WO2025240484A1 - Methods and sytems of facilitating flotation using super-collectors - Google Patents

Abstract

Methods of facilitating bubble-particle interactions have been developed by increasing the particle contact angles to the levels that cannot be obtained using traditional flotation reagents. The novel collectors are designed to control the interfacial tensions using a group of specially designed hydrophobicity-enhancing reagents while maintaining negative wetting tensions. The contact angles measured on polished chalcopyrite specimens reached the level of super hydrophobic surfaces with contact angles in the range of 140°–170°. Laboratory-scale flotation tests conducted on a low-grade copper ore using the Super Collectors showed significant improvements in the recovery of both ultrafine and coarse particles by flotation.

Description

METHODS AND SYTEMS OF FACILITATING FLOTATION USING SUPER- COLLECTORS CROSS-REFERENCE [0001] The present application claims the benefit of U.S. Provisional Application Serial No. 63/646,374 filed on May 13, 2024, entitled Improving Flotation Using Novel Reagents, which is fully incorporated herein by reference. TECHNICAL FIELD [0002] The present disclosure is generally related to methods and systems for dispersion of agglomerates of hydrophobic particles, e.g. coal and hydrophobic minerals, in an aqueous slurry. BACKGROUND INFORMATION [0003] In 1905, Sulman and Picard were awarded U.S. Patent No. 793,808 for inventing a novel method of upgrading a finely pulverized ore using air bubbles to selectively collect target mineral particles and float out of an aqueous phase, leaving gangue mineral particles behind. For this process to work, small droplets of oil were used to render the target mineral particles, e.g., chalcopyrite, selectively hydrophobic to allow them to be attached to the air bubbles. The process, generally known as forced air flotation, is still generally regarded as the best available fine particle separation method and hence is widely used around the world. [0004] Flotation is a complex process involving three phases, i.e., solid, liquid, and air, and its efficiency is controlled by many different parameters. It may be fair to say, however, that particle hydrophobicity may be the most important parameter as it controls the bubble-particle attachment step. No flotation is possible without attachment, and the attachment step must be selective for upgrading. [0005] The free energy change (∆G) associated with the attachment step entails changes in interfacial changes as follows, ∆_{G = − +} [1] [0007] solid/liquid, and interfaces, respectively. Substituting the Young’s equation, _{γ SV} − _{γ SL} [0008] _cos θ = [2] [0009] [0010] < 0 [3] [0011] the contact angle, the higher the recovery. Also, the larger the difference in contact angles of the particles to be separated from each other, the higher the separation efficiency. [0012] In the mineral industry, a target mineral is rendered hydrophobic by coating the surface with collector molecules, with their polar head groups in contact with the surface and the nonpolar hydrocarbon tails (or hydrophobes) extended to the aqueous phase. In general, the higher the packing density of the hydrophobes on the surface, the higher the contact angles. On the other hand, collector adsorption does not often result in the formation of close-packed monolayers as the adsorption can be site-specific. As a means to improve the packing densities, several different types of reagents are inserted in between the adsorbed hydrocarbons to increase contact angles. These reagents known as hydrophobicity-enhancing agents include, but it not limited to, nonionic surfactants with HLB numbers of less than 15, naturally occurring lipids, modified lipids, and hydrophobic polymers (Yoon, U.S. Patent No. No. 6,799,682, incorporated fully herein by reference). Having no highly polar groups, they can readily adsorb in between the hydrocarbon chains adsorbed on the surface, squeezing out the water molecules in between and thereby increasing the contact angles. Most of these reagents are not water- soluble; therefore, they are used as solutions in organic solvents, e.g., light hydrocarbon oils, petroleum ethers, and distillates. Typically, one part by volume of an active ingredient is dissolved in 0.1 to 2 parts of a solvent before use. Some of the hydrophobicity-enhancing reagents that are sparingly soluble in water may be used without solvents. [0013] Various collectors are used in industry to render selected minerals hydrophobic. Wark and Cox (1934) found that galena (PbS) specimens from various mining districts of the world show contact angles in the narrow range of 60^o±2^o after the collector coating. Longer-chain collector molecules gave higher contact angles, but they were usually less than 90^o. The use of the hydrophobicity-enhancing reagents as disclosed by Yoon (US 6,799,682) can increase the contact angles slightly above 90^o. [0014] A flotation cell includes the pulp phase at the bottom and the froth phase at the top. In the former, the higher the contact angle, the higher the free energy of bubble-particle attachment as suggested by Eq. [3]. In the latter, the situation is more complex. In principle, fine particles act as “solid surfactants.” As θ increases, more of the particles would adsorb at the water/air interface and stabilize the froth. It has been reported that froth stability increases indeed with increasing contact angle. However, the stability begins to decrease at θ > 65-70^o (Ata, 2012; Park et al., 2018), while