Control Thin Film Composite Membrane Research Articles

Retarded Interfacial Formation of Polyamine-Based Nanofiltration Membranes with Pyromellitic Acid: Separation, Acid Stability, and Antifouling Performance

Crosslinked and additive-added polyamide thin-film composite (TFC) nanofiltration (NF) membranes formed by the conventional interfacial polymerization (IP) process have shown good performances. However, studies on polyamine TFC NF membrane prepared via an adjusted IP process with low-cost acid ligands as an interfacial additive for improved liquid-based separation are still lagging. In this regard, a polyamine-based TFC NF membrane synthesized by retarding the interfacial polymerization (IP) process with pyromellitic acid (PMA) (a polycarboxylate acid ligand) is herein reported. The PMA-adjusted membrane displayed a superb range of pure water fluxes from 9.8 to 20.4 L m–2 h–1 bar–1, with the best-performed membrane achieving up to 95.1% for Na2SO4 rejection. Thus, the water permeability of the PMA-TFC membrane is ∼2.4 times as high as the control TFC membrane. The best-performed PMA-TFC membrane showed good hydrophilicity, pressure resistance, and long-term filtration stability. In addition, the membrane structural stability was maintained with ∼3.9% declination in salt rejection after 30 days of immersion in 0.1 M HNO3 solution. Also, an impressive fouling resistance was achieved after three-cycle of bovine serum albumin fouling tests. This work, therefore, offers a more feasible way of designing polyamine-based NF membranes with good prospects in water reuse and nitric acid-generating wastewater treatment application.

Evading the permeance-selectivity trade-off dilemma in electrospray-assisted interfacial polymerization polyamide thin-film composite membrane through electrospinning nanofibers interlayer

The permeance-selectivity trade-off has been a long-standing problem in membrane separation process, which has limited the application potential of many membrane separation techniques. Here we introduce chitosan (CS) nanofibers interlayer to optimize the substrate to improve the separation performance of thin-film composite (TFC) membrane fabricated by electrospray-assisted interfacial polymerization (EIP). A series of characterizations were conducted and the results showed that the introduction of CS nanofibers prevented polyamide from invading the substrate's pores, and increased the content of interfacial amine monomer to promote interfacial polymerization (IP) reaction. At the same time, the enhanced confinement effect formed a rougher selection layer, providing more water transport paths and enhancing the hydrophilicity of the membrane. Compared with the control TFC membrane with polyethersulfone (PES) substrate, the TFC/CS/PES membrane with CS/PES composite substrate showed excellent separation performance, achieving 4.5 times increase in permeance while maintaining a high MgCl2 rejection. Our work provides a new strategy for optimizing the substrate and improving the properties of the membranes.

Nano-striped polyamide membranes enabled by vacuum-assisted incorporation of hierarchical flower-like MoS2 for enhanced nanofiltration performance

Introducing nanomaterials into the polyamide layer of thin-film composite (TFC) membranes during interfacial polymerization process can customize the physicochemical properties of membranes and further enhance the membrane permeability without sacrificing selectivity. In this study, we prepared novel thin-film nanocomposite (TFN) nanofiltration membranes by varying the deposition density of hierarchical flower-like structured molybdenum disulfide (HF–MoS2) with the assistance of vacuum filtration. Ascribed to the unique 3D hierarchical structure of HF–MoS2, a nano-sized striped polyamide film with a decreased thickness of 30–40 nm was formed, which increased the membrane effective filtration area and reduced the mass transfer resistance for water permeation. In addition, compared to the control TFC membrane, the TFN membranes possessed relatively looser polyamide layers with higher surface hydrophilicity and more negative surface charges. When the deposition density of HF–MoS2 was 10 μg/cm2, the optimal performance of the TFN membranes was obtained, i.e., a water permeability of 18.4 L m−2 h−1 bar−1 and rejections above 98% for Na2SO4 and MgSO4. Moreover, the optimal TFN membrane demonstrated an excellent separation performance and structure stability in the mixed salt solution and the long-term filtration test of 120 h, respectively. This work provides a novel approach to design high-performance TFN membranes applied for water/wastewater treatment.

