Search Results (720)

The development of anode-free sodium metal batteries (AFSMBs) offers a promising pathway to achieve ultrahigh energy density and cost efficiency inherent to conventional sodium ion/metal batteries. However, irreversible Na plating/stripping and dendritic growth remain critical barriers. Herein, we demonstrate that separator engineering is a pivotal strategy for stabilizing AFSMBs. Through systematic evaluation of four separators—2500 separator (PP), 2325 separator (PP/PE/PP), glass fiber (GF), and an Al₂O₃-coated PE membrane, we reveal that the Al₂O₃-coated separator uniquely enables exceptional interfacial kinetics and morphological control. Na||Na symmetric cells with Al₂O₃ coated separator exhibit ultralow polarization (4.5 mV) and the highest exchange current density (1.77 × 10⁻² mA cm⁻²), while the anode-free AlC-NFPP full cells retain 91.6% capacity after 150 cycles at 2C. Specifically, the Al₂O₃ coating homogenizes Na⁺ flux, promotes dense and planar Na deposition, and facilitates near-complete stripping with minimal “dead Na”. This work establishes ceramic-functionalized separators as essential enablers of practical high-energy AFSMBs. Full article

Metal–Organic Frameworks (MOFs) have emerged as advanced porous crystalline materials due to their highly ordered structures, ultra-high surface areas, fine-tunable pore sizes, and massive chemical diversity. These features, arising from the coordination between an almost unlimited number of metal ions/clusters and organic linkers, have resulted in significant interest in MOFs for applications in gas storage, catalysis, sensing, energy, and biomedicine. Beyond their stand-alone properties and applications, recent research has increasingly explored the integration of MOFs with other substrates, particularly electrodes, polymeric thin films, and glass surfaces, to create synergistic effects that enhance material performance and broaden application potential. Coating MOFs onto these substrates can yield significant benefits, including, but not limited to, improved sensitivity and selectivity in electrochemical sensors, enhanced mechanical and separation properties in membranes, and multifunctional coatings for optical and environmental applications. This review provides a comprehensive and up-to-date summary of recent advances (primarily from the past 3–5 years) in MOF coating techniques, including layer-by-layer assembly, in situ growth, and electrochemical deposition. This is followed by a discussion of the representative applications arising from MOF-substrate coating and an outline of key challenges and future directions in this rapidly evolving field. This article aims to serve as a focused reference point for researchers interested in both fundamental strategies and applied developments in MOF surface coatings. 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

A metal-ion-free method was developed to prepare κ-carrageenan/cellulose hydrogel beads for efficient cationic dye removal. The beads were fabricated using a mixture of 1-ethyl-3-methylimidazolium acetate and N,N-dimethylformamide as the solvent system, followed by aqueous ethanol-induced phase separation. This process eliminated the need for metal-ion crosslinkers, which typically neutralize anionic sulfate groups in κ-carrageenan, thereby preserving a high density of accessible binding sites. The resulting beads formed robust interpenetrating polymer networks. The initial swelling ratio reached up to 28.3 g/g, and even after drying, the adsorption capacity remained over 50% of the original. The maximum adsorption capacity for crystal violet was 241 mg/g, increasing proportionally with κ-carrageenan content due to the higher surface concentration of anionic sulfate groups. Kinetic and isotherm analyses revealed pseudo-second-order and Langmuir-type monolayer adsorption, respectively, while thermodynamic parameters indicated that the process was spontaneous and exothermic. The beads retained structural integrity and adsorption performance across pH 3–9 and maintained over 90% of their capacity after five reuse cycles. These findings demonstrate that κ-carrageenan/cellulose hydrogel beads prepared via a metal-ion-free strategy offer a sustainable and effective platform for cationic dye removal from wastewater, with potential for heavy metal ion adsorption. Full article

Accelerated industrialization and surging energy demands have led to continuously rising atmospheric CO₂ concentrations. Developing sustainable methods to reduce atmospheric CO₂ levels is crucial for achieving carbon neutrality. Concurrently, the rapid development of new energy vehicles has driven a significant increase in demand for lithium-ion batteries (LIBs), which are now approaching an end-of-life peak. Efficient recycling of valuable metals from spent LIBs represents a critical challenge. This study employs conventional hydrometallurgical processing to recover valuable metals from spent LIBs. Subsequently, Ni-doped Co₃O₄ (Ni:Co₃O₄) supported on the natural mineral attapulgite (ATP) was synthesized via a sol–gel method. The incorporation of a small amount of Ni into the Co₃O₄ lattice generates oxygen vacancies, inducing a localized surface plasmon resonance (LSPR) effect, which significantly enhances charge carrier transport and separation efficiency. During the photocatalytic reduction of CO₂, the primary product CO generated by the Ni:Co₃O₄/ATP composite achieved a high production rate of 30.1 μmol·g⁻¹·h⁻¹. Furthermore, the composite maintains robust catalytic activity even after five consecutive reaction cycles. 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

