Patent Application
20240309485
The present application relates to processes for leaching high value metals including battery metals from mineral substrates using acids and or microorganisms.
Geological reserves of hydrocarbons as an energy source are being depleted. Further, the devastating impact of carbon dioxide production from hydrocarbon combustion in driving climate change is becoming increasingly apparent. There is an urgent need to reduce reliance on and usage of hydrocarbon fuels and transition to alternative sources of energy.
However, alternative energy sourcing alone will not be sufficient to enable this transition to occur; energy transport and storage are also challenges that must be addressed to meet current climate change goals. Growing electric vehicle (EV) demand and applications including energy storage systems (ESS) will collectively require an increase in the sourcing and utilization of battery metals and other metals such as lithium, nickel, and cobalt. For example, the global lithium market is projected to grow from USD 3.83 billion in 2021 to USD 6.62 billion in 2028. This will leave an estimated gap in production of 2 million metric tons per annum by 2030.
Techniques to extract metals from the earth have developed over thousands of years. While the mining of metal ores, and the extraction of metal therefrom, is widespread, this has a profound environmental impact. In recent years, the recognition of this impact has become increasingly accepted by the mining industry and steps have been taken to modify such processes to make them more environmentally responsible.
One alternative to conventional mining approaches is to extract metals from clays using leaching techniques. Clays are fine-grained natural sediments made up of weathered minerals and which contain varying levels of metals.
Techniques for leaching metals such as aluminium from clays have been proposed since the 1930s and 1940s. These techniques typically utilize acids, for example sulfuric acid, to facilitate extraction of the metals of interest from the clays. While these processes are relatively effective, the production of sulfuric acid is costly and energy intensive. Additionally, owing to the corrosive nature of sulfuric acid and the related challenges associated with its transport and storage, in acid leaching processes utilizing sulfuric acid, it is typically necessary to construct a plant to produce the acid and or a specially treated tank to store it at the locality where the leaching process is conducted. Further the selective extraction of metals from clays which are present at low concentrations, such as lithium, has proven challenging and inefficient.
The use of microbial leaching of battery metals from ores has been disclosed but these disclosures are typically on a bench scale and/or are cumbersome and inefficient. For example, Reichel et al., Minerals Engineering 106 (2017), pages 18 to 21 disclose the use of sulfur oxidising microorganisms to recover lithium from mica. In the disclosed process, a coarse-grained lithium-containing greisen ore were crushed. Mica was then hand-picked and milled. The obtained milled mica comprised 13,350 ppm of lithium and only a low level of lithium was recovered. Other attempts to microbially recover specific metals from metal-rich ores are disclosed by Rezza et al., Letters in Applied Microbiology, volume 25, 1997, pages 172 to 176; and by Barnett et al., Minerals, volume 8, no. 6, 2018, pages 236 to 246; and also in Chinese Patent Publication Nos. 113981218 and 1958815 and German Patent Publication No: 2557008.
Thus, at present, no cost effective and resource efficient method for mining and processing clays, weathered rocks and other substrates comprising high value metals present at low levels in such materials exists. Therefore, there exists a need for environmentally friendly, cost effective methods for extracting high value metals from clays, weathered rocks and other substrates present in low levels in such materials. Demand also exists for optimisation of the extraction of such high value metals via leaching processes.
Thus, according to a first aspect of the present application, there is provided a method for extracting a high value metal from a mineral substrate comprising:
One advantage provided by the processes of the present application is that, as is demonstrated in the accompanying examples, the inventors unexpectedly found that organic acids can be used to provide highly effective recovery of high value metals from mineral substrates such as clay or weathered rock. More specifically, the examples demonstrate the efficient recovery of lithium, nickel and cobalt from such substrates and thus, in embodiments of the invention, the high value metal is lithium, nickel or cobalt.
Through the use of organic acids as opposed to strong, inorganic acids conventionally employed in leaching processes, the environmental burden of the process is advantageously reduced. The accompanying examples demonstrate that the excellent recovery of high value metals can be achieved using citric acid, oxalic acid and gluconic acid. Thus, in embodiments of the invention, the abiotic organic acid is citric acid, oxalic acid or gluconic acid, save that where lithium is the high value metal, the abiotic organic acid is not oxalic acid.
Advantageously, the methods of the present application can be applied to a range of different types of mineral substrates. In some embodiments, the mineral substrate is a clay or a laterite.
It has been unexpectedly found that organic acid leaching is particularly suitable for use with laterite substrates. Thus, according to a second aspect of the invention, there is provided a method for extracting a high value metal from a laterite comprising:
In this aspect of the application, the organic acid may be abiotic or be microbially produced. As with the first aspect of the invention, citric acid, oxalic acid and gluconic acid may be employed. Additionally, the high value metal may be lithium, nickel or cobalt.
In embodiments of this aspect of the invention in which an organic acid producing microorganism is comprised in the leaching medium, that microorganism may be bacterial (e.g. a bacteria of the genus Gluconobacter, such as Gluconobacter Gluconobacter oxydans or Gluconobacter diazotrophicus) or fungal (e.g. a fungus of the genus Aspergillus such as Aspergillus niger).
Also provided herein is a kit comprising a leaching medium comprising an organic acid and/or an organic acid producing microorganism and instructions to use the medium to leach a high value metal from a laterite.
A more complete understanding of aspects described herein, and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features.
In the following description of the various examples and components of this disclosure, reference is made to the accompanying drawings, which form a part hereof. It is to be understood that other methods may be utilized and that modifications may be made from the specifically described methods.
As explained above, in a first aspect of the present application, there is provided a a method for extracting a high value metal from a mineral substrate comprising:
In this aspect of the invention, the organic acid present in the leaching medium is abiotic, i.e. it is not produced from microbes. For example, the acid may be produced by conventional chemical synthesis. In embodiments, the abiotic organic acid may be provided in solid form, e.g. amorphous or crystalline form and mixed with a liquid medium to form the leaching medium, or may be pre-mixed with a liquid with the resulting mixture then added to a liquid medium to form the acid medium. In certain embodiments, the abiotic organic acid may be provided in liquid form and mixed with a liquid medium to form the leaching medium.
In some embodiments of this first aspect of the invention, the leaching medium does not contain (or contains only de minimis amounts of) acid producing microorganisms and/or acid or protons produced by microorganisms. Additionally, or alternatively, the leaching medium may not contain (or contain only de minimis amounts of) microbial components, microbial products and/or microbial metabolites.
As explained above, in this first aspect of the invention, when the high value metal is lithium, the abiotic organic acid is not a dicarboxylic acid. In certain embodiments, when the high value metal is a group I or group II metal, the abiotic organic acid is not a dicarboxylic acid.
The versatility of the process of this first aspect of the present application permits its use with a wide range of mineral substrates. As used herein, the term “mineral substrate” is used to encompass materials comprising the high value metal. In embodiments, the mineral substrate may be solid, for example it may be a sedimentary material such as clay, a solid precipitate, a weathered rock, or a hard rock (i.e., a rock which is not a clay). The solid mineral substrate may be in bulk form or in particulate or comminuted form. In some embodiments, the mineral substrate may be a liquid (including a liquid medium containing particulate material), for example a leachate, brine, pregnant liquor solution, mining effluent or wastewater.
In embodiments of the invention, in which the mineral substrate is a clay, the clay may be kaolinite, laterite, montmorillonite-smectite, illite, chlorite, smectite, hectorite, vermiculite, talc, pyrophyllite, varve or the like.
