Field of the invention

The present disclosure relates to the use of a resin as grinding aid for an ore or mineral, wherein the resin is a monomer-based condensation product comprising at least one monomer having an aldehyde moiety and/or being an aldehyde source; and at least one monomer a) having a ketone moiety, or b) being naphthalene sulfonic acid or a salt thereof; and wherein the monomer-based condensation product comprises at least one hetero moiety selected from the group consisting of sulfino, sulfo, sulfonamido, sulfoalkyloxy, sulfinoalkyloxy, phosphono, and phosphonooxy, and/or salts thereof. Background of the invention

Bauxite is one of the widely used natural ores for aluminum production and consists primarily of aluminium oxide-hydroxides (minerals gibbsite, boehmite and diaspore) and iron oxide- hydroxide phases (minerals Goethite and Hematite). In the aluminum processing industry the aluminum oxide-hydroxide phases are being digested by caustic solution in a so-called Bayer process and recrystallized as pure aluminum hydroxide. To make the digestion process as effective as possible the bauxite ore is milled before the digestion step in a wet grinding process using ball and/or rod mills. The bauxite grinding process is usually carried out in spent Bayer liquor, which is a returned solution after the precipitation stage of aluminum hydroxide. Spent Bayer liquor is an extremely alkaline and saline solution, which mainly consists of sodium hydroxide, sodium aluminates, another dissolved salts and organic material. Therefore, the suspension of bauxite in the used Bayer liquor (so-called Bayer slurry) has also a very high salinity and pH value of 13 to 14.

Bauxite grinding is a very energy consuming step of the whole Bayer process, and the throughput of the mill is limited by the pumpability and viscosity of the Bayer slurry. The latter is always very high due to the high solids content used (50 % by wt. and higher of bauxite).

The use of additives to the Bayer slurry at the grinding step of Bayer process is not very widely known. As a rare example of an additive to the Bayer process for bauxite grinding, the bauxite grinding aid "Rheotec GA2" Tecnochem may be mentioned. CYFLOC ^® BXD of Cytec may also be mentioned as an example of a grinding additive. However, CYFLOC ^® BXD is rather used for absorbing the free moisture content of the bauxite and for agglomerating fine particles, than to directly influence the rheology of the Bayer slurry.

The use of non-ionic surfactants, polyglycols, polyglycol ethers, anionic surfactants, and anionic polymers to increase the pumpability of the Bayer slurry is suggested, e.g., in U.S. patent No. 8,628,737 B2.

The general use of polyacrylic or polymethacrylic acid or an anionic derivative thereof as a grinding aid for coal or ores in a liquid medium was suggested by U.S. patent No. 4,162,044.

Finally, also the use of additives in the wet grinding of bauxite to reduce the viscosity of the slurry was suggested, e.g., in WO 2009/093270 A1 . Here, an aqueous suspension of ethylene oxide/propylene oxide copolymer, dioctyl sulphosuccinate and butySene glycol is suggested as additive.

Despite these efforts to make the grinding of bauxite more effective, there still exists a need for a grinding aid that allows for a more effective grinding process. Summary of the invention

It was now surprisingly found that the resins of the present disclosure allow for an increase of the solid content of an ore or mineral, such as bauxite, in an aqueous slurry, e.g. in the Bayer slurry, while maintaining the slurry viscosity, thus allowing for an increased throughput of ore or mineral in the grinding process at the same grinding energy.

The present description relates to the use of a resin as grinding aid for an ore or mineral.

In a first aspect, the present disclosure relates to the use of a resin as grinding aid for an ore or mineral, wherein the resin is a monomer-based condensation product comprising

A) at least one monomer having an aldehyde moiety and/or being an aldehyde source; and

B) at least one monomer a) having a ketone moiety, or b) being naphthalene sulfonic acid or a salt thereof;

and wherein the monomer-based condensation product comprises at least one hetero moiety selected from the group consisting of sulfino, sulfo, sulfonamido, sulfoalkyloxy, sulfinoalkyloxy, phosphono, and phosphonooxy, and/or salts thereof. Preferred embodiments of this aspect are disclosed herein below, in particular in connection with the Examples, as well as in the appendant claims and Figures.

Figures

The present disclosure also refers to the following Figures, wherein:

Fig. 1 shows the shear stress at increasing shear rate of a Bayer slurry with ABL with and without Additive 1 according to Example 1 a;

Fig. 2 shows the shear stress at increasing shear rate of a Bayer slurry with ABL with and without Additive 3 according to Example 1a;

Fig. 3 shows the shear stress at increasing shear rate of a Bayer slurry with SBL with and without Additive 1 according to Example 1 b;

Fig. 4 shows the shear stress at increasing shear rate of a Bayer slurry with SBL with and without Additive 1 according to Example 1 b;

Fig. 5 shows the shear stress at increasing shear rate of a Bayer slurry with ABL with and without Additive 2 according to Example 2a;

Fig. 6 shows the shear stress at increasing shear rate of a Bayer slurry with SBL with and without Additive 4 according to Example 2b;

Fig. 7 shows the shear stress at increasing shear rate of a Bayer slurry with SBL with and without Additive 4 according to Example 2b;

Fig. 8 shows the shear stress at increasing shear rate of a Bayer slurry with SBL with and without Additives 5 and 6 according to Example 2b;

Fig. 9 shows the shear stress at increasing shear rate of a Bayer slurry with SBL with and without Additive 1 and different amounts of bauxite according to Example 3;

Fig. 10 shows the shear stress at increasing shear rate of a Bayer slurry with SBL with and without Additive 2 and different amounts of bauxite according to Example 4;

Fig. 1 1 shows the particle size distribution of bauxite ore sample; and

Fig. 12 shows mill discharge particle size distributions for the tests 1-3. Detailed description of the invention

The present description relates to the use of a resin as grinding aid for an ore or mineral.

