Search Results (243)

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

Water scarcity poses a formidable challenge around the world, especially in arid regions where limited availability of freshwater resources threatens both human well-being and ecosystem sustainability. Membrane-based desalination technologies offer a viable solution to address this issue by providing access to clean water. This work ultimately aims to develop a novel permselective polymeric membrane material to be employed in an electrochemical desalination system. This part of the study addresses the optimization, preparation, and characterization of a polyvinylidene difluoride (PVDF) polymeric membrane using the electrospinning technique. The membranes produced in this work were fabricated under specific operational, environmental, and material parameters. Five different additives and nano-additives, i.e., graphene oxide (GO), carbon nanotubes (CNTs), zinc oxide (ZnO), activated carbon (AC), and a zeolitic imidazolate metal–organic framework (ZIF-8), were used to modify the functionality and selectivity of the prepared PVDF membranes. Each membrane was synthesized at two different levels of additive composition, i.e., 0.18 wt.% and 0.45 wt.% of the entire PVDF polymeric solution. The physiochemical properties of the prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), zeta potential, contact angle, conductivity, porosity, and pore size distribution. Based on findings of this study, PVDF/GO membrane exhibited superior results, with an electrical conductivity of 5.611 mS/cm, an average pore size of 2.086 µm, and a surface charge of −38.33 mV. Full article

This study systematically compares the environmental and economic performance of three wastewater treatment systems: constructed wetlands (CWs), microbial fuel cells (MFCs), and their integration (CW–MFC). Lab-scale units of each system were constructed using a multi-media matrix (gravel, zeolite, and granular activated carbon), composite native wetland species (Juncus effusus, Iris sp., and Typha angustifolia), carbon-based electrodes (graphite), and standard inoculum for CW and CW–MFC. The MFC system employed carbon-based electrodes and proton-exchange membrane. The experimental design included a parallel operation of all systems treating domestic wastewater under identical hydraulic and organic loading rates. Environmental impacts were quantified across construction and operational phases using life cycle assessment (LCA) with GaBi software 9.2, employing TRACI 2021 and ReCiPe 2016 methods, while techno-economic analysis (TEA) evaluated capital and operational costs. The key results indicate that CW demonstrates the lowest global warming potential (142.26 kg CO₂-eq) due to its reliance on natural biological processes. The integrated CW–MFC system achieved enhanced pollutant removal (82.8%, 87.13%, 78.13%, and 90.3% for COD, NO₃, TN, and TP) and bioenergy generation of 2.68 kWh, balancing environmental benefits with superior treatment efficiency. In contrast, the stand-alone MFC shows higher environmental burdens, primarily due to energy-intensive material requirements and fabrication processes. TEA results highlight CW as the most cost-effective solution (USD 627/m³), with CW–MFC emerging as a competitive alternative when considering environmental benefits and operational efficiencies (USD 718/m³). This study highlights the potential of hybrid systems, such as CW–MFC, to advance sustainable wastewater treatment technologies by minimizing environmental impacts and enhancing resource recovery, supporting their broader adoption in future water management strategies. Future research should focus on optimizing materials and energy use to improve scalability and feasibility. Full article

Gel electrolytes (GEs) play a pivotal role in the advancement of lithium metal batteries by offering high energy density and enhanced rate capability. Nevertheless, their real-world application is hampered by relatively low ionic conductivity and significant interfacial resistance at room temperatures. In this work, we developed a gel electrolyte membrane (GEM) by embedding Zeolitic Imidazolate Framework-8 (ZIF-8) metal–organic frameworks (MOFs) material into a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix through UV curing. The composite membrane, with 4 wt% ZIF-8, exhibited an ionic conductivity of 1.17 × 10⁻³ S/cm, an electrochemical stability window of 4.7 V, and a lithium-ion transference number of 0.7. The test results indicate that the electrochemical performance of LFP//GEM//Li battery has an initial specific capacity of 168 mAh g⁻¹ at 0.1 C rate. At 1 C, the discharge capacity was 88 mAh g⁻¹, and at 2 C, it was 68 mAh g⁻¹. Enhanced ionic transport, improved electrochemical stability, and optimized lithium-ion migration collectively contributed to superior rate performance and prolonged cycle life. This study offers novel insights and methodological advances for next-generation lithium metal batteries technologies. Full article

