Bioleaching of tailings and concentrates at temperatures above 30°c to obtain cobalt and other metals

Abstract

The present invention relates to bioleaching of tailings and concentrates at temperatures above 30°C to obtain cobalt and other metals, using a specific consortium of microorganisms that allows high recovery of said metals. The consortium is referred to as "Kobold B(S)" (DMS 35389) and is made up of three layers which belong to three genera of microorganisms: Sulfobacillus, Acidithiobacillus and Leptospirillum.

Description

[0001] Bio-extraction of tailings and concentrates at temperatures higher than 30°C to obtain cobalt and other metals.

[0002] TECHNICAL FIELD

[0003] The present invention focuses on a bio-extraction system for the recovery of cobalt and other metallic values ​​from tailings and mining concentrates.

[0004] BACKGROUND AND PREVIOUS ART

[0005] Tailings are a finely ground solid, discarded from mining operations, characterized as an aggregate of gangue minerals. A common mineral in tailings from hydrothermal deposits, pyrite, reacts with water and oxygen when exposed to the atmosphere, generating acid mine drainage (AMD) that can contaminate soil and groundwater. For this reason, tailings are considered a harmful waste for the environment, and mining companies must construct tailings storage facilities that allow them to be disposed of completely isolated from the surrounding ecosystem, taking responsibility for acid mine drainage and other potential environmental impacts.

[0006] On the other hand, tailings contain valuable elements, such as copper in residual sulfides, iron in magnetite, and in the case of pyrite, this mineral often exhibits high concentrations of cobalt, nickel, cadmium, zinc, gold, silver, and other metals and metalloids. When addressing the management of mining waste, particularly tailings, and the recovery of valuable elements, there is a concerted effort to adopt the principles of the circular economy, emphasizing the reuse of treated tailings and the efficient recovery of process water. The adoption of clean and cost-effective technologies, particularly bio-extraction, holds great promise for optimizing mining processes.

[0007] Pyrite, a mineral associated with significant environmental challenges due to its role in AMD generation and the solubilization of heavy metals, warrants special attention. Previous literature and tailings analyses have indicated the presence of cobalt within pyrite. Bio-extraction of tailings or concentrates containing pyrite offers a viable route for the recovery of cobalt, copper, nickel, zinc, and other metals from process solutions after iron removal. Optimal pyrite dissolution via bio-extraction typically occurs within the temperature range of 30 to 45 °C, consistent with the activity of mesophilic and moderately thermophilic microorganisms. Beyond this temperature range, especially in solutions with sulfate concentrations exceeding 50 g / L, further temperature increases do not significantly improve dissolution.Given the fine particle size of the tailings material to be treated (below 100 microns), its use in mini-columns and heaps on an industrial scale requires agglomeration on larger supports, such as coarse sand or quartz, to ensure optimal liquid permeability during irrigation. Therefore, the literature on pyrite bioleaching typically uses agitated flasks or tanks (Zang, L. (2008). Bioleaching of pyrite by A. ferrooxidans and L. ferriphilum. Transactions of Nonferrous Metals Society of China, 18(6), 1415-1420), which increases the cost and complexity of the process. A new method for obtaining metals from tailings is needed, one that does not require agitation or reactors, and that is also efficient. To address these challenges, our group initiated this work to extract cobalt from tailings using bioleaching technologies.Microorganisms crucial for biomining were isolated from process samples obtained from a mining company located in the Atacama Region of northern Chile, known for its rich iron-copper-gold (IOCG) deposits. Bioleaching experiments were conducted in flasks using tailings, specifically focusing on the fraction below 37 microns, to evaluate the technical feasibility of cobalt extraction from pyrite, its host mineral. The experiments were performed under shaken flask conditions at 30 °C and 45 °C, with 20% pulp density and isolated microbial consortia. The inoculum comprised a consortium exhibiting iron- and sulfur-oxidizing activities, with microorganisms predominantly from the genus Suifobacius.Surprisingly, our findings demonstrate cobalt recoveries of up to 93% through bioleaching of pyrite within tailings using pulp densities that double the values ​​of 10% previously reported in the literature (Zhang, R., & Schippers, A. (2022). Stirred-tank bioleaching of copper and cobalt from mine tailings in Chile. Minerals Engineering, 180, 107514).

