Thin-film Membranes Research Articles

Manipulating Interface Magnetism in Manganite Thin Film Membranes by Substrate Surface Chemistry

Manipulating Interface Magnetism in Manganite Thin Film Membranes by Substrate Surface Chemistry

Investigating novel thin-film nanocomposite membranes for sustainable water recovery using fertilizer-driven forward osmosis – Experimental and machine learning approaches

Water recovery from municipal wastewater can augment freshwater resources to meet increasing demand. An osmotic-driven membrane separation process- forward osmosis (FO) is currently being explored as a sustainable technology. This work proposes to address the challenges associated with FO namely (i) robust membrane and (ii) draw solute (DS) recovery. Robust thin-film nanocomposite membranes incorporating a) nickel ferrite or b) nitrogen-enriched nanoporous polytriazine (NENP-1) covalent organic framework were fabricated with enhanced hydrophilicity, surface roughness and anti-fouling properties. The optimum membranes M2 and C2 displayed a pure water flux of 4.86 ± 0.11 and 5.4 ± 0.2 L/m2h respectively and a specific reverse solute flux (SRSF) <<1 when using 1 M NaCl solution as the DS (feed solution – DI water). Fertilizer-driven FO (FDFO) was proposed as the diluted DS need not be recovered but could be used directly for irrigation. The pure water flux for both M2 and C2 membranes were in the following order for the fertilizers used as DS (1 M) - (NH4)2SO4 + (NH₄)₂HPO₄ > (NH4)2SO4 > (NH₄)₂HPO₄ which indicates that the mixed ions in the DS enhanced the water permeance. In all cases, the SRSF was < 1 g/L indicating the feasibility of the process. The membranes exhibited a TOC removal of > 90 % from synthetic municipal wastewater containing persistent organic pollutants and personal & pharmaceutical care products and the membranes could be regenerated after washing with a 10 mM solution of SDS for 5 cycles of operation. Further, ANN was used to develop a predictive model for water flux in FO membranes and the optimized architecture of 7–5–50–40–1 displayed a remarkable overall R2 value of 0.98 (MSE= 0.027). The FDFO process using the fabricated thin-film nanocomposite membranes holds enormous potential to be investigated in larger-scale studies.

Boosted performance of thin-film nanocomposite membranes based on phytic acid functionalized Zr-MOF for nanofiltration

Endowed with designable pore structure and intrinsically interconnected channels, metal-organic frameworks (MOFs) offer immense potential as functional nanofillers to boost the performance of nanocomposite membranes. However, achieving optimal pore size matching between MOFs and the polymer matrix while maintaining robust interfacial affinity remains a significant challenge in fabricating high-performance nanocomposite membranes. Herein, natural organic polyphosphate phytic acid was utilized to functionalize PCN-224 to narrow its pore size and enhance the polymer affinity. Thin-film nanocomposites containing mPCN-224 were afterward synthesized on the polysulfone support through a combined approach of anodic electrophoretic deposition (EPD) and vacuum filtration-assisted interfacial polymerization (VF-IP). The incorporation of mPCN-224 nanoparticles not only enhanced the hydrophilicity and electronegativity of the polyamide film but also led to a substantial reduction in film thickness. This is likely attributed to lessened piperazine supply at the interface, related to its limited diffusion at the presence of negatively charged mPCN-224. The additional nanochannels provided by mPCN-224, coupled with the loose PA layer, resulted in a substantial 56.3 % increase in the water permeance of the TFN-mPCN-224 membrane, reaching 20.0 L m−2 h−1 bar−1. Additionally, the post-synthesis modification with phytic acid led to an improved Cl−/SO42− selectivity coefficient of 44, substantially higher than that of the TFN-PCN-224 membrane. This improvement was primarily attributed to the narrowed pore size of mPCN-224 and the enhanced surface electronegativity. This study introduces a pathway for developing high-performance TFN membranes based on post-synthetic modification of MOF nanofillers with phytic acid molecules.

