Polysulfone Support Layer Research Articles

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.

High permeability Performance TFC Nanofiltration Membrane with Two dimensional Nanochannels Support Layer Fabricated by Dissolving of Nanosheets

A synthesized thin film composite (TFC) nanofiltration membrane was prepared by incorporating Mg(OH)2 nanosheets at different ratios (from 0 to 0.5 wt%) into polysulfone (PSf) support layer. The polypiperazinamide (PPA) layer was prepared on the polysulfone support layer by means of interfacial polymerization. Then TFC membrane was then etched with H2SO4 and a PPA selective layer was established using trimesoyl chloride (TMC) and piperazine (PIP). The characterization results show that the modifications of the PSf substrate with Mg(OH)2 alter the physicochemical properties of the poly(piperazine amide) selective layer. Through the introduction of Mg(OH)2, the hydrophilicity of the TFC membrane was increased (WCA: 20.5°), promoting more linear polypiperinamide. The addition of 0.4 wt% Mg(OH)₂ to the PSf substrate, followed by sulfuric acid etching, resulted in a 196 % increase in membrane flux and with Na₂SO₄ retention at 97.72 %. The change in matrix composition favoured the generation of a lighter and rougher selective layer. The two-dimensional nanochannels in the support layer provided additional channels for water molecule transport. The membrane with two-dimensional nanochannels exhibited excellent resistance to contamination, with a flux recovery of 92.8 % for bovine serum albumin (BSA).

Construction of 1D akaganeite-templated nanochannels in polyamide forward osmosis membrane for high flux separation and nutrient enrichment

To realize nutrient (NO3–-N and PO43−-P) enrichment through FO, this study focuses on tailoring polysulfone (PSF) support layer of TFC FO membrane using 1D akaganeite (Ak) as nano-template to improve the permeance and selective separation of nutrient ions. The incorporation and the subsequent removal of the nano-template from the PSF support layer instantly created porous structures with the desired nanochannel architectures. The separation performance of the resultant e-Ak/TFC membrane is superior to other as-synthesized TFC membranes due to the presence of highly permeable channels, lower membrane tortuosity of support layer and the formation of homogenous polyamide active layer. This restricts the back-diffusion of ions in the support layer, hence improving the effective driving force across the layer. The membrane demonstrated increased water flux from 6.5 for control TFC to 14.1 L/m2∙h for e-Ak/TFC membrane (∼2.2 times higher) along with high selectivity, JW/JS of 0.58 g/L and lower S value. NO3–-N and PO43−-P were effectively enriched in the feed side due to high ion removal efficiencies by the membrane (>97 %) with water reduction of approximately 25 %. We anticipate this work offers an insight into the design of FO membrane that is capable for desalination and enrichment of nutrient in wastewater.

FO membrane fabricated by layer-by-layer interfacial polymerisation and grafted sulfonamide group for improving chlorine resistance and water permeability

This study presents a layer-by-layer interfacial polymerization approach to enhance the chlorine resistance and water permeability of thin-film composite (TFC) polyamide (PA) forward osmosis membranes. The PA film was prepared by self-polymerization using 3,5-Dihydroxybenzoic acid (DHBA) and trimesoyl chloride (TMC) with addition of 4-amino-benzene sulfonamide (4-ABSA), which is a sulfonamide monomer, on a polysulfone (PSF) support layer. The cross-linking structure and surface characterisation of the DHBA-ABSA membrane was studied systematically. FTIR results showed the successful grafting of the sulfonamide group on the membrane surface. Compared with the MPD-TMC membrane, the water flux of three modified membranes—DHBA, ABSA, and DHBA with ABSA—improved by 27.6%, 44.0%, and 67.6%, respectively, and reverse salt flux decreased by 9.9%, 12.3%, and 16.2%, respectively. Furthermore, the chlorine-stability test using 200 ppm NaClO indicated stable long-term performance under different pH values. The stable sulfonamide structure of ABSA with N-H group effectively prevented chlorine from directly attacking the active layer and improve the chlorine-stability of the membrane. In addition, the abundant hydrophilic groups on ABSA and DHBA monomers formed a hydration layer with water molecules on the membrane surface through hydrogen bonding, which enhanced the permeability of the TFC-PA membranes. The findings of this study demonstrate the DHBA-ABSA membrane's wider application potential in water and wastewater treatment processes.

