Extraction Of Lanthanides Research Articles

Application of diglycolamide extractant in rare-earth extraction

Diglycolamide (DGA) extractant is a kind of rare-earth extractant with promising applications that has the advantages of high extraction capacity, ease of synthesis, good thermal stability and good radiation stability. It is a green extractant that contains only four elements, C, H, O and N, and produces no residue after incineration. The properties of DGAs containing branched N,N′-alkyl substituents have been much studied in recent years, and it has been shown that branched side chains lead to better separation. The introduction of structurally rigid elements in DGA provides new possibilities for separation of rare earth elements (REEs). Owing to the tiny differences in the chemical properties of adjacent REES, the simple use of DGA extractant cannot meet all separation requirements, and a masking agent is added to the aqueous phase to improve the separation by coextraction to meet the requirements of different processes. This review presents the structural analysis of the complexes and crystals of diglycolamide extractants with rare-earth ions through different characterization means, and the effects of different structural extractants, solvents, nitric acid and phase modifiers on extraction behavior are reviewed. This review pays special attention to the effect of the side chain structure of diglycolamide on extraction behavior, which provides a theoretical basis and guiding direction for the field of separation of the REEs by diglycolamide extractants.

Establishing forward mixing model to mass transfer overview in multi-impeller agitated column for rare Earth extraction process

The current study develops comprehensive mass transfer models to optimize the rare earth extraction. A plug flow, axial dispersion, backflow, forward mixing-based mass transfer model was created and solved numerically using the fitting technique. The investigated process is a multi-impeller agitated column designed to provide proper contact between organic and aqueous phases to extract rare-earth ions. Taking Sm(III)–Gd(III) separation as an application case, extraction efficiency in the agitation speed of 200 rpm was obtained equal to 95.14%, 76.67% by this column for Gd(III), and Sm(III) ions, respectively. The model's findings were compared with experimental data, and a significant agreement was achieved with the forward mixing model. The results indicated that the high agitation speed is beneficial to increasing the interfacial area while reducing the mass-transfer coefficient. On the contrary, the circulation within the larger droplet improves the transfer of mass, albeit at the expense of reducing the interfacial area. The results showed that the drop size distribution is a crucial factor as the droplet sizes significantly affect the droplet mass transfer. The mathematical models’ values of Ec for mass transfer parameters showed that the operational variables significantly affect the mass transfer rate and can cause deviations from the ideal flow path. A reasonable and appropriate estimation of the organic-side volumetric overall mass transfer coefficient was provided, which can be applied to this contactor’s design and scale-up.

Extraction of Rare Earth Elements from Chloride Solutions Using Mixtures of P507 and Cyanex 272

In this study, the extraction of rare earth elements (REEs) from chloride solutions after leaching REE carbonate concentrate with solutions of the mixtures of P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) and Cyanex 272 (bis(2,4,4-trimethylpentyl)phosphinic acid) (1:1) at various concentrations was experimentally studied. It was shown that the distribution ratios of all REEs decrease with the increasing concentration of these metals in the initial solution, which is associated with the loading of the organic phase. The most significant improvement in the extraction is observed for the heavy group of rare earth elements. The extractability of REEs increases with the increasing atomic number of the element, as is typical for the extraction of these metals with acidic organophosphorus extractants. The data obtained show that the separation factors of adjacent rare earth elements decrease slightly with the increasing concentration of metals in the initial aqueous solution. Increasing the concentration of the extractant mixture does not have a significant effect on the values of the adjacent REE separation factors. The data obtained on the distribution ratios and separation factors made it possible to propose a flow sheet for the separation of rare earth elements with the production of Y, Ho, Tb and Dy.

Rapid and efficient extraction of cerium by forming Al-Ce alloys in LiCl-KCl molten salts

The extraction of lanthanides in spent fuel reprocessing plays a key role in the development of nuclear energy. In this work, the extraction of the typical fissionable cerium elements has been studied by electrolytic co-reduction of Al(III) and Ce(III) in LiCl-KCl-CeCl3 molten salts assisted by KAlCl4. The electrochemical behavior of the reduction of Al(III) and Ce(III) on a molybdenum electrode was studied by cyclic voltammetry (CV), square wave voltammetry (SWV), and open circuit chronopotentiometry (OCP), and specific peaks of five Al-Ce intermetallic compounds were detected. After 2.7 h of galvanostatic electrolysis at a current density of 0.064 A cm-2, the extraction efficiency and current efficiency of Ce(III) reached 99.9 % and 91.3 % respectively. Potentiostatic electrolysis is slightly more efficient, with 99.9 % Ce(III) extraction in 3.5 h at a current efficiency of 97.8 %. The products of electrolysis are rod-shaped alloys (Al11Ce3, Al3Ce, Al2Ce), and the molten salts purified by electrolytic separation are free of impurity signals and can be reused for electrolytic refining.

