Method of recovering and upgrading metals and minerals by flotation

Abstract

A method of recovering and upgrading a metallic component from a fluid mixture by flotation comprises the steps of introducing a lipopeptide surfactant and at least one supplementary flotation agent a

Description

FIELD OF THE INVENTION The invention relates to a method of recovering and upgrading metals and minerals by flotation. In particular, it relates to the use of an environmentally benign flotation agent for recovering metals. BACKGROUND TO THE INVENTION Sulphide minerals provide an extensive range of metals to the global economy and are the ore minerals of most metals used by industry, as for example antimony, bismuth, cobalt, copper, lead, nickel, zinc and precious metals. Sulphide mineral flotation is a critical separation process in the mineral industry for concentrating valuable elements from their gangue. Sulphide minerals can oxidise in the presence of air, forming sulphuric acids and resulting in acid mine drainage. Sulphide mineral flotation can serve as a mitigation strategy for acid mine drainage through removal of minerals such as pyrite. Froth flotation utilizes the characteristics of hydrophobicity, bubble stability and surface properties of minerals to induce flotation and separation of desired mineral particles from gangue particles. Some mineral surfaces are hydrophobic or have hydrophobicity imparted onto them via reagents, such as collectors. Additional hydrophobicity can also be imparted onto already hydrophobic minerals, such as non-polar minerals or sulphide minerals, to increase their floatability relative to minerals with similar surface properties to propagate separation between the minerals. Collectors are chemical compounds which attach to the surface of minerals. This reduces the stability of the hydrated layer separating the air bubble from the mineral, allowing the attachment of mineral particles to the air bubbles. Collectors may reduce induction time for bubble attachment, that is, they may further increase the hydrophobicity of the target mineral. Within a flotation cell a liquid / solid mixture or a suspension solution is aerated and agitated via impellers. The agitation results in the reduction of air bubble size and increased bubble density, which is further stabilized by frothing agents, also referred to as frothers, and the mixing of solid particles to allow them to collide with the air bubbles. The purpose of frothers is to increase the number of small air bubbles in the froth mixture. This in turn increases the surface area of air introduced into the flotation machine, which leads to a higher number of collisions of mineral particles with the bubbles. This improves the chances of the target particles being floated to the surface. The hydrophobic characteristic of the particles, either natural or induced, results in the preferred attachment to the air bubbles. The particles rise to the top of the flotation cell to be either mechanically removed via a scraping mechanism or via overflow mechanisms. Selective attachment is the most important mechanism regarding the separation and recovery of particles, but entrainment and entrapment also result in the recovery of particles to the concentrate. Water between air bubbles also flows into the concentrate due to the normal surface tension of water and its tendency to “stick” to itself. This results in particles within the water being “floated” as well and entering the concentrate, known as entrainment of particles within the water. Conventional flotation of sulphide minerals predominantly utilises fossil-fuel-derived synthetic reagents, such as xanthates, as the collector. Xanthates decompose into carbon disulphide (CS2), which poses health hazards and may create toxic conditions for aquatic life. In the field of ion flotation, heavy metal contaminated waters are a significant environmental hazard. The metals which might be recovered from these streams have significant intrinsic value if they can be collected and concentrated. With the growth of industrial sectors to cater for the continuously growing global population, there is a proportional growth in waste produced by industry. Heavy metals are a common contaminant in waste from mining, metal plating, fertilizer, paper, and dye industries, amongst many others. While heavy metals can be toxic and dangerous, some are rare metals and hold some economic value if they could be recovered. The valorisation of heavy metal contaminated waste could potentially encourage thorough treatment of wastewater from industries that may typically allow discharge of contaminated waste. Several conventional treatment methods are typically employed for treatment of heavy metals from aqueous waste streams. Chemical precipitation is a simple and cost-effective process, resulting in its frequent use in the current treatment of heavy metal contaminated wastewater. However, chemical precipitation requires long settling times, large areas, and produces large volumes of sludge that requires problematic downstream treatment. Alternative common processes include ion exchange, membrane filtration, and adsorption. These methods have shortcomings relating to high cost and energy requirements, secondary pollutant production, or limited efficiency with large volumes of dilute solutions, which limit their ease of implementation. The waste residues produced by these treatment methods are infrequently treated to recover metals and are typically subject to end of pipe treatment and disposed of in landfills by accredited waste handling companies. Flotation is a simple and low-cost process which has been shown to be an effective means of ion removal from aqueous solutions. Many flotation techniques are available, including ion flotation, precipitative flotation, sorptive flotation, dissolved air flotation, and foam fractionation. The method applied however, should be selected based on the quality of the up-stream solution, the target quality of the treated solution, and the chemistry of the solution. In cases of dilute concentration, precipitative flotation or sorptive flotation may be inefficient, and can also produce large volumes of toxic sludge. Ion flotation is effective at dilute concentrations and produces less sludge, while remaining simple and energy efficient. Collectors are used in flotation to alter the hydrodynamic properties of the material to be floated. In the case of ion flotation, oppositely charged collectors bind the desired metal ions (colligends) in solution and include them in a hydrophobic complex that adheres to the surface of bubbles in the liquid. In ion flotation, surfactants typically play the role of both collector and frother. The selection of an appropriate surfactant will depend on the chemistry of the solution, and the properties of the froth needed. The current state of the art uses synthetic surfactants such as sodium dodecyl sulphate (SDS) in ion flotation; however, there are environmental impacts associated with these chemicals as well. There is accordingly a need for environmentally benign, but still effective collectors and frothers to achieve ion flotation of metals. Biosurfactants are amphiphiles produced as secondary metabolites by a wide range of microorganisms. Interest has been generated around these molecules due to their biodegradability and their ability to be produced from renewable carbon sources. These properties provide clear benefits over the synthetic chemical surfactants often used in conventional industrial processes. Biosurfactants also show good stability and activity at extreme pH, temperature, and ionic strength. Oz Aksoy et al. (2022) disclosed the use of surfactin as a bio-collector in in the flotation of magnesite from magnesite ore (Oz Aksoy, D. et al., ‘Modelling of Magnesite Flotations with two different Collectors: Biocollector and Oleate’, J. ESOGU Engin. Arch. Fac., 30(1), pp.106-114, 2022). WO2019133554 disclosed compositions and methods for extracting minerals and metals from ore and mine tailings. The publication described bioleaching using a composition comprising biosurfactant-producing microorganisms or microbial growth by-products, including lipopeptide biosurfactants such as surfactin. There is a need for environmentally benign yet still effective collectors and frothing agents to achieve flotation of metals, both metal-bearing minerals and metal ions. The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application. SUMMARY OF THE INVENTION In accordance with an aspect of the invention there is provided a method of recovering and upgrading a metallic component from a fluid mixture by flotation, the method comprising the steps of: introducing a selected quantity of a lipopeptide surfactant into the fluid mixture; causing a gas to flow through the fluid mixture, thereby to float a froth fraction containing at least some of the lipopeptide surfactant and the metallic component; separating at least a portion of the froth fraction from a residual fraction of the fluid mixture; and separating the metallic component from said portion of the froth fraction. The method may include a step of introducing a selected quantity of at least one supplementary flotation agent into the fluid mixture. The supplementary flotation agent may be a synthetic frothing agent The supplementary flotation agent may be an alkyl polyglycol. The lipopeptide surfactant may be a biosurfactant. The biosurfactant may be surfactin. The lipopeptide surfactant may be introduced into the fluid mixture in a quantity sufficient to provide an initial concentration of the surfactant in the fluid mixture ranging from about 10 mg / L to about 20 mg / L, preferably from about 13 mg / L to about 17 mg / L, more preferably about 15 mg / L. The supplementary flotation agent may be introduced into the fluid mixture in a quantity sufficient to provide an initial concentration of the supplementary flotation agent in the fluid mixture ranging from about 5 pL / L to about 15 pL / L, preferably about 10 pL / L. The method may include a step of controlling or adjusting a pH value of the fluid mixture. The method may include controlling a pH value of the fluid mixture to below a natural or initial pH value of the fluid mixture. The method may include (i) lowering the pH value of the fluid mixture to below its initial pH value and (ii) introducing the lipopeptide surfactant in a quantity as described above (e.g., in a quantity sufficient to provide a concentration of about 15 mg / L). The method may also include (iii) introducing the supplementary flotation agent in a quantity as described above (e.g., in a quantity sufficient to provide a concentration of about 10 pL / L). The method may include a step of controlling or adjusting the pH of the fluid mixture to a level in a range from about 5 to about 9. The higher end of this range may be suitable for promoting separation performance in the case of fluid mixtures derived from fresh materials, while the lower end of the range may be suitable for promoting separation performance in the case of fluid mixtures derived from oxidised materials. In certain modes of performing the invention, the pH may be adjusted to a level in a range from about 6 to about 7, preferably from about 6.2 to about 6.6, more preferably about 6.4 (for oxidised materials). The metallic component may be in particulate form. It may be a metal mineral or a metalloid mineral. It may be a solid sulphide mineral. It may be a metal sulphide compound. The metal sulphide compound may be selected from the group consisting of copper sulphide compounds, nickel sulphide compounds, and any mixtures thereof. The fluid mixture may include a plurality of different metallic components. The method may accordingly be applied for recovering and upgrading a plurality of different metallic components from a fluid mixture containing them. The method may further be applied for selectively separating the different metallic components from the fluid mixture and from one another. The method may be applied to selectively separate different solid sulphide minerals contained in the same fluid mixture from one another by froth flotation. For example, the method may include selectively separating a copper sulphide compound and a nickel sulphide compound from a fluid mixture of both. The method may be applied to separate copper and nickel compounds from gangue, for example. The fluid mixture may contain a copper sulphide compound and a nickel sulphide compound, and the disclosed method may include a step of selectively separating those compounds from each other by (i) floating and recovering the copper sulphide compound from the separated portion of the froth fraction, and (ii) recovering the nickel sulphide compound from the residual fraction of the fluid mixture. For this aspect of the invention, the fluid mixture may have natural uncontrolled pH or an initial pH in a range from about 7.6 to about 8.0, optionally about 7.8. The invention also provides a process for preferentially collecting and floating a copper sulphide compound while depressing