[0008] In the prior art, we find some documents closely related to the present invention, although none anticipate it. For example, PCT application WO2022026833AT (Rio Tinto Tech Resources Inc [US] 2022-02-03) indicates in its abstract that it is a method for recovering metals such as copper, nickel, zinc, and cobalt from materials containing metallic sulfides, especially waste materials containing pyrite. The technique includes mixing the material with pyrite to form agglomerates, and leaching in heaps or flotation circuits. However, despite including it in its abstract, the document does not provide specific results on cobalt extraction, as the examples and tests focus primarily on copper. Furthermore, it indicates the use of ferrous iron and sulfur-oxidizing microorganisms, such as bacteria or archaea, without specifying their genus, much less their species.Since the inventors conducted various tests before finding the consortium of microorganisms used in the invention, we know that not every microorganism allows for adequate metal recovery. This document clearly does not anticipate the specific consortium of microorganisms used in the invention.

[0009] Another related document, US2020340076A1 (Locus IP Co LLC [US] 2020-10-29), discloses a bioleaching method for the extraction of minerals and metals, including cobalt. This process utilizes biosurfactant-producing microorganisms, such as the yeast Starmerella bombicola, and their growth byproducts, particularly glycolipids and lipopeptides, which act as biosurfactants. In this technology, the ore is crushed, mixed with the biological agent, and the metals and minerals are separated from the ore and collected by physical methods such as froth flotation, magnetic separation, or gravity. It is noted that the process is carried out at lower temperatures than traditional methods. The document does not describe the efficiency of the process. Thus, this document does not employ the consortium of the invention, nor does it anticipate bioleaching at temperatures above ambient temperature, as applied in the invention.

[0010] Thus the invention provides a new method of cobalt recovery not anticipated in the prior art.

[0011] BRIEF DESCRIPTION OF FIGURES

[0012] Figure 1. Cobalt extraction over time. Cobalt extraction is measured in tests in flasks maintained at 30°C or 45°C in the presence (Kobold B (S)) or absence of inoculum of the Kobold B(S) consortium (DSM35389) (No Inoculum).

[0013] Figure 2. Iron extraction over time. Iron extraction is measured in the same tests in flasks maintained at 30°C or 45°C in the presence (Kobold B (S)) or absence of inoculum from the Kobold B(S) consortium (DSM35389) (No Inoculum). Figure 3. ORP over time. The redox potential (ORP) is measured in the same tests in flasks maintained at 30°C or 45°C in the presence (Koboid B (S)) or absence of inoculum from the Kobold B(S) consortium (DSM35389) (No Inoculum).

[0014] Figure 4. Acid consumption over time. Acid consumption is measured in the same tests in flasks maintained at 30°C or 45°C in the presence (Koboid B (S)) or absence of inoculum of the Koboid B(S) consortium (DSM35389) (No Inoculum).

[0015] Figure 5. Evolution of pH and ORP over time. The pH (left axis, from 0.4 to 1.9) of the flask liquor and the redox potential (ORP, right axis from 300 to 540) are plotted for the condition of presence of the Koboid B(S) consortium (DSM35389) at 30°C.

[0016] Figure 6. Photograph of the mini-columns used in example 3.

[0017] Figure 7 A. Cobalt extraction in columns up to 50 days with different doses of inoculated microorganisms: 1x10 7 5x10 7 and 1x10 8microorganisms per gram of ore. The percentage of cobalt recovery is measured from columns with Scavenger Tailings (Scv Tailings) inoculated or cured with the Koboid B(S) consortium (DSM35389) grown at 45°C or uninoculated.

