Interfacial polymerization of thin film nanocomposites: A new concept for reverse osmosis membranes

Incorporating functionalized graphene oxide into diethylene triamine-based nanofiltration membranes can improve the removal of emerging organic micropollutants

The presence of emerging organic micropollutants (OMPs) in drinking and potable waters is a matter of great concern due to the health hazards associated with these. In this work, we present the preparation and application of a thin-film nanocomposite (TFN) membrane containing functionalized graphene oxide to effectively remove low-molecular-weight OMPs from water. Graphene oxide was functionalized with amino silane to enhance its cross-linking capability during the formation of the polyamide active layer via interfacial polymerization of diethylene triamine and trimesoyl chloride. The TEM analysis showed that amino silane functionalized GO had 2-3 layered sheets, while non-functionalized graphene oxide appeared multilayered or stacked. XPS analysis confirmed the successful functionalization of GO. Characterization of the membranes with advanced techniques confirmed the successful incorporation of the GO and its functionalization: spectra from Fourier Transform Infra Red spectroscopy had the characteristic peaks of GO and NH groups; scanning Electron Microscopy (SEM) images showed a continuous presence of GO nanosheets. Contact angle measurements showed the TFN membranes to be more hydrophilic than their thin film composite (TFC) counterparts. Incorporating functionalized oxide nanosheets in the active polyamide layer produced additional water permeation channels, resulting in an improvement of ∼25 % in permeate flux compared to the pristine TFC and the TFN membrane with non-functionalized GO. The removal efficiencies of four OMPs commonly found in natural waters: Amitriptylene HCl (ATT HCl) and Bisphenol-A (BPA), Acetaminophen (ACT), and Caffeine (CFN) were determined for the synthesized membranes. The TFN membrane with functionalized GO outperformed its TFC counterpart with ∼100 % removal for BPA, ∼ 90 % for CFN and ATT HCl, and ∼80 % removal for the low molecular weight ACT. The high-efficiency rejection of OMPs was attributed to the synergistic effects of size exclusion as well as the reduced specific interactions between the functional groups.

A novel trimesoyl chloride/hyper branched polyethyleneimine/MOF (MIL-303)/P84 co-polyimide nanocomposite mixed matrix membranes with an ultra-thin surface cross linking layer for removing toxic heavy metal ions from wastewater

In this study, a positively charged nanofiltration (NF) nanocomposite mixed matrix membrane (MMM) was developed by incorporating metal-organic frameworks (MOFs) (MIL-303) into P84 co-polyimide and cross-linking with hyperbranched polyethyleneimine (HPEI). A very thin selective layer was subsequently formed on the cross-linked membrane surface using trimesoyl chloride (TMC). The incorporation of MIL-303 introduced specific water channels, enhancing the permeance of the nanocomposite MMMs. Additionally, it improved hydrophilicity and influenced the diffusion of the TMC monomer through the channels. The cross-linker HPEI resulted in NF membranes with increased electro-positivity and a reduced mean pore diameter. The very thin crosslinked TMC layer further improved permeance and heavy metal ions rejection of the membrane. This optimized membrane exhibited excellent rejection for both bivalent and monovalent ions, as well as heavy metal ions, effectively overcoming the common trade-off between permeance and rejection in NF membranes. The membrane demonstrated a remarkable permeance of 13.0 LMH/bar, coupled with exceptional rejection for heavy metal ions (96.8 % for Zn²⁺, 95.2 % for Ni²⁺, 95.7 % for Cu²⁺, 93.2 % for Pb²⁺, and 92.9 % for Cd²⁺). The TMC/HPEI/MIL-303/P84 system presented in this study holds significant promise for customizing high-performance positively charged NF membranes for the removal of heavy metal ions from wastewater.

A new methacrylate-chitosan based blend and its ZnO containing nanocomposites: Investigation of thermal and biological properties

Biobased materials are an important step towards a sustainable future. The need for these materials, which stand out in terms of their environmental and economic benefits, is increasing daily. This study includes the production of new bio based nanocomposites containing a blend of biopolymer chitosan (CS) and synthetic polymethacrylate derivative poly(2-oxo-2-(3,4,5-trifluoroanilino)ethyl-2-methylprop-2-enoate)(POTFAMA) and biosynthesized zinc oxide nanoparticles (ZnO NPs) by hydrothermal method. POTFAMA, POTFAMA-CS blend, and POTFAMA-CS/ZnO nanocomposites were characterized by FTIR, XRD, SEM, EDX, and TEM techniques. The thermal properties of the materials were determined by TGA and DSC. While POTFAMA reduced the thermal stability of CS, ZnO NPs incorporated into POTFAMA-CS blend increased the thermal stability. POTFAMA-CS blend had a single glass transition temperature (Tg) value at 116 °C. The Tg of CS, which was 93 °C, increased by 23 °C after blending with POTFAMA, and by 34 °C with the incorporation of 7 % ZnO NPs. The biological properties of the prepared materials have been meticulously investigated. The inhibition zone of CS against C. albicans was 10.66 ± 1.19 mm, while that of the POTFAMA-CS blend was 13.70 ± 1.54 mm. After standard BHT at a concentration of 120 μg/mL, the highest DPPH inhibition percentages belonged to POTFAMA (60.56 %) and POTFAMA-CS (52.99 %). It was detected that the wound closure rates of POTFAMA (17.51 ± 0.75 %) and POTFAMA-CS (15.51 ± 2.52 %) were better than the characteristics of CS wound closure (13.61 ± 2.01 %). The results suggest that POTFAMA-CS may be a good alternative as a wound-healing agent. Furthermore, nanocomposites containing 5 % and 7 % ZnO NPs can be an alternative material in healthcare due to their higher antimicrobial activity.