In embodiments of the invention in which the mineral substrate is a hard rock, this may be spodumene, goethite, hematite, or the like. In some embodiments, the mineral substrate is not a hard rock. In certain embodiments, the mineral substrate is not a mica, zinnwaldite and/or a spodumene.
In embodiments, the mineral substrate may be naturally occurring.
An advantage of the processes of the present application is that they permit the efficient extraction of the high value metal from mineral substrates such as clays and weathered rocks. Typically, such substrates comprise lower levels of high value metals than hard rock ores selected for extraction processes owing to high content of such metals, thus making clays less attractive for metal extraction processes. However, as is demonstrated in the examples which follow, the processes disclosed herein permit high levels of extraction of high value metal from clays.
It has been unexpectedly found that organic acid leaching is particularly suitable for use with laterite substrates. Thus, according to a second aspect of the invention, there is provided a method for extracting a high value metal from a laterite comprising:
In such embodiments, the organic acid may be abiotic or microbially produced.
In some embodiments of this aspect of the invention, the leaching medium comprises an abiotic acid (optionally an organic acid) and a microbially produced organic acid. In certain embodiments of this aspect of the invention, the acid medium may comprise a microbially produced acid (optionally an organic acid) and an abiotic organic acid.
As demonstrated in the accompanying examples, the processes of the present application advantageously enable high value metals present in low amounts in a mineral substrate to be efficiently and selectively recovered from that substrate. In embodiments, the high value metal is present in the mineral substrate at a level of about 5% or less by weight. However, in embodiments, the high value metal may be present in the mineral substrate at lower levels, for example at a level of about 4% or less, about 3% or less, about 2% or less, or about 1% or less.
In certain embodiments, the high value metal may be present in the mineral substrate at a level of about 50000 ppm or less, about 30000 ppm or less, about 20000 ppm or less, about 10000 ppm or less, about 5000 ppm or less, about 2000 ppm or less, about 1000 ppm or less, about 500 ppm or less, about 200 ppm or less, about 100 ppm or less or about 50 ppm or less. Additionally or alternatively, the high value metal may be present in the mineral substrate at a level of at least about 1 ppm, at least about 2 ppm, at least about 5 ppm, at least about 10 ppm, at least about 20 ppm, at least about 50 ppm, or at least about 100 ppm. In certain embodiments, the high value metal may be present in the mineral substrate in an amount of about 5000 ppm to about 50000 ppm, about 1000 ppm to about 10000 ppm or about 2500ppm to about 25000 ppm.
Those skilled in the art will recognize that the processes of the present application involve acid leaching. In the first aspect of the invention, the leaching medium comprises an abiotic organic acid. In the second aspect of the invention, the leaching medium comprises an organic acid which may be abiotic or microbially produced. Additionally, or alternatively, the leaching medium employed in the second aspect of the invention may comprise an acid producing microorganism, for example an organic acid producing microorganism.
The organic acids that may be employed in all aspects of the present application or which may be produced by organic acid producing microorganisms in the second aspect of the invention may be one or more acids selected from the group consisting of citric acid, gluconic acid, oxalic acid, ascorbic acid, fumaric acid, acetic acid, propionic acid, butyric acid, isobutyric acid, succinic acid, formic acid, malonic acid, tartaric acid, itaconic acid, lactic acid, or mixtures thereof. In preferred embodiments, the organic acid is citric, gluconic and/or oxalic acid.
In certain embodiments, the organic acid may be a dicarboxylic acid, for example dicarboxylic acids comprising 12 or fewer carbon atoms, 10 or fewer carbon atoms, 8 or fewer carbon atoms or 6 or fewer carbon atoms. Examples of dicarboxylic acids which may be employed in processes of the present application as an organic acid include oxalic acid, malonic acid and/or succinic acid.
In embodiments of the second aspect of the invention in which acid producing microorganisms are employed, the acid produced by those microorganisms may be a strong and/or inorganic acid, such as sulphuric acid, hydrochloric acid or nitric acid. In certain embodiments, the microorganism does not produce sulfuric acid, does not primarily produce sulfuric acid or does not produce solely sulfuric acid. In certain embodiments, the microorganism does not produce hydrochloric acid, does not primarily produce hydrochloric acid or does not produce solely hydrochloric acid. In certain embodiments, the microorganism does not produce nitric acid, does not primarily produce nitric acid or does not produce solely nitric acid.
While the use of microorganisms in metal bioleaching processes has been disclosed in the literature, those disclosures highlight the shortcomings of such approaches. For example, in a paper by Verma et al., Industrial and Engineering Chemistry Research, 2019, 58 pages 15381-15393, bioleaching processes are identified as requiring longer reaction times than chemical leaching processes which makes them energy intensive. Surprisingly, as demonstrated in the examples of the present application, excellent recovery of high value metals from mineral substrates over significantly shorter reaction times than those disclosed in the literature have advantageously been observed using the processes of the present application.
In embodiments of the second aspect of the invention, the acid producing microorganism produces one or more acid, for example one or more of the acids discussed herein, at a rate of at least 0.01 mmol/h, at least 0.02 mmol/h, at least 0.05 mmol/h, at least 0.1 mmol/h, at least 0.2 mmol/h, at least 0.05 mmol/h or at least 0.1 mmol/h. The skilled person will be familiar with methods for assessing the rate of acid production of microorganisms, e.g., using standardized colonies and growth media, assessing acid production using HPLC (high-performance liquid chromatography).
Any type of acid producing microorganism which is capable of promoting the leaching of high value metals from mineral substrates may be employed in the second aspect of the present application. In some embodiments, the microorganism may be a fungus, a bacterium or an archaea.
In certain embodiments, the microorganism may be a heterotrophic organism (e.g., a heterotrophic bacteria or fungus), which produces one or more organic acids. Additionally or alternatively, the microorganism may not be a sulfur oxidizing microorganism.
Examples of fungi which may be employed in the second aspect of the present application include Aspergilli (e.g., Aspergillus niger, A. brasiliensis), strains belonging to the genera Nectria, Rhizopus, and strains of wood-rotting fungi, such as Phanerochaete chrysosporium, Trametes menziesii, Pomitopsis pinicol, Schizophyllan commune, Merulius tremellosus among others. In embodiments of the second aspect of the invention, the acid producing microorganism is not an Aspergillus. In certain embodiments of the second aspect of the application, the acid producing microorganism is not Aspergillus niger.
Bacterial strains to be employed in the second aspect of the present application may belong to the genera Acidithiobacillus (e.g., Acidithiobacillus ferrooxidans), Gluconobacter (e.g., Gluconobacter oxydans), Gluconacetobacter (e.g., Glaconacetobacter diazotrophicus), Bacillus (e.g., Bacillus licheniformis or Bacillus subtilis), Poenibacillus (e.g., Paentbacillus polymyxa or Paenibacillus mucilaginosus), Pseudomonas (e.g., Pseudomonas putida), Lactobacillus, Lactococcus, or Sulfobacillus.
In embodiments of the second aspect of the invention, a plurality of microorganism strains may be present in the leaching medium. In embodiments, the plurality of microorganisms may comprise fungal and bacterial strains. In certain embodiments, the plurality of microorganisms may comprise a plurality of bacterial strains. In some embodiments, the plurality of microorganisms may comprise a plurality of fungal strains.