[0018] 7 B. Cobalt extraction in columns up to 120 days. The percentage of cobalt recovery is measured from columns with Scavenger Tailings (Scv Tailings) inoculated or cured with the Koboid B(S) consortium (DSM35389) grown at 45°C (KB), at a single inoculum concentration: 1x10 7 microorganisms per gram of mineral or uninoculated.

[0019] Figure 8 A. Nickel extraction in columns up to 50 days with different doses of inoculated microorganisms: 1x10 7 5x10 7 and 1x10® microorganisms per gram of ore. The percentage of Nickel recovery is measured from columns with Scavenger Tailings (Scv Tailings) inoculated or cured with the Koboid B(S) consortium (DSM35389) grown at 45°C or uninoculated.

[0020] 8 B. Nickel extraction in columns up to 120 days. The percentage of nickel recovery is measured from columns with Scavenger Tailings (Scv Tailings) inoculated or cured with the Koboid B(S) consortium (DSM35389) grown at 45°C (KB), at a single inoculum concentration: 1x10 7 microorganisms per gram of uninoculated mineral. DETAILED DESCRIPTION OF THE INVENTION

[0021] The invention relates to a tailings treatment system for obtaining cobaite and other metallic values ​​through bioleaching at temperatures higher than ambient.

[0022] To achieve this, the inventors have developed a bioleaching system that employs a specific consortium of microorganisms, enabling high metal recovery from metal-containing tailings. This consortium, named “Kobold B(S)”, consists of three strains belonging to three genera of microorganisms: Sutfobacfflus, Aciditiobacillus, and Leptospirillum, identified using the next-generation DNA sequencing technique “Illumina”. Sutfobacfflus has been identified as the predominant microorganism. This Kobold B(S) consortium was deposited in the DSMZ and received the deposit number DSM 35389.

[0023] The developed bioleaching system does not use stirred tanks, allowing for simple operation without energy expenditure on agitation, and simultaneously eliminating the volume limitations imposed by a bioreactor. This new system enables the treatment of copper mining tailings containing cobalt-bearing pyrite, recovering not only cobalt in the form of salt, but also iron and other valuable metals such as nickel and zinc. A specific microbial consortium has been obtained that is capable of bioleaching the mineral at temperatures above ambient, between 21 and 60°C, and preferably between 30 and 45°C. The Kobold B(S) consortium (DSM 35389) comprises a strain of Sutfobacfflus thermos ulfidoox idans, a strain of Acidithiobacfflus catdus, and a strain of Leptospirosis sp.

[0024] This system allows, for the first time, the treatment of copper mining tailings through bioleaching at temperatures above ambient, to extract cobalt, iron, and other residual minerals sequentially and efficiently from pyrite. It is worth noting that processing and dissolving pyrite through bioleaching prevents this mineral from reaching the final tailings, effectively de-escalating the tailings and inhibiting the potential for wastewater and pollution generation. It also reduces the chemical and physical risks and hazards that these large deposits of environmental liabilities can pose. The system of this invention does not use agitated tanks, which is the current proposed technology, and therefore is not limited by the maximum 10% tailings content restriction for slurry treatment.It also avoids the high costs associated with agitation, and furthermore, it harnesses the heat generated by the exothermic reaction of pyrite dissolving in contact with water or aqueous solutions, as well as other exothermic mineralogical reactions, to raise the reaction temperature above ambient temperature. In this way, the process of the invention leverages all the principles of a circular economy to reprocess a material that is currently considered waste and transforms a liability into a mining asset.

[0025] Surprisingly, the inventors have achieved a very high recovery of cobalt and iron from the ore with the Kobold B(S) consortium (DSM 35389) of the invention, without the need for agitation, achieving up to 70% cobalt recovery and 65% iron recovery in 15 days. Depending on the mineralogy of the substrate to be leached, it is possible to recover other valuable metals present, such as nickel, zinc, and cadmium, among others. Additionally, the inventors have established that the consortium can withstand extremely acidic pH levels, close to pH 1. This characteristic solves a potential problem in the method of the invention, since, because it is not carried out in bioreactors, it is more difficult to control all the process conditions, including pH variations due to water-mineral reactions.However, since the consortium of the invention withstands extremely acidic pH, in case the pH drops abruptly, the continuity of the process is ensured, without requiring a reconditioning or re-equipment of the reaction stack or column.