Aveyard et al. (1994) suggested that a foam should be most stable atθ = 90^o and decrease at higher contact angles. Since froth is an integral part of flotation, increasing contact angles too high could destabilize froth as will be discussed later in this present disclosure. [0015] In the present disclosure, novel methods and systems of increasing contact angles to the range of 140^o to 170^o have been developed. Hydrophobic surfaces with contact angles of ∼150^o are generally referred to as superhydrophobic surfaces. In this regard, the new reagents and their compositions disclosed in the instant invention are referred to herein as Super Collectors. BRIEF DESCRIPTION OF THE DRAWINGS [0016] These and other features and advantages will be better understood by reading the following detailed description, taken together with the drawings, wherein: [0017] Figure 1 shows one example of the changes in the interfacial tension at the pentane/water interface. [0018] Figure 2 shows one example of the mechanism by which heptane/water interfacial tensions are reduced. [0019] Figure 3 shows one example of the changes in contact angle with the changes in the composition of Super Collectors. [0020] Figure 4 shows one example of the changes in contact angles by changing the heptane/water interfacial tensions using cationic surfactants and polymers. [0021] Figure 5 shows one example of the effects of using Super Collectors for coarse particle flotation. [0022] Figure 6 shows one example of a Super Collector that improves the copper recovery from a cleaner-scavenger tail. [0023] Figure 7 shows one example of the effect of using Supe Collector for the copper recovery from a coarse ground rougher feed. [0024] Figure 8 compares the simulation results obtained using Super Collector and a conventional collector. [0025] Figure 9 shows the simulation results showing that a super-collector can improve the recovery of coarse composite particles. [0026] Figure 10 shows experimental results showing that Super Collector improves the flotation of coarse composite particles. [0027] Figure 11 compares the results obtained using Super Collector with those obtained using diesel as an extender. [0028] Figure 12 shows that Super Collector can greatly increase flotation throughout. DETAILED DESCRIPTION [0029] The present disclosure is generally related to methods and apparatus for separating a mixture of hydrophobic fine particulate materials suspended in water. In at least one example, the methods and apparatus improve bubble-particle interactions by increasing the particle contact angles to levels that cannot be obtained using traditional flotation reagents using novel collectors. The novel collectors are designed to control the interfacial tensions using a group of hydrophobicity-enhancing reagents while maintaining negative wetting tensions. The contact angles measured on polished chalcopyrite specimens reached the level of super hydrophobic surfaces with contact angles in the range of 140^o–170^o. Laboratory-scale flotation tests conducted on a low-grade copper ore using the novel collectors showed significant improvements in the recovery of both ultrafine and coarse particles by flotation. [0030] Flotation is generally regarded as one of the most significant separation processes invented during the 20^th Century for the metallurgical industry. Since it is a physical separation process, its cost is low. Therefore, flotation is widely used to produce preconcentrates to reduce the volume of materials to be used in the downstream process using chemical and/or thermal processes that are more energy intensive. In this regard, flotation has been an integral part of producing practically all metals used by humans. [0031] In flotation, air bubbles are used to selectively collect hydrophobic particulate materials from an aqueous phase, leaving hydrophilic materials behind. In effect, flotation is a hydrophobic-hydrophilic separation, in which separation process is controlled by controlling particle hydrophobicity. The best measure of hydrophobicity is contact angle (θ ), which varies with the surface free energies at the solid/liquid, solid/vapor, and liquid /vapor interfaces. The interfacial free energies (or tensions) given in units of J/m² (or N/m) can be controlled using appropriate surfactants. Of the various reagents used in the flotation industry, collectors are designed to increase θ of a target mineral, e.g., chalcopyrite, of an ore so that it can be recovered on the surface of air bubbles. In this regard, collectors are the most critical reagents in flotation. [0032] Various collectors are used to recover different minerals. For sulfide minerals, thiol- type collectors are used. For the flotation of oxide minerals, e.g., quartz, iron oxides, etc., various cationic and anionic surfactants may be used. In general, collector-coated minerals exhibit contact angles of less than 90^o. It has been shown by Yoon (U.S. Patent Nos.6,799,682 and 10,144,012, both of which are fully incorporated herein by reference) that using a non- ionic surfactant with HLB numbers of less than 15 can be used to increase θ a little above 90^o (US6,799,682; US10,144,012). If a low HLB surfactant or a hydrophobic polymer has a low water solubility, it may be used after dissolving it in an organic solvent, e.g., short-chain hydrocarbon oils, to increase its dispersibility in aqueous media. While non-exhaustive, the short-chain hydrocarbon oil may include at least one of n-alkanes with carbon numbers in the range of 4 to 16, mixed hydrocarbon oils such as kerosene