Wet magnetic separation process

Abstract

A wet magnetic separation process for beneficiating (extracting and concentrating) paramagnetic lithium-mica minerals from a milled feed stream 2A containing paramagnetic lithium-mica minerals and gan

Description

16 07 25 The present invention relates to a wet magnetic separation process for beneficiation (extracting and concentrating) of paramagnetic lithium-mica minerals from a milled feed stream containing paramagnetic lithium-mica minerals and gangue materials, using a wet 5 magnetic separator, such as Wet High Gradient Magnetic Separator ("WHGMS") to obtain concentrated paramagnetic lithium-mica minerals therefrom suitable for further processing to extract the lithium. The present invention also relates to a magnetic separation apparatus for beneficiation (extracting and concentrating) paramagnetic lithium-mica minerals from a milled feed stream containing paramagnetic lithium-mica minerals and gangue materials. The 10 process of the present invention can be used to achieve >90% recovery of paramagnetic lithium-mica minerals to a concentrate. BACKGROUND OF INVENTION Beneficiation is used in the mining and allied industry to improve the economic value of an ore feed by removing gangue minerals (worthless or low value contaminants) in order to 15 provide a higher grade or concentrated product. Beneficiation can however be a wasteful process in terms of both energy and chemicals. Beneficiation processes typically use high energy milling, chemical surfactants and other agents to improve mineral concentration. Physical means of beneficiating ores can also be used to extract different materials to discrete process streams based on physical characteristics such as for example colour, radiometric, 20 magnetic or electrostatic susceptibility, density, shape or particle size. For example, magnetic separation can be used to separate magnetic contaminants from the desired mineral ore, or to remove a magnetic target mineral from non-magnetic contaminants. Various beneficiation processes can be used in combination to achieve a desired beneficiation efficiency or purity. For example, pegmatites and spodumene hosted lithium deposits (which 25 are currently the world's largest source of lithium production) have been known to be beneficiated using dense media separation and froth floatation technologies as a precursor to extracting the lithium from the spodumene. Floatation technologies require the use of costly consumable surfactants which may be harmful to the environment and can require remediation. One of the key parameters in floatation is the particle size distribution of the 30 feed and it has been shown in several studies that the optimal size range for floatation is 16 07 25 relatively narrow, approximately 20 pm to 150 pm which requires energy intensive milling of the ore, and which can also generate fine particles which cannot be economically recovered. Froth floatation is widely used; however it has been found that spodumene producers typically recover only 60% to 70% of the desired spodumene content of the ore, meaning that 5 30% to 40% of the lithium is lost through process wastes. Furthermore, beneficiation processes for spodumene are complex and typically involving various stages of crushing, grinding, hydraulic sorting, attrition scrubbing, conditioning, multi- stage floatation plus dense media separation. This is time consuming, costly and labour intensive. Spodumene is a pyroxene mineral consisting of lithium aluminium inosilicate LiAI(SiOs)2, is not 10 magnetic or paramagnetic, and so cannot be separated from gangue minerals and concentrated by magnetic separation. Extensive potentially economic deposits of lithium also occur in lithium-mica minerals within granites in Europe and elsewhere, which also contain gangue minerals, principally quartz and feldspar. However lithium has never been extracted commercially from lithium-mica and so 15 to exploit these deposits commercially there is a need to develop an environmentally sustainable and economic method for separation and concentration of the lithium-mica from gangue minerals as a precursor to extracting the lithium from the mica. Micas are chemically the most variable mineral group among all rock-forming minerals. Not all mica minerals contain lithium, but those that do can also contain iron within their crystal 20 matrix or as impurities in the form of sub-microscopic inclusions of iron oxides, which makes them weakly magnetic or paramagnetic. Lithium-mica minerals such as zinnwaldite KLiFeAI(AISi3)Oio(OH,F)2 (potassium lithium iron aluminium silicate hydroxide fluoride) and polylithionite KLii.7Nao.3AISi40ioF(OH) are more complex minerals than spodumene LiAI(Si20e) (lithium aluminium inosilicate) and contain less 25 lithium. Pure zinnwaldite for example contains eight elements with lithium accounting for only 1.59% of the mineral's mass, whereas spodumene contains only four elements of which lithium accounts for 3.73% of the pure mineral's mass. Given lithium-mica minerals' disadvantages of lower grade and higher mineral complexity compared to spodumene there is a need for a beneficiation process for lithium-mica minerals 30 with improved mineral recovery efficiency, with fewer processing steps, improved specificity 16 07 25 for a particular ore, at lower cost and lower environmental impact. There is also a need for a beneficiation process which does not require the use of environmentally damaging reagents or processes. BACKGROUND ART 5 The major sources of commercially mined lithium are from brine solutions (principally in South America) and spodumene containing ores (principally in Western Australia). To date, there has been no commercial production of lithium from lithium-mica rich ores or concentrates. There have been several efforts to beneficiate lithium-mica minerals in the laboratory. 