Search Results (135)

This study presents an integrated process for the recovery and purification of lithium hydroxide (LiOH) from lithium sulfate (Li₂SO₄) solution obtained by sulfuric acid leaching of spent crucibles used for producing the cathodes of LIBs. The recovered leachate contains considerable concentrations of metallic impurities, including Na, K, Mg, Ca, Al, and Ni, which hinder the direct production of high-purity LiOH. To overcome this limitation, a pretreatment step combining cation- and anion-exchange resins was introduced to control impurity levels and condition the solution prior to conversion. Under the optimized ion-exchange condition of 10 g cation-exchange resin and 50 g anion-exchange resin, the solution pH was adjusted to 6–7, resulting in effective impurity removal through combined ion-exchange and solution-conditioning effects. More than 90% of Al was removed, while Mg, Ca, Na, K, and Ni were removed by approximately 70–75%. After purification, LiOH was produced through a double-displacement conversion reaction using Ba(OH)₂. The results showed that the reaction temperature and the [OH]:[Li] molar ratio were the key parameters governing the sulfate-removal-based apparent conversion efficiency and filtrate-based LiOH purity. Excess OH⁻ promoted the formation of dissolved and complexed species, thereby lowering the purity of the LiOH-containing filtrate. In contrast, the optimum condition was identified at 70 °C and an [OH]:[Li] molar ratio of 1:1, under which SO₄²⁻ was effectively removed as solid BaSO₄. Under these conditions, the sulfate-removal-based apparent conversion efficiency reached 91.91%, and the filtrate-based LiOH purity was 98.84%. X-ray diffraction analysis confirmed the coexistence of LiOH·H₂O and LiOH phases in the final recovered product, whereas the precipitate was identified as single-phase BaSO₄, indicating effective sulfate removal. Overall, this study demonstrates the feasibility of producing high-purity LiOH from sulfation-derived Li₂SO₄ leachate through a sequential process consisting of impurity removal, conversion, and drying. The findings provide fundamental process data for the design of lithium recovery and purification routes using spent cathode crucibles as secondary lithium resources. Full article

Background/Objectives: Terbium-161 is an interesting and promising theranostic radionuclide, thanks to its decay characteristics (T_1/2 = 6.95 d, E(β)_max = 593 keV, E(β)_av = 154 keV, E(γ) = 74.6 keV (10.2%)). Having similar chemical properties, it is considered as an alternative to currently used ¹⁷⁷Lu. In addition, ¹⁶¹Tb emits a significant amount of conversion and Auger electrons, which contribute to the enhancement of localised therapeutic effect. The aim of this paper is to describe the preparation of ¹⁶¹Tb in quantity and quality relevant for preclinical and early clinical studies and to provide practical notes on the preparation. Methods: No-carrier-added ¹⁶¹Tb has been repeatedly prepared by neutron irradiation of highly enriched ¹⁶⁰Gd targets (up to 98 mg of ¹⁶⁰Gd₂O₃) at nuclear reactor LVR-15 (CV Řež, Czech Republic) in four different irradiation positions. The separation and purification process of ¹⁶¹Tb from the bulk of ¹⁶⁰Gd target was performed by cation exchange chromatography with Dowex 50 W × 8 (H⁺ cycle, 200–400 mesh). Terbium-161 was obtained in ¹⁶¹TbCl₃ form and formulated into 0.1 M HCl solution. The γ-ray spectrometry was used for radionuclide identification and radionuclidic purity and the ICP-MS method for chemical purity measurements and specific activity determination. The DOTA labelling assay was performed, as described by Gracheva et al., providing an assessment of the apparent molar activity of the preparation in terms of its competitive interaction with stable daughter nuclide ¹⁶¹Dy. Results: Irradiations (59.2 h to 421.52 h) of enriched ¹⁶⁰Gd targets with mass ranging from 43.4 to 144.0 mg for ¹⁶⁰Gd(NO₃)₃ and from 12.5 to 98.3 mg for ¹⁶⁰Gd₂O₃ yielded 1.3–23.7 GBq of ¹⁶¹Tb. The separation yields of purified ¹⁶¹Tb varied from 85 to 99%, with the activities of 9.9–22.1 GBq and the highest achieved specific activity of the final product was 4.1 GBq/μg (of Tb). The DOTA chelator was radiolabelled with ¹⁶¹Tb at time points from 2 to 14 days after the end of separation (EOS). Conclusions: Based on our results, we describe practical aspects of terbium production at the laboratory scale with a particular focus on practical aspects and issues arising during the process that may surprise even experienced radiochemists, as lanthanoid separation is not always straightforward, even though it is well-known and has been extensively studied. The preparation of ¹⁶¹Tb in a n.c.a. form proceeds, according to the reported data, with high reproducibility and achieves significant activity levels suitable for both preclinical and clinical investigations by irradiation of highly enriched ¹⁶⁰Gd targets in LVR-15 reactor with subsequent separation and purification of ¹⁶¹Tb on cation exchange resin Dowex 50 W × 8(H⁺). The produced [¹⁶¹Tb]TbCl₃ is employed in subsequent experimental research and development for the labelling of preparations intended for preclinical applications. Full article