Without being bound to any theory, it is assumed that the resins of the description when used as grinding aid in a process for grinding an ore or mineral modify the rheology of the grinding suspension or slurry. Accordingly, in the present description, the terms ^" grinding aid" and "rheology modifier" are used interchangeably.

Furthermore, also the terms "grinding suspension", "grinding slurry", "suspension", and "slurry ^" are used interchangeably in the present description when referring to a suspension of solid particles used in a grinding process, such as the Bayer process for grinding bauxite.

In a first aspect, the present disclosure relates to the use of a resin as grinding aid for an ore or mineral, wherein the resin is a monomer-based condensation product comprising

A) at least one monomer having an aldehyde moiety and/or being an aldehyde source; and

B) at least one monomer a) having a ketone moiety, or b) being naphthalene sulfonic acid or a salt thereof;

and wherein the monomer-based condensation product comprises at least one hetero moiety selected from the group consisting of sulfino, sulfo, sulfonamido, sulfoalkyloxy, sulfinoalkyloxy, phosphono, and phosphonooxy, and/or salts thereof.

The resins of the present disclosure thus are a polymerization product obtained by

polycondensation of a monomer mixture, the monomer mixture comprising at least two types of monomers, namely (monomeric) components A and B, and component A and/or component B comprise at least one hetero moiety, or such hetero moiety is introduced into the resin by a compound providing a hetero moiety, wherein the hetero moiety is selected from the group consisting of sulfino, sulfo, sulfonamido, sulfoalkyloxy, sulfinoalkyloxy, phosphono, and phosphonooxy, and/or salts thereof. It is understood that when naphthalene sulfonic acid, or a salt thereof, is used as one of the monomeric components, i.e., component B, a sulfo group is present in the resins. However, also the aldehyde moiety of component A or the ketone moiety of component B may provide such hetero moiety, or a hetero moiety is introduced into the resin by a compound providing the hetero moiety, such as, e.g., in Additives 2 and 4 given above. Without being bound to any theory, it is surmised that the presence of such hetero moiety provides beneficial properties to the resins of the present disclosure when used as grinding aid for grinding an ore or mineral, in particular reducing the shear stress of a dispersion of an ore or mineral, thus allowing for the milling or grinding of a dispersion of an ore or mineral with a higher solid content at a constant shear stress.

In a preferred embodiment, the resin consists of components A and B, and wherein the monomer-based condensation product comprises at least one hetero moiety.

In another preferred embodiment, the resin consists of components A and B, and wherein the monomer-based condensation product comprises at least one hetero moiety, wherein only a single representative of each component is present. In other words, only one species of compounds A and B is present in the resin in accordance with this embodiment of the present disclosure.

The preferred embodiments of the present disclosure relating to the different components, the amounts thereof, and also additional compounds used in the use are independent of each other, and these embodiments are thus freely combinable as understood by the skilled person. As an example, if one preferred embodiment relates to a specific aldehyde for component A, and another preferred embodiment relates to a specific ketone for component B, a still other preferred embodiment relates to the combination thereof, i.e., the specific aldehyde compound for component A in combination with the specific component B.

In a preferred embodiment, the at least one monomer having an aldehyde moiety and/or being an aldehyde source (component A) is selected from the group consisting of paraformaldehyde, formaldehyde, acetaldehyde, 1 ,3,5-trioxane, butyraldehyde, glyoxal, glutaraldehyde,

furfurylaldehyde, benzaldehyde, naphthylaldehyde, sulfonaphthaldehyde and mixtures thereof, and preferably is formaldehyde. In particular, the monomer being an aldehyde source may be selected from the group consisting of paraformaldehyde, 1 ,3,5-trioxane, and paraldehyde.

Paraformaldehyde and 1 ,3,5-trioxane are sources of formaldehyde, and paraldehyde of acetaldehyde.

In another embodiment, component B comprises at least one monomer having a ketone moiety being selected from the group consisting of methyl ethyl ketone, acetone, diacetone alcohol, ethyl acetoacetate, laevulinic acid, methyl vinyl ketone, mesityl oxide, 2,6-dimethyl-2,5- heptadien-4-one, acetophenone, 4-methoxyacetophenone, 4-acetylbenzenesulfonic acid, diacetyl, acetylacetone, benzoylacetone, cyclohexanone and mixtures thereof. In a preferred embodiment, the monomer having a ketone moiety is cyclohexanone or acetone, more preferably cyclohexanone.

It is understood that, in accordance with some embodiments of the present disclosure, also combinations of the monomers given for component A and/or B may be used.

