RECOVERY IN MINING APPLICATIONS

FIELD OF THE INVENTION

[0001] This invention relates to froth flotation. Specifically this invention relates to collectors for use in froth flotation that provide enhanced mineral recovery.

BACKGROUND OF THE INVENTION

[0002] Froth flotation is a process which separates hydrophobic materials from hydrophilic materials, and is utilized in industries such as mining, waste water treatment, and paper recycling.

[0003] In the mining industry, froth flotation is utilized to separate desired minerals from otherwise unwanted mined ore (known as "gangue"). The process typically involves first crushing and grinding the ore so that the various minerals exist as physically separate grains. The ground ore is then mixed with water to form a slurry and the desired mineral is rendered hydrophobic by the addition of a surfactant chemical, known as a collector. The particular chemical depends on the nature of the mineral to be recovered and/or the waste minerals. Commonly used collectors include anionic sulfur ligands such as xanthate salts, which include potassium amyl xanthate, potassium isobutyl xanthate, potassium ethyl xanthate, sodium isobutyl xanthate, sodium isopropyl xanthate, and sodium ethyl xanthate. Other collectors include sulfur- based ligands such as dithiophosphates and dithiocarbamates, thiourea thiocarbanilide, fatty acids, and fatty amines.

[0004] The resulting slurry (commonly referred to as a pulp) of hydrophobic particles and hydrophilic particles is introduced to tanks known as flotation cells that are aerated to produce bubbles. The hydrophobic particles attach to the air bubbles, which rise to the surface, forming a froth. The froth is removed from the cell, producing a concentrate of the target mineral.

[0005] Frothing agents, known as frothers, may be introduced to the pulp to promote the formation of a stable froth on top of the flotation cell. Commonly used frothers include pine oil, various alcohols (methyl isobutyl carbinol (MIBC)), polyglycols, and xylenol (cresylic acid).

[0006] The minerals that do not float into the froth are referred to as the flotation tailings or flotation tails. These tailings may be subjected to further froth flotation to recover additional desired minerals in a process known as scavenging. The final tailings after scavenging are typically discarded.

[0007] Methods of froth flotation are known in the art. U.S. Patent No. 2,278,060 discloses a froth flotation promoter incorporating the reaction products of polyalkylene polyamines with fatty acids or fatty acid glycerides or other esters, as well as the substantially water soluble salts of such products. Separately, U.S. Patent No. 2,857,331 discloses a froth flotation promoter comprising "a polymerization condensation reaction product resulting from heating a mixture containing (1) from 2.5 to 18 molecular equivalents of a commercially crude heterogeneous product such as crude tall oil, tall oil pitch or equivalent crude fatty product of vegetable or animal origin and (2) one molecular equivalent of a commercial alkylene polyamine or a polyalkylene polyamine, herein collectively referred to as a commercial polyamine. Preferably the two reacting components are tall oil pitch, or crude tall oil, and commercial diethylene triamine."

[0008] U.S. Patent No. 3,009,575 teaches a froth flotation process to collect KCL from sylvite utilizing a fatty imidazoline collector, while U.S. Patent No. 4,276,156 teaches a process to collect phosphate from silica utilizing a collector prepared by condensing a mixture of a fatty acid or ester and ethanolamine and hydroxyethylethylenediamine. U.S. Patent No. 4,301,004 teaches a froth flotation method utilizing N-aminoethylpiperazine with a fatty acid or fatty acid ester that improves the separation of phosphate from silica. The patent discloses that separation is further improved in the presence of a co-collector consisting of a polyethylenepolyamine condensed with a fatty acid. WO 1987/03222 also discloses amine-based froth flotation collectors.

[0009] U.S. Published Patent Application No. 2014/0144290 discloses a method of froth floatation incorporating collectors comprising amidoamines and etheramines. U.S. Published Patent Application No. 2016/0114337 discloses polyamidoamine cationic collectors. Finally U.S. Patent No. 9,457,357 teaches a process for beneficiation of an iron-containing ore via an amidoamine comprising a reaction product of tall oil fatty acid and polyamine, while WO 2016/065189 discloses a composition for froth flotation utilizing an organic acid and a polyamidoamine.

[0010] In addition to the collectors and processes disclosed above, it is known in the art that alkyl xanthates (used individually or in conjunction with collectors such as those disclosed above) are among the most widely used collectors in froth flotation processes. However, alkyl xanthates, along with the collectors disclosed in the above prior art, provide poor recovery of oxidized ores from a traditional flotation process, due to their low affinity to oxidized metals. What is needed is a class of collectors with higher affinity and selectivity, especially to oxidized metal ores, to enhance metal recovery in the flotation process.