In embodiments in which a plurality of microorganism strains are present in the leaching medium, the plurality of microorganism strains may comprise the acid producing microorganism and one or more additional microorganisms. In embodiments, some or all of the additional microorganisms may be acid producing. In some embodiments, the additional microorganisms may comprise 2, 3, 4, 5, 6, 7, 8, 9, 10 or more than 10 strains. In embodiments, the additional microorganisms may comprise 2 or more strains, 2 to 5 strains, 2 to 7 strains, 2 to 10 strains, 5 or more strains, 5 to 10 strains or 7 or more strains.
The acid producing microorganism potentially employed in the second aspect of the invention may be prepared or treated in any way to render it useful in the process of the present application. In embodiments, the process includes the step of preconditioning the acid producing microorganism. For example, the acid producing microorganism may be cultured in the presence of the mineral substrate, components thereof for example the high value metal, or other substances.
The acid producing microorganism(s) useful in the methods of the second aspect of the invention may be selected or tailored to facilitate preferential leaching of one or more metals in the mineral substrate relative to one or more other metals in the mineral substrate.
The acid producing microorganism may be native, i.e., non-engineered or may be genetically engineered.
In embodiments of all aspects of the invention, the leaching medium may have pH of about 5 or less, about 4 or less, or about 3 or less. In some embodiments, the pH of the leaching medium may be about 1 to about 6, about 1.5 to about 5 or about 2 to about 4.
In embodiments of the first aspect of the invention, the leaching medium may comprise one or more additional abiotic acids. The added abiotic acid may be the same acid as the abiotic organic acid or may be a different acid. In embodiments, the added abiotic acid may be one or more acid selected from the group consisting of citric acid, gluconic acid, oxalic acid, ascorbic acid, fumaric acid, acetic acid, propionic acid, butyric acid, isobutyric acid, succinic acid, malonic acid, formic acid, tartaric acid, itaconic acid, lactic acid, nitric acid, hydrochloric acid and/or sulfuric acid. In certain embodiments, where utilized, the added abiotic acid does not comprise hydrochloric acid, nitric acid and/or sulfuric acid.
The leaching medium may have any composition provided that it permits effective contact between itself and the mineral substrate. In embodiments of the invention, the leaching medium may be aqueous.
In certain embodiments, the leaching medium does not comprise and/or is not contacted with a cathode and/or cathode materials such as LiCoO2, LiNixC1-xO2, LiNi0.33Mn0.33Co0.33O2 and/or LiFePO4.
In embodiments of the second aspect of the invention, the leaching medium may comprise one or more additional acids which may be abiotic and/or microbially produced. The added acid may be the same acid as the organic acid and/or produced by the acid producing microorganism or may be a different acid. In embodiments, the added acid may be one or more acids selected from the group consisting of citric acid, gluconic acid, oxalic acid, ascorbic acid, fumaric acid, acetic acid, propionic acid, butyric acid, isobutyric acid, succinic acid, malonic acid, formic acid, tartaric acid, itaconic acid, lactic acid, nitric acid, hydrochloric acid and/or sulfuric acid. In certain embodiments, where utilized, the added abiotic acid does not comprise hydrochloric acid, nitric acid and/or sulfuric acid.
In embodiments of the second aspect of the invention in which the leaching medium comprises an acid producing microorganism, the leaching medium may comprise a nutritional source, for example a carbohydrate source (e.g., a mono-, di-or polysaccharide, such as sucrose), a nitrogen source (e.g., ammonium chloride) an iron source (e.g., ferrous iron), a hydrogen source and/or a sulfur source.
In embodiments of the second aspect of the invention in which the leaching medium comprises an acid producing microorganism, the acid producing effect of the microorganism is realized in situ in the leaching medium without separate acid production/storage apparatus needing to be set up at the location where the leaching process is being conducted.
In all embodiments of the invention, the leaching medium may be provided in ‘ready to use’ form or may prepared shortly prior to operation of the process.
In embodiments of the first aspect of the application, the process may comprise the step of providing a composition comprising an abiotic organic acid and mixing this with a liquid to produce the leaching medium.
In embodiments of the second aspect of the application, the process may comprise the step of providing a composition comprising an acid producing microorganism and/or an acid and mixing this with a liquid to produce the leaching medium. In such embodiments, the composition may comprise one or more additional microorganisms, a nutritional source as described herein, and/or an added acid.
An additional advantage of the methods of the present application is that they are widely applicable and can be used to recover different high value metals of interest. As used herein, the term “high value metal” encompasses lithium, nickel, cobalt, silver, gold, platinum, boron, titanium, manganese, vanadium, zinc, tantalum, tin, cesium, barium, molybdenum, radium, rhodium, beryllium, or strontium. In certain embodiments, the high value metal is a transition metal. In some embodiments, the high value metal is a rare earth metal. In embodiments, the high value metal is lithium. In some embodiments, the high value metal is nickel. In embodiments. the high value metal is cobalt. In some embodiments, the high value metal is manganese. In certain embodiments, the metal is not uranium and/or a rare earth metal. In certain embodiments, the high value metal is not calcium. In embodiments, the high value metal is not sodium. In some embodiments, the high value metal is not calcium. In some embodiments, the high value metal is not iron. In certain embodiments, the high value metal is not magnesium. In embodiments, the high value metal is not potassium.
In embodiments of the invention, the high value metal may be a group I or group II metal, for example lithium, calcium, magnesium, sodium, potassium, rhodium, beryllium, or strontium.
In embodiments of the invention, the high value metal may be a transition metal.
The high value metal may be present in the mineral substrate and/or in the recovered leachate (i.e., the leachate recovered in step 3) of the processes of all aspects of the invention) in any form. For example, the high value metal may be present in the mineral substrate and/or be in the recovered leachate in elemental form. In embodiments, the high value metal may be present in the mineral substrate and/or be in the recovered leachate in ionic form, for example as a cation. Additionally or alternatively, the high value metal may be present in the mineral substrate and/or be in the recovered leachate in the form of an oxide, a salt, a complex, a conjugate or in any other form. In embodiments, the high value metal may be dissolved in the recovered leachate.
In embodiments of all aspects of the invention, the high value metal may be in the recovered leachate in the form of a precipitate.
In embodiments in which the high value metal is in the recovered leachate in the form of a precipitate, the method of the all aspects of the present application may additionally comprise the step of analyzing the composition of the precipitate.
An additional advantage of the methods of all aspects of the present application is they permit the selective recovery of the high value metal or metals from the mineral substrate. In particular, the high value metal which is selectively leached from the mineral substrate in the processes of the invention may be lithium, nickel and/or cobalt.
In conventional metal leaching processes utilizing sulfuric acid, metals are leached indiscriminately from mineral substrates, typically in dissolved form, requiring costly downstream processes, e.g., crystallization and precipitation steps, to separate out the metal/s of interest from undesirable components. Thus, in embodiments of all aspects of the invention, the content of the high value metal in the recovered leachate (as a weight percentage of all metal comprised in the recovered leachate) is at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 70%, at least about 80%, at least about 90% or at least about 95%. In certain embodiments in which the high value metal is present in the recovered leachate in the form of a precipitate, the content of the high value metal present in the precipitate (as a weight percentage of all metal comprised in the leachate in solid form) is at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 70%, at least about 80%, at least about 90% or at least about 98%.