10 Importantly, these prior art efforts focussed on nonmagnetic lithium-mica minerals using gravity or density separation or floatation or on paramagnetic lithium-mica minerals using dry magnetic separation and none of these prior art efforts have involved the proposed sequence of Wet High Gradient Magnetic Separation (WHGMS) or Vertical ring Pulsating Wet High Gradient Magnetic Separation (VPWHGMS). 15 From review of other known methods for the beneficiation of mica, whether or not they are lithium-micas, recovery efficiencies as high as those demonstrated by the invention process are not known in the prior art. Similarly, the magnetic properties of many mica materials are unknown and their utility as a means of separation is previously undescribed in academic and patent literature. 20 The use of magnetic separation of one material from another or the removal of magnetic particles from streams depend upon their motion in response to the magnetic force and to other competing external forces, namely gravitational, inertial, hydrodynamic and centrifugal forces all of which need to be considered when designing an efficient process. A necessary condition for a successful separation of more strongly magnetic from less strongly magnetic 25 particles in a magnetic field is that the magnetic force acting on more magnetic particles must be greater than the sum of all the competing forces. CN108014901A describes a method for extracting lepidolite from lithium porcelain stone ore. The technology comprises the steps that (1) naturally dissociation of the lithium porcelain stone ore is carried out, concretely, screw-thread steel in a sand making machine carries out 16 07 25 four stages of rapid impact on ore grains so that ore crystals are naturally disassembled, and after screening, a mixture of gangue quartz and lepidolite crystals, feldspar and lepidolite are obtained; (2) efficient gravity difference floatation is carried out, concretely, the mixture of the gangue quartz and the lepidolite crystals is subjected to ball milling, magnetic separation, 5 swirling, liquid separation and floatation and thus a lepidolite concentrate and fine silica powder are obtained; and (3) the feldspar and the lepidolite are subjected to continuous high-gradient strong magnet purification, and thus the lepidolite concentrated and albite are obtained. Siame et al. (Minerals Engineering, 2011, vol. 24, pages 1595-1602) describe a study 10 investigating the use of a combination of froth flotation using dodecylamine as collector, and wet high intensity magnetic separation (WHIMS) to extract lithium from micaceous waste from china clay production. CN108525843A describes a method for recovering tantalum-niobium, lepidolite and feldspar powder by utilizing difficult-to-treat mine solid waste, involving the series-connection 15 technology of weak magnetism, medium magnetism and strong magnetism. CN108057513A describes a method for extracting potassium feldspar concentrate and iron lepidolite concentrate from lithium-containing granite pegmatite waste. The method includes the steps that (1) mineral separation and classification are performed; (2) ball-milling screening and classification are performed; (3) gravity separation is performed; (4) magnetic 20 separation is performed; and finally the potassium feldspar concentrate and the iron lepidolite concentrate are obtained. SUMMARY OF INVENTION According to a first aspect of the invention, there is provided a wet magnetic separation process for beneficiating extracting and concentrating paramagnetic lithium-mica minerals 25 from a milled feed stream containing paramagnetic lithium-mica minerals with both highly magnetic and nonmagnetic gangue materials, in which the process comprises feeding the milled feed stream containing paramagnetic lithium-mica minerals and gangue into a Low Intensity Magnetic Separator (LIMS) having a first magnetic field strength to provide a first waste stream comprising highly 16 07 25 magnetic waste material, and a first product stream comprising low to nonmagnetic materials comprising paramagnetic lithium-mica minerals together with nonmagnetic gangue, and subsequently feeding the first product stream into a first Wet High Gradient Magnetic Separator (WHGMS) having a second magnetic field strength which is greater than the first 5 magnetic field strength of the LIMS to provide a second waste stream comprising nonmagnetic gangue and some paramagnetic lithium-mica material, and a second product stream comprising concentrated paramagnetic lithium-mica minerals, and wherein the process further comprises one or more of: feeding the second waste stream produced by the first WHGMS into a second WHGMS having 10 a magnetic field strength which is equal to or greater than the magnetic field strength of the first WHGMS, to provide a third product stream comprising concentrated paramagnetic lithium-mica minerals, and a third waste stream; and / or feeding the second product stream comprising concentrated paramagnetic lithium mica minerals, into a third WHGMS to provide a fourth product stream comprising an increased 15 concentration of paramagnetic lithium-mica minerals compared to the second product stream, and a fourth waste stream. A series of