The present invention relates to collector compositions containing biodegradable compounds, and their use in treating siliceous ores.

Compounds for use in collector compositions to treat siliceous ores are known from several documents such as WO2012/139985, WO2018/007418. These documents disclose the direct flotation of silicas from iron ores using as the collector composition a composition that contains an alkylethermonoamine.

EP 1949963 discloses a collector composition for siliceous ores which is said to have improved biodegradability. The primary collector in this document is a polyester polyquaternary compound which corresponds to the polyester polyquaternary (PEPQ) compounds as disclosed in WO 2015/091308 together with a process to manufacture these polyester polyquaternary compounds and their use to treat phosphate ores so to recover phosphates therefrom by a reverse flotation to remove silica.

There is however a desire for additional biodegradable collector compositions that have a good performance in direct flotation of silica from siliceous ores different than the state of the art collector compositions.

The present invention now provides collector compositions that contain as a primary collector the compound of the formula (I)

wherein R is an alkyl group containing between 5 and 16 carbon atoms that may be branched or linear, k is a value of 1 to 3, m is an integer from 0 to 25, each A independently is -CH2-CH2- or -CH2CH(CH3)- or -CH2-CH(CH2-CH3)-, n is an integer of at least 3 and at most 8, and wherein X is an anion derivable from deprotonating a Bronsted-Lowry acid and (ii) a second compound selected from the group of other primary collectors, secondary collectors, depressants, frothers, solvent, wherein the other primary collector is selected from the group of cationic ammonium- fucntional surfactants different from the above formula (I), and amine-functional surfactants such as alkylamines, alkylamidoamines and etheramines; the secondary collector is chosen from the group of nonionic, and anionic surfactants, wherein the nonionic surfactants are chosen from the group of unbranched and branched fatty alcohols, alkoxylated fatty alcohols, alkylamide ethoxylates, alkyl diethanol amide ethoxylates, the anionic surfactants are chosen from the group of fatty acids, sulphonated fatty acid, acylamidocarboxylates, acylestercarboxylates, alkylphosphates, alkylpyrophosphates, alkylsulphates, and alkylsulphonates; the depressant is chosen from the group of polysaccharides and derivatives thereof, and polyacrylamide polymers; the frother is selected from MIBC and propoxylated and ethoxylated C6-C10 alcohols, and; wherein the solvent is chosen from the group of C1-C5 alcohols that may be optionally ethoxylated and/or propoxylated, such as preferably propylene glycol, triethylene glycol, ethylene glycol, 2-methoxyethanol, glycerol, or isopropanol, and acetic acid, provided that the second compound is not a compound of the formula ROH or R-(0-A)m-OH wherein R and m are the same as in the compound of formula (I)..

It should be noted that some compounds of the above formula I are disclosed for use in pharmaceutical preparations such as in“Esters of 6-aminohexanoic acid as skin permeation enhancers: The effect of branching in the alkanol moiety”, A Habralek et al, Journal of Pharmaceutical Sciences, Vol. 94, 1494-1499, (2005). The invention furthermore provides a process to treat siliceous ores wherein the process contains a step of froth flotating in the presence of the primary collector compound of formula (I), preferably froth flotating in the presence of a collector composition containing the primary collector compound (I), and a second compound selected from the group of further primary collectors, secondary collectors, depressants, frothers and solvents, more preferably froth flotating in the presence of the above collector composition. After completion of the flotation, a silicate-enriched flotate is obtained. The compounds of formula (I) were determined to be readily biodegradable, which adds to the environmental profile of the collector compositions in which they are used. Furthermore, the flotation results resulting when using them in flotating silicas from ores are very good, the compositions deliver better selectivity than known collector compositions containing biodegradable compounds and similarly good or better selectivity than not readily biodegradable alternatives. At the same time the collector compositions and process of the present invention provide for outstanding frothing properties. The compounds of formula (I) and collector compositions of the present invention were found to be especially suited for ores that are relatively fine, such as siliceous iron ores. The environmentally friendly PEPQ compounds from the prior art, though showing good performance on some ore types, such as phosphate and calcite ores, are not showing superior performance on all non-sulphidic ores. The compounds of the present invention appear to be more versatile than PEPQ as they work for several non-sulphidic ore types, e.g. also for iron ore.