collection and flotation of a nickel sulphide compound in a fluid mixture, by performing the disclosed method. The copper sulphide compound may be chalcopyrite. The nickel sulphide compound may be pentlandite. The method may include a step of exposing the fluid mixture to oxidising conditions for a selected period of time prior to flotation (i.e., prior to causing the gas to flow through the fluid mixture). Oxidising conditions may be achieved by exposing the fluid mixture (and / or components thereof) to an oxygen-containing gas such as ambient air for a selected period of time. The time period for which the oxidising step is carried out may be selected to achieve or promote flotation of metal components, in particular particulate metal components, within the fluid mixture.The oxidising step may also be applied for controlling the pH of the fluid mixture. Without limiting the generality applications for the disclosed method and process, the fluid mixture may be a product of a mining process or an industrial process, or derivatives thereof. The fluid mixture may, for example, be a material selected from the group consisting of primary ore, run-of-the-mine (ROM), crushed ore, tailings, gangue, paste, and wastewater. Supplementary to or instead of solid metal or metalloid minerals, the fluid mixture may include a metallic component selected from the group consisting of metal ions, metalloid ions, and any mixtures of these ions. The fluid mixture may, for example, be a solution of such ions. The metal ions may be selected from the group consisting of Cu2+ ions, Ni2+ ions, Co2+ ions, and any mixtures of these ions. The solution may be an aqueous solution. The method may include a further step of precipitating ions from the froth fraction of the fluid mixture. The method may include a step of precipitating ions from the residual fraction of the fluid mixture. Embodiments and modes of the performing the method of the invention will now be described, by way of example only, with reference to the accompanying drawings. In the drawings: Figure 1 is a flow diagram illustrating a method of recovering and upgrading a metallic component from a fluid mixture by flotation; Figure 2 is a graph illustrating the effect of the concentration of a supplementary frother (Flotanol™ C-07) on rise factors of slurries containing varying surfactin concentrations at or above 30 mg / L; Figure 3 is a graph illustrating the effect of the concentration of the supplementary frother (Flotanol™ C-07) on deflation factors at various surfactin concentrations; Figure 4 is a graph illustrating the effect of surfactin concentration on mass recovery from a Merensky ore during flotation runs at a natural uncontrolled pH; Figure 5 is a graph illustrating the effect of surfactin concentration on mass recovery from the Merensky ore during flotation runs at a high uncontrolled pH via the addition of sodium carbonate; Figure 6 is a graph illustrating the effect of surfactin concentration on copper mineral grade and recovery from the Merensky ore during flotation runs at a natural uncontrolled pH; Figure 7 is a graph illustrating the effect of surfactin concentration on copper mineral grade and recovery from the Merensky ore at a natural constant pH; Figure 8 is a graph illustrating the effect of surfactin concentration on copper mineral grade and recovery from the Merensky ore at a lower uncontrolled pH due to oxidising; Figure 9 is a graph illustrating the effect of surfactin concentration on copper mineral grade and recovery from the Merensky ore at a high uncontrolled pH via the addition of sodium carbonate; Figure 10 is a graph illustrating the effect of surfactin concentration on nickel mineral grade and recovery from the Merensky ore during flotation runs at a natural uncontrolled pH; Figure 11 is a graph illustrating the effect of surfactin concentration on nickel mineral grade and recovery from the Merensky ore during flotation runs at a natural maintained pH; Figure 12 is a graph illustrating the effect of surfactin concentration on nickel mineral grade and recovery from the Merensky ore during flotation runs at a lower uncontrolled pH due to oxidising; Figure 13 is a graph illustrating the effect of surfactin concentration on nickel mineral grade and recovery from the Merensky ore during flotation runs at a high uncontrolled pH via the addition of sodium carbonate; Figure 14 is a graph illustrating the effect of collector concentration (Hostaflot™9033) on copper mineral grade and recovery from the Merensky ore during flotation runs at a natural uncontrolled pH; Figure 15 is a graph illustrating the effect of collector concentration (Hostaflot™9033) on nickel mineral grade and recovery from the Merensky ore during flotation runs at a natural uncontrolled pH; Figure 16 is a graph comparing copper grade and recovery of the highest performing surfactin concentrations (15 mg / L) for each of the respective pH condition groups and the Hostaflot™9033 run at a concentration of 120 mg / L; Figure 17 is a graph comparing nickel grade and recovery of the highest performing surfactin concentrations (15 mg / L) for each of the respective pH condition groups and the Hostaflot™9033 run at a concentration of 120 mg / L; Figure 18 is a graph illustrating the results of an experimental ion flotation run with surfactin for Cu2+, Ni2+ and Co2+ ions, with conditions of Qajr of 0.08 L / min, a pH level of 7 and an initial ion to surfactin ratio of 1:3, showing the extent of ion removal, the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation, and the concentration factor of ions into the overflowed foam fraction; Figure 19 is a graph showing the concentration of metal ions remaining in the residual solution over the duration of the flotation run described for Figure 18; Figure 20 is a set of graphs illustrating how changes in the air flowrate affect the extent of (i) Cu2+, (ii) Ni2+, and (iii) Co2+ ion removal from aqueous solution, the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation, and the concentration factor of metal ions into the foam overflowed fraction after ion flotation with surfactin; Figure 21 is a set of graphs illustrating the concentration of metal ions remaining in the residual solution during ion flotation with surfactin for a (i) Cu2+ solution, (ii) Ni2+ solution, and (iii) Co2+ solution, under the changing conditions of air flowrate described for Figure 20; Figure 22 is a set of graphs illustrating how changes in the pH level affect the extent of (i) Cu2+, (ii) Ni2+, and (iii) Co2+ ion removal from aqueous solution, the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation, and the concentration factor of metal ions into the foam overflow fraction after ion flotation with surfactin; Figure 23 is a set of graphs illustrating the species of (i) Cu (II), (ii) Ni (II), and (iii) Co (II) as a fraction of the total metal content, with speciation being illustrated as a function of solution pH; Figure 24 is a set of graphs illustrating how changes in the ratio of metal ions to surfactin affect the extent of (i) Cu2+, (ii) Ni2+, and (iii) Co2+ ion removal from aqueous solution, the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation, and the concentration factor of metal ions into the foam overflow fraction after ion flotation with surfactin; and Figure 25 is a graph illustrating the concentration of metal ions remaining in the residual solution during ion flotation of the solutions of metal ions described in respect of Figure 24, at both 1:3 and 1:10 molar ratio of metal ions to surfactin initially in solution. DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS Lipopeptide surfactants, such as the biosurfactant surfactin, can be used as flotation agents for separating, recovering and upgrading metal sulphide solids and precipitated metal complexes or ions. Surfactin, for example, has been found to be particularly effective as a collector and frothing agent for the flotation of particulate metal minerals (such as copper sulphide) and metal ions (such as Cu2*, Co2* and Ni2+) from slurries of particulate metal minerals and / or solutions of metal ions. Lipopeptide biosurfactants, also referred to as lipopeptides, are microbial surface-active compounds produced by a wide variety of bacteria, fungi, and yeast. Lipopeptides and lipoproteins are mainly obtained from bacteria of the Bacillus and Pseudomonas genera. Lipopeptides comprise a C12 to C18 fatty acid linked to a peptide chain of about four to twelve amino acids. Lipopeptides may have a linear hydrophilic head or a lactone ring if they are cyclic lipopeptides. Surfactins, iturins, fengycins, lichenysins, viscosins, amphisins and putisolvins are all examples of cyclic lipopeptides. Surfactin, iturin, and fengycin are produced by Bacillus subtilis. Surfactin is a lipopeptide biosurfactant comprising a cyclic peptide made up of a p-hydroxy fatty acid and up to seven amino acid residues. It has surface-active and antimicrobial properties. It has greater capacity for foaming and foam stability than SDS. It is a chelating biosurfactant, meaning that it has the ability to bind metals into metal-surfactin complexes. The carboxylic acid groups present on the hydrophilic heptapeptide moiety of the surfactin have a pKa of around 5.4 - 5.8, and are anionic at pH values greater than 5. The claw like structure formed by the carboxylate anions allows surfactin to bind metals in a precipitative reaction, producing stable complexes of the metal and surfactin. The cyclic peptide is the hydrophilic head group moiety of the amphiphilic surfactin molecule. The fatty acid tail is the hydrophobic moiety and can vary in chain length between twelve and seventeen carbons, but typically between fourteen and fifteen carbons. Improved separation of solid metal mineral particles from their gangue was achieved by flotation of the metal minerals with a select quantity of a lipopeptide biosurfactant, surfactin, and a select quantity of a synthetic flotation agent. The synthetic flotation agent may be an alcohol-based flotation agent. The flotation agent may be a polyglycol, an alkyl polyglycol, a poly(alkylene glycol), a polyglycol ether, or a poly(propylene glycol) ether. The flotation agent may be a poly(propylene glycol) monomethyl ether. Preferably, the flotation agent is the commercially available frothing reagent Flotanol™ C-07 (or C7) from Clariant Mining Solutions, Louisville, USA. Surfactin acts as both a selective collector of metal sulphides and as a flotation agent. The introduction of a supplementary flotation or frothing agent to the slurry, resulted in better frothing and thus improved recovery of the froth fraction that includes the metal sulphide particles in comparison to the introduction of surfactin alone. The metal sulphide particles float with the surfactin and supplementary flotation agent whilst the gangue minerals such as silicates and aluminates tend to settle. It was found that surfactin, in particular, displays selectivity towards copper sulphide minerals over nickel sulphide minerals. Accordingly, the methods described herein are useful for separating metal components, in particular metal minerals, from their gangue using flotation. The methods may be limited to the separation only, or may include a further step of recovering the metal components from a separated froth fraction following the flotation process. Figure 1 illustrates a mode of performing a method (100) of recovering and upgrading a metallic component from a fluid mixture by flotation. The fluid mixture may, for example, be a slurry or a solution of ions. The method involves introducing (101) a selected quantity of a lipopeptide surfactant into the fluid mixture and causing a gas to flow (102) through the fluid mixture, thereby to float a froth fraction containing at least some of the lipopeptide surfactant and the metallic component. A portion of the froth fraction is then separated (103) from a residual fraction of the fluid mixture and the metallic component is separated (104) from that portion of the froth fraction. For present purposes, the term “froth” is to be interpreted broadly and will include foam, for example, depending upon the particular type of flotation being carried out. The method includes a step of introducing a selected quantity of at least one supplementary flotation agent into the fluid mixture. It may be a frothing agent (“frother”) or collector. It may, for example, be an alkyl polyglycol based frother such as Flotanol™ C-07 (available from Clariant Mining Solutions, Louisville, USA). The supplementary flotation agent may be any similar commercially available synthetic compound. The supplementary flotation agent may be introduced into the fluid mixture before, after or together with the lipopeptide surfactant in a premixture form. Moreover, the introduction of the lipopeptide surfactant and the supplementary flotation agent may be performed before, after or at the same time as the gas is caused to flow through the fluid mixture. It will be appreciated that more than one supplementary flotation agent may be introduced into