This study presents the development of a novel Cu–Co–O-codoped graphitic carbon nitride (g-C₃N₄) catalyst for efficient peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX) in aqueous environments. The synthesized Cu–Co–O-g-C₃N₄ catalyst demonstrated exceptional catalytic performance, achieving 90% SMX removal within 10 min—significantly outperforming pristine g-C₃N₄ (14%) and O-doped g-C₃N₄ (22%)—with a reaction rate constant of 0.63 min⁻¹. The superior activity was attributed to the synergistic effects of Cu-Co bimetallic doping and oxygen incorporation, which enhanced the active sites, stabilized metal ions, and minimized leaching. Mechanistic studies revealed a dual-pathway degradation process: (1) a radical pathway dominated by sulfate radicals (SO₄•⁻) and (2) a non-radical pathway driven by singlet oxygen (¹O₂), with the latter identified as the dominant species through quenching experiments. The catalyst exhibited broad pH adaptability and optimal performance at neutral to alkaline conditions. Characterization techniques (XRD, FTIR, XPS) confirmed successful doping and revealed that oxygen incorporation modified the electronic structure of g-C₃N₄, improving charge carrier separation. This work provides a sustainable strategy for antibiotic removal, addressing key challenges in advanced oxidation processes (AOPs), and highlights the potential of multi-heteroatom-doped carbon nitride catalysts for water purification. 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

The growing demand for high-energy, safe, and sustainable lithium-ion batteries has increased interest in nickel-rich cathode materials and solid-state electrolytes. This study presents a scalable wet-processing method for fabricating composite cathodes for all-solid-state batteries. The cathodes studied herein are high-nickel LiNi_0.90Mn_0.05Co_0.05O₂, NMC955, the sulfide-based electrolyte Li₆PS₅Cl, and alternative binders—polyvinyl alcohol (PVA) and polyisobutylene (PIB)—dispersed in toluene, a non-polar solvent compatible with the electrolyte. After fabrication, the cathodes were characterized using SEM/EDX, sheet resistance, and Hall effect measurements. Electrochemical tests were additionally performed in all-solid-state battery half-cells comprising the synthesized cathodes, lithium metal anodes, and Li₆PS₅Cl as the separator and electrolyte. The results show that both PIB and PVA formulations yielded conductive cathodes with stable microstructures and uniform particle distribution. Electrochemical characterization exposed that the PVA-based cathode outperformed the PIB-based counterpart, achieving the theoretical capacity of 192 mAh·g⁻¹ even at 1C, whereas the PIB cathode reached a maximum capacity of 145 mAh.g⁻¹ at C/40. Post-mortem analysis confirmed the structural integrity of the cathodes. These findings demonstrate the viability of NMC955 as a high-capacity cathode material compatible with solid-state systems. Full article

In recent years, membranes have found extensive applications, primarily in wastewater purification and food packaging. However, petroleum-based membranes can be detrimental to the environment. For this reason, extensive studies are being conducted to identify environmentally friendly substitutes for the materials used in membrane composition. Among these materials, polylactic acid (PLA) and poly(3-hydroxybutyrate) (PHB) are two bio-sourced and biodegradable polymers that can be derived from lignocellulosic waste. These polymers also possess suitable characteristics, such as thermal resistance and mechanical strength, which make them potential candidates for replacing conventional plastics. This study provides an overview of recent advances in the production of PLA and PHB, with a focus on their extraction from lignocellulosic biomass, as well as the recent applications of these two biodegradable polymers as sustainable materials in membrane manufacturing. The advantages and limitations of membranes produced from these materials are also summarized. Lastly, an analysis of future trends is provided concerning new sources, production possibilities, and potential applications in water treatment (mainly for metal ions separation), gas separation, oil–water separation, medical applications, drug release control, and food packaging. Full article

Nanocellulose-based composite aerogels have the advantages of high porosity, biodegradability, and biocompatibility, with wide applications in many fields, such as adsorption, separation, energy storage, and heat insulation. In this study, a nanocellulose-based composite aerogel (NCA) was prepared using the one-pot method with cellulose nanofibrils (CNFs), tannic acid (TA), and polyvinyl alcohol (PVA) as raw materials. The adsorption behaviors of Pb²⁺, Cd²⁺, and Cu²⁺ were also studied. FT-IR analysis confirmed that TA successfully solidified on the nanocellulose, while SEM analysis revealed that the prepared NCA exhibited significantly higher porosity compared with the cellulose nanofibril-only aerogel. The results of the adsorption experiment demonstrated that the adsorption behavior of heavy metal ions using the prepared NCA followed pseudo-second-order kinetics. The adsorption isotherms fit well with the Langmuir adsorption model, indicating that the process of aerogels adsorbing heavy metal ions is that of monolayer adsorption. Under conditions of pH 6 and an initial heavy metal ion concentration of 100 mg/L, the maximum adsorption capacity calculated for the prepared NCA was up to 196.850 mg/g, 181.488 mg/g, and 151.515 mg/g for Cu²⁺, Cd²⁺, and Pb²⁺, respectively. Furthermore, the prepared NCA exhibited excellent reusability, with more than 90% efficiency retained after three cycles. NCAs have the potential to become an efficient material for absorbing heavy metal ions in water. Full article