MEMS Precision Sensors Based on Process Innovation Technology

This article introduces a novel process for achieving micro-scale thermal isolation through solid porous 3D microstructures. It proposes a method to improve existing thermal MEMS devices by utilizing thin-film membrane structures, develops a model for estimating the thermal conductivity of porous microstructures, and constructs porous 3D microstructures made of three different powder materials, studying their applicability for thermal isolation. Breakthroughs have been achieved in process preparation technology, enabling the production of precision MEMS sensors. These sensors are expected to find wide applications in smart cars, intelligent healthcare, electronic resonance sensors, and other fields.

Mixed matrix and thin-film nanocomposite membranes of PIM-1 and hydrolyzed PIM-1 with Ni- and Co-MOF-74 nanoparticles for CO2 separation: Comparison of blending, grafting and crosslinking fabrication methods

The prototypical polymer of intrinsic microporosity, PIM-1, was synthesized with branched topology, then acid-hydrolyzed to introduce carboxylic acid functional groups (cPIM-1). Self-standing membranes and thin film nanocomposite (TFN) membranes were fabricated from PIM-1, cPIM-1, and Ni- or Co-MOF-74 nanoparticles (NPs), with a particular focus on TFNs for industrial viability. TFN membranes on polyacrylonitrile support were fabricated utilizing the following methods: (i) conventional blending; (ii) a grafting reaction between the hydroxyl group in the MOF-74 NPs and fluoro-groups of the chain-ends during PIM-1 synthesis; and (iii) an in-situ cross-linking reaction between the carboxylic acid groups in cPIM-1 and the metal ions of MOF-74 synthesized in-situ. Both conventional blending and grafting of PIM-1 with MOF-74 showed significant increase in permeance in TFN membranes. A grafted PIM-1 TFN membrane produced a CO2 permeance of 9600 GPU, which is roughly 170 % higher than a pristine PIM-1 thin film composite (TFC) membrane, while also improving the selectivity. After 28 days of aging, a blended TFN membrane based on PIM-1 showed a CO2 permeance of 1000 GPU and selectivities of 20.0 and 20.5 for CO2/N2 and CO2/CH4, respectively. Crosslinked cPIM-1 TFNs showed significant improvement in ideal selectivity from 65 in cPIM-1 to over 90 for CO2/N2, with permeance almost unchanged after crosslinking with Ni-MOF-74. However, small differences in the polyacrylonitrile support can result in significant changes in gas separation behavior. In mixed gas conditions, crosslinked cPIM-1/Co-MOF-74 produced an impressive 1842 GPU and CO2/N2 selectivity of 33. These results fall within the performance range that is suitable for post-combustion carbon capture.

Broadband and widely tunable second harmonic generation in suspended thin-film LiNbO3 rib waveguides

Our study demonstrates second harmonic generation (SHG) in a high confinement LiNbO3 rib waveguide through type-I birefringence phase matching of fundamental modes. The combination of micro-waveguide dispersion and material birefringence reveals unique SHG characteristics that complement the performance of standard LiNbO3 on insulator (LNOI) components. Dual-pump wavelength phase matching in the near-infrared and mid-infrared regions is shown in a given waveguide. These two wavelengths can be positioned in the 1.1–3.5 μm range or converge near 1.5 μm by adjusting the core waveguide size or through temperature tuning. A 25 °C temperature change enables a broad pump tunability band of 300 nm, ranging from 1350 to 1650 nm, with a conversion efficiency exceeding 40 %/W/cm2 within a single waveguide. A temperature tuning range of up to 900 nm is foreseen by tailoring the waveguide core size. In addition, a broadband response of 150 nm within the telecom window is demonstrated experimentally. The nonlinear waveguide, etched in a thin film membrane, is combined with titanium-indiffused waveguides to form a monolithic LiNbO3 component. This configuration provides low coupling losses of 0.8 dB and single-mode operation. It paves the way for a new generation of versatile and cost-effective frequency conversion components with wide-band spectral responses suitable for optical communications, environmental sensing, and quantum information processing.

