Search Results (135)

Lanthanide rare earth elements possess significant promise for material applications owing to their distinctive optical and magnetic characteristics, as well as their versatile coordination capabilities. This study introduced a lanthanide-functionalized magnetic nanocellulose composite (NNC@Fe₃O₄@La(OH)₃) for effective phosphorus/nitrogen (P/N) ligand separation. The hybrid material employs the adaptable coordination geometry and strong affinity for oxygen of La³⁺ ions to show enhanced DNA-binding capacity via multi-site coordination with phosphate backbones and bases. This study utilized cellulose as a carrier, which was modified through carboxylation and amination processes employing deep eutectic solvents (DES) and polyethyleneimine. Magnetic nanoparticles and La(OH)₃ were subsequently incorporated into the cellulose via in situ growth. NNC@Fe₃O₄@La(OH)₃ showed a specific surface area of 36.2 m²·g⁻¹ and a magnetic saturation intensity of 37 emu/g, facilitating the formation of ligands with accessible La³⁺ active sites, hence creating mesoporous interfaces that allow for fast separation. NNC@Fe₃O₄@La(OH)₃ showed a significant affinity for DNA, with adsorption capacities reaching 243 mg/g, mostly due to the multistage coordination binding of La³⁺ to the phosphate groups and bases of DNA. Simultaneously, kinetic experiments indicated that the binding process adhered to a pseudo-secondary kinetic model, predominantly dependent on chemisorption. This study developed a unique rare-earth coordination-driven functional hybrid material, which is highly significant for constructing selective separation platforms for P/N-containing ligands. Full article

Bacillus species have shown the potential to recover rare earth elements (REEs), but strains with adsorption selectivity for terbium(III) remain understudied. In this study, six Bacillus strains with the capability for efficient adsorption of Tb(III) were screened from an ionic rare earth mine and were identified based on 16S rRNA gene sequencing. Adsorption experiments showed that Bacillus sp. DW011 exhibited exceptional Tb(III) adsorption efficiency, with an adsorption rate of 90.45% and adsorption selectivity for heavy rare earth elements. Notably, strain DW011 was also found to be tolerant against Tb(III) with the 24 h 50% lethal concentration (LC₅₀) of 2.62 mM. The biosorption mechanisms of DW011 were investigated using adsorption kinetics, SEM-EDS, and FTIR. The results indicated that the adsorption of strain DW011 conforms to the second-order kinetic model, and the teichoic acid–peptidoglycan network (phosphate-dominated) serves as the primary site for heavy REE adsorption, while carboxyl/amino groups in the biomembrane matrix provide secondary sites for LREEs. This study provides new information that Bacillus strains isolated from ionic rare earth mine deposits have potential as green adsorbents and have high selectivity for the adsorption of heavy REEs, providing a sustainable strategy for REE recovery from wastewaters. Full article

Bis(2-ethylhexyl) phosphate (P204) is widely used in extraction processes in the nuclear and rare earth industries. However, its high solubility in water results in high levels of total organic carbon and phosphorus in aqueous environments, and may also lead to radioactive contamination when it is used to combine with radionuclides. In this paper, we characterized a coconut shell activated carbon (CSAC) and a coal-based activated carbon (CBAC) for the adsorption of P204 and then evaluated their adsorption performance through batch and column experiments. The results found that, except for the main carbon matrix, CSAC and CBAC carried rich oxygen-containing functional groups and a small amount of inorganic substances. Both adsorbents had porous structures with pore diameters less than 4 nm. CSAC and CBAC showed good removal performance for P204 under low pH conditions, with removal efficiencies significantly higher than those of commonly used adsorption resins (XAD-4 and IRA900). The adsorption kinetics of P204 conformed to the pseudo-second-order kinetic model, and the adsorption isotherms conformed to the Langmuir model, indicating a monolayer chemical reaction mechanism. Both adsorbents exhibited strong anti-interference capabilities; their adsorption performance for P204 did not change greatly with the ambient temperature or the concentrations of common interfering ions. Column experiments demonstrated that CSAC could effectively fix dissolved P204 with a removal efficiency exceeding 90%. The fixed P204 could be desorbed with acetone. The findings provide an effective method for the recovery of P204 and the regeneration of spent activated carbon, which shows promise for practical applications in the future. Full article