and diesel, aromatic hydrocarbon oils, and long-chain alcohols. [0033] In the present disclosure, small amounts of surfactants are added to decrease the solvent/water interfacial tensions to substantially increase the contact angles to the level of super hydrophobic surfaces. In at least some examples, the reagent package accounts for 10 to 40% of primary collector, e.g., the reagent package accounts for 10 to 40% mol/L of primary collector. Thus, the role of the Super Collectors disclosed herewith is to further increase the contact angles of a target mineral well above the level achievable by using primary collectors alone. Here the term primary collectors are intended to refer to those that are designed to render a specific type of minerals hydrophobic. For example, xanthate is used as primary collectors to render sulfide minerals hydrophobic. In at least some examples, the primary hydrophobizing agent or collectors may include, but is not limited to, at least one of thiol-type collectors or dithiocarbamates. For example, the primary hydrophobizing agent or collectors may include, but is not limited to, at least one of thiol-type collectors or dithiocarbamates for separating sulfide minerals from silicious gangue minerals. The primary collectors may also include, but is not limited to, at least one of cationic, anionic, or fatty acid surfactants. For example, the primary collectors may include, but is not limited to, at least one of cationic, anionic, or fatty acid surfactants for the flotation of nonmetallic minerals. [0034] In the present disclosure, a small amount of surfactant is added to reduce the interfacial tensions at the solvent/water interface to increase contact angles to the range of 140^o to 170^o. If the contact angle of a target mineral is above 90^o in the absence of a solvent, the surfactant may be used to reduce the interfacial tensions at the water/vapor interface. This approach, which is born out of the Young’s equation given as Eq. [2], can improve both the recovery and selectivity of the flotation process. The Super Collectors developed in the present disclosure is particularly useful for the flotation of coarse composite particles without the problems associated with froth destabilization. [0035] As an air bubble approaches a flat mineral surface, the former deforms to form a thin liquid film (TLF), also known as wetting film, in between. The film thins initially due to the capillary pressure (p_c) due to the changes in bubble curvature. As the film thickness (h) reaches ~250 nm, the film thinning is controlled by the disjoining pressure (Π), [_{0036] Π = Πd (h ) + Π e ( h ) + Π h ( h )} [4] [0037] in which _{Πd, Πe,} and _Πh represent the disjoining pressures due to the van der-Waals (vdW), electrical double-layer (EDL), and hydrophobic forces (HP), respectively. Thus, film thinning is driven by [_{0038] p = p c − Π} [5] [0039] in which p is the hydrodynamic pressure that drives the film thinning step. In Eq. [4], _Πd and _Πe are usually repulsive (or positive) while _Πh is attractive. It will, therefore, be necessary to create a strong hydrophobic force to increase the kinetics of film thinning and hence expedite the kinetics of bubble-particle attachment. [0040] The kinetic of bubble-particle interaction in the pulp phase of a flotation cell may be represented as a second-order reaction, dN 1 [0041] _{= − kp N 1 N} dt ₂ [6] [0042] in which N1 and N2 are the number densities of particles 1 and bubbles 2, respectively, and _kp is the rate constant (Gupta and Yoon, 2024), ^ _{( E1 + E h ) − W a ^} [7] [0044] in which_Z * 1_{2 represents the corrected bubble-particle collision frequency under} turbulent conditions, while the exponential term represents the probability of particles attaching to air bubbles and leaving the pulp phase without being detached. [0045] In Eq. [7], which is in the same form as the Arrhenius equation, E1 is the energy barrier due to the surface forces, Eh the hydrodynamic resistance to film thinning, and W_a is the work of bubble-particle attachment, and E_k is the kinetic energy due to the microturbulence in the pulp phase. One can readily E_h using the Reynold’s equation, while the work of attachment can be predicted from θ, γ_LV, and particle size. [0046] From Eqs. [3] and [4], one the following relation, ∆ G _{= γ 23 ( cos − 1 )} h 0 [0047] = ⁻^ _[ ^Π _{d ( h )} ^{+ Π} _{e ( h )} ^{+ Π} _{h ( h ) ] dh} [8] [0048] from the values of θ, ς-potentials, and the Hamaker constants (A₁₃₂). Such information can be used to determine E₁. Recognizing that flotation processes are controlled by control of these surface chemistry parameters, E1 is perhaps the most critical kinetic parameter in flotation. Detailed analysis of Eq. [8] shows that Π < 0 at the contact angles obtainable using Super Collectors, which should in turn greatly increase the kinetics of film thinning and thereby increase flotation recovery and selectivity. [0049] As bubble-particle aggregates formed in the pulp phase enter the froth phase, less hydrophobic particles would drop off from bubble surface due to limited “parking area” for particles. Thus, froth phase recovery (R_f) should be a function of bubble coarsening in the as follows (Park et al., 2018), d 2, ₋ [9] [0051] ^ _{^ ^ ^} 0.5 n [0053] where d_2,b and d_2,t represent the bubble sizes at the base and top of a froth phase, respectively, n_f the number of faces of a bubble rupturing during coalescence, h_f the froth height, t_c is the critical rupture time of a lamella film varies with the contact angles of the particles in froth