Synthesis of polyaniline-coated composite anion exchange membranes based on polyacrylonitrile for the separation of tartaric acid via electrodialysis

The increasing need to tackle major societal challenges such as environmental sustainability and resource scarcity has heightened global interest in green and efficient separation technologies. The separation of organic acids, particularly tartaric acid, holds significant industrial importance in the food and pharmaceutical sectors. Purifying tartaric acid is crucial due to its roles as a chiral catalyst, antioxidant, and stabilizer, which are vital for ensuring product quality and efficiency. In this study, we synthesized heterogeneous anion exchange membranes by casting a solution of polyacrylonitrile (PAN) homogeneously dispersed with micronized anion exchange resin [polystyrene-divinylbenzene-trimethyl ammonium chloride (PS-DVB-TAC)]. These membranes were further coated with polyaniline (PANI) through in situ polymerization at different time intervals such as 2, 12, and 24 h. Cation exchange membranes were also prepared by solution casting of PAN dispersed with micronized cation exchange resin, sulfonated poly-styrene-co-divinylbenzene, and SPS-DVB. These synthesized anion exchange membranes with and without a PANI coating were examined for their separation performance of tartaric acid, along with the cation exchange membranes in a four-compartment electrodialyser at a constant voltage. The newly fabricated membranes were characterized by different techniques, including attenuated total reflectance-Fourier transform infrared spectroscopy for functional group analysis, scanning electron microscopy for their surface morphology, and the four-probe method for electrical conductivity. In addition, ion exchange capacity and water uptake have been measured. The electrodialysis experiments showed that 14.82 wt% of tartrate ions moved into the product compartment through the uncoated anion exchange membrane within 30 min at a voltage of 30 V. Under the same conditions, membranes coated with PANI at 2, 12, and 24 h raised the separation efficiency to 21.19%, 34.13%, and 37.21%, respectively. Findings indicate that membranes coated with PANI for extended periods demonstrate superior separation efficiency for tartaric acid. Consequently, this energy-efficient method shows significant potential for application in the food and pharmaceutical industries for separating tartaric acid and other organic and amino acids. This research can advance practical and sustainable separation technologies, addressing critical societal issues like resource efficiency and environmental sustainability.

A review on the potential of cellulose nanomaterials for the development of thin film composite polyamide membranes for water treatment

Membrane-based separation technologies have drawn significant interest because of their compactness, low energy consumption, and ability to be easily integrated with existing processes. There has been significant interest in the utilization of natural materials derived from sustainable and renewable resources for membrane fabrication. Cellulose is one of the promising polymers which has been extensively studied in membrane fabrication and modification due to its abundant availability, non-toxicity and biodegradability. While there have been several reviews in recent years separately on TFC membranes and cellulose-based materials for different applications, reviews exclusively focusing on cellulosic nanomaterials-based TFC membranes are still lacking. This review provides an overview of the types of cellulose nanomaterials exploited for the development and modification of TFC membranes, particularly those used for desalination and wastewater treatment. We have presented a brief description of cellulose-based nanomaterials followed by a detailed discussion of different studies addressing each cellulose nanomaterial separately. In addition, we have summarized the performance of different studies in the literature, paying particular attention to the enhancement achieved by the incorporation of cellulose nanomaterial in the membrane.

How Can the Filler-Polymer Interaction in Mixed Matrix Membranes Be Enhanced?

Mixed matrix membranes (MMMs) constitute a type of molecular separation membranes in which a nanomaterial type filler is dispersed in a given polymer to enhance its selective permeation ability. The key issue in MMMs is the establishing of a proper filler-polymer interaction to avoid non-selective transport paths while increasing permeability but also to improve other membrane properties such as aging and plasticization. Along the pass years several strategies have been applied to enhance the physicochemical interaction between the fillers (e. g. silicas, zeolites, porous coordination polymers, carbonaceous materials, etc.) and the membrane polymers: increase of external surface area, priming, use of intrinsically more compatible fillers, in situ synthesis of filler, in situ polymerization, polymer side-chain modification and post-synthetic modification of filler.

Tailoring Polyamide Nanofiltration Membranes by Switching Charge of Nanocellulose Interlayers