[0026] The inventors have observed that the invention process significantly accelerates the bioleaching kinetics of the minerals, which would otherwise occur in a substantially longer time.

[0027] Specifically, the invention relates to a method for bioleaching cobaltiferous pyrite comprising the steps of: a) Inoculating tailings containing cobaltiferous pyrite with a microbiological consortium containing the Kobold B (S) DSM 35389 consortium; particularly the consortium is inoculated at a concentration between 10 6a) 10-10 total microorganisms / g of ore; b) Raise the temperature of the inoculated tailings to between 30°C and 60°C; c) Add solutions containing ferrous ions at a concentration between 0.5 and 5 g / L; d) Incubate for 10 to 50 days in flasks and 40 to 120 days in columns; e) Recover the bioleached solution containing cobalt and other metals in solution. The process is carried out without agitation; in one embodiment, the temperature rises naturally due to mineralogical reactions. This process can be carried out at a pH between 3 and 0.5. The consortium also contains Sulfobacillus thermosifluidooxidans, Acidithiobacillus caldas, and Leptospirum sp. This process allows the recovery of metals such as iron, nickel, cadmium, and zinc. Preferably the B (S) DSM 35389 consortium inoculated in step a) has been previously grown at a temperature between 30 and 60°C; especially at 45°C.This method accelerates the bioleaching kinetics, allowing at least an additional 5% of metal to be recovered in the same amount of time.

[0028] In a second embodiment, the invention also targets the microbiological consortium for bioleaching of tailings with cobaltiferous pyrite comprising a strain of Sulfobacillus thermos ulfidoox idans, a strain of Acidithiobacsllus caldus, and a strain of Leptospirillum sp. and which has been deposited under the deposit number DSM 35389.

[0029] The batteries of the invention are constantly irrigated with an acidified solution, at the operating pH, i.e., at a pH between 0.5 and 3, preferably at a pH between 1 and 2, especially at 1.5.

[0030] The invention may be better understood in light of the following illustrative examples.

[0031] EXAMPLES

[0032] Example 1, Obtaining the microbiological consortium of the invention

[0033] To obtain the consortium required for the invention process, mineralogical samples were obtained from 12 different stages of a copper flotation recovery process from a deposit containing cobaltiferous pyrite. It is presumed that these samples could contain microorganisms capable of bioleaching cobalt associated with pyrite.

[0034] Each of these initial samples was separated into different subsamples to be subjected to different conditions. For each sample, two duplicate assays were performed, where each was incubated in a flask with Modified 9K culture medium in the presence of cobalt pyrite for 4 weeks. Two samples were maintained with shaking at 30°C and the other two at 45°C.

[0035] After this time, both microbial growth and bioleaching of the cobalt added to the flask were evaluated.

[0036] The samples with the best results were selected and blended to obtain a bioleaching pool. This artificially obtained pool has been tested under different conditions and has remained stable for more than 60 passes, maintaining the improved bioleaching conditions. This has led to the creation of the Kobold B(S) consortium (DSM 35389) used in the invention. The consortium, identified as Kobold B(S) with accession number DSM 35389, was originally deposited on February 13, 2025, at the Leibniz Institute DSMZ (Address: Inhoffenstr. 7 B, D-38124 Braunschweig, Germany). Its viability was confirmed on February 21, 2025, and it was declared viable.

[0037] The Kobold B(S) consortium (DSM 35389) has been established to comprise bacteria of 3 different species: Sulfobacillus thermos ulfidooxidans, Acsdithiobacillus caídas, and Leptospirillum sp. The predominant bacterium is Sulfobacillus thermos ulfidooxidans.