Rationally designed nanotrap structures for efficient separation of rare earth elements over a single step

Extracting rare earth elements (REEs) from wastewater is essential for the growth and an eco-friendly sustainable economy. However, it is a daunting challenge to separate individual rare earth elements by their subtle differences. To overcome this difficulty, we report a unique REE nanotrap that features dense uncoordinated carboxyl groups and triazole N atoms in a two-fold interpenetrated metal-organic framework (named NCU-1). Notably, the synergistic effect of suitable pore sizes and REE nanotraps in NCU-1 is highly responsive to the size variation of rare-earth ions and shows high selectivity toward light REE. As a proof of concept, Pr/Lu and Nd/Er are used as binary models, which give a high separation factor of SFPr/Lu = 796 and SFNd/Er = 273, demonstrating highly efficient separation over a single step. This ability achieves efficient and selective extraction and separation of REEs from mine tailings, establishing this platform as an important advance for sustainable obtaining high-purity REEs.

Adsorption using Selective Adsorbents as An Effective Method for Rare Earth Elements Recovery–a Review

Rare Earth Elements (REEs) are strategically important for the industry, especially in the manufacture of high-technology products and components, such as electric batteries for energy storage, energy conversion, defense and security industry, electric vehicles, components on smartphones, laptops, liquid crystal display, and others. Generally, REEs are processed by liquid-liquid extraction. However, this process is very costly due to the use of chemicals and high operational costs, so the waste has the potential to pollute the environment. Currently, innovative separation/recovery techniques are continuously being developed for effective and environmentally friendly extraction of rare earths. The adsorption method using the optimal adsorbent is one of the most efficient methods for recovering REEs at low concentrations. This method offers several advantages, including high release effectiveness, ease of installation and operation, low maintenance costs, and reduced chemical consumption. This study reviews the mechanism, characterization, and several adsorbents from natural to synthetic materials, especially nanocomposite-based adsorbents for the recovery of rare earths. In addition, the discussion of several parameters that affect the adsorbent. However, the results of several methodological breakthroughs that have been carried out show how much further research is needed

A novel bifunctional ionic liquid [N1888][OOB] for the separation of rare earth and transition metal in NdFeB magnet

In this paper, a series of novel bifunctional ionic liquids with methyltrioctylammonium as the cation and o-alkoxybenzoic acetate as the anion were synthesized. Their extraction properties were investigated for the separation of rare earth and transition metal for NdFeB waste recycling. It was found that [methyltrioctyl ammonium][o-octyloxybenzoic acetate] ([N1888][OOB]) could preferentially extract rare earth while the extraction abilities of Fe and Co were weak. The extraction mechanism of rare earth with [N1888][OOB] was indicated to be ion association in a molar ratio of 2:1. The rare earth loaded by [N1888][OOB] could be selectively stripped with water. Based on the above research results, a novel separation process was developed to separate rare earth, Fe and Co with [N1888][OOB]. This study intensified the separation process of rare earth and transition metals. The novel separation strategy based on [N1888][OOB] has revealed the advantages of efficiency and sustainability for rare earth recovery.

Prospecting for rare earth element (hyper)accumulators in the Paris Herbarium using X-ray fluorescence spectroscopy reveals new distributional and taxon discoveries.