Calcium tartrate (CaT) instability in bottled wines has become a recurrent issue. Conventional stabilization strategies, such as cold stabilization or the use of protective colloids, can be ineffective or yield inconsistent results. Cation-exchange resins and electrodialysis can reduce the risk of CaT precipitation, but their use is limited by cost and availability. Therefore, the aim of this study was to assess sodium alginate, a natural divalent metal chelator, as a processing aid to remove calcium and improve CaT stability. The study began with the characterization of the alginate composites formed in wines, followed by an evaluation of different doses and contact times. Subsequently, a series of conventional and dealcoholized wines was evaluated, showing significant reductions in calcium concentration (i.e., 27–32% in conventional wines and 10–21% in dealcoholized or reduced-alcohol wines) and improved CaT stability. Besides a significant increase in sodium content, conductivity, and turbidity (p < 0.05), most other compositional parameters remained stable, with variations observed only in some wines for certain parameters (e.g., CIELab parameters). These findings demonstrate the potential of sodium alginate as a practical calcium-binding agent and suggest the need for further studies to continue evaluating its applicability in winemaking. Full article

The cleavage of cumene hydroperoxide (CHP) via the Hock rearrangement is a cornerstone process in the chemical industry, responsible for over 90% of global phenol and acetone production. Despite its industrial significance, the conventional use of homogeneous sulfuric acid catalysis presents critical drawbacks, including severe equipment corrosion, generation of hazardous waste, and the need for complex neutralization steps. This review explores the transition toward heterogeneous solid acid catalysts as a sustainable alternative, emphasizing the relationship between catalyst structure, surface acidity, and reaction performance. Key catalyst families—such as ion-exchange resins, zeolites, and heteropolyacids—are systematically evaluated, with a focus on how Brønsted acid site density and porous architecture influence catalytic activity and selectivity. Particular attention is given to deactivation mechanisms, including coking, leaching of active species, and poisoning by inorganic cations, alongside mitigation strategies enabled by rational catalyst design and regeneration protocols. Additionally, we highlight recent progress in reactor engineering, particularly the integration of solid acid catalysts in reactive distillation and microchannel configurations. These insights offer a strategic perspective for developing more efficient and environmentally benign industrial processes for the Hock cleavage of cumene hydroperoxide. Full article

