New frother for mineral recovery

Abstract

The present invention relates to a composition comprising at least one compound of formula (I) and the use of said composition for the recovery of valuable minerals from ores and other raw materials by flotation (formula (I)).

Description

[0001] The present invention relates to a composition comprising at least one compound of formula (I) and the use of said composition for the recovery of valuable minerals from ores and other raw materials by flotation.

[0002] BACKGROUND

[0003] Froth flotation is a process used for the beneficiation of ores containing valuable minerals, usually referred to as "valuable minerals". One or more valuable minerals refer to a metal, metals, a mineral or minerals that are the main target of the flotation process, i.e. the metals and minerals from which impurities are desired to be removed.

[0004] A typical froth flotation process involves intermixing an aqueous slurry containing finely ground particles of an ore with a "frother" or frothing agent to produce a froth. The grinding is usually carried out in water and the resulting slurry is called "ore slurry". The ore slurry is treated in flotation cells which agitate the mixture and introduce air as small bubbles. The ore particles containing one or more valuable minerals are preferentially attracted to the froth due to the affinity between the froth and the exposed mineral on the surface of the ore particles. The valuable minerals are then collected by separating them from the froth to obtain a concentrate, while gangue particles, which have a poor or no affinity to the froth, sink or remain in the liquid to obtain a tailing.

[0005] The separation by froth flotation is based on the selective adhesion of the gas bubbles to the surface of the particles of the target valuable mineral in the mineral / water slurry.

[0006] Froth flotation is a versatile process that can be applied to the separation of a wide range of valuable minerals. In fact, the affinity of the surface of the mineral particles to the froth to which they are exposed can be selectively increased by chemical treatment, for example by changing the hydrophobicity of the surface of the mineral particles. Just to illustrate the versatility of the process, froth flotation is used for the separation of sulphide minerals from siliceous gangue and for the recovery of coal from slurries (run-of-mine) containing, for example, carbonaceous material with high ash content, shale, clay and other non-carbonaceous impurity minerals such as kaolinite, quartz, dolomite, calcite, muscovite, pyrite and feldspar.

[0007] The frother is used to provide the basic froth phase required to carry out the process, while other reagents are used to control the relative hydrophilicity of the particles and to maintain the appropriate froth properties. Among these reagents, one can cite -(i) collectors, which can be non-ionic, amphoteric, anionic, cationic compounds and mixtures thereof; -(ii) modifiers, which can be activators or depressants, i.e. which can increase or decrease the adsorption of the collector to the surface of a particular mineral.

[0008] The frother can be selected from alcohols, polyglycols, alkoxylated paraffins, organic acids and amines. However, they are typically selected from alcohols, polyglycols and alkoxylated paraffins as they have little collector properties (collectors), which is not the case for example for organic acids and amines. Frothers suitable for different applications can be found in Minerals 2018, 8(2), 53: “Classification of Flotation Frothers”. MIBC, i.e. 4-methyl-2-pentanol, is one of the most commonly used flotation frothers in coal, metal sulfide or non-sulfide flotation.

[0009] In industry, froth flotation is a multi-stage process which comprises - (i) a roughing stage, where the process is designed to produce a concentrate of valuable minerals at high recovery (yield typically over 80%) - (ii) optional regrinding of the concentrate obtained in the roughing stage - (iii) a cleaning stage, where the process is designed to produce a concentrate of higher grade from the optionally regrinded roughing concentrate. Cleaning can be repeated several times until a marketable concentrate is produced. In the case of copper, marketable concentrates are typically in the range from 15% to 38% Cu.

[0010] Strong frothers are typically useful in the roughing stage in order to recover valuable minerals at high yield. More particularly, strong frothers are effective in recovering coarse particles, i.e. particles of relatively large size (i.e. particles of diameter > 100 pm as generally considered).

[0011] After the regrinding stage, coarse particles are now much finer in size. Weak frothers are typically useful in the cleaning stage in order to recover valuable minerals at high selectivity, thereby providing a concentrate of high grade. However, frothers are typically introduced (and thus persist) from the roughing stage until the regrinding and cleaning stages.

[0012] As generally considered, commercially available frothers are either too weak in frothing properties, leading to poor recovery (e.g. in the roughing stage), or such properties are too strong, leading to poor selectivity (e.g. in the cleaning stage). In practice, plants typically use a combination of strong and weak frothers, which are selected to balance the needs of the roughing and cleaning stages. Therefore, there is a need for new frothers and new frother compositions.

