Thin Film Nanocomposite Membranes Research Articles

One-pot in situ synthesis of ZIF particles to prepare thin-film nanocomposite membranes for CO2 separation

Mixed matrix membranes (MMMs) are more likely to break the Robeson upper bound because they combine the pros of both organic and inorganic membranes. However, in the conventional MMM preparation processes, multi-steps are normally needed and, in many cases, the particle agglomeration and consequent non-selective voids are unavoidable, resulting in poor carbon dioxide (CO2) separation performances. In addition, the agglomeration makes it challenging to fabricate thin-film nanocomposite (TFN) membranes. In this study, zeolitic imidazolate framework (ZIF)-8- and ZIF-67-based TFN membranes were fabricated via a facile one-pot in situ synthesis protocol. The ZIF particles were synthesized in the polymeric solution, then the TFN membranes were fabricated by a dip coating method. With a casting solution concentration of 1.5 wt.%, a selective layer with a thickness of ∼300 nm can be prepared on the porous polyacrylonitrile (PAN) support. The results of thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), Fourier Transform Infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) showed that ZIFs were successfully synthesized in the casting solution. At 35 °C and 2 bar, the membrane containing 5 wt.% ZIF-67 had a CO2 permeance of 223.35 gas permeation unit (GPU), which was 16.55 % higher than that of pure Pebax.

Construction of low-resistance nano-transport channels with UiO-66-(NH2)2 “transmembrane” in polyamide layer structure for efficient nanofiltration

Metal-organic frameworks (MOFs) is always a research hotspot as the modifier for fabrication of thin-film nanocomposite (TFN) membrane due to their excellent chemical tunability and suitable pore size. However, the traditional strategy for the involvement of MOFs into interfacial polymerization (IP) process has its limitations, as the addition of MOFs only serve to modulate the structure of the polyamide (PA) layer and to optimize the transport path of water molecules, rather than play an important role in selectively sieving solutes. To solve the problem that MOF embedded under the PA layer cannot directly participate in solute sieving, this study designed a “transmembrane” structure of MOF in the PA layer. Here, the feasibility of 1,3,5-Benzenetricarbonyl chloride modified UiO-66-(NH2)2 was verified based on Gibbs free energy calculations. By adding chlorinated UiO-66-(NH2)2 nanomaterials in the dual IP process, a high-throughput nanofiltration membrane was innovatively constructed. In contrast to conventional thin-film composite membrane prepared by only one IP process, the sieving mechanism no longer relied solely on the free volume of the PA chain segments. Instead, it was determined by the combination of the pore channels of UiO-66-(NH2)2 and the matrix gaps. Based on density functional theory (DFT), the calculated diffusion energy barriers of H2O and Na2SO4 in UiO-66-(NH2)2 and PA matrices reveal the reasons for the improvement of water flux and changes in retention rate of TFN membranes. In addition, the gap size between PA-MOFs was determined by comparing the solvation and de-solvation structures of dye molecules. This work provides a new theoretical basis for explaining the changes in the separation performance of TFN membranes, and offers new ideas for the development of novel TFN membrane structures.

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

Pentahomoserine functionalized graphene oxide decorated polyamide thin film for enhanced separation of green tea polyphenols

The isolation of valuable compounds from the byproducts of food processing industries presents a significant contemporary challenge. Thin film nanocomposite (TFN) membranes have been identified as potential media for separating bioactive compounds. In this work, pentahomoserine functionalized graphene oxide (FGO) based TFN membranes were prepared for the effective separation of tea polyphenols epigallocatechin (EGC) and epigallocatechin gallate (EGCG). The nanocomposite selective polyamide (PA) layer was prepared through the dispersion of FGO in an aqueous monomer solution. The prepared membranes possess high average surface roughness with improved hydrophilicity and thermal stability. Additionally, FGO membranes contain more hydroxyl or carboxyl groups with cross-linked PA layer through interfacial polymerization (IP) process. Moreover, FGO membranes featured increased hydroxyl or carboxyl groups, facilitating cross-linking with the PA layer via intermolecular forces. The effects of amine functionality on the membrane characteristics such as surface morphology, roughness and hydrophilicity were also investigated. Remarkably, the membranes demonstrated rejection efficiency of 96.3% towards polyphenols. Furthermore, comprehensive assessments of reusability performance of the membrane highlighted their potential for industrial applications. This study provides valuable insights into the fabrication of highly efficient TFN membranes for biomolecule separation across diverse technological domains.