The resin of the present disclosure comprises at least one hetero moiety selected from the group consisting of sulfino, sulfo, sulfonamido, sulfoalkyloxy, sulfinoalkyloxy, phosphono, and phosphonooxy, and/or salts thereof. Said hetero moiety may be introduced into the resin of the present disclosure either during the condensation reaction of at least components A and B, or afterwards by reacting the condensation product not containing such hetero moiety. When introducing the hetero moiety, a suitable hetero moiety containing compound may be used, or a compound providing such hetero moiety may be present during the condensation reaction, or the condensation product may be reacted with a compound providing a hetero moiety, thus preparing the final resin comprising a hetero moiety. In an exemplary embodiment, the hetero moiety may be provided by an acid or acid salt, such as, e.g., by sulfurous acid, sodium hydrogen sulfite, or sodium sulfite for the sulfo group. If the hetero moiety is a phosphono group, this group may be introduced by dialkylphosphonate (HP(=0)(OR)2) reagent in a Kabachnik-Fields like reaction with the subsequent hydrolysis of ester groups.

In a preferred embodiment, said at least one hetero moiety is selected from the group consisting of sulfino, sulfo, sulfonamido, sulfoalkyloxy, and sulfinoalkyloxy, and preferably said at least one hetero moiety is sulfo.

In still another embodiment, the molar ratio of component A : component B is 1 : 0.8-3.5, preferably 1 :0.9-2.5.

In still another embodiment, the molar ratio of component A : hetero moiety is 1 : 0,8-3,5, preferably 1 :0,9-2,5. It is understood that the molar ratio of the "hetero moiety" is the molar ratio in reaction mixture. As such, if the molar ratio of component A to the hetero moiety is 1 : 1 , equal amount of component A and the hetero moiety are present in the reaction mixture.

In general, if the molar ratio of two components is given, it refers to the ratio of the two components as present in the reaction mixture.

In another embodiment, the resin has a molecular weight Mw of between 1 000 and

50 000 g/mol, preferably of between 2 000 and 30 000 g/mol.

In still another embodiment, the resin is a formaldehyde / cyclohexanone condensation product comprising a sulfo moiety. According to this embodiment, the resin may be a condensation product of only formaldehyde and cyclohexanone, or a condensation product of formaldehyde and cyclohexanone also comprising other monomers, such as another aldehyde, ketone or naphthalene sulfonic acid or a salt thereof, the final resin also comprising a sulfo moiety.

In a further embodiment, if component B has a ketone moiety (i.e., option a), the monomers are reacted at a pH-value of 8 to 14 when obtaining the resin, and if component B is naphthalene sulfonic acid or a salt thereof (i.e., option b), the monomers are reacted at a pH-value of 0 to 5 when obtaining the resin.

In still a further embodiment, the reaction for the preparation of the resin is carried out without any solvent, i.e. as bulk polymerization, in water or in a mixture of water and a polar organic solvent.

In accordance with the present disclosure, the resins are used as aid for grinding ores and/or minerals. It is understood that the resins disclosed herein may be used alone or as a mixture of different resins, and even in mixture with other grinding aids.

It is preferred according to the present disclosure that the resin is used as grinding aid in an aqueous suspension or aqueous slurry of an ore and/or mineral. The ore or mineral is thus suspended in water as solvent, and the grinding is a wet grinding. The resin is then added to the slurry or suspension, or it may be present in the water prior to the addition of the ore or mineral.

In one embodiment, the resin is used in the aqueous suspension or aqueous slurry in an amount of from 0.001 % to 5 % by wt., preferably of from 0.01 % to 0.5 % by wt., based on the total amount of ore or mineral. The amount of resin added is thus preferably determined based on the amount of ore or mineral, and not based on the amount of solvent, such as water.

The resin of the present disclosure may be used as grinding aid for any ore or mineral. In one embodiment, the ore or mineral is selected from the group of an Al containing ore or mineral, a Fe containing ore or mineral, a Cu containing ore or mineral, a Mo containing ore or mineral, an Au containing ore or mineral, or mixtures thereof. In a preferred embodiment, the ore or mineral is an Al containing ore or mineral, and preferably the resin is used as grinding aid to improve the grinding of a bauxite containing slurry during the grinding stage of an alumina extraction process, preferably in an alumina extraction process using a Bayer process.

For the milling or grinding of the ore or mineral, any conventionally known process may be used. As such, in one embodiment, the ore or mineral may be ground in a wet milling process using milling balls for grinding.

It was now surprisingly found that the resins of the present disclosure allow for an increase of the solid content of an ore or mineral, such as bauxite, in an aqueous slurry, e.g. in the Bayer slurry, while maintaining the slurry viscosity, thus allowing for a increased throughput of ore or mineral in the grinding process at the same grinding energy. This is illustrated in more detail in the Examples below.