Siliceous ores are ores in which silica is present in an amount of at least 1 wt%. Preferably, silica is present in those ores in an amount of between 2 and 50 wt%.

In a preferred embodiment R is an alkyl group that contains 6 to 16 carbon atoms. In a more preferred embodiment R is an alkyl group that contains 8 to 13 carbon atoms.

In another preferred embodiment R is branched on the carbon atom beta from the oxygen atom. In further embodiments R can contain more than a single branched carbon atom. It is furthermore preferred when n is 4, 5 or 6.

X is in a preferred embodiment a halogenide, sulphate, phosphate, hydrogen sulphate, hydrogen phosphate, or dihydrogen phosphate anion. If a further prirmary collector is present in the collector compositions or processes of the invention the further primary collector is selected from the group of amine- functional surfactants and (quaternary) ammonium compounds with a structure different from the above formula (I). Preferably, the further primary collector is selected from the group of fatty amines (alkylamines where the alkyl group is a C11-C24 alkyl), etheramines, etherdiamines, alkylamidoamines, optionally in their (quaternized) cationic form.

If a secondary collector is present in the collector compositions or processes of the present invention, the secondary collector is chosen from the group of nonionic and anionic surfactants. If the secondary collector is a nonionic surfactant it can be selected from the group of unbranched or branched fatty alcohols, alkoxylated alcohols, alkylamide ethoxylates, alkyl diethanol amide ethoxylates, alkyl amine ethoxylates. If the secondary collector is an anionic surfactant it can be selected from the group of fatty acids, sulphonated fatty acid, acylamidocarboxylates, acylestercarboxylates, alkylphosphates, alkylpyrophosphates, alkylsulphates, alkylsulphonates.

The secondary collector is preferably selected from the group of nonionics, like unbranched and branched fatty alcohols, alkoxylated fatty alcohols, alkylamide ethoxylates, and alkyl diethanol amide ethoxylates, even more preferably C11-C24 fatty alcohols, or alkoxylated C11-C24 fatty alcohols. Examples of secondary collectors in a most preferred embodiment are branched C1 1-C17 fatty alcohols, such as iso C13 fatty alcohols, and their ethoxylates and/or propoxylates. The secondary collector is not a compound of the formula ROH or R-(0-A)m-OH wherein R and m is the same as in the compound of formula (I) in the same composition.

In another preferred embodiment the above nonionic secondary collectors are combined with an anionic surfactant. If a depressant is present in the collector compositions or processes of the present invention, such depressant may be chosen from the group of polysaccharides and derivatives thereof, e.g. dextrin, starch, such as maize starch activated by treatment with alkali, and polyacrylamide polymers. Other examples of (hydrophilic) polysaccharides and derivatives thereof are cellulose esters, such as carboxymethylcellulose and sulphomethylcellulose; cellulose ethers, such as methyl cellulose, hydroxyethylcellulose and ethyl hydroxyethylcellulose; hydrophilic gums, such as gum arabic, gum karaya, gum tragacanth and gum ghatti, alginates; and starch derivatives, such as carboxymethyl starch and phosphate starch. The depressant is normally added in an amount of about 10 to about 1 ,000 g per ton of ore. If a frother is present in the collector compositions or processes of the present invention, examples of suitable froth regulators are methylisobutyl carbinol (MIBC) and alcohols having 6-10 carbon atoms which are alkoxylated with ethylene oxide and/or propylene oxide, especially branched and unbranched octanols and hexanols. The frother is not a compound of the formula ROH or R-(0-A)m-OH wherein R and m is the same as in the compound of formula (I) in the same composition.

The weight ratio between the primary collector(s) and the secondary collector is preferably from 15:85, more preferably 20:80, most preferably 25:75 to 99:1 , preferably 98:2, most preferably 97:3. All weight ratios herein refer to the ratio of active materials, unless stated otherwise.