Distinct Efficacies of Interlayers in Tailoring Polyamide Nanofiltration Membrane Performance for Organic Micropollutant Removal: Dependent on Substrate Characteristics.

Interlayered thin-film nanocomposite (TFN) membranes have shown the potential to boost nanofiltration performance for water treatment applications including the removal of organic micropollutants (OMPs). However, the effects of substrates have been overlooked when exploiting and evaluating the efficacy of certain kinds of interlayers in tailoring membrane performance. Herein, a series of TFN membranes were synthesized on different porous substrates with identical interlayers of metal-organic framework nanosheets. It was revealed that the interlayer introduction could narrow but not fully eliminate the difference in the properties among the polyamide layers formed on different substrates, and the membrane performance variation was prominent in distinct aspects. For substrates with small pore sizes exerting severe water transport hindrance, the introduced interlayer mainly enhanced membrane water permeance by affording the gutter effect, while it could be more effective in reducing membrane pore size by improving the interfacial polymerization platform and avoiding PA defects when using a large-pore-size substrate. By matching the selected substrates and interlayers well, superior TFN membranes were obtained with simultaneously higher water permeance and OMP rejections compared to three commercial membranes. This study helps us to objectively understand interlayer efficacies and attain performance breakthroughs of TFN membranes for more efficient water treatment.

A Comprehensive Examination of Low GO-Silica Loading in Pebax1657/PEI Thin Film Nano-composite Membranes for Gas Dehydration

The aim of this study was to assess the effectiveness of blending Pebax1657 polymer with SiO2-GO nanoparticles in the production of TFN membranes for N2 gas dehydration. By utilizing dip coating, nanoparticles were incorporated at varying concentrations. The resulting nanocomposites were subjected to thorough analysis to investigate their chemical structure, physical morphology, surface topology, and thermal stability. This examination encompassed the application of FTIR, SEM, CA, AFM, and TGA techniques. The results demonstrated that the samples displayed good thermal stability and a highly hydrophilic surface. The investigation concluded that the dehydration properties of TFN membranes are influenced by a variety of factors, such as morphology, plasticization, and hydrophilic attributes. The effectiveness of the system is contingent upon the contribution made by each individual nanoparticle. The impact of SiO2 nanoparticles in their pure form is clearly evident in the 0.5 wt% loaded composite membrane membrane. When 0.5% of SiO2 nanoparticles are introduced into the composite membrane, the morphology closely resembles the ideal state due to the non-porous nature of SiO2 and the low concentration of nanoparticles, hence a selectivity of ~560 is experienced. Fortunately this selectivity is beyond the need of the industries. Consequently, there was a reduction in water vapor and nitrogen permeability, resulting in a heightened selectivity ratio. These discoveries hold considerable importance in industrial settings, as they offer a more comprehensive understanding of the topic.

Functionalised carbon nanotube thin film nanocomposite membranes: A comparison study on the role of backbone monomers and hydraulic pressure on membrane's performance and fouling

Thin film nanocomposite (TFN) reverse osmosis (RO) and nanofiltration (NF) membranes have attracted considerable attention for industrial applications in recent years. Among recent nanomaterials used in the fabrication of TFN membranes, carbon nanotubes (CNTs) have gained significant interest due to their unique structure (e.g., tubular shape, mechanical strength, porosity, etc.). Here, the effects of multi-walled carbon nanotubes (MWCNTs) with different functional groups as one of the well proven nanchannel structures and their interaction with two typical monomers, MPD and PIP, were thoroughly investigated. All fabricated membranes were analysed using SEM, FTIR, AFM and contact angle analyzer. Pressure variation significantly affected the performance of membranes over 24 hours of testing. The membranes incorporated with polypyrrole (PPy) modified MWCNTs showed promising results with nearly 37 % and 99 % water flux improvement for the TFN-RO and NF membranes, respectively, compared to the bare (unmodified) TFC RO/NF membranes. Specifically, the water flux of the RO OX-MWCNTs-PPy membrane increased from 18.9 to 25.5 L.m−2.h−1, while the NF OX-MWCNTs-PPy membrane's water flux rose from 45.2 to 90.1 L.m−2.h−1. The salt rejection of RO and NF remained relatively high, with over 90 % salt rejection against NaCl and Na2SO4 for RO and NF membranes. The NF OX-MWCNTs-PPy membrane exhibited a 98.2 % rejection rate for Na2SO4, and the RO OX-MWCNTs-PPy membrane showed around a 98.8 % rejection rate for NaCl. The TFN membranes showed less fouling tendency compared to the TFC membranes. In general, the integration of MWCNTs with various functional groups significantly enhanced the water flux and salt rejection properties of these membranes. Specifically, the modified membranes showed considerable improvements in water flux and maintained high salt rejection rates. Additionally, the interaction between MWCNTs and PIP monomers in TFN-NF membranes exhibited a stronger affinity compared to MPD monomers in TFN-RO membranes, indicating a more promising performance for NF applications. The findings suggest that TFN-NF membranes incorporating MWCNTs hold great promise for future industrial use, offering enhanced performance and reduced fouling rates.