Rare earth elements (REEs) have garnered significant global attention due to their essential role in advanced technologies. Sri Lanka is endowed with various REE-bearing minerals, including the apatite-rich deposit in the Eppawala area, commonly known as Eppawala rock phosphate (ERP). However, direct extraction of REEs from ERP is technically challenging and economically unfeasible. This study introduces a novel, integrated approach for recovering REEs from ERP as a by-product of nitrophosphate fertilizer production. The process involves nitric acid-based acidolysis of apatite, optimized at 10 M nitric acid for 2 h at 70 °C with a pulp density of 2.4 mL/g. During cooling crystallization, 42 wt% of calcium was removed as Ca(NO₃)₂.4H₂O while REEs remained in the solution. REEs were then selectively precipitated as REE phosphates via pH-controlled addition of ammonium hydroxide, minimizing the co-precipitation with calcium. Further separation was achieved through selective dissolution in a sulfuric–phosphoric acid mixture, followed by precipitation as sodium rare earth double sulfates. The process achieved over 90% total REE recovery with extraction efficiencies in the order of Pr > Nd > Ce > Gd > Sm > Y > Dy. Samples were characterized for their phase composition, elemental content, and morphology. The fertilizer results confirmed the successful production of a nutrient-rich nitrophosphate (NP) with 18.2% nitrogen and 13.9% phosphorus (as P₂O₅) with a low moisture content (0.6%) and minimal free acid (0.1%), indicating strong agronomic value and storage stability. This study represents one of the pioneering efforts to valorize Sri Lanka’s apatite through a novel, dual-purpose, and circular approach, recovering REEs while simultaneously producing high-quality fertilizer. Full article

Rare earth metals (REMs) are vital for high-tech industries, but their extraction from secondary sources is challenging due to environmental and technical constraints. This study investigates the ion-exchange extraction of light REMs (neodymium, praseodymium, and samarium) from sulfuric and phosphoric acid solutions, modeling industrial leachates from apatite concentrates and phosphogypsum. The study considers the use of anion- and cation-exchange resins with different functional groups for efficient and environmentally safe REM separation. Experimental sorption isotherms were obtained under static conditions at 298 K and analyzed using a thermodynamic model based on the linearization of the mass action equation. Equilibrium constants and Gibbs energy were calculated, which reveals the spontaneity of the processes. Cation-exchange resins demonstrated high selectivity towards individual REMs, while anion-exchange resins were suitable for group extraction. Infrared spectral analysis confirmed the presence of sulfate and phosphate complexes in the resin matrix, clarifying the ion-exchange mechanisms. Thermal effect measurements indicated exothermic sorption on anion-exchange resins with negative entropy and endothermic sorption on cation-exchange resins with positive entropy. The findings highlight the potential of ion-exchange resins for selective and sustainable REM recovery, offering a safer alternative to liquid extraction and enabling the valorization of industrial wastes like phosphogypsum for resource recovery. Full article

Hollow fibre renewal liquid membranes (HFRLMs) are susceptible to third-phase formation during rare earth element (REE) extraction using D2EHPA (bis(2-ethylhexyl phosphoric acid)), potentially leading to membrane fouling and decreased mass transfer efficiency. This study investigated the effects of various parameters, such as the composition of the aqueous feed and organic phases, on the third-phase formation and limiting organic concentration (LOC) of REE(III) in D2EHPA. Higher concentrations of REEs and a higher pH in the feed phase correlated with decreased mass transfer, while yttrium showed a greater propensity to induce third-phase formation compared to other REEs. Conditions favouring the use of linear aliphatic diluents, low extractant concentrations (5–10 v/v% D2EHPA) and the absence of modifiers also contributed to third-phase formation. The addition of tri-n-butyl phosphate (TBP) mitigated third-phase formation without evidence of synergy with D2EHPA. These findings provide key insights into formulating extraction systems that prevent third-phase formation in HFRLM processes. Full article