In some embodiments in which a plurality of high value metals (e.g. nickel and cobalt) are present in the mineral substrate, the processes of the invention permit the selective recovery of one high value metal over the others.
As is demonstrated by the accompanying examples, different organic acids permit the selective recovery of different high value metals. Those skilled in the art, using their common general knowledge and the information and data presented therein will be able to select an appropriate organic acid to facilitate selective recovery of the high value metal, if desired.
In some embodiments of all aspects of the invention, the percentage recovery of the high value metal (i.e., the amount of the high value metal in the leachate collected in step 3 of the processes of the present application) as a weight percentage of the high value metal in the mineral substrate prior to being contacted with the leaching medium), is at least 10% greater, at least 20% greater, at least 30% greater, at least 40% greater or at least 50% greater than the percentage recovery of any other metal in the leachate. As an illustrative example, if a high value metal was recovered with 90% recovery, and a second metal was recovered at 40% recovery, the percentage recovery of the high value metal would be 50% greater than that for the second metal.
In some embodiments, the percentage recovery of the high value metal in dissolved form as a weight percentage of the high value metal in the mineral substrate prior to being contacted with the leaching medium, is at least 10% greater, at least 20% greater, at least 30% greater, at least 40% greater or at least 50% greater than the percentage recovery of any other metal in dissolved form in the leachate.
Additionally, or alternatively, the recovered leachate may not comprise all of the metals present in the mineral substrate. In such embodiments, the recovered leachate may comprise 10 or fewer of the metals comprised in the mineral substrate, 8 or fewer of the metals comprised in the mineral substrate, 7 or fewer of the metals comprised in the mineral substrate, 6 or fewer of the metals comprised in the mineral substrate, 5 or fewer of the metals comprised in the mineral substrate, 4 or fewer of the metals comprised in the mineral substrate, 3 or fewer of the metals comprised in the mineral substrate, or 2 or fewer of the metals comprised in the mineral substrate. In certain embodiments, the recovered leachate comprises calcium and/or magnesium in amounts of 10 wt % or less, 5 wt % or less, 2 wt % or less or 1 wt % or less. In certain embodiments, the recovered leachate comprises calcium and/or magnesium in dissolved form in amounts of 10 wt % or less, 5 wt % or less, 2 wt % or less or 1 wt % or less.
Advantageously, and as demonstrated in the examples which follow, the processes of the invention permit high recovery of high value metal from mineral substrates. Thus, in embodiments of all aspects of the invention, the recovered leachate comprises at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80% or at least about 90% of the high value metal present in the mineral substrate prior to being contacted with the leaching medium (i.e. the percentage recovery). In preferred embodiments, the recovered leachate comprises at least about 80% of the high value metal present in the mineral substrate prior to being contacted with the leaching medium. In some embodiments. the recovered leachate comprises at least about 90% of the high value metal present in the mineral substrate prior to being contacted with the leaching medium.
One additional benefit of the methods of the present application, as demonstrated in the accompanying examples, is that they permit the extraction and recovery of multiple high value metals from a mineral substrate. Thus, in embodiments of all aspects of the invention, the mineral substrate comprises a first high value metal and one or more additional high value metals, and the recovered leachate comprises the first high value metal and one or more additional high value metals.
In such embodiments, the first high value metal but not the one or more additional high value metals may be present in the mineral substrate at a level of 5% by weight or less and/or be a group I or II metal. Alternatively, the first high value metal and the one or more additional high value metals may collectively be present in the mineral substrate at a level of 5% by weight or less and/or all be group I and/or group II metals. In certain embodiments, the first high value metal may be nickel and the additional high value metal may be cobalt.
In embodiments of all aspects of the invention, there may be 1, 2, 3, 4, 5 or more than 5 additional high value metals present in the mineral substrate and/or in the recovered leachate.
The processes of all aspects of the invention, or step 1 and/or step 2 and optionally step 3, may be operated in a reactor or in situ. In embodiments in which the processes of the invention (or step 1 and/or step 2 and optionally step 3) are operated in a reactor, the reactor may take any form, for example a countercurrent reactor, continuous stirred tank reactor (CSTR), an immobilized cell reactor (ICR), trickle bed reactor (TBR), bubble column, gas lift fermenter, static mixer, plug-flow reactor or the like.
In embodiments in which the processes of the invention (or step 1 and/or step 2 and optionally step 3) are operated in situ, they may be conducted in a submerged environment or in a surface environment, for example a heap leach.
Advantageously, the processes of all aspects of the present application may be conducted on an industrial scale. For example, in embodiments, the leaching medium has a volume of about 500 mL or more, about 1 liter or more, about 2 liters or more, about 5 liters or more, about 10 or more liters, about 20 or more liters, about 50 or more liters, about 100 or more liters, about 200 or more liters, about 500 or more liters, about 1,000 or more liters, about 2,000 or more liters, about 5,000 or more liters, about 10,000 or more liters, about 20,000 or more liters, about 50,000 or more liters, about 100,000 or more liters, about 200,000 or more liters or about 500,000 or more liters.
In embodiments of all aspects of the invention, the process comprises the step of pre-treating the mineral substrate prior to it being contacted with the leaching medium in process step 2). For example, in embodiments of the invention, the mineral substrate may be pre-treated (e.g. by grinding, comminuting, shredding, or similar) to increase its surface area (e.g. such that the mineral substrate has an average particle size (d(90)of 25 mm or lower, 10 mm or lower, 5 mm or lower, 2 mm or lower, 1 mm or lower, 500 μm or lower, 200 μm or lower, 100 μm or lower, 50 μm or lower, 20 μm or lower, or 10 μm or lower) and/or plasticity. However, such mechanical pre-treatment is not required; as demonstrated in the examples which follow (and unlike conventional acid leaching processes), the processes of the present application do not require mechanical processing of the mineral substrate prior to the leaching process in order to facilitate the efficient extraction of metal therefrom. Accordingly, in embodiments of all aspects of the invention, the mineral substrate is not provided in crushed, ground and/or comminuted form.
In embodiments, for example in those in which the mineral substrate is a clay or a weathered rock such as laterite, the pre-treatment step may comprise washing the mineral substrate with an acid. In preferred embodiments the acid is a weak acid. The inventors have found that washing mineral substrates such as clays and weathered rocks e.g. laterite with a weak acid prior to the commencement of leaching processes advantageously results in the selective removal of impurities such as carbonates and metals which are not high value metals (e.g. iron, magnesium, calcium and/or aluminum) from the mineral substrate which facilitates downstream leaching processes. The reaction between the weak acid and the carbonates results in the formation of salts which precipitate out from the acid wash and can be easily removed. Thus, in embodiments, the process comprises the step of removing precipitated carbonate and/or extracted non-high value metal/s.
Thus, according to a further aspect of the present application, there is provided a step of pre-treating a laterite comprising: i) providing a laterite; ii) contacting the laterite with a weak acid to produce a mixture comprising the weak acid, the laterite and carbonate and/or non-high value metals (optionally iron, aluminum, magnesium and/or calcium), and iii) separating the laterite from the carbonate and/or non-high value metals.