An integrated hybrid system was developed, incorporating sedimentation, anaerobic digestion, biological filtration, and a two-stage hybrid subsurface flow constructed wetland, horizontal subsurface flow constructed wetland (HSSFCW) and vertical subsurface flow constructed wetland (VSSFCW), to treat rural sewage in southern Jiangsu. To optimize nitrogen and phosphorus removal, the potential of six readily accessible industrial and agricultural waste byproducts—including plastic fiber (PF), hollow brick crumbs (BC), blast furnace steel slag (BFS), a zeolite–blast furnace steel slag composite (ZBFS), zeolite (Zeo), and soil—was systematically evaluated individually as substrates in vertical subsurface flow constructed wetlands (VSSFCWs) under varying hydraulic retention times (HRTs, 0–120 h). The synergy among substrates, plants, and microbes, coupled with the effects of hydraulic retention time (HRT) on pollutant degradation performance, was clarified. Results showed BFS achieved optimal comprehensive pollutant removal efficiencies (97.1% NH₄⁺-N, 76.6% TN, 89.7% TP, 71.0% COD) at HRT = 12 h, while zeolite excelled in NH₄⁺-N/TP removal (99.5%/94.5%) and zeolite–BFS specializing in COD reduction (80.6%). System-wide microbial analysis revealed organic load (sludges from the sedimentation tank [ST] and anaerobic tanks [ATs]), substrate type, and rhizosphere effects critically shaped community structure, driving specialized pathways like sulfur autotrophic denitrification (Nitrospira) and iron-mediated phosphorus removal. Annual engineering validation demonstrated that the optimized strategy of “pretreatment unit for phosphorus control—vertical wetland for enhanced nitrogen removal” achieved stable effluent quality compliance with Grade 1-A standard for rural domestic sewage discharge after treatment facilities, without the addition of external carbon sources or exogenous microbial inoculants. This low-carbon operation and long-term stability position it as an alternative to energy-intensive activated sludge or membrane-based systems in resource-limited settings. Full article

As a rarefied metallic element, strontium (Sr) is susceptible to significant environmental radioactive contamination risks during industrial mining and refining processes. In this study, NaA molecular sieves were prepared by alkali excitation using synthetic powders, which were homogeneously blended with the polyacrylonitrile (PAN) matrix, and nanoscale TiO₂ reinforcing phases were introduced. Finally, composite separation membranes (TiO₂-NaA@PANMs) with stable adsorption properties were constructed by electrostatic spinning technology. The micro-morphology and interfacial properties were characterized by SEM, XRD, and FT-IR systems. The adsorption experiments demonstrated that the equilibrium adsorption capacity of the system for Sr²⁺ reached 55.00 mg/g at the optimized pH = 6.0, and the theoretical saturated adsorption capacity at 298 K was 80.89 mg/g. The isothermal process conformed to the Langmuir’s model of monomolecular layer adsorption, and the kinetic behavior followed the quasi-secondary kinetic equation. Following three cycles of regeneration by elution with a 0.3 mol/L sodium citrate solution, the membrane material exhibited 81.60% Sr²⁺ removal efficacy. The composite membrane passages exhibited remarkable potential for utilization in engineering applications involving the treatment of complex nuclear wastewater. Full article

In this paper, the modification of natural clinoptilolite and mordenite zeolites from Almaty using acid treatment is addressed for the purposes of improving adsorption performance and for drinking water purification. Structural chemical transformation was characterized by the use of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Scanning electron microscope (SEM) techniques. Acid treatment led to a partial dealumination that was responsible for an increase in the number of surface defects and micropores, improvement in ion exchange capacity, and selectivity toward heavy metals. Additionally, modifications greatly enhance the uptake capacities of Pb²⁺, Cd²⁺, and As³⁺. The clinoptilolite post-modification removal efficiencies reached 94%, 86%, and 84%, respectively, while mordenite zeolites achieved 95%, 90%, and 87% removal efficiencies, respectively. The enhancement of performance was related to the increase in surface area and active sites for ion exchange, verified from analysis of the Brunauer-Emmett-Teller (BET) surface area. The use of different Bhatt and Kothari methods has revealed that adsorption processes followed Langmuir isotherm models for Pb²⁺ and Cd²⁺, whereas As³⁺ adsorption was better described by the Freundlich isotherm model. However, second-order kinetics indicate that chemisorption was the dominant mechanism. Such evidence indicates spontaneity and an endothermic process, as shown from thermodynamic studies. Results showed that modified zeolites indeed had a high degree of reusability, with over 80% of the adsorption capacity retained even after five cycles. Acid-modified zeolites can provide cheaper, greener methods of purification, generating only negligible secondary waste when compared to conventional methods of water purification, for example, activated carbon and membrane filtration. Results from this study proved that modified clinoptilolite and mordenite zeolites have the potential for sustainable heavy metal treatment in drinking water purification systems. Full article