The South China Block hosts extensive sedimentary phosphorites that offer valuable insights into both paleoenvironmental reconstruction and rare earth element (REE) resource potential. However, the mechanisms governing REE enrichment in these deposits remain poorly understood. This study investigates two distinct phosphorite layers from the Lower Cambrian Zhujiaqing (ZJQ) Formation in the Bailongtan (BLT) area of the Yangtze Platform using integrated analyses including petrology, XRD, major and trace elements, δ¹³C and δ¹⁸O isotopes, and LA-ICP-MS. The lower thin-bedded phosphorite, composed of finer phosphatic grains (<300 μm), exhibits significantly higher REE concentrations (883.6 ± 160.9 ppm; n = 48) compared to the upper thick-bedded phosphorite (303.2 ± 82.7 ppm; n = 64), which is dominated by larger, reworked grains (300–600 μm). Intervening strata consist of laminated phosphate-bearing carbonates interbedded with quartz, dolomite, and pyrite. PAAS-normalized REE patterns display MREE–HREE enrichment, negative Ce anomalies (avg. 0.60 ± 0.18; n = 18), and positive Y anomalies—indicative of oxic depositional conditions. The elevated REE content in the lower layer, coupled with the lowest δ¹³C values (−4.59‰), suggests enrichment linked to organic matter degradation. A proposed two-stage depositional model links REE enrichment to proximity with REE-rich deep-shelf waters, underscoring the critical role of redox and depositional dynamics in phosphorite-hosted REE accumulation. Full article

The chemical extraction of rare-earth elements (REEs) from Estonian graptolite-argillite (GA) and phosphate rock (Phosphorite, PH) samples has been conducted and analyzed. For the initial leaching process, HCl and HNO₃ with different concentrations were used to extract REEs from GA and PH. Different extraction agents, including ionic liquids, were examined for the extraction of REEs from acidic aqueous solutions in the liquid–liquid extraction step. After leaching and extraction, all samples were characterized using the inductively coupled plasma mass spectrometry method (ICP-MS/MS). The highest REE extraction efficiencies from GA were established with 1-ethyl-3-methyl imidazolium diethyl phosphate (EMImDEPO₄) and from PH using bis(2-ethylhexyl) phosphate (D2EHPA). Full article

This study evaluates the predictive performance of advanced machine learning models, including DeepBoost, XGBoost, CatBoost, RF, and MLP, in estimating the Ω₂, Ω₄, and Ω₆ parameters based on a comprehensive set of input variables. Among the models, DeepBoost consistently demonstrated the best performance across the training and testing phases. For the Ω₂ prediction, DeepBoost achieved an R² of 0.974 and accuracy of 99.895% in the training phase, with corresponding values of 0.971 and 99.902% in the testing phase. In comparison, XGBoost ranked second with an R² of 0.929 and accuracy of 99.870% during testing. For Ω₄, DeepBoost achieved a training phase R² of 0.955 and accuracy of 99.846%, while the testing phase results included an R² of 0.945 and accuracy of 99.951%. Similar trends were observed for Ω₆, where DeepBoost obtained near-perfect training phase results (R² = 0.997, accuracy = 99.968%) and testing phase performance (R² = 0.994, accuracy = 99.946%). These findings are further supported by violin plots and correlation analyses, underscoring DeepBoost’s superior predictive reliability and generalization capabilities. This work highlights the importance of model selection in predictive tasks and demonstrates the potential of machine learning for capturing complex relationships in data. Full article