low and high magnetic field strength separations may be used to achieve a high beneficiation mass yield of particular paramagnetic lithium-mica minerals. The process may comprise the use of vertical fluid flow and pulsating slurry feed in 20 combination with the series of low and high magnetic field strength separations to achieve a high beneficiation yield of particular mica minerals. According to a second aspect of the present invention, there is provided an apparatus for the wet magnetic separation of milled paramagnetic lithium-mica minerals from a feed stream containing paramagnetic lithium-mica minerals mixed with highly magnetic and nonmagnetic 25 gangue materials, the apparatus comprising: a feed source comprising milled paramagnetic lithium-mica mineral mixed with highly magnetic and nonmagnetic gangue materials; a Low Intensity Magnetic Separator (LIMS) having a first magnetic field strength configured to receive the feed source, and further comprising a first waste outlet configured to provide 16 07 25 a first waste stream containing highly magnetic gangue material, and a first product outlet configured to provide a first product stream comprising paramagnetic lithium-mica minerals together with nonmagnetic gangue; a first Wet High Gradient Magnetic Separator (WHGMS) having a second magnetic field 5 strength configured to receive the first product stream from the LIMS, and further comprising a second waste outlet to provide a second waste stream comprising nonmagnetic gangue, and a second product outlet configured to provide a second product stream comprising concentrated paramagnetic lithium-mica minerals; in which the second magnetic field strength is greater than the first magnetic field strength 10 of the LIMS, and one or more of: a second WHGMS having a magnetic field strength which is equal to or greater than the magnetic field strength of the first WHGMS, operable to receive the second waste stream from the first WHGMS, and in which the second WHGMS further comprises a third product outlet configured to provide a third product stream comprising concentrated paramagnetic 15 lithium-mica minerals, and a third waste outlet configured to provide a third waste stream; and / or a third WHGMS operable to receive the second product stream from the first WHGMS to provide a fourth product stream comprising an increased concentration of paramagnetic lithium-mica minerals compared to the second product stream from the first WHGMS, and a 20 fourth waste stream. Size classification of the particles is required to ensure the bulk of the material feed is of a size suitable for magnetic separation. Preferably the feed stream has a minimum particle size in the range of between 10 pm and 50 pm The wet magnetic separation process may further comprise desliming the milled feed stream 25 containing paramagnetic lithium-mica minerals to provide a deslimed, milled feed stream containing paramagnetic lithium-mica minerals comprising particles having an average particle size (dso) of greater than 10 pm, preferably greater than 20 pm, preferably greater than 50 pm. Desliming the milled feed stream to remove slimes with an average particle size (dso) of 10 pm or less, preferably 20 pm or less, preferably 50 pm or less reduces the feed 16 07 25 mass by between [10% and 20%] while losing to waste less than [5%] of the contained paramagnetic lithium-mica minerals and removing ultrafine particles that are not readily separated by magnetic separation, floatation or any other means of beneficiation. The feed stream or feed source may comprise a plurality of feed stream fractions. Each feed 5 stream fraction may comprise a milled feed stream containing paramagnetic lithium-mica minerals comprising particles having a maximum particles size within a predetermined maximum particle size range. The feed stream or feed source may comprise a plurality of feed stream fractions, in which one or more, preferably each feed stream fraction, comprises particles within a different predetermined maximum particle size range. The predetermined 10 maximum particle size range within one feed stream fraction may overlap with the predetermined maximum particle size range of one or more other feed stream fractions. The predetermined maximum particle size range within one feed stream fraction may be distinct from the predetermined maximum particle size range of one or more other feed stream fractions. 15 The process may comprise feeding each feed stream fraction ora combination of one or more feed stream fractions into a WHGMS and obtaining a paramagnetic lithium-mica mineral concentrate product stream therefrom. One or more, for example each, feed stream fraction may be fed, for example separately fed or in combination, into the same WHGMS, or into separate WHGMS. 20 The milled feed stream containing paramagnetic lithium-mica minerals or feed source is derived from igneous rock which may be granite. The igneous rock may have been formed during the Variscan orogeny. The igneous rock may form for example part of the Cornubian batholith, the Bohemian batholith, the Mondenubian batholith or the Central French Massif. The milled feed stream containing paramagnetic lithium-mica minerals or feed source is 25 preferably derived from naturally deposited lithium-mica-bearing rock, sediments or anthropogenically generated waste streams or lithium-mica storage dams derived from naturally deposited lithium-mica-bearing rock or sediments. The milled feed stream containing paramagnetic lithium-mica minerals or feed source preferably comprises a slurry containing between 20% and 60% w / w solids, grading between 30 500 and 15,000 ppm lithium. 