Definitions:

The grinding aids of the present application are used for grinding ores and minerals. As used herein, the term "ores and minerals" refers to any metal containing ore or mineral. In a preferred embodiment, the term "ores and minerals" does not comprise mineral binders, such as clinker, cement, slag and fly ash. In another embodiment, the ores and minerals are selected from the group consisting of Al containing ore or mineral, Fe containing ore or mineral, Cu containing ore or mineral, Mo containing ore or mineral, Au containing ore or mineral and mixtures thereof. In another preferred embodiment, the term "ores and minerals" comprises aluminum and/or iron ores and minerals, in particular aluminum ores and minerals, preferably bauxite. In still another preferred embodiment, the term "ores and minerals" refers to aluminum and/or iron ores and minerals, in particular aluminum ores and minerals, preferably bauxite. As used herein, the term "naphthalene sulfonic acid" refers to 1 -naphthalene sulfonic acid, 2-naphthaiene sulfonic acid, or a mixture thereof. The corresponding salts thus refer to C10H7-SO2OM wherein M is, independently, selected from alkali metals, alkaline earth metals, ammonium and organic ammonium ions, and s is 0.5, or 1 , depending on the charge of M, to result in a neutral molecule.

As used herein, the term "naphthylaldehyde ^" or "naphthaldehyde" refers to 1-naphthaldehyde, or 2-naphthaldehyde, or a mixture thereof.

As used herein, the term "sulfonaphthaldehyde" refers to a sulfonated naphthylaldehyde, i.e., a naphthylaldehyde being additionally substituted by a sulfonic acid group.

As used herein, the term "benzoylacetone" refers to 1 -phenyl-1 ,3-butanedione.

As used herein, the term "sulfino" refers to the group -S(=0)OH, or a salt thereof. In other words, a -S(0)OM _s group is referred to, wherein M is selected from hydrogen, alkali metals, alkaline earth metals, ammonium and organic ammonium ions, and s is 0.5, or 1 , depending on the charge of M, to result in a neutral molecule.

As used herein, the term "sulfo" refers to the group -S(=0)20H, or a salt thereof. In other words, a -SC OMs group is referred to, wherein M is selected from hydrogen, alkali metals, alkaline earth metals, ammonium and organic ammonium ions, and s is 0.5, or 1 , depending on the charge of M, to result in a neutral molecule.

As used herein, the term "sulfamido" refers to the -S(=0)2-NR'R", wherein R' and R" are, independently, selected from hydrogen, Ci-Ci-alkyl or -(Ci-Ci-alkyl)-(5- to 10-membered)aryl. Preferably, both R' and R" are hydrogen.

As used herein, the term "sulfoalkyloxy" refers to the group -S(=0)20R ¹ , wherein R ¹ is a C1-C10 alkyl, preferably a C ₁ -C4 alkyl or a (5- to 10-membered)aryl.

As used herein, the term "sulfinoalkyloxy" refers to the group -S(=0)OR ¹ , wherein R ¹ is a C1-C10 aikyl, preferably a C1-C4 aikyl or a (5- to 10-membered)aryl.

As used herein, the term "phosphono" refers to the group -P(=0)(OH)2, or a salt thereof. In other words, a -P(=0)(OM _p )2, or -PC Mp group is referred to, wherein M is, independently, selected from hydrogen, alkali metals, alkaline earth metals, ammonium and organic ammonium ions, and p is 0.5, 1 or 2, depending on the charge of M, to result in a neutral molecule.

As used herein, the term "phosphonooxy" refers to the group -0-P(=0)(OH)2, or a salt thereof. In other words, a -0-P(=0)(OM _p ) ₂ , or -OPO3M., group is referred to, wherein M is,

independently, selected from hydrogen, alkali metals, alkaline earth metals, ammonium and organic ammonium ions, and p is 0.5, 1 or 2, depending on the charge of M, to result in a neutral molecule.

As used herein, the term "polar organic solvent" refers to an organic solvent having a dielectric constant of more than 15, and are preferably composed of carbon, hydrogen, nitrogen, oxygen and sulfur atoms. In one embodiment, the polar organic solvent is an alcohol or an acid ester. Exemplary embodiments of polar organic solvents include, but are not limited to,

tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, formic acid, methanol, ethanol, n-propanol, isopropanol, n- butanol, and acetic acid.

As used herein, the term "C1-C10 alkyl" refers to a straight-chained or branched saturated hydrocarbon group having 1 to 10 carbon atoms, e.g. methyl, ethyl, propyl, 1 -methylethyl, butyl, 1- methylpropyl, 2-methylpropyl, 1 ,1 -dimethylethyl, pentyl, 1 -methylbutyl, 2-methylbutyl, 3- methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1 ,1 -dimethylpropyl, 1 ,2-dimethylpropyl, hexyl, 1- methyl pentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1 ,1-dimethylbutyl, 1 ,2- dimethylbutyl, 1 ,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1- ethylbutyl, 2-ethylbutyl, 1 ,1 ,2-trimethylpropyl, 1 ,2,2-trimethylpropyl, 1 -ethyl-1 -methylpropyl and 1-ethyl-2-methylpropyl. In one embodiment, the C1-C10 alkyl is a d-Ce-alkyl or a Ci-C4-alkyl. A preferred embodiment of a C1-C10 alkyl is a Ci-C4-alkyl. It is understood that the term "d-Ce- alkyl ^" refers to a straight-chained or branched alkyl group having 1 to 6 carbon atoms. Likewise, the term "CrC4-alkyl" refers to a straight-chained or branched alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, propyl (n-propyl), 1-methylethyl (iso-propyl), butyl, 1-methylpropy! (sec. -butyl), 2-methylpropyl (iso-butyl), 1 ,1 -dimethylethyl (tert. -butyl).