This study explores the fabrication, structural characteristics, and performance of an innovative porous geopolymer membrane made from waste natural zeolite powder for Pb(II) removal, with potential applications in wastewater treatment. A hybrid geopolymer membrane incorporating polyvinyl acetate (PVAc) (10, 20, and 30 wt.%) was synthesized and thermally treated at 300 °C to achieve a controlled porous architecture. Characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), revealed the disappearance of characteristic C=O and C-H stretching bands (~1730 cm⁻¹ and ~2900 cm⁻¹, respectively), confirming the full degradation of PVAc. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) indicated a total mass loss of approximately 14.5% for the sample with PVAc 20 wt.%, corresponding to PVAc decomposition and water loss. Energy-dispersive spectroscopy (EDS) elemental mapping showed the absence of carbon residues post-annealing, further validating complete PVAc removal. X-ray diffraction (XRD) provided insight into the crystalline phases of the raw zeolite and geopolymer structure. Once PVAc removal was confirmed, the second phase of characterization assessed the membrane’s mechanical properties and filtration performance. The thermally treated membrane, with a thickness of 2.27 mm, exhibited enhanced mechanical properties, measured with a nano-indenter, showing a hardness of 1.8 GPa and an elastic modulus of 46.7 GPa, indicating improved structural integrity. Scanning electron microscopy (SEM) revealed a well-defined porous network. Filtration performance was evaluated using a laboratory-scale dead-end setup for Pb(II) removal. The optimal PVAc concentration was determined to be 20 wt.%, resulting in a permeation rate of 78.5 L/(m²·h) and an 87% rejection rate at an initial Pb(II) concentration of 50 ppm. With increasing Pb(II) concentrations, the flux rates declined across all membranes, while maximum rejection was achieved at 200 ppm. FTIR and EDS analyses confirmed Pb(II) adsorption onto the zeolite-based geopolymer matrix, with elemental mapping showing a uniform Pb(II) distribution across the membrane surface. The next step is to evaluate the membrane’s performance in a multi-cation water treatment environment, assessing the sorption kinetics and its selectivity and efficiency in removing various heavy metal contaminants from complex wastewater systems. Full article

Fructooligosaccharides (FOSs) are carbohydrates of high nutritional value with various prebiotic properties. Optimizing their production process is of significant interest for expanding commercial-scale production. This review discusses the properties and potential applications of FOSs, addressing production challenges and providing an economic market analysis. Bibliometric analysis of data concerning the functional properties, production, purification, and applications of FOSs revealed an over 87% increase in the number of worldwide publications from 2012 to 2022, rising from 88 to 165. Furthermore, contributions from ninety-three countries were identified up to 2024, with Brazil ranking first, with 326 publications. Furthermore, Aureobasidium sp. and Aspergillus sp. have shown the best results for FOS production, with reported conversion in the order of 0.66 g FOS/g sucrose. Nevertheless, the formation of by-products or co-products requiring separation from the medium remains a challenge. Activated carbon, cation exchange resins, and zeolites are highlighted as key adsorbents, with the adsorption process achieving FOS purity exceeding 90%. Furthermore, membrane technology is identified as a more efficient and promising separation method. Addressing these limitations will facilitate the further expansion of the growing global FOS market, promoting a sustainable approach and their integration with biorefineries, which can enable the development of a wider range of value-added products. Full article

Simulations of the Brownian dynamics of diffusing particles in complex environments provide important information about the characteristics of the medium and the properties of biological processes. Notable examples include the diffusion of ions and macromolecular solutes through channels of varying cross-section, such as pores in biological membranes, living tissues, zeolites, carbon nanotubes, and synthetic porous materials. In these systems, the observed diffusion can exhibit anomalous behavior characterized by a nonlinear increase in the mean squared displacement. In this article, we present a toy model of the diffusion of rod-shaped particles through a narrowing, conical pore with a trapezoidal longitudinal cross-section. Particles of different sizes undergo a random walk due to interactions with the environment (modeled as noise). We study how the diffusion properties change with particle size as a function of pore width. The numerical analysis of diffusion-driven transport through narrowing conical channels reveals its effective subdiffusive, i.e., anomalous, character. Full article