[0013] There is a need for new compositions comprising one or more strong frothers, which can be used for high yield recovery of valuable minerals by froth flotation. Ideally, such compositions should be effective in recovering coarse particles of valuable minerals.

[0014] Obtaining such one or more stronger frothers and such compositions will allow to treat less finely ground ore particles during the flotation process and thus will allow to reduce the costs associated with the energy spent under more extreme ore grinding conditions. Moreover, since the specific surface of the coarse particles is reduced compared to the specific surface of the thinner particles, less collector will be required during the flotation process, which will represent an economic and environmental advantage.

[0015] There is also a need for new compositions comprising one or more strong frothers that can be used in sufficient amount to produce a strong frothing behavior at the roughing stage without impairing at all the process at the cleaning stage. Indeed, the possibility to use sufficient amount of said frother to produce a strong frothing behavior should help to have a high recovery of the valuable mineral at the roughing stage and an improved recovery of the coarse particles of the valuable mineral.

[0016] Generally, the strong frother used at the roughing stage persists downstream of the flotation cells at the cleaning stage. This then creates a lower selectivity, an operating trade-off in the circuit at the cost of the recovery, where the cells are less "aggressive" to operate (i.e. increased froth depth and reduced gas flow) and creates over frothing, i.e. the formation of too much froth, which is detrimental to the overall process by reducing the selectivity at the cleaning stage and / or leading to an overflow of the cleaning cells. In some cases, a large amount of anti-foaming agent (defoamer) needs to be used in the cleaning circuit to control the over frothing, thus creating additional costs.

[0017] There is also a need for strong frothers that can be transformed / dissociated into less strong frothers, or weak frothers or even non-frothers, during the whole process and especially between the roughing and the cleaning stages.

[0018] Obtaining such "dissociable" stronger frothers would make it possible to use them in sufficient amount to produce a strong frothing behavior, thus helping to have a high recovery of the valuable mineral and an improved recovery of the coarse particles of the valuable mineral at the roughing stage and to avoid over frothing and reduce the selectivity at the additional stages, such as the cleaning stage.

[0019] Finally, there is a need for frother compositions that are less volatile and have a higher flash point than the currently available frother compositions. Indeed, for safety reasons, it is highly desirable to reduce the flammability of the frother compositions, both during storage and during the use of said compositions. Just to give an example, MIBC, a commonly used frother, is a highly flammable compound with a flash point of 41 °C. SUMMARY

[0020] The Applicant has surprisingly found that the compositions according to the present application can satisfy all these needs and more.

[0021] Thus, in a first aspect, the present application relates to a composition comprising at least one compound of formula (I):

[0022]

[0023] wherein:

[0024] A represents a C1-C8alkanediyl group which can be linear, branched or cyclic,

[0025] B, which can be identical or different at each occurrence, represents a C1-C8alkanediyl group which can be linear, branched or cyclic,

[0026] R represents H or a C1-C8alkyl group which can be linear or branched, and

[0027] n is an integer > 0 and < 100.

[0028] In a second aspect, the present application relates to a flotation process for the recovery of valuable minerals from ores and other feedstocks, the process comprising adding to said ores and other feedstocks a composition comprising at least one compound of formula (I):

[0029]

[0030] wherein A, B, R and n are as previously defined.

[0031] In a third aspect, the present application relates to the use of a composition comprising at least one compound of formula (I) for the recovery of valuable minerals from ores and other feedstocks by flotation:

[0032]

[0033] wherein A, B, R and n are as previously defined.

[0034] Composition comprising a compound of formula (I)

[0035] The composition according to the present application comprises at least one compound of formula (I) as disclosed above.

[0036] Typically, in formula (I), A represents a C1-C8alkanediyl group which can be linear, branched or cyclic.

[0037] Preferably, A is selected from the list consisting of: -CH2-, -CH2-CH2-,

[0038] -CH 2- CH2-CH2-CH2-CH2-, -CH2-CH2-CH2-CH2-CH2-, and

[0039] -CH(CH3)-. More preferably, A is selected from the list consisting of: -CH2-,

[0040] -CH2-CH2-, -CH2-CH2-CH2-, and -CH(CH3)-, even more preferably, A is selected from the list consisting of: -CH2-, -CH2-CH2-CH2-, and -CH(CH3)-.

[0041] In some embodiments, A represents a linear Ci-C8alkanediyl. In this case, preferably, A is selected from the list consisting of: -CH2-, -CH2-CH2-,

[0042] -CH 2- -CH2-CH2-, -CH2-CH2-CH2-, -CH2-CH2-CH2-CH2-, and -CH2-CH2-CH2-CH2-CH2-. More preferably, A is selected from the list consisting of: -CH2-, -CH2-CH2-, and

[0043] -CH2-CH2-CH2-, even more preferably, A represents -CH2- or -CH2-CH2-CH2-.