phase (Park et al., 2018). In Eq. [9], α is the rate at which particles drop off air bubbles and τ is the retention time of bubbles in a froth phase. [0054] One can determine the overall flotation rate constants (k) by combining Eq. [7] and [9] using the following relationship (Finch and Dobby, 1990), [_{0055] k = k p R f} [11] [0056] In at least one example, present disclosure can improve the efficiency of flotation separation on the various model equations discussed in the foregoing sections. Flotation is a hydrophobic-hydrophilic-separation, in which contact angle (θ ) is a thermodynamic parameter representing the hydrophobicity of the particles to be separated from each other. As Eq. [3] shows, ∆G of bubble-particle attachment step becomes more negative at higher contact angles, demonstrating its importance in flotation. [0057] Contact angles also play a critical role in flotation kinetics in that the higher the θ, the stronger the attractive hydrophobic disjoining pressure (Π_h < 0) that can counterbalance the repulsive van der Waals (Πd > 0) and electrical (Πe > 0) disjoining pressures and, thereby, reduce E1 for bubble-particle interactions. As shown by Eqs. [7] and [11], the overall flotation rate constant (k) should increase with decreasing E₁, which should in turn give rise to higher flotation rates, recoveries, and selectivity. [0058] According to Young’s equation (Eq. [2]), one can readily render a target mineral hydrophobic with _θ close to 90^o by coating the surface with a primary collector alone. In this case, the role of collector is to decrease γ_SV and/or increase γ_SL. If γ_SV > γ_SL due to the adsorption of the collector at the solid/liquid interface, the target mineral becomes partially hydrophobic, i.e., θ < 90^o. [0059] It has been shown previously that the use of a low HLB surfactant (or a hydrophobic polymer) dissolved in a short-chain hydrocarbon oil in conjunction with a primary collector, then the contact angle becomes slightly larger than 90^o, i.e., θ > 90 (Yoon, US6,799,682; US 10,144,012). It has been discovered that the hydrocarbon oil used as a solvent forms a meniscus near the three-phase contact line as shown in Figure 1. In this case, a contact angle is measured through the oil-water-air phase. In effect, the contact angle is for the oil-coated bubble rather than for solid. Under this condition, one should use the Young’s equation of the following form, c_os θ = _{γ SO} − _{γ SW} [0061] the wetting tension is always negative, i.e., (γ_SO - γ_SW) < 0, for hydrocarbon oils. Under this condition, one can increase the magnitude of cosθ by decreasing γ_OW and, thereby, increase θ well above 90^o. It has been discovered in the present disclosure that the contact angles of chalcopyrite (CuFeS2) can be increased to the level of super hydrophobic materials, e.g., PTFE (polytetrafluoroethylene), better known by its brand name Teflon ^TM. [0062] In the at least one example of the present disclosure, a small amount of a surfactant (e.g., butanol) is added to the short-chain hydrophobic oil (e.g., heptane, diesel, etc.) that was used as solvent for the low-HLB surfactant and hydrophobic polymer to increase θ of chalcopyrite to the range of 140^o -170^o. Table 1 shows the contact angle data obtained in this manner on a polished chalcopyrite surface. The surface was first treated using potassium amyl xanthate (KAX) as a primary collector and then by adding a low-HLB surfactant to increase θ above 90^o and subsequently adding butanol as a surfactant to decrease γ_OW. Three different low HLB surfactants were used as hydrophobicity-enhancing agents, which included Span 80, Span 40, and Brij 30. As shown, KAX alone gave _θ = 67^o, which was increased to 110.9^o using diesel oil as extender. By adding a small amount of butanol, the contact angles increased to >150^o. In these experiments, the concentrations of KAX and butanol were kept constant at 6x10^-5 moles/L. The conditioning time employed for the KAX treatment was 20 min. [0063] Note here that diesel alone gave a value of _θ = 110.9^o without using a low-HLB surfactant to meet the condition of γ_SO - γ_SW < 0 or θ > 90^o. It happened that the chalcopyrite sample used in the measurement exceptionally well to diesel, as θ was increased from 67^o to 110.9^o. For this reason, diesel is widely used as an extender in the flotation industry. Note here also that diesel works substantially better as extender in the presence of butanol to decrease γ_LV. [0064] Table 1 Primary Low HLB Butanol Contact S_urfacta ^Solvent o Collector* _nts (moles/L) Angle ( ⁾ KAX - - - 67.0 K^{AX - Diesel - 110.9 KAX - Diesel 6x10-5 157.7 KAX Span 80 Heptane} _6x10 ^{-5 154.8} KAX Span 40 Heptane _6x10-5 159.7 K^{AX Brij 30 Heptane} _6x10 ^{-5 172.2} *6x10^-5 moles/L [0065] Table 2 shows another set of contact angle measurements conducted using a hydrophobic polymer, polymethyl hydrosiloxane (PMHS), to meet the inequality of γ_SO - γ_SW < 0 that as discussed in the present disclosure. In this series of polished chalcopyrite surface was immersed in a 5x10^-5 M KAX solution for 20 min, followed by immersion in a 100 ppm PMHS-in-Heptane solution to obtain contact angle of 104.8^o. When the last step was carried out in the presence of butanol, the contact angle increased >160^o as shown. Note also that the higher the butanol concentration, the higher the contact angles became as Eq. [12] suggests. The results obtained using poly (2-ethyl hexyl) methacrylate (PEHMA), which is an insoluble hydrophobic polymer showed similar results as obtained by using PMHS.