the fluid mixture, in addition to the lipopeptide surfactant. The lipopeptide surfactant may be a biosurfactant, such as surfactin, iturin and / or fengycin. Advantageously, the lipopeptide biosurfactant may be surfactin. The surfactin or other lipopeptide surfactant may be introduced into the fluid mixture in a quantity sufficient to provide an initial concentration of the surfactant in the fluid mixture ranging from about 10 mg / L to about 20 mg / L, optionally from about 13 mg / L to about 17 mg / L, optionally about 15 mg / L. The supplementary flotation agent may be introduced into the fluid mixture in a quantity sufficient to provide an initial concentration of the supplementary flotation agent in the fluid mixture ranging from about 5 pL / L to about 15 pL / L, optionally about 10 pUL Advantageously, the surfactin and the supplementary flotation agent may each be introduced into the fluid mixture in quantities sufficient to provide the following concentrations in the fluid mixture, respectively: • surfactin - approximately 15 mg / L; and • supplementary flotation agent - approximately 10 pL / L. The method may include a step of controlling a pH value of the fluid mixture (e.g., slurry). This step may comprise controlling the pH value to below a natural or initial pH value of the fluid mixture. Lower pH may typically correspond to oxidised material being floated. However, the floatability is still present at higher pH. This is important in certain settings and contexts. For example, in an industrial mining operation an alkaline condition may be preferred, and any recovery achieved without dropping pH is something to work with and can be advantageous. The method may include a step of adjusting the pH of the fluid mixture to a value in a range from about 5 to about 9, optionally from about 6 to about 7, optionally from about 6.2 to about 6.6, optionally about 6.4. The method may include (i) lowering the pH value of the fluid mixture and (ii) introducing the lipopeptide surfactant in a quantity as described above (e.g., in a quantity sufficient to provide a concentration of about 15 mg / L). The method may optionally also include (iii) introducing the supplementary flotation agent in a quantity as described above (e.g., in a quantity sufficient to provide a concentration of about 10 pL / L). Certain modes of performing the method may include a step of exposing the fluid mixture or one or more components thereof (e.g., mineral particles or gangue suspended in the fluid mixture) to oxidising conditions for a selected period of time before the flotation and separation steps are carried out. Typically, although not necessarily, no artificial oxidising conditions are used. The oxidising conditions may be obtained by exposing the fluid mixture (or the component before mixing or while suspended in the mixture) to an oxygen-containing gas such as ambient air. For example, the fluid mixture may be left exposed to the air. The oxidising step may be carried out prior to performing the flotation. The oxidising step may be carried out on particulate metal components of the fluid mixture before, after or while they are introduced into the fluid mixture. The oxidising step may be carried out for a period of time sufficient to achieve or promote flotation of particles within the fluid mixture. By way of example only, the oxidising period may range from 1-2 days. In one example of carrying out the oxidising step, mineral particles were left suspended in the fluid mixture for two days before the flotation was carried out. The oxidising step may cause surfaces of the particles to become oxidised. This in turn may promote increased interaction of the particle surfaces with the lipopeptide surfactant, e.g., surfactin. In some cases, the oxidising period may be sufficient to provide a copper recovery of 30% with a grade of 1.1%. Under certain conditions, the oxidising step may be instrumental in the step of controlling the pH of the fluid mixture. For example, the pH may be lowered by applying the oxidising step. The step of combining the frothing agent with the lipopeptide surfactant in the fluid mixture may establish a synergistic relationship between these two components, thereby to provide either or both of the following enhanced outcomes, when compared against corresponding outcomes achievable by just one or the other of the two components individually without the other: (i) more effective conditions of deflation, foam generation and overall bubble stability within the fluid mixture during flotation; and (ii) increased recovery of the metallic component from the mixture by flotation, that is, promotion of recovery. The metallic component may be in particulate form. It may be a metal mineral or a metalloid mineral. It may be a solid sulphide mineral. It may be a metal sulphide compound. The metal sulphide compound may be selected from the group consisting of copper sulphide compounds, nickel sulphide compounds, and any mixtures thereof. The copper sulphide compound may be chalcopyrite. The nickel sulphide compound may be pentlandite. The disclosed method can be applied for the selective separation of solid sulphide minerals from a fluid mixture using flotation, e.g., froth flotation. This method may involve selectively separating a copper sulphide compound (e.g., chalcopyrite) and a nickel sulphide compound (e.g., pentlandite) from a fluid mixture of both. The compounds can be selectively separated from each other by (i) floating and recovering the copper sulphide compound from the separated portion of the froth fraction, and (ii) recovering the nickel sulphide compound from the residual fraction of the fluid mixture. The invention can provide a process for preferentially collecting and floating copper sulphide compounds while depressing the collection and flotation of nickel sulphide compounds. The process may be carried out by performing the disclosed method to float and recover the copper sulphide compound. This process may be particularly suitable for the separation of chalcopyrite and pentlandite. For this aspect of the invention, the flotation may be performed at a natural uncontrolled or initial pH in a range from about 7.6 to about 8.0, optionally at an initial pH of about 7.8. Instead of the solid minerals, or in addition to them, the mixture may include a solution of ions. The metallic component of the fluid mixture may therefore include metal ions, metalloid ions, or any mixtures of these. The metal ions may be heavy metal ions, including any mixture of different heavy metal ions. The metal ions may be selected from the group consisting of copper ions, nickel ions, cobalt ions, and any mixtures thereof. The metal ions may be selected from the group consisting of Cu2+ ions, Ni2+ ions, Co2+ ions, and any mixtures thereof. The method may also be used to recover metalloid cations from solution such as arsenic, selenium or tellurium cations. A precipitation process may be used to supplement the disclosed ion flotation method. As described in United Kingdom patent application no. GB 2214049.5 filed by the present applicant, the precipitation process may employ at least one lipopeptide surfactant such as, but not limited to, surfactin. The presently disclosed method may accordingly include a further step of precipitating ions from the froth fraction of the mixture, or the residual fraction of the fluid mixture, or both. The precipitation step may, in each case, be performed with the aid of surfactin, using the method described in GB 2214049.5. For the recovery of metal ions by precipitation, the lipopeptide biosurfactant may be added in an equimolar or higher molar ratio of lipopeptide biosurfactant to metal ion. By way of example, the lipopeptide biosurfactant may be added in a molar ratio ranging from about 1:1 to about 3:1 of lipopeptide biosurfactant to metal ion. Optionally, the molar ratio may range from about 1:1 to about 2:1. Surfactin, for example, may be added to a heavy metal contaminated water at a concentration in a range from about 1:1 to about 2:1 of surfactin to heavy metal. The gas used to form the froth fraction may be air. Without limitation, the fluid mixture may be or be derived from primary ore, run-of-the-mine (ROM), crushed ore, and / or mining waste such as, but not limited to, tailings, gangue or paste. The fluid mixture may be a slurry. The fluid mixture may be wastewater from a mining process or other industrial process. Without committing to any particular mechanism for operation of surfactin in the disclosed method, the surfactin may act to change the hydrophobicity on the surface of sulphide mineral particles. Ionisation of the carboxylic groups of the surfactin may play a role in adsorption. Under certain conditions, surfactin may act as a frother to stabilise bubbles for froth flotation. FLOTATION OF METAL MINERALS In one mode of performing the disclosed method, surfactin may provide an alternative collector for sulphide mineral flotation. The frothing capabilities of surfactin at various concentrations were evaluated with the addition of Flotanol™ C-07, a commercially available frother from Clariant Mining Solutions, Louisville, USA. Method The froth flotation capabilities of surfactin were evaluated after determining optimal frothing concentrations. Surfactin at concentrations of 15, 30 and 50 mg / L, with the addition of 7.5 pL / L Flotanol™ C-07 as a frother, were tested within a 3-litre flotation cell with 1 kg samples of run-of-the mine (ROM) Merensky ore. The pH conditions were varied, as well as the effect of 2-day oxidising on the ore. Hostaflot™ 9033, a conventional collector from Clariant International Ltd, was also tested within the same flotation cell, to compare flotation performance with surfactin. Merensky ore contains the major mineral groups pyrrhotite, pentlandite and chalcopyrite. Metals generally aimed to be extracted are nickel, copper and platinum group metals (PGMs). The ROM used for the runs had an uneconomical or negligible quantity of PGMs remaining within the ore and low concentrations of nickel and copper. The minerals that were to be concentrated out of the ore were thus pentlandite and chalcopyrite, the nickel and copper containing minerals. Milling To ensure particles were appropriate sizes for flotation while maintaining constant size parameters, a milling curve was constructed to generate consistent and repeatable feed. Samples 1 kg each were milled in a 5-litre milling vessel in conjunction with 0.7 mL of water per gram of ore. Milling of separate ore feeds was executed for time periods of approximately 20 min, 40 min and 60 min respectively. After milling, the samples were dried within an oven at 80°C for 24 hours and dry sieved. A milling curve was generated which indicated that a milling time of 36 min and 40 seconds was appropriate to achieve a consistent 80% 75 micron undersize. Surfactin The surfactin powder used had a purity of 79%. Stock solutions for the adsorption tests were prepared at concentrations of 120 mg / L, 208 mg / L and 360 mg / L respectively. The concentration for the flotation stock solution was 7 500 mg / L. Froth attribute testing To determine the frothing qualities of surfactin compared to Flotanol™ C-07, a frothing column was utilized. The frothing column was loaded with 1 kg of milled feed and filled to the 3-litre mark with commercial water. Commercial water refers to water that has not been treated via distillation, reverse osmosis or any other chemically altered water. The column was then dosed with the surfactin or Flotanol™ C-07 depending on the specific run conditions. After dosage, agitation was initiated in the flotation cell and run for 5 minutes to condition. Rise tests were carried out. If the froth generated reached a goal height of 15 cm, the time it took was measured. If the height of 15 cm was not reached in 20 seconds or the froth stagnated at a specific point within the 20 second time frame, the time was noted and the height that the froth achieved was also noted. Immediately after each rise test had been completed, the aeration was turned off and a deflation section of the run was performed. The time taken for deflation to a 4 cm mark was noted. If the froth did not deflate to the 4 cm mark within a 60 second time frame, the deflation distance was measured. Froth flotation procedure The frothing capabilities of surfactin at various concentrations were assessed using surfactin both on its own and with the addition of Flotanol™ C-07. Surfactin exhibited frothing characteristics with limited bubble stability. It was able to generate froth on its own, but appeared to be limited in its capability to maintain froth stability without having the bubbles rapidly coalescing into larger bubbles, or without generating foam. The addition of small quantities of Flotanol™ C-07 was found to alleviate the bubble stability problem and to increase the frothing capabilities of surfactin significantly. The addition of a conventional frother may act synergistically with surfactin to provide the required bubble stability while simultaneously decreasing the mean bubble diameter. After concluding the frothing and adsorption tests, further tests were conducted to assess the effects of pH on surfactin collecting capabilities, the frothing capabilities of surfactin and any interaction surfactin may have with conventional frothers. Surfactin concentrations of 15 mg / L, 30 mg / L and 50 mg / L, respectively, were tested. The concentration of Flotanol™ C-07 was 7.5 pL / L for each run. A varying set of pH and solution conditions were tested, as follows: 1. Natural slurry pH with no implemented pH control - Initial pH of 9 declining to 7.5 after 20 minutes within the slurry. 