Rare earth elements (REEs) are increasingly crucial for modern technologies. Plants could be used as a biogeochemical pathfinder and a tool to extract REEs from deposits. However, a paucity of information on suitable plants for these tasks exists. We aimed to discover new REE-(hyper)accumulating plant species by performing an X-ray fluorescence (XRF) survey at the Herbarium of the Muséum national d'Histoire naturelle (MNHN, Paris, France). We selected specific families based on the likelihood of containing REE-hyperaccumulating species, using known taxa that accumulate REEs. A total of 4425 specimens, taken in the two main evolutionary lineages of extant vascular plants, were analysed, including the two fern families Blechnaceae (n = 561) and Gleicheniaceae (n = 1310), and the two flowering plant families Phytolaccaceae (n = 1137) and Juglandaceae (n = 1417). Yttrium (Y) was used as a proxy for REEs for methodological reasons, and a total of 268 specimens belonging to the genera Blechnopsis (n = 149), Dicranopteris (n = 75), Gleichenella (n = 32), Phytolacca (n = 6), Carya (n = 4), Juglans (n = 1) and Sticherus (n = 1) were identified with Y concentrations ranging from the limit of detection (LOD) >49 µg g-1 up to 1424 µg g-1. Subsequently, analysis of fragments of selected specimens by inductively coupled plasma atomic emission spectroscopy (ICP-AES) revealed that this translated to up to 6423 µg total REEs g-1 in Dicranopteris linearis and up to 4278 µg total REEs g-1 in Blechnopsis orientalis which are among the highest values ever recorded for REE hyperaccumulation in plants. It also proved the validity of Y as an indicator for REEs in XRF analysis of herbarium specimens. The presence of manganese (Mn) and zinc (Zn) was also studied by XRF in the selected specimens. Mn was detected in 1440 specimens ranging from the detection limit at 116 µg g-1 up to 3807 µg g-1 whilst Zn was detected in 345 specimens ranging from the detection limit at 77 µg g-1 up to 938 µg g-1. This study led to the discovery of REE accumulation in a range of plant species, substantially higher concentrations in species known to be REE hyperaccumulators, and records of REE hyperaccumulators outside of the well-studied populations in China.

Understanding the Complexation Behavior of Carbamoylphosphine Oxide Ligands with Representative f-Block Elements.

The complexation behavior of carbamoylmethylphosphine oxide ligands (CMPO), a bifunctional phosphine oxide, and their substituted derivatives with Ce(III), Eu(III), Th(IV), U(VI), and Am(III) was probed at the density functional theory (DFT) level. The enhanced extraction of trivalent rare earth elements by the 2-diphenylphosphinylethyl derivative over the conventional CMPO ligand is identified due to the availability of an additional P═O donor group in the former. In addition, the orbital and dispersive interactions play a vital role in the preference of Th(IV) over U(VI) during extraction using CMPO ligands. The better complexing ability of ligands having long alkyl chain substituents at the P atom is justified due to the observed enhanced dispersion interactions in these systems.

Recovery of Rare Earth Elements from Acid Mine Drainage with Supported Liquid Membranes: Impacts of Feedstock Composition for Extraction Performance.

Acid mine drainage (AMD) from inactive coal mines can be enriched in rare earth elements (REEs) and has gained much attention as an alternative source for these technology-critical metals. However, AMD is a relatively low-grade REE resource in which the abundance of impurities and the composition variability of the feedstock create major uncertainties for the performance of REE extraction technologies. This study sought to identify AMD feedstock variables that influence the extraction efficiency of REEs by supported liquid membranes (SLMs). SLM separation is a process involving a hydrophobic membrane embedded with an extracting solvent that facilitates the selective extraction of REE ions. The major aims were to (1) assess the effectiveness of SLM-based REE separation from several AMD samples representing a spectrum of aqueous composition, (2) determine the effects of AMD storage and holding time on extraction performance, and (3) assess the impact of AMD pretreatment (e.g., filtration and pH adjustment) on REE recovery. The results showed that relative extraction fluxes of REE correlated with AMD characteristics such as pH and major ions such as Fe, Ca, and Mn. The purity of the acid strippant product, expressed as the REE dry weight content, depended on the initial REE concentrations in the AMD source rather than the flux of individual REEs across the membrane. For AMD samples stored for 3 months prior to extraction, REE recovery by SLM separations was substantially decreased if oxidation of Fe(II) to Fe(III) was observed during sample storage. Pretreatment of AMD feedstocks by pH adjustment did not substantially improve the separation performance. Overall, this study establishes primary water quality parameters of AMD that influence the SLM separation flux and product purity. Such insights contribute to a mechanistic understanding of critical metals extractions by SLM for complex and nontraditional feedstocks such as AMD wastes.

