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glencore

At Glencore, were responsibly sourcing the commodities that advance everyday life.To fulfil our Purpose, we are always looking for the best talent to join our team. Experience this world of opportunity and take a look at our open positions.https://www.glencore.com/careers/career-opportunities?utm_source=social&utm_medium=facebook_organic&utm_campaign=5&utm_content=people_video

@josianeessabe In the Lualaba province, where our operations are located, the total population is estimated to be 2.5m people. We provide jobs to 14.5k employees and contractors. But our overall economic impact also includes our support for small businesses and agricultural cooperatives. [2/2]

@josianeessabe Hi Josiane, thanks for your questions. Next to taxes and royalties, other forms of contributions include payments we make for public infrastructure improvements. In 2020, we paid $97.8m to the DRC government for such projects. You can find all details on our website. [1/2]

Last week, we published our 2020 Payments to Governments report, detailing our economic contribution in the countries we operate. In the Democratic Republic of the Congo, we paid $424m in taxes, royalties and other payments and provided jobs for 14,500 employees and contractors https://www.glencore.com/media-and-insights/insights/2020-payments-to-governments-report?utm_source=social&utm_medium=facebook_organic&utm_campaign=4&utm_content=statement_graphic

At Glencore, we're committed to upholding our Values wherever we work to create a safe environment for our colleagues.Meet Samy and Hyacinthe - our compliance officers in the #DRC. Read more about what they enjoy most when working for us and the important role they play to uphold compliance: https://www.glencore.com/investors/reports-results/2020-annual-report/ethics-and-compliance?utm_source=social&utm_medium=facebook_organic&utm_campaign=8&utm_content=people_photo

At Glencore, were responsibly sourcing the commodities that advance everyday life.To fulfil our Purpose, we are always looking for the best talent to join our team. Experience this world of opportunity and take a look at our open positions.

Our purpose is to responsibly source the commodities that advance everyday life, and we have a clear ambition to be a #NetZero total emissions company by 2050. As we welcome Gary Nagle into his role as Glencores new CEO, hear him speak about his vision for Glencore:

My leadership style is one of inclusiveness. I want to listen, I want to hear suggestions, I want to be able to capitalise on those great ideas that come from our people. Gary NagleAt Glencore, we have an open door policy. We believe it is crucial that everyone in the business feels able to freely exchange ideas with one another, while also engaging with our external stakeholders to better understand their perspectives on a whole range of topics and issues.

Last week, we published our 2020 Payments to Governments report, detailing our economic contribution in the countries we operate.In the Democratic Republic of the Congo, we paid $424m in taxes, royalties and other payments and provided jobs for 14,500 employees and contractors.

Working with diverse stakeholders, our compliance officers are central to ensuring we operate according to our ethics and values.Read more from Samy and Hyacinthe, part of our regional compliance team in #DRC as they discuss their lives at Glencore.

I have learned more from Ivan than one can imagine from one individual. Ivans contribution is something that cant be replicated, that wont be replicated. He has led this organisation through a period of exceptional growth and navigated some considerable challenges with the support of the senior management team. Hes created this group for what it is and set it up for success for the next 40 or 50 years. Gary Nagle

@josianeessabe In the Lualaba province, where our operations are located, the total population is estimated to be 2.5m people. We provide jobs to 14.5k employees and contractors. But our overall economic impact also includes our support for small businesses and agricultural cooperatives. [2/2]

At Glencore, were responsibly sourcing the commodities that advance everyday life.To fulfil our Purpose, we are always looking for the best talent to join our team. Experience this world of opportunity and take a look at our open positions.https://www.glencore.com/careers/career-opportunities?utm_source=social&utm_medium=facebook_organic&utm_campaign=5&utm_content=people_video

copper

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comparison of three different bioleaching systems for li recovery from lepidolite | scientific reports