Layer-by-layer assembly of alginate/Ca2+ as interlayer on microfiltration substrate: Fabrication of high selective thin-film composite forward osmosis membrane for efficient heavy metal ions removal

Forward osmosis (FO) technology has the merit potential to remove heavy metal ions from wastewater. However, the deficiency of FO membranes with low selectivity and permeability has hampered the scale-up and development of this technology. In this work, we coated a hydrophilic alginate/Ca2+ thin layer through the layer-by-layer (LbL) assembly as an interlayer on polyethersulfone (PES) microfiltration (MF) substrate to enhance the separation performance of the thin-film composite (TFC) membrane. The interlayer thickness was controlled by the LbL cycles (1–7 cycles), and its effect on surface properties of substrates in terms of hydrophilicity and pore size was investigated thoroughly. Then the influence of interlayer LbL cycles on the polyamide (PA) synthesis through interfacial reaction was studied. Results show that the interlayer prevents the PA layer's intrusion into the substrate pores and provides a hydrophilic and smooth surface to synthesize a defect-free PA layer. SEM images show that a dense, uniform, and defect-free PA rejection layer was formed on interlayer-coated MF substrates. FO performance result also verified the positive effect of interlayer on TFC membrane performance, where TFC-LbL.5 membrane (with 5 LbL cycles of alginate/Ca2+) showed 2 times higher water flux than control TFC membrane (23.3 LMH compared to 9.2 LMH). In the TFC-LbL.5 membrane, the defect-free PA active layer formed on the alginate/Ca2+ interlayer acted as a favorable barrier for different heavy metal ions (Cr3+, Co2+, and Hg2+) with the rejection of more than 99% under FO mode. This work offers a novel opportunity for the practical construction and development of high-efficiency TFC-FO membranes for heavy metal removal applications.

Surface Modification of a Thin-Film Composite (TFC) Nanofiltration Membrane with 3-Aminopropyltriethoxysilane (APTES) for Efficient Dye–Salt Separation

Nanofiltration (NF) technology is attractive in desalting and concentrating dyeing wastewater in the textile industry. A highly efficient NF membrane is critical in reducing the cost of the process. Here, a facile and reliable approach to prepare an NF membrane for the selective separation of dye/salt is proposed by surface grafting of 3-aminopropyltriethoxysilane (APTES) on a fresh polyamide (PA) layer after interfacial polymerization (IP). A thin layer of APTES with a thickness of ∼64 nm was found successfully covalently bonded onto the PA surface via esterification and amidation reactions. The thin-film composite (TFC)-1.0 membrane grafted with 10% APTES achieved a high water permeance of 44.8 L m–2 h–1 bar–1, which was 4.7 times higher than that of the control TFC membrane. Interestingly, the rejection of monovalent salt (NaCl, 11.5%) and divalent salt (Na2SO4, 17.2%) decreased significantly, while the rejection for different dyes (Congo red, reactive blue-19, Coomassie blue G-250, and methyl blue) remained over 99.0%. These noticeable changes in separation performances could be attributed to the large pore size of the active layer, resulting from the interference of APTES on the post-cross-linking of a PA network. The poly(ethylene glycol) (PEG) filtration experiments confirmed that the mean pore size of the membrane was enlarged significantly from 0.51 to 1.17 nm after surface modification. Finally, the modified membrane showed good long-term stability and excellent separation efficiencies in fractionation of a high salinity Congo red/NaCl (0.2/50 g L–1) mixture. Overall, this work provides a practical strategy to prepare a permeable and selective NF membrane for dye and salt separation by surface grafting of the nascent PA layer.

Enhancing the Permselectivity of Thin-Film Composite Membranes Interlayered with MoS2 Nanosheets via Precise Thickness Control.