Impact of Graphene Oxide on Properties and Structure of Thin-Film Composite Forward Osmosis Membranes.

Forward osmosis (FO) membranes have the advantages of low energy consumption, high water recovery rate, and low membrane pollution trend, and they have been widely studied in many fields. However, the internal concentration polarization (ICP) caused by the accumulation of solutes in the porous support layer will reduce permeation efficiency, which is currently unavoidable. In this paper, we doped Graphene oxide (GO) nanoparticles (50~150 nm) to a polyamide (PA) active layer and/or polysulfone (PSF) support layer, investigating the influence of GO on the morphology and properties of thin-film composite forward osmosis (TFC-FO) membranes. The results show that under the optimal doping amount, doping GO to the PA active layer and PSF support layer, respectively, is conducive to the formation of dense and uniform nano-scale water channels perpendicular to the membrane surface possessing a high salt rejection rate and low reverse solute flux without sacrificing high water flux. Moreover, the water channels formed by doping GO to the active layer possess preferable properties, which significantly improves the salt rejection and water permeability of the membrane, with a salt rejection rate higher than 99% and a water flux of 54.85 L·m−2·h−1 while the pure PSF-PA membrane water flux is 12.94 L·m−2·h−1. GO-doping modification is promising for improving the performance and structure of TFC-FO membranes.

Acid-resistant thin-film composite nanofiltration membrane prepared from polyamide-polyurea and the behavior of density functional theory study

Acid-resistant nanofiltration membranes consisting of amide and urea groups have enhanced acid stability. A polyamide-polyurea NF membrane was fabricated by the interfacial polymerization reaction of linear ethylenediamine with toluene-diisocyanate and trimesoyl chloride on a polysulfone (PSf) support layer. The optimized EDA 0.5 /TMC 0.05 -TDI 0.05 membrane has a MgSO 4 rejection rate of 98% and was maintained over 98% for 83 days of exposure to 15 wt% H 2 SO 4 . The EDA 0.5 /TMC 0.05 -TDI 0.05 membrane has acid resistance in an acidic solution (pH < 0), which was attributed to the stability of EDA as well as polyurea linkage having resonance, and resistance to hydrolysis due to greater hydrogen bonding. In addition, density functional theory (DFT) calculations were carried out to prove the acid-stability of the polyamide-polyurea NF membrane in terms of free energy (ΔG). The degradation of the membrane with EDA-TMC/TDI proceeds relatively slowly compared to a commercial polyamide nanofiltration membrane (PIP-TMC) due to the high energy barrier and the enhanced acid resistance of the prepared polyamide-polyurea membrane. This study introduces an NF membrane with a novel active layer with excellent performance and robust acid stability. • A novel acid-resistant NF membrane was fabricated by the interfacial polymerization. • An active layer of the novel membrane has consisted of amide and urea group. • DFT was used to prove the acid-stability of the polyamide-polyurea NF membrane. • The novel membrane exhibited excellent long-term acid stability.

Zwitterionic polysiloxane-polyamide hybrid active layer for high performance and chlorine resistant TFC desalination membranes

• Zwitterionic polysiloxane-PA hybrid active layer TMC on the PS support layer was prepared. • SPPT was synthesized by the reaction of DMAPS with 1,3-propane sulfone. • Chlorine resistance of fabricated membrane increased from 2 h to 6 h. • Salt rejection slightly increased from 98.8% to 98.9%. Hybrid polysiloxane-polyamide thin-film composite (TFC) reverse osmosis (RO) membranes were produced in the presence of a zwitterionic silane compound during polyamide active layer preparation by interfacial polymerization for an enhanced desalination performance and chlorine resistance. The zwitterionic functional silane monomer, (3-sulfopropylbetaine-propyl)-trimethoxysilane (SPPT), was added to an aqueous m-phenylenediamine (MPD) monomer solution at different concentrations; 0.05, 0.1, 0.25, 0.5 and 1.0 SPPT/MPD ratios. The aqueous monomer solutions adsorbed on a polysulfone support layer were contacted with an organic trimesoyl chloride (TMC) monomer solution to create a polysiloxane-polyamide hybrid active layer by interfacial polymerization. Hybrid active layers were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA), and zeta potential measurements. Membranes produced with a SPPT/MPD ratio of 0.1 exhibited an increase in permeate flux from 25 L m −2 h −1 to 33 L m −2 h −1 (55 bar operating pressure; 3.2% NaCl feed) while the salt rejection was not compromised, but slightly increased from 98.8% to 98.9%, when compared to the control membrane prepared without SPPT. The highest resistance against chlorine was observed for the membranes produced with a SPPT/MPD ratio of 1.0, for which, a significant membrane damage and consequent loss of salt rejection were observed after six hours of exposure to chlorine solution, while the control membrane was prone to chlorine damage after two hours.