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Three different biological systems, the consortium of autotrophic bacteria Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, heterotrophic fungus Aspergillus niger and heterotrophic yeast Rhodotorula mucilaginosa, were investigated for lithium extraction from lepidolite. The bacterial consortium was the most effective, 11mgl1 of Li was dissolved in the absence ofnutrients within 336days. Fungal and yeast bioleaching was faster (40days), however, with lower extraction efficiency. Bioaccumulation represented a main process of Li extraction by R. mucilaginosa and A. niger, with 92 and 77% of total extracted Li accumulated in the biomass, respectively. The X-ray diffraction analysis for bioleaching residue indicated changes caused by microorganisms, however, with differences between bacterial leaching and bioleaching by fungi or yeasts. The final bioleaching yields for bacterial consortium, A. niger and R. mucilaginosa were 8.8%, 0.2% and 1.1%, respectively. Two-step bioleaching using heterotrophic organisms followed by autotrophic bioleaching could lead to the increase of the process kinetics and efficiency. Bioaccumulation of Li offers strong advantage in Li extraction from solution.

Ranking as the lightest alkaline metal, lithium is widely used in metallurgy, aerospace, ceramic, battery and fuel cell industries especially owing to its unique electrochemical reactivity and other properties as well1. The increased usage in lithium ion batteries to power portable consumer electronics and electric vehicles results in rising demand for lithium. According to several market research companies huge increase in lithium production is predicted, counting for 66% increase of global lithium production by 20252. Over the period 2021 to 2023 a rapid deficiency of Li may be expected3. Therefore, in the coming years lithium demand will rapidly increase.

In nature, lithium is present in lake brines, pegmatites and sedimentary rocks4. More than 80% of todays lithium is obtained from brines5. Since the lithium demand has significantly increased in the past years the lithium-containing ores have regained a great importance6. Therefore, developing the technology of extracting lithium from solid lithium ores will be important to meet the demand for lithium. Compared to brines the extraction of lithium from hard rock is much more difficult and involves a number of extra operations such as beneficiation to give a concentrate containing 13% Li and also roasting in sulphate or carbonate to receive Li into water-soluble species7.

One of the main industrial minerals of lithium is spodumene because it has the largest deposits over the world and it does not contain many other metals. However, the most abundant Li ore is lepidolite, a type of pegmatite, that has an ideal formula of K(Li,Al)3(SiAl)4O10(F,OH)2, and its distribution is much wider than that of lithium brine. The content of Li2O in lepidolite is relatively low ranging in 3.07.7 wt.% (containing 1.393.58% of Li) comparing with that of spodumene (68 wt.%) 8. The lithium extraction from lepidolite often incurs higher costs owing to low utilization of other metals contained in the lepidolite9. Numerous new procedures (sulfuric acid, lime, sulfate, etc.) were studied to be used for lithium recovery from lepidolite10,11. However, the use of lepidolite in hydrometallurgy is restricted by high cost of the hydrometallurgical process for lithium recovery from this mineral as it requires a high concentration of acid and complex purification processes10. Alternative technology represents utilisation of bioleaching which becomes viable owing to reduced costs, higher efficiency and green processing12. Owing to its special properties metal bioleaching has gradually replaced the hydrometallurgical methods.

Despite the various advantages of bioleaching its application on Li recovery from hard rock ores is scarce. Up to now just studies of the Rezza et al.13,14 and Reichel et al.15 were published. Rezza et al.13,14 reported the utilisation of heterotrophic microscopic fungi Penicillium purpurogenum, Aspergillus niger and yeast Rhodotorula rubra for spodumene bioleaching. They recovered 1.26, 0.75 and 1.53mg l1 of Li in nutrient rich medium and 1.06, 0.37 and 0.5mg l1 of Li in nutrient poor medium by P. purpurogenum, A. niger and yeast R. rubra, respectively. Reichel et al.15 for the first time reported the application of autotrophic bacteria for zinnwaldite bioleaching. They used un-identified, adapted mixed culture of sulphur-oxidising bacteria obtained from leaching of sulphide tailings. They reported 11% recovery of Li in batch experiments with sulphur addition and 26% Li recovery in bioreactor experiments. The first application of bioleaching to lepidolite was recorded by our group16,17,18, however, only few factors influencing the process were investigated. To conduct a comprehensive study of lithium bioextraction from lepidolite we focused on three different microbial systems, the consortium of autotrophic bacterial strains ofAcidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, heterotrophic fungus Aspergillus niger and heterotrophic yeast Rhodotorula mucilaginosa. The selected microorganisms are widespread in nature and participate inbioweathering of rocks, mobilization of metals from minerals, in metal precipitation and deposition and are widely applied in biohydrometallurgical processes. Our aim was to study and compare the kinetics of bioleaching by the three biological systems, changes in mineral structures and contribute to the understanding of mechanisms responsible for Li bioextraction from hard rock ores.