[0066] Table 2 Primary Contact Hydrophob Butanol Contact C^ollector _{ic Polymer} ^Solvent o o Angle ( ) ^(moles/L) Angle ( ^{) KAX PMHS Heptane 104.8} _6x10 ^{-5 162.8 KAX PMHS Heptane 104.8} _2x10 ^{-3 165.9 KAX PMHS Heptane 104.8} _2x10 ^{-1 172.2} [0067] In general, oil drops can form larger contact angles on a given hydrophobic surface than air bubbles can. The reason is that Πd < 0 in the TLF of water confined between oil drops and a mineral surface, while Π_d > 0 in the TLF of water formed between an air bubble and a mineral surface (Huang and Yoon, 2019). See Eq. [8]. In this regard, the data presented in Tables 1 and 2 may be attributed to the presence of small amounts of oil used as solvent for the low-HLB surfactants and hydrophobic polymers. As has already been discussed, there are two other reasons: First, a hydrophobicity-enhancing agent is used to create a condition of _γSO ^_ _γSW ^< 0. Second, small amounts of surfactants are added to decrease the interfacial tensions γ_OW of the oil/water interface and thereby further increase the contact angles in Eq. [12]. Figure 2 shows the effect of butanol on the changes in _γOW. [0068] In the present disclosure, contact angles are measured at the menisci of the hydrophobic solvent (e.g., short-chain hydrocarbon oils) forming at the three-phase contact lines, as shown in Figure 1. In effect, contact angles are measured practically on the surface of the hydrocarbon oils coating air bubbles, which is the reason that the contact angles are so much higher than measured with air bubbles alone. The role of the surfactant is to allow oil coatings to be possible. Thermodynamically, oil can coat an air bubble in water under the following condition, [0069] ∆_{G = γ OA + γ OW − γ WA [0070] in which∆ G is the free energy change associated with the oil coating, γ OA is the surface tension of oil, γ OW is the interfacial tension at the oil/water interface, and γ WA is the surface tension of diesel oil, γ OA is in the range of 26-29 mN/m, OA is close to 44 mN/m. At a value γ WA = 68-72 ∆ G is close to zero or even positive. Thus, coating air} bubbles with diesel oil may not be thermodynamically favored in a flotation system. It would _{become easier in the presence of a surfactant, e.g., butanol, as γ OW is substantially reduced as shown in Figure 2 and thereby causing ∆G ^ 0.} [0071] Figure 3 shows the effects of the compositions of Supper Collectors on the contact angles of polished chalcopyrite samples as measured using the captive bubble method. As shown, the mineral surface treated with KAX alone gave a contact angle a little above 60^o. In the presence of KAX and polymethylhydrosiloxane (PMHS) and poly(2-ethylhexyl methacrylate) (PEHMA), the contact angles increased considerably above 90^o as described previously (Yoon, US6,799,682; US10,144,012). By adding diesel as is frequently practiced in industry, the contact angle actually decreased most probably due to the high surface tension of the oil. By replacing diesel with heptane, which has lower surface tension and hence more hydrophobic, and by adding butanol, contact angle was increased to >150^o. By replacing heptane with diesel and PMHS with PEHMA and still using butanol, contact angle decreased a little to slightly below 150^o. These changes can be readily explained using the changes in surface tensions of the reagent components involved. [0072] The result of the contact angle measurements presented hitherto were obtained using butanol as a surfactant to control γ_OW and synthesize Super-Collectors. There are many other reagents/ surfactants, however, that can also be used to do the same. These include, but are not limited to, one or more short-chain alcohols (such as, but not limited to, butanol and/or octanol), including aliphatic, cyclic, and aromatic alcohols that are commonly used as frothing agents in flotation. Also shown in the present disclosure is that one can use one or more of long-chain cationic surfactants (such as, but not limited to, DAH, CTAB, and/or CnTACl) or cationic polymers to synthesize Super Collectors that can greatly increase the kinetics of bubble-particle interaction and hence increase the throughput. In addition (or alternatively), the surfactant may include, but is not limited to, one or more of polyethylene or polypropylene glycols. By way of non-limiting examples, alcohol (such as, but not limited to, butanol and octanol) may be present in an amount of approximately 10^-(6) - 0.2 mol/L and cationic surfactants (such as, but not limited to, DAH, CTAB, and CnTACl) may be present in an amount of approximately 10^(-6) - 10^(-4) mol/L. In flotation, bubbles and particles are usually negatively charged, creating a positive disjoining pressure due to the electrical double-layer force (Π_e) which in turn contributes to increasing the energy barrier (E₁) and hence a slower flotation kinetics. This problem can be reversed by using a cationic surfactant and/or a cationic polymer to create a negative _Πe which should decrease _E1 and thereby increase the flotation kinetics. Still another advantage of using a cationic surfactant and/or a cationic polymer to reduce the disjoining pressure is that contact angles increase as Eq. [8] suggests and Figure 4 shows. [0073] Huang et al. (2018) developed a dewatering model and showed that fine particles can be more readily dewatered at higher contact angles. If the contact angle can be increased to >90^o the fine particles can dewater spontaneously due to the negative capillary pressure (p_c). Thus, Super Collectors may also be used as efficient dewatering aids. [0074] TEST PROCEDURE [0075] The Super Collectors synthesized as described in the foregoing section were tested in a series of laboratory-scale flotation tests. Samples were taken from operating plants and wet ground in a rod or attrition mill for size reduction and mineral liberation. The mill products were diluted with tap water to obtain desired solids contents for flotation tests. In each test, the performance of Super Collectors was compared with that