[0038] Example 2, Bioleaching with the Kobold B(S) consortium (DSM 35389)

[0039] Once the Kobold B(S) consortium of the invention in Example 1 was obtained, bioleaching tests were carried out in flasks, evaluating the consortium at two different temperatures, 30°C and 45°C, in duplicate. As a control, the mineral without inoculum was evaluated at each temperature.

[0040] In each flask, 20% tailings, specifically Scavenger tailings, was added, the composition of which is shown in Table 1. Each flask had a volume of 50 mL and was inoculated with 5 mL of consortium inoculum, at a final concentration of 1x10 7 microorganisms per gram of mineral.

[0041] Modified 9K medium ((NhkjzSCU, 247.5 mg / L; NaHzPO HzO, 36.5 mg / L; KH2PO4, 13.125 mg / L; MgSOrTHzO, 25 mg / L; CaCl, 5.25 mg / L) was added and 1 g / L of Fe was added as an additional feed source 2+ to all the flasks. The results are shown in Figures 1 and 2.

[0042] In the case of cobalt, it can be observed that under all conditions with the Kobold consortium (DSM 35389), a very high extraction is obtained compared to the controls without inoculum, reaching almost 70% extraction after 15 days of bioleaching (Figure 1).

[0043] In the case of iron, the best conditions were observed at 30°C with the consortium, where by day 15 there was a recovery of between 60 and 70% of this metal (Figure 2). Additionally, the inventors measured other reaction parameters, such as the oxidation-reduction potential (ORP) and acid consumption during the process. Figure 3 shows the variation of ORP under the different conditions. It can be seen that the ORP increases significantly in the presence of the consortium of the invention compared to the uninoculated ore and is higher at 30°C than at 45°C. This is expected because the redox potential increases due to the iron-oxidizing activity of the inoculated microorganisms. On the other hand, the fact that the redox potential is lower at 45°C is possibly due to ferric ion precipitation, which increases with temperature.

[0044] Conversely, acid consumption is substantially higher in the samples without inoculum, and between the two conditions with the consortium of the invention, it is lower at 45°C than at 30°C (Figure 4). This result, of lower acid consumption in the presence of the consortium, is possibly explained by the generation of acid from the dissolution of pyrite, which is greater in the presence of iron-oxidizing microorganisms. Furthermore, consumption is even lower at 45°C, possibly due to the acid generated by the precipitation of ferric ions at that temperature.

[0045] Surprisingly, the inventors have found that the consortium of the invention can withstand and bioleach at extremely acidic pH levels, down to pH 1, and even 0.8. This resistance to extreme conditions is primarily due to Suffobacterium thermosulfidooxidans. This is verified in Figure 5, where it can be seen that a culture of the Kobold B(S) DSM 35389 consortium subjected to 30°C in a bioreactor without pH control is able to generate iron-oxidizing activity, evidenced by the increase in oxidation-reduction potential (ORP) from day 7 of culture onwards, precisely when the pH of the culture falls below pH 1.0, which is extremely low.

[0046]

[0047] Table 1. Mineralogical composition of the Scavenger tailings.

[0048] Example 3. Bioleaching with the Kobold B(S) DSM 35389 consortium in columns

[0049] The inventors replicated the flask tests from Example 2, this time in bioleaching columns under laboratory conditions. The columns used can be seen in Figure 6.

[0050] To start the process, the mineral, Scavenger tailings, are first homogenized in a dry state.

[0051] Water and acid were then added to the quartz particles, followed by Scavenger glue to agglomerate them into well-formed glomerates. The criterion used to determine if the glomerate was well-formed was to add water until the mineral slightly adhered to the binder and then perform the glove test. The test was satisfactory, as when the glomerate was squeezed and compacted, it did not stick to the glove, fall apart, or leak any liquid.