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.

Synthesis of aminopropyl triethoxysilane/melamine incorporated superhydrophilic membranes for simultaneous removal of oil, metals, and Salt ions from produced water

Water treatment has turned out to be more important in most societies due to the expansion of most economies and to advancement of industrialization. Developing efficient materials and technologies for water treatment is of high interest. Thin film nanocomposite membranes are regarded as the most effective membranes available for salts, hydrocarbon, and environmental pollutants removal. These membranes improve productivity while using less energy than conventional asymmetric membranes. Here, the polyvinylidene fluoride (PVDF) membranes have been successfully modified via dip single-step coating by silica-aminopropyl triethoxysilane/trimesic acid/melamine nanocomposite (Si-APTES-TA-MM). The developed membranes were evaluated for separating the emulsified oil/water mixture, the surface wettability of the membrane materials is therefore essential. During the conditioning step, that is when the freshwater was introduced, the prepared membrane reached a flux of about 27.77 L m−2 h−1. However, when the contaminated water was introduced, the flux reached 18 L m−2 h−1, alongside an applied pressure of 400 kPa. Interestingly, during the first 8 h of the filtration test, the membrane showed 90 % rejection for ions including Mg2+, and SO42− and ≈100 % for organic pollutants including pentane, isooctane, toluene, and hexadecane. Also, the membrane showed 98 % rejection for heavy metals including strontium, lead, and cobalt ions. As per the results, the membrane could be recommended as a promising candidate to be used for a mixture of salt ions, hydrocarbons, and mixtures of heavy metals from wastewater.

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.

A high-performance TFN membrane prepared by a novel PE support layer, a polydopamine interlayer, and a doped MoS2 quantum dots@ZnO nanocomposites-incorporated polyamide active layer

Herein, thin film nanocomposite (TFN) membranes were prepared with excellent chemical stability and separation performance for organic solvent nanofiltration (OSN) applications. The support membrane was synthesized via a new approach, in which a blend of two immiscible polymers, i.e. high density polyethylene (HDPE)-polystyrene (PS), which were compatibilized with styrene-ethylene-butylene-styrene (SEBS), was prepared through mixing by a Brabender, followed by fabricating blend sheets through a hot press machine. The PE support was then prepared by extracting the PS/compatibilizer phase from the blend sheet. The hydrophilicity of the PE support membrane was considerably enhanced with a polydopamine (PDA) layer. Different nanoparticles including nanoflower (NF) ZnO, nanosphere (NS) ZnO, MoS2 Quantum dots-nanoflower ZnO nanocomposite (QDs@NF ZnO), and MoS2 Quantum dots-nanosphere ZnO nanocomposite (QDs@NS ZnO) were incorporated into the polyamide (PA) active layer of the membranes to enhance the performance of the TFN membranes. The separation performance of the TFN membranes was investigated for rejecting different dyes dissolved in methanol. Our results demonstrate outstanding separation performance, with a dye rejection of 99.6 %, 99.6 %, 99.8 %, and 99.9 % for methylene blue, crystal violet, rhodamine B, and methyl green, respectively. Additionally, the TFN membranes incorporated with QDs@NF ZnO nanoparticles showed great solvent resistance, with a methanol permeance up to 6.7 L/m2.h.bar after activation with dimethylformamide.

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.

Synergistic Construction of Sub-Nanometer Channel Membranes through MOF–Polymer Composites: Strategies and Nanofiltration Applications