Influence of Clay Particle Interactions on Leaching Percolation in Ion-adsorption-type Rare Earth Ores

Ion-adsorption-type rare earth ores (IRE-ores) are a vital source of rare earth elements globally. The percolation properties of the ore body significantly determine the ease of rare earth extraction using in situ leaching processes. This paper investigates the interactions among clay particles in ion-adsorption-type rare earth ores within aqueous solutions, utilizing methods such as mineral particle aggregation and settling and acid–base adsorption on mineral surfaces. Based on these analyses, this paper elucidates the influence of solution properties on the percolation process of ion-type rare earth ores during leaching. The results indicate that the electrostatic attraction between minerals in aqueous solutions is pronounced, enhancing the interaction and resulting in a notable instability of the aggregates. The aggregation of minerals impacts the viscous effect of water bound to the mineral surface on the solution, thereby affecting the percolation rate. Extremely low concentrations of SO42− and CH3COO− can act as surface modifiers, reducing the electrostatic attraction between particles and consequently increasing the leaching percolation rate.

Staged magnetic concentration of complex rare earth ores containing niobium and zirconium

ABSTRACT The Balzhe rare earth deposit, located in Inner Mongolia, China, is a complex deposit that also contains niobium and zirconium. However, it remains undeveloped. One notable challenge is the low grades of the main valuable minerals, including xinganite, zircon, niobite, ilmenorutile, pyrochlorite, eschynite, monazite, and bastnaesite. These minerals are either weakly magnetic or associated with ilmenite, a paramagnetic mineral. To overcome this, a high-intensity magnetic method can be employed to separate these valuable minerals from the gangue minerals, thereby generating enriched products to lower the cost of the following flotation. In this study, the first step involved utilizing a high-intensity magnetic separation to enrich particles in different size fractions. It was observed that the size fraction of −0.5 + 0.02 mm was particularly suitable for effective separation. Subsequently, staged magnetic pre-concentration was conducted to obtain products with varying specific magnetization coefficients. To optimize the applied magnetic field intensity, a combination of a high-intensity magnetic separator and a superconducting magnetic separator was employed at different magnetic induction intensities. This proposed technique not only reduces reagent costs but also enhances the operational efficiency of subsequent flotation processes. By implementing this approach, it is anticipated that the Balzhe rare earth deposit can be effectively processed, overcoming the challenge of low-grade valuable minerals. This would contribute to improved economic viability and operational efficiency in the extraction of rare earth elements, niobium, and zirconium from the deposit.

Synergistic extraction of rare earth elements and alumina from coal fly ash by potassium pyrosulfate

Although coal fly ash (CFA) contains a high content of rare earth elements (REEs), the related extraction methods have limitations because of their low efficiencies, high levels of energy consumption, and other drawbacks. To address these problems, in this study, we examined the coextraction of REEs and Al2O3 from two types of Al2O3-rich CFA, pulverized CFA (PCFA) and circulating fluidized bed fly ash (CFBFA) using low-temperature calcination in the presence of K2S2O7. The total REEs, heavy REEs (HREEs), and light REEs (LREEs) extraction efficiencies were determined using different K2S2O7/Al2O3 molar ratios and calcination temperatures and correlated with the Al2O3 extraction efficiency using Pearson correlation coefficient analysis. The REEs are concentrated within CFA particles encapsulated in an aluminosilicate glass phase, and the REEs extraction efficiency is related to the form of Al in CFA. The extraction efficiencies of Al2O3 and REEs increase as the K2S2O7/Al2O3 molar ratio and calcination temperature increase, and the extraction selectivity of the more industrially valuable HREEs from CFBFA is higher. At high K2S2O7/Al2O3 molar ratios, the extraction of REEs from PCFA is more efficient than that from CFBFA with the regeneration of the highly active Al–O–Si bonds in CFBFA. The Al2O3 extraction efficiencies of PCFA as well as CFBFA correlate strongly with the total REEs, HREEs, and LREEs extraction efficiencies. The developed extraction technology has the potential to promote CFA valorization and expand REEs resources, thus mitigating the bottlenecks of REEs procurement.

Selective extraction of rare earth elements and cobalt from iron residue containing rare earth using mechanical activation and reductive leaching method

NdFeB waste is an important rare earth secondary resource, which is usually treated by hydrochloric acid preferential method in traditional industrial process. Herein, leaching residue containing about 0.5–1 % rare earth elements (REEs) and a small amount of cobalt is generated as a by-product in the process. The leaching residue is mainly composed of iron oxide and generally sold to steelmaking plants, resulting in the waste of REEs and cobalt resource. An efficient recycling process is proposed for selectively extracting REEs and cobalt from the iron residue containing rare earth by mechanical activation and reductive leaching method based on mineral liberation analysis (MLA) and thermodynamic analysis. By analyzing the composition of the raw materials, magnetite and limonite are in an encapsulated state with rare earth minerals. REEs and cobalt are mainly present in the rare earth aluminate phase. To achieve deep extraction of REEs and cobalt, the first step is to change the insoluble phase of iron residue by mechanical activation method. During this process, the crystal structures of Fe2O3 and Fe3O4 in the iron residue containing rare earth are disrupted and transformed into amorphous states. During the reductive leaching process, part of the iron is converted into divalent. The iron in the leaching solution can be removed by hematite method and achieved phase reconstruction. Thus, REEs and cobalt can be extracted selectively from leaching residue of NdFeB waste.