As used herein, the term "alkali metal" refers to the alkali metals selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and caesium (Cs). In one embodiment, the alkali metal is selected from sodium and potassium.

As used herein, the term "alkaline earth metal" refers to the alkali metals selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). In one embodiment, the alkali metal is selected from magnesium and calcium.

As used herein, the term "ammonium" refers to the ammonium ion, i.e., NH ₄ ⁺ .

As used herein, the term "organic ammonium ions" refers to ammonium ions having at least one organic substituent. In one embodiment, the organic ammonium ions have the formula

NH _b R ^a (4-b) ⁺ , wherein b is an integer selected from 0, 1 , 2, and 3, and R ^a is, independently for each occurrence in the ammonium ion, a Ci-Cio-alkyl, (5- to 10-membered)aryl, which aryl may optionally be substituted by 1 to 3 Ci-Cio-alkyl, or C2-C3-hydroxyalkyl (preferably 2-hydroxyethyl or 2-hydroxypropyl). The organic ammonium ion has a single, positive charge.

Molecular weight averages (Mz, Mw and Mn), Molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI= Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight) may be determined by Size Exclusion Chromatography (SEC) (PEG/PEO calibration, Rl detection, column combination OH- Pak SB-G, OH-20 Pak SB 804 HQ und OH-Pak SB 802.5 HQ from Shodex, Japan; eluent 80 Vol.-% aqueous ammonium form i ate solution (0,05 mol/l) und 20 Vol.-% acetonitrile; injection volume 100 μΙ; flow rate 0,5 ml/min).

Experimental Part

Examples and Additives not falling under the appendant claims, in particular Examples using such Additives not falling under the appendant claims, are reference examples and reference Additives. Characterization of raw material bauxite ore

Bauxite grinding experiments of the present application were made with raw bauxite ore.

XRD Analysis

The composition of the bauxite used for the present experiments as determined by XRD (Bruker, D4, Cu Ka) and Rietveld analysis is given in Table 1.

Table 1 Phase composition of bauxite ore.

Particle size distribution (PDS) of the raw material

The particle size distribution of the bauxite ore as received (the raw ore) was analyzed sieving the raw material over a sieve tower with sieves of different mesh size (Table 2).

Table 2 Particle size distribution of bauxite ore as received.

Bayer liquor

Bauxite slurries for grinding and rheology experiments were performed with (1 ) an artificial Bayer Liquor (ABL) and (2) with spent Bayer liquor (SBL) from an industrial process. The ABL was prepared as a highly alkaline and saline solution of sodium hydroxide and sodium aluminate as follows: 124 g NaOH and 131 g NaAIO? were dissolved in the solvent (H2O) to yield in 1 liter of solution, i.e., per liter of solution.

The composition of the SBL was analyzed with optical emission spectroscopy combined with inductive coupled plasma (ICP-OES), the total organic carbon (TOC) content was measured, and also the dry residue was analyzed with elemental analysis. The results are given in Table 3.

Table 3 Composition of spent Bayer liquor

Slurry preparation and Bauxite grinding

Reference system: ore grinding in planetary ball mill; Particle size investigation

Grinding of bauxite at a concentration of 65 wt.% solid in ABL without additive and with Additive 1 with a dosage of 0.5 wt.%, based on the amount of bauxite, was performed in a planetary ball mill at 400 rpm for 6 minutes with stainless steel balls with a diameter of 2 cm in steel beakers. The particle size distribution was measured in water via static light scattering with a astersizer by Malvern. Results are given in Table 4. No significant differences in particle size distribution are found for slurries ground with or without additive for these small particle sizes.

Table 4 Particle size distribution of bauxite ground with and without Additive 1

Rheology measurements of bauxite slurries

Rheology measurements of the ground bauxite slurries were carried out using a plate-plate geometry of 2.5 cm diameter with a slit height of 1 mm and by applying a shear rate ramp of from 0.01 up to 500 1/s (Anton Paar MCR 301 Rheometer). The dosages of additives are given in wt.-% with respect to bauxite solid content. To account for addition of water by aqueous polymer solution addition, reference samples were prepared, adding the same amount of water which would be introduced by polymer solutions to estimate the influence of water addition. These are called "Blank". In SBL-based slurries, if no water was added to account for the water added by dosing the additive, but only SBL (to reach the same bauxite weight content level), the sample is called "Reference ^" . The Blank or Reference gives the reference value in relation to the respective sample, stemming from one milling batch split into 50 g aliquots, if not stated otherwise, since samples from one batch can be compared more reliably.

With respect to the Blank and Reference values given in the tables below, it may be added that Blanks and References were prepared from different batches, and there are always some minor differences in solid content, such as due to non-grindable coarse particles. A comparison should thus be based on the values within one table (stemming from the same milling batch), and not between different tables. The results are given as the mean value of aliquots from different milling batches each for the comparison (number of batches indicated in the table), or as a single measurement value.

Example 1a: Rheology of different additives with ABL - Additive addition after grinding

Artificial Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 1 (added as a 25 wt.-% aqueous solution), or the respective amount of deionized water (called "Blank"), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Results at a shear rate of 500 1 /s are given in Table 5, rheological curves are given in Figure 1 .