[0044] Typically, B, which can be the same or different at each occurrence, represents a Ci-C8alkanediyl which can be linear, branched or cyclic. Preferably, B is selected from the list consisting of: -CH2-CH2-, -CH2-CH(CH3)-, -CH(CH3)-CH2-, and -CH2-CH2-CH2-CH2-. Preferably, B represents -CH2-CH2- or -CH2-CH(CH3)-, and more preferably B represents -CH2-CH2-.

[0045] In some preferred embodiments, the composition according to the application comprises at least one compound of formula (I) wherein A represents -CH2- or -CH2-CH2-CH2-, and B represents -CH2-CH2-.

[0046] In another preferred embodiment, the composition according to the application comprises at least one compound of formula (I) wherein A represents

[0047] -CH(CH3)-, and B represents -CH2-CH2-.

[0048] Typically, in formula (I), R represents H or a Ci-C8alkyl which can be linear or branched. In some preferred embodiments, R is H. In some other preferred embodiments, R is selected from the list consisting of: methyl, ethyl, propyl, isopropyl, sec-butyl, tert-butyl, isobutyl and n-butyl.

[0049] In some preferred embodiments, the composition according to the application comprises at least one compound of formula (I) wherein A represents

[0050] -CH2- or -CH2-CH2-CH2-, B represents -CH2-CH2- and R is H.

[0051] In another preferred embodiment, the composition according to the application comprises at least one compound of formula (I) wherein A represents

[0052] -CH(CH3)-, B represents -CH2-CH2- and R is H.

[0053] Generally, in formula (I), n is an integer > 0 and < 100. Preferably, n is an integer > 0 and < 50; more preferably, n is an integer > 0 and < 20; even more preferably, n is an integer > 0 and < 10.

[0054] In some embodiments, n is selected from 1 to 10, preferably from 1 to 6 and more preferably from 1 to 4.

[0055] In some preferred embodiments, the composition according to the application comprises at least one compound selected from the list consisting of

[0056] and

[0057] In some other preferred embodiments, the composition according to the application comprises at least one compound selected from the list consisting of

[0058] and

[0059] In some embodiments, the composition according to the application comprises at least two compounds of formula (I).

[0060] By way of example only, the synthesis of the compounds of formula (I) according to the application can be carried out by the different paths A to E below.

[0061] Path A

[0062]

[0063] Path B

[0064]

[0065] Path C

[0066]

[0067] Path D

[0068]

[0069] Path E

[0070]

[0071] In the above paths A to E, A, B, R and n are as defined previously.

[0072] The skilled person can easily adapt the reaction conditions in order to obtain the desired product in high yield. The skilled person can also find other reaction paths to prepare the compounds according to the application.

[0073] More complete details on some reaction conditions are given in the examples of the experimental part.

[0074] In some other embodiments, the composition according to the application further comprises at least one compound selected from the group consisting of a foaming agent, a collector, water, a compatibility agent, an antifoam agent, a dispersant, a pH regulator, a rheology modifier, a surfactant, an activator, an inhibitor, a lubricant, an anti- scaling agent and an anti-corrosion agent. Preferably, the compound is selected from a collector and / or a foaming agent.

[0075] The foaming agent can be selected from the list consisting of phenols, alkyl sulfonates, fatty alcohols, cyclic alcohols, alkoxylated paraffins, polyglycols, polypropylene glycols, polyglycol ethers, polypropylene glycol ethers, polyglycol glycerol ethers, pyridine derivatives and mixtures thereof.

[0076] Without being exhaustive, the foaming agent can be selected from:

[0077] (i) phenols such as o-cresol, m-cresol, p-cresol, dimethylphenol and phenol;

[0078] (ii) alkyl sulfonates, in particular alkyl aryl sulfonates;

[0079] (iii) fatty alcohols such as n-butanol, n-pentanol, iso-pentanol, n-hexanol, 2- ethylhexanol, n-heptanol, methyl isobutyl carbinol (MIBC), octanoic acid, 4-heptanol, a mixture of C4-C7 alcohols and a mixture of C5-C8 alcohols;

[0080] (iv) cyclic alcohols such as terpineol and borneol;

[0081] (v) alkoxylated paraffins, such as 1,1,3-triethoxybutane (TEB) and 1,3,5-trialkoxypropyl trioxane;

[0082] (vi) polyglycols, polyglycol ethers, such as

[0083] R2(X) m OH, wherein R2= H or C n H 2n+1 wherein n is an integer ranging from 1 to 6, wherein m is an integer ranging from 2 to 20 and X = EO (ethylene oxide), PO (propylene oxide) or BO (butylene oxide),

[0084]

[0085] (vii) pyridine derivatives;

[0086] (viii) and mixtures thereof.