A novel TFNi pervaporation membrane with g-C3N4 quantum dots for high-efficiency IPA dehydration

Pervaporation (PV) shows significant potential for the highly selective isopropanol (IPA). The pursuit of developing PV membranes with outstanding separation effect and enduring high purity permeation is an indispensable goal. Based on polyamide (PA) separation layers, a polydopamine (PDA) mixed g-C3N4 quantum dots (gCNQDs) coating as the interlayer was deposited onto a porous ceramic hollow fiber substrate to fabricate thin-film nanocomposite membranes with an interlayer (TFNi). The nanocomposite interlayer enabled the formation of a smoother and highly separated selective polyamide layer. The separation factor exhibited a 31-fold enhancement with the augmentation of the blending fraction of gCNQDs during the PDA coating process. The resulting TFNi membrane attained an exceedingly high separation factor of 10270 ± 90 with a permeate water concentration of 99.9% and demonstrated a satisfactory flux of 1.40 ± 0.08 kg⋅m-2⋅h-1 during the PV process of 90 wt% IPA dehydration at 60 °C. This study presents a fresh perspective on the implementation of nanocomposite interlayers, which is expected to expand the application of high-performance TFNi membranes in PV dehydration processes.

Modulating interfacial polymerization by combination of organic phase additives and trimesoyl chloride for preparing high-performance thin-film nanocomposite reverse osmosis membranes

Incorporating hydrophilic nanoparticles into organic phase during interfacial polymerization (IP) to establish covalent bonds with organic phase monomers has proven to be a successful approach for fabricating high-performance thin-film nanocomposite (TFN) reverse osmosis (RO) membranes. However, the effect of covalent bonds number on the membrane structure and properties remains uncertain. Herein, hydrochloric acid doped polyaniline (PANI-HCl) with a small amount of amine groups and inherent polyaniline (PANI-base) nanomaterials with a larger amount of amine groups were prepared as organic phase additives for preparing high-performance TFN RO membranes. The amine groups on the nanoparticles can bond covalently with the acyl chloride groups of trimethyl chloride (TMC), leading to the accumulation of TMCs at organic/aqueous interface and accelerates IP reaction rate, resulting in a thinner, denser polyamide layer with more leaf-like structures and free volume. The water permeance of the PANI-base-RO membrane was improved by 62.5 % from 0.8 to 1.3 Lm−2h−1bar−1, and the NaCl rejection was improved from 97.6 % to 99.4 % compared with the pristine membrane. Overall, this work highlights the beneficial impact of organic phase additives with more amine groups on enhancing the desalination performance of RO membranes, providing valuable insights for the structural design of additives and dispersing medium selection.

Ultra-fast molecular sieving in ZIF-67 and cellulose nanofibers based thin-film nanocomposite membrane

Membranes based on two-dimensional (2D) materials often show great separation efficiency and therefore have great potential in the treatment of dye wastewater. However, improving the water flux of 2D material-based membranes remains a challenge. In this work, 2D ZIF-67/CNF membranes were prepared on a polyether sulfone (PES) support layer via a simple extraction filtration method. The added CNF intertwined with 2D ZIF-67 nanosheets and formed an interlocked stacked laminar flow structure, which improved both the water flux and stability of the thin-film nanocomposite (TFN) membranes. The optimized membrane showed a water flux of 357.8 L m−2 h−1 bar−1, and its rejections of four dyes (Direct Red 80, Methyl Blue, Alkali Blue 6B and Congo Red) were all above 99.8 %. Furthermore, the optimized membrane maintained a rejection of 97 % after 8 h of continuous operation, indicating that the facile mixing of nanofibers into nanosheets can be considered a promising strategy for preparing TFN membranes for dye wastewater treatment.