In embodiments, the weak acid used to wash the mineral substrate (e.g. the laterite) may be an organic acid. Additionally or alternatively, the weak acid may have at least one pKa value of from about 2 to about 6. The weak acid may have at least one pKa value of from about 2.5 to about 5.5 or about 3 to about 5. In this context, “pKa value” means the hydrogen in at least one acid group has a pKa value as stated. Examples of weak acids and the associated pKa values are shown in the table below:
An additional or alternative pre-treatment step in the first aspect of the invention may be an acid leaching step, for example a sulfuric acid leaching step, e.g., one using conventional approaches. In such embodiments, the mineral substrate which is contacted with the leaching medium in step 2) of the process of the invention may be a pregnant liquor solution (PLS) obtained from the acid leaching pre-treatment step. By performing the process of the invention following such a step, the recovery of the high value metal from the mineral substrate is maximized. Further, this permits the selective recovery of high value metals from the mineral substrate following acid leaching. In one such embodiment, the acid used in the acid leaching pre-treatment step is not comprised in the leaching medium used in step 2) of the process of the invention. In certain embodiments, the leaching medium used in step 2) of the process of the invention comprises an abiotic dicarboxylic acid, such as oxalic acid (except in embodiments in which the high value metal is lithium or optionally any group I or group II metal). As demonstrated in the examples which follow, acid leaching processes as worked conventionally, e.g., using sulfuric acid, result in the recovery of PLS containing a mixture of high value metals and the treatment of such PLS with specific abiotic acid results in the selective precipitation of certain, but not all, dissolved metals. If the high value metal is one which is precipitated, then it can be conveniently removed. If the high value metal is not one which is precipitated, then the removal of other metals from the PLS will remove impurities therefrom.
According to a further aspect of the invention, there is provided a process for purifying a pregnant liquor solution comprising a high value metal comprising contacting the pregnant liquor solution with an abiotic organic acid (which is not a dicarboxylic acid if the high value metal is lithium or optionally any group I or group II metal) to selectively precipitate metals other than the high value metal from the PLS and removing said precipitated metals from the PLS. The PLS may be recovered from an upstream acid leaching process. In certain embodiments, the high value metal is lithium. In embodiments of the invention, the dicarboxylic acid is oxalic acid. The dicarboxylic acid used in this aspect of the invention is preferably different from the acid used in the upstream acid leaching process.
The process of all aspects of the invention may further comprise the step of processing the leachate recovered in step 3) of the process of the invention. For example, in embodiments in which the high value metal is present in dissolved form in the recovered leachate, the process of the invention may comprise recovering the high value metal therefrom, e.g. via precipitation, ion exchange and/or electrolysis. In alternative embodiments, in which the high value metal is present in the form of a precipitate in the recovered leachate, the process of the invention may comprise recovering the high value metal therefrom, e.g. by collecting the precipitate from the recovered leachate and/or filtering the precipitate from the recovered leachate.
In certain embodiments of the invention, the recovered high value metal may be subjected to additional treatment steps, for example washing and/or roasting.
In step 2) of the processes of all aspects of the invention, the mineral substrate may be contacted with the leaching medium at a pre-determined ratio. For example, the mass of the mineral substrate in the leaching medium may be at least 0.1 g, at least 0.2 g, at least 0.5 g, at least 1 g, at least 2 g, at least 5 g, at least 10 g, at least 20 g, at least 50 g, at least 100 g, at least 150 g, at least 200 g, at least 250 g, at least 300 g, at least 400 g or at least 500 g per liter of leaching medium. Additionally or alternatively, the mass of the mineral substrate in the leaching medium may be 500 g or lower 200 g or lower, 100 g or lower, 50 g or lower, 20 g or lower or 10 g or lower per liter of leaching medium.
In embodiments of all aspects of the invention, for example in heap leaches, the leaching medium may be present at lower volumes than the mineral substrate. For example, the leaching medium may be provided at a volume of less than 50%, of less than 40% or less than 30% of the volume of the mineral substrate. Additionally or alternatively, the leaching medium may be provided at a volume of more than 2%, more than 5%, or more than 10% of the volume of the mineral substrate.
In certain embodiments, following step 2) of the processes of all aspects of the invention, the leaching medium may be maintained in contact with the mineral substrate for a maintenance period to permit leaching of the high value metal from the mineral substrate.
In some embodiments, the maintenance period is at least 1 hour, at least 2 hours, at least 6 hours, at least 12 hours, at least 24 hours, at least 48 hours, at least 72 hours or at least 96 hours. Additionally or alternatively, the maintenance period is 336 hours or less, 240 hours or less, 168 hours or less, 96 hours or less, 72 hours or less, 48 hours or less or 24 hours or less.
In embodiments of all aspects of the invention, during the maintenance period, the leaching medium may be agitated, e.g., via stirring, agitation and/or countercurrent flow.
During the maintenance period, the temperature of the leaching medium may be controlled. For example, for some or all of the maintenance period, the temperature of the leaching medium may be at least about 10° C., at least about 15° C., at least about 20° or at least about 25° C. Additionally or alternatively, for some or all of the maintenance period, the temperature of the leaching medium may be 90° C. or lower, 70° C. or lower, 50° C. or lower, 40° C. or lower, or 30° C. or lower.
In alternative embodiments, e.g., those in which the leaching medium is cell free, for some or all of the maintenance period, the temperature of the leaching medium may be at least about 50° C., at least about 60° C., at least about 80° or at least about 90° C. Additionally or alternatively, for some or all of the maintenance period, the temperature of the leaching medium may be 150° C. or lower, 130″° C. or lower, 110° C. or lower, or 100° C. or lower.
In embodiments of the invention, the process includes the step of adjusting the pH of the leaching medium, e.g. during the maintenance period. This may be a single step, i.e., a single pH adjustment, or the pH may be adjusted periodically to maintain the pH of the leaching medium at a preferred level. The pH may be adjusted by adding the acid producing microorganism, acid/protons produced by that microorganism, a nutritional source, abiotic acid or alkali as needed. In embodiments in which a pH adjustment step comprising the addition of microbially produced or abiotic acid is performed, the acid may be the same or different to the acid produced by the acid producing microorganism.
In embodiments of all aspects of the present application, the acid present in the leaching medium may form a complex with the high value metal, for example an oxalate if the leaching medium comprises oxalic acid. Thus, in embodiments, the high value metal in the leachate recovered in step 3) of the processes of the invention may be in the form of a metal-acid complex.
Investigations were made regarding the onward processing of the obtained metal-acid complex including the conversion of the obtained metal-acid complexes into carbonates. It was unexpectedly found that the metal-acid complexes could be conveniently converted into metal carbonates via a heat treatment step or through reaction with alkali metal carbonates. Thus, in embodiments, the processes of all aspects of the invention comprise the step of 4) converting the recovered metal-acid complex to metal carbonate. In such embodiments, conversion of the recovered metal-acid complex to metal carbonate may be achieved through heat treatment.
In embodiments in which a metal-acid complex is converted to a metal carbonate via heat treatment, the metal-acid complex may be heated to a temperature of at least about 200° C., at least about 300° C., at least about 400° C. or at least about 500° C. Additionally, or alternatively, the metal-acid complex may be heated for at least about 1 minute, at least about 2 minutes, at least about 3 minutes, at least about 4 minutes, at least about 5 minutes, at least about 10 minutes, at least about 20 minutes, at least about 30 minutes or at least about 60 minutes.
An alternative approach for converting metal-acid complex to metal carbonate which has been developed by the inventors involves reacting the metal-acid complex with an alkali metal carbonate. In such embodiments, the metal comprised in the metal-acid complex is not the same metal as the metal comprised in the alkali metal carbonate.
