Fabrication of sustainable organic solvent nanofiltration membranes using cellulose–chitosan biopolymer blends

Biodegradable aminated alginate-chitosan porous polymer for efficient indoor formaldehyde capture

Formaldehyde, even at low concentrations, poses a significant indoor pollutant risk, underscoring the need for efficient and sustainable sorbents. This study introduces a novel, multifunctional, and fully biodegradable adsorbent derived from waste shrimp shells. The shells were converted into soluble chitosan, which was then physically crosslinked with branched amine-modified alginate, resulting in a porous biuret-modified alginate/chitosan (BCC) polymer. BCC, with a 6 wt% biuret content, demonstrated exceptional adsorption performance for low-concentration formaldehyde, achieving a capacity of 1.97 mg·g-1-159% higher than alginate and 149 % greater than activated carbon. The adsorption kinetics followed the pseudo-second-order model, and the Sips isotherm model suggested a chemical adsorption-dominated mechanism, with physical adsorption acting as a supplementary process. Additionally, BCC exhibited excellent reusability, maintaining high adsorption efficiency after four regeneration cycles, and incorporated a colorimetric signaling function, with a detection threshold of 0.07 mg·m-3 and a sensitivity of 0.02 mg·m-3. These findings provide valuable insights and a theoretical basis for developing effective, safe, and environmentally friendly formaldehyde adsorbents.

Bioderived Polyarylester Nanofilms from Innovative Plant Materials for High-Efficient Organic Solvent Nanofiltration

The successful realization of thin film composite (TFC) organic solvent nanofiltration (OSN) membranes with high permeability and small solute selectivity for solute-solute separation to purify drugs in complex solution environments remains challenging in the pharmaceutical industry. Here, we present the preparation of high cross-linked TFC OSN membranes via interfacial polymerization (IP) utilizing phlorotannin, a plant-derived biomass phenolic compound, as a promising aqueous phase monomer. Benefiting from the presence of multiple cross-linking sites and twisted rigid structure in phlorotannin, nanofiltration membranes with excellent molecular selectivity and solvent permeability were successfully fabricated. This allowed for straightforward separation and purification of active pharmaceutical ingredients from intermediates. The membranes demonstrated remarkable stability over extended periods of operation and adaptability to a diverse array of solvent environments, making them a highly promising option for use in fine chemicals, biopharmaceuticals, and other fields.

Furandicarboxylic Acid (FDCA): Electrosynthesis and Its Facile Recovery From Polyethylene Furanoate (PEF) via Depolymerization

Replacing fossil fuels with renewable, bio-based alternatives is inevitable for the modern chemical industry, in line with the 12 principles of green chemistry. 2,5-Furandicarboxylic acid (FDCA) is a promising platform molecule that can be derived from 5-hydroxymethyl furfural (HMF) via sustainable electrochemical oxidation. Herein, we demonstrate TEMPO-mediated electrooxidation of HMF to FDCA in ElectraSyn 2.0 using inexpensive commercially available electrodes: graphite anode and stainless-steel cathode, thereby avoiding the often cumbersome electrode preparation. Key parameters such as concentration of HMF, KOH, and catalyst loading were optimized by experimental design. Under the optimized conditions, using only a low amount of TEMPO (5 mol %), high yield and Faradaic efficiency of 96 % were achieved within 2.5 h. Moreover, since FDCA is a monomer of the bio-based poly(ethylene furanoate), PEF, we aimed to investigate its recovery by depolymerization, which could be of paramount importance in the circular economy of the FDCA. For this, a new polar aprotic solvent, methyl sesamol (MeSesamol), was used, allowing the facile depolymerization of PEF at room temperature with high monomer yields (up to 85 %), while the cosolvent MeSesamol was recycled with high efficiency (95-100 %) over five reaction cycles.