[0087] Collectors can be comprised in the composition according to the application. Without wishing to be bound by theory, collectors are agents used to selectively adsorb onto the surface of the particles to enhance their hydrophobic behavior and increase their affinity with the froth. Selecting the appropriate collector is essential for an efficient separation by froth flotation.

[0088] Suitable collectors can be selected from the list consisting of non-ionic, anionic, cationic, amphoteric collectors and mixtures thereof.

[0089] By way of example only, non-ionic collectors can be hydrocarbon oils, such as fuel oil, kerosene or small molecules like isopropyl ethyl thioethylcarbamate (IPETC). Non-ionic collectors are widely used for the flotation of, for example, coal, molybdenite, elemental sulphur, copper and talc.

[0090] Anionic collectors are generally acids or acid salts that ionize in water and can be selected from

[0091] - (i) organic sulphur-containing compounds, such as xanthates (e.g. ethyl xanthate), monothiophosphates, monothiophosphinates, dithiophosphates, dithiophosphinates, dithiocarbamates, trithiocarbonates, alkyl sulphates, sulphonates, sulphosuccinates, sulphosuccinamates, generally as sodium, potassium or ammonium salts,

[0092] - (ii) organic phosphorus-containing compounds, such as phosphonic acids and phosphoric esters, generally as sodium, potassium or ammonium salts,

[0093] - (iii) carboxylic acids, such as decanoic acid, lauric acid, myristic acid, oleic acid, stearic acid, palmitic acid, linoleic acid, synthetic saturated or unsaturated fatty acids, tall oil, generally as sodium, potassium or ammonium salts, such as sodium oleate,

[0094] (iv) mixtures thereof.

[0095] By way of example only, xanthates are particularly selective collectors for sulphide minerals, while sodium oleate is typically used for oxide mineral flotation.

[0096] Cationic collectors typically carry a positively charged amine group, which can be a primary, secondary or tertiary amine group. Quaternary ammonium salts can also be used as cationic collectors. Cationic collectors are used, for example, for the flotation of silicates and rare metal oxides.

[0097] Amphoteric collectors are compounds which carry one or more cationic and one or more anionic functional groups. Common types are long-chain amino acids, such as cetyl aminoacetate, N-lauryl-p-aminopropionic acid, N-lauryl-β-iminodipropionic acid, N-lauryl-β-aminobutyric acid or long-chain amino sulphonic acids such as N-myristyl taurine.

[0098] Certain other reagents, known as "modifiers", can be included in the composition according to the application to improve the separation and recovery of the desired mineral and / or metal. Modifiers, which can include pH adjusters, can be used to change and control the pH of the slurry in order to improve the separation and recovery of the desired mineral and / or metal. Rheology modifiers can be used to change and control the rheology of the slurry in order to improve the separation and recovery of the desired mineral and / or metal.

[0099] In some cases, compounds known as "activators" and "inhibitors" can be added to the composition according to the application.

[0100] Typically, activators are specific compounds used to activate a certain valuable mineral. By way of example, copper sulphate is used in order to improve the collector coating on a particular valuable sulphide.

[0101] Inhibitors generally prevent the adsorption of collectors to the surface of a particular mineral; they are used to improve selectivity. As suitable inhibitors, mention can be made of cyanide, lime added as CaO or Ca(OH)2, starch and lignin.

[0102] In some other embodiments, the composition according to the application comprises water.

[0103] The composition can also comprise some other products, such as by-products from the synthesis of the compound of formula (I).

[0104] Flotation process

[0105] In a second aspect, the present application relates to a flotation process for the recovery of valuable minerals from ores and other feed materials, the process comprising adding to said ores and other feed materials a composition comprising at least one compound of formula (I):

[0106]

[0107] wherein A, B, R and n are as previously defined.

[0108] The flotation process according to the present application relates to the recovery of valuable minerals from ores and other feed materials.

[0109] In some embodiments, the flotation process according to the present application comprises adding to ores in the form of crushed ores, ground ores and / or aqueous slurries a composition comprising at least one compound of formula (I), the composition having all the possible features and all the possible embodiments previously described.