The crushed lepidolite used in this work was provided by prof. Rowson (University of Birmingham, UK). It was ground in ball mill and sieved to less than 150m with approximately 75% of particles bellow 100m. The mineralogical deposit of the ore is situated in Beauvoir (France). The composition of this mineral is shown in Table 1. Content of the lithium in lepidolite was determined by AAS as 1.21%.

The fresh culture of Aspergillus niger strain An-S (isolated from the acidified site of obov near Bansk tiavnica with a high content of exchangeable aluminium) was obtained from Department of Soil Science, Faculty of Natural Sciences in Bratislava and maintained at 4C on a solid Sabourad Dextrose Agar (HiMedia Laboratories) slant. The fungal strain is registered in the Collection of Microscopic Fungi ISB in esk Budejovice under the number 167419 Stock cultures were subcultured every month.

Pure cultures of Acidithiobacillus ferrooxidans strain SmolnikLC and A. thiooxidans strain SmolnikF were obtained from Institute of Geotechnics, Slovak Academy of Sciences in Koice and maintained at 4C in 9K and Waksman and Joffe media, respectively. Both bacteria were isolated from copper mine drainage in Smolnk region, Slovakia.

According to our previous study16 biomass received after 8-days spores cultivation was used in experiment as the age of spores or conidia of the heterotrophic fungus influenced lithium dissolution from the mineral and a higher Li bioleaching efficiency was achieved using long-term cultured fungi.

The experiments were carried out in 250ml Erlenmeyer flasks containing 200ml of standard liquid bioleaching media composed of glucose5g l1 and (NH4)2SO40.5g l1 with the initial pH value of 5.1 adjusted using 10M H2SO4. To each bioleaching media 2g crushed mineral and 5ml of 8-day old conidia (biomass), were added. The flasks were sealed with removable cotton and the experiment was carried out at 21C statically. Prior to leaching the medium and mineral were sterilized by autoclaving for 20min at 120C. At pre-determined intervals (4, 11, 18, 25, 33 and 41day) 5ml of media were collected by disposable sterile pipettes and filtered through the 0.45m-pore-size membrane filter. At the end of the experiments the biomass was easily removed by tweezers and washed with deionised water. The bioleaching residue was obtained after the filtering the rest of the medium and washed with deionised water. The biomass and residue samples were air-dried for 24h and consequently mineralised in oven for 4h at 500C. Thereafter, the biomass was digested by the 2M HCl to determine lithium accumulated in the biomass. The amount of biomass was calculated per 1l of media. To calculate Li recovery efficiency Li concentration was analysed in filtrate, in the biomass and bioleaching residue. Each treatment was prepared in duplicate (two flasks for each pre-determined withdrawal time were prepared). Control experiments with the same media just without microorganisms addition were carried out simultaneously.

The experiments were conducted in 250ml Erlenmeyer flasks containing 190ml of nutrient rich or poor medium. Composition of nutrient medium for bacterial consortium was adapted from basic media for individual acidithiobacilli and consist of KH2PO40.1g, (NH4)2SO42g, KCl0.1g, MgSO4.7H2O4g, FeSO4.7H2O44.2g and elemental sulphur 4g in 1,000ml of deionised water. The poor medium was prepared just as a solution of H2SO4 with pH 3 and elemental sulphur 5g l1. Medium pH prior bacteria addition was adjusted to 3 by 10M H2SO4. 10ml of adapted bacterial consortium was added. After pH dropped to 1.5 due to production of sulphuric acid, crushed lepidolite was added in concentration 10g l1. Control experiments with the same medium but without microorganisms were set up. All culture and control flasks were incubated at 30C, statically. All experiments were carried out in duplicate. At regular intervals (day 1, 3, 7, 10, 14, 21, 49, 77, 171, 205 and 366) samples were withdrawn using 0.2m-pore-size membrane filters and supernatant was analysed for Li content using AAS. At the end of the experiments the bioleaching residue was obtained after the filtering the rest of the medium and washed with deionised water. The residue samples were air-dried for 24h and analysed for Li content by AAS.