Polymeric Membranes for Liquid Separation: Innovations in Materials, Fabrication, and Industrial Applications

Polymeric membranes have emerged as a versatile and efficient liquid separation technology, addressing the growing demand for sustainable, high-performance separation processes in various industrial sectors. This review offers an in-depth analysis of recent developments in polymeric membrane technology, focusing on materials' advancements, innovative fabrication methods, and strategies for improving performance. We discuss the underlying principles of membrane separation, selecting suitable polymers, and integrating novel materials, such as mixed-matrix and composite membranes, to enhance selectivity, permeability, and antifouling properties. The article also highlights the challenges and limitations associated with polymeric membranes, including stability, fouling, and scalability, and explores potential solutions to overcome these obstacles. This review aims to guide the development of next-generation polymeric membranes for efficient and sustainable liquid separation by offering a detailed analysis of current research and future directions.

Biobased Interpenetrating Polymer Network Membranes for Sustainable Molecular Sieving

There is an urgent need for sustainable alternatives to fossil-based polymer materials. Through nanodomain engineering, we developed, without using toxic cross-linking agents, interpenetrating biopolymer network membranes from natural compounds that have opposing polarity in water. Agarose and natural rubber latex were consecutively self-assembled and self-cross-linked to form patchlike nanodomains. Both nano-Fourier transform infrared (nano-FTIR) spectroscopy and computational methods revealed the biopolymers' molecular-level entanglement. The membranes exhibited excellent solvent resistance and offered tunable molecular sieving. We demonstrated control over separation performance in the range of 227-623 g mol-1 via two methodologies: adjusting the molecular composition of the membranes and activating them in water. A carcinogenic impurity at a concentration of 5 ppm, which corresponds to the threshold of toxicological concern, was successfully purged at a negligible 0.56% pharmaceutical loss. The biodegradable nature of the membranes enables an environmentally friendly end-of-life phase; therefore, the membranes have a sustainable lifecycle from cradle to grave.

Recent advances in the fabrication of organic solvent nanofiltration membranes using covalent/metal organic frameworks

Organic solvent nanofiltration (OSN) has evolved as a vital technological frontier with paramount significance in the separation and purification of organic solvents. Its implication is particularly prominent in industries such as pharmaceuticals, petrochemicals, and environmental remediation. This comprehensive review, meticulously navigates through the current state of research in OSN membranes, unveiling both the critical challenges and promising opportunities that beckon further exploration. The central focus of this review is on the unique utilization of covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) in OSN membrane design, leveraging their distinctive structural attributes-tunable porosity, robust chemical stability, and molecular sieving capabilities. These qualities position them as exceptional candidates for crafting membranes tailored to the intricacies of organic solvent environments. Our investigation extends into the fundamental principles that render COFs and MOFs adept in OSN applications, dissecting their varied fabrication methods while offering insights into the advantages and limitations of each. Moreover, we address environmental and sustainability considerations in the use of COF and MOF-based OSN membranes. Furthermore, we meticulously present the latest advancements and innovations in this burgeoning field, charting a course toward potential future directions and emerging research areas. By underscoring the challenges awaiting exploration, this review not only provides a panoramic view of the current OSN landscape but also lays the groundwork for the evolution of efficient and sustainable OSN technologies, specifically harnessing the unique attributes of COFs and MOFs.

A surface multiple imprinting layers membrane with well-oriented recognition sites for selective separation of chlorogenic acid from Ficus carica L

Chlorogenic acid (CGA), known as an important natural antioxidative compound in Ficus carica L, has valuable application prospects on health food, functional food, nutrition and dietary formulations. In this study, a surface multiple imprinting layers membrane (SMILM) was developed and applied to separate CGA from F. carica. Two different imprinting layers were integrated onto the membrane surface in sequence. The first imprinting layer was formed by dopamine polymerization and the second imprinting layer was fabricated by atom transfer radical polymerization (ATRP) and boronate affinity. The prepared SMILM with well-oriented multiple recognition sites exhibited high adsorption capacity (52.08 mg·g-1 in 60 min) for CGA and specific selectivity with imprinting factor (IF) of 3.06. Furthermore, the recognition mechanism of SMILM was clarified by molecular simulation and NMR. The SMILM was successfully applied to separate CGA from the fruits, peels and leaves of F. carica with recoveries of 90.22, 83.31 and 84.95 %, respectively.