Reaction of the metal-acid complex with the alkali metal carbonate may be achieved by providing a reaction medium comprising the metal-acid complex and the alkali metal carbonate to produce metal carbonate which may then be recovered from the reaction medium.
In such embodiments, the reaction medium may be aqueous. Additionally or alternatively, the alkali metal carbonate may be sodium carbonate.
In certain embodiments, the reaction of the metal-acid complex with the alkali metal carbonate may be carried out at a temperature of at least about 0° C., at least about 10° C., or at least about 20° C. Additionally or alternatively, the reaction of the metal-acid complex with the alkali metal carbonate may be carried out at a temperature of about 80° C. or less, about 70° C. or less, about 60° C. or less, about 50° C. or less or about 40° C. or less. In certain embodiments, the reaction may be carried out at room temperature.
In some embodiments, the reaction of the metal-acid complex with the alkali metal carbonate may be carried out for at least about 1 hour, at least about 2 hours, at least about 3 hours, at least about 6 hours, at least about 9 hours or at least about 12 hours. Additionally or alternatively, the reaction of the metal-acid complex with the alkali metal carbonate may be carried out for about 7 days or less, about 5 days or less, about 3 days or less, about 2 days or less or about 1 day or less.
In embodiments of the invention, the metal-acid complex converted to metal carbonate has a mass of at least 1 g, at least 2 g, at least 5 g, at least 10 g, at least 20 g, at least 50 g, at least 100 g, at least 200 g, at least 500 g or at least 1 kg.
In embodiments, the metal-acid complex which is converted to metal carbonate is a metal dicarboxylate, for example an oxalate, a succinate or an itaconate. Additionally or alternatively, the metal-acid complex may be a citrate or a gluconate.
The following examples are offered by way of illustration of certain embodiments of aspects of the application herein. None of the examples should be considered limiting on the scope of the application.
Lithium bioleaching was assessed using the following acid producing microbes:
The ability of these microbes to leach metals from a mineral substrate, specifically a clay, was assessed. The elemental composition of the clay (a mixture comprising hectonite, smectite and illite as the metal bearing minerals and calcite, quartz and plagioclase as the host clay with a lithium content of 2325 ppm) is:
A. ferrooxydans was grown to a cell density of 2×108 cells/mL in Basal Salts Media (“Medium 1”) consisting of 30.3 mM ammonium sulfate, 33.2 mM magnesium sulfate heptahydrate, 29.4 mM potassium phosphate dibasic, 5 mM tetrathionate, 50 mM iron sulfate heptahydrate, and trace elements. The medium was prepared at pH 1.8.
In triplicate, 15 mL of the culture was inoculated into 85 mL of Medium 1 in 250 mL erlenmeyer flasks, producing a leaching medium having an initial cell density of 3×107 cells/mL. Two grams of clay was added to each flask for a 2% pulp density. The cultures were monitored daily for the first three days, and pH was re-adjusted using sulfuric acid to maintain pH around 2. The leaching medium was sampled at 0, 7, 14, and 26 days for pH, cell density, and lithium and elemental analysis.
G. oxydans was grown to a cell density of ˜108 cells/mL in DSMZ media recipe 105 (“Medium 2”). In triplicate, 15 mL of the culture was inoculated into 85 ml of Medium 2 in 250 mL erlenmeyer flasks, producing a leaching medium having a cell density of 1.5×107. 2 g clay was added to each flask for a 2% pulp density. Leaches were sampled at 0, 6, 12, and 16 days for pH, cell density; and lithium and elemental analysis.
A. niger was grown on YPD (Yeast Peptone Dextrose) agar plates until sporulation (2 days) at 28° C. Spores were collected and suspended in sterile milliQ water to a spore density of 1.36×107 spores/mL. One mL of spore suspension was inoculated into 99 ml of medium comprising 140 g/L sucrose, 1.64 g/L ammonium chloride, 1 g/L dipotassium hydrogen phosphate, and 0.4715 g/L magnesium sulfate heptahydrate. Two g clay was added to this leaching medium for a 2% pulp density. The flasks were sampled at 0 and 6 days.
Abiotic experiments were set up in duplicate to determine the effect of organic acids produced by microorganisms on leaching group I/II metals from the clays. The organic acids oxalic, citric, and gluconic acids were prepared in 25 g/L and 50 g/L concentrations, and 100 mL of these solutions were added to 150 ml Erlenmeyer Flasks. Following this, the flasks were agitated at 150 rpm and placed in either a 30° C. incubator or placed on a hotplate set to 90° C. These reactions were then incubated under these conditions for T=3 hr. At T=3 hr the agitation ended, and the clay settled to the bottom of the Erlenmeyer Flasks forming a distinct supernatant (leachate). A 1 mL sample of this leachate was taken from the flasks and placed in 1 mL of 3% nitric acid to stabilize any metals in the solution. The 2 ml solution was then filtered using a syringe and a 0.22 μm syringe filter into a 15 mL Falcon Tube with 8 mL of 3% nitric acid to make a final dilution of the 1 mL of leachate 1:10 in a 3% nitric acid solution. This solution was then analyzed via ICP-OES (5900 ICP-OES, Agilent Santa Clara, CA) to detect the percent recovery of ions that were contained in the clay.
Oxalic acid had the highest lithium and magnesium recovery from the 20% slurry when compared to the other organic acids screened at 30° C. and 90° C. during T=3 Hr. This finding was surprising as, to the inventors' knowledge, oxalic acid had not previously been proposed as a leachate for recovering lithium from mineral substrates such as clays.
Pure lithium oxalate was obtained from ChemImpex (Catalog 26493). Five grams of lithium oxalate was added to a ceramic crucible and heated to a temperature of 585° C. for 6 minutes using a RapidFire Pro-LP Electric Kiln Furnace-2200F 10 Min Melt Gold—Programmable Controller (Tabletop Furnace Company Tacoma, WA). After the heating cycle was complete, samples were analyzed using X-Ray Diffraction (XRD) with Reitveld refinement method (Bish and Howard, 1988) using MDI Jade (Newton Square, PA). X-Ray Diffraction (XRD) analyses were performed at OU School of Geosciences (Norman, OK) with a Rigaku Ultima IV instrument, using a Cu radiation source. Scans were retrieved using Bragg-Brentano method within 2-70° 2θ interval with 0.02° step size and 2-second counting time, using fixed slits. The XRD scan of lithium oxalate at T0 is provided as
The following table shows the 2-theta angles and d-spacing values corresponding to the XRD scans in
These figures demonstrate the total conversion of lithium oxalate to lithium carbonate.
Peak intensities from the XRD scans were used to determine the mineral composition of the sample by interfacing with databases from the International Centre for Diffraction Data.
Based on the data analysis from the XRD, it was determined that 44.2% of lithium oxalate was converted into lithium carbonate, while 55.8% of it stayed as lithium oxalate. Complete conversion of lithium oxalate to lithium carbonate was achieved when heated at 585° C. for 6 minutes. Importantly, no lithium oxalate was detected, indicating total conversion of that compound to lithium carbonate.