The interlayer strategy has emerged as an effective approach for modulating the interfacial polymerization process and improving the permeability and selectivity of polyamide membranes. However, the underlying mechanisms by which charged interlayers influence the interfacial polymerization process remain inadequately understood. In this study, we utilized two distinct charged cellulose nanofibers, namely, carboxylated cellulose (⊖-CNF) and quaternized cellulose ([Formula: see text]-CNF), as interlayers to regulate the interfacial polymerization process. Through simulation results, isothermal titration calorimetry (ITC) and UV tests, we demonstrated that the [Formula: see text]-CNF interlayer, which possesses stronger hydration capability and better piperazine affinity, enhanced the diffusion of piperazine across the reaction interface compared with the ⊖-CNF interlayer. This led to an acceleration of the interfacial polymerization process and the formation of a denser membrane structure. Further investigation revealed that the charged interlayers significantly influenced the surface charging properties of the resulting nanofiltration membranes within a 30 nm range of electrostatic effects. Specifically, the ⊖-CNF interlayer conferred a higher negative charge to the membrane surface, while the [Formula: see text]-CNF interlayer endowed the membranes with a lower surface negative charge. Leveraging these differences, the ⊖-i-TFC membranes exhibited exceptional separation performance for divalent anions, achieving a SO42-/Cl- selectivity of 136. Conversely, the [Formula: see text]-i-TFC membrane demonstrated an enhanced separation of divalent cations, displaying a Mg2+/Na+ selectivity of 3.5. This study lays the groundwork for regulating the surface charging properties of polyamide membranes, offering potential advancements in nanofiltration applications.

MOF-Based Membranes for Remediated Application of Water Pollution

Membrane separation plays a crucial role in the current increasingly complex energy environment. Membranes prepared by metal-organic framework (MOF) materials usually possess unique advantages in common, such as uniform pore size, ultra-high porosity, enhanced selectivity and throughput, and excellent adsorption property, which have been contributed to the separation fields. In this comprehensive review, we summarize various designs and synthesized strategies of free-standing MOF and composite MOF-based membranes for water treatment. Special emphases are given not only on the effects of MOF on membrane performance, removal efficiencies, and elimination mechanisms, but also on the importance of MOF-based membranes for the applications of oily and micro-pollutant removal, adsorption, separation, and catalysis. The challenges and opportunities in the future for the industrial implementation of MOF-based membranes are also discussed.

Nanomaterials-modified reverse osmosis membranes: a comprehensive review

Because of its great efficiency and widespread application, reverse osmosis (RO) is a popular tool for water desalination and purification. However, traditional RO membranes have a short lifespan due to membrane fouling, deterioration, decreased salt rejection rate, and the low water flux with aging. As a result, membrane modification has received a lot of attention recently, with nanomaterials being extensively researched to improve membrane efficacy and lifespan. Herein, we present an in-depth analysis of recent advances of RO membranes modification utilizing nanomaterials. An overview of the various nanomaterials used for membrane modification, including metal oxides, zeolites, and carbon nanomaterials, is provided. The synthesis techniques and methods of integrating these nanomaterials into RO membranes are also discussed. The impacts of nanomaterial change on the performance of RO membranes are addressed. The underlying mechanisms responsible for RO membrane enhancements by nanomaterials, such as improved surface hydrophilicity, reduced membrane fouling via surface repulsion and anti-adhesion properties, and enhanced structural stability, are discussed. Furthermore, the review provides a critical analysis of the challenges and limitations associated with the use of nanomaterials to modify RO membranes. Overall, this review provides valuable insights into the modification of RO membranes with nanomaterials, providing a full grasp of the benefits, challenges, and future prospects of this challenging topic.

Nanoscience and nanotechnology for water remediation: an earnest hope toward sustainability

Water pollution and the global freshwater crisis are the most alarming concerns of the 21st century, as they threaten the sustainability and ecological balance of the environment. The growth of global population, climate change, and expansion of industrial processes are the main causes of these issues. Therefore, effective remediation of polluted water by means of detoxification and purification is of paramount importance. To this end, nanoscience and nanotechnology have emerged as viable options that hold tremendous potential toward the advancement of wastewater treatment methods to enhance treatment efficiency along with augmenting water supply via utilization of unconventional water sources. Materials at the nano level have shown great promise toward water treatment applications owing to their unique physicochemical properties. In this focus article, we highlight the role of new fundamental properties at the nano scale and material properties that are drastically increased due to the nano dimension (e.g. volume-surface ratio) and highlight their impact and potential toward water treatment. We identify and discuss how nano-properties could improve the three main domains of water remediation: the identification of pollutants, their adsorption and catalytic degradation. After discussing all the beneficial aspects we further discuss the key challenges associated with nanomaterials for water treatment. Looking at the current state-of-the-art, the potential as well as the challenges of nanomaterials, we believe that in the future we will see a significant impact of these materials on many water remediation strategies.

Recent Developments in Nanocomposite Membranes Based on Carbon Dots

Carbon dots (CDs) have aroused colossal attention in the fabrication of nanocomposite membranes ascribed to their ultra-small size, good dispersibility, biocompatibility, excellent fluorescence, facile synthesis, and ease of functionalization. Their unique properties could significantly improve membrane performance, including permeance, selectivity, and antifouling ability. In this review, we summarized the recent development of CDs-based nanocomposite membranes in many application areas. Specifically, we paid attention to the structural regulation and functionalization of CDs-based nanocomposite membranes by CDs. Thus, a detailed discussion about the relationship between the CDs' properties and microstructures and the separation performance of the prepared membranes was presented, highlighting the advantages of CDs in designing high-performance separation membranes. In addition, the excellent optical and electric properties of CDs enable the nanocomposite membranes with multiple functions, which was also presented in this review.