16 07 25 The first Wet Magnetic Separator preferably provides a magnetic field with a magnetic field strength of less than 2 Tesla, preferably less than 1.5 Tesla, for example in the range of between 0.2 and 1.5 Tesla. The wet magnetic separator is preferably a VPWHGMS. 5 Pulsation may be provided by for example an actuated diaphragm configured to provide pulsation to the separator. The WHGMS preferably comprises one or more VPWHGMS. The VPWHGMS may use an actuated diaphragm pulsation mechanism with a stroke length between 0 and 40 mm, and a stroke rate between 0 and 400 Hz. At least one of the WHGMS is a VPWHGMS. The vertical orientation of the separator ring 10 enables magnetic particle flushing in the opposite direction to the flow of feed material. This enables the more strongly magnetic and or coarse particles to be removed without passing through the full depth of the separator matrix. Additionally, flushing may take place near the top of rotation of the vertical ring where the magnetic field is the lowest, reducing residual attraction of paramagnetic particles. These benefits reduce magnetic matrix plugging and 15 increase mechanical availability. Preferably, the first and / or second and / or third WHGMS is a VPWHGMS. Preferably, each of the first and second and third WHGMS is a VPWHGMS. For example, in one embodiment, each of the low and WHGMS is a VPWHGMS. Also disclosed is a wet magnetic separator comprising: 20 a Low Intensity Magnetic Separator (LIMS) having a first magnetic field strength; and WHGMS having a second magnetic field strength, in which the second magnetic field strength is greater than the first magnetic field strength, and in which the LIMS is operable to receive the feed source and to provide a first waste 25 stream and a first product stream comprising paramagnetic lithium-mica minerals, and in which the WHGMS is operable to receive the first product stream from the LIMS and to provide a second low to non-magnetic waste stream and a second magnetic product stream comprising concentrated paramagnetic lithium-mica mineral. 16 07 25 The process comprises feeding the milled feed stream containing paramagnetic lithium-mica materials into a low-magnetic field strength magnetic separator having a first magnetic field strength to provide a first highly magnetic waste stream, and a low magnetic first product stream comprising paramagnetic lithium-mica minerals. The process further comprises 5 subsequently feeding the low magnetic first product stream into a first WHGMS having a second magnetic field strength which is greater than the first magnetic field strength of the LIMS to provide a second low to non-magnetic waste stream and a second magnetic product stream comprising concentrated paramagnetic lithium-mica mineral. In one embodiment, the apparatus further comprises a scavenger unit operable to receive 10 one or more waste streams from the wet magnetic separator, and to provide a third product stream comprising concentrated paramagnetic lithium-mica minerals, and a scavenger waste stream therefrom. The process may further comprise feeding one or more waste streams obtained from the wet magnetic separator into a scavenger unit to provide a third product stream comprising 15 concentrated paramagnetic lithium-mica mineral, and a scavenger waste stream. In one embodiment, the apparatus comprises a first WHGMS, and a scavenger unit comprising a second WHGMS having a magnetic field strength equal to or greater than the magnetic field strength of the first WHGMS, in which the scavenger unit is operable to receive a waste stream from the first WHGMS and to provide a third product stream comprising concentrated 20 paramagnetic lithium-mica minerals, and a scavenger waste stream therefrom. In one embodiment, the process comprises feeding one or more waste streams from one or more first WHGMS into a scavenger unit comprising a second WHGMS having a magnetic field strength equal to or greater than the magnetic field strength of the first WHGMS to provide the third product stream comprising concentrated paramagnetic lithium-mica minerals, and 25 a scavenger waste stream. The scavenger waste stream may comprise paramagnetic lithium-mica minerals in a concentration below a predetermined minimum amount. The predetermined minimum amount may be selected to correspond to an amount of lithium content which is considered to be uneconomic to use for further extraction. The apparatus may further comprise a cleaning unit operable to receive one or more magnetic 30 product streams from the wet magnetic separator and to provide a fourth product stream 16 07 25 comprising an increased concentration of paramagnetic lithium-mica minerals compared to the magnetic product streams from the wet magnetic separator, and a cleaning waste stream. The process may comprise feeding a magnetic product stream obtained from the wet magnetic separator into a cleaning unit to provide a fourth product stream comprising an 5 increased concentration of paramagnetic lithium-mica minerals compared to the magnetic product stream obtained from the wet magnetic separator, and a cleaning waste stream. The cleaning unit is preferably in communication with a second WHGMS, and in which the cleaning unit comprises a third WHGMS having a magnetic field strength of no more than the magnetic field strength of the second WHGMS magnetic field strength. 