Search Results (323)

The efficient recovery of rhenium (Re), a critical metal in high-tech industries, is essential to address its growing demand and reduce reliance on primary mining. In this study, we developed novel anion-exchange resins for the selective adsorption and recovery of Re(VII) ions from acidic solutions, simulating industrial by-products. The resins were synthesized from a vinylbenzyl chloride-co-divinylbenzene copolymer modified with aliphatic, heterocyclic, and aromatic weakly basic amines, selected from among bis(3-aminopropyl)amine (BAPA), 1-(2-pyrimidinyl)piperazine (PIP), thiosemicarbazide (TSC), 2-amino-3-hydroxypyridine (AHP), 1-(2-hydroxyethyl)piperazine (HEP), 4-amino-2,6-dihydroxypyrimidine (AHPI), and 2-thiazolamine (TA). The adsorption of Re on BAPA, PIP, and HEP resins obeyed the Langmuir model, and the resins exhibited high adsorption capacities, with maximum values reaching 435.4 mg Re g⁻¹ at pH 6. Furthermore, strong selectivity for ReO₄⁻ ions over competing species, including Mo, Cu, and V, was noted in solutions simulating the leachates of the by-products of Cu-Mo ores. Additionally, complete elution of Re was possible. The developed resins turned out to be highly suitable for the continuous-flow-mode adsorption of ReO₄⁻, revealing outstanding adsorption capacities before reaching column breakthrough. In this context, the novel anion-exchange resins developed offer a reference for further Re recovery strategies. Full article

This work investigated the ion exchange technique for selective separation of rare earth elements (REE) from acid mine drainage (AMD), using different column systems, pH values, and eluent concentrations. Systematic analysis of pH and eluent concentration showed that an initial pH of 6.0 and 0.02 mol L⁻¹ NH₄EDTA are the optimal conditions, achieving 98.4% heavy REE purity in the initial stage (0 to 10 bed volumes). This represents a 32-fold increase compared to the original AMD (6.7% heavy REE). The speciation of REE and impurities was determined by Visual Minteq 4.0 software using pH 2.0, which corresponds to the pH at the inlet of the fractionation column. Under this condition, La and Nd and the impurities (Ca, Mg, and Mn) remained in the fractionation column, while Al was partially retained. In addition, the heavy REE (Y and Dy) were mainly in the form of REE-EDTA complexes and not as free cations, which made fractionation more feasible. The fractionation column minimized impurities, retaining 100% of Ca and 67% of Al, generating a liquor concentrated in heavy REE. This sustainable approach adopted herein meets the critical needs for scalable recovery of REE from diluted effluents, representing a circular economy strategy for critical metals. Full article

Objectives: The oral route is the most widely used method of administration. However, the bitter taste of drugs is a prevalent issue compromising patient acceptance. This study aimed to develop a palatable amorphous trazodone hydrochloride (TRA) formulation via ion exchange with Amberlite IRP88 resin as the carrier. Methods: TRA-Amberlite IRP88 complexes (TRCs) were prepared using the static exchange method and their physical properties were then characterized. Molecular docking was carried out to elucidate the molecular interaction. Finally, the dissolution profiles and taste of TRCs were evaluated. Results: The Physical characterizations confirmed that TRA was amorphously dispersed in Amberlite IRP88. Importantly, the in vivo taste masking study suggested that the bitterness of TRA was effectively masked. The reason was that the dissociation of TRCs was suppressed in the saliva, resulting in reduced dissolution in the oral cavity. Conclusion: this study suggests that amorphization is effective in masking the bitterness of drugs and provides guidance for the development of palatable oral formulations. Full article

Esterification is a key transformation in the production of lubricants, pharmaceuticals, and fine chemicals. Conventional processes employing homogeneous acid catalysts suffer from limitations such as corrosive byproducts, energy-intensive separation, and poor catalyst reusability. This review provides a comprehensive overview of heterogeneous catalytic systems, including ion exchange resins, zeolites, metal oxides, mesoporous materials, and others, for improved ester synthesis. Recent advances in membrane-integrated reactors, such as pervaporation and nanofiltration, which enable continuous water removal, shifting equilibrium and increasing conversion under milder conditions, are reviewed. Dual-functional membranes that combine catalytic activity with selective separation further enhance process efficiency and reduce energy consumption. Enzymatic systems using immobilized lipases present additional opportunities for mild and selective reactions. Future directions emphasize the integration of pervaporation membranes, hybrid catalyst systems combining biocatalysts and metals, and real-time optimization through artificial intelligence. Modular plug-and-play reactor designs are identified as a promising approach to flexible, scalable, and sustainable esterification. Overall, the interaction of catalyst development, membrane technology, and digital process control offers a transformative platform for next-generation ester synthesis aligned with green chemistry and industrial scalability. Full article