Micelles regulated thin film nanocomposite membrane with enhanced nanofiltration performance

The desalination performance of thin film nanocomposite (TFN) membranes is significantly influenced by the nature of nanofillers and the structure of the polyamide (PA) layer. Herein, a micelles regulated interfacial polymerization (MRIP) strategy is reported for the preparation of TFN membranes with enhanced nanofiltration (NF) performance. Specially, stable and ultrafine micelles, synthesized from the poly(ethylene oxide)-b-poly(4-vinyl pyridine)-b-polystyrene (PEO-PVP-PS) triblock copolymers, were utilized as regulators in the aqueous phase during the interfacial polymerization (IP) process. TFN membranes were fabricated with varying concentrations of micelles to improve their properties and performances. The structure of the PA layer was further regulated by modulating the content of trimesoyl chloride (TMC), which significantly enhances the performance of the TFN membrane with micelles. Attributable to the homogeneously dispersed micelles and the modified PA layer, the optimized membrane denoted as TFN-2-0.3 exhibits an improved separation performance of 20.7 L m-2h-1 bar-1 and 99.3 % Na2SO4 rejection, demonstrating nearly twice the permeance and 2.7 % higher rejection than that of the original control membrane, respectively. The mechanism of this MRIP strategy was investigated through the diffusion experiments of piperazine (PIP) and interfacial tension tests. The incorporated micelles effectively lower the interfacial tension, promote the diffusion of PIP and accelerate the IP reaction, resulting in a denser and thinner PA layer. Collectively, these findings demonstrate that TFN membranes with micelles exhibit increased roughness, enhanced hydrophilicity, superior rejection to divalent salts, and better acid-base resistance, highlighting their potential applications in the design of TFN membranes.

Nonmonotonic polymer translocation kinetics through nanopores under changing surface-polymer interactions

Understanding the dynamics of polymers in confined environments is pivotal for diverse applications ranging from polymer upcycling to bioseparations. In this study, we develop an entropic barrier model using self-consistent field theory that considers the effect of attractive surface interactions, solvation, and confinement on polymer kinetics. In this model, we consider the translocation of a polymer from one cavity into a second cavity through a single-segment-width nanopore. We find that, for a polymer in a good solvent (i.e., excluded volume, u0 > 0), there is a nonmonotonic dependence of mean translocation time (τ) on surface interaction strength, ɛ. At low ɛ, excluded volume interactions lead to an energetic penalty and longer translocation times. As ɛ increases, the surface interactions counteract the energetic penalty imposed by excluded volume and the polymer translocates faster through the nanopore. However, as ɛ continues to increase, an adsorption transition occurs, which leads to significantly slower kinetics due to the penalty of desorption from the first cavity. The ɛ at which this adsorption transition occurs is a function of the excluded volume, with higher u0 leading to an adsorption transition at higher ɛ. Finally, we consider the effect of translocation across different size cavities. We find that the kinetics for translocation into a smaller cavity speeds up while translocation to a larger cavity slows down with increasing ɛ due to higher surface contact under stronger confinement.

Ti2NTx quasi-MXene modified polyamide thin film composite reverse osmosis membrane with effective desalination and antifouling performance

In this study, considering the serious problem of lack of fresh water worldwide and the effectiveness of reverse osmosis (RO) membranes in water purification, we prepared improved RO membranes with two-dimensional quasi-MXene nanosheets. In this study, the MAX phase with the chemical formula of Ti2AlN was prepared through the reactive sintering route. Prosperous preparation of the MAX phase with the hexagonal crystalline structure was approved by an X-ray diffraction pattern. Compacted sheets morphology was recognized for the prepared MAX phase from transmittance electron microscopy and scanning electron microscopy micrographs. Then, Ti2NTx quasi-MXene nanosheets were prepared by selective ultrasonic-assisted exfoliation of the MAX phase. Polyamide (PA) thin-layer composite RO membranes with different weight percentages of Ti2NTx quasi-MXene were fabricated by the interfacial polymerization (IP) method. The addition of ultrasonic-assisted prepared quasi-MXene creates numerous and coherent nanochannels on the surface of the membrane. The optimum membrane with 0.01 wt% of quasi-MXene showed the highest pure water flux of 31.9 L m-2. h-1 with an improved salt rejection of 98.2%. Therefore, these nanosheets showed that they can partially solve the trade-off between water permeability and salt rejection, which is a serious challenge in RO membranes. Also, the membranes containing quasi-MXene showed good resistance against fouling by humic acid. This research can be a scalable development in making high-performance membranes.

An economical and simple method for preparing highly permeable and chlorine-resistant reverse osmosis membranes with potential commercial applications

The improvement in the overall efficiency of thin-film composite (TFC) reverse osmosis (RO) membranes is limited by their low permeability and sensitivity to degradation by chlorine. In the present study, polypiperazine (PIP), the commonly used amine monomer in preparing commercial TFC nanofiltration (NF) membranes, was used to regulate the m-phenylenediamine (MPD) based interfacial polymerization (IP) process. The results showed that addition of PIP optimized the micro-structure and surface properties of the polyamide (PA) layer. When the MPD and PIP mass ratio was 1 : 1, the TFCW-1:1 membrane exhibited 70% flux enhancement compared to pure MPD-based TFCW-1:0 membranes. Besides, the TFCW-1:1 membrane exhibited better chlorine-resistant performance since the NaCl rejection declined to just 3.8% while it was 11.3% for TFCW-1:0 membranes after immersion in 500 ppm NaClO solution for 48 h. Such improvement can be attributed to the increased number of unreacted amine groups and the thickness of the PA layer that PIP brought, which provided a sacrificial protective layer to consume the active chlorine, and thus maintain the integrity of the inner rejection layer. In all, the novelty and purpose of the present work is to find a more simple and scalable method to fabricate high-performance TFC RO membranes by using commonly, cheaply and frequently used materials.