10 In one embodiment, the process comprises feeding a magnetic product stream obtained from one or more first WHGMS into a cleaning unit comprising a third WHGMS. The magnetic field strength of the third WHGMS is preferably no greater than the magnetic field strength of the second WHGMS. The third WHGMS provides a fourth magnetic product stream comprising an increased concentration of paramagnetic lithium-mica minerals compared to the magnetic 15 product stream obtained from one or more first WHGMS, and a cleaning waste stream. The cleaning waste stream may contain paramagnetic lithium-mica minerals in a concentration above a predetermined minimum amount. As such, the cleaning waste stream may be recycled, for example reintroduced into the wet magnetic separator (for example one of: the LIMS, the first or second or third or fourth WHGMS) in order to further extract the 20 paramagnetic lithium-mica minerals within the cleaning waste stream. The apparatus may comprise one or more of: LIMS, WHGMS, scavenger units and / or cleaning units, and any combination thereof, operable to receive one or more waste streams. One or more waste streams may be fed into one or more of: the LIMS, WHGMS, a scavenger unit and / or a cleaning unit, and any combination thereof. 25 The apparatus may comprise one or more of: additional LIMS(s), WHGMS(s), scavenger unit(s), cleaning unit(s), floatation unit(s), or any combination thereof, operable to receive one or more product streams. One or more magnetic product streams are preferably fed into one or more of: a further LIMS, a WHGMS, a scavenger unit, a cleaning unit, a floatation unit, or any combination thereof. 16 07 25 Preferably, the process further includes pulsation of at least one of the magnetic separators. Preferably, the process further includes pulsation of the one or more, preferably of at least the first, WHGMS. Preferably, the process further includes pulsation of the second WHGMS. Preferably, the process further includes pulsation of one or more, preferably each, of the low, 5 first high, second high and third WHGMS, or any combination thereof. Pulsation assists the separation of weakly paramagnetic lithium-mica particles by agitating the feed material in the separation zone, for example slurry, and keeping particles in a loose state, thereby minimizing the risk of blockages, accumulation or entrapment on the faces of the magnetic matrix and maximising contact of paramagnetic particles to the magnet while 10 reducing particle momentum aiding in magnetic attraction. The process and apparatus of the present invention has been found to be more tolerant of fine particles as well as of larger particle sizes, and of particles of lower magnetic susceptibility than conventional beneficiation processes. As a result, the process of the present invention is more time and energy efficient and lower cost than conventional beneficiation processes, 15 and does not require the use of chemicals and produces higher mass recovery. Preferably, the wet magnetic separation process for beneficiation of paramagnetic lithium-mica minerals is an exclusively magnetic separation process. In one embodiment, the wet magnetic separation process of the present invention does not involve any additional beneficiation steps other than magnetic separation of the feed. 20 The process of the present invention has been found to provide improved recovery efficiency compared to conventional beneficiation processes including dense media separation and / or floatation. Furthermore, the process of the present invention involves less processing steps, is more economical and more environmentally friendly than conventional beneficiation processes. The process of the present invention does not use environmentally damaging 25 processes or reagents, such as surfactants. The waste products are principally chemically unaltered silica sand and feldspar. Embodiments of the present invention will now be described in further detail in relation to the accompanying Figures: BRIEF DESCRIPTION OF FIGURES 16 07 25 Figure 1 is a schematic illustration of the magnetic separation process for extracting magnetically susceptible lithium-mica minerals by sequentially extracting magnetic fractions of an ore. DETAILED DESCRIPTION 5 Figure 1 shows an embodiment of a magnetic separation apparatus 10 for extracting paramagnetic lithium-mica minerals from a milled feed stream containing paramagnetic lithium-mica minerals 2A. By way of example, the comminution apparatus 12 is operable to produce a milled feed stream containing paramagnetic lithium-mica minerals 2A. The comminution apparatus 12 10 may for example be a device which is configured to mill, and optionally break, crush, grind, and / or vibrate the mineral feed source 1A, IB. The comminution apparatus is a milling device, for example a wet milling device. The comminution apparatus 12 provides a milled feed stream containing paramagnetic lithium-mica minerals 2A having predetermined maximum particle size, for example, of no more than 3 mm. The comminution apparatus 12 also 15 provides a milled waste stream containing paramagnetic lithium-mica minerals 2B having maximum particle size which is found to be greater than the predetermined maximum particle size. The waste stream 2B is recycled and reintroduced to the comminution apparatus 12 as recycled mineral feed stream IB. The apparatus 10 further comprises a cyclone 14 comprising an inlet 16 operable to receive 20 the milled feed stream containing paramagnetic lithium-mica minerals 2A. The cyclone 14 further comprises an outlet 18 to provide a deslimed, milled feed stream containing paramagnetic lithium-mica minerals 4 therethrough. The cyclone is operable to produce a deslimed, milled paramagnetic lithium-mica mineral feed stream having an average particle size (dso) of 10 pm or more, for example 50 pm or more. 25 The apparatus 10 further comprises a LIMS 20 in communication with the outlet 18 of the cyclone 14 to receive the deslimed, milled feed stream containing paramagnetic lithium-mica minerals 4therefrom. 