[0110] In some other embodiments, the flotation process according to the present application comprises adding to any other feed material a composition comprising at least one compound of formula (I), the composition having all the possible features and all the possible embodiments previously described.

[0111] The term valuable minerals refers to a metal, a plurality of metals, a mineral, a plurality of minerals, an energy mineral or a plurality of energy minerals that is the main target of the flotation process, i.e. the metal, mineral and energy mineral from which it is desired to remove impurities.

[0112] In some embodiments, the valuable minerals are sulfide minerals, non-sulfide minerals or native metals.

[0113] In some preferred embodiments, the valuable minerals are sulfide minerals and the sulfide mineral feed material / ore is, for example, sulfide ores, historical tailings, hydrocyclone underflow, sinks, etc., or combinations thereof. The sulfide mineral feed material / ore includes Cu-Mo ores, Cu-Au ores, primary Au ores, platinum group metal ores. Cu ores, Ni ores, Ni-Cu ores, and ores including Pb, Zn, Cu, and / or Ag. Valuable metals of interest include, for example, gold, silver, platinum, palladium, other platinum group metals, copper, nickel, molybdenum, cobalt, lead, and zinc. The valuable mineral feed material / ore is comprised of copper-bearing minerals, such as chalcocite, chrysocolla, bornite, covellite; gold-bearing minerals, such as electrum, pyrite, marcasite, copper sulfide minerals, and arsenopyrite; molybdenum-bearing minerals, such as molybdenite; lead-bearing minerals, such as galena; zinc-bearing minerals, such as sphalerite and marmatite; silver-bearing minerals, such as argentite, freibergite, silver-bearing pyrite, and silver-bearing galena; nickel-bearing minerals, such as millerite; platinum group metal-bearing minerals, such as sperrylite; or combinations thereof.

[0114] In some other preferred embodiments, the valuable mineral is a non-sulphide mineral and the feedstock / ore is a non-sulphide mineral feedstock / ore. The term non-sulphide mineral includes minerals belonging to the following classes: oxides, silicates, sulphates, phosphates, carbonates and halides. By way of example only, non-sulphide mineral feedstock / ores include phosphates, iron oxides, kaolinite and bentonite, spodumene, potash, borates, trona, fluorite, calcite, dolomite, limestone, barite, mica, feldspar, quartz, silica sand, monazite, cyanite, magnesite, chromite, bauxite, ilmenite, rutile, manganese oxides, graphite, talc and cassiterite.

[0115] Also in some preferred embodiments, the valuable mineral is a native metal and the feedstock / ore is, for example, a gold, silver or copper feedstock / ore.

[0116] In some other embodiments, the valuable mineral is an energy mineral such as coal and the valuable mineral feedstock is a slurry of coal and gangue (run-of-mine coal) containing, for example, carbonaceous material with a high ash content, shale, clay and other non-carbonaceous impurity minerals such as kaolinite, quartz, dolomite, calcite, muscovite, pyrite and feldspar.

[0117] The run-of-mine coal can be a high rank coal such as anthracite or hard coal, a medium rank coal such as bituminous coal, or a low rank coal such as sub-bituminous coal, lignite or brown coal.

[0118] In a third aspect, the present application relates to the use of a composition comprising at least one compound of formula (I) for the recovery of a valuable mineral from ores and other feedstocks by flotation:

[0119]

[0120] wherein A, B, R and n are as previously defined.

[0121] The use according to the present application relates to a composition having all the possible features and all the possible embodiments previously described.

[0122] The present application will now be explained in more detail with reference to the following examples, which are not intended to be limiting.

[0123] Example

[0124] Preparation of "decomposable" frother

[0125] Synthesis of 2-hydroxyacetic acid 4-methylpentan-2-yl ester (frother 1)

[0126]

[0127] In a 500-mL round bottom flask, glycolic acid (13.8 g, 180 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (37.6 g, 360 mmol, 2 equiv) and toluene (230 mL) were added sequentially, followed by the addition of sulfuric acid (96%) (1 mL, 18 mmol, 0.1 equiv). The resulting solution was heated under reflux and water was removed azeotropically using a Dean-Stark apparatus. After 3 h, the water distillation was complete and the reaction mixture was allowed to cool to room temperature. The resulting solution was washed with saturated aqueous NaHC03solution (twice), then with saturated aqueous NaCl solution. The organic phase was dried over anhydrous magnesium sulfate and the volatiles (toluene and excess MIBC) were removed in vacuo. The crude product was purified by flash chromatography on silica gel to give the desired MIBC glycolate as a colorless liquid in the first fraction (15 g, 52% yield).