This study presents a novel, integrated membrane–resin hybrid platform for the high-efficiency purification of N-acetylneuraminic acid (sialic acid, NANA) from complex microbial fermentation broths. By synergistically combining four sequential stages—ceramic microfiltration (50 nm), ultrafiltration (3 kDa), nanofiltration (150 Da), and dual-resin purification (macroporous adsorption + cation-exchange)—the process achieves stepwise removal of cells, proteins, pigments, monovalent salts, and divalent metal ions without using organic solvents or high-salt buffers. Critically, each stage demonstrates high target recovery: 76.2% (CM), 67.3% (UF), and 77.5% (NF), with near-quantitative retention (>95%) during resin treatment due to NANA’s low hydrophobicity and electrostatic repulsion at pH 6.8. Following optimised acidification crystallisation (acetic acid dosage = 3 × concentrate volume; sialic acid concentrate concentration = 333.49 g/L), the final product reaches 97.9% purity with a crystalline yield of 78.6%. This scalable, green purification strategy eliminates major bottlenecks in downstream processing and enables industrial-scale production of pharmaceutical-grade sialic acid, with broad applicability to other high-value acidic biomolecules. Full article

Mn and Fe complexes of ethylene cross-bridged tetraazamacrocycles, known to retain their reactive metal ions even under harsh aqueous conditions due to the rigidity and topological constraint of the ligands, with methyl, allyl and benzyl pendant arms were electrostatically fixed to a commercial cation exchange resin, and their effectiveness and recyclability in the bleaching of organic dyes, namely, methyl orange, methylene blue and rhodamine B, were determined. These molecular Mn and Fe tetraazamacrocycle catalysts have been previously reported as homogeneous solution phase catalysts for bleaching organic dyes, but could not be feasibly recovered for multiple cycles of dye bleaching. Herein, we report the potential of these resin-fixed solid-state metal complex catalysts in the degradation of organic dyes. The Mn catalysts were faster in the first cycle of dye bleaching, but their bleaching rate slowed considerably (to about 10% on average) in additional cycles. In contrast, the Fe catalysts were slower in the first cycle of dye bleaching, but were able to bleach dyes for up to five cycles while retaining more of their original reactivity (30–50% on average), suggesting their potential recyclability. Thus, these resin-fixed tetraazamacrocyclic metal complex catalysts, when coupled with the demonstrated rechargeability of the resin with fresh catalyst, may one day be effectively used for water purification applications. SEM and optical microscopy images demonstrated the robustness of the resin bead across multiple cycles, while EDS experiments confirmed the continued presence of Mn and Fe on the bead surface after multiple cycles. Full article

Recovery of scandium from chloride-bearing process liquors formed during titanium–magnesium production remains constrained by trace-level metal content and chemically aggressive solution matrices. Within the present study, the retention behaviour of Sc³⁺ species in strongly acidic chloride media was examined through batch-mode interaction with gel-type sulfonated cation exchangers, namely KU-2-8, Lewatit SP112H, Purosorb SAC140H, and Purolite C-150H. Quantitative evaluation of sorption efficiency was performed by calculating equilibrium uptake (q_e), phase distribution factor (K_d), and percentage recovery (R). Under identical liquid–solid ratios, the Lewatit SP112H matrix exhibited superior affinity toward dissolved scandium, achieving q_e = 179.82 mg/g and K_d = 172.41 mL/g. Equilibrium fitting procedures revealed that scandium uptake by Purosorb SAC140H conforms to monolayer-type retention described by the Langmuir formalism (R² = 0.9786), whereas sorption on Lewatit SP112H proceeds over energetically non-uniform sites and is more adequately represented by Freundlich and Dubinin–Radushkevich approximations. The observed retention characteristics establish a selection framework for ion-exchange media applicable to scandium concentration from acidic chloride hydrometallurgical streams. Full article

Addressing the need for efficient separation of critical elements from NdFeB magnets, this study introduces, for the first time, a D001 cation exchange resin for the selective separation Co(II) from Nd(III) and Dy(III). At pH 5, the resin adsorbs Nd and Dy with high capacities (97.57 and 86.38 mg/g, respectively) and efficiencies (over 98%), but shows low affinity for Co (26.6% efficiency). The resin exhibits excellent stability across a wide pH range of 2–7 and maintains high adsorption performance over five consecutive cycles. The process follows pseudo-second-order kinetics and the Langmuir model. Co(II) is effectively desorbed with high purity (>99%) using 2.5 M H₂SO₄. Characterization confirms that adsorption occurs via ion exchange on –SO₃Na groups. This method successfully separates Co, providing a high-purity stream for further rare earth purification and demonstrating strong industrial potential. Full article