16 07 25 The LIMS 20 is operable to have a first magnetic field strength to produce a first highly magnetic waste stream (not shown) and a first low magnetic product stream comprising paramagnetic lithium-mica mineral 5. The apparatus 10 further comprises a first WHGMS 22 in communication with the LIMS 20 to 5 receive the first product stream comprising paramagnetic lithium-mica mineral 5 therefrom. The first WHGMS 22 is operable to have a second magnetic field strength higher than the first magnetic field strength of the LIMS 20. The first WHGMS 22 is operable to provide a second low to non-magnetic waste stream 7 and a second magnetic product stream 6 comprising paramagnetic lithium-mica mineral. 10 The apparatus 1 may further comprise one or more of: a scavenger unit comprising a second WHGMS and / or a cleaning unit comprising a third WHGMS. It can be seen from Figure 2 that the low to non-magnetic waste stream 7 is fed into the scavenger unit. The scavenger unit comprises a second WHGMS having a magnetic field strength equal to or greater than the magnetic field strength of the first WHGMS 22. The 15 scavenger unit provides a third product stream comprising concentrated paramagnetic lithium-mica minerals 8, and a scavenger waste stream 9. The apparatus 10 further comprises a cleaning unit in communication with the first WHGMS 22. The cleaning unit comprises a third WHGMS having a field strength which is preferably no greater than the magnetic field strength of the second and / or first WHGMS. The third 20 WHGMS receives the second magnetic product stream 6 from the first WHGMS 22 and provides a fourth product stream 11 comprising an increased concentration of paramagnetic lithium-mica minerals compared to the product stream 6, and a fourth waste stream 13. It is to be understood that one or more waste streams may be recycled and reintroduced into any one of: LIMS, one or more WHGMS, scavenger unit and / or cleaning unit, or any 25 combination thereof, in order to further extract and concentrate paramagnetic lithium-mica minerals therefrom. The magnetic concentrate product stream has been found to have an increased efficiency of lithium-mica recovery with low energy consumption and without requiring any non-magnetic beneficiation steps or the use of environmentally harmful chemicals. The process of the 16 07 25 present invention can be used to achieve >90% recovery of paramagnetic lithium-mica minerals to a concentrate. The operating principle of the invention relies on a series of magnetic separation steps which are tuned to enable the selective recovery of materials with different magnetic 5 susceptibilities. The applicant has achieved this through tailoring the forces required for particle capture at each magnetic separation step. For the purpose of initially analysing the forces involved in particle capture, an idealised situation describing the separation process can be applied. A spherical paramagnetic particle in a fluid moving at constant velocity, approaches a ferromagnetic / ferrimagnetic object of circular cross section. A uniform 10 magnetic field applied perpendicular to the object axis magnetizes the object and a magnetic force acting on the particle is developed. If the magnetic force is large enough to overcome the competing hydrodynamic force and gravity then the particle will adhere to the magnetised matrix. This is the underlying principle by which the method described is tuned to a particular separation challenge. The equation that describes the relationship is given 15 below. FM = V•Mp• (dH / dX) where; 20 FM is the magnetic force required V is the volume of the particle Mp is the magnetic susceptibility of the particle dH / dX is the magnetic gradient seen across the particle. 25 The magnetic force required for the separation becomes proportional to three terms: the volume of the particle, the particle magnetization (gauss / gram), and the field gradient over the dimensions of the particle. In the process of the present invention, all of these terms are tuned to improve the recovery yield of the material. The dynamics of this sequence of separations become readily interpretable by substitution into the formula. For each of the 30 target magnetic separation steps of the present invention, a range of parameters for practicing the invention is defined. The process of the invention is particularly suited to the magnetic beneficiation of lithium-mica minerals that show paramagnetic properties. In a general sense, lithium-mica minerals suitable for beneficiation by this process can be described by the general formula: 5 X2Y4-6Z802o(OH, F)4, in which; X is K, Na, or Ca or less commonly Ba, Rb, or Cs; Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, Sn etc.; Z is chiefly Si or Al, but also may include Fe3+ or Ti. 10 Structurally, lithium-mica minerals can be classed as dioctahedral (Y = 4) and trioctahedral (Y = 6). One example of a paramagnetic lithium-mica mineral suitable for concentration using the invention is Zinnwaldite KLiFeAI(AISi3)Oio(OH,F)2 (potassium lithium iron aluminium silicate 15 hydroxide fluoride). 16 07 25