[0128] Alternative synthesis of 2-hydroxyacetic acid 4-methylpentan-2-yl ester (Foamer 1)

[0129]

[0130] In a 250-mL round bottom flask, glycolic acid (30.4 g, 396 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (200 mL, 1.54 mol, 4 equiv) and sulfuric acid (96%) (1.1 mL, 20 mmol, 0.05 equiv) were added sequentially. The resulting solution was heated at 130 °C for 6 h. The reaction mixture was then allowed to cool to room temperature and calcium carbonate (4.5 g) was added, and the resulting suspension was stirred overnight. The white solid was then filtered from the suspension and the excess MIBC was removed in vacuo. The remaining crude product was purified by distillation to give MIBC glycolate as a colorless liquid (36 g, 57% yield).

[0131] Synthesis of 2-(2-hydroxyethoxy)acetic acid ethyl ester

[0132]

[0133] As described in J. Photosci. 2000, 7, 143-148.

[0134] Synthesis of 2-(2-hydroxyethoxy)acetic acid 4-methylpentan-2-yl ester (Foamer 2)

[0135]

[0136] In a 100-mL round-bottom flask, ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate (20 g, 132 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (52.1 g, 565 mmol, 4.3 equiv), and sulfuric acid (96%) (0.7 mL, 12.6 mmol, 0.1 equiv) were added sequentially. The resulting solution was heated at 50 °C for 24 h. The reaction mixture was then allowed to cool to room temperature and calcium carbonate (15 g) was added, and the resulting suspension was stirred overnight. The white solid was then filtered from the suspension and excess MIBC was removed in vacuo. [Care should be taken in this step as residual traces of acidity or overheating can lead to cyclization of the product and release of MIBC.] The remaining crude product (7.8 g) was purified by silica gel flash chromatography to give the desired product as a colorless liquid (6.2 g, 23% yield).

[0137] Synthesis of ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate

[0138]

[0139] As described in Langmuir 2013, 29, 13111-13120.

[0140] Synthesis of ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate

[0141]

[0142] In a 250-mL round-bottom flask, ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate (30.3 g, 155 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (125.1 g, 156 mL, 1.2 mol, 8 equiv), and sulfuric acid (96%) (0.4 mL, 7.2 mmol, 0.05 equiv) were added sequentially. The resulting solution was heated at 90 °C for 24 h. The reaction mixture was then allowed to cool to room temperature and calcium carbonate (5 g) was added, and the resulting suspension was stirred overnight. The white solid was then filtered from the suspension and excess MIBC was removed in vacuo. The remaining crude product (32.2 g) was purified by silica gel flash chromatography to give the desired product as a colorless liquid (25.4 g, 66% yield).

[0143] Synthesis of ethyl 2-(2-(2-hydroxyethoxy)ethoxy)acetate

[0144]

[0145] As described in Langmuir 2013, 29, 13111-13120.

[0146] Synthesis of 2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)acetic acid 4-methylpentan-2-yl ester (Foamer 4)

[0147]

[0148] In a 250-mL round bottom flask, ethyl 2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)acetate (15 g, 63.5 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (26 g, 156 mL, 254 mmol, 4 equiv), toluene (150 mL) and sulfuric acid (96%) (0.38 mL, 6.8 mmol, 0.1 equiv) were added sequentially. The resulting solution was heated under reflux and the ethanol was removed azeotropically using a Dean-Stark apparatus. After 10 h, the reaction mixture was allowed to cool to room temperature. Calcium carbonate (4 g) was added and the resulting suspension was stirred overnight. The white solid was then filtered from the suspension and the excess MIBC was removed in vacuo. The remaining crude product (22.3 g) was purified by flash chromatography on silica gel to give the desired product as a colorless liquid (7.6 g, 35% yield).

[0149] Synthesis of 4-hydroxybutanoic acid 4-methylpentan-2-yl ester (Foamer 5)

[0150]

[0151] In a 250-mL round bottom flask, gamma-butyrolactone (GBL) (20 g, 230 mmol, 1 equiv), 4-methyl-2-pentanol (MIBC) (100 g, 979 mol, 4 equiv) and sulfuric acid (96%) (0.5 g, 4.9 mmol, 0.02 equiv) were added sequentially. The resulting solution was stirred at room temperature for 14 h, after which equilibrium was reached (by 1 HNMR, GBL / ester = 63:37). Calcium carbonate (3 g) was then added and the resulting suspension was stirred for 1 h. The white solid was then filtered from the suspension and the filtrate was diluted with AcOEt (200 mL). The organic phase was washed with Na2C03solution (1% in water, 100 mL), water (2 x 100 mL) and finally with saturated NaCl solution (100 mL). The organic phase was then dried over MgS04, filtered and the resulting oil was purified by flash chromatography on silica gel to give the desired product as a colorless oil (13 g, 30% yield).