Adaptation of bacteria to lepidolite was carried out prior bioleaching experiments and it lasted for two months. Bacteria were cultivated in 180ml of nutrient medium with addition of 10ml of pure culture of A. ferrooxidans and 10ml of A. thiooxidans pure culture and 10g l1 of lepidolite.

The experiments were carried out in 250ml Erlenmeyer flasks containing 200ml of bioleaching media, yeast cells pre-cultivated 5days in Petri dish prior the experiments and 10g l1 of crushed ore. Two types of media, rich and poor, were used for experiments. Composition of rich medium was in 1,000ml deionised waterglucose20g, KH2PO45g, (NH4)2SO45g, MgSO40.34g and yeast extract 7g. Poor medium consist of glucose5g and (NH4)2SO40.5g in 1,000ml of deionised water. The medium pH was adjusted to 5.1 by 10M H2SO4 and sterilized by autoclaving for 20min at 120C before biomass was added. Flasks were placed in shaker at 160rpm. At pre-defined intervals (days 6, 13, 20, 27, 34, 42, 52 and 59) the samples were collected using micropipettes and centrifuged at 4,500g for 5min. Li concentration was analysed in supernatant by AAS. Experiments were carried out at 21C, statically. All were conducted in duplicate. Control bioleaching was conducted at the same way without yeast addition.

At the end of the experiments, remaining supernatant with cells was collected by pipette and centrifuged at 4,500g for 10min to obtain a biomass. The bioleaching residue was obtained after the filtering the rest of the medium and washed with deionised water. The biomass and residue samples were air-dried for 24h and consequently mineralised in oven for 4h at 500C. Thereafter, the biomass was digested by the 2M HCl to determine lithium accumulated in the biomass. The amount of biomass was calculated per 1l of media. To calculate Li recovery efficiency Li concentration was analysed in filtrate, in the biomass and bioleaching residue.

Solution pH was measured using a GRYF 208L pH meter with a combined electrode. Li concentration in aqueous samples was measured by Atomic Absorption Spectrophotometer (Perkin Elmer 3,100) at 670nm. The initial sample and final leaching residues were also mounted with silver paste on aluminium stubs, then coated with 300 400 A Au/Pd in a sputtering unit and finally examined in a JEOL scanning electron microscope (JEOL JSM-35CE). Mineral composition before and after the bioleaching process was determined by a diffractometer Bruker D2 Phaser (Bruker AXS, GmbH, Germany) in BraggBrentano geometry (configuration Theta-2Theta), CuK radiation.

Comparison of Li bioleaching by three various types of organisms (Fig.1) revealed that the leaching kinetics in systems with yeast R. mucilaginosa was the fastest. Presence of Li in solution was detected at 6th day of the process. After initial faster bioleaching within first 6days (285.5g l1), there was a gradual decrease of Li concentration in solution due to Li bioaccumulation into the biomass up to 13th day and later stable Li concentration in range of 240250g l1 was observed suggesting that the rate of bioleaching and bioaccumulation were equal.

Kinetics of Li bioleaching from lepidolite by consortium of A. ferrooxidans and A. thiooxidans (bacteria), A. niger (fungi) and R. mucilaginosa (yeast) (A), long-term kinetics of Li bioleaching by bacteria (B) (fungi: initial ore concentration 10g l1, t=21C, pH=5.1, statically, standard medium, yeast: 10g l1, t=21C, pH=5.1, shaking 160rpm, rich medium and bacteria: 10g l1, t=30C, pH=1.5, statically, poor medium).

The lowest amount of Li was bioleached by fungi A. niger. Under this bioleaching conditions Li was for the first time observed in solution after 26days of the process. Its concentration gradually increased later on. Again bioaccumulation was observed affecting the amount of Li in the solution.