Claims

16 07 251. A wet magnetic separation process for beneficiating extracting and concentrating paramagnetic lithium-mica minerals from a milled feed stream containing paramagnetic lithium-mica minerals with both highly magnetic and nonmagnetic gangue materials,5 in which the process comprises feeding the milled feed stream containingparamagnetic lithium-mica minerals and gangue into a Low Intensity Magnetic Separator (LIMS) having a first magnetic field strength to provide a first waste stream comprising highly magnetic waste material, and a first product stream comprising low to nonmagnetic materials comprising paramagnetic lithium-mica minerals together with nonmagnetic gangue, and10 subsequently feeding the first product stream into a first Wet High Gradient Magnetic Separator (WHGMS) having a second magnetic field strength which is greater than the first magnetic field strength of the LIMS to provide a second waste stream comprising nonmagnetic gangue and some paramagnetic lithium-mica material, and a second product stream comprising concentrated paramagnetic lithium-mica minerals, and wherein the15 process further comprises one or more of:feeding the second waste stream produced by the first WHGMS into a second WHGMS having a magnetic field strength which is equal to or greater than the magnetic field strength of the first WHGMS, to provide a third product stream comprising concentrated paramagnetic lithium-mica minerals, and a third waste stream; and / or20 feeding the second product stream comprising concentrated paramagnetic lithiummica minerals, into a third WHGMS to provide a fourth product stream comprising an increased concentration of paramagnetic lithium-mica minerals compared to the second product stream, and a fourth waste stream.