If a solvent is present in the collector compositions or processes of the present invention, such solvent may be chosen from the group of C1-C5 alcohols, including alcohols that contain more than one hydroxyl unit, that optionally may be alkoxylated (ethoxylated and/or propoxylated) and acetic acid. Preferred examples are propylene glycol, ethylene glycol, triethylene glycol, glycerol, isopropanol, 2-methoxyethanol, acetic acid and combinations thereof. The solvent is not a compound of the formulae ROH or R-(0-A)m-OH wherein R and m is the same as in the compound of formula (I) in the same composition. When using the collector compositions of the present invention in the flotation of silica ores, it is possible to dilute them by adding further solvents, such as one of the above solvents, or water. The flotation process of the invention is preferably a direct flotation process of silicas, which may correspond with a reversed flotation process of other valuable minerals present in the ore such as iron. In the process of the present invention the ore is preferably a siliceous iron ore, hematite ore, magnetite ore, phosphate ore, calcite ore, or potash ore.

Reversed flotation means that the desired ore is not concentrated in the froth, but in the residue of the flotation process. The process of the invention is preferably a reversed flotation process for iron, such as magnetite, ores, more preferably for ores that contain more than 50 wt% of Fe304 on total iron oxide content, even more preferably more than 70 wt%, most preferably 80 to 99 wt%. In another preferred embodiment the ores contain less than 15 wt% of silica, even more preferably less than 12 wt%, most preferably less than 10 wt%, on total solids weight in the ore. In a reversed flotation process for concentrating iron, such as magnetite, ores, the pH during flotation in a preferred embodiment is suitably in the range of 5-10, preferably in the range of 7 to 9. In yet another preferred embodiment the ores treated by the process of the present invention have an average particle size of less than 200 pm.

The collector composition of the present invention is very beneficially used in a reversed froth flotation process of iron ores to enrich iron.

The froth flotation process of the invention in an embodiment comprises the steps of mixing a ground siliceous ore with an aqueous medium, preferably water;

- optionally, especially if the ore is an iron ore, concentrating the medium with magnetic separation;

optionally, conditioning the mixture with a depressant;

optionally, adjusting the pH;

conditioning the mixture with a primary collector of the formula (I) or a collector composition as defined herein;

introducing air into the conditioned water-ore mixture; and

skimming off the froth formed.

The composition is preferably liquid at ambient temperature, i.e., at least in the range of 4 to 25 °C.

The process of the invention may involve other additives and auxiliary materials that can be typically present in a froth flotation process, which additives and auxiliary materials can be added at the same time or (partially) separately during the process. Further additives that may be present in the flotation process are (iron) depressants, froth ers/froth regulators/froth modifiers/defoamers, cationic surfactants (such as alkylamines, quaternized amines, alkoxylates), and pH-regulators. After conditioning of the ore, the primary collector of the formula (I) or the collector compositions as defined herein can be added, optionally partially neutralized, and the mixture is further conditioned for a while before the froth flotation is carried out. After completion of the flotation, a silicate-enriched flotate and a bottom fraction poor in silicate can be withdrawn. In another aspect, the present invention relates to a pulp comprising crushed and ground siliceous ore, preferably siliceous iron ore, and the primary collector compound of formula (I) or the collector composition as defined herein, and optionally further flotation aids. These flotation aids may be the same as the above other additives and auxiliary materials, which can be typically present in a froth flotation process.

The amount of the collector used in the process of reversed flotation of the present invention will depend on the amount of impurities present in the ore and on the desired separation effect, but in some embodiments will be in the range of from 1 -500 g/ton dry ore, preferably in the range of from 10-200 g/ton dry ore, more preferably 20-150 g/ton dry ore.

Examples Example 1

Ore in flotation tests:

Fe - 69,5%, Si0 ₂ - 1 ,3%. Flotation chemicals

Isodecyloxyprolylamine (partly neutralized by acetic acid) (Lilaflot 811 M)

Polyester polyquaternary ammonium compound synthesized as described in WO 2015/091308A1 Example 1.