THE RARE EARTH ELEMENTS: AN IN-DEPTH EXPLORATION OF INDUSTRIAL UTILIZATION, RECYCLING POTENTIAL AND ENVIRONMENTAL RAMIFICATIONS

This comprehensive study delves into the extensive spectrum of applications attributed to rare earth elements (REEs), their potential for effective recycling, and the intricate environmental considerations entwined with their extraction and utilization. The realm of rare earth elements is undergoing rapid transformations fueled by technological progress and the escalating demand for these essential components. The spectrum of REEs encompasses the lanthanide series elements, namely La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, as well as Sc and Y. These metals currently hold utmost significance across a multitude of contemporary technologies, spanning from smartphones, televisions, LED light bulbs, to wind turbines. This paper concisely outlines the environmental perils encompassing human health that stem from REE mining practices and the large-scale disposal of electronic waste containing noteworthy concentrations of REEs. Within these pages, we encapsulate novel strategies aimed at ensuring the future availability of REEs, including recent advancements in REE extraction from Coal Field Ash and innovative e-waste recycling methodologies. Additionally, we spotlight recent breakthroughs in the domain of individual REE separation techniques, encompassing both metallurgical and recycling operations.

Full recycling of MgCl2 wastewater generated in rare earth extraction and separation process by spray pyrolysis

Wastewater recycling is the desired goal of the rare earth separation plants for current ecological requirements and economic benefit. The MgCl2 wastewater generated during rare earth extraction and separation process was treated by spray pyrolysis for the first time to achieve full recycling. The kinetic of spray pyrolysis process and the mechanism affecting the activity of MgO powder were investigated. The results showed that the rate determining step of MgCl2 solution spray pyrolysis was transformed from a chemical reaction control to a diffusion process control after the temperature exceeded 1073 K. The MgO powder prepared by spray pyrolysis was rough and porous, the embedding of Cl made MgO grains severely distorted, producing more defects. Meanwhile, polycrystalline basic magnesium chloride likewise had more defects. These two points resulted a higher density of defects of MgO powders, and causing higher activity. Moreover, at a temperature of 1173 K, MgCl2 concentration of 300 g/L and N2 flow rate of 40 L/min, the thermal decomposition rate of MgCl2 reached 99.54%, the alkalinity of the powder reached 0.045 mol/g, and the iodine absorption value reached 102.72 mg I2/g MgO. Meanwhile, the high purity hydrochloric acid with a concentration of 6.70 mol/L was obtained.

Bioleaching of secondary and critical raw materials from Red Mud by a mixed culture in a semi-continuous reactor

Red Mud (RM) is a byproduct of the Bayer Process, used to extract alumina from bauxite. This residue contains valuable metals and rare earth elements (REEs), which can be bioleached under acidic conditions and later recovered, eventually reducing the RM pollution potential. The focus of this study was to extract metals through bioleaching using biostimulated biomass. A sequencing batch reactor (SBR) was operated at two different solid to liquid ratios (S/L, 2% and 1.5%) under aerobic conditions, using a feeding strategy based on pH evolution over time. The lowest pH obtained at 2% S/L was 3.8. Metals extraction efficiencies were 68 ± 18% for Mn, 58 ± 4.5% for Mg, 51 ± 2.9% for Al, 0.6 ± 0.07% for Ti and < 0.1% for Fe. At 1.5% S/L, a slightly lower pH was achieved (3.4), with metals extraction efficiencies similar to those obtained at 2% S/L, but more stable over time. At 1.5% S/L, REEs (i.e., Nd, Ce, Y, Sc and La) extraction efficiencies were also evaluated, and the highest value was obtained for Nd (around 65%). The results were promising and provided useful information for further enhancing the efficiency of metals extraction, in the perspective of process scale-up.