2. A wet magnetic separation process as claimed in claim 1, in which the milled feed 25 stream containing paramagnetic lithium-mica minerals comprises particles having a maximum particles size of no more than 3 mm.

3. A wet magnetic separation process as claimed in either of claims 1 and 2, further comprising desliming the milled feed stream containing paramagnetic lithium-mica minerals16 07 25having an average particle size (dso) of 50 pm or less to provide a deslimed, milled feed stream containing paramagnetic lithium-mica minerals.

4. A wet magnetic separation process as claimed in any one of claims 1 to 3, in which the or each feed stream comprises a plurality of feed stream fractions, in which the process 5 comprises feeding each feed stream fraction or a combination of one or more feed stream fractions into a corresponding WHGMS and obtaining a paramagnetic lithium-mica mineral concentrate product stream therefrom.

5. A wet magnetic separation process as claimed in any preceding claim, in which the milled feed stream containing paramagnetic lithium-mica minerals comprises a slurry 10 containing between 20% and 60% w / w solids, grading between 500 and 15,000 ppm lithium.

6. A wet magnetic separation process as claimed in any preceding claim, in which the first WHGMS provides a magnetic field with a magnetic field strength in the range of between 0.2 and 1.5 Tesla.

7. A wet magnetic separation process as claimed in any preceding claim, in which the15 first and / or second and / or third WHGMS is a Vertical Pulsating Wet High Gradient Magnetic Separator (VPWHGMS).

8. A wet magnetic separation process as claimed in claim 7, in which the VPWHGMS uses an actuated diaphragm pulsation mechanism with a stroke length between 0 and 40 mm, and a stroke rate between 0 and 400 Hz.20 9. An apparatus for the wet magnetic separation of milled paramagnetic lithium-micaminerals from a feed stream containing paramagnetic lithium-mica minerals mixed with highly magnetic and nonmagnetic gangue materials, the apparatus comprising:a feed source comprising milled paramagnetic lithium-mica mineral mixed with highly magnetic and nonmagnetic gangue materials;25 a Low Intensity Magnetic Separator (LIMS) having a first magnetic field strengthconfigured to receive the feed source, and further comprising a first waste outlet configured to provide a first waste stream containing highly magnetic gangue material, and a first product outlet configured to provide a first product stream comprising paramagnetic lithium-mica minerals together with nonmagnetic gangue;16 07 25a first Wet High Gradient Magnetic Separator (WHGMS) having a second magnetic field strength configured to receive the first product stream from the LIMS, and further comprising a second waste outlet to provide a second waste stream comprising nonmagnetic gangue, and a second product outlet configured to provide a second product stream5 comprising concentrated paramagnetic lithium-mica minerals;in which the second magnetic field strength is greater than the first magnetic field strength of the LIMS, and one or more of:a second WHGMS having a magnetic field strength which is equal to or greater than the magnetic field strength of the first WHGMS, operable to receive the second waste stream 10 from the first WHGMS, and in which the second WHGMS further comprises a third product outlet configured to provide a third product stream comprising concentrated paramagnetic lithium-mica minerals, and a third waste outlet configured to provide a third waste stream; and / ora third WHGMS operable to receive the second product stream from the first WHGMS 15 to provide a fourth product stream comprising an increased concentration of paramagnetic lithium-mica minerals compared to the second product stream from the first WHGMS, and a fourth waste stream.

10. An apparatus as claimed in claim 9, in which the first and / or second and / or third WHGMSisa VPWHGMS.20

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