Pure lithium oxalate was obtained from ChemImpex (Catalog 26493) and pure sodium carbonate was obtained from Sigma-Aldrich (Catalog $7795). 1.5 gram of lithium oxalate was added to 3.5 grams of sodium carbonate in 20 mL of MilliQ) water and reacted at room temperature for 12 hours. Precipitation occurred from this reaction and the solution was centrifuged at 12.1 g for 2 minutes to pellet the precipitates and decant the supernatant. The precipitates from this reaction were then analyzed using XRD and the XRD scan following the 12 hour reaction period is provided as
Data from the XRD scan was then analyzed with Reitveld refinement method (Bish and Howard, 1988), using MDI Jade (Newton Square, PA). X-Ray Diffraction (XRD) analyses were performed at OU School of Geosciences (Norman, OK) with a Rigaku Ultima IV instrument, using a Cu radiation source. Scans were retrieved using Bragg-Brentano method within 2-70° 2θ interval with 0.02° step size and 2-second counting time, using fixed slits. Peak intensities from the XRD scan were used to determine the mineral composition of the sample by interfacing with databases from the International Centre for Diffraction Data. It was found that the reaction product comprised 59.9% sodium oxalate, 31.8% lithium carbonate and 8.3% impurities (believed to primarily comprise hydrogen oxalate hydrate). Importantly, no lithium oxalate was detected, indicating total conversion of that compound to lithium carbonate.
Smectite ore (with a lithium content of 2374 ppm) was attrition scrubbed and provided as a suspended slurry. The percent weight of the ore in its slurry form was found to be 33.2%.
A 2% solids leach by weight of the smectite ore was conducted. 7.53 g of this slurry (2.5 g total solids) was placed in 500 mL Erlenmeyer Flasks and autoclaved to sterilize the ore. Following sterilization of the ore, 117.47 g of filter sterilized DSMZ medium (100 g/L Glucose & 10 g/L Yeast Extract) was mixed with the slurry to provide a mixture with a total mass of 125 grams in the Erlenmeyer Flasks representing a 2% solids leach. Flasks were inoculated with 10% (12.5 mL) of a stationary phase Gluconobacter oxydans culture that had been growing for 72 hrs on DSMZ medium. These flasks were then set on a shaker set to 125 RPM in a 30° C. incubator. This experiment was set up in triplicates with abiotic chemical controls (data not shown).
Samples were collected post-inoculation at days 0, 3, 7, 10, and 14 to monitor the leaching effects of G. oxydans when grown directly in the presence of this ore. A 3 mL sample was taken from the flasks through the experiment to generate cell counts, pH, ICP-OES measurements, and untargeted proteomic analyses. Percent recoveries were calculated (
Smectite ore (lithium content 6954 ppm) was attrition scrubbed and provided as a suspended slurry. The percent weight of the ore in its slurry form was found to be 33.2%. The slurry was further diluted down to 20% solids using MilliQ water for the purposes of this experiment for a final slurry concentration of 20 g smectite ore in 80 g MilliQ Water/Ore
Two acid/slurry mixes were prepared. The first comprised oxalic acid, to simulate the effect of microbially produced oxalic acid. The second comprised sulphuric acid representative of conventional leaching practices. Both mixes comprised a 1:2 acid-to-ore ratio. For the oxalic acid leach, oxalic acid crystals were obtained from Sigma-Aldrich and 10 g of dry crystals were added to the 20% slurry solution to provide a 10 g oxalic acid:20 g smectite ore (1:2) leach. For the sulfuric acid leaches, a concentrated (x>98%) sulfuric acid solution was obtained from Sigma-Aldrich. The specific gravity of this solution was found to be 1.83 and 5.46 mL (˜10 g) was added to the 20% slurry solution for a 10g Sulfuric acid:20 g smectite ore (1:2) leach. These leaches were conducted on hotplates (90° C.) and a stir bar agitated at 180 RPM. The leaches proceeded for two hours, and 2 mL of the supernatant was removed from the leaches and prepared for analysis on ICP-OES to determine percent recoveries of elements from the ore (
As can be seen, sulphuric acid resulted in the indiscriminate leaching out of metals, particularly iron, lithium and magnesium, the oxalic acid leach was more selective in favour of lithium extraction as compared to the other metals. This data demonstrates that oxalic acid and microbes which produce oxalic acid are particularly advantageous for the extraction of lithium.
A clay having the following metal content was identified as suitable for acid leaching:
20 g of the clay was mixed with 5 g of acetic acid (1.045 SG) in 100 ml of total liquid volume to produce a 20% slurry. 2 replicates were set up and stirred at 500 RPM, at a temperature of 90° C. for 2 hours; The treated slurry was then filtered through a 0.22 μm filter. The composition of the filtrates was then analysed by acidification with 5% nitric acid followed by ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) and their. composition was found to be:
The percentages of metal extracted from the clay via the acid washing step was calculated and is shown in
As is apparent from that figure, the weak acid pre-treatment step resulted in the selective extraction of calcium (˜80%) and sodium (˜70%). In contrast, the amounts of lithium, magnesium, iron, potassium and silicon extracted from the clay were modest. The removal of carbonates, primarily calcites from mineral substrates which are to be acid leached is advantageous as this reduces acid consumption and increases leaching efficiency.
This was experimentally demonstrated. Biological leaching experiments were set up with untreated and pre-treated clay in 10% slurry concentration to compare the leaching efficiencies.
More specifically, 10 g of untreated clay was added to 100 ml of DSM105 medium, in two replicates, and Gluconobacter oxydans was inoculated to give a final cell count of 108 cell/ml. In parallel, 2.5 g of acetic acid treated clay collected via filtration was added to 22.5 ml of DSM105 medium, in triplicates, and Gluconobacter oxydans was inoculated to give 108 cell/ml final cell count.
All flasks were incubated at 30° C. for 21 days for the untreated clay and 12 days for the treated clay. Supernatants were taken periodically to measure pH and chemical composition after filtering through 0.22 μm syringe filters. Filtered samples were acidified with 5% HNO3 and submitted to ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy).
The recorded compositions of the leachate obtained from the clay which was not pre-treated by weak acid washing are shown below:
The recorded composition of the leachates obtained from the pre-treated clay are shown below:
As is apparent, pre-treatment of the clay with a weak acid pre-wash significantly increased the leaching efficiency for lithium and magnesium, with substantially higher recoveries of those metals even after a shorter leaching period.
Although this was demonstrated using a biological leaching process, corresponding increase in leaching efficiency would be expected in an abiotic leaching process, e.g. a conventional process using strong acid (e.g. sulfuric acid).
A clay having the following composition was biologically leached using Gluconobacter oxydans;
25 ml of pregnant liquor solution (“PLS”) comprising 2% solids obtained from that leach was transferred to a 150 ml beaker.
A separate sample of 25 ml PLS was transferred into another 150 ml beaker and 0.25 g of oxalic acid crystals were stirred in at 200 RPM at 100° C. for 5 min via a magnetic stirrer.
1 ml of sample from each beaker were filtered through 0.22 μm. 600 μl from each sample was used to prepare 3 replicates (200 μl each) in 10 ml volume, to determine the chemical composition. pH was measured from the remaining 400 μl.
The results obtained are shown below:
Overall, oxalic acid addition to PLS resulted in the selective removal of almost the entire Ca (up to 99%), substantial amounts of Fe (up to 80%), and Mg (up to 41%), while keeping Li in the solution. Although these results were obtained from a PLS generated from a biological leaching process, it is anticipated that the selective removal of corresponding metals from a PLS obtained from other types of leaching processes, e.g. abiotic leaches such as those employing strong acids such as sulfuric acid.