Table 5 Rheological measurements with Additive 1 and ABL, added after grinding

The same process was repeated for another batch using Additive 3 instead of Additive 1 (Figure 2 and Table 6), however, only with one aliquot. Table 6 Rheological measurements with Additive 3 and ABL, added after grinding

Example 1b: Rheology of Additive 1 with SBL - Additive addition after grinding

Spent Bayer liquor and bauxite were ground in a planetary ball mil! for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 1 (added as a 25 wt.-% aqueous solution), the respective amount of deionized water (called "Blank") or the respective amount of SBL (called

"Reference"), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Results at a shear rate of 500 1/s are given in Table 7, rheological curves are given in Figure 3 and Figure 4. It is understood that a comparison should only be made between experiments based on the same batch of slurry, i.e., between the first two lines and the last two lines of Table 7.

Table 7 Rheological measurements with Additive 1 and SBL, added after grinding

Example 2a: Rheology of Additive 2 with ABL - Additive addition after grinding

Artificial Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 2 (added as a 25 wt.-% aqueous solution), or the respective amount of deionized water (called Blank ^" ), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Results at a shear rate of 500 1 /s are given in Table 8, rheological curves are given in Figure 5. Table 8 Rheological measurements with Additive 2 and ABL, added after grinding

Example 2b: Rheology of different additives with SBL - Additive addition after grinding

Spent Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 4, 5 or 6, respectively, (added as a 25 wt.-% aqueous solution), the respective amount of deionized water (called "Blank") or the respective amount of SBL (called "Reference"), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Results are given at a shear rate of 500 1/s.

This process was performed for different batches of slurries using Additive 4 (Figure 6 and Table 9; Figure 7 and Table 10), Additive 5, or Additive 6 (Figure 8 and Table 1 1 ), respectively.

Table 9 Rheological measurements with Additive 4 and SBL, added after grinding

Table 10 Rheological measurements with Additive 4 and SBL, added after grinding

Sample Additive Liquid Shear stress Shear stress reduction

dosage at 500 1/s [Pa] mean at 500 1/s as

[wt%] compared to the

reference [%]

Reference 1 SBL SBL 890 -

Additive 4 0.5 SBL 666 25 Table 1 1 Rheological measurements with Additives 5 and 6 and SBL, added after grinding

Example 3: Rheology at different solid contents using Additive 1

Spent Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 1 (added as a 25 wt.-% aqueous solution), the respective amount of deionized water (called "Blank ^" ) or the respective amount of SBL (called

"Reference"), were added (yielding solid bauxite contents between 55 and 70 wt.-%) and mixed for 5 minutes before rheological properties were measured. Results at a shear rate of 53 and 500 1/s are given in Table 12.

With Additive 1 the shear stress at 53 1/s can be reduced by (60±7) % as compared to the reference at different solid contents. Thus, with Additive 1 at 0.5 wt.-% dosage with respect to bauxite, the solid content can be increased by about 5 wt.-% without increasing shear stress (see also Figure 9).

Example 4: Rheology at different solid contents using Additive 2

Spent Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 2 (added as a 25 wt.-% aqueous solution), the respective amount of deionized water (called "Blank") or the respective amount of SBL (called

"Reference"), were added (yielding solid bauxite contents between 55 and 70 wt.-%) and mixed for 5 minutes before rheological properties were measured. Results at a shear rate of 53 and 500 1/s are given in Table 13.

With Additive 2 the shear stress at 53 1/s can be reduced by (33±10) % as compared to the reference at different solid contents. Thus, with Additive 2 at 0.5 wt.-% dosage with respect to bauxite, the solid content can be increased by about 2.5 wt.-% without increasing shear stress (see also Figure 10). Table 12 Rheological properties of Bayer slurry as a function of solid content and shear stress reduction with Additive 1

Table 13 Rheological properties of Bayer slurry as a function of solid content and shear stress reduction with Additive 2

Example 5: Rheology at different temperatures with Additive 1 and SBL

Spent Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 1 (added as a 25 wt.-% aqueous solution), the respective amount of deionized water (called "Blank") or the respective amount of SBL (called

"Reference"), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Slurries were measured in plate-plate geometry in a humidity chamber to avoid evaporation of water during heating and equilibration.

Measurements were performed at a shear rate of 200 1/s for 20 sec. Results are given in Table 14.

Table 14 Rheological properties with Additive 1 and SBL as a function of temperature

Example 6: Dose efficiency of Additive 1 in SBL

Spent Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, different amounts (0.015, 0.05, 0.5 wt.-%, based on the amount of bauxite) of Additive 1 (added as a 25 wt.-% aqueous solution), the respective amount of deionized water (called "Blank") or the respective amount of SBL (called "Reference"), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Slurries were measured in plate-plate geometry. Results at a shear rate of 500 1/s are given in Table 15. Table 15 Dose efficiency of Additive 1 with SBL

Example 7: Dose efficiency of Additive 3 in ABL

Artificial Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, different amounts (wt.-% as indicated in Table 16 below, based on the amount of bauxite) of Additive 3 (added as a 25 wt.-% aqueous solution) were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Slurries were measured in plate- plate geometry. Results at a shear rate of 500 1/s are given in Table 16.

