a dysprosium mineral, a holmium mineral, an erbium mineral, a thulium mineral, a ytterbium mineral, a lutetium mineral, a ruthenium mineral, a rhodium mineral, a palladium mineral, a silver mineral, an osmium mineral, an iridium mineral, a platinum mineral, a gold mineral or a combined mineral, which has a chemical composition assigning the combined mineral to two or more of the aforementioned minerals at the same time.

6. A method according to claim 5, wherein the ore is a copper ore.

7. A method according to claim 5, wherein the ore is a gold ore.

8. A method according to any of the claims 5 to 7, wherein the ore comprises the first mineral and a second mineral, which is different to the first mineral.

9. An aqueous solution of a frothing agent mixture for flotation of an ore, which comprises at least as one frothing agent 2,4-diethyloctane-1 ,5-diol or a distillation residue derived from the manufacturing process of 2-ethylhexanol comprising 2,4-diethyloctane-1 ,5-diol and at least one other frothing agent not comprised in such distillation residue, which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1 -propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB).

10. An aqueous solution of a frothing agent mixture according to claim 9, which comprises as other frothing agent another distillation residue obtained by hydroformylation of 1 -propene.

11. An aqueous solution of a frothing agent mixture according to claim 9, which comprises as other frothing agent an isomer mix of dipropylene glycol monobutyl ether with butoxy dipropanol (DPnB),

12. An aqueous solution of a frothing agent mixture according to claim 9, which comprises as other further frothing agent methyl isobutyl carbinol (MIBC).

13. An aqueous solution of a frothing agent mixture according to any of claims 10 or 12, which comprises a third frothing agent added to the frothing agent mixture, which is different to the already present other added frothing agents, and which is selected from the group consisting of a distillation residue obtained by hydroformylation of 1-propene, a distillation residue obtained by hydroformylation of octene, a cyclic terpene alcohol, methylisobutyl carbinol (MIBC), a non-cyclic C6-C12 alcohol, an alcoholic aliphatic ester, triethoxybutane, an ethoxylated and/or propoxylated non-cyclic C1-C6 alcohol, an isomer mix of dipropylene glycol monobutyl ether with butoxy dipropanol (DPnB), poly(tetrahydrofuran), polyethylene glycol and polypropylene glycol.

14. An aqueous suspension comprising

(i) an ore, which is in the form of particles,

(ii) water, (iii) a frothing agent mixture, characterized in that the frothing agent mixture is a frothing agent mixture of at least 2 frothing agents, wherein one of the frothing agents is 2,4-diethyloctane-1,5-diol or a distillation residue derived from the manufacturing process of 2-ethylhexanol comprising 2,4-diethyloctane-1 ,5-diol, and at least one of the other frothing agents not comprised in such distillation residue, which is selected from methyl isobutyl carbinol (MIBC), a distillation residue obtained by hydroformylation of 1 -propene or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB). An aqueous suspension according to claim 14, wherein the amount of component (iii) in the aqueous suspension is in the range of 0.00001 to 0.1 parts by weight based on 100 parts by weight of component (i), and the amount of component (ii) in the aqueous suspension is in the range of 100 to 1000 parts by weight based on 100 parts by weight of component (i). Use of the distillation residue derived from the manufacturing process of 2-ethylhexanol comprising 2,4-diethyloctane-1,5-diol or the compound 2,4-diethyloctane-1 ,5-diol as such as frothing agent to enhance the efficacy for flotation of one or more other frothing agents, wherein the other frothing agent(s) are selected from a distillation residue obtained by hydroformylation of 1-propene, methyl isobutyl carbinol (MIBC) or an isomer mix of dipropylene glycol monobutyl ether with butoxy di-propanol (DPnB).