To ensure the sustainable use of limited resources, it is essential to establish selective and efficient recycling technologies for platinum group metals (PGMs). This study focused on the selective precipitation-based separation of Pt(IV) from hydrochloric acid (HCl) solutions in the presence of various metal ions, using trans-1,4-bis(aminomethyl)cyclohexane (BACT) as a precipitating agent. By using BACT, we succeeded in the selective separation of Pt(IV) by precipitation from HCl solutions containing Pd(II) and Rh(III). Notably, selective and efficient recovery of Pt(IV) was accomplished across various HCl concentrations, with a small amount of BACT and within a short shaking time. To evaluate the practical applicability of the method, Pt(IV) was recovered and purified from the HCl leachate of spent automotive exhaust gas purification catalysts using BACT. As a result, a high Pt recovery of 95.6% and a high purity of 99.3% were achieved. Although Pt(IV) was recovered as a precipitate containing BACT, it was found that Pt black could be readily obtained by dissolving the precipitate in HCl solution followed by reduction with sodium borohydride. Detailed structural analysis of the Pt(IV)-containing precipitate revealed that it is an ionic crystal composed of [PtCl₆]²⁻ and protonated BACT. The selective formation of this ionic crystal in HCl solution, along with its stability under such conditions, is the key to the selective recovery of Pt(IV) using BACT. Full article

In this study, we report the synthesis and characterization of a novel NH₂-MIL-101(Fe) magnetic composite, developed via in situ formation of NH₂-MIL-101(Fe) in the presence of Fe₃O₄ nanoparticles embedded within a chloropropyl-modified mesoporous silica layer. This hybrid composite retains the high adsorption capacity of NH₂-MIL-101(Fe) while benefiting from the easy magnetic separation enabled by Fe₃O₄ nanoparticles. The mesoporous silica forms a protective porous coating around the magnetic nanoparticles, significantly enhancing its chemical stability and preventing clumping. Beyond protection, the mesoporous silica layer provides a high-surface-area scaffold that promotes the uniform in situ growth of NH₂-MIL-101(Fe). Functionalization of the silica surface with chloride groups enables strong electrostatic interactions between the magnetic component and metal organic framework (MOF), ensuring a homogeneous and stable hybrid structure. The new composite’s capacity to remove Pb(II) and Cd(II) ions from aqueous solutions was systematically investigated. The adsorption data showed a good fit with the Langmuir isotherm model for both ions, the maximum adsorption capacities calculated being 214.6 mg g⁻¹ for Pb(II) and 181.6 mg g⁻¹ Cd(II). Furthermore, the kinetic behavior of the adsorption process was accurately described by the pseudo-second-order model. These findings confirm the effectiveness of this composite for the removal of Pb(II) and Cd(II) ions from aqueous solutions, demonstrating its potential as an efficient material for environmental remediation. The combination of magnetic recovery, high adsorption capacity, and stability makes this novel composite a promising candidate for heavy metal removal applications in water treatment processes. Full article

The conventional spent lithium-ion batteries (LIBs) recycling method suffers from complex processes and excessive chemical consumption. Hence, this study proposes an electrochemical strategy for achieving reductant-free leaching of high-valence transition metals and efficient separation of valuable components from spent cathode sheets (CSs). An innovatively designed sandwich-structured electrochemical reactor achieved efficient reductive dissolution of cathode materials (CMs) while maintaining the structural integrity of aluminum (Al) foils in a dilute sulfuric acid system. Optimized current enabled leaching efficiencies exceeding 93% for lithium (Li), cobalt (Co), manganese (Mn), and nickel (Ni), with 88% metallic Al foil recovery via cathodic protection. Multi-scale characterization systematically elucidated metal valence evolution and interfacial reaction mechanisms, validating the technology’s tripartite innovation: simultaneous high metal extraction efficiency, high value-added Al foil recovery, and organic removal through single-step electrochemical treatment. The process synergized the dissolution of CM particles and hydrogen bubble-induced physical liberation to achieve clean separation of polyvinylidene difluoride (PVDF) and carbon black (CB) layers from Al foil substrates. This method eliminates crushing pretreatment, high-temperature reduction, and any other reductant consumption, establishing an environmentally friendly and efficient method of comprehensive recycling of battery materials. Full article