The selective separation of small molecules at the sub-nanometer scale has broad application prospects in the field, such as energy, catalysis, and separation. Conventional polymeric membrane materials (e.g., nanofiltration membranes) for sub-nanometer scale separations face challenges, such as inhomogeneous channel sizes and unstable pore structures. Combining polymers with metal–organic frameworks (MOFs), which possess uniform and intrinsic pore structures, may overcome this limitation. This combination has resulted in three distinct types of membranes: MOF polycrystalline membranes, mixed-matrix membranes (MMMs), and thin-film nanocomposite (TFN) membranes. However, their effectiveness is hindered by the limited regulation of the surface properties and growth of MOFs and their poor interfacial compatibility. The main issues in preparing MOF polycrystalline membranes are the uncontrollable growth of MOFs and the poor adhesion between MOFs and the substrate. Here, polymers could serve as a simple and precise tool for regulating the growth and surface functionalities of MOFs while enhancing their adhesion to the substrate. For MOF mixed-matrix membranes, the primary challenge is the poor interfacial compatibility between polymers and MOFs. Strategies for the mutual modification of MOFs and polymers to enhance their interfacial compatibility are introduced. For TFN membranes, the challenges include the difficulty in controlling the growth of the polymer selective layer and the performance limitations caused by the “trade-off” effect. MOFs can modulate the formation process of the polymer selective layer and establish transport channels within the polymer matrix to overcome the “trade-off” effect limitations. This review focuses on the mechanisms of synergistic construction of polymer–MOF membranes and their structure–nanofiltration performance relationships, which have not been sufficiently addressed in the past.

Covalently modified MoS2 for the fabrication of interlayered thin film composite membranes with excellent structural stability against swelling and drying in organic solvent nanofiltration

Thin film nanocomposite (TFNi) membranes interlayered with 2D nanomaterials are promising for organic solvent nanofiltration (OSN) applications. However, swelling and drying problems can arise due to the instability of the 2D nanomaterial interlayer in different solvents and humidity conditions. To address this issue, covalently modified molybdenum disulfide (MoS2) nanosheets (MoS2–COOH and MoS2–CONH2) were used as interlayers in the fabrication of TFNi membranes. The covalent groups acted as spacers to stabilize the interlayer spacing of the MoS2 interlayer and regulate its structural stability in diverse solvents and drying conditions. The TFNi membranes interlayered with MoS2–COOH and MoS2–CONH2 nanosheets demonstrated excellent structural stability and maintained their high permeance even after exposure to various solvents and drying conditions. The TFNi-MoS2-CONH2 membrane exhibited the highest permeance of 8.60 ± 0.23 L m−2 h−1 bar−1 for MeOH, with a high rejection of 87.1 ± 1.3 % for Evans Blue (EB). Furthermore, the TFNi membranes exhibited sustained separation performance throughout the 72 h test, demonstrating their structural stability. This study highlights the potential of TFNi membranes interlayered with covalently modified MoS2 nanosheets for OSN applications, providing high permeance and structural stability in diverse solvents and drying conditions.

A Tale of Two Separation Properties: Bulk and Thin Films of Mixed Matrix Materials

AbstractMixed matrix materials (MMMs) integrating excellent processability from polymers and distinct separation properties from nanofillers are of interest for membrane gas separations, and they are often made into freestanding films (>100 µm) to demonstrate superior gas separation properties. However, they are difficult to fabricate into thin‐film nanocomposite (TFN) membranes due to interfacial incompatibility between polymers and nanofillers. Here TFN membranes based on MMMs (as thin as 200 nm) are successfully developed comprising amorphous poly(ethylene oxide) (aPEO) and UiO‐66‐NH2 enabling strong hydrogen bonds between the two matrices. Increasing the UiO‐66‐NH2 loading unexpectedly decreases CO2 permeability in freestanding films, but it surprisingly leads to the best CO2/N2 separation properties in the membranes at a loading of 10 mass% (CO2 permeance of 2900 GPU and CO2/N2 selectivity of 48). Nanoconfinement significantly influences the morphological and gas separation properties of the MMM layer. The membrane with 10 mass% UiO‐66‐NH2 demonstrates mixed‐gas CO2 permeance of 1400 GPU and CO2/N2 selectivity of 76 in the presence of 1.2 mol% water vapor at ≈23 °C, surpassing Robeson's upper bound. The membrane also demonstrates stable CO2/N2 separation performance when challenged with real flue gas for 700 h continuously.

GO and surfactant assisted regulation of polyamide nanofiltration membranes for improved separation performance