Table 16 Dose efficiency of Additive 3 with ABL

Additive Viscosity Viscosity reduction at

Sample Additive dosage Liquid at 500 1/s 500 1/s as compared

[wt.-%] [mPas] to Reference 1 [%]

Blank 1 water 2.96 ABL 616 -

Additive 3

Additive 3 0.15 ABL 529 14

and water

Additive 3

Additive 3 0.37 ABL 465 25

and water

Additive 3

Additive 3 0.74 ABL 365 41

and water

Additive 3

Additive 3 1.48 ABL 314 49

and water

Additive 3

Additive 3 2.22 ABL 298 52

and water

Additive 3 Additive 3 2.96 ABL 299 51 Spent Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, different amounts (0.015, 0.05, 0.5 wt.%, based on the amount of bauxite) of the indicated Additive (added as a 25 wt.-% aqueous solution), the respective amount of deionized water (called "Blank") or the respective amount of SBL (called "Reference"), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. Slurries were measured in plate-plate geometry. Results at a shear rate of 500 1/s are given in Table 17. Table 17 Dose efficiency of additives in Bayer slurry with spent Bayer liquor.

Example 9: Formulations with MPEG 500 and Additives 1 and 3 in ABL

Artificial Bayer liquor and bauxite were ground in a planetary ball mill for 6 minutes at 400 rpm. Afterwards, from one milling batch, the slurry was split into 50 g aliquots since samples from one batch can be compared more reliably. To these aliquots of the slurry, 0.5 wt.-%, based on the amount of bauxite, of Additive 1 or 3 (added as a 25 wt.-% aqueous solution), or the respective amount of deionized water (called "Blank"), were added (yielding a 65 wt.-% solid bauxite content) and mixed for 5 minutes before rheological properties were measured. When MPEG was added, an additive formulation was prepared containing the additive and the given amount of MPEG (in wt.-%, based on the amount of additive). A 25 wt.-% aqueous solution was prepared from the additive formulation, which solution was then added. Results at a shear rate of 500 1/s are given in Table 18. Table 18 Rheological properties with formulations of Additives 1 and 3 with MPEG 500

Energy Efficiency and Rheology experiments with bauxite ground in a big ball mill at the conditions close to industrial

These experiments aim to determine the effect of each chemical additive in the performance of the grinding process. The ore samples were ground at different dosages of each additive, and the resulting viscosity and particle size distribution are measured in every step. For grinding the samples, a 2 L stainless-steel laboratory scale ball mill was used, filled with a suitable ball string calculated to produce the maximum efficiency given the particle size distribution of the feed sample. This method is scalable to real plant conditions, since the main controlling variable of the mill's grinding energy efficiency is the Specific Surface Area a (m ² of ball surface/m ³ balls) exposed by the ball charge for impact and abrasion of the ore particles, regardless of the actual combination of sizes that make up the 'string' of balls in the charge (Sepulveda, J.E. (2007). SPEC - a pseudo-empirical correlation for the assessment of the ideal ball size for conventional and sag milling applications. Proceedings Workshop SAG2007 Conference. Vina del Mar, Chile). The main variables during grinding were: mill volume, V = 2 L; load volume, J = 33 %; speed, N=75 % of critical (91 rpm); interstitial powder filling, U = 0.6; sample size, W = 150 g; solids content in Bayer slurry = 65% w/w; grinding time, t = 8 min, equivalent to specific energy consumption, E = 5 kWh/t for all cases. In all experiments, the liquid phase is spent Bayer liquor (SBL). The liquid part of all the polymer solutions is double- distilled water.

With the bauxite ore samples, product size distributions were determined after batch grinding tests. Since the characteristic values of the feed and product sizes (F80 and P80) and the specific energy consumption (E = 5 kWh/t) are known in each case, the energy required to perform the comminution task of converting a given mass of ore from a particular F80 to P80, is defined as (F.C. Bond, "Testing and Calculations" Ch.5, Section 3A, SME Mineral Processing Handbook, N.L. Weiss editor, (1985), p 3A-18):

_E_

Op. Work Index (OWi) = 10

(1/VP80 - 1/VF80)

Figure 1 1 represents the particle size distribution of Bayer slurry before milling.

Figure 12 represents the particle size distributions of Bayer slurry after milling using the batch mill for the cases without and with 500 g/Ton of Additive 1 in spent Bayer Liquor in identical milling conditions. Tests 2 and 3 are identical test made to show reproducibility.

Table 19 summarizes the calculation and comparison of resulting operational work indexes values (OWi) obtained using the batch mill for both without and with 500 g/Ton of Additive 1 .

Table 19 Summary of batch grinding test results with Additive 1 at the dosage 500 g/ton

Solids Specific Energy

F80 P80 OWi

Test No. Content Additive Nr. Energy Savings

(microns) (microns) (kWh/t)

(%) (kWh/t) (%)

1 65 None 3524 273 5 1 1 .4 0

2 65 Additive 1 3524 243 5 10.6 7.7

3 65 Additive 1 3524 239 5 10.5 8.7 Synthesis of additives

Synthesis of Additive 1

Phenoxyethanol (124.31 g) was placed into 1 L double wall heatable glass reactor equipped with reflux condenser and mechanical stirrer, followed by slow addition of polyphosphoric acid (1 15 % based on H3PO4, 67.50 g) through a drop funnel (about 10-15 Min, the temperature was controlled not to exceed 40 °C). The resulting mixture was heated to 100 C and kept at this temperature over 1 h. Then 100 % methanesulfonic acid (Lutropur ^® MSA of BASF, 31 .79 g) was added to the reaction mixture, followed by the addition of 30 % aqueous formaldehyde solution (85.8 g) via syringe pump over about 80 min, keeping the reaction temperature above 97 C. The resulting polymer solution was further heated for 24 min, and then MPEG 500

(49.95 g) was added to stop the polycondensation, followed by addition of cold water (559.16 g) and 50 % aqueous NaOH solution for the neutralization to pH of 6.5.