Five clays were selected for leaching, having the following compositions:
Leaching processes were conducted at varying slurry concentrations, temperatures, and leaching times as shown in the following table. Leaching efficiencies were tested using varying amounts of oxalic acid crystals.
The amount of oxalic acid used is quantified in the table below as a weight ratio of oxalic acid crystals:clay. For example, to give a 1:4 acid/clay ratio and 10% slurry concentration, 5 g of clay in 45 g of solution (10% slurry) containing 1.25 g of oxalic acid crystals may be used.
Supernatant samples were taken at end of the leaching periods. Samples were filtered through 0.22 μm syringe-tip filters, and aliquoted for pH and ICP-OES (0.1 ml). ICP-OES samples were prepared to 1:100 dilution via mixing 0.1 ml PLS supernatant with 9.9 ml 5% HNO3 and submitted for analysis. Metal recoveries (%) were calculated based on a given element's initial concentration in the clay, acid solution volume and final concentration of the elements in solution after leaching.)
Metal recoveries obtained via leaching at various condition the following table:
Generally speaking, when varying conditions for s single type of clay are compared, increased temperature, and oxalic acid concentration was observed to result in increased lithium leaching efficiency. Increased duration only increased leaching efficiency only up to 24 hours.
These data demonstrate that 100% lithium recovery from clays can be achieved using the processes of the invention. While these results were obtained from an abiotic leaching process, it is envisaged that corresponding recovery rates would also be achieved with biological leaching processes utilising microorganisms which produce dicarboxylic acids such as oxalic acid.
Nickel laterite ore (3% pulp density)—adapted cultures of Gluconobacter oxydans were gradually spun down at 600 RPM for 5 minutes and 2000 RPM for 3 minutes to separate them from the ore. Cells were then harvested by centrifuging at 10000 RPM for 5 minutes. followed by washing with growth media (Modified DSMZ105: 100 g/l glucose, 10 g/l yeast extract, pH 6.8).
Six splits of 2.5 g of nickel laterite ore (OREAS 194 Standard) were transferred into 125 ml flasks and autoclaved (at dry cycle) for 20 minutes at 121° C. Modified DSMZ105 medium was vacuum filtered through a 0.22 μm bottle top filter in an autoclaved media bottle. 47.5 g aliquots of media for each biotic and abiotic experiment were transferred into triplicate ore-containing flasks. Biotic experiments were inoculated with cell pellets under a laminar flow hood, following resuspending it with media from the respective flasks. After time 0 sampling and cell counts (described below), flasks were placed on a shaker at 150 RPM in a temperature-controlled incubator set to 27° C.
1 ml samples were taken from each flask during the experiments on days 0, 3, 7, and 14. Flasks were weighed before and after sampling to account for evaporative loss and loss from sampling. Using a Petroff-Hauser chamber, small untreated aliquots (200 μl) were spared from biotic reactors for biomass assessment (e.g., cell counts). The remainder of the samples were filtered (0.22 μm) and 200 μl aliquots were used for pH measurements and 100 μl aliquots were diluted 1:100 in 5% nitric acid for ICP-AES. The results observed are presented in the following table:
Gluconobacter oxydans flasks showed a drop in pH to ˜3, and up to ˜39% nickel was leached into solution after 3 days. By day 7, the pH remained at ˜3, and 100% nickel had advantageously been selectively leached and solubilized. Magnesium, iron, manganese, and cobalt were also leached into the solution albeit at lower percentages (
A nickel laterite ore was ground to multiple <200 μm splits and one split was sent for compositional analysis via ICP-OES, followed by 4-acid digestion. The ore contained 1.16% nickel and 0.08% cobalt. Elemental composition of the ore is specified in the table below:
The mineralogical composition of the ore determined by powder X-ray diffraction (XRD) analysis is specified in the following table:
Growth experiments preceding leach experiments were performed for one week, and Gluconobacter oxydans was serially transferred two times before direct leach kinetic experiments. Before indirect leach experiments (microbial culture filtrate), Gluconobacter oxydans was grown in growth media tailored to favor the production of organic acids for one week. After one week, the culture was filtered through 0.22 μm filter to remove biomass, and the filtrate (biolixiviant) was utilized as the leaching agent.
Direct biological, indirect, and abiotic (ore+media) kinetic leach tests were conducted at a 5% pulp density on a nickel laterite ore and incubated at 30° C., shaking at 150 rpm, for a minimum of two weeks. Direct leach tests were inoculated to cell density 107. cells/mL, from ore acclimated cultures described above. Indirect leach tests were performed with the individual culture filtrates produced by each microbe, as described above. Measurements of pH and an ICP-OES multielement scan, were made from 0.2 μm filtered samples at seven time points throughout each leach experiment.
Metal recoveries calculated from the leachate chemistry normalized to the composition of the ore is given in the following table:
indicates data missing or illegible when filed
Overall, leach solution from Gluconobacter oxydans direct leaches contained 56% of the feed laterite nickel and 100+% of the cobalt, while indirect leaching tests solubilized 60% of the feed laterite nickel and 100+% of the c salt (
A nickel laterite ore was ground to multiple <200 μm splits and one batch was sent for compositional analysis via ICP-OES, followed by 4-acid digestion. The ore contained 1.16% nickel and 0.08% cobalt, according to the analysis results. Elemental composition of the ore is specified in the table below:
Mineralogical composition of the ore determined by powder X-ray diffraction (XRD) analysis is specified in the following table:
A series of abiotic organic acid kinetic leach tests were conducted with citric acid, gluconic acid and oxalic acid. All abiotic organic acid kinetic leach tests ere conducted at a 5% pulp density.
In sequential tests, each acid was present at a 100 g/L concentration. Abiotic organic acid kinetic leach tests were incubated at 30° C., shaking at 125 rpm, for two weeks. Measurements of pH, and an ICP-OBS multielement scan, were made from 0.22 μm filtered samples at five time points over the course of each leach experiment.
Metal recoveries calculated from the leachate chemistry normalized to the composition of the ore is given in the following table:
indicates data missing or illegible when filed
Overall, citric acid and gluconic acid leached most of the nickel and cobalt from the laterite (
Oxalic acid tests leached less nickel (3%) and cobalt (6%) compared to citric and gluconic acid; however, oxalic acid solubilized 100% of the feed iron and a substantial amount of other impurities such as magnesium (85%), manganese (37%), calcium (53%) and aluminum (70%). Thus, oxalic acid carries a pre-treatment potential for lateritic ores to remove non-high value metals.
The above description is for the purpose of teaching the person of ordinary skill in the art how to practice the object of the present application, and it is not intended to detail all those obvious modifications and variations of it which will become apparent to the skilled worker upon reading the description. It is intended, however, that all such obvious modifications and variations be included within the scope of the present application, which is defined by the following claims. The aspects and embodiments are intended to cover the components and steps in any sequence, which is effective to meet the objectives there intended, unless the context specifically indicates the contrary.
This application is a Continuation-In-Part of U.S. patent application Ser. No. 18/333,008, filed Jun. 12, 2023, which claims priority to U.S. Provisional Application No. 63/381,174, filed Oct. 27, 2022 and U.S. Provisional Application No. 63/366,336, filed Jun. 14, 2022.
| Number | Date | Country | |
|---|---|---|---|
| 63381174 | Oct 2022 | US | |
| 63366336 | Jun 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 18333008 | Jun 2023 | US |
| Child | 18536684 | US |