Immobilization of BoPAL3 Phenylalanine Ammonia-Lyase on Electrospun Nanofibrous Membranes of Polyvinyl Alcohol/Nylon 6/Chitosan Crosslinked with Dextran Polyaldehyde

Phenylalanine ammonia-lyase (PAL, EC 4.3.1.24) is common in plants and catalyzes the formation of trans-cinnamic acid and ammonia via phenylalanine deamination. Recombinant Bambusa oldhamii BoPAL3 protein expressed in Escherichia coli was immobilized on an electrospun nanofibrous membrane using dextran polyaldehyde as a crosslinker. The immobilized BoPAL3 protein exhibited comparable kinetic properties with the free BoPAL3 protein and could be recycled for six consecutive cycles compared with the free BoPAL3 protein. The residual activity of the immobilized BoPAL3 protein was 84% after 30 days of storage at 4 °C, whereas the free BoPAL3 protein retained 56% residual activity in the same storage conditions. Furthermore, the resistance of the immobilized BoPAL3 protein to chemical denaturants was greatly increased. Therefore, the BoPAL3 protein can be immobilized using the natural dextran polyaldehyde crosslinker in place of the conventional chemical crosslinker. Nanofibrous membranes made from polyvinyl alcohol (PVA), nylon 6, and chitosan (CS) are incredibly stable and useful for future industrial applications.

Resource recovery from RO concentrate using nanofiltration: Impact of active layer thickness on performance

Modelling the removal of monovalent and divalent ions from seawater via nanofiltration is crucial for pre-treatment in seawater reverse osmosis systems. Effective separation of divalent ions through nanofiltration and allowing the permeate containing only monovalent ions to pass through the reverse osmosis system produces pure NaCl salt from the concentrate. However, the Donnan steric pore model and dielectric exclusion assume a uniformly distributed cylinder pore morphology, which is not representative of the actual membrane structure. This study analyzed the impact of membrane thickness on neutral solute removal and investigated the effect of two different methods for calculating the Peclet number on rejection rates of monovalent and divalent salts. Results show that membrane thickness has a significant effect on rejection rates, particularly for uncharged solutes in the range of 0.5-0.7 solute radius to membrane pore size ratio. Operating pressures above 10 bar favour the use of effective active layer thickness over the membrane pore size to calculate the Peclet number. At low pressures, using the effective active layer can lead to overestimation of monovalent salt rejection and underestimation of divalent salt rejection. This study highlights the importance of appropriate Peclet number calculation methods based on applied pressure when modelling membrane separation performance.

Removal of pharmaceutically active compounds from water sources using nanofiltration and reverse osmosis membranes: Comparison of removal efficiencies and in-depth analysis of rejection mechanisms

Trace organic compounds from effluent streams are not completely removed by conventional purification techniques and hence, contaminating groundwater sources. Herein, we report the removal efficiency and rejection mechanisms of three common pharmaceutically active compounds (PhACs); caffeine (CFN), omeprazole (OMZ), and sulfamethoxazole (SMX), using commercial nanofiltration (NF) and reverse osmosis (RO) membranes with different surface characteristics. The RO membranes showed near-complete removal of all PhACs with rejection rates >99%. On the other hand, retention capabilities for the NF membranes varied and were influenced by the characteristics of the PhACs, membranes, and the feed solution. In general, during long-term testing, the rejection did not show much variation and followed a trend compatible with the size exclusion (steric hindrance) mechanism. When a real matrix was used, the rejection of CFN by the more tight NF membranes, HL TFC and NFW decreased by ∼10%, whereas the removal of SMX by the loose NF membrane, XN45, increased by the same ratio. In short-term testing, the rejection of negatively charged SMX increased significantly (∼20-40%) at a higher pH of ∼8 and in the presence of salts. Fouling by the PhACs was more severe on the high-flux NF membranes, HL TFC and XN45, as witnessed by the significant change in Contact angle (CA) values (∼25-50°) as well as the flux decline (∼15%) during long-term testing. To summarize, the removal of PhACs by membranes is a complex phenomenon and depends upon a combination of several factors.