of potassium amyl xanthate (KAX), which was chosen as a primary collector. A Denver laboratory flotation machine with a 1 or 2 L flotation cell was used in all separations tests using methyl isobutyl carbinol (MIBC) or polypropylene glycol (PPG)-425 as frothers. [0076] The performance of Super Collectors was also compared with that of KAX by simulating a full-scale rougher flotation bank in a manner described previously (Gupta et al., 2024). The major input parameters for the simulation were contact angles (θ ) and mineral liberation data. The latter information was provided by the company. [0077] EXAMPLES [0078] Example 1 [0079] A sample was taken from the feed to a copper rougher flotation bank, in which a low- grade porphyry copper ore was being processed at the 80% passing size (d80) of 220 µm. As is usually the case, copper recovery was low at particle sizes >150 µm due mainly to the sharp decrease in liberation at this particle size (Clark et al.2006). A possible solution to this problem may be to use a stronger collector or increase the reagent dosage to increase the contact angles of the poorly liberated composite particles. This approach was tested by isolating a coarse fraction (-600+212 µm) from the rougher feed sample by screening and subjecting the sample to two sets of flotation tests by changing the compositions of the Super Collectors at two different levels of the primary collector, potassium amyl xanthate (KAX) using a 1-L Denver laboratory flotation cell. The coarse fraction assayed 0.135 %Cu. [0080] In one set of tests, the coarse fraction was floated with 0.2 lb/ton KAX as the primary collector. In another, the flotation tests were conducted with 1.1 lb/t KAX as the primary collector. In each set, three different tests were performed: i) KAX alone, ii) KAX plus PHEMA-in-diesel, and iii) KAX plus PHEMA/butanol-in-heptane. The results presented in Figure 5 show that the third option gave the best results, which may be attributed to the use of butanol to decrease the contact angles by decreasing the oil/water interfacial tensions (γ₂₃). Note here that the use of hydrophobic polymers as disclosed previously (Yoon, US6,799,682; US 10,144,012); however, the improvement brought out by reducing the interfacial tensions also helped. [0081] The results show also that the Super Collector compositions tested in this example performed better at higher KAX dosages, indicating that the role of super collectors is to increase contact angles beyond what can be obtained using the primary collector and the hydrophobic polymers and thus act as one of promoters. It is interesting to note here that the results obtained at 1.1 lb/ton KAX produced substantially higher copper recoveries than those obtained at 0.2 lb/ton but at substantially lower copper grades, which can be attributed to the higher recoveries of coarse particles that are poorly liberated. At a given KAX dosage, however, the use of the Super Collector compositions improved both recoveries and grades. These results suggest that one can readily shift the grade vs. recovery curves by changing the composition of Super Collectors. [0082] Example 2 [0083] In a flotation circuit, the cleaner-scavenger tail (CST) is where the most difficult-to- recover materials congregate. These include ultrafine particles below 10-20 µm, poorly liberated ones despite their small particle sizes, and those that may be superficially oxidized while being recirculated without being recovered. It is common to send the CST back to the rougher flotation circuit as a circulating load (CL) so that they would have another opportunity to recover. In processing low-grade ores, CLs may account for 20-25% of the volumetric flows in rougher feeds. In this regard, the possibility of recovering copper directly from a CST was explored in a laboratory flotation test using a Super Collector. The laboratory test was conducted on a CST sample with a 0.14 %Cu grade and d₈₀ = 60 µm. Approximately 50% of the CST sample was finer than 28.7 µm. The flotation tests were carried out after grinding the sample in an attrition mill to d₈₀ = 10.7 µm to remove possible oxidation products and to improve liberation. The mill product was split into two samples with one used for a control test using 100 g/t KAX as a collector and another using 50 g/t of Super Collector (butanol in heptane) in addition to the KAX dosage used in the control test. [0084] The results presented in Figure 6 show that the use of the Super Collector in addition to KAX increased copper recovery from 26.9 to 44.1% and the product grade from 3.27 to 7.85 %Cu. These results suggest an open-circuit configuration, in which copper is recovered directly from CST in a separate flotation circuit while at the same time increasing the volumetric flowrate of freshly-mined copper ore by 20-25%. Financial benefits of the open- vs. close- circuit configurations have been discussed previously (Gupta et al.2023). [0085] Example 3 [0086] Copper ore samples assaying ~0.30%Cu were wet ground in a laboratory rod mill for 10 minutes to d80 = 280 µm and subjected to a standard laboratory flotation test using a 2-L Denver. The sample was subjected to coarse grinding on purpose to test the efficacy of using Super Collectors for coarse particle flotation. In a control test, the mill product was floated using 50 g/t KAX as collector and MIBC as frother. The total flotation time was 5 minutes while the froth products were collected at 1, 3, and 5 min. In another test, 20 g/t of a super collector (PMHS and butanol) was used in addition to 50 g/t KAX. [0087] The results presented in Figure 7 show that the use of the Super Collector significantly shifted the grade vs. recovery curve substantially to the right, demonstrating that the new reagent improved both recovery and grade. The recovery obtained after the 5-min flotation time was considerably higher (91.8%) than that (88.5%) obtained in the control test. The improved recovery was consistent with the decrease in the tails assay from 0.039 to 0.029 %Cu. That these improvements