At present, a wide range of commercial resins is available for diverse applications, whether in both the food and industrial sector. However, limited information is available in the literature to scientifically evaluate the effectiveness and behaviour of new commercial resins under varying application conditions. In this study, the Purolite MB400 ion-exchange resin was investigated for its capacity to simultaneously remove metal cations (Cu, Zn, Fe) and sulphates from model solutions. The highest efficiency was observed in the CuSO₄ model solution (10 mg/L), where Cu²⁺ removal reached 97.8% and SO₄²⁻ removal 95.1%. However, increasing concentrations of metals and sulphates resulted in a gradual decline in removal efficiency. Full article

This study represents comprehensive research that arises from the advanced sorption properties of zwitterionic resin beads, which were tested on simulated mono- and multicomponent heavy metal ion (HMI)-polluted water, compared to the stream collected in the Tarnita mine area. Ionic exchange resins (IExRs) were first synthesized in cationic form from a highly crosslinked (8%) acrylic copolymer, by introducing different side groups containing amino functionalities, such as ethylenediamine, triethylenetetramine, and hydrazine hydrate. The corresponding zwitterionic form of each IExR was obtained by reacting the cationic resins with sodium chloroacetate. The structures and morphologies of the synthesized resins were characterized using scanning electron microscopy and infrared spectroscopy. Successful removal of Cu(II), Fe(II), and Mn(II) was quantified by using atomic absorption spectroscopy. Tests with multicomponent synthetic solutions revealed the following typical order of retention: Cu(II) > Fe(II) > Mn(II). In the case of water samples collected from the Tarnita area, the zwitterionic resins were able to retain approximately 93.8% Mn(II), 94.7% Fe(II), and >95.5% Cu(II); in all instances, the concentration of Fe(II) was significantly higher than that of Cu(II) and Mn(II). Additionally, sorption isotherms, kinetics, and thermodynamic parameters were studied. Wheat germination was included to test the efficiency of the batch sorption using IExRs, compared to the stream collected from Tarnita, highlighting how the water cleaning process leads to healthy plant growth. The results demonstrate that, after IExRs sorption the tested HMIs content is below the permissible maximum level for surface water, effectively mitigating the pollution of the steam near to the Tarnita closed mine area, removing the main contaminants found in it. Full article

A technology aimed at reducing extremely high water hardness in Chotěšov, a village in the Czech Republic, was developed and tested. Three treatment methods were evaluated under laboratory conditions: softening filtration using a cation exchange resin in the Na⁺ cycle (resulting in a 72% reduction in hardness); nanofiltration (NF); and reverse osmosis (RO), which reduced hardness by 71% and 96%, respectively. The mixing of the permeate with treated groundwater at a volume ratio of 1:1 resulted in a further reduction in hardness to 41% with NF permeate and to 53% with RO permeate, relative to the original value. Full article

Polymethoxy butyl ether (BTPOM_n), a novel diesel additive developed for suppressing incomplete combustion emissions, was synthesized via an optimized batch slurry method employing n-butanol and trioxane (TOX) over NKC-9 acid cation-exchange resin (90–110 °C). A comprehensive kinetic model elucidated the reaction mechanism, addressing competitive pathways governing both main product formation and key side reactions—specifically polyoxymethylene hemiformals (HD_n) and polyoxymethylene glycols (MG) generation. As the first detailed kinetic investigation of BTPOM_n synthesis, this work provides a fundamental dataset and a robust predictive model that are crucial for process intensification and reactor design. Hybrid optimization integrating genetic algorithms with nonlinear least-squares regression achieved robust parameter estimation, with model predictions showing excellent agreement with experimental data. Thermal effects significantly influenced reaction rates, enhancing decomposition and propagation processes with increasing temperature. Optimal catalyst loading was identified at 3 and 6 wt.%, balancing reaction acceleration and byproduct suppression. Temperature-dependent equilibrium revealed chain length regulation through growth and depolymerization processes. This mechanistic understanding enables predictive reactor design for cleaner fuel additive synthesis. It provides critical insights for developing emission-control technologies in diesel engine systems. Full article