Acid stability of polyamide membranes

This study systematically focused on the conditions for acid resistance of polyamide membranes using seven types of polyamide membranes fabricated manually via interfacial polymerization. A 15 wt% sulfuric acid solution was used as the model wastewater of the smelting process to investigate the effect of the acidic solution on the physical and chemical properties of the membranes. Successful synthesis of the polyamide layer on the polysulfone support layer was confirmed by the changes in hydrophilicity and charge of the membrane surface using a contact angle analyzer and an electrophoretic light scattering spectrophotometer, respectively. To accelerate the degradation of polyamide membranes by acid solution, the membrane samples were gradually exposed to an acidic feed solution at 25, 45, and 65 °C. According to the surface characterizations and permeation properties of polyamide membranes, each result showed a high correlation in terms of the acid stability order. Additionally, through density functional theory calculations, we found that the lower out-of-plane deformation of the N-protonated amide bond showed higher acid stability, which is consistent with previous work. Through experimental characterization and theoretical study, we demonstrated the acid-stability trend of various polyamide membranes and proposed an important condition for acid stability.

ZnO@PMMA incorporated PSf substrate for improving thin-film composite membrane performance in forward osmosis process

The performance of the existing forward osmosis membranes is mainly restricted by the internal concentration polarization (ICP) of solutes inside the substrate. In the current work, the poly (methyl methacrylate) (PMMA) grafted ZnO nanoparticle (ZnO@PMMA) was synthesized and introduced as a novel nanofiller to minimize the ICP effect within the polysulfone (PSf) support layer. It was revealed that the ZnO@PMMA nanoparticles could improve the characteristics of the PSf membrane substrate, including the porosity, hydrophilicity, pure water permeability (PWP) and morphology. The optimal support layer has a porosity of 82.4% and PWP of 186.5. The FO performance of modified membranes in terms of water flux (Jw, LMH) and reverse salt flux (Js, gMH) were thoroughly evaluated using a cross-flow system. Also, the water permeability (A, LMH.bar−1) and salt rejection (R, %) were measured by a dead-end RO setup. The obtained TFN-ZP.2 membrane (modified with 0.25 wt% of ZnO@PMMA) showed significantly improved FO water flux (up to 14.6 LMH) and water permeability (2.3 LMH/bar) which was about 2 times that of the bare TFC-FO membrane (5.9 LMH and 1.2 LMH/bar). Additionally, the structure parameter (S) was significantly alleviated (693 ± 85 μm) after the ZnO@PMMA incorporating, indicating reducing the unwanted ICP in TFN-FO membranes.

Nanofiltration membrane embedded with hydroxyapatite nanowires as interlayer towards enhanced separation performance