In the case of bacteria, medium composition was the most important for Li bioleaching. In nutrient rich medium for acidophilic chemoautotrophic acidithiobacilli which contained energy sources (Fe2+ ions and S0) no Li bioleaching was observed during the whole process time. However, in the medium with limited amount of nutrients and energy sources containing just sulphuric acid and elemental sulphur, Li+ ions presence was observed at 21st day for the first time. Bacteria were probably forced to utilize nutrients necessary for their life directly in the leached material. During the first 77days the lithium bioleaching kinetics was very slow but this stage was followed by the sharp increase of bioleaching rate (400 times increase of the bioleaching rate was observed) resulting in 11mg l1 of solubilised Li at the end of the bioleaching experiments (after 336days). The rapid change in the bioleaching rate might be attributed to the changes of mineral structure due to bacterial activity. No Li was found in control experiments using the media without microorganisms addition.

To kinetically interpret the heterogeneous non-catalytic reaction for lepidolite bioleaching the shrinking core model (SCM) was used. The assumptions to use the model are based on the three facts(i) mixed lepidolite particles are considered as nonporous particles, (ii) ore grains gradually shrank and (iii) the product layers form around the unreacted grains20. The development and verification of the model were previously described in details by several authors20,21.

Experimental data obtained for all three studied bioleaching systems were substituted into both equations of SCM model. In the case of bacterial bioleaching a plot of 1(1X)1/3 versus time (Fig.2) was found a straight line suggesting that chemical reaction and outer diffusion are the rate controlling steps of the process of bacterial bioleaching. Changes of rate constant, kr, (apparent from slopes of the plots) can be visible, as well. The linear relationship was obtained in the initial stage of bioleaching (R2=0.9944) and later at the day 77 the rate of the process changed but still showed the good fitting obtained by plotting 1(1X)1/3 versus time (R2=0.9991). This changes are very well visible also in the previous Fig.1 showing the increase of Li+ ion concentration within the experimental period.

However, the SCM model did not fit to the bioleaching data of two other bioleaching systems, using fungi and yeasts. Obviously, parallel bioaccumulation of Li+ ions into the biomass was responsible for considerably different bioleaching behaviour.

Conditions of bioleaching experiments (pH, medium composition) were adjusted according the type of the microorganism used. Independently of conditions, the decrease of pH (Fig.3) was recorded in all three bioleaching system. The most obvious decrease in pH occurred in bioleaching by microscopic fungi A. niger, with a pH decrease from 5.1 to 3 within first 12days, followed by slow decrease to 2.5 until the end of the experiment. According to various authors22,23, it can be suggested that organic acids, considered the main fungal bioleaching agents, were produced. In the control medium a small increase in pH (from 5.2 to 5.6) was observed.

Changes of pH during bioleaching of lepidolite by consortium of A. ferrooxidans and A. thiooxidans (bacteria), A. niger (fungi) and R. mucilaginosa (yeast) (fungi: initial ore concentration 10g l1, t=21C, pH=5.1, statically, standard medium, yeast: 10g l1, t=21C, pH=5.1, shaking 160rpm, rich medium and bacteria: 10g l1, t=30C, pH=1.5, statically, poor medium).

A similar pattern was also observed in bacterial bioleaching, in which fast decrease of pH to 1.2 was observed during first 7days followed by slow decrease to 0.9. Later the pH was stable in range of 0.91.2. Probably bacteria A. thiooxidans were mainly responsible for such pH decrease. In the control without bacteria addition the pH initially decreased from 1.5 to 1.3 and later increased and remained at 1.5.

As shown in Fig.3 fast pH decrease was observed during first 6days of bioleaching with yeast R. mucilaginosa from initial 5.1 to 4.1. Later pH did not change until 20th day followed by slow decrease to 3.5 at 30th day. In control media, without microorganisms, pH value slowly increased from initial 5.1 to final 5.5.