2. Natural slurry pH with pH control aiming to maintain a constant pH - Initial pH of 9 maintained between 8.75 - 9.25 due to constant pH decline. 3. Lower pH with no implemented pH control - Initial pH of 7.8 after 2-day oxidising period for slurry in an open container which declined to 6.4. 4. Increased initial pH with no implemented pH control - Initial pH of 10 declining to 8.2 after 20 minutes within the slurry. Two repeats were also performed on the 30 mg / L surfactin for both the natural pH with and without control. Three runs with a commercial collector, Hostaflot™ 9033, were also performed with respective concentrations of 120 mg / L, 150 mg / L and 180 mg / L and with a Flotanol™ C-07 concentration of 40 pL / L. These runs were performed as comparison runs, to compare surfactin’s performance against a commercially available, conventional collector. To start each froth flotation run, the stock solutions for surfactin and frother were prepared and mixed into a single beaker. Eight oven-ready trays were readied with time interval markers for 0-1 min, 1-2 min, 2-4 min, 4-6 min, 6-8 min, 8- 3 min, 13-20 min and tailings (i.e., the remaining solids in the column after a float time). An additional container was used for any possible overflow during the conditioning period. The milled ore was loaded into the flotation cell and agitation was initiated. A calibrated pH probe was placed within the flotation cell and the cell was filled up to the 3-litre mark. The pH was noted, and pH buffers were added for specifically the increased pH condition and the pH-controlled condition. For those respective conditions buffers were added before conditioning to ensure the starting pH was correct. The surfactin-Flotanol™ C-07 mixture was added and the conditioning period of 5 minutes commenced. When the end of the conditioning period was reached, an aeration flow of 5.5 LPM was opened and a stopwatch was used to record the time. Every 15 seconds the froth was scraped off the top layer into the oven-ready tray. Water was intermittently added to the flotation cell to compensate for lost water into the concentrate. The liquid level was kept constant. When the run had reached 20 minutes, the aeration and agitation was switched off and the run was terminated. The concentrates were put into an oven at 80°C for 24 hours to dry. The tailings left within the flotation cell were filter-pressed into a filter cake, which was also placed into the oven and dried for 48 hours. This was repeated for every collector concentration and slurry condition. The dried samples were marked with identifiers and each sample was weighed. With this data, a mass pull and recovery curve for each run could be generated. After weighing, the samples were prepared for inductively coupled plasma (ICP) spectroscopy analysis. Feed samples were also sent for particle size distribution (PSD), X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis. Results of frothing tests Frothing tests were performed to generate data regarding the height that a specific reagent combination reached as well as the duration that it took the reagent combination to reach that height. The tests also generated data regarding the distance the reagent combination deflated from that height and the duration it took to deflate that distance. The data was noted as rise height (RH), rise time (RT), deflation height (DH) and deflation time (DT). By dividing the distance by the duration, a rise velocity (RV) and deflation velocity (DV) were generated. To gauge the performance of the reagent combinations, each combination was compared against a reference reagent combination. This reference combination was selected based on desired performance regarding the RV and DV and characteristics observed such as bubble size, coalescence and foam generation. The reference reagent combination was run with a surfactin concentration of 15 mg / L and a Flotanol™ C-07 concentration of 10 pL / L. To normalize the RVs and DVs, the generated velocity of each run was divided by the velocity of the reference run so that the results could be presented as dimensionless numbers noted as the rise factor (RF) and the deflation factor (DF). Figure 2 shows the effect of varying Flotanol™ C-07 concentrations on the rise factor (RF) of slurries containing varying surfactin concentrations at or above 30 mg / L. The graph contains all the rise factor (RF) data points for surfactin concentrations higher than 15 mg / L as well as the one data point which only used Flotanol™ C-07. No significant change to the rise factor (RF) was observed when adding additional Flotanol™ C-07 if the surfactin concentration was at 30 mg / L or above, that is, maximum frothing was reached at concentrations of 30 mg / L. This suggests that surfactin was able to induce frothing up to this concentration. Figure 3 shows the effect of Flotanol™ C-07 concentration on the deflation factor (DF) at various surfactin concentrations. Froth produced using surfactin alone lacked prolonged bubble stability, i.e., surfactin exhibited frothing capabilities but did not impart enough bubble stability on slurry solutions to serve as a frothing agent on its own (as the sole frother). However, surfactin was shown to interact in a complementary way with other industrial frothing agents such as Flotanol™ C-07, which provided the additional bubble stability required. An increased deflation factor (DF) indicates a higher deflation velocity (DV). As seen in the graph, deflation is highly sensitive to the presence of an additional reagent, such as Flotanol™ C-07, acting as a supplementary frother. The reagent concentration is also a sensitive variable with regards to foam generation and overall bubble stability. The results shown in Figure 3 provided upper limits due to foaming limitations. For all the tested surfactin concentrations, having a Flotanol™ C-07 concentration at or above 20 pL / L generated foam or bubbles that deflated too slowly. The most favourable reagent combination, based on the tests, was surfactin at 15 mg / L and Flotanol™ C-07 at 10 pL / L. However, if a Flotanol™ C-07 concentration of 10 pL / L had been used for the tests, it would have resulted in foaming for the other two concentrations of surfactin. Thus, 7.5 pL / L Flotanol™ C-07 was selected as the concentration to be used for the froth flotation runs. The results illustrate that surfactin may be advantageously used to supplement one or more conventional frothers such as Flotanol™ C-07. This may be advantageous insofar as surfactin is more environmentally friendly than certain conventional frothers, especially synthetic frothers, while being relatively inexpensive to manufacture. Flotation tests under varying pH conditions and surfactin concentrations Tests were run to assess the effect of varying pH conditions and surfactin concentrations on mass recovery, copper and nickel recovery, and copper and nickel grade and separation efficiencies between the gangue and minerals. Effect of surfactin concentration on mass recovery Figure 4 shows the effect of surfactin concentration on mass recovery at a natural uncontrolled pH (initial pH 7.8). It can be seen how an increase in collector concentration causes an increase in mass recovery, likely due to more particles adsorbing surfactin. (Note: The relative standard deviation was relatively high, at 4.8%.) An increase in surfactin past the CMC causes the formation of micelles in the solution. The measurement of CMC for surfactin varies depending on the type, method of production and purity but has been established as approximately 8-12 mg / L. The lowest operating concentration for the experimental tests conducted in the present study was 15 mg / L. With the addition of more surfactin, an increase in the collection power of the micelles was to be expected, with a decrease in selectivity. Increased froth generation rate and bubble stability may also have allowed more particles to overflow into the concentrate. Figure 5 shows the effect of surfactin concentration on mass recovery at a high uncontrolled pH via the addition of sodium carbonate. With an increased pH, ionization of the surfactin may cause increased frothing which may result in increased entrapment of surfactin micelles. This may explain the high mass recovery during the initial time periods, reaching a maximum for the 50 mg / L run. The difference between the 30 mg / L and 15 mg / L runs was small. This indicates that the surfactin concentration had a relatively limited effect on overall mass pull in this concentration range. The 50 mg / L run showed a significant jump, which may also be attributed to increased frothing and overflow of solids. Copper grade and recovery for various concentrations of surfactin Figure 6 shows the effect of surfactin concentration on copper grade and recovery at a natural uncontrolled pH (initial pH 9 declining to pH 7.8). The graph illustrates how the copper grade decreased with increased surfactin concentration. The copper grade within the feed was 0.0634 wt%, as determined via XRF analysis supported by ICP spectroscopy analysis. Surfactin flotation was able to increase the grade to 0.69 wt%, which is approximately 11 times higher than the feed copper grade, according to Error! Reference source not found.. The trade-off between grade versus recovery is observed. Increasing the surfactin concentration starting from 15 mg / L, the relative rate at which the grade decreases is higher than the relative recovery that the copper recovery rises. This suggests that, when the pH is natural and uncontrolled, a surfactin concentration of approximately 15 mg / L may be a more efficient concentration compared to the other two tested concentrations, for copper flotation with the provided Merensky ore. The increase in grade associated with lower surfactin concentration may be attributable to fewer micelles resulting in possible entrapment of other particles. The recovery is also lower at the lower surfactin concentration because of the weaker collecting power. Figure 7 shows the effect of surfactin concentration on copper grade and recovery at a natural maintained pH (pH 8.75 - 9.25). The graph illustrates how the copper grade also decreased with increased surfactin concentration when the pH was maintained between 8.75 and 9.25, apart from a slight increase in recovery between the 15 mg / L and 30 mg / L concentrations. As in the case of Figure 6 above, the results plotted in Figure 7 also suggest potential for the use of surfactin as a sulphide mineral collector, being able to recover up to 40% of the copper within the feed while increasing the grade by a factor of about 11, from 0.0634% to approximately 0.69%. Figure 8 shows the effect of surfactin concentration on copper grade and recovery at a lower uncontrolled pH (initial pH of 7.8 declining to 6.4) for oxidised material. The graph illustrates how an oxidised mineral condition resulted in the highest copper grade out of all the runs, including that carried out with a conventional collector (Hostaflot™ 9033), while also indicating the highest sensitivity to grade when the surfactin concentration is varied. According to Error! Reference source not found, the 15 mg / L surfactin concentration run was able to increase the copper grade from 0.0634 wt% to 1.1 wt%, which represents a 17.4 times increase, while recovering 30% of the copper as well. Figure 9 shows the effect of surfactin concentration on copper grade and recovery at a high uncontrolled pH (initial pH 10 declining to 8.2) achieved by the addition of sodium carbonate. The graph illustrates how a high uncontrolled pH condition corresponds to a high copper recovery. This may be attributable to the increased frothing and collection power of surfactin in basic solutions in addition to collecting capabilities. The copper recovery decreased slightly with an increase in surfactin concentration. This may have resulted from true flotation being inhibited by excessive frothing. It is recommended when using the higher surfactin concentrations in basic solutions, to decrease the supplementary frother that is added (Flotanol™ C-07 in the case of the tests). This strategy may result in a higher copper recovery than was observed in the tests, while having a lower decrease in grade, and may be advantageous if fast recovery is more important than high grade. Nickel grade and recovery for various concentrations of surfactin Figure 10 shows the effect of surfactin concentration on nickel grade