SUMMARY OF THE INVENTION

[0011] A collector formulation for froth flotation is disclosed. The collector can be made by a condensation reaction of tall oil fatty acids with polyamines such as triethylenetetramine (TETA) or tetraethylenepentamine (TEPA). The resulting product of the reaction comprises a mixture of amidoamine and imidazoline products that display superior copper recovery and a strong chelation capacity to copper via the amide/imidazoline group, with the hydrophobic carbon chain having an affinity to the air bubbles.

[0012] Froth flotation testing determined that the products, when utilized as a secondary collector in connection with a primary collector such as alkyl xanthate, provide a synergistic effect and increase total copper recovery by up to 13%.

BRIEF DESCRIPTION OF THE FIGURES

[0013] FIG. 1 depicts a collector reaction from the condensation of oleic acid and TETA.

[0014] FIG. 2 depicts a ¹³ C NMR characterization of collector-A.

[0015] FIG. 3 depicts an expanded ¹³ C NMR of collector-A.

[0016] FIG. 4 depicts 1H NMR (x axial) and ¹³ C NMR (y axial chemical shift predictions).

[0017] FIG. 5 depicts 2D lH- ¹³ C HMBC of collector-A.

[0018] FIG. 6 depicts a ¹³ C NMR characterization of a series of collector-B.

[0019] FIG. 7 depicts an expanded ¹³ C NMR of a series of collector-B.

[0020] FIG. 8 depicts a ¹³ C NMR characterization of collector-C-l and collector-C-2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention discloses a method for extraction from an ore comprising the steps of contacting a liquid suspension or slurry comprising one or more particulates with a collector to produce a treated mixture. The collector comprises one or more first components having the chemical formula:

and one or more second components having the chemical formula:

wherein R is C ₁₀ -C ₃₀ and is either a branched or linear, saturated or unsaturated alkyl chain; and wherein said first component comprises one amidoamine functionality and one imidazoline functionality, and said second component comprises two imidazoline functionalities.

[0022] The collector may further include one or more third components having the formula: wherein R is C ₁₀ -C ₃₀ and is either a branched or linear, saturated or unsaturated alkyl chain; and wherein said third component comprises two amidoamine functionalities. The collector is synthesized by reacting one or more tall oil fatty acids with one or more polyamines.

Tall Oil Fatty Acids

[0023] "Tall oil fatty acids” ("TOFAs)” encompass compositions which include not only fatty acids, but also rosin acids and/or unsaponifiables. TOFAs are generally produced as a distillation fraction of crude tall oil, which is obtained as a by-product of the Kraft process of wood pulp manufacture when pulping mainly coniferous trees. Tall oil, prior to refining, is normally a mixture of rosin acids, fatty acids, sterols, high-molecular weight alcohols, and other alkyl chain materials. Distillation of crude tall oil is often used to recover a mixture of fatty acids in the C ₁₆ -C ₂₄ range. [0024] Commercially available tall oil products such as XTOL® 100, XTOL® 300, and XTOL® 304 (all from Georgia-Pacific Chemicals LLC, Atlanta, Ga.), for example, all contain saturated and unsaturated fatty acids in the C16-C24 range, as well as minor amounts of rosin acids, and mixtures thereof. Representative fatty acids include oleic acid, lauric acid, linoleic acid, linolenic acid, palmitic acid, stearic acid, ricinoleic acid, myristic acid, arachidic acid, behenic acid and mixtures thereof.

[0025] In tall oil chemistry the actual distribution of the constituents in crude tall oil depends on a variety of factors, such as the particular coniferous species of the wood being processed (wood type), the geographical location of the wood source, the age of the wood, the particular season that the wood is harvested, and others. Thus, depending on the particular source, crude tall oil can contain from about 20 wt. % to about 75 wt. % fatty acids (more often about 30 wt. % to about 60 wt. %), from about 20 wt. % to about 65 wt. % rosin acids, and about 1 wt. % to about 40 wt. % neutral and non-saponifiable components.

[0026] For example, crude tall oil can have a fatty acids concentration of about 30 wt. % to about 60 wt. %, a rosin acids concentration of about 30 wt. % to about 60 wt. %, and a non- saponifiables concentration of about 5 wt. % to about 40 wt. %. Crude tall oil can also include at least 5 wt. %, at least 8 wt. %, or at least 10 wt. % neutral and non-saponifiable components. Fatty acid triglycerides can be present in an amount of less than 10 wt. %, less than 5 wt. %, or less than 1 wt. %, based on the total weight of the collector. The preferred molecular weight for a TOFA for use in the present invention is between approximately 150 g/mol to approximately 350 g/mol.