Preparation of magnetic oil-based gel microspheres containing di(2-ethylhexyl)phosphoric acid for extraction of scandium ions at low concentrations in aqueous solutions

Extraction of low-concentration rare earths is one of the important paths for the sustainability of the rare earth industry. The research and development of materials suitable for the extraction of rare earth ions at low concentrations is of great significance. Currently, the application of solvent extraction in the rare earth production industry is highly mature. However, it is not economical to use it for the extraction of low concentration rare earths with problems of phase separation and organic phase loss. This work innovatively proposes to encapsulate the extractant and diluent in magnetic oleogel microspheres, which are obtained by solubilizing magnetic poly (phenyl divinylbenzene)(PS-DVB) microspheres with the extractant and diluent.. The magnetic PS-DVB microspheres of 3 ∼ 16 μm were prepared by suspension polymerisation, followed by encapsulation of di(2-ethylhexyl)phosphoric acid (D2EHPA) and dichloroethane in magnetic PS-DVB microspheres using emulsion swelling, and then magnetic oil-based gel microspheres containing D2EHPA with a particle size of 10 ∼ 32 μm were obtained. The magnetic oil-based gel microspheres containing D2EHPA consist of about 96 wt% liquid phase and about 4 wt% solid phase, with D2EHPA accounting for more than 4.19 wt%. The magnetic oil-based gel microspheres are very close to small oil droplets and are superparamagnetic. The magnetic oil-based gel microspheres containing D2EHPA could completely extract 60 ppm of scandium ions(Sc3+) under the conditions of O:A = 1:50,1:60,1:70, and the extraction equilibrium times were 6, 9 and 12 min, respectively. This extractant encapsulation scheme inherits the selectivity of traditional extractants while simultaneously preserving the advantages of rapid extraction by solvent extraction.

Rare earth element extraction from geothermal brine using hybrid capacitive-deionisation process

Rare Earth Elements (REE) in geothermal brine include pollutants such as dissolved Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, lithium, and other ions. These REEs in geothermal brine, also popularly known as “Vitamins of the modern industry”, are vital for industries such as new energy vehicles, wind turbines, radar systems, laser crystals, etc., and harmful for agriculture and drinking purposes. Hence, identifying, quantifying, and extracting these REEs are essential and economical for a geothermal plant. The present study systematically investigates identifying and quantifying the REE and other essential ions in geothermal brine sources from Gujarat regions. For the extraction of REE from geothermal brine, geothermal brine treatment systems and their integration with automation control are designed in the present work. The proposed system filters geothermal brine and extracts REE through a hybrid filtration setup using capacitive deionization. Solar photovoltaic Water Filtration uses a hybrid Capacitive De-Ionization (CDI) treatment-based prototype to purify water and extract REE. The CDI method is an emerging technology in the desalination systems. It has far greater leverage over other desalination methods such as electrodialysis. The proposed design allows the simultaneous removal of various dissolved organic and inorganic contaminants in geothermal brine.

Bioleaching of rare earth elements (REEs) from Indonesian red mud by the bacterium Bacillus nitratireducens strain SKC/L-2

Red mud, a residue of the bauxite industry, represents a secondary source of rare earth elements (REEs) with substantial commercial value and untapped potential. Bioleaching, an innovative, cost-effective, and environmentally friendly method, offers a means of extracting valuable metals from mining wastes. This study explored the bioleaching of Indonesian red mud using Bacillus nitratireducens strain SKC/L-2 to recover REEs. The experiments were carried out over three days at 25 °C with different concentrations of red mud (1.5, 3, and 6 g/L) and a 10% v/v bacterial inoculum in a specific bioleaching medium. The findings indicated a slight reduction in REEs extraction by the bacterium as the red mud concentration increased from 1.5 to 6 g/L in the direct bioleaching process. In the experiment using 1.5 g/L red mud, 16 REEs were successfully extracted, with high extraction levels for specific elements such as Lu (92.0%), Tb (80.61%), and Gd (67.42%). However, when the red mud concentration was increased to 6 g/L, the survival potential of Bacillus nitratireducens strain SKC/L-2 decreased, leading to reduced recovery of elements such as Lu (76.80%), Tb (70.30%), and Gd (55.83%). The study reveals the behaviour of Bacillus nitratireducens in interacting with red mud and enduring high alkalinity, resulting in REEs extraction. These findings enhance the understanding of microbial interactions with red mud and provide insights into potential resource recovery applications.