and recovery at a natural uncontrolled pH (initial pH 9). The nickel recovery was significantly lower than the copper recovery under the same conditions (see Figure 6 above). The highest grade achieved for nickel was 0.55 wt%, which was concentrated from feed with a grade of 0.187 wt%. The grade for nickel recovery therefore increased by a factor of only 2.94, compared to a grade increase factor of about 11 for the copper recovery. This suggests that surfactin has a weak affinity for adsorption and collection of the nickel sulphide mineral, pentlandite, compared to its affinity for collecting the copper sulphide mineral, chalcopyrite. The disclosed method of recovering and upgrading metals by flotation consequently allows for the preferential flotation of either copper sulphide compounds or nickel sulphide compounds. The method can be applied to selectively depress flotation of nickel sulphide compounds while promoting the flotation of copper sulphide compounds, i.e., depressing a floated quantity of the nickel sulphide compound while elevating a floated quantity of the copper sulphide compound. This differential in activity (collecting or depressant) can be used to selectively separate copper sulphide compounds and nickel sulphide compounds from a slurry or other fluid mixture containing both of these compounds. The disclosed method may accordingly provide a mechanism for the flotation separation of chalcopyrite from pentlandite (amongst other mineral combinations) using surfactin and, optionally, at least one frothing agent. As seen in the graph, the nickel recovery and grade increased with increasing surfactin concentration, possibly because the increased froth generated by the surfactin only transported the already hydrophobic pentlandite. Thus, the increase in grade may have resulted from increased bubble stability and not adsorption to the pentlandite itself. Figure 11 shows the effect of surfactin concentration on nickel grade and recovery at a natural maintained pH (pH 8.75 - 9.25). Recovery decreased from the 15 mg / L to the 30 mg / L surfactin concentration, but there was a trend reversal to a high recovery and low grade when moving to the 50 mg / L concentration. This reversal was likely due to entrainment and entrapment caused by high frothing. Figure 12 shows the effect of surfactin concentration on nickel grade and recovery at a lower uncontrolled pH on oxidised material. The nickel recovery continuously increased with an increased concentration but reached a maximum grade between the 15 mg / L and 50 mg / L surfactin concentrations, according to Figure 12. This behaviour is similar to the natural uncontrolled pH conditions of Figure 10. The oxidised material runs have an overall higher grade as well as higher recoveries. The increase in grade corresponding to increased concentration may have been caused by increased froth and bubble stability, allowing the natural hydrophobicity of the pentlandite to facilitate most of the flotation. The decrease in grade for the 50 mg / L concentration may have been caused by entrainment of gangue. Figure 12 further reinforces the notion that surfactin has a higher affinity for copper sulphides than for pentlandite. The flotation of pentlandite resulting from the use of surfactin may be mainly due to increased froth and bubble stability. Figure 13 shows the effect of surfactin concentration on nickel grade and recovery at a high uncontrolled pH (initial pH 10) via the addition of sodium carbonate. The high uncontrolled pH conditions had the lowest nickel grade for all the pH conditions. The grade remained relatively constant with variation of surfactin concentration. The recovery also stayed virtually constant moving from 15 mg / L surfactin to 30 mg / L surfactin. The increase in recovery for the 50 mg / L may be attributable to frothing effects. The frothing properties of surfactin are considered to be the main contributors to the flotation of pentlandite. It was observed that there are no significant froth characteristic differences between 15 mg / L surfactin and 30 mg / L surfactin at a high pH. Thus, the recovery remained generally constant since the overall mass recovery only slightly changed according to Figure 5. Comparison runs: Grade and recovery of copper and nickel for various concentrations of a conventional collector (Hostaflot™ 9033) Figure 14 shows the effect of Hostaflot™9033 concentration on copper grade and recovery during flotation runs ata natural uncontrolled pH (initial pH 9). Hostaflot™9033, an industrial collector, generated high recoveries between 62 and 72%, while concentrating the copper between 0.32 and 0.4 wt%. Its performance compared to surfactin is more consistent. When comparing the results between the Hostaflot™ 9033 runs, a decrease in recovery of copper was observed with an increase in collector concentration. Grade also decreased with an increase in collector concentration. Figure 15 shows the effect of Hostaflot™ 9033 concentration on nickel grade and recovery during flotation runs ata natural uncontrolled pH (initial pH 9). The Hostaflot™ 9033 runs consistently recovered the highest percentage of nickel compared to all the surfactin runs. Figure 16 compares the copper grade and recovery of the highest performing surfactin concentrations (15 mg / L) for each respective pH condition group and the Hostaflot™ 9033 run at 120 mg / L. Figure 17 compares the nickel grade and recovery of the highest performing surfactin concentrations (15 mg / L) for each pH condition group and the Hostaflot™ 9033 run (120 mg / L). Grade-Recovery A significant difference was seen between the grade-recovery for copper and the grade-recovery for nickel when performing flotation with surfactin. This difference can form the basis of a method of separating the two sulphide minerals from each other. Table 1 relates to copper flotation and provides the concentration of the collector for each data point. Analyzing the recovery against an industrial benchmark that is Hostaflot™ 9033, recoveries with surfactin are within 2 % for the high maintained pH condition at 15 mg / L surfactin. This indicates the industrially comparable performance of surfactin in recovering copper minerals. Regarding grade the oxidized mineral ore condition achieved the highest grade beyond that of the industrial reagent indicating a superior ability to concentrate the copper minerals when an oxidized surface is present. Table 1: Selected optimal data points for copper grade-recovery. Condition Surfactin Concentration Copper Grade % wt Copper Recovery % pH Natural Uncontrolled 15 mg / L 0.7% 14% pH Natural Maintained 15 mg / L 0.7% 40% pH Oxidised Uncontrolled 15 mg / L 1.1% 30% pH High Uncontrolled 15 mg / L 0.5% 60% 120 mg / L Hostaflot™ 9033 120 pL / L (Hostaflot™ 9033) 0.3% 62% If grade is the more sought out characteristic, surfactin has increased performance compared to Hostaflot™ 9033. The more the weight on grade is prioritized and increased, the better suited surfactin is as a collector. If recovery is weighted as much as grade, most of the surfactin falls short, except the 15 mg / L concentration at a high uncontrolled pH condition. In conclusion, surfactin is a viable, and in certain circumstances more suitable, option as a froth flotation collector for copper sulphide flotation benchmarked against an industrial collector Hostaflot™ 9033. Table 2 relates to nickel flotation and provides the concentration of the collector for each data point, as well as the normalized grade-recovery number. Based on the results obtained, Hostaflot™ 9033 is a more suitable collector than surfactin for nickel flotation. The highest recovery is again observed for High pH uncontrolled conditions which are however 50 % lower in recovery compared to the industrial collector. The best grade was obtained under oxidized conditions with the recovery only dropping by 10 % compared to the high pH uncontrolled condition. Compared to copper recovery which was from the same mixture the surfactin clearly shows a higher preference for copper flotation and greater separation between copper and nickel than the industrial collector. Table 2: Selected optimal data points for nickel grade-recovery. Condition Surfactin Concentration Copper Grade % wt Copper Recovery % pH Natural Uncontrolled 15 mg / L 0.5% 17% pH Natural Maintained 15 mg / L 0.7% 14% pH Oxidised Uncontrolled 15 mg / L 1.0% 16% pH High Uncontrolled 15 mg / L 0.3% 26% 120 mg / L Hostaflot™ 9033 120 mg / L (Hostaflot™ 9033) 0.7% 42% Summarizing the findings for mineral recovery and upgrading, surfactin demonstrated strong frothing characteristics but had limitations relating to bubble stability. The addition of small quantities of conventional frother were found to alleviate the bubble stability problem, meaning surfactin can serve as an inexpensive alternative to frothing reagent if used in tandem with conventional frothers. An increase in pH resulted in significant increases in frothing. An increase in pH also resulted in an increase in recovery. This may have been due solely to the increased frothing, or the effect of increased pH on the surface activity of surfactin may also have played a role. At lower pH values on oxidised material, the performance of surfactin regarding grade and recovery increased compared to natural, unoxidised samples. This may have been due to increased selectivity of surfactin resulting from a decrease in pH as well as attachment to oxidised surfaces, increasing the hydrophobicity of the mineral particles. With an increase in surfactin concentration, the general trend is an increase in recovery and a decrease in grade. The results included some outliers which may have been attributable to factors such as entrapment, entrainment, and frothing. Surfactin was able to outperform the commercial collector, Hostaflot™ 9033 for the flotation of copper sulphides at certain conditions. Surfactin was able to concentrate copper minerals within the run-of-the-mine Merensky ore from 0.0634 wt% up to 1.1 wt% within the concentrate, while achieving recoveries of 30%. The grade therefore increased by a factor of 17.35 when using surfactin. Recoveries of up to 60% were achieved with surfactin, albeit with a loss of copper grade. The commercial Hostaflot™ 9033 collector was only able to achieve a copper grade of 0.4 wt% with a recovery of 73%. The most favourable conditions for flotation with surfactin were determined to be oxidised material at low pH with a surfactin concentration of 15 mg / L. The results suggested that lipopeptide surfactants including surfactin can be applied as supplementary flotation agents and can perform similarly to commercial collectors while providing a renewable and sustainable solution. The results also demonstrated that surfactin has a significantly higher affinity for chalcopyrite than the nickel sulphide ore, pentlandite, i.e., that surfactin is less suitable to float pentlandite than chalcopyrite. During the pentlandite runs, surfactin could only achieve an increase in grade from 0.187% to 1%, an increase of just 5.347 times. The second highest grade was 0.71% and the recoveries that matched these grades were low relative to Hostaflot™ 9033. The best performing surfactin result, considering a trade-off between both grade and recovery, was a nickel grade (wt%) of 0.68% and a recovery of 23%. By contrast, Hostaflot™ 9033 was able to obtain a nickel grade of 0.69% with a recovery of 42%, almost double that achieved by surfactin. These results suggest that surfactin does not significantly enhance nickel flotation. This property and the difference in affinity that surfactin has for chalcopyrite compared to pentlandite can be applied as a separation method between those compounds. The results of the experiments therefore indicate that surfactin may be useful as a separation agent for separating nickel sulphides and copper sulphides from mixtures containing these components, and for separating copper compounds away from gangue. Synergistic collector performance may occur when lipopeptide surfactants such as, but not limited to, surfactin are used in combination with one or more supplementary collectors, e.g., Hostaflot™ 9033. FLOTATION OF METAL IONS In order to assess the use of surfactin as a collector in ion flotation, surfactin was used in experimental ion flotation runs on solutions of 100 mM Cu2+, Ni2+, and Co2+. At a pH of 7, an air flowrate of 0.08 L / min, and an initial molar ratio of 1:3 (metal ion colligends : surfactin collector) recoveries from the foam overflow were 75.2% of Cu2+, 94.7% of Ni2+, and 98.2% of Co2+ ions. A lower air flowrate resulted in reduced ion recovery, but greater concentration in the foam overflow as a result of lower water recovery. Surfactin demonstrated significantly improved metal recovery than other tested surfactants from literature. Materials 10 mM standard solutions of Cu2+, Ni2+, and Co2+ were produced using 99% assay sulphate salts of each metal and diluted in deionized water. All simulated solutions emulating heavy metal contaminated water used in the experiments were produced from