NASICON-type titanium and zirconium phosphates doped with rare-earth cations, A_0.33M₂(PO₄)₃ (M = Ti, Zr; A = Dy, Y, Yb), were synthesized using the sol–gel method and investigated as catalysts for ethanol dehydration at 300–400 °C. The catalysts were characterized via XRD, SEM, BET, and FTIR spectroscopy. The relationships between the catalyst composition, acidity and the dehydration activity were evaluated. Diethyl ether (DEE) formation is promoted by the presence of the zirconium phosphates (ZrP), while the presence of titanium phosphate (TiP) catalyzes the formation of both ethylene and diethyl ether (DEE). The application of Fourier-transform infrared (FTIR) spectroscopy to the analysis of adsorbed C₆H₆ has revealed the presence of hydroxyl groups exhibiting varying degrees of proton-donating mobility. This finding has enabled the correlation of the structure of the active sites with the process’s selectivity. The results underscore the key function of OH-group localization and framework geometry in the control of form-selective reactions. Full article

The growing demand for rare earth elements (REEs) in high-tech and green energy sectors has prompted renewed exploration of unconventional sources. Drill cuttings, which are commonly discarded during subsurface drilling, are increasingly recognized as a potentially valuable, underutilized secondary REE reservoir. This review adopts a mineral-first lens to assess REE occurrence, extractability, and recovery strategies from drill cuttings across various lithologies. Emphasis is placed on how REEs associate with specific mineral host phases ranging from ion-adsorbed clays and organically bound forms to structurally integrated phosphates, each dictating distinct leaching pathways. The impact of drilling fluids on REE surface chemistry and mineral integrity is critically examined, alongside an evaluation of analytical and extraction methods tailored to different host phases. A scenario-based qualitative techno-economic assessment and a novel decision-tree framework are introduced to align mineralogy with optimal recovery strategies. Limitations in prior studies, particularly in characterization workflows and mineralogical misalignment in leaching protocols, are highlighted. This review redefines drill cuttings from industrial waste to a strategic resource, advocating for mineralogically guided extraction approaches to enhance sustainability in the critical mineral supply chain. Full article

Rare earth-doped phosphate glasses have found widespread application in the field of solid-state and fiber laser technologies. Nevertheless, the fabrication of high-quality rare earth-doped phosphate glasses with minimal residual hydroxyl groups remains a significant challenge. To address this, a two-step melting process was utilized in this work to synthesize Er³⁺-Yb³⁺ co-doped phosphate glasses with low residual hydroxyl group content and improved optical quality. When re-melted under a N₂ atmosphere at 900 °C for 12 to 16 h, the hydroxyl absorption coefficient (α_-OH) decreased to ~1 cm⁻¹. The structural and compositional characteristics of the glass remained essentially unchanged throughout the re-melting process. The weak broadband absorption in the visible range and the red-shift of the ultraviolet absorption edge were attributed to the reduction in residual hydroxyl group content rather than carbon contamination. The dehydroxylation mechanism was governed by the physical diffusion of hydroxyl groups within the glass matrix. Full article

Phosphogypsum, a byproduct of phosphate fertilizer production, poses significant environmental challenges due to its large volume, hazardous composition, and radioactivity. Conventional disposal methods, such as stockpiling and landfilling, contribute to soil and water contamination and present risks to human health. This article explores the potential of integrating phosphogypsum into a circular economy framework, focusing on reducing environmental impacts and extracting value from this industrial waste. A detailed assessment of phosphogypsum’s chemical composition, including trace metals and radionuclides, is essential for effective management. This review paper examines safe handling, storage, and disposal strategies to minimize environmental risks. Additionally, innovative reuse applications are investigated, such as incorporating phosphogypsum into construction materials like cement, plasterboard, and concrete and its use in agriculture as a soil amendment or for land reclamation. The recovery of critical elements, particularly rare earth elements (REEs), highlights its potential to reduce waste and contribute to meeting the growing demand for strategic resources. Despite its promise, challenges remain, including chemical variability and the presence of radioactive components. This article identifies the technological and regulatory steps required to enable safe, large-scale reuse of phosphogypsum, emphasizing its role in advancing sustainable resource management within a circular economy. Full article