[0052] Four columns were installed using Scavenger Tailings (Table 1) with an initial cobalt concentration of 1100 ppm and a nickel concentration of 519 ppm. The columns were loaded with 200 g of ore and 1000 g of support (quartz). Three of them were inoculated post-acid curing with a concentration of 1x10 7 , 5x10 7 and 1x10® microorganisms per gram of mineral, and subsequently irrigation was started and maintained at a rate of 2.5 L / hm 2 A fourth uninoculated column was set up as a control.

[0053] Irrigation was carried out with modified 9K medium ((NH^zSO, 247.5 mg / L; NaH2PO4,H2O, 36.5 mg / L; KH2PO4, 13.125 mg / L; MgSCu -7^0.25 mg / L; CaCh, 5.25 mg / L) supplemented with 1g / L of Fe 2+ , at pH 1.5.

[0054] The inoculated columns operated at 45°C, as in the flasks, obtained significantly higher cobalt recovery results than the uninoculated one, similar to what was recorded in the flasks.

[0055] The results are shown in Figures 7A and 7B for cobalt recovery and in Figures 8A and 8B for nickel recovery. In the case of cobalt, Figure 7A shows that the recovery in the columns inoculated with the consortium of the invention is much higher at 50 days compared to the uninoculated control, where a cobalt recovery of 25% is obtained, while the columns inoculated with Kobold B(S) at 45°C have a recovery of approximately 40%. The nickel recovery results are very similar to those for cobalt, as seen in Figure 8A. The recovery at 50 days in the uninoculated control is approximately 26%, while with the three cell concentrations of the Kobold B(S) consortium at 45°C, a 40% nickel recovery is obtained.

[0056] Figure 7B shows the cobalt recovery kinetics in the uninoculated C4 column and in the C1 column inoculated with Kobold B(S) over 120 days of operation. A consistent difference of approximately 10% higher recovery is observed with the method of the invention. Similarly, under the same conditions for nickel recovery, a consistent 10% higher recovery is also observed with the method of the invention (Figure 8B).

Claims

CLAIMS 1. A method for bioleaching cobaite-bearing pyrite, CHARACTERIZED in that it comprises: a. Inoculating tailings or concentrates containing cobaite-bearing pyrite with a microbiological consortium containing the KoboidB (S) DSM 35389 consortium; b. Raising the temperature of the inoculated tailings to between 30°C and 60°C; c. Adding solutions containing ferrous ion at a concentration between 0.5 and 5 g / L; d. Incubating for between 10 and 50 days in flasks and 40 to 120 days in columns; e. Recovering the bioleached solution containing cobalt and other metals in solution; wherein the process is carried out without agitation.

2. Method according to claim 1 CHARACTERIZED in that in step a) the consortium is inoculated at a concentration between 10® and 10 9 total microorganisms / g of mineral.

3. Method according to claim 1 CHARACTERIZED in that in step b) the temperature rises naturally due to the mineralogical reactions of the process.

4. Method according to claim 1 CHARACTERIZED in that step d can be carried out at a pH of between 3 and 0.

5.

5. Method according to claim 1 CHARACTERIZED in that the consortium contains Sulfobacillus thermos ulfidooxidans, Acidithiobacilius caldos and Leptospirum sp.

6. Method according to claim 1 CHARACTERIZED in that it allows the recovery of metals such as iron, nickel, cadmium and zinc.

7. Method according to claim 1 CHARACTERIZED in that the Kobold B (S) DSM 35389 consortium inoculated in step a) has been previously grown at a temperature between 30 and 60° C.

8. Method according to claim 6 CHARACTERIZED in that the consortium has been cultivated at a temperature of 45°C.

9. Method according to claim 5 CHARACTERIZED in that it accelerates the bioleaching kinetics, allowing the recovery of at least an additional 5% of metal in the same amount of time.

10. Microbiological consortium for bioleaching of tailings with cobaltiferous pyrite CHARACTERIZED in that it comprises a strain of Su / fobac / l / us thermos u / fídoox ida ns, a strain of Acidithiobacillus caldas and a strain of Leptospirillum sp., and constitutes the Kobold B(S) consortium whose deposit number is DSM 35389.

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