The molecular weight of the resulting polymer was analyzed by SEC (PEG/PEO calibration, Rl detection, column combination OH-Pak SB-G, OH-20 Pak SB 804 HQ und OH-Pak SB 802.5 HQ from Shodex, Japan; eluent 80 Vol.-% aqueous ammonium formiate solution (0,05 mol/l) und 20 Vol.-% acetonitrile; injection volume 100 μΙ; flow rate 0,5 ml/min).

SEC-data: Mw = 9,8 kDa, Mn = 6,4 kDa, PDI = 1 ,52. (MPEG 500 peak is well separated from the polymer peak).

Synthesis of Additive 3

Phenoxyethanol (75.99 g) was placed into a 1 L heatable glass reactor equipped with reflux condenser and mechanical stirrer, followed by slow addition of polyphosphoric acid (1 15 % based on H3PO4, 54.96 g) through a drop funnel over 100 min (the temperature was maintained below 40 C). The resulting mixture was heated to 95 C and kept at this temperature for 1 h. Then, polyethyleneglycol phenyl ether ("Pluriol A 750 PH", Mw = 750 g/mol, 1 12.50 g) and paraformaldehyde (24.89 g) were added to the reaction mixture, followed by the addition of 70 % methanesulfonic acid (Lutropur ^® MSA of BASF, 28.83 g) over 30 min via syringe pump, and keeping the reaction temperature above 97 C. The resulting polymer solution was further heated for 3 h at about 100 C Then, water (300 g) was added, followed by reflux over 30 min. After cooling to 60 °C, the polymer solution was neutralized by 50 % aqueous NaOH solution to a pH of 6.5.

The molecular weight of the polymer was analyzed with SEC (details see above at Additive 1 ). SEC-data: Mw = 14,4 kDa, Mn = 7,7 kDa, PDI = 1 ,77.

Synthesis of Additive 2

Water (40 g) was placed into a heatable double wall reaction vessel equipped with reflux condenser, thermometer and pH-meter. 30 wt-% aqueous formaldehyde solution (1 .28 mol) was mixed with sodium sulfite (0.27 mol) and cyclohexanone (0.61 mol) and added to the water. The pH was adjusted with 50 wt-% aqueous sodium hydroxide (NaOH) solution to a pH of 13.5. The viscous mixture was heated to reflux for 3 hours. After cooling to room temperature, formic acid was used to adjust the pH to 10. The molecular weight of the polymer was analyzed with SEC (the method details see in the synthetic procedure for Additive 1 ) and viscosimetry.

SEC-data: Mw = 28.6 kDa, Mn = 20.8, PDI = 1 .38. Synthesis of Additive 4

In the same manner as for Additive 2 above, Additive 4 was prepared by using 0.56 mol cyclohexanone instead of 0.61 mol, and KOH for pH adjustment instead of NaOH.

SEC-data: Mw = 32.7 kDa; Mn = 19.7 kDa; PDI = 1 .66. Synthesis of Additive 5

Calcium salt of naphthalene sulfonate-formaldehyde condensate was prepared according to well-known conventional synthetic procedures described for example in BASF patent DE292531 (1913) and in Yan et al., "Synthesis, Separation and adsorption of naphthalene sulphonate formaldehyde condensates", Tenside Surf. Det. 42 (2005), 02-105. As a base for

neutralization, calcium hydroxide was used. The molecular weight of the polymer was analyzed with SEC (the method details see in the synthetic procedure for Additive 1 ):

several polymer and oligomer peaks:

1 ) Mw = 12,6 kDa, Mn = 9,4 kDa, PDI = 1 ,33;

2) Mw = 2,2 kDa, Mn = 2,0 kDa, PDI = 1 ,08;

3) Mw = 0,87 kDa, Mn = 0,82 kDa, PDI = 1 ,06.

Synthesis of Additive 6

Sodium salt of naphthalene sulfonate-formaldehyde condensate was prepared according to well-known conventional synthetic procedures described for example in BASF patent DE292531 (1913) and in Yan et al., "Synthesis, Separation and adsorption of naphthalene sulphonate formaldehyde condensates ^" , Tenside Surf. Det. 42 (2005), 102-105. The molecular weight of the polymer was analyzed with SEC (the method details see in the synthetic procedure for Additive 1 ): several polymer and oligomer peaks

1 ) Mw = 9,8 kDa, Mn = 8,5 kDa, PDI = 1 ,15;

2) Mw = 2,2 kDa, Mn = 2,1 kDa, PDI = 1 ,06;

3) Mw = 0,95 kDa, Mn = 0,91 kDa, PDI = 1 ,04.