Alkyl-6-aminohexanoate sulphates from Exxal™ 8, Exxal™ 10 and 2-ethylhexanol were synthesized as described in“Esters of 6-aminohexanoic acid as skin permeation enhancers: The effect of branching in the alkanol moiety”, A Habralek et al, Journal of Pharmaceutical Sciences, Vol. 94, 1494-1499, (2005).

Synthetic process water

Synthetic process water was used in the flotation tests. It was prepared by adding appropriate amounts of commercial salts to deionised water. Following the composition described by chemical analysis of process water from plant, table 1.

Table 1. Composition of flotation process water used in in the lab tests Flotation procedure

The study has been done as stepwise rougher flotation with a Denver laboratory flotation machine. The machine is modified and equipped with an automatic froth scraping device and a double lip cell. Apparatus parameters see Table 2. The ore sample is added to the flotation cell and the cell is filled up with synthetic process water (40% solids). Water temperature 19 - 22 °C is used as standard. The rotor speed is constant during the test, 900 rpm.

1. The pulp was conditioned for 2 minutes with Dextrin (Crystal Tex 627M) as depressant (300g/t).

2. The collector solution (1 wt%) was added and conditioned for 2 minutes.

3. Air and automatic froth skimmer were switched on at the same time.

4. The flotation continued for 3 minutes. Water was added continuously by a tube below the pulp surface to keep the right pulp level.

5. The flotation was repeated twice (or three times) from (2) with the only difference being a conditioning time of 1 minute instead of 2.

The froth products and the remaining cell product were dried, weighed and analyzed for content of silicate minerals, defined as insoluble in 25% hydrochloric acid.

The content of acid insoluble remaining in the cell product was then calculated after the first, second and third flotation steps.

Table 2. Flotation machine parameters

Frothing procedure

• conditioning of the depressant, same Dextrin as is used in the flotation, and mineral slurry in the process water for 2 minutes at 900 rpm;

• addition of the collector and conditioning for an additional 2 minutes at 900 rpm;

• aeration at a constant rate of 2,5 L/min;

• the froth formation is monitored for 2 minutes and recorded every 20 seconds, or until the froth height no longer increases, however the minimum time is set to 2 minutes;

• the aeration is stopped and the froth collapse is recorded every 20 seconds until all froth has collapsed.

The results are summarized below in Tables 3 and 4.

Table 3. Flotation results presented as acid insoluble vs iron weight recovery for several collectors in same iron ore

* not always measured

Table 4. Height of the froth after air supply stopped (%)

The results show that the polyester polyquaternary ammonium compound does not work very well. When using this polyester polyquaternary ammonium the froth height remained very low and not much siliceous material was flotated from the iron ore. Also the acid insoluble amount could not be removed to the target level of 1.3%. lsodecyl-6- aminohexanoate sulphate and 2-ethylhexyl-6-aminohexanoate sulphate are as selective as established benchmarks (Table 3) but in comparison with Isodecyloxyprolylamine have much better frothing properties for silicas. Example 2

The process of Example 1 was repeated except that no depressant was employed.

In this Example a collector compound of formula (I) was employed as a 1 wt% solution in 3 tests in which an iron ore with varying silicate content as specified in the Table 5 was used. Table 5 Flotation results when varying the iron silica ore using the same primary collector

Table 5 demonstrates that the primary collector component of formula (I) when used in a process to treat silica ores continues to perform very well independent of the choice of ore type. The results also demonstrate that increasing the dosage of the primary collector component leads to better results for the silicate concentrate

Example 3

The Example 3 illustrates a flotation process employing a collector composition containing a compound of formula (I) and a solvent, respectively, a collector composition containing a compound of formula (I) blended with an addition primary collector component.

The process of the above Example 1 was repeated except that no depressant was employed, employing the collector compositions and siliceous iron ores as indicated in the below Tables 6 and 7.

The results show that the presence of a compound ii, such as a solvent or additional primary collector, improves the grade of the iron concentrate (decreased amount of acid insoluble or Si02) keeping iron recovery at similar level.

Table 6 ore treatment process results using collector compositions containing the primary collector of formula (I) and a solvent (II)

Table 7 ore treatment process results using collector compositions containing the primary collector of formula (I) with an additional primary collector (II)