Combined Electrospinning-Electrospraying for High-Performance Bipolar Membranes with Incorporated MCM-41 as Water Dissociation Catalysts

Electrospinning has been demonstrated as a very promising method to create bipolar membranes (BPMs), especially as it allows three-dimensional (3D) junctions of entangled anion exchange and cation exchange nanofibers. These newly developed BPMs are relevant to demanding applications, including acid and base production, fuel cells, flow batteries, ammonia removal, concentration of carbon dioxide, and hydrogen generation. However, these applications require the introduction of catalysts into the BPM to allow accelerated water dissociation, and this remains a challenge. Here, we demonstrate a versatile strategy to produce very efficient BPMs through a combined electrospinning-electrospraying approach. Moreover, this work applies the newly investigated water dissociation catalyst of nanostructured silica MCM-41. Several BPMs were produced by electrospraying MCM-41 nanoparticles into the layers directly adjacent to the main BPM 3D junction. BPMs with various loadings of MCM-41 nanoparticles and BPMs with different catalyst positions relative to the junction were investigated. The membranes were carefully characterized for their structure and performance. Interestingly, the water dissociation performance of BPMs showed a clear optimal MCM-41 loading where the performance outpaced that of a commercial BPM, recording a transmembrane voltage of approximately 1.11 V at 1000 A/m2. Such an excellent performance is very relevant to fuel cell and flow battery applications, but our results also shed light on the exact function of the catalyst in this mode of operation. Overall, we demonstrate clearly that introducing a novel BPM architecture through a novel hybrid electrospinning-electrospraying method allows the uptake of promising new catalysts (i.e., MCM-41) and the production of very relevant BPMs.

Extreme Ion-Transport Inorganic 2D Membranes for Nanofluidic Applications

Inorganic 2D materials offer a new approach to controlling mass diffusion at the nanoscale. Controlling ion transport in nanofluidics is key to energy conversion, energy storage, water purification, and numerous other applications wherein persistent challenges for efficient separation must be addressed. The recent development of 2D membranes in the emerging field of energy harvesting, water desalination, and proton/Li-ion production in the context of green energy and environmental technology is herein discussed. The fundamental mechanisms, 2D membrane fabrication, and challenges toward practical applications are highlighted. Finally, the fundamental issues of thermodynamics and kinetics are outlined along with potential membrane designs that must be resolved to bridge the gap between lab-scale experiments and production levels.

Recent Advances in the Support Layer, Interlayer and Active Layer of TFC and TFN Organic Solvent Nanofiltration (OSN) Membranes: A Review

Although separation of solutes from organic solutions is considered a challenging process, it is inevitable in various chemical, petrochemical and pharmaceutical industries. OSN membranes are the heart of OSN technology that are widely utilized to separate various solutes and contaminants from organic solvents, which is now considered an emerging field. Hence, numerous studies have been attracted to this field to manufacture novel membranes with outstanding properties. Thin-film composite (TFC) and nanocomposite (TFN) membranes are two different classes of membranes that have been recently utilized for this purpose. TFC and TFN membranes are made up of similar layers, and the difference is the use of various nanoparticles in TFN membranes, which are classified into two types of porous and nonporous ones, for enhancing the permeate flux. This study aims to review recent advances in TFC and TFN membranes fabricated for organic solvent nanofiltration (OSN) applications. Here, we will first study the materials used to fabricate the support layer, not only the membranes which are not stable in organic solvents and require to be cross-linked, but also those which are inherently stable in harsh media and do not need any cross-linking step, and all of their advantages and disadvantages. Then, we will study the effects of fabricating different interlayers on the performance of the membranes, and the mechanisms of introducing an interlayer in the regulation of the PA structure. At the final step, we will study the type of monomers utilized for the fabrication of the active layer, the effect of surfactants in reducing the tension between the monomers and the membrane surface, and the type of nanoparticles used in the active layer of TFN membranes and their effects in enhancing the membrane separation performance.

Harvesting Blue Energy Based on Salinity and Temperature Gradient: Challenges, Solutions, and Opportunities

Greenhouse gas emissions associated with power generation from fossil fuel combustion account for 25% of global emissions and, thus, contribute greatly to climate change. Renewable energy sources, like wind and solar, have reached a mature stage, with costs aligning with those of fossil fuel-derived power but suffer from the challenge of intermittency due to the variability of wind and sunlight. This study aims to explore the viability of salinity gradient power, or "blue energy", as a clean, renewable source of uninterrupted, base-load power generation. Harnessing the salinity gradient energy from river estuaries worldwide could meet a substantial portion of the global electricity demand (approximately 7%). Pressure retarded osmosis (PRO) and reverse electrodialysis (RED) are more prominent technologies for blue energy harvesting, whereas thermo-osmotic energy conversion (TOEC) is emerging with new promise. This review scrutinizes the obstacles encountered in developing osmotic power generation using membrane-based methods and presents potential solutions to overcome challenges in practical applications. While certain strategies have shown promise in addressing some of these obstacles, further research is still required to enhance the energy efficiency and feasibility of membrane-based processes, enabling their large-scale implementation in osmotic energy harvesting.