Bayan Obo rare earth concentrate (BOREC) is composed of bastnaesite, monazite and fluorite, which is recognized as a refractory mineral in the world. In order to solve the problems of waste gas treatment and comprehensive utilization efficiency of BOREC decomposed by the current concentrated sulfuric acid roasting method (500–700 °C), H₂SO₄-HCl mixed acid assisted by aluminum salt was used to leach out the bastnaesite, and the optimal conditions were determined as follows: c(H⁺) = 7 mol/L, c(1/2H₂SO₄):c(HCl) = 5:1, c(Al₂(SO₄)₃) = 0.25 mol/L, temperature 135 °C, liquid–solid ratio of 42:1, and reaction time 3 h. At this time, the leaching rates of concentrate and rare earth (La, Ce, Pr and Nd) were 74.08% and 71.95%, respectively, and the decomposition rate of bastnaesite was 96.83%. At the same time, the yield of calcium sulfate was 77.35% and the purity was 99.22%. Subsequently, sodium sulfate was added with m(Na₂SO₄):m(RE₂O₃) = 2.5:1, and the recovery rate of rare earth was 99.5%, and the purity of rare earth double salt product was 98.47% at a temperature of 90 °C. After most of the acid had been extracted with triethyloctanamine, sodium fluoride was added with a fluorine–aluminum ratio of 6:1, sodium carbonate was used to adjust pH = 3, and cryolite was obtained with a purity of 95.59% and an aluminum recovery rate of 99.6% at 90 °C. Since the separation of bastnaesite and monazite has been basically realized in the leaching stage, it is conducive to the docking of subsequent alkali decomposition and recovery of trisodium phosphate, realizing the comprehensive recovery of rare earth, fluorine, calcium, aluminum and phosphorus. Full article

Rare earth elements (REEs) are important strategic resources, widely used in various technological fields, especially heavy rare earth elements (HREEs). China has extensive rare earth deposits, with diverse mineral types and a complete range of rare earth elements, characterized by a “heavy south, light north” resource distribution pattern. The rare earth-bearing collophane in the Zhijin area of Guizhou is a typical marine sedimentary phosphorite deposit with large reserves and a high heavy rare earth content. This study investigates the rare earth-bearing collophane in the Zhijin area using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) to analyze its mineral composition and occurrence characteristics. In terms of flotation, a reverse flotation process for magnesium removal was adopted. By optimizing the flotation parameters, including grinding fineness, collector dosage, pH regulator dosage, and depressant dosage, the optimal flotation conditions were determined. A further mineralogical analysis was conducted on both the flotation concentrate and tailings. The results show that the main minerals in the rare earth-bearing collophane of Zhijin are fluorapatite and dolomite, with dolomite as the primary gangue mineral, and rare earth elements are mainly hosted in fluorapatite. The optimal flotation conditions were achieved when the grinding fineness was −74 μm with an 83% passing rate, XF-1 was used as the collector at a dosage of 300 g/t, sulfuric acid (H₂SO₄) as the pH regulator at 6 kg/t, and phosphoric acid (H₃PO₄) as the depressant at 3 kg/t. By employing an optimal reagent regime and implementing a reverse flotation process consisting of one roughing and one scavenging stage, a phosphate concentrate was obtained with a P₂O₅ grade of 31.61% and an REO content of 0.161%. The P₂O₅ recovery reached 84.22%, while the REO recovery was 78.65%. Compared to the raw ore, the P₂O₅ grade increased by 11.52 percentage points, and the REO content improved by 0.051 percentage points. Mineralogical analysis of the flotation concentrate and tailings revealed that dolomite was effectively removed by reverse flotation, while rare earth elements were successfully enriched in the phosphate concentrate. In conclusion, this study provides an efficient flotation separation process for rare earth-bearing collophane and dolomite, while also offering technical support for the efficient recovery of rare earth resources. This research has significant theoretical and practical implications. Full article