Polyamines

[0027] Polyamines are organic compounds having two or more amino groups. Polyamines are desirable chelating agents, as they are useful for dissolving metal ions in organic solvents. It was determined that preferred polyamines include carbon chains between the nitrogen groups of 2, 3, or 4 carbons. Triethylene- and tetraethylene- polyamines are examples of suitable polyamines. The amine groups of the polyamine are preferably primary amines. Illustrative polyamines include triethylenetetramine (TETA) and tetraethylenepentamine (TEPA), pentaethylenehexamine, hexaethyleneheptamine and mixtures thereof. Commercial TETA is a mixture of four amine isomers with close boiling points including linear, branched and two cyclic molecules. The major component is L-TETA (N,N’-bis(2-aminoethyl)-l,2- ethanediamine) at approximately 67 wt. % in the mixture; the remaining 33% are branched and cyclic amines, such as DAEP (N,N’-bis-(2-aminoethyl)piperazine); PEEDA (N[(2-aminoethyl)2- aminoethyl]piperazine); and TAEA (tris-(2-aminoethyl)amine). For the present invention, the preferred molecular weight for a TOFA is between approximately 100 g/mol to approximately 200 g/mol.

Collector Synthesis

[0028] The claimed froth flotation collector can be synthesized via a condensation reaction of TOFAs and polyamines, resulting in in a mixture of amidoamine and imdiazoline products. An example synthesis reaction is depicted in FIG. 1.

[0029] As the reaction in FIG. 1 shows, the products of the reaction may comprise amidoamine and imdiazoline products, hereinafter "chemical x," "component y," and "component z." The generic chemical formulas for these components are as follows:

Component X Component Y Component Z wherein R is C ₁₀ -C ₃₀ and is either a branched or linear, saturated or unsaturated alkyl chain.

[0030] As disclosed above, component X has two amidoamine functionalities, component Y has both one amidoamine functionality and one imidazoline functionality, and component Z has two imidazoline functionalities. The froth flotation collector comprising component X, component Y, and component Z preferably comprises 1 mol% to 99 mol% amidoamine functionality and a corresponding 99 mol% to 1 mol% imidazoline functionality, more preferably 25-75% amidoamine functionality and a corresponding 75%-25% imidazoline functionality.

[0031] Alternatively, the constituents of the synthesis reaction can be selected such that the resulting froth flotation collector further includes only component Y and component Z. The froth flotation collector comprising component Y and component Z preferably comprises 1 mol% to 99 mol% amidoamine functionality and a corresponding 99 mol% to 1 mol % imidazoline functionality, more preferably 25% to 75% amidoamine functionality and a corresponding 75% to 25% imidazoline functionality, and most preferably 25% to 50% amidoamine functionality and a corresponding 75% to 50% imidazoline functionality.

[0032] The collector is preferably synthesized at temperatures ranging between approximately l35°C to approximately 200°C for a time ranging between approximately one hour to thirteen hours, and pressures ranging between 2.0 psi to atmospheric pressure.

Working Examples

[0033] The following examples illustrate various representative attributes of the invention but should in no way be construed as limiting.

Preparation and Characterization of Froth Flotation Collectors

Collector-A formulation

[0034] A mixture of oleic acid (90% technical grade; Sigma- Aldrich; 500 mmol, 141.2 g), B(OH) ₃ (50 mmol, 3.09 g) and toluene (150 mL) was prepared in a 500 mL two-neck round- bottom flask. Commercial TETA (Dow Chemical Company; 250 mmol, 36.55 g) was slowly added to the mixture under nitrogen purge. After the TETA addition, a Dean-Stark apparatus was set up, and the reaction system was heated at l35°C for 6 hours while maintaining the nitrogen purge. The mixture was subsequently cooled to the room temperature. The organic solution was filtered to remove the B(OH) ₃ and collected in the round flask. The product was furthermore purified by vacuum distillation to achieve a mixture of products (collector-A; 151 g, 90% yield). FIG. 1 discloses the reaction equation for the synthesis of the collector-A compositions.