Bio-Based Polymeric Membranes: Development and Environmental Applications

Nowadays, membrane technology is an efficient process for separating compounds with minimal structural abrasion; however, the manufacture of membranes still has several drawbacks to being profitable and competitive commercially under an environmentally friendly approach. In this sense, this review focuses on bio-based polymeric membranes as an alternative to solve the environmental concern caused by the use of polymeric materials of fossil origin. The fabrication of bio-based polymeric membranes is explained through a general description of elements such as the selection of bio-based polymers, the preparation methods, the usefulness of additives, the search for green solvents, and the characterization of the membranes. The advantages and disadvantages of bio-based polymeric membranes are discussed, and the application of bio-based membranes to recover organic and inorganic contaminants is also discussed.

The Effect of Non-Solvent Nature on the Rheological Properties of Cellulose Solution in Diluted Ionic Liquid and Performance of Nanofiltration Membranes

The weak point of ionic liquids is their high viscosity, limiting the maximum polymer concentration in the forming solutions. A low-viscous co-solvent can reduce viscosity, but cellulose has none. This study demonstrates that dimethyl sulfoxide (DMSO), being non-solvent for cellulose, can act as a nominal co-solvent to improve its processing into a nanofiltration membrane by phase inversion. A study of the rheology of cellulose solutions in diluted ionic liquids ([EMIM]Ac, [EMIM]Cl, and [BMIM]Ac) containing up to 75% DMSO showed the possibility of decreasing the viscosity by up to 50 times while keeping the same cellulose concentration. Surprisingly, typical cellulose non-solvents (water, methanol, ethanol, and isopropanol) behave similarly, reducing the viscosity at low doses but causing structuring of the cellulose solution and its phase separation at high concentrations. According to laser interferometry, the nature of these non-solvents affects the mass transfer direction relative to the forming membrane and the substance interdiffusion rate, which increases by four-fold when passing from isopropanol to methanol or water. Examination of the nanofiltration characteristics of the obtained membranes showed that the dilution of ionic liquid enhances the rejection without changing the permeability, while the transition to alcohols increases the permeability while maintaining the rejection.

Separation of C18 Fatty Acid Esters and Fatty Acids Derived from Vegetable Oils Using Nanometer-Sized Covalent Organic Frameworks Incorporated in Polyepoxy Membranes

Fatty acids (FAs) and FA methyl esters (FAMEs) are easily isolated from vegetable oil and are important starting materials for the chemical industry to produce commercial products that are green, biorenewable, and nontoxic. A challenge in these applications is that mixtures of five or more FAs and FAMEs are isolated from a vegetable oil source, and methods to separate these mixtures are decades old and have increasingly high costs associated with the production of high-purity single-component FAs or FAMEs. We developed a method to separate these mixtures using mixed matrix membranes containing nanometer-sized covalent organic frameworks. The 2D, crystalline COFs possessed narrow distributions of pore sizes of 1.3, 1.8, 2.3, and 3.4 nm that separated FAs and FAMEs based on their degrees of unsaturation. The COFs were synthesized, characterized, and then encapsulated at 10 or 20% by weight into a prepolymer of epoxy that was then fully cured. For all mixed matrix membranes, as the degree of unsaturation increased, the FAs or FAMEs had a slower flux. The largest difference in flux was obtained for a COF/epoxy membrane with a pore size of 1.8 nm, and methyl stearate had a 5.9× faster flux than methyl linolenate. These are the first membranes that can separate the important C18 FAs and FAMEs found in vegetable oil.