Thin-Film Nanocomposite Forward Osmosis Membranes Incorporated with Hydrophilic TiO2/Fe3O4 Nanoparticles: Toward Alleviated ICP

Thin-Film Nanocomposite Forward Osmosis Membranes Incorporated with Hydrophilic TiO2/Fe3O4 Nanoparticles: Toward Alleviated ICP

Recent progress in green thin film membrane based materials for desalination: Design, properties and applications

The urgent need for sustainable solutions to address freshwater scarcity has encouraged significant research interest in green thin film membrane-based materials (GTFM) for desalination applications. This review paper comprehensively examines recent progress in these innovative membranes' design, properties, and applications. Emphasizing environmental sustainability and efficiency, various fabrication techniques such as electrospinning, layer-by-layer assembly, and template synthesis are discussed for their role in tailoring membrane structures at the nanoscale. The review highlights the importance of incorporating eco-friendly materials, such as biopolymers, natural extracts, and nanocellulose, in membrane formulations to enhance biodegradability and reduce environmental impact. Furthermore, the paper investigates the crucial properties of green film membranes, including permeability, selectivity, mechanical strength, and fouling resistance. Additionally, the review explores recent advancements in functionalization strategies, such as surface modification and incorporation of nanomaterials, to enhance membrane properties and address specific desalination challenges. The applications of green thin film membranes across various desalination technologies, including reverse osmosis, nanofiltration, and forward osmosis, are thoroughly examined. Moreover, the review discusses emerging trends and future directions in green thin film membrane research, such as multifunctional membranes, hybrid systems, and integrated desalination processes. In summary, this review provides valuable insights into the design principles, fundamental properties, and diverse applications of GTFM-based materials for sustainable desalination, paving the way for the development of next-generation water purification technologies.

Salt-responsive polyamide thin-film nanocomposite membrane based on zwitterionic polymeric nanoparticles for high-efficient dye desalination

To simultaneously improve the water permeability, selectivity, and antifouling properties of polyamide nanofiltration (NF) membranes in textile wastewater treatment, we fabricated a salt-responsive thin-film nanocomposite (TFN) membrane with the incorporation of zwitterionic polymeric nanoparticles (ZNPs) into polyamide selective layer. Herein, the ZNPs were synthesized via an inverse miniemulsion polymerization with zwitterionic monomer, amino monomer, and cross-linker reagent. The salt-responsive property of ZNPs rendered their resultant membranes TFN-ZNPs with adjustable microstructure and separation performance via varying the sodium chloride (NaCl) concentration in water. The water permeance of TFN-ZNPs was enhanced to be 1.7 times that of its pure water permeance with the 10 g L−1 NaCl solution, and the salt-responsive behavior was reversible. Moreover, this salt-responsive property endowed the membrane with outstanding separation performance for the salt/dye or dye/dye mixtures. The selectivity of TFN-ZNPs to NaCl/congo red and methyl orange/neutral blue was enhanced to ∼104 and ∼127, respectively. The TFN-ZNPs with salt-responsive property also exhibited an improved antifouling performance, i.e., the flux recovery ratio was enhanced from 85.6 % to 96.5 % by washing with NaCl solution instead of deionized water. Thus, this work provided a paradigm shift in the fabrication of salt-responsive TFN membranes for the highly efficient separation of organic molecules and inorganic salts and wastewater treatment.

Preparation of thin-film nanocomposite membrane with the addition of cysteine-modified MoS2 to enhance nanofiltration performance

Novel thin-film nanocomposite nanofiltration ((TFN)-NF) membrane was successfully fabricated by adding MoS2 functionalized with cysteine in a polysulfone (PSf) layer and the active layer to enhance separation performance in water and alcohol. A novel TFN-NF membrane was prepared through interfacial polymerization (IP), which reacts with an aqueous DETA solution containing MoS2-cys and a TMC organic solution onto the PSF/MoS2-cys support layer. A PSf support layer was incorporated with MoS2-cys, which enhanced the membrane permeability due to increasing porosity and hydrophilicity. Furthermore, MoS2 is essential in forming thin films and Turing structures of the NF membrane, resulting in enhanced permeability for water and alcohol. The prepared TFN-NF membrane has shown a notable permeability of 7.9 LMH/bar and a rejection rate of 99% for MgSO4. It also demonstrated excellent fouling resistance after three chemical cleaning cycles and long-term running. The TFN-NF membrane with MoS2 showed improved permeability for water and alcohol solvents, such as methanol and ethanol, of 5.5, 1.2, and 0.48 LMH/bar, respectively. This work would present a valuable strategy for preparing a TFN-NF membrane to retrieve alcohol solvents.