Phosphorylated cellulose is proposed as a bio-resin for the removal of heavy metals, as a substitute for synthetic polymer-based materials. Phosphorylation is carried out using kraft pulp fibers as the cellulose source, with phosphate esters and urea as reactants to prevent significant fiber degradation. Herein, phosphorylated fibers, with three types of counterions (sodium, ammonium, or hydrogen), are used in adsorption trials involving four individual metals: nickel, copper, cadmium, and lead. The Langmuir isotherm model is applied to determine the maximum adsorption capacities at four different temperatures (10, 20, 30, and 50 °C), enabling the calculation of the Gibbs free energy (ΔG), entropy (ΔS), and enthalpy (ΔH) of adsorption. The results show that the adsorption capacity of phosphorylated fibers is equal or even higher than that of commercially available resins (1.7–2.9 vs. 2.4–2.6 mmol/g). However, the nature of the phosphate counterion plays an important role in the adsorption capacity, with the alkaline form showing a superior ion exchange capacity than the hybrid form and acid form (2.7–2.9 vs. 2.3–2.7 vs. 1.7–2.5 mmol/g). The thermodynamic analysis indicates the spontaneous (ΔG = (-)16–(-)30 kJ/mol) and endothermic nature of the adsorption process with positive changes in enthalpy (0.45–15.47 kJ/mol) and entropy (0.07–0.14 kJ/mol·K). These results confirm the high potential of phosphorylated lignocellulosic fibers for ion exchange applications, such as the removal of heavy metals from process or wastewaters. Full article

High-alumina fly ash may potentially be a valuable source of Ga with a concentration of Ga at 80 mg/kg. Direct adsorption and enrichment of Ga from sulfuric acid leach liquor of high-alumina fly ash is developed in this study. The H-type chelating resin with two carboxy groups exhibited the best adsorption capacity for Ga. The maximum adsorption capacity for Ga was 55 mg/g resin with an adsorption time of 24 h, an initial Ga concentration of 500 mg/L, an adsorption temperature of 55 °C, and an initial acid concentration of 0.1 mol/L. The adsorption process of Ga was in good fit with the Langmuir isotherm and pseudo-second-order reaction kinetics model. The chemical adsorption rate was controlled by an internal diffusion mechanism. The resin had a high selectivity for Ga³⁺ with a K_d over 3600 compared with Fe²⁺, Al³⁺, K⁺, Ca²⁺, and Mg²⁺. The adsorption mechanism was found to be the ion exchange reaction between Ga and H of carboxy and hydroxyl groups. The concentration of Ga in sulfuric acid leach liquor from high-alumina fly ash achieved enrichment from 200 mg/L to 2 g/L. It is an attractive medium for large-scale Ga extraction from high-alumina fly ash. Full article

This study systematically investigated the physicochemical properties and proton exchange membrane fuel cell (PEMFC) performance of perfluorosulfonic acid (PFSA) membranes with different thicknesses, which were prepared based on the resins produced by Dongyue (China) in comparison with commercial Nafion membranes. It was found that the water uptake of Dongyue membranes is significantly higher than that of Nafion, showing a significant upward trend with the thickness increase. The ion exchange capacity (IEC) of these membranes is ca. 1 mmol·g⁻¹. Moreover, the tensile strength of the Dongyue membrane was positively correlated with the thickness and was significantly higher than that of recast Nafion. Under 80 °C, all Dongyue membranes with various thicknesses (15~45 μm) exhibited PEMFC single-cell performance superior to that of Nafion. The maximum power density is observed with a thickness of 25 μm, reaching 851.76 mW·cm⁻², which is higher than that of Nafion (635.99 mW·cm⁻²). However, the oxidative stability of the prepared Dongyue PFSA series membranes exhibits a slight deficit compared to commercial Nafion membranes. Subsequently, the modification and optimization of preparation processes can be employed to improve the mechanical and chemical stability of Dongyue PFSA membranes. Full article