dilutions of these standard solutions. Metal concentrations were modelled against metal concentrations found in industrial waste waters. Sodium surfactin (90% purity) was used. This surfactin was dissolved in deionized water to produce a 5 mM standard solution of surfactin that was used in the experiments. For the purpose of pH control, standard solutions of HNO3 and NaOH were used. A 0.1 M sodium hydroxide solution was produced from 97% assay solid NaOH salt. A 0.1 M HNO3 solution was produced by diluting a 55% nitric acid solution. Method for Ion Flotation A custom micro-flotation rig similar to that used by Bradshaw and O’Connor (1996) was used (Bradshaw, D.J. and O’Connor, C.T., ‘Measurement of the sub-process of bubble loading in flotation’, Miner Eng, vol. 9, no. 4, pp. 443-448, 1996). The rig was modified to include a sparging stone to provide a greater dispersion and density of bubbles in the cell for ion flotation as opposed to single mineral flotation. Synthetic air (0.21% O2 and 0.79% N2) was used as the flotation gas with the flowrates controlled using a needle valve. Aqueous solution within the column was continuously cycled using a peristaltic pump operating at 300 mL / min, as a method of maintaining homogeneity. A sampling port was present at the base of the column to allow sample collection. Solutions were produced by diluting appropriate volumes of 10 mM metal standard solution and 5 mM surfactin standard solution in deionised water up to 150 mL for flotation. Values of pH for each solution were adjusted dropwise to the required pH using 0.1 M solutions of NaOH and HNO3. Table 3 tabulates the operating conditions for the ion flotation experimental runs: Table 3: Operating parameters for ion flotation experiments. Parameter Values Qair (L / min) 0.06, 0.08, 0.10 PH 5, 7, 10 Me2+ / surfactin molar ratio 1:1, 1:3,1:10 Wherein: • Qair refers to air flowrate; • Me2+ refers to metal2+ ions; and • Flotations were run at ambient temperature (22 °C). Concentration factor (CF) and ion removal (R) from feed were calculated using equation (1) and equation (2), respectively: CFt = C-^ (1) co D _ ^0-Cre,t-Vre,t / o\ ^0-^0 Wherein Co, C(fi,t), and C(re,t) are the ion concentration in the initial solution, the floated fraction at time t, and the residual fraction at time t, respectively. These factors were used as metrics to evaluate the effectiveness of the ion flotation process. The flotation process for each run was allowed to proceed for 50 minutes, or until the surfactin concentration remaining in the residual solution was insufficient to maintain foam formation. Samples each having a volume of 1 mL were taken from the residual solution at 0, 2, 5, 10, 20, 30, 40, and 50 minutes. A further sample was taken from the final foam overflow and volume of overflow was also measured after completion of the flotation. Characterization Samples taken from the residual solution and from the foam overflow were adjusted to pH <1 using a 0.1 M HNO3 solution to break the complex and precipitate the surfactin. This was done to ensure no complex was trapped during filtration of samples. The samples were filtered using 0.22 pm nylon syringe filters and the samples were sent for metal analysis. The concentration of heavy metal ions was determined by inductively coupled plasma mass spectrometry (ICP-MS). Results Comparison of metals’ behaviour The flotation of each metal was compared at the experimental condition of 0.08 L / min flowrates, pH 7, and an initial molar ratio of 1:3 metal ion colligends to surfactin. Figure 18 plots the extent of ion removal (primary axis), the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation (primary axis), and the concentration factor of ions into the overflowed foam fraction. For all three metals, significant recovery was observed using surfactin flotation, with 75.2% of Cu2+, 94.7% of Ni2+ and 98.2% of Co2* recovered into the foam overflow after 50 minutes of flotation. The Cu2+ ion removal of 75.2% approximates the levels of recovery seen with conventional surfactants such as SDS or saponin. The near complete extraction of Ni2+ and Co2+ under conditions similar to those used for conventional surfactants confirms the advantages of the disclosed method as a comparatively simple process which makes use of an environmentally benign collector. Figure 19 illustrates the rate of ion concentration out of the solution into the foam overflow by plotting the concentration of metal ions remaining in the residual solution over the duration of the flotation process. The rate of removal of Cu2+ metal ions is slower than that of Ni2+ and Co2+, which both share a similar rate of removal. The slope of the Ni2+ and Co2+ curves flatten as the time approaches 50 minutes, meaning the rate of removal for those ions is slowing and removal is approaching completion. However, the rate of Cu2+ ion removal did not appear to become slower, as shown by the fact that the Cu2+ curve maintains a steady slope across the entire 50 minute flotation. This indicates that a longer flotation may allow for more complete removal of Cu2+ ions, and that the lower removal efficiency for Cu2+ is a result of a slower flotation process. The fraction of water entrained in the foam and partitioned into the froth overflow, or water recovery, was 31.7%, 34.9%, and 39.3% respectively for the Cu2+, Ni2+, and Co2* solutions. The lower entrainment of water in the Cu2+ ion flotation suggests that Cu-surfactin complex hydrophobicity may reduce the froth stability. Surfactin produced a fine wet foam similar to that produced by saponin biosurfactant collectors. Use of defrothers with the latter are known to have little deleterious impact on ion removal (within 5%). Therefore, a defrother may be advantageous to also use with surfactin to reduce water recovery in the overflowed foam fraction. Alternatively, a longer column may allow greater water drainage from the rising foam due to increased foam residence time. Effect of air flowrates Figure 20 illustrates the impact of changes made to the rate of air flow. The graphs plot the extent of (i) Cu2+, (ii) Ni2+, and (iii) Co2+ ion removal from aqueous solution (primary axis), the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation (primary axis), and the concentration factor of metal ions into the foam overflow fraction after ion flotation with surfactin at Qair of 0.06, 0.08 and 0.1 L / min, respectively. The pH was maintained at 7 and the ion to surfactin ratio was initially 1:3 in all cases. An increase in the rate of flow of air through a flotation cell may cause an increase in metal ion removal. The results confirm that this was the case initially when increasing Qajr from 0.06 L / min to 0.08 L / min, as removal of Cu2+ increased from 42.7% to 75.2%, removal of Ni2+ increased from 80.1% to 94.7%, and Co2+ removal increased from 89.4% to 98.2%. An increase in Qajr may lead to an increased quantity of bubbles, and hence a greater bubble surface area ascending through the flotation cell at any given time, assuming flowrates have little effect on bubble size. This greater bubble surface area may explain the increase in ion removal seen when Qajr was increased from 0.06 to 0.08 L / min. The increase in water recovery seen when Qair was increased to 0.08 L / min was also likely a result of increasing bubble velocity through the flotation cell. A further increase of Qair to 0.10 L / min had little impact on the extent of ion removal for both Ni2+ and Co2+; however, this was likely as a result of the ion removal being near complete. As such, the percentage of Ni2+ removed only increased by 1.3% to 96.0%, and the removal of Co2+ was still within 1% of the removal at 0.08 L / min. This could indicate that as extraction of ions by ion flotation approaches completeness, the impact of increasing airflowrate decreases. Figure 21 illustrates the effect of changing air flowrate on the rate of extraction during the flotation process. The graphs show the concentration of metal ions remaining in the residual solution during the ion flotation of a (i) Cu2+ solution, (ii) Ni2+ solution, and (iii) Co2+ solution, performed at Qair of 0.06 L / min, 0.08 L / min and 0.10 L / min, respectively. The pH was controlled at 7 and the initial ratio of metal ions to surfactin was 1:3 in all cases. Figures 21 (ii) and 21 (iii) show that the flotation rate appears to have little dependence on the air flowrate, with the extraction at 0.08 L / min and 0.10 L / min occurring at similar rates for Ni2+ and Co2+, and the rate of ion extraction only being slightly slower for both ions at 0.06 L / min. The notable decrease in ion removal seen forCu2+ ions can be explained by Figure 21 (i), which shows that the flotation of Cu2+ ions at Qajr = 0.10 L / min effectively stopped after 30 minutes. At this point the froth was no longer stable and foam overflow ceased, which in turn suggests that all frothforming surfactin had overflowed at this point. This did not occur with the other metal ion solutions, and the extent of extraction was not as great as that achieved at flowrates of 0.06 L / min and 0.08 L / min, suggesting extraction of Cu-surfactin complexes was not complete. The concentration factor is dependent not only on the extent of partitioning of ions into the foam fraction, but also the entrainment of water in the foam phase. With greater volumes of water entrained in the foam overflow, the ion concentration becomes more dilute. This is demonstrated in Figure 20 by the lower concentration factor seen in cases where the percentage of water in the foam overflow is higher. For this reason, the greatest concentration factor for all three metal ion solutions was achieved at the lowest air flowrate of 0.06 L / min, where the least water was recovered in the overflow, despite the ion removal being greater at higher air flowrates. In view of these results, the preferred CU for a flotation run can be selected dependent on the desired outcome of the run. Lower rates of air flow typically gave a greater concentration factor (and therefore a more concentrated metal product) at the cost of having a slower flotation process and, in some cases, lower extent of ion removal. Lower rates of air flow may accordingly result in reduced ion recovery but greater concentration in the foam overflow as a result of lower water recovery. If more extensive ion removal is required, higher rates of air flow may be more effective, although this comes at the cost of increased volumes of water becoming entrained in the foam fraction and overflowing, reducing the concentration factor. In cases where water is being treated to reuse or recycle, or if entrainment of other components in aqueous solution into the foam is undesirable, the flowrate can be adjusted to allow enough ion extraction without undesirably partitioning large volumes of water into the metal ion rich foam overflow phase. Effect of solution pH The chemistry and activity of surfactin in solution is greatly affected by solution pH. Below around pH 5, the surfactin is protonated and becomes neutral and unavailable for ion binding or froth formation, thereby simultaneously losing its water solubility and metal ion chelating ability. Basic pH resulted in the formation of hydroxide species of metals; however, metal species continued to be concentrated in the overflow even under basic conditions. This suggests that the surfactin collector may adsorb to neutral hydroxide species and allow flotation. Figure 22 shows the impact of pH changes. The graphs plot the extent of (i) Cu2+, (ii) Ni2+, and (iii) Co2+ ion removal from aqueous solution (primary axis), the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation (primary axis), and the concentration factor of metal ions into the foam overflow fraction after ion flotation with surfactin at pH 5, 7 and 10, respectively. Qair was maintained at 0.08 L / min and the ion to surfactin ratio was initially 1:3. The loss of water solubility and chelating ability is clear from the graphs. At pH 5 there is no extraction of metal ions from the solution following flotation with any of the heavy metals. No foam formation was observed due to the precipitation of the surface active surfactin from the solution. As a result, the entire water volume was present in the residual phase after sparging. Lower pH and higher concentration of H+ ions may reduce recovery in ion flotation due to displacement of the colligend from complexes by H+. This is therefore not a symptom of the use of a biosurfactant but rather typical of ion flotation using anionic collectors. The protonation of the collector imposes a lower limit on metal recovery. The greatest extent of ion removal was achieved at pH 7 for all three tested heavy metal ions. Thereafter, as pH increased to 10, the ion removal decreased notably for both Ni2+ and Co2*, while it increased slightly for Cu2+. The lower ions removal is due to the hydrolysis of metal ions at basic conditions. Figure 23 illustrates how, as the pH approaches 10, all metals begin to form neutral hydroxide species that are insoluble in aqueous solution. As these hydroxide