The demand for highly permeable and selective thin-film composite (TFC) nanofiltration membranes, which are essential for seawater and brackish water softening and resource recovery, is growing rapidly. However, improving and tuning membrane permeability and selectivity simultaneously remain highly challenging owing to the lack of thickness control in polyamide films. In this study, we fabricated a high-performance interlayered TFC membrane through classical interfacial polymerization on a MoS2-coated polyethersulfone substrate. Due to the enhanced confinement effect on the interface degassing and the improved adsorption of the amine monomer by the MoS2 interlayer, the MoS2-interlayered TFC membrane exhibited enhanced roughness and crosslinking. Compared to the control TFC membrane, MoS2-interlayered TFC membranes have a thinner polyamide layer, with thickness ranging from 60 to 85 nm, which can be tuned by altering the MoS2 interlayer thickness. A multilayer permeation model was developed to delineate and analyze the transport resistance and permeability of the MoS2 interlayer and polyamide film through the regression of experimental data. The optimized MoS2-interlayered TFC membrane (0.3-inter) had a 96.8% Na2SO4 rejection combined with an excellent permeability of 15.9 L m-2 h-1 bar-1 (LMH/bar), approximately 2.4 times that of the control membrane (6.6 LMH/bar). This research provides a feasible strategy for the rational design of tunable, high-performance NF membranes for environmental applications.

A novel ceramic-based thin-film composite nanofiltration membrane with enhanced performance and regeneration potential

The rational design of a ceramic-based nanofiltration membrane remains a significant challenge due to its performance and fabrication cost. Herein, we report a high-performance ceramic-based thin-film composite (TFC) membrane fabricated via a typical interfacial polymerization on an interwoven net substrate assembled by titanium dioxide (TiO2) nanowires. The chemical properties and morphologies were systematically investigated for ceramic substrates and their corresponding TFC membranes. Due to the significantly improved hydrophilicity of the TiO2 framework, more reactive amine monomers were uniformly adsorbed on the modified surface of the ceramic substrate, yielding an ultrathin polyamide layer with less resistance. In addition, the smooth surface and decreased pore size of the TiO2 framework contributed to forming a defect-free polyamide layer. As a result, the obtained ceramic-based TFC membrane evinced high permeance of 26.4 L m−2 h−1 bar−1 and excellent salt rejection efficiency, leading to simultaneous improvements compared with the control TFC membrane without the TiO2 framework. Notably, the potential regeneration ability of the ceramic-based TFC membrane could be achieved via facile low-temperature calcination and re-polymerization process due to the varied thermostability between the polyamide layer and the robust ceramic substrate. The operation of regeneration helped to prolong the lifetime and decrease the cost for the ceramic-based TFC membrane. This research provides a feasible protocol to fabricate sustainable ceramic-based nanofiltration membranes with enhanced performance for water treatment.

Biocidal surfactant-assisted fabrication of thin film composite membranes with excellent and durable anti-biofouling performance

Biofouling is a critical problem for water treatment and desalination membranes because it significantly reduces process efficiency. Here, we present a new facile strategy for the fabrication of anti-biofouling polyamide (PA) thin film composite (TFC) membranes that involves the addition of the biocidal cationic surfactant, benzalkonium chloride (BAC), to an amine monomer solution during interfacial polymerization. The optimal addition of BAC effectively promotes and uniformizes amine diffusion toward the organic phase by reducing organic–aqueous interfacial tension and improving solution wettability on the support, producing a denser and more permeable PA structure. Moreover, BAC was strongly integrated into the PA matrix, presumably via strong chemical interactions between BAC and PA (i.e., electrostatic, hydrophobic, π–π stacking, and cation–π interactions), which enhanced the surface hydrophilicity and anti-bacterial activity of the membrane. Consequently, the BAC-incorporated TFC (BAC-TFC) membrane exhibited significantly enhanced reverse osmosis separation and anti-biofouling performance in comparison with the control TFC membrane. When compared with the conventional surfactant, sodium dodecyl sulfate, BAC resulted in remarkably improved biofouling resistance with comparable performance enhancement. Furthermore, the strong incorporation of BAC into PA led to the long-term durability of the BAC-TFC membrane in terms of its separation and anti-biofouling performance.