Inspired by the mechanism of ion exchange resins, this study is a first-report in constructing a dual-layer photocathodic protective coating with ionic selectivity to enhance corrosion resistance property. The microstructure, composition, and ion selectivity of the coating are characterized by scanning electron microscopy, Raman spectroscopy, infrared spectroscopy, and membrane potential. It shows that the outer g-C₃N₄/TiO₂ cation-selective layer plays a role in preventing corrosive Cl⁻ ions passing through the coating; the inner g-C₃N₄-TiO₂-CTAB anion-selective layer could prevent Fe²⁺ ions from diffusing through the coating. Furthermore, the coated carbon steel sample demonstrates a minimum OCP (open circuit potential) value of −770 mV (vs. SCE) under illumination in 3.5% NaCl media. Interestingly, the OCP remains around −720 mV (vs. SCE) even after light deprivation. The synergistic effect between ion selectivity and photocathodic protection is described, in detail, in the following. Full article

The provision of potable water for armed forces at their operational sites necessitates a robust treatment chain to ensure the production of safe drinking water from potentially contaminated local water sources. Relying on single-use water bottles is not considered an eco-friendly option and on-site production may exhibit limited efficiency depending on the water contamination. This study therefore aimed to define a mobile processing chain that could efficiently produce drinking water on-site while offering a multi-barrier level of protection. To evaluate the system, contaminated water was prepared from different water sources and then spiked with various inorganic contaminants (metals, anions: Cl⁻, F⁻, I⁻, NO₂⁻, NO₃⁻, SO₄²⁻, CN⁻), organic contaminants (e.g., pesticides, petroleum hydrocarbons, polycyclic aromatic hydrocarbons, chlorinated solvents), and energetic compound (perchlorate) at levels ranging from 5 to 50 times the standard water quality criteria. A specific treatment process was defined optimized and evaluated at flow rates reaching 500 L/h. This treatment chain includes the following: a sediment filter, a greensand filter, a cation exchange resin, an anion exchange resin, an activated carbon adsorption filter, ultrafiltration, a UV lamp, and a reverse osmosis (RO) unit. This treatment system successfully met all water quality criteria, providing a reliable and effective alternative to an RO-only treatment regime. Full article

This study conducted a systematic investigation of the degradation pathway and process optimization of strong acid cation exchange resins subjected to SCWO. Controlled experiments evaluated the effects of operating temperature, oxidant stoichiometry, initial organic concentration, and residence time. RSM was utilized to refine the operating parameters, and a second-order regression model (R² = 0.9951) was established to predict COD removal (R_COD), valid within experimental ranges: reaction temperature 400–500 °C, oxidant stoichiometry 80–150%, initial COD 10,000–100,000 mg·L⁻¹, and residence time 1–10 min. COD-dependent NaOH addition could enhance degradation efficiency. The R_COD was sensitive to operating temperature, oxidant stoichiometry, and residence time. Under the optimized conditions of 472 °C, oxidant stoichiometry of 137%, initial COD of 77,216 mg·L⁻¹, and residence time of 4.9 min with the addition of 1.74 wt% NaOH, the R_COD reached 99.92%, which was in close agreement with model predictions. GC-MS analysis of intermediates revealed that sulfonic groups dissociated early, followed by aromatic compounds, particularly phenol, undergoing ring-opening and oxidation to small carboxylic acids and aliphatic species, which were ultimately mineralized to CO₂ and H₂O. These findings provide mechanistic insight into resin decomposition and offer a scientific basis for the safe treatment of radioactive waste resins using SCWO. Full article