[0152] Flash point determination

[0153] The flash point of frother 1 was determined using ASTM method D3828-87, Method B, Limited Flash Point method, also known as the Setaflash closed cup method. Approximately 2 mL of sample was placed in the cup and tested at 22°C, 35°C, 50°C, 70°C, 80°C, 85°C and 87°C. The lowest temperature at which the headspace burned was defined as the flash point.

[0154] Frother 1 (flash point of 87°C) is much less flammable than MIBC (flash point of 41°C). This is very advantageous for safety reasons during storage and transportation or during use of this type of frother.

[0155] Hydrolysis of "decomposable" frother

[0156] DI water (50 g), Ca(OH)2to adjust the pH to 12 and "decomposable" frother (20 μί) were added in a 100 mL flask. The resulting solution was stirred at room temperature for 24 h after which complete hydrolysis was achieved (checked by LC-MS when the ester peak disappeared).

[0157] The resulting solution was used in flotation tests to evaluate the flotation performance of the "decomposable" frother after hydrolysis.

[0158] Flotation tests

[0159] Before performing the flotation tests in a Denver cell, a sample of 1 Kg of Cu-Mo ore crushed to 2 mm and 0.6 g of Ca(OH)2was milled in a laboratory stainless steel ball mill in the presence of 675 ml of water to achieve a grind of 80% passing 212 μιη. The pH of the resulting slurry was 9.8. The milled slurry was transferred to a flotation cell with a capacity of 2.7 L and diluted to a solids content of 32%. The impeller speed was set to 1000 r / min and the slurry was agitated. The reagent addition strategy and the flotation program were as follows: collector was added to the flotation slurry and the slurry was homogenized for 1 min; then, the frother was added and the slurry was homogenized for another 45 s. The air flow was turned on and the froth was scraped every 15 s for a total time of seven minutes to collect the Cu concentrate. The air flow rate supplied to the flotation cell was kept at a flow rate of 3.25 L / min in all tests. The slurry level was kept at the same level by adding water.

[0160] After the tests, the concentrate and the tailings were filtered, dried, weighed and analyzed for Cu content.

[0161] The Cu ore information used in the flotation tests is presented in Table 1.

[0162] Table 1. Analysis of the Cu-Mo ore used in the flotation tests.

[0163] Table 1. Analysis of the Cu-Mo ore used in the flotation tests.

[0164] The determination of the water recovery (water rec. %) is made using the following equation ：

[0165]

[0166] Where:

[0167] C = concentrate (water + solids) collected over time;

[0168] Cdry(g) = solids after concentration of the concentrate has dried;

[0169] W = total mass of water added to the cell.

[0170] Copper recovery (Cu rec. wt. %), copper concentrate grade (Cu grade wt. %) are determined by analyzing the Cu content of the ore, concentrate and tailings.

[0171] Coarse particle recovery % is determined by passing the concentrate collected through a 212 pm sieve.

[0172] Results

[0173] The flotation tests were conducted using isopropyl ethyl thio carbamate (IPETC) as collector.

[0174] Blends of glycol ethers as strong frothers and methyl isobutyl carbinol (MIBC) as a weak frother are well known in the industry. The comparative examples were conducted using AEROFROTH 68 (AF68 - blended glycol ethers) or AEROFROTH 70 (AF70 - MIBC).

[0175] The first flotation tests were conducted at pH 9.5, which is a relatively low pH, chosen to simulate the pH conditions of the rougher stage.

[0176] Table 2. Results of flotation tests before hydrolysis of "decomposable" frother

[0177]

[0178] Flotation at pH 9.5 over 7 minutes.

[0179] **The blend consists of a solution containing 6 ppm of frother 1, 4 ppm of frother 2, 6 ppm of frother 3 and 5 ppm of frother 4.

[0180] *** Particle size > 212 pm.

[0181] The results of Table 2 show that, surprisingly, frothers 1 to 5 are strong frothers which allow a higher water recovery than MIBC and more surprisingly than the blended glycol ether. Even more surprisingly, the blend of frothers 1 to 4 shows similar performances.