High-Performance Thin-Film nanocomposite forward osmosis membranes modified with Poly(dopamine) coated UiO66-(COOH)2

• Surface functionalization of UiO-66 with polydopamine (UiO-PDA). • Thin film nanocomposite (TFN) forward osmosis (FO) membranes were fabricated by incorporating UiO-PDA. • UiO-PDA as a hydrophilic nanomaterial enhanced the separation performance of TFN-FO membranes. • The UiO-PDA modified TFN membrane exhibited better anti-fouling performance and Cu +2 ions rejection in comparison with bare TFC one. In this study, a new family of thin-film nanocomposite forward osmosis (TFN-FO) membranes was synthesized by embedding polydopamine (PDA) coated UiO-66-(COOH) 2 (UiO-PDA) nanofiller in polyamide (PA) rejection layer via interfacial polymerization (IP). The PDA coating assisted the UiO dispersion in MPD/water media, resulting in better chemical miscibility between the UiO-PDA and PA matrix. The impact of the UiO-PDA incorporation on the physicochemical properties (surface chemical composition, hydrophilicity, morphology, and roughness) of the TFN membranes are systematically examined via different characterization techniques. Besides, the effect of UiO-PDA concentration on the overall performances (FO water flux, reverse salt flux, antifouling tendency) of the obtained UiO-PDA modified TFN-FO membranes were investigated in a cross-flow FO system. Compared with the pristine thin film composite (TFC) membrane, the modified TFN membranes presented higher selectivity, water flux, and anti-fouling tendency. Finally, the TFN-UC.2 (modified with 0.03 wt% UiO-PDA) membrane exhibited greater Cu 2+ ions removal in FO mode (feed solution in contact with PA active layer) than the control TFC membrane, arising from their improved PA rejection layer characteristics.

Acid-Resistance Enhancement of Thin-Film Composite Membrane Using Barrier Effect of Graphene Oxide Nanosheets.

In this study, the effect of graphene oxide nanosheets (GONs) embedded in a thin-film composite (TFC) polyamide (PA) membrane on the acid resistance of the membrane was investigated by comparison with the effect of oxidized single-walled carbon nanotubes (o-SWNTs). Both GONs and o-SWNTs increased the hydrophilicity of the membranes and caused the formation of ridges and clustered bumps on the surfaces, resulting in slightly improved water permeability. However, the o-SWNTs-embedded membrane did not show a difference in acid resistance depending on the concentration of embedded material, but the acid resistance of the GONs-embedded membrane increased with increasing concentration. The acid resistance of the GONs-embedded membranes appears to be mainly due to the barrier effect caused by the nanosheet shape of the GONs along with a sacrificial role of the PA layer protruded by the addition of GONs and the decrease of acid reaction sites by the hydrogen bonding between GONs and PA. When the TFC PA membrane was prepared with a high amount (300 ppm) of the GONs without considering aggregation of GONs, membrane selectivity exceeding 95% was maintained 4.7 times longer than the control TFC membrane. This study shows that the acid resistance can be enhanced by the use of GONs, which give a barrier effect to the membrane.

Mechanistic Insights into the Role of Polydopamine Interlayer toward Improved Separation Performance of Polyamide Nanofiltration Membranes.

Interlayered thin-film nanocomposite membranes (TFNi) are an emerging type of membranes with great potential to overcome the permeability-selectivity upper bound of conventional thin-film composite (TFC) nanofiltration and reverse osmosis membranes. However, the exact roles of the interlayer and the corresponding mechanisms leading to enhanced separation performance of TFNi membranes remain poorly understood. This study reports a polydopamine (PDA)-intercalated TFNi nanofiltration membrane (PA-PSF2, PDA coating time of 2 h) that possessed nearly an order of magnitude higher water permeance (14.8 ± 0.4 Lm-2 h-1 bar-1) than the control TFC membrane (PA-PFS0, 2.4 ± 0.5 Lm-2 h-1 bar-1). The TFNi membrane further showed enhanced rejection toward a wide range of inorganic salts and small organic molecules (including antibiotics and endocrine disruptors). Detailed mechanistic investigation reveals that the membrane separation performance was enhanced due to both the direct "gutter" effect of the PDA interlayer and its indirect effects resulting from enhanced polyamide formation on the PDA-coated substrate, with the "gutter" effect playing a more dominant role. This study provides a mechanistic and comprehensive framework for the future development of TFNi membranes.