were made with a coarse ground sample is remarkable and shows that Super Collectors can significantly improve flotation performance by increasing the contact angles of composite particles. [0088] Example 4 [0089] Huang et al. (2022) developed a flotation model that can simulate flotation using the contact angles of particles to be recovered by flotation. The authors calculated the contact angles of composite particles from the liberation data of a flotation feed. The calculation was made using the Cassie-Baxter equation (1944) from the 2D areas of target mineral grains exposed on particle surfaces. Some of the model equations are given in this disclosure and discussed. A computer simulator based on the model can predict both the recoveries and grades for the first time from the liberation data of the copper-bearing mineral or a flotation feed. In this example, the simulator has been used to better understand the effects of using Super Collectors and compared the results with those obtained using KAX. [0090] The model was used to simulate a rougher flotation bank of an operating porphyry copper ore plant. Simulations were carried out to compare the performance of the rougher bank using a conventional collector, e.g., KAX, that can render the copper-bearing mineral hydrophobic with θ = 70^o, and a super collector that can do the same with θ = 150^o. Figure 8 shows the simulation results obtained with the -500+300 µm size fraction. As shown, the Super Collector gave substantially higher recoveries of the coarse particles, with the maximum gains observed at the mid-range surface liberations. At high surface liberations, even the KAX performed well. At the lower surface liberations, however, the gains in contact angle and hence the work of adhesion (W_a) are large enough to overcome the detrimental hydrodynamic impact. [0091] Figure 9 shows a set of two recovery vs. grade curves, one obtained using KAX and the other using Super Collector. It appears that KAX works well with particles with high surface liberations but not those with low surface liberations. The use of Super Collector, on the other hand, can substantially increase the contact angles of composite particles and hence give rise to substantially higher recoveries. The results obtained in the present disclosure suggest that the major difficulty associated with coarse particle flotation arises from low surface liberation, which can be addressed by using the Super Collectors developed in the present disclosure. The simulation results presented in Figure 9 show the same trend as those obtained in flotation tests shown in Figure 10. Note here that simulation and experimental results have been obtained on two different porphyry copper ore samples. [0092] Example 5 [0093] In the flotation industry, diesel oils are frequently used as “extenders,” meaning that the hydrocarbon oil can increase the contact angles beyond what can be achieved using a collector alone. The contact angle data shown in Table 1 are in support of the use of diesel as an extender. Nevertheless, the extent of contact angle increase is substantially less than the case of using a surfactant, e.g., butanol, which is one example of a Super Collector consistent with the present disclosure. [0094] The objective of this example is to show that Super Collectors can indeed outperform the extender in flotation experiments. In a control test, 20 g/ton KAX, 20 g/ton di-thiophosphate (DTP), and 20 g/ton diesel were used using 40 g/ton MIBC as frother. In another test, the 20 g/ton diesel was replaced by 20 g/ton Super Collector using 60 g/ton MIBC. The flotation products were conducted on a porphyry copper ore, while taking froth products at 0.5, 1.0, 2.0 and 8.0 minutes. The flotation results are given in Figure 11, in which the size-by-size tailings grades are plotted. As shown, Super Collectors gave substantially lower tails grade, or higher copper recoveries particularly at the 610 µm size fraction. [0095] Example 6 [0096] Although not shown numerically in this disclosure, the flotation rate constants (k) obtained using Super Collectors are approximately four times larger than those obtained using KAX at the optimal particle size range, i.e., 20-150 µm. The improved results obtained in the examples entail increased values of k. On the other hand, the increased recoveries observed in laboratory flotation experiments are less than anticipated on the basis of the increases in k values obtained by using Super Collectors, which may be attributed to the fact that the energy dissipation rates are 10 to 15-times higher than those (∼1 kW/m³) used in industrial flotation cells. Under this condition, conventional flotation collectors, e.g., KAX, can give high recoveries. Although Super Collectors produces superior results, the improvements were not as high as anticipated from the changes in k values. If the results obtained using KAX gave a 92% recovery, it would be difficult to obtain substantially higher recoveries for the particles that are in optimal particle size range. [0097] In full-scale flotation plants, operators compensate for the low-energy dissipation rate by allowing much longer retention times, e.g., 35-50 minutes. Under these conditions, it would be difficult to show the benefits of using Super Collectors, because recoveries are already high due to the long retention times. Under this condition, it may be better to aim for increased throughput. In this regard, a series of simulations have been conducted by increasing the throughput while maintaining the copper recoveries at 86.6% as is currently obtained using KAX in a closed-circuit configuration. The results presented in Figure 12 show that the use of a Super Collector that can give θ = 150^o for chalcopyrite grains. As shown, the throughput can be increased from 5,000 to 17,500 TPH. This finding is consistent with the generic understanding that stronger collectors can increase flotation rates, reduce flotation times, and increase throughput. [0098] While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.