species are neutral, it is expected that little interaction with the anionic surfactin will occur. The extraction seen at pH 10 may have been due to the entrainment of their hydroxide species in the foam; however, the concentration factors of the metals being between 1.75 and 2.25 suggests that some selective flotation of the hydroxide species may have been occurring. The results suggest that the operating pH of ion flotation with surfactin is more favourable near neutral pH, as acidic pH sees the precipitation of surfactin from solution without binding colligends, while basic pH leads to formation of neutral metal species that do not interact with the surfactin collector and thereby reduce the ion removal achievable by ion flotation. This means that in cases where aqueous solutions treated by ion flotation are at acidic or basic pH, some pH adjustment may be necessary in order to achieve maximum ion removal or concentration into the froth overflow. Effect of metal ion to surfactin ratio The volume of water entrained in the froth, or water recovery, is strongly dependent on the concentration of foaming surfactant in the solution. The influence of collector structure and frothing ability on water recovery in ion flotation is known, and increased frother dosage in conventional froth flotation leads to increased water recovery by increasing froth stability. Therefore, the increases in excess surfactin not involved in collecting available as a frother has a strong influence on froth stability and water recovery, where increasing the concentration of the surfactin available as a frother may be expected to increase water recovery. Decreasing the concentration of surfactin to an equimolar concentration to the metal ions resulted in negligible froth formation, as a result of all surfactin being involved in metal binding and precipitation. This shortcoming can be addressed by providing an excess of surfactin to act as frother, or by employing one or more additional frothing or foaming agents to create and stabilise the foam. Increasing the concentration of surfactin to 10x that of the metal ions resulted in near complete removal of the Ni2+ and Co2+ ions, and greatly improved Cu2+ recovery; however, water recovery in the overflowed foam fraction approximately doubled as a result of the excess surfactin. Figure 24 illustrates the influence of changing concentrations of excess surfactin. The graphs plot the extent of (i) Cu2+, (ii) Ni2+, and (ill) Co2+ ion removal from aqueous solution (primary axis), the distribution of water recovery in the overflowing foam phase and in the residual solution after flotation (primary axis), and the concentration factor of metal ions into the foam overflow fraction after ion flotation with surfactin at initial metal ion to surfactin ratios of 1:1, 1:3 and 1:10, respectively. QaT was maintained at 0.08 L / min and pH ratio was maintained at pH 7. Typically, an increase in the ratio of collector to colligend results in improved ion removal. When the initial ratio was 1:1, the collector and colligend were present in the theoretical stoichiometric proportions, and as such there was little to no surfactin in excess that could act as a frother and form a stable foam. Without the formation of a stable foam or froth, the flotation process was inhibited and so there was negligible concentration of metal ions out of the solution. When the metal ion to surfactin ratio was initially 1:3, the water recovery in the overflow fraction for each metal ion solution was between 30% and 40%. Figure 25 illustrates that a significant increase in excess surfactin present in the solution has little influence on the dynamics of the metal ion extraction. As seen in Figures 24 (i) and 25, however, by comparison with the removal of Ni2+ and Co2* ions, there was an increased removal of Cu2* ions as the ratio was adjusted from 1:3 to 1:10 (in addition to surfactin concentrating the copper). This outcome can potentially be attributed to the increased water recovery at the ratio of 1:10 ion to surfactin, leading to greater ion extraction as a result of ion entrainment in overflow water. It may also be a result of the excess surfactin providing a more stable foam. Cu-surfactin complexes may be more hydrophobic and agglomerate more strongly than those of Ni- and Co-surfactin. As such, Cu-surfactin complexes may destabilise foam more than the complexes of other metals, as hydrophobic complexes lead to bubble coalescence. While the extraction of metal ions at the ratio of 1:10 is closer to complete, with extraction of Cu2+, Ni2+, and Co2+ reaching 94.4%, 99.7%, and 99.4% respectively, the increase in water recovery in the overflow fraction results in a far lower concentration factor as the concentrate overflow is diluted. This means that in applications where nearly complete heavy metal extraction is necessary, a greater excess of surfactin may be desirable. However, in cases where a concentrated overflow fraction is desired, such as if the metal ions were to be recovered after flotation, it may be preferable to optimise the ratio of ions to surfactin to a point where a sufficient fraction of the metal ions are concentrated without encouraging a large water recovery. Alternatively, the flotation cell may be optimised by providing a taller column allowing more space for water drainage from the froth. Surfactin has not previously been shown to have capabilities for collection (e.g., via chelation) or foam fractionation. The above results demonstrate that surfactin has both of these capabilities. These properties may make it suitable for the removal of metal ions from industrial wastewater. Surfactin was also demonstrated to specifically remove ions from dilute concentrations, potentially positioning this technology amongst technologies that can achieve near total removal of ions. The disclosed method may, for example, find application as a complementary treatment process after an initial alkaline treatment used industrially, to remove more metal ions which may still be present at low concentrations. Surfactin also demonstrated improved metal recovery by comparison with results reported for other surfactants. The disclosed method may provide an environmentally benign biosurfactant for the flotation of metal ions (Cu2+, Ni2+, and Co2+). Surfactin, at a molar ratio of 1:3 ion to surfactin, has been shown to float 75.2%, 94.7%, and 98.2% of an initial 100 pM solution of copper, nickel and cobalt, respectively. Those skilled in the art will appreciate that further improvements in the recovery of metal ions may be achieved by optimising the flotation cell to increase foam residence time or by introducing a defrother to reduce water recovery and allow greater concentration of metal ions in the overflow. Modifications of these types, amongst others, also fall within the scope of the invention. The impacts of air flowrate, molar ratio, and pH as operating conditions on foam fractionation provide insights into key industrial operating criteria. The results of the experiments indicated that greater air flowrates and higher concentrations of surfactin can improve recovery of metal ions from solution. Increasing the gas flow rate modifies the float by increasing the carryover of water into the overflow. A pH of 5 was found to be ineffective (due to surfactin precipitation), while a pH of 10 was less effective than pH 7, likely due to the ionic speciation of the metals in solution tending to hydroxyl precipitates at a high pH. The disclosed method may reduce latent impacts associated with the use of synthetic flotation agents in metallurgical processes. Examples of latent effects include persistence in the environment, dispersion and bioaccumulation. Conventional methods for flotation can involve the use of sodium dodecyl sulphate, methyl isobutyl carbinol (MIBC), cresylic acid or cresol, pine oil or saponin. Surfactin is biodegradable and biocompatible and can be produced from renewable carbon resources. The use of surfactin as a flotation agent may accordingly provide an alternative biodegradable product and a more environmentally friendly alternative to conventional, synthetic flotation agents. Surfactin also exhibits favourable stability in extreme conditions. It is resistant to variations in temperature, salinity, and pH (above 4) in solution. Furthermore, it is a lipopeptide unlike saponin which is a plant derivative. Surfactin can be commercially produced at low costs. Also, the required dosage of surfactin is lower than that required for industrial collectors such as xanthates. Moreover, it is hypothesized that the surfactin solution can be regenerated by dissolving the froth fraction in an acidic solution and separating the metal ions and lipopeptide. In summary, surfactin may be suitable as an inexpensive and environmentally friendly alternative to conventional collectors and frothing reagents. If used in tandem or combination with conventional collectors and frothers, it may reduce flotation costs while providing a more environmentally favourable process than may be obtained using conventional frothers alone. The disclosed method may be applied in industries such as, but not limited to, mining and mine wastewater treatment. For example, the method may be used to separate metal ions or particles of valuable minerals from gangue materials. In wastewater treatment processes, the method could be used for the removal of valuable materials or contaminants from wastewater streams. Other applications in wastewater processes will be apparent to those skilled in the art. Separation of valuable materials from pre-processing materials, post-processing materials and mining waste is encompassed. The disclosed method may accordingly be applied to slurries or other mixtures of unprocessed mined material or ore in its natural state, consisting of the soil and rock of overburden, minerals, middlings, contaminants and impurities. Mining waste is typically created as a by-product of mining operations. The term typically refers to material extracted from the ground and processed during the ore-processing and enrichment phases of the mining process which remains after the valuable materials have been withdrawn. Mining waste has low to no economic value and is typically considered as unusable mineralised material. Efficient separation of valuable material from valueless material is an issue faced at all stages of the mining process. Mining waste products and crushed ore or ROM can include a combination of fine suspended materials, including dissolved metals which can be valuable. Mining waste products can also include reagents, chemicals, and inorganic and organic additives. Such mining waste can present itself in the form of rock waste or processing waste, aqueous solutions, particulate emissions, water treatment sludge, and metallurgical slag, for example. Current methods used to separate and extract metals from gangue in a slurry, tailings, crushed ore, ROM and paste may be insufficient to extract economically feasible quantities of such desired materials while limiting the environmental impact. The present method may provide a way to address that problem. The disclosed method may also find application in desulphurisation to mitigate or prevent acid mine drainage, and for the separation of pyrite and coal. A further application might be the recovery of metals from solutions in the first instance, such as lithium mining which extracts lithium from ground water. Using surfactin and other lipopeptides as flotation agents provides a safe and renewable alternative, or “green chemistry” substitute, for synthetic chemical surfactants and collectors for the effective recovery, upgrading and extraction of metals and minerals, including the selective separation of metal sulphides from one another. The method may provide an environmentally less harmful solution than conventional processes, reducing the ecological footprint of flotation processes. The foregoing description has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure. The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims. Finally, throughout the specification and accompanying claims, unless the context requires otherwise: • the word ‘comprise’ or variations such as ‘comprises’ or ‘comprising’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers; • the term “flotation” will be interpreted broadly and will, without limitation, be understood to include reference to froth flotation, dissolved air flotation, foam fractionation, ion flotation, precipitative flotation, and sorptive flotation processes; • the term “fluid mixture” will be interpreted broadly and will, without limitation, be understood to include reference to mixtures of particulate solids with liquids (suspensions or slurries), and solutions; • the term “metal mineral” will be interpreted broadly and will, without limitation, be understood to include reference to metal-bearing minerals; and • the term “metalloid mineral” will be interpreted broadly and will, without limitation, be 5 understood to include reference to metalloid-bearing minerals. 14 02 25