High-performance nanofiltration membranes with a sandwiched layer and a surface layer for desalination and environmental pollutant removal

To overcome the permeability-selectivity limitation and improve the performance of desalination membranes, novel methods and design strategies are needed to prepare new types of thin film composite (TFC) nanofiltration (NF) membranes. In this work, a modified TFC membrane with a sandwiched layer and a surface layer was fabricated through a facile additional two-step approach. The microfiltration (MF) substrate and TFC surface were modified by a cellulose nanocrystal (CNC) sandwiched layer and a polydopamine (PDA) layer, respectively. Scanning electron microscopy (SEM) analysis indicated that the support modified by CNCs presented a more homogeneous surface than the control TFC. Cross-sectional SEM images showed that the underneath MF support, CNC interlayer, polyamide layer and PDA deposition layer were perfectly integrated. The surface charge was determined by an electrophoretic analyzer and revealed that the CNC interlayer increased the membrane electronegativity, while the PDA layer presented the opposite effect. Compared to the control TFC membrane, the solute permeability and rejection of the resultant CNC-TFC-PDA membrane were simultaneously increased, indicating a breakthrough in the trade-off limitation. The modified membranes exhibited a high removal rate for Congo red, Rose Bengal, sodium lignosulfonate and alkaline lignin, suggesting their excellent rejection performance for textile dyes and lignin derivatives. Fouling tests indicated that both the interlayer and surface layer exhibited positive effects on fouling alleviation. The effects of each functional layer were explored, and the main factors for performance improvement, including the modified hydrophilicity, surface charge, pore size and surface roughness, were discussed.

Enhancing the permeance and antifouling properties of thin-film composite nanofiltration membranes modified with hydrophilic capsaicin-mimic moieties

Enhancing the water permeance and improving the antifouling performance of developing thin film composite (TFC) nanofiltration (NF) membranes remains a great challenge for practical applications. In this work, a novel TFC membrane was fabricated by introducing a new capsaicin derivative (propyl 2-(acrylamidomethyl)-3,4,5-trihydroxybenzoate, PAMTB) into a polyamide (PA) layer during interfacial polymerization for the NF process. The abundant hydroxyl groups in the PAMTB molecules can compete with the amino group in piperazine (PIP) to react with acyl chloride in trimesoyl chloride (TMC), facilitating the formation of a smooth and hydrophilic membrane surface with an enlarged pore size to promote water permeance. Compared to the control TFC membrane, the PAMTB-incorporated membrane exhibited increased water flux from 80 L m-2h-1 to 115 L m-2h-1 and a steady rejection of above 98.0% with 2.0 g L-1 Na2SO4 as the feed solution under a pressure of 5.0 bar. Different measurement methods demonstrated that the TFC-PAMTB membrane exhibited superior antifouling properties and long-term stability. In particular, the permeation flux recovery was approximately 100% after simple hydraulic washing with HA solution as the foulant. This work introduced a new approach to exploit capsaicin-mimic moieties in water treatment applications.

Constructing substrate of low structural parameter by salt induction for high-performance TFC-FO membranes

Forward osmosis (FO) is a promising membrane-based technology for water treatment and desalination. But, internal concentration polarization (ICP), a unique phenomenon in FO, generally leads to the sharp performance decline. In this study, a novel polyacrylonitrile (PAN) substrate with low polymer concentration (4 wt%) of the thin-film composite (TFC) membrane with a low membrane structural parameter (S) is developed with sodium chloride (NaCl) aqueous solution as the coagulation bath, and exhibits high performance for FO applications. The existence of NaCl in the coagulation bath not only affects the phase inversion process significantly, resulting in the formation of a thin substrate with finely tuned morphology structure, but also benefits the formation of a uniform and defect-free top polyamide (PA) layer. Effects of NaCl content in the coagulation bath on the morphology and intrinsic properties of resulting PAN substrates, the formed PA layer, as well as the morphology and FO performance of resulting TFC membranes, are investigated systematically. Moreover, an extended study on cellulose acetate (CA) substrate is also conducted to study the universality of this salt induction method to fabricate high-performance TFC membranes. Compared to the control TFC membrane, modified TFC membranes show much lower S parameters and superior separation performance with the higher water flux (324% increment) and lower reverse salt flux (58% reduction).