Development of cell adhesive and inherently antibacterial polyvinyl alcohol/polyethylene oxide nanofiber scaffolds via incorporating chitosan for tissue engineering

Currently, polyvinyl alcohol (PVA) and polyethylene oxide (PEO), as tissue engineering scaffolds materials, had been widely studied, however the hard issues in cell adhesive and antimicrobial properties still seriously limited their application in biomedical respects. Herein, we solved both hard issues by incorporating chitosan (CHI) into the PVA/PEO system, and successfully prepared PVA/PEO/CHI nanofiber scaffolds via electrospinning technology. First, the hierarchical pore structure and elevated porosity stacked by nanofiber of the nanofiber scaffolds supplied suitable space for cell growth. Significantly, the PVA/PEO/CHI nanofiber scaffolds (the cytotoxicity of grade 0) effectively improved cell adhesion by regulating the CHI content, and presented positively correlated with the CHI content. Besides, the excellent surface wettability of PVA/PEO/CHI nanofiber scaffolds exhibited maximum absorbability at a CHI content of 15 wt%. Based on the FTIR, XRD, and mechanical test results, we studied the semi-quantitative effect of hydrogen content on the aggregated state structure and mechanical properties of the PVA/PEO/CHI nanofiber scaffolds. The breaking stress of the nanofiber scaffolds increased with increasing CHI content, and the maximum value reached 15.37 MPa, increased by 67.61 %. Therefore, such dual biofunctional nanofiber scaffolds with improved mechanical properties showed great potential application in tissue engineering scaffolds.

Eco-Friendly OSN Membranes Based on Alginate Salts with Variable Nanofiltration Properties

In this work, membranes for organic solvents nanofiltration (OSN) based on a natural polymer, sodium alginate, were fabricated. They are chemically stable in organic solvents, including aprotic polar solvents. The unique advantage of these membranes is the absence of toxic reagents and solvents during their production. This ensures the safety and environmental friendliness of the production process. It has been shown that an operation as simple as changing the cation in alginate (Cu²⁺, Fe³⁺, Cr³⁺, Al³⁺, Zn²⁺, Ca²⁺) makes it possible to control the transport and separating properties of membranes, depending on the organic solvent being separated. Therefore, to isolate RemazolBrilliant Blue with MM = 626 g·mol^-1 from ethanol, membranes based on iron alginate with a rejection R = 97% and a permeability of 1.5 kg·m^-2·h^-1·bar^-1 are the most efficient. For isolation of the same solute from DMF and MP, membranes based on calcium alginate with an R of about 90% and a permeability of 0.1-0.2 kg·m^-2·h^-1·bar^-1 are the most efficient. The resulting membranes based on natural biodegradable sodium alginate are competitive compared to membranes based on synthetic polymers.

Recent Advances in Biomass-Based Materials for Oil Spill Cleanup

Oil spill on sea surfaces, which mainly produced by the oil leakage accident happened on tankers, offshore platforms, drilling rigs and wells, has bring irreversible damage to marine environments and ecosystems. Among various spill oil handling methods, using sorbents to absorb and recover spill oils is a perspective method because they are cost-effective and enable a high recovery and without secondary pollution to the ecosystem. Currently, sorbents based on biomass materials have aroused extensively attention thanks to their features of inexpensive, abundant, biodegradable, and sustainable. Herein, we comprehensively review the state-of-the-art development of biomass-based sorbents for spill oil cleanup in the recent five years. After briefly introducing the background, the basic theory and material characteristics for the separation of oil from water and the adsorption of oils is also presented. Various modification methods for biomass materials are summarized in section three. Section four discusses the recent progress of biomass as oil sorbents for oil spill cleanup, in which the emphasis is placed on the oil sorption capacity and the separation efficiency. Finally, the challenge and future development directions is outlined.

Biodegradable Electrospun Nanofiber Membranes as Promising Candidates for the Development of Face Masks

Aerosol particles, such as the widespread COVID-19 recently, have posed a great threat to humans. Combat experience has proven that masks can protect against viruses; however, the epidemic in recent years has caused serious environmental pollution from plastic medical supplies, especially masks. Degradable filters are promising candidates to alleviate this problem. Degradable nanofiber filters, which are developed by the electrospinning technique, can achieve superior filtration performance. This review focuses on the basic introduction to air filtration, the general aspects of face masks, and nanofibers. Furthermore, the progress of the state of art degradable electrospun nanofiber filters have been summarized, such as silk fibroin (SF), polylactic acid (PLA), chitosan, cellulose, and zein. Finally, the challenges and future development are highlighted.