[0182] Furthermore, the Cu recovery and Cu grade are similar for the flotation with frother 1, frother 2, frother 3, frother 4, frother 5 and with the blend of "decomposable" frothers respectively and for the flotation with the blended glycol ether.

[0183] Finally, frothers 1, 3, 4 and 5 are strong frothers which allow a higher coarse particle recovery than MIBC and more surprisingly, in the case of frothers 1 and 3, even higher coarse particle recovery than the blended glycol ether. The blend of frothers 1 to 4 allows a higher coarse particle recovery than MIBC.

[0184] As mentioned, the hydrolysis of frothers 1 to 5 and of the blend of frothers 1 to 4 was performed at pH 12 by stirring their solutions in water at 23°C over 24 hours.

[0185] A second flotation test was then performed at pH 9.5 using the resulting hydrolyzed frother or frother blend.

[0186] Table 3. Results of the flotation test after hydrolysis of the "decomposable" frother

[0187]

[0188] Flotation at pH 9.5 over 7 minutes.

[0189] From the results compiled in Table 3, it is clear that frothers 1, 3, 4 and 5 which behaved like the blended glycol ether before hydrolysis behave more like MIBC after hydrolysis.

[0190] Without being bound by any theory, it is hypothesized that the ester function of frothers 1, 3, 4 and 5 is hydrolyzed, resulting in a hydrolysis product and MIBC and surprisingly their mixture behaves like MIBC.

[0191] The inventors have shown that the frother composition according to the application (initially behaving as a strong frother and hydrolyzing to give a hydrolysis product and MIBC) adopts the frothing behavior of MIBC after hydrolysis.

[0192] The present inventors have shown that the blowing agents and blowing agent compositions according to the present application can surprisingly behave as strong blowing agents at a given pH, some properties exceeding those of well-known strong blowing agents (e.g. blended glycol ethers), while behaving like less strong or even weak blowing agents after or during a phase of higher pH.

[0193] Furthermore, the present inventors have shown that these blowing agents and compositions are advantageous in terms of safety of storage, transport or handling compared to other blowing agents (such as MIBC) at least due to a higher flash point.

Claims

1. A flotation process for the recovery of valuable minerals from ores and other feed materials, the process comprising adding to said ores and other feed materials a composition comprising at least one compound of formula (I): wherein: A represents a linear, branched or cyclic Ci-C8alkanediyl group, B represents, on each occurrence, identically or differently, a linear, branched or cyclic Ci-C8alkanediyl group, R represents H or a linear or branched Ci-C8alkyl group, and n is an integer > 0 and < 100. (I) A is selected from the list consisting of: -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -CH2-CH2-CH2-CH2-, and -CH2-CH2-CH2-CH2-CH2-. B is selected from the list consisting of: -CH2-CH2-, -CH2-CH(CH3)-, -CH(CH3)-CH2-, and -CH2-CH2-CH2-CH2-. R is H. R is selected from the list consisting of: methyl, ethyl, propyl, isopropyl, sec-butyl, tert-butyl, isobutyl and n-butyl.

7. The flotation process according to any one of the preceding claims, comprising at least one compound selected from the list consisting of:

2. The flotation method according to claim 1, wherein, A is selected from the list consisting of: -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, 2- CH2-CH2-, -CH2-CH2-CH2-CH2-, -CH2-CH2-CH2-CH2-CH2-, and -CH(CH3)-.

3. The flotation method according to claim 2, wherein, 8. The flotation process according to any one of claims 1 to 6, comprising at least one compound selected from the list consisting of:

4. The flotation method according to any one of claims 1 to 3, wherein, 9. The flotation process according to any one of the preceding claims, comprising at least two compounds of formula (I).

5. The flotation method according to any of the preceding claims, wherein, 10. The flotation process according to any one of the preceding claims, further comprising at least one compound selected from the group consisting of frothers, collectors, water, compatibilizers, defoamers, dispersants, pH adjusters, rheology modifiers, surfactants, activators, depressants, lubricants, anti- scaling agents and anti-corrosion agents.

6. The flotation method according to any one of claims 1 to 4, wherein, The compound is selected from collectors and / or frothers. The valuable mineral is a sulfide mineral, a non-sulfide mineral or a native metal. The valuable mineral is an energy mineral.

14. Use of a composition as defined in the flotation process according to any one of claims 1 to 11 for the recovery of valuable minerals from ores and other feed materials by flotation. ​ 11. The flotation method according to claim 10, wherein, ​ 12. The flotation method according to claim 1, wherein, ​ 13. The flotation method according to claim 1, wherein, ​ ​

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