Resorcinol-formaldehyde nanobowls modified thin film nanocomposite membrane with enhanced nanofiltration performance

The performance of thin film nanocomposite (TFN) membranes is substantively determined by the structure, composition and size of the incorporated nanofillers. In this work, an asymmetric organic nanofiller, resorcinol-formaldehyde nanobowls (RFB), was firstly designed via a modified Stöber approach and introduced into the polyamide selective layer of the TFN membrane via an interfacial polymerization process. Thanks to the asymmetric structure, concave cavity and chemical groups of the incorporated RFB, enhanced nanofiltration performance of the prepared TFN membrane was achieved. The optimized TFN membranes exhibited higher water fluxes and well maintained salt rejections. The water fluxes of the TFN-B0.12 membrane were 119.74 ± 4.28 for the Na2SO4 solution and 141.46 ± 5.92 L/(m2·h) for the MgCl2 solution, which are 1.5 times higher than that of the control thin film composite (TFC) membrane, with comparable rejection (95.76 ± 0.29%) for Na2SO4 and 4.63% higher (25.98 ± 0.45%) rejection for MgCl2, respectively. Meanwhile, the basic resistance of the RFB modified TFN membrane was reinforced simultaneously as compared with that of the control TFC membrane. The results demonstrate the incorporation of the RFB significantly strengthened the nanofiltration performance of the TFN membrane.

Efficient surface ionization and metallization of TFC membranes with superior separation performance, antifouling and anti-bacterial properties

Membrane-based forward osmosis (FO) technology has attracted increasing interest in the field of water treatment due to its high economical and separation efficiency. However, the availability of a FO membrane with superior separation and antifouling properties is still the critical issue for its real application in wastewater purification. In this work, novel thin-film composite (TFC) membranes are developed by surface ionization with various metal ions and subsequent metallization with the assistance of pre-grafted polyethyleneimine (PEI) and N-containing organic phosphonic acid (OPA), where the latter provides abundant and stable complexing sites. The grafting of hydrophilic PEI/OPA and the attachment of silver atoms endow the resulting membrane a dual defensive and offensive functionality associated with anti-adhesive property and antibacterial activity, respectively. Compared with the control TFC membrane, the surface-modified membranes show significantly improved anti-adhesive property against bovine serum albumin (BSA) and antibacterial property against S. aureus and E. coli bacteria, and thereby improved antifouling property towards the local lake water. Additionally, compared with the silver-metalized TFC membranes prepared by the direct method or indirect PEI binding, the silver-metalized membrane prepared by the indirect OPA binding exhibits a much higher silver loading (34.38 μg/cm2), as well as better, more stable and long-term antibacterial property. Moreover, compared with the control membrane, the modified membranes also have much higher water fluxes (87–141% increase) and comparable or even lower reverse salt fluxes. The influences of the metal ion type used for ionization and the method used for metallization are systematically investigated.

Tannic Acid/Fe3+ Nanoscaffold for Interfacial Polymerization: Toward Enhanced Nanofiltration Performance.

Conventional thin-film composite (TFC) membranes suffer from the trade-off relationship between permeability and selectivity, known as the "upper bound". In this work, we report a high performance thin-film composite membrane prepared on a tannic acid (TA)-Fe nanoscaffold (TFCn) to overcome such upper bound. Specifically, a TA-Fe nanoscaffold was first coated onto a polysulfone substrate, followed by performing an interfacial polymerization reaction between trimesoyl chloride (TMC) and piperazine (PIP). The TA-Fe nanoscaffold enhanced the uptake of amine monomers and provided a platform for their controlled release. The smaller surface pore size of the TA-Fe coated substrate further eliminated the intrusion of polyamide into the substrate pores. The resulting membrane TFCn showed a water permeability of 19.6 ± 0.5 L m2- h-1 bar-1, which was an order of magnitude higher than that of control TFC membrane (2.2 ± 0.3 L m-2 h-1 bar-1). The formation of a more order polyamide rejection layer also significantly enhanced salt rejection (e.g., NaCl, MgCl2, Na2SO4, and MgSO4) and divalent to monovalent ion selectivity (e.g., NaCl/MgSO4). Compared to conventional TFC nanofiltration membranes, the novel TFCn membrane successfully overcame the longstanding permeability and selectivity trade-off. The current work paves a new avenue for fabricating high performance TFC membranes.