Ultra-permeable thin-film nanocomposite membrane with an asymmetric structure harvested by a heterogeneous interlayer for brackish water desalination

Constructing interlayers has proven highly efficacious in augmenting the performance of polyamide (PA) NF membranes. However, the fabrication of highly-permeable interlayered RO membranes poses significant challenges. In this work, we propose a hydrophilic-hydrophobic heterogeneous interlayer strategy to fabricate an ultra-permeable thin-film nanocomposite membrane with asymmetric two-layered structures (a-TFN). This membrane comprises a dense PA upper layer doped with ordered ZIF-8 nanocrystals and a porous dendrimer lower layer. The heterogeneous interlayer, characterized by nonuniform wettability, is more supportive of the eruption and diffusion of MPD monomers compared to a hydrophilic interlayer, beneficial to the formation of a highly cross-linked PA layer replete with nanovoids. Additionally, the in-situ encapsulation of ZIF-8 nanocrystals within the dense PA layer provide additional transport channels, while the dendrimer layer serves as a gutter layer, collectively enhancing water transport. The resulting a-TFN membrane exhibits an unprecedented water permeance (8.67 ± 0.13 L·m−2·h−1·bar−1), outperforming state-of-the-art commercial and advanced structural RO membranes, while maintaining competitive NaCl rejection (98.1 ± 0.19 %). Furthermore, it demonstrates exceptional structural durability, resistance to compaction, and antifouling performance. This study provides valuable insights for the design of interlayered RO membranes with enhanced performance.

Engineering Interfacial Structure and Channels of Polyamide Thin-Film Nanocomposite Membranes to Enhance Permselectivity for Water Purification

Engineering Interfacial Structure and Channels of Polyamide Thin-Film Nanocomposite Membranes to Enhance Permselectivity for Water Purification

Influences of substrate pore size on the morphology and separation performance of MoS2-interlayered thin-film nanocomposite membranes

Recent studies reveal the enhancement in water permeability for thin-film nanocomposite (TFN) membranes that incorporate an interlayer (TFNi), mainly when developed using substrates with larger pores. Nevertheless, the impact of substrate pore size on the membrane's morphology and separation performance requires further exploration. The study systematically investigates how the pore size of polycarbonate track-etched (PCTE) substrates influences these factors. Findings suggest that larger pores lead to rougher membrane surfaces and higher water permeance by reducing hydraulic transport resistance. However, optimal performance on larger pores requires a thicker MoS2 interlayer, leading to a thinner polyamide layer. Specifically, on PCTE-200 substrates, the MoS2 interlayer made up of large MoS2 nanosheets creates a more tortuous path for water molecules, limiting permeance. Conversely, smaller pores than the MoS2 nanosheets' dimensions obstruct the storage and diffusion of PIP monomers, negatively affecting the polyamide film and salt rejection. These findings underscore the significance of choosing the suitable substrate and adjusting interlayer thickness for creating TFN membranes with desired separation characteristics. The study provides valuable insights into the role of substrate selection and interlayer thickness in TFNi membrane design, offering guidelines for developing high-performance membranes for various separation tasks.