Development of Functional Hybrid Polymers and Gel Materials for Sustainable Membrane-Based Water Treatment Technology: How to Combine Greener and Cleaner Approaches

Water quality and disposability are among the main challenges that governments and societies will outside during the next years due to their close relationship to population growth and urbanization and their direct influence on the environment and socio-economic development. Potable water suitable for human consumption is a key resource that, unfortunately, is strongly limited by anthropogenic pollution and climate change. In this regard, new groups of compounds, referred to as emerging contaminants, represent a risk to human health and living species; they have already been identified in water bodies as a result of increased industrialization. Pesticides, cosmetics, personal care products, pharmaceuticals, organic dyes, and other man-made chemicals indispensable for modern society are among the emerging pollutants of difficult remediation by traditional methods of wastewater treatment. However, the majority of the currently used waste management and remediation techniques require significant amounts of energy and chemicals, which can themselves be sources of secondary pollution. Therefore, this review reported newly advanced, efficient, and sustainable techniques and approaches for water purification. In particular, new advancements in sustainable membrane-based filtration technologies are discussed, together with their modification through a rational safe-by-design to modulate their hydrophilicity, porosity, surface characteristics, and adsorption performances. Thus, their preparation by the use of biopolymer-based gels is described, as well as their blending with functional cross-linkers or nanofillers or by advanced and innovative approaches, such as electrospinning.

Hollow Fiber Membrane for Organic Solvent Nanofiltration: A Mini Review

Organic solvents take up 80% of the total chemicals used in pharmaceutical and related industries, while their reuse rate is less than 50%. Traditional solvent treatment methods such as distillation and evaporation have many disadvantages such as high cost, environmental unfriendliness, and difficulty in recovering heat-sensitive, high-value molecules. Organic solvent nanofiltration (OSN) has been a prevalent research topic for the separation and purification of organic solvent systems since the beginning of this century with the benefits of no-phase change, high operational flexibility, low cost, as well as environmental friendliness. Especially, hollow fiber (HF) OSN membranes have gained a lot of attention due to their high packing density and easy scale-up as compared with flat-sheet OSN membranes. This paper critically reviewed the recent research progress in the preparation of HF OSN membranes with high performance, including different materials, preparation methods, and modification treatments. This paper also predicts the future direction of HF OSN membrane development.

Thin Film Composite Polyamide Reverse Osmosis Membrane Technology towards a Circular Economy

It is estimated that Reverse Osmosis (RO) desalination will produce, by 2025, more than 2,000,000 end-of-life membranes annually worldwide. This review examines the implementation of circular economy principles in RO technology through a comprehensive analysis of the RO membrane life cycle (manufacturing, usage, and end-of-life management). Future RO design should incorporate a biobased composition (biopolymers, recycled materials, and green solvents), improve the durability of the membranes (fouling and chlorine resistance), and facilitate the recyclability of the modules. Moreover, proper membrane maintenance at the usage phase, attained through the implementation of feed pre-treatment, early fouling detection, and membrane cleaning methods can help extend the service time of RO elements. Currently, end-of-life membranes are dumped in landfills, which is contrary to the waste hierarchy. This review analyses up to now developed alternative valorisation routes of end-of-life RO membranes, including reuse, direct and indirect recycling, and energy recovery, placing a special focus on emerging indirect recycling strategies. Lastly, Life Cycle Assessment is presented as a holistic methodology to evaluate the environmental and economic burdens of membrane recycling strategies. According to the European Commission's objectives set through the Green Deal, future perspectives indicate that end-of-life membrane valorisation strategies will keep gaining increasing interest in the upcoming years.