Fabricating nanofiltration membranes with high water permeance and selectivity by tailoring the structure and morphology is crucial to efficient water purification. In this work, the fabrication of thin film nanocomposite (TFN) nanofiltration membranes by combining two methods, the surfactant-assembly interfacial polymerization (SARIP) and the addition of graphene oxide (GO) or ionic liquid functionalized graphene oxide (GO-IL) for the preparation of the selective PA layer on a novel porous substrate is reported. For the preparation of the porous substrate, mechanically robust, aromatic polyethers containing polar pyridine units (PDSPP) were chosen targeting to improved hydrophilicity and thus enhanced water permeability. The anionic sodium dodecyl sulfate (SDS) surfactant was used to regulate the interfacial polymerization thereby enabling the formation of dense PA layers with high cross-linking degree and consequently high salt rejections. On the other hand, the addition of GO/GO-IL nanosheets could impart hydrophilicity and antifouling properties. The novel porous PDSPP substrate was selected for the fabrication of TFN membranes due to its improved water permeability and superior salt rejection and increased hydrophilicity compared to commercial PSf substrate. The detailed study of the fabricated TFN membranes by ATR-FT-IR, SEM, AFM, XPS, contact angle measurements revealed the formation of polyamide selective layers with rougher surfaces, increased hydrophilicity and high cross-linking degrees (from 44 % to 94 %), resulted from the synergistic effect of SDS and GO incorporation. Moreover, the prepared TFN membranes exhibited high salt rejections while maintaining a moderate water permeability. In particular, the membrane containing the neat GO (TFNGO50) displayed excellent Na2SO4 and MgSO4 rejections (98.8 % and 99.5 %, respectively) while the NaCl rejection was 47.0 % and a water permeability value of 4.2 L m-2h−1 bar−1. The divalent salt rejections were among the highest values reported in the literature in comparison with commercial NF membranes and TFN membranes containing GO/functionalized GO. When GO-IL nanosheets were embedded in the PA layer, the water permeability was slightly improved while the salt rejections were significantly reduced compared to TFNGO50. Lastly, the incorporation of GO enhanced the anti-fouling properties of the prepared membranes due to increased hydrophilicity of the PA surface.

Influence of graphene oxide additives on the NF separation of triazine-based H2S scavenging compounds using advanced membrane technology

This work proposes an innovative approach for the membrane separation of spent and unspent H2S scavengers (SUS) derived from the application of MEA-triazine in offshore oil and gas production. Modified nanofiltration membranes were fabricated by incorporating graphene oxide (GO) and polyvinyl alcohol (PVA) into a thin film composite (TFC) to obtain a thin film nanocomposite (TFN) with enhanced permeability. In addition, various immobilization strategies for GO were investigated. The performance of the membranes and the effect of the GO loading were evaluated in terms of permeability, fouling propensity, and rejection of key components of the SUS, i.e., MEA-triazine (unspent scavenger), dithiazine (spent scavenger), and monoethanolamine, operating on a sample of SUS wastewater obtained from an offshore oil and gas platform. Various characterization techniques, such as contact angle, FTIR, XRD, SEM, TGA, and AFM, were employed to evaluate the structure, composition, and hydrophilicity of the membrane. The results show a remarkable increase in permeability (from 0.22 Lm-2 h−1 bar−1 for the TFC to 5.8 Lm-2 h−1 bar−1 for the TFN membranes), due to the enhanced hydrophilicity from GO incorporation. The strong interfacial interaction between GO and PVA within the TFN membrane results in negligible nanofiller leaching. The incorporation of GO moderately increases the rejection of the unspent scavenger (63%–73%, 62%–79%, 62%–80%, and 68%–76%), while drastically increasing the rejection of the spent scavenger, which is approximately null for the TFC membrane without GO and increases up to 58% in the TFN membrane with GO. Therefore, while the proposed membranes cannot be used for the selective separation of the unspent form the spent scavenger, they can achieve substantial recovery of all the key components contained in the SUS to avoid their discharge into the sea.

Robust CA-GO-TiO2/PTFE Photocatalytic Membranes for the Degradation of the Azithromycin Formulation from Wastewaters.

We have developed an innovative thin-film nanocomposite membrane that contains cellulose acetate (CA) with small amounts of TiO2-decorated graphene oxide (GO) (ranging from 0.5 wt.% to 2 wt.%) sandwiched between two polytetrafluoroethylene (PTFE)-like thin films. The PTFE-like films succeeded in maintaining the bulk porosity of the support while increasing the thermal and chemical robustness of the membrane and boosting the catalytic activity of TiO2 nanoparticles. The membranes exhibited a specific chemical composition and bonding, with predominant carbon-oxygen bonds from CA and GO in the bulk, and carbon-fluorine bonds on their PTFE-like coated sides. We have also tested the membranes' photocatalytic activities on azithromycin-containing wastewaters, demonstrating excellent efficiency with more than 80% degradation for 2 wt.% TiO2-decorated GO in the CA-GO-TiO2/PTFE-like membranes. The degradation of the azithromycin formulation occurs in two steps, with reaction rates being correlated to the amount of GO-TiO2 in the membranes.