As in the case with other metals, tungsten is an element with a number of uses in different fields, which is why its recovery from both primary and secondary materials continues to be of great interest. Various hydrometallurgical processes, considered as unit operations, can be used for the recovery, separation and concentration of tungsten from any source, with ease of scaling-up a potential factor when considering the best process for practical use. The present work reviewed investigations into the use of such unit operations for the recovery of tungsten which were published during 2024 and the first half of 2025. Because most if not all of these investigations were conducted on a laboratory scale, there is still much room for improvement before deciding on the best option for tungsten recovery. In all cases, however, this recovery is based on a series of steps from leaching to separation technologies (ion exchange resins, liquid–liquid extraction, etc.) to the tungsten end-product. Full article

Biodiesel, a renewable and environmentally friendly alternative to fossil fuels, has attracted significant attention due to its potential to reduce greenhouse gas emissions. However, high production costs and complex processing remain challenges. Heterogeneous catalysts have shown promise in overcoming these barriers by offering benefits, such as easy separation, reusability, low-cost raw materials, and the ability to reduce reaction times and energy consumption. This review evaluates key classes of heterogeneous catalysts, such as metal oxides, ion exchange resins, and zeolites, and their performance in transesterification and esterification processes. It highlights the importance of catalyst preparation methods, textural properties, including surface area, pore volume, and pore size, activation techniques, and critical operational parameters, like the methanol-to-oil ratio, temperature, time, catalyst loading, and reusability. The analysis reveals that catalysts supported on high surface area materials often achieve higher biodiesel yields, while metal oxides derived from natural sources provide cost-effective and sustainable options. Challenges, such as catalyst deactivation, sensitivity to feedstock composition, and variability in performance, are discussed. Overall, the findings underscore the potential of heterogeneous catalysts to enhance biodiesel production efficiency, although further optimization and standardized evaluation protocols are necessary for their broader industrial application. 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

Brine purification is an important process unit in chlor-alkali industrial plants for the production of sodium hydroxide, chlorine, and hydrogen. The membrane cell process requires ultrapure brine, which is obtained through mechanical filtration, chemical precipitation and fine polishing, and ion exchange using polymer resins. Temperature variations can lead to the degradation of the exchange properties of these resins, primarily causing a decrease in their exchange capacity, which negatively impacts the efficiency of the brine purification. After multiple ion exchange regeneration cycles, significant quantities of spent resins may be generated. These must be managed in accordance with resource efficiency and hazardous waste management to ensure the sustainability of the industrial process. In this paper, a comparative study is conducted to characterize the long-term stability of a new commercial chelating resin used in the industrial electrolysis process. The spectroscopic methods of physicochemical characterization included: scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR). The thermal behavior of the polymer resins was evaluated using the following thermogravimetric methods: thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA), while the moisture behavior was studied using dynamic vapor sorption (DVS) analysis. To assess the energy potential, the polymer resins were analyzed to determine their calorific value and overall energy content. Full article

The growing demand for therapeutic monoclonal antibodies (mAbs) has heightened the need for efficient and scalable purification strategies. A major challenge in downstream processing is the removal of antibody aggregates, which can compromise drug safety, efficacy, and regulatory compliance. This review explores the use of multimodal chromatography for aggregate separation, providing an in-depth analysis of commercially available resins and emerging adsorbent prototypes. It also examines the mechanisms of aggregate formation during bioprocessing. A comparative evaluation of conventional single-mode chromatography techniques—affinity, ion exchange, and hydrophobic interaction—is presented alongside multimodal chromatography, which integrates ion-exchange, hydrophobic, and other non-covalent interactions for enhanced aggregate clearance and process flexibility. The review primarily assesses commercial multimodal resins in terms of aggregate removal efficiency, binding capacity, and scalability. Additionally, advancements in prototype resins and multimodal membranes are discussed. Finally, the advantages, limitations, and future directions of multimodal chromatography in mAb aggregate removal are outlined. As purification demands continue to evolve, multimodal chromatography is poised to play an increasingly critical role in achieving the high purity standards required for therapeutic antibodies. Full article