[0035] Carbon-l3 and two-dimensional Nuclear Magnetic Resonance Spectroscopy (" ¹³ C NMR" and "2D NMR") were applied to quantify and characterize the ratio of the compositions of collector-A products. FIGS. 2 and 3 disclose three sets of peaks from 166 ppm to 185 ppm which are all from quaternary carbons. The peak around 181 ppm was assigned to the carbonyl carbon of oleic acid, which matches the chemical shift of pure oleic acid. Chemical shift predictions (shown in FIG. 4) were prepared and found to be consistent with the raw ¹³ C NMR data. The set of peaks around 175 ppm was assigned to amide carbonyl carbons and the other set of peaks around 168 ppm was assigned to the quaternary carbon of imidazoline products. As shown in the shaded areas of FIG. 4, within four 1H-13C chemical bonds, the amide carbonyl carbon is only correlated with one 1H at 3.5 ppm. Meanwhile, the quaternary carbon from the cyclized product is coupled to 1H at 3.75 ppm, 3.6 ppm and 3.6 ppm, all within four 1H-13C chemical bonds. This 1H-13C coupling difference confirmed the peak assignments in FIG. 3.

[0036] 2D 1H-13C Heteronuclear multiple-bond correlation (HMBC) provided correlations between carbons and protons separated by 2-4 bonds and is disclosed in FIG. 5. The top horizontal dash line highlighted peaks of FIG. 5 indicate 1H-13C coupling between the quaternary carbon at 168 ppm and all other protons within 2-4 chemical bonds. This quaternary carbon at 168 ppm is coupled to protons at 3.4 ppm, 3.55 ppm, and 3.7 ppm, which indicates the presence of cyclized structure. The peak (highlighted by the middle of horizontal line) representing coupling of carbon at 175 ppm to proton at 3.3 ppm confirms that the 175 ppm peaks in one-dimensional ¹³ C NMR are from amide carbonyl carbon. By combining one dimensional ¹³ C NMR and two-dimensional 1H-13C HMBC, it was determined that that the amidoamine functionality of the collector is around 175 ppm and imidazoline functionality is around 168. By analyzing the peak integration at 175 ppm over the peak integration at 168 ppm the collector was determined to be mainly composed of amidoamine and imidazoline products.

Collector-B formulation

[0037] A mixture of oleic acid (47.23 mmol, 13.34 kg) and commercial TETA (23.62 mol, 3.45 kg) were mixed and agitated in a 5-gallon reactor. The reaction temperature was setup at l50°C under a nitrogen pad. After the reactor reached l50°C, 4 oz. samples were collected at 3 hours (collector-B@3h) and 4 hours (collector-B@4h). Once this was complete the nitrogen pad was discontinued and a vacuum was ramped to 2.0 psi and temperature was ramped to l80°C over the course of 2 hours. When the reaction reached l80°C and 2.0 psi, 4 oz. samples were again collected at 1 hour (collector-B@5h) and 2 hours (collector-B@6h). The reaction was then ramped to 200°C, and another 4 oz. sample was collected at 1 hour (collector-B@7h) and 2 hours (collector-B@8h). The mixture was subsequently cooled to room temperature. NMR was then used to characterize the ratio of collector B compositions. Full spectrum is shown in FIG. 6 and expanded spectrum at 160-190 ppm is shown in FIG 7. Collector C-l

[0038] A mixture of oleic acid (200 mmol, 56.5 g), triethylenetetramine hydrate (100 mmol, 16.43 g) and toluene (50 mL) was prepared in a 250 mL two-neck round-bottom flask. A Dean-Stark apparatus was set up under nitrogen pad, and the reaction system was heated at l35°C for 1 hour. The mixture was cooled to the room temperature. The product was furthermore purified by vacuum distillation to achieve a mixture of products (Collector-C-l; 65.9 g, 97% yield). NMR was used for characterizing the ratio of collector-C-l compositions, as shown in FIG. 8.

Collector C-2

[0039] A mixture of oleic acid (200 mmol, 56.5 g), triethylenetetramine hydrate (100 mmol, 16.43 g) and toluene (50 mL) was prepared in a 250 mL two-neck round-bottom flask. A Dean-Stark apparatus was set up under nitrogen pad. The reaction system was heated at l35°C for 13 hours. The mixture was cooled to the room temperature. The product was furthermore purified by the vacuum distillation to achieve a mixture of products (Collector-C-2; 60.2 g, 94% yield). NMR was used for characterizing the ratio of collector-C-2 compositions as shown in FIG. 8.

[0040] The NMR data detailing the molar ratio of amidoamine functionality to imidazoline functionality for samples Collector-A through Collector C-2 is set forth in Table I.

Table

[0041] As the above table shows, the various collectors have molar ratios of amidoamine functionality to imidazoline functionality ranging from 6:1 to 1:6.