Polycage membranes for precise molecular separation and catalysis

The evolution of the chemical and pharmaceutical industry requires effective and less energy-intensive separation technologies. Engineering smart materials at a large scale with tunable properties for molecular separation is a challenging step to materialize this goal. Herein, we report thin film composite membranes prepared by the interfacial polymerization of porous organic cages (POCs) (RCC3 and tren cages). Ultrathin crosslinked polycage selective layers (thickness as low as 9.5 nm) are obtained with high permeance and strict molecular sieving for nanofiltration. A dual function is achieved by combining molecular separation and catalysis. This is demonstrated by impregnating the cages with highly catalytically active Pd nanoclusters ( ~ 0.7 nm). While the membrane promotes a precise molecular separation, its catalytic activity enables surface self-cleaning, by reacting with any potentially adsorbed dye and recovering the original performance. This strategy opens opportunities for the development of other smart membranes combining different functions and well-tailored abilities.

When self-assembly meets interfacial polymerization

Interfacial polymerization (IP) and self-assembly are two thermodynamically different processes involving an interface in their systems. When the two systems are incorporated, the interface will exhibit extraordinary characteristics and generate structural and morphological transformation. In this work, an ultrapermeable polyamide (PA) reverse osmosis (RO) membrane with crumpled surface morphology and enlarged free volume was fabricated via IP reaction with the introduction of self-assembled surfactant micellar system. The mechanisms of the formation of crumpled nanostructures were elucidated via multiscale simulations. The electrostatic interactions among m-phenylenediamine (MPD) molecules, surfactant monolayer and micelles, lead to disruption of the monolayer at the interface, which in turn shapes the initial pattern formation of the PA layer. The interfacial instability brought about by these molecular interactions promotes the formation of crumpled PA layer with larger effective surface area, facilitating the enhanced water transport. This work provides valuable insights into the mechanisms of the IP process and is fundamental for exploring high-performance desalination membranes.

Thin-Film Nanocomposite (TFN) Membranes for Water Treatment Applications: Characterization and Performance

Thin-film nanocomposite (TFN) membranes have been widely investigated for water treatment applications due to their promising performance in terms of flux, salt rejection, and their antifouling properties. This review article provides an overview of the TFN membrane characterization and performance. It presents different characterization techniques that have been used to analyze these membranes and the nanofillers within them. The techniques comprise structural and elemental analysis, surface and morphology analysis, compositional analysis, and mechanical properties. Additionally, the fundamentals of membrane preparation are also presented, together with a classification of nanofillers that have been used so far. The potential of TFN membranes to address water scarcity and pollution challenges is significant. This review also lists examples of effective TFN membrane applications for water treatment. These include enhanced flux, enhanced salt rejection, antifouling, chlorine resistance, antimicrobial properties, thermal stability, and dye removal. The article concludes with a synopsis of the current status of TFN membranes and future perspectives.

Correlating the Role of Nanofillers with Active Layer Properties and Performance of Thin-Film Nanocomposite Membranes

Thin-film nanocomposite (TFN) membranes are emerging water-purification membranes that could provide enhanced water permeance with similar solute removal over traditional thin-film composite (TFC) membranes. However, the effects of nanofiller incorporation on active layer physico-chemical properties have not been comprehensively studied. Accordingly, we aimed to understand the correlation between nanofillers, active layer physico-chemical properties, and membrane performance by investigating whether observed performance differences between TFN and control TFC membranes correlated with observed differences in physico-chemical properties. The effects of nanofiller loading, surface area, and size on membrane performance, along with active layer physico-chemical properties, were characterized in TFN membranes incorporated with Linde Type A (LTA) zeolite and zeolitic imidazole framework-8 (ZIF-8). Results show that nanofiller incorporation up to ~0.15 wt% resulted in higher water permeance and unchanged salt rejection, above which salt rejection decreased 0.9-25.6% and 26.1-48.3% for LTA-TFN and ZIF-8-TFN membranes, respectively. Observed changes in active layer physico-chemical properties were generally unsubstantial and did not explain observed changes in TFN membrane performance. Therefore, increased water permeance in TFN membranes could be due to preferential water transport through porous structures of nanofillers or along polymer-nanofiller interfaces. These findings offer new insights into the development of high-performance TFN membranes for water/ion separations.

Nanostructured Material and its Application in Membrane Separation Technology

Abstract:

Nanomaterials are classified with their at least one dimension in the range of 1-100 nm, which offers new innovative solutions for membrane development. These are included as nanosized adsorbents, nanomembranes, nanocomposites, photocatalysts, nanotubes, nanoclays, etc. Nanomaterials are promising, exceptional properties for one of the opportunity is to prevent the global water crisis with their extraordinary performance as their usage for membrane development, particularly for water treatment process. Nanomaterial based membranes that include nanoparticles, nanofibers, 2D layered materials, and their nanostructured composites which provide superior permeation characteristics besides their antifouling, antibacterial and photodegradation properties. They are enable for providing the extraordinary properties to be used as ultrafast and ultimately selective membranes for water purification. In this review, recently developed nanomaterial based membranes and their applications for water treatment process were summarized. The main attention is given to the nanomaterial based membrane structure design. The variety in terms of constituent structure and alterations provide nanomaterial based membranes which will be expected to be a perfect separation membrane in the future.