Efficient surface modification of thin-film composite membranes with self-catalyzed tris(2-aminoethyl)amine for forward osmosis separation

Interfacially synthesized polyamide (PA) thin-film composite (TFC) membranes are widely employed in forward osmosis (FO) applications because of the easy fabrication and excellent separation performance. But they generally suffer from the relative low water permeability and high fouling tendency due to the inherent hydrophobic nature of the PA layer. In this study, an efficient surface modification of nascent TFC membranes is performed by grafting a self-catalyzed tripodal amine—tris(2-aminoethyl)amine (TAEA), in order to improve the membrane performance. This tertiary amine plays a dual role of the reactive amine monomer reacting with acyl chloride groups and the catalyst accelerating the amidation reaction between 1,3,5-trimesoyl chloride (TMC) and TAEA, therefore contributing to an efficient grafting effect to the greatest extent. State-of-the-art characterizations are applied to verify the modification mechanism. The effects of the pH and concentration of the TAEA solution on the overall properties of the resultant TFC membranes are systematically investigated, including the surface chemical composition, surface morphology, hydrophilicity, surface charge, separation performance, and fouling resistance. Compared with the control TFC membrane, TAEA-modified TFC membranes exhibit significantly improved water fluxes, higher antifouling propensity, and comparable reverse salt fluxes.

Decreasing ICP of forward osmosis (TFN-FO) membrane through modifying PES-Fe3O4 nanocomposite substrate

This film nanocomposite forward osmosis (TFN-FO) membrane was developed using polyethersulfone-ferrous ferric oxide (PES-Fe3O4) nanocomposite substrate. The results revealed that the porosity and the hydrophilicity of the PES substrate were improved after addition of Fe3O4 nanoparticles (NPs), leading to reducing in structural parameter (S value or S) and water flux enhancement. To fabricate TFN membranes for FO application, a thin polyamide layer was fabricated by interfacial polymerization of m-Phenylenediamine (MPD) and 1, 3, 5-trimesoylchloride (TMC) on the top surface of PES-Fe3O4 nanocomposite substrates. The TFN membrane prepared with 0.2 wt% Fe3O4 NPs showing the most reliable results by exhibiting high water flux and low reverse solute flux. Furthermore, TFN0.2 membrane exhibited significantly higher pure water flux than that of control thin film composite (TFC) membrane in both AL-FS and AL-DS orientation when 10 mM NaCl and Caspian seawater was used as feed solution and 0.5 or 2M NaCl was used as draw solution. This improvement can be attributed to the fact that the S value of TFN0.2 is much lower in comparison to control TFC membrane (0.42 vs 0.78 mm), leading to reduced internal concentration polarization (ICP) effect.

Synthesis and characterization of thin film composite membranes made of PSF-TiO2/GO nanocomposite substrate for forward osmosis applications

Support layer of thin film composite (TFC) membrane plays an important role in forward osmosis (FO) performance. A new type of support layer or nanocomposite substrate was developed by incorporating titanium dioxide (TiO2)/graphene oxide (GO) into polysulfone (PSF) matrix. Prior to performance evaluation, the developed substrates were characterized with respect to surface chemistry, roughness and cross-sectional morphology. The results showed that both surface hydrophilicity and roughness of PSF-based substrates were increased upon incorporation of nanomaterials. Substrates with long finger-like voids extended from the top to the bottom could be developed upon incorporation of TiO2 (SubstrateTiO2) or TiO2/GO mixture (SubstrateTiO2/GO). The improved surface hydrophilicity and favorable structure formed are the main factors leading to higher water flux of nanocomposite substrate. Moreover, the water flux of FO using TFC membranes could be enhanced using this nanocomposite substrate. Comparing to the control TFC membrane, the TFC membranes made of SubstrateTiO2 and SubstrateTiO2/GO exhibited greater water flux with minimum increase in reverse draw solute flux. Based on the results obtained, it can be concluded that the incorporation of TiO2 and/or GO nanoparticles into PSF substrate could potentially improve the TFC membrane performance during FO applications.