Froth Flotation Test

[0042] Several batch flotation tests were performed to evaluate the effectiveness of the synthesized collector formulations in conjunction with copper oxide. First a copper ore sample was ground into powder capable of passing through a 100 mesh sieve. To assure a homogenous ore sample for the different flotation tests, the total ore sample was divided into smaller samples of 1.0 kg each via a rotary sampling machine. The samples were dissolved through acid digestion in a microwave digester from CEM Corporation, and copper concentration was analyzed by atomic adsorption in a Perkin Elmer Model Analyst 100. During flotation, pH was measured in a HANNA pH-meter. The conditions used in the trials are disclosed in Tables II, III, IV.

Table - Equipment Used in the Froth Flotation Tests

Table III - Reactants Used in the Froth Flotation tests

Table IV - Operational Parameters

[0043] Next, a collector formulation for copper oxide based on commercial TETA and oleic acid was prepared and synthesized pursuant to the method described for Collector A above, i.e. via a condensation reaction of 2 equiv. of oleic acid and 1 equiv. of commercial TETA, pursuant to the following equation:

Component X Component Y Component Z

[0044] A collector sample was then prepared by diluting Collector A in methyl isobutyl carbinol (MIBC), and a second sample was prepared by diluting Collector A in MIBC and mixing with sodium isopropyl xanthate. A pure sodium isopropyl xanthate sample was also prepared. The compositions of the samples are set forth in Table V.

Table V - Sample Preparation in the Flotation of Mixed Copper Core

[0045] All flotation tests were performed one time in the equipment previously described in Table II, and the operational conditions were kept constant as indicated in Table IV.

[0046] The results obtained for the flotation tests of mixed copper ore are shown in Table

VI.

Table VI - Metallurgical Results in the Flotation of Mixed Copper Ore

[0047] The above results show a clear and significant improvement in the flotation of soluble copper of the disclosed collector formulation compared to pure xanthate, increasing copper oxide recovery from 30 % to 65 % and total copper recovery from 46 % to 75 %, with a reduction in the total concentrate copper grade from 5.74 % to 2.71 %.

[0048] Further, as the data from Sample 3 shows, when only a collector formulation is used, the copper recovery increases as oxides are floated (believed due to the improvement of recovery of oxides), however copper concentrate grade drops to 2.71 %, indicating a decrease in copper selectivity. In contrast, the data for Sample 2 shows a synergistic effect when a collector formulation is mixed with xanthate, as total copper recovery increased from 46% (for sample 1, pure sodium isopropyl xanthate) to 81%, with a higher copper grade of 5.54%.

[0049] As such, it was determined that the Concentration A collector is an ideal secondary collector in combination with xanthate. To further investigate how the collector formulations can be applied as a secondary collector, an identical froth flotation test was conducted on 40 ppm samples of the various other collectors (i.e. collectors B@3h through C-2), in combination with 60 ppm of xanthate. Known collector AP-6493 (sodium hydroxamate-based product produced by Cytec), used in combination with known frother D-250, was also tested as a benchmark for comparison

[0050] The collector testing results were duplicated and the results were averaged. The average values obtained from the two experiments are summarized in Table VII below.

Table VII - Metallurgical Results in the Flotation Mixed

Copper Ore Using the Collector Formulations

[0051] As the above table shows, the benchmark combination of AP-6493 and D-250 resulted in average copper recovery of 62.5%. In contrast, all of the collectors tested (i.e. Collector B@3h through Collector C-2) demonstrated average copper recovery greater than 62.5%.

[0052] Finally, froth flotation testing was conducted to determine the efficacy of the collector in conjunction with frother D-250. AP-6493 was again used as a benchmark. Collector B@5h, which exhibited the greatest average copper recovery, was selected as the collector. The test results are set forth in Table VIII. Table VIII - Metallurgical Results: Flotation of Mixed

Copper Ores Using Collector B@5h with the Addition of D-250

[0053] As the above table shows, the use of Collector B@5h in conjunction with D-250 exhibited a total copper recovery that was approximately 13% higher than that of the AP- 6493/D-250 benchmark.

[0054] In summary, the flotation tests indicated that the collector formulations displayed higher performance when combined with xanthate by increasing the recovery of oxidized copper. This suggests that these formulation are well-suited as secondary collectors, as they provide synergistic benefits and exhibit superior performance when combined with primary collectors such as Xanthates, compared to benchmark secondary collectors.

[0055] Although the invention has been described by reference to its preferred embodiment as is disclosed in the specification and drawings above, many more embodiments of the invention are possible without departing from the invention. Thus, the scope of the invention should be limited only by the appended claims.