A comprehensive review on zeolite-based mixed matrix membranes for CO2/CH4 separation

Biogas consisting of carbon dioxide/methane (CO₂/CH₄) gas mixtures has emerged as an alternative renewable fuel to natural gas. The presence of CO₂ can decrease the calorific value and generate greenhouse gas. Hence, separating CO₂ from CH₄ is a vital step in enhancing the use of biogas. Zeolite and zeolite-based mixed matrix membrane (MMM) is considered an auspicious candidate for CO₂/CH₄ separation due to thermal and chemical stability. This review initially addresses the development of zeolite and zeolite-based MMM for the CO₂/CH₄ separation. The highest performance in terms of CO₂ permeance and CO₂/CH₄ selectivity was achieved using zeolite and zeolite-based MMM, which exhibited CO₂ permeance in the range of 2.0 × 10^{- 7}-7.0 × 10^{- 6} mol m^{- 2} s^{- 1} Pa^{- 1} with CO₂/CH₄ selectivity ranging from 3 to 300. Current trends directed toward improving CO₂/CH₄ selectivity via modification methods including post-treatment, ion-exchanged, amino silane-grafted, and ionic liquid encapsulated of zeolite-based MMM. Those modification methods improved the defect-free and interfacial adhesions between zeolite particulates and polymer matrices and subsequently enhanced the CO₂/CH₄ selectivity. The modifications via ionic liquid and silane methods more influenced the CO₂/CH₄ selectivity with 90 and 660, respectively. This review also focuses on the possible applications of zeolite-based MMM, which include the purification and treatment of water as well as biomedical applications. Lastly, future advances and opportunities for gas separation applications are also briefly discussed. This review aims to share knowledge regarding zeolite-based MMM and inspire new industrial applications.

Advanced Polymeric Nanocomposite Membranes for Water and Wastewater Treatment: A Comprehensive Review

Nanomaterials have been extensively used in polymer nanocomposite membranes due to the inclusion of unique features that enhance water and wastewater treatment performance. Compared to the pristine membranes, the incorporation of nanomodifiers not only improves membrane performance (water permeability, salt rejection, contaminant removal, selectivity), but also the intrinsic properties (hydrophilicity, porosity, antifouling properties, antimicrobial properties, mechanical, thermal, and chemical stability) of these membranes. This review focuses on applications of different types of nanomaterials: zero-dimensional (metal/metal oxide nanoparticles), one-dimensional (carbon nanotubes), two-dimensional (graphene and associated structures), and three-dimensional (zeolites and associated frameworks) nanomaterials combined with polymers towards novel polymeric nanocomposites for water and wastewater treatment applications. This review will show that combinations of nanomaterials and polymers impart enhanced features into the pristine membrane; however, the underlying issues associated with the modification processes and environmental impact of these membranes are less obvious. This review also highlights the utility of computational methods toward understanding the structural and functional properties of the membranes. Here, we highlight the fabrication methods, advantages, challenges, environmental impact, and future scope of these advanced polymeric nanocomposite membrane based systems for water and wastewater treatment applications.

Molecular modeling of thin-film nanocomposite membranes for reverse osmosis water desalination

The scarcity of freshwater resources is a major global challenge causedby population and economic growth. Water desalination using a reverse osmosis (RO) membrane is a promising technology to supply potable water from seawater and brackish water. The advancement of RO desalination highly depends on new membrane materials. Currently, the RO technology mainly relies on polyamide thin-film composite (TFC) membranes, which suffer from several drawbacks (e.g., low water permeability, permeability-selectivity tradeoff, and low fouling resistance) that hamper their real-world applications. Nanoscale fillers with specific characteristics can be used to improve the properties of TFC membranes. Embedding nanofillers into TFC membranes using interfacial polymerization allows the creation of thin-film nanocomposite (TFNC) membranes, and has become an emerging strategy in the fabrication of high-performance membranes for advanced RO water desalination. To achieve optimal design, it is indispensable to search for reliable methods that can provide fast and accurate predictions of the structural and transport properties of the TFNC membranes. However, molecular understanding of permeability-selectivity characteristics of nanofillers remains limited, partially due to the challenges in experimentally exploring microscopic behaviors of water and salt ions in confinement. Molecular modeling and simulations can fill this gap by generating molecular-level insights into the effects of nanofillers' characteristics (e.g., shape, size, surface chemistry, and density) on water permeability and ion selectivity. In this review, we summarize molecular simulations of a diverse range of nanofillers including nanotubes (carbon nanotubes, boron nitride nanotubes, and aquaporin-mimicking nanochannels) and nanosheets (graphene, graphene oxide, boron nitride sheets, molybdenum disulfide, metal and covalent organic frameworks) for water desalination applications. These simulations reveal that water permeability and salt rejection, as the major factors determining the desalination performance of TFNC membranes, significantly depend on the size, topology, density, and chemical modifications of the nanofillers. Identifying their influences and the physicochemical processes behind, via molecular modeling, is expected to yield important insights for the fabrication and optimization of the next generation high-performance TFNC membranes for RO water desalination.