Claims

1. A method of separating a copper sulphide mineral from a nickel sulphide mineral in a fluid mixture by flotation, the method comprising the steps of:5 introducing a selected quantity of a lipopeptide surfactant into the fluid mixture;introducing a selected quantity of at least one supplementary flotation agent into the fluid mixture;causing a gas to flow through the fluid mixture, thereby to float a froth fraction containing at least some of the lipopeptide surfactant and the copper and nickel sulphide 10 minerals;separating at least a portion of the froth fraction from a residual fraction of the fluid mixture;separating the copper sulphide mineral from the portion of the froth fraction; and separating the nickel sulphide mineral from the residual fraction of the fluid mixture.

2. The method according to claim 1, wherein the lipopeptide surfactant is surfactin.

3. The method according to either one of claims 1 and 2, wherein the supplementary flotationagent is a synthetic frothing agent.

4. The method according to any one of claims 1 to 3, wherein the lipopeptide surfactant is introduced into the fluid mixture in a quantity sufficient to provide an initial concentration of the surfactant in the fluid mixture ranging from about 10 mg / L to about 20 mg / L.25 5. The method according to claim 4, wherein the lipopeptide surfactant is introduced into thefluid mixture in a quantity sufficient to provide an initial concentration of the surfactant in the fluid mixture ranging from about 13 mg / L to about 17 mg / L.

6. The method according to claim 5, wherein the lipopeptide surfactant is introduced into the 30 fluid mixture in a quantity sufficient to provide an initial concentration of about 15 mg / L ofthe surfactant in the fluid mixture.

7. The method according to any one of claims 1 to 6, wherein the supplementary flotationagent is introduced into the fluid mixture in a quantity sufficient to provide an initial 35 concentration of the flotation agent in the fluid mixture ranging from about 5 pL / L to about15 pL / L.14 02 25N)8. The method according to claim 7, wherein the supplementary flotation agent is introduced into the fluid mixture in a quantity sufficient to provide an initial concentration of about 10 pL / L of the flotation agent in the fluid mixture.

59. The method according to any one of claims 1 to 8, which includes a step of controlling a pH value of the fluid mixture.

10. The method according to any one of claims 1 to 9, wherein the fluid mixture has an initial 10 pH in a range from about 7.6 to about 8.0.

11. The method according to any one of claims 1 to 10, wherein the copper sulphide mineral is chalcopyrite.15 12. The method according to any one of claims 1 to 10, wherein the nickel sulphide mineral ispentlandite.

13. The method according to any one of claims 1 to 12, which includes exposing the fluid mixture to oxidising conditions for a selected period of time prior to flotation.

14. The method according to any one of claims 1 to 13, wherein the fluid mixture is a product of a mining process, or a derivative thereof.

15. The method according to claim 14, wherein the fluid mixture includes a material selected 25 from the group consisting of primary ore, run-of-the-mine (ROM) ore, crushed ore, tailings,gangue, paste, and wastewater.

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