Boom-Membrane Space Structure’s Incomplete Deployment After Storage in OrigamiSat-1 Ground Demonstrator

This study investigates the deployment reliability of multifunctional membrane deployable space structures that can be compactly stored and deployed in a two-dimensional direction using carbon composite booms to realize the construction of thin-film solar arrays and membrane antennas. Herein, two aspects are experimentally clarified using the structural models of a nano-satellite OrigamiSat-1, which is a 1 m-by-1 m square multifunctional deployable membrane structure demonstrator. First, a measurement system is developed to quasi-statically quantify the deployment torque of the structural models that failed to complete deployment after long-term storage and fell into an undesirable equilibrium shape. The measurement results confirm that the deployment torque decreases with long-term storage of the structure, and the torque in the deployment direction becomes negative at the deployment angle of the undesirable equilibrium shape. Therefore, as the second contribution, design modifications are made to the boom and membrane, and quasi-static and dynamic deployment tests are employed to evaluate their effects. The deployment reliability evaluation method and two design updates proposed herein will contribute to future space demonstrations and the utilization of lightweight membrane deployment structures with high packaging efficiency.

Laser Patterning of Porous Support Membranes to Enhance the Effective Surface Area of Thin-Film Composite-Facilitated Transport Membranes for CO2 Separation.

Although thin-film composite membranes have achieved great success in CO2 separation, further improvements in the CO2 permeance are required to reduce the size and cost of the CO2 separation process. Herein, we report the fabrication of composite membranes with high CO2 permeability using a laser-patterned porous membrane as the support membrane. High-aspect-ratio micropatterns with well-defined micropores on their surface were carved on microporous polymer supports by a direct laser writing process using a short-pulsed laser. By using a Galvano scanner and optimizing the laser conditions and target materials, in-plane micropatterns, such as microhole arrays, microline grating, microlattices, and out-of-plane hierarchical micropatterns, were created on porous membranes. An aqueous suspension of hydrogel microparticles doped with an amine-based mobile carrier was sprayed onto the patterned surface to form a defect-free thin separation layer. The surface area of the separation layer on the patterned support is up to 80% larger than that of flat pristine membranes, resulting in a 52% higher CO2 permeance (1106 GPU) with a CO2/N2 selectivity of 172. The laser-patterned porous membranes allow the development of inexpensive and high-performance functional membranes not only for CO2 separation but also for other applications, such as water treatment, cell culture, micro-TAS, and membrane reactors.

Enhanced Nanofiltration Performance of the PVC/PVA Thin Film Membranes for Treatment of Petroleum Refinery Wastewater through Incorporation of Amino-functionalized SBA-15 Nanoparticles

Enhanced Nanofiltration Performance of the PVC/PVA Thin Film Membranes for Treatment of Petroleum Refinery Wastewater through Incorporation of Amino-functionalized SBA-15 Nanoparticles

High-performance separation for ultra-low concentration nanoparticles with mesoporous silica thin membrane

Mesoporous silica thin film membrane (MSTF) emerges as an ideal ultrafiltration membrane for the removal of nanoparticles, ensuring the production of particle-free water. This is mainly ascribed to its uniform and narrow pore size distribution, having vertical nanochannels with low tortuosity, and being ultrathin, which helps enhance its selectivity and permeability. In this study, we demonstrated the potential of MSTF overlayed on macroporous anodic aluminum oxide (AAO) support for separating gold nanoparticles even at a very low concentration. Moreover, with the addition of pore-expanding agents, E-MSTF⊥AAO (pore size 3.12 nm) and D-MSTF⊥AAO (pore size 5.26 nm) membranes are formed, and both membranes indeed showed high rejection efficiency towards 150 ppb gold nanoparticles of sizes 10 nm and 5 nm, ∼99 %, and ∼96 %, respectively. It is also worth noting that as compared to the state-of-the-art conventional UF membranes, the E-MSTF⊥AAO membrane showed significantly high permeance of 114.1 ± 12.76 L m−2 h−1 bar−1 and 104.1 ± 50.6 L m−2 h−1 bar−1 while efficiently separating 150 ppb and 50 ppb 5 nm gold nanoparticles, respectively. Moreover, the promising long-term stability and chemical stability of the MSTF⊥AAO membrane paved a promising path for applying mesoporous silica membranes for effective nanoparticle separation in wastewater treatment and particle-free water production in industries.