Claims

What is claimed is: 1. A process of upgrading a mined ore comprising: pulverizing the mined ore to form pulverized materials including a target mineral particles; dispersing the pulverized materials in water to form an aqueous slurry; adding a primary collector, or hydrophobizing agent, to render the target mineral particles partially hydrophobic with contact angles with less than 90^o; adding a hydrophobicity enhancing reagent dispersed in a short-chain hydrocarbon oil to increase the contact angles above 90^o; adding a surfactant to lower the interfacial tension at an oil/water interface to further increase the contact angles to the level of superhydrophobic surfaces with contact angles in the range of 150^o to 170^o; adding small air bubbles to collect the target mineral particles on the surface and to rise out of the aqueous slurry to obtain a concentrate; and leaving gangue minerals behind in the aqueous slurry.

2. The process of claim 1, wherein the primary hydrophobizing agent or collectors include at least one of thiol-type collectors or dithiocarbamates.

3. The process of claim 1, wherein the primary hydrophobizing agent or collectors include at least one of thiol-type collectors or dithiocarbamates for separating sulfide minerals from silicious gangue minerals.

4. The process of claim 1, wherein the primary collectors include at least one of cationic, anionic, or fatty acid surfactants for the flotation of nonmetallic minerals.

5. The process of claim 1, wherein the hydrophobicity enhancing reagent includes at least one of hydrophobic polymers, nonionic surfactants whose HLB numbers are less than 15, naturally occurring lipids, modified lipids, or hydrocarbon oils.

6. The process of claim 1, wherein the short-chain hydrocarbon oil includes at least one of n-alkanes with carbon numbers in the range of 4 to 16, mixed hydrocarbon oils such as kerosene and diesel, aromatic hydrocarbon oils, and long-chain alcohols.

7. The process of claim 1 wherein the surfactant includes one or more of short-chain aliphatic alcohols, cyclic and aromatic alcohols, and polyethylene and polypropylene glycols.

8. The process of claim 7, wherein the surfactant is a cationic surfactant configured to increase contact angle by reducing the interfacial tension at the oil/water interface and configured to create an attractive electrical double-layer force between bubbles and mineral particles to increase the kinetics of flotation.

9. The process of claim 1, wherein the reagent package accounts for 10 to 40% of primary collector.

10. The process of claim 1, wherein the surfactant accounts for 10 to 40% of primary collector.

11. The process of claim 1, wherein the surfactant includes butanol.

12. A process of synthesizing Super Collectors that can increase the contact angle of a target mineral to a level comparable to those of superhydrophobic surfaces, the process comprising: a) Determining the flotation rate constants from the feed characteristics, b) Predicting the optimal grade vs. recovery curve using an Super Collector with an optimal reagent composition using a flotation simulator, c) Predicting the maximum throughput while maintaining the optimal grade vs. recovery curve, and d) Implementing the simulation result.

13. A process of increasing the rate of filtration of fine particles by increasing the contact angles of the particles well above 90^o and thereby creating a negative capillary pressure in filter cake.