LiFePO₄ (LFP) batteries are among the earliest commercialized and most discarded lithium-ion batteries. Although existing recovery technologies focus on the conversion of LiFePO₄ to Li₂CO₃, challenges associated with achieving near-full recovery and high-value products remain. This study proposes a strategy for the conversion of spent LiFePO₄ to LiF by mechanical chlorination coupled with a fluorination reaction. The optimum conditions were determined to be a ball-to-powder ratio (BPR) = 15, NH₄Cl:LFP = 3, H₂O₂ = 2.0 mL, rotation speed = 600 rpm, and grinding time = 12 h. Results showed that 97.14% Li was converted into LiCl by H₂O₂–NH₄Cl mechanical chlorination. When chlorinated intermediates were immersed in water, FePO₄ could be harvested, and 96.79% Li could be recovered as LiF with a purity of 99.50% after adding NH₄F. When Cl-functionalized renewable resin was used to exchange 99.89% F⁻, 0.63 g NH₄Cl per litre of LiF conversion residual liquid was derived. The favourable results were attributed to the ¹O₂ generated by H₂O₂, which had a strong electron affinity to break Li–O bonds and provided superior conditions for the combination of Li and Cl. During fluorination, the formation of LiF reduced the ion concentration, and the entropy decreased, contributing to the spontaneous reaction. Therefore, the proposed method paves the way for near-full recovery and high-value products of spent LiFePO₄. Full article

Cuboid packed-bed devices developed for chromatographic separation typically have shorter bed heights and larger cross-sectional areas than their equivalent cylindrical columns. These devices can be operated at low back pressures and give comparable or even better resolution than their equivalent columns. However, the bed height of a cuboid packed-bed device could potentially affect its separation performance. To examine this, three devices having 5, 10 and 19.5 mm bed heights were fabricated and packed with the same resin media. A mathematical model was first developed to predict the effect of bed height on the performance of these cuboid devices. This prediction was performed based on the residence time heterogeneity (RTH) in these devices, which increased slightly as the bed height was decreased. However, this was not likely to affect the separation efficiency very significantly. The relative performances of these three cuboid devices were then compared based on the resolution obtained during ion-exchange chromatography of multi-protein mixtures. As predicted by the mathematical model, the loss in resolution due to the decrease in bed height was relatively small (0.83 to 0.73 in binary protein separation). Also, this loss could easily be compensated for by slightly lowering the flow rate or by extending the elution gradient. The results discussed in this paper demonstrate that with cuboid packed-bed devices, the dimensions could be altered in a reasonably flexible manner without adversely affecting separation performance. Such flexibility is advantageous from the point of view of process design and optimization, which is critically important for developing large-scale processes for the purification of biologics. Full article

The disposal of low-level and intermediate-level radioactive solid waste has aroused widespread concern. In this work, the pyrolysis characterizations of simulated radioactive solid waste, cotton gloves (CG), stain removal cloths (SRC), plastic bags (PB), shoe covers (SC), and ion exchange resins (IER), were analyzed using thermogravimetric analysis, Thermogravimetric–Fourier Transform Infrared Spectrometry–Mass Spectrometry (TG-FTIR-MS) and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). The main mass loss stages of CG, SRC, PB, SC, and IER were 240–500 °C, 210–500 °C, 400–550 °C, 180–610 °C, and 25–700 °C, respectively. The average activation energies calculated by three iso-conversional methods were 184.09–211.46 kJ/mol, 172.33–180.85 kJ/mol, 264.63–268.01 kJ/mol, 150.49–184.36 kJ/mol, and 150.72–151.66 kJ/mol, respectively. Pyrolysis of CG and SRC mainly produced CO₂ and oxygenated compounds. SC generated large amounts of HCl during pyrolysis. Combined with rapid pyrolysis analysis, it was shown that CG and SRC mainly produced carbohydrates, aliphatic hydrocarbons, and aromatics. The pyrolysis products of SC mainly consisted of aliphatic hydrocarbons, aromatics, and acids. The pyrolysis products of PB were mainly olefins and alcohols. IER produced large amounts of aromatics during rapid pyrolysis. Specifically, the pyrolysis of IER generated some SO₂. This work provides a theoretical basis and data support for the treatment of mixed combustible radioactive waste. Full article