According to obtained results different mechanisms can be suggested for lepidolite bioleaching by biological systems studied. Mechanisms of Li bioleaching from lepidolite by A. niger fungus may be attributed to combination of biochemical (due to organic acids production) and biomechanical (due to hyphae penetration) leaching mechanisms. Significant drop of pH values indicates increased concentration of organic acids in the media as the result of high metabolic activity of the A. niger cell what was confirmed by various authors studying bioleaching by the microscopic fungi14,22,23,24,25. However, lepidolite interpenetration by A. niger hyphae growing along cleavages was observed by SEM analysis of solid residue after bioleaching, as well (Supplementary Information, Fig. S1), suggesting that direct biomechanical deterioration of lepidolite was alsoa part of the whole lithium extraction mechanism. However, according to Gadd26 the biochemical activities of microorganisms play more significant role than mechanical degradation.

Mechanisms of lepidolite bioleaching by bacteria is unknown. However, from abovementioned results it is obvious that no other substance except H+ ions contributed to the dissolution of Li+ ions. These results suggested that Li in lepidolite was dissolved by acid. Probably the mechanisms suggested by Liu et al.20 for leaching of lepidolite in sulphuric acid may be applied to bioleaching by acidophilic bacteria with sulphuric acid as a main bioleaching agent, as well. The main reaction of mixed alkali metal bioleaching may be expressed as follows:

where M presents alkali metals. Metallic elements from lepidolite are dissolved to form metal sulphates and mixed alums in the solution resulting just in partial lepidolite dissolution20. Overal reaction of lepidolite bioleaching in sulphuric acid produced by bacteria may be adopted from Onalbaeva et al.11:

XRD analysis was applied in this study for phase identification and structural changes evaluation of samples before and after bioleaching in all three studied systems. Significant differences in mineralogical composition of leaching residue among the three studied bioleaching systems are visible from XRD spectra comparison (Supplementary Information, Fig. S2) suggesting that different mechanisms can be responsible for bioleaching. While bacterial bioleaching led to the disappearing of muscovite phase from XRD spectrum, the fungal bioleaching led to the appearance of new silicate phase (SiO2) and muscovite was found a dominant phase. According to Liu et al.20 presence of quartz in the spectrum at the end of the process may correspond withalkali metal dissolution from the silicate lattice. Phase changes were observed also after bioleaching by yeast R. mucilaginosa. Reallocation and significant decrease of diffraction peaks intensity was observed and similarly as in case of microscopic fungi muscovite has become a dominant phase while polylithionite phase significantly weakened. Based on the results, it can be suggested that the bioleaching mechanisms of lepidolite by fungi and yeast may be similar, however, in the case of bacteria the mechanisms might be significantly different. Further experiments are necessary to understand the mechanisms behind the lepidolite bioleaching.

Bioaccumulation of lithium into the biomass was observed when heterotrophic microorganisms A. niger and R. mucilaginosa were used (Fig.4A). No bioaccumulation was found when bioleaching by consortium of acidophilic bacteria was studied. It can be suggested that the process of Li recovery by A. niger and R. mucilaginosa is a combination of two basic processes initial bioleaching (metal solubilisation) followed by rapid bioaccumulation (intracellular lithium accumulation). It is possible that lithium bioaccumulation could significantly contribute to its solubilisation as released Li+ cations were fast accumulated in the cells and thus pulled the equilibrium resulting in the increased efficiency of the Li dissolution.

Distribution of Li between solution and biomass during bioleaching of lepidolite (A) and efficiency of the lepidolite bioleaching (B) by consortium of A. ferrooxidans and A. thiooxidans (bacteria), A. niger (fungi) and R. mucilaginosa (yeast) (fungi: initial ore concentration 10g l1, t=21C, pH=5.1, statically, standard medium, yeast: 10g l1, t=21C, pH=5.1, shaking 160rpm, rich medium and bacteria: 10g l1, t=30C, pH=1.5, statically, poor medium).

The highest amount of lithium was accumulated by R. mucilaginosa cells, representing 92% of the total amount of Li recovered from the ore. In the case of microscopic fungi A. niger, produced biomass accumulated 77% of the total solubilised Li. Distribution of Li between solution and biomass of particular microorganisms is shown in Fig.4A. It is obvious that in both cases (fungi and yeast) bioaccumulation is dominant process of Li recovery and just small amount of Li+ ions remain in solution.