Silicalite-2 membranes were successfully prepared on tubular α-Al₂O₃ supports by secondary hydrothermal synthesis, and the pervaporation performance of the membrane was evaluated by separation of a 5 wt% ethanol/H₂O mixture at 60 °C. The effects of templating agent content, water–silicon ratio and crystallization time on the separation performance of Silicalite-2 membranes were investigated. When the TBAOH/SiO₂ and H₂O/SiO₂ molar ratios of the precursor synthesis solution were 0.2 and 120, a dense Silicalite-2 membrane could be prepared on the surface of the tubular α-Al₂O₃ support after 72 h. The silane coupling agent was utilized to treat the Silicalite-2 membranes, and the effects of silane coupling agent dosage on their properties were also explored. The pervaporation performance of the Silicalite-2 membrane was greatly improved with a 5.7 wt% trimethylchlorosilane (TMCS) solution and the flux and separation factor of the membrane reached 1.75 kg·m⁻²·h⁻¹ and 22 for separation of 5 wt% EtOH/H₂O at 60 °C, respectively. Full article

With the growth of the population and the development of industry and agriculture, water resources are experiencing contamination by numerous pollutants, posing a threat to the aquatic environment and human health. Zeolitic imidazolate framework (ZIF) membranes, as a solution for water pollutant treatment, not only have the advantages of high efficiency adsorption, good selectivity, stability, and easy recyclability, but they also can be modified or derivatized through surface functionalization, compositing, or structural tuning, which can further endow the membranes with other functions, such as catalysis and degradation. In order to improve the performance of ZIF membranes, it is crucial to select suitable preparation methods to optimize the microstructure of the membranes and to improve the separation performance and stability of the membranes. This review systematically summarizes the current major preparation methods of ZIF membranes and their respective advantages and disadvantages, providing an overview of the applications of ZIF membranes in the treatment of water pollutants, such as dyes, antibiotics, and heavy metal ions. Future development prospects are also discussed, with the expectation that future research will optimize the synthesis methods to enhance the mechanical strength of the membranes and improve their selectivity, permeability, and anti-fouling properties through modifications or functionalization. This article is expected to provide theoretical support for the application of ZIF membranes in water pollution treatment. Full article

The development of functional materials and the use of nanotechnology are ongoing projects. These fields are closely linked, but there is a need to combine them more actively. Nanoarchitectonics, a concept that comes after nanotechnology, is ready to do this. Among the related research efforts, research into creating functional materials through the formation of thin layers on surfaces, molecular membranes, and multilayer structures of these materials have a lot of implications. Layered structures are especially important as a key part of nanoarchitectonics. The diversity of the components and materials used in layer-by-layer (LbL) assemblies is a notable feature. Examples of LbL assemblies introduced in this review article include quantum dots, nanoparticles, nanocrystals, nanowires, nanotubes, g-C₃N₄, graphene oxide, MXene, nanosheets, zeolites, nanoporous materials, sol–gel materials, layered double hydroxides, metal–organic frameworks, covalent organic frameworks, conducting polymers, dyes, DNAs, polysaccharides, nanocelluloses, peptides, proteins, lipid bilayers, photosystems, viruses, living cells, and tissues. These examples of LbL assembly show how useful and versatile it is. Finally, this review will consider future challenges in layer-by-layer nanoarchitectonics. Full article

The pervaporation properties of membranes based on comb-like polysiloxanes when C₂-C₄ alcohols are removed from water were studied for the first time. It was established that membranes based on comb-like polysiloxanes with linear aliphatic and organosilicon substituents have increased permeability selectivity for C₃₊ alcohols. The obtained results were interpreted from the point of view of the solubility of the components of the separated mixture in polysiloxanes. It was shown that membranes based on polysiloxanes with linear substituents have increased butanol/water permeability selectivity (2.5–3.7). The achieved selectivity values correspond to the level of highly selective zeolite membranes, which allows for a reduction in energy consumption for the pervaporation removal of butanol by more than two times. Full article