Enhanced Separation Performance of Polyamide Thin-Film Nanocomposite Membranes with Interlayer by Constructed Two-Dimensional Nanomaterials: A Critical Review

Thin-film composite (TFC) polyamide (PA) membrane has been widely applied in nanofiltration, reverse osmosis, and forward osmosis, including a PA rejection layer by interfacial polymerization on a porous support layer. However, the separation performance of TFC membrane is constrained by the trade-off relationship between permeability and selectivity. Although thin-film nanocomposite (TFN) membrane can enhance the permeability, due to the existence of functionalized nanoparticles in the PA rejection layer, the introduction of nanoparticles leads to the problems of the poor interface compatibility and the nanoparticles agglomeration. These issues often lead to the defect of PA rejection layers and reduction in selectivity. In this review, we summarize a new class of structures of TFN membranes with functionalized interlayers (TFNi), which promises to overcome the problems associated with TFN membranes. Recently, functionalized two-dimensional (2D) nanomaterials have received more attention in the assembly materials of membranes. The reported TFNi membranes with 2D interlayers exhibit the remarkable enhancement on the permeability, due to the shorter transport path by the "gutter mechanism" of 2D interlayers. Meanwhile, the functionalized 2D interlayers can affect the diffusion of two-phase monomers during the interfacial polymerization, resulting in the defect-free and highly crosslinked PA rejection layer. Thus, the 2D interlayers enabled TFNi membranes to potentially overcome the longstanding trade-off between membrane permeability and selectivity. This paper provides a critical review on the emerging 2D nanomaterials as the functionalized interlayers of TFNi membranes. The characteristics, function, modification, and advantages of these 2D interlayers are summarized. Several perspectives are provided in terms of the critical challenges for 2D interlayers, managing the trade-off between permeability, selectivity, and cost. The future research directions of TFNi membranes with 2D interlayers are proposed.

Nanocomposite membranes for organic solvent nanofiltration: Recent advances, challenges, and prospects

Organic solvent nanofiltration (OSN) is an emerging technology for the separation of organic solvents that are relevant to the petrochemical, pharmaceutical, food and fine chemical industries. The separation performance of OSN membranes has continued to push the boundary up through advanced membrane fabrication techniques and novel materials for fabricating the membranes. Despite the many advantages, OSN membranes still face such challenges as low solvent permeability and durability in harsh organic solvent conditions. To overcome these limitations, attempts have been made to incorporate nanomaterial fillers into OSN membranes to improve their overall performance. This review analyzes the potential and use of nanomaterials for OSN membranes, including covalent organic frameworks (COFs), metal-organic frameworks (MOFs), metal oxides (MOs) and carbon-based materials (CBMs). Recent advances in the state-of-the-art nano-based OSN membranes, in the form of thin-film nanocomposite (TFN) membranes and mixed matrix membranes (MMMs), are reviewed. Moreover, the separation mechanisms of OSN with nano-based membranes are discussed. The challenges faced by these OSN membranes are also elaborated, and recommendations for further research in this field are provided.

High-flux nanofiltration membrane with modified highly dispersed MOF particles as nano filler

The synthesis of optimized thin film nanocomposite (TFN) membrane with no or few defects is an efficacious method which can improve nanofiltration performance. However, poor dispersion of fillers in the organic phase and wrong compatibility between fillers and polymerizate are still a serious problem. In this study, the particle size of metal organic framework (MOF), aluminum-based metal-organic frameworks (CAU-1) was modulated and for the first time, dodecyl aldehyde was used to modify the surface hydrophobicity of CAU-1, which improved the dispersibility and inhibited the aggregation in the trimesoyl chloride (TMC)/n-hexane solution; later CAU-1 and modified CAU-1 were incorporated into the polyamide (PA) selective layer to synthesize TFN membrane by interfacial polymerization (IP). The particle size modulation and modification of the CAU-1 were demonstrated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) characterization. The characterization showed that PA selective layer was synthesized on the top layer of polysulfone (PSF) substrate. The pure water flux of the TFN membrane was increased to 79.89 ± 1.24 L·m^-2·h^-1·bar^-1 compared to the original thin film composite (TFC) membrane, which was due to the polymerization of 100 nm modified CAU-1 on the PA layer to form a new water molecular channel, thus increasing the water flux by about 70%.

Experimental and TDDFT materials simulation of thermal characteristics and entropy optimized of Williamson Cu-methanol and Al2O3-methanol nanofluid flowing through solar collector

Current investigation emphasizes the evaluation of entropy in a porous medium of Williamson nanofluid (WNF) flow past an exponentially extending horizontal plate featuring Parabolic Trough Solar Collector (PTSC). Two kinds of nanofluids such as copper-methanol (Cu-MeOH) and alumina-methanol (Al₂O₃-MeOH) were tested, discussed and plotted graphically. The fabricated nanoparticles are studied using different techniques, including TDDFT/DMOl³ method as simulated and SEM measurements as an experimental method. The centroid lengths of the dimer are 3.02 Å, 3.27 Å, and 2.49 Å for (Cu-MeOH), (Al₂O₃-MeOH), and (Cu-MeOH-αAl-MOH), respectively. Adequate similarity transformations were applied to convert the partial differential equation (PDEs) into nonlinear ordinary differential equations (ODEs) with the corresponding boundary constraints. An enhancement in Brinkmann and Reynolds numbers increases the overall system entropy. WNF parameter enhances the heat rate in PTSC. The thermal efficiency gets elevated for Cu-MeOH than that of Al₂O₃-MeOH among 0.8% at least and 6.6% in maximum for varying parametric values.