The bioleaching efficiency is given as asum of two processes Li dissolution and its accumulation in the biomass. The final bioleaching yields for consortium of A. ferrooxidans and A. thiooxidans, fungi A. niger and R. mucilaginosa were found to be 8.8%, 0.2% and 1.1%, respectively. The results suggested that the most efficient among all three studied systems was the consortium of acidophilic bacteria A. ferrooxidans and A. thiooxidans (Fig.4B) with the final bioleaching yield of almost 9%. On the other hand, very long time (336days) was necessary for the process. Reichel et al.15 found 11% Li recovery from zinnwaldite using consortium of sulphur-oxidising bacteria, however, authors reported just 14days for observed Li bioleaching efficiency although they do not found clear explanation of higher bioleaching efficiency in comparison with chemical leaching.

The lowest bioleaching yield was observed when A. niger was used. Rezza et al.13,14 used A. niger for Li bioleaching from spodumene with highest recovery of 0.75mg l1 of lithium, they do not reported any bioaccumulation.

Composition of medium had very strong effect on bioleaching efficiency by R. mucilaginosa as in nutrient rich medium due to significantly higher biomass production majority of Li has accumulated into the biomass resulting in 3 times higher final Li recovery. There were also morphological differences observed between yeasts cultivated in nutrient rich and poor environments with spherical shape and thin exopolymer layer of 0.48m for yeast from nutrient rich media in comparison with oval cells and thick exopolymer layer (1.8m) when cultivated in nutrient poor medium17.

Despite of quite low bioleaching efficiency there is clearly visible potential of all three biological systems for Li recovery from hard rocks. Even with low Li concentration in solution after bioleaching, the lithium concentration in the leaching solution resembles the lithium concentration of sea water (0.10.2mg l1) and brines (0.12g l1) considered for economic recovery28,29. That shows that the leaching solution is generally suitable for further processing15.

Due to the expensive separation of Li from leaching liquor, the conventional processing routes are likely not economic. However, ability of fungus A. niger and especially yeast R. mucilaginosa represent advantageous route of Li recovery after bioleaching. Thermal, chemical or microbiological process can be used to Li extraction from the biomass later on.

Metabolic activity and hyphae penetration of microscopic fungi and yeasts resulted in significant structural changes of mineral enhancing the access of lithium by bioleaching agent. Maybe the combination of heterotrophic microorganisms (microscopic fungi or yeast) bioleaching leading to mineral structure changes with consequent bacterial bioleaching could bring better results in the future.

The study describes the bioleaching of lithium from lepidolite using three different biological systemsacidophilic bacteria, microscopic fungus and yeasts. The results indicate that the presence of microorganisms was beneficial for Li bioleaching from lepidolite because no Li was found in abiotic controls. The lithium extraction was the highest using bacteria, however very long time was necessary for the process. The mechanisms of bioleaching by fungi and yeast differs from bacterial bioleaching. Significant deterioration of the mineral surface and structure were observed during fungal and yeast bioleaching after short time so probably the combination of two, heterotrophic followed by autotrophic processes would result in shortening of the time necessary for the process as well as increase of the bioleaching efficiency. Strong ability to accumulate Li represent the advantage of fungi and yeast exploitation for Li recovery from leachate. Thermal, chemical or microbiological process can be used to Li extraction from the biomass later on. The effect of medium composition was visibleto force bacteria to increase the rate and efficiency of bioleaching poor medium was suitable, however when bioaccumulation was the main aim, rich medium resulting in high biomass production was more advantageous.

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The authors would like to thank Dr. N. Rowson from University of Birmingham for the supply of the lepidolite used in this work. The work was fully supported by a grant from the Slovak National Grant Agency under the VEGA Project 1/0229/17 and APVV SK-PL-18-0012.

J.S-K., A.L. and R.M. designed the study, R.M. conducted experiments, M.V. and M.F. carried out the X-ray and SEM analyses and analysed the data, J.S-K., R.M. and P.P. interpreted the experimental data, J.S-K. wrote the manuscript, all authors reviewed the manuscript.

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Sedlakova-Kadukova, J., Marcincakova, R., Luptakova, A. et al. Comparison of three different bioleaching systems for Li recovery from lepidolite. Sci Rep 10, 14594 (2020). https://doi.org/10.1038/s41598-020-71596-5