The triple-layered composite nanofiltration (NF) membrane consisting of thin polyamide (PA) top layer covered on polymeric porous membrane with interlayer has been popularly accepted, even commercially applied, to solve the “trade-off” issue. The nanofiltration performance was determined by the physicochemical properties of all layers. In the current work, hydroxyapatite (HAP) nanowires were adopted as a new type of interlayer material. Its superiority of ultra-hydrophilicity and electronegativity made it a container of aqueous monomers. As a result, ultra-thin and defect-free PA layer with a thickness of ~28 nm was generated owing to the low piperazine (PIP) concentration and restricted diffusion. In addition, the ultra-hydrophilic polysulfone (PSf) support layer was also helpful to reduce mass transfer resistance. The prepared PA/HAP/PSf composite membrane presented high salt aqueous solution permeation (177 L m −2 h −1 under 6 bar), excellent divalent salt rejection (98.2% for Na 2 SO 4 ) and high mono/bivalent salt selectivity (19 for NaCl/Na 2 SO 4 mixed solutions). This work proposed a useful strategy to construct highly permeable and selective NF membrane. PA/HAP/PSf triple-layered electronegative nanofiltration membrane showing high selectivity to monovalent/bivalent ions • HAP nanowires were adopted as interlayer of composite NF membrane for the first time. • The prepared PA/HAP/PSf NF membrane possessed ultra-thin and robust electronegative PA layer. • High rejection of 98.2% and salt permeation of 177 L m −2 h −1 under 6 bar for Na 2 SO 4 were achieved.

Enhancing water permeability and antifouling performance of thin–film composite membrane by tailoring the support layer

The properties of support layers are critical for the desalination performance of thin–film composite (TFC) membranes. For instance, surface characteristics of the support layers significantly impact the formed polyamide (PA) rejection layer by interfacial polymerization, thereby affecting the water transport and fouling behaviors of the TFC desalination membranes. In this work, the relationship between the support layer's properties and final separation and antifouling properties of TFC membranes was comprehensively investigated. A sulfonated polysulfone (sPSf) polymer was utilized to control the properties of the polysulfone (PSf) support layers. The sPSf modified support layer (PSf–X series) exhibited enhanced surface hydrophilicity, smaller surface pores, larger overall porosity, and higher water flux compared with the pristine PSf support layer. After interfacial polymerization on the PSf–X series support layers, the TFC–X series membranes showed enhanced hydrophilicity, smoother surfaces, enhanced water permeability and antifouling performance without major loss of NaCl rejection. Meanwhile, the forward osmosis (FO) desalination performance of TFC–X series was significantly improved due to the enhanced water permeability and reduced internal concentration polarization associated with the more porous support layer. A computational fluid dynamic model based on the finite element method was also developed to fit the forward water and reverse salt fluxes to the experimental results. The prepared TFC membrane containing sPSf in the support layer displayed improved water permeability and antifouling performance in FO applications. This work explores the relationship between the support layer properties and the separation performance of TFC membranes. It provides an effective strategy to enhance the water permeability and antifouling of TFC membranes by tailoring the support layers.

Feasibility of H2O2 cleaning for forward osmosis membrane treating landfill leachate

This study reports landfill leachate treatment by the forward osmosis (FO) process using hydrogen peroxide (H2O2) for membrane cleaning. Although chemical cleaning is an effective method for fouling control, it could compromise membrane integrity. Thus, understanding the impact of chemical cleaning on the forward osmosis membrane is essential to improving the membrane performance and lifespan. Preliminary results revealed a flux recovery of 98% in the AL-FS mode (active layer facing feed solution) and 90% in the AL-DS (draw solution faces active layer) using 30% H2O2 solution diluted to 3% by pure water. The experimental work investigated the effects of chemical cleaning on the polyamide active and polysulfone support layers since the FO membrane could operate in both orientations. Results revealed that polysulfone support layer was more sensitive to H2O2 damage than the polyamide active at a neutral pH. The extended exposure of thin-film composite (TFC) FO membrane to H2O2 was investigated, and the active layer tolerated H2O2 for 72 h, and the support layer for only 40 h. Extended operation of the TFC FO membrane in the AL-FS based on a combination of physical (hydraulic flushing with DI water) and H2O2 was reported, and chemical cleaning with H2O2 could still recover 92% of the flux.

Co-Casting Highly Selective Dual-Layer Membranes with Disordered Block Polymer Selective Layers.

Highly selective and water permeable dual-layer ultrafiltration (UF) membranes comprising a disordered poly(methyl methacrylate-stat-styrene)-block-poly(lactide) selective layer and a polysulfone (PSF) support layer were fabricated using a co-casting technique. A dilute solution of diblock polymer was spin coated onto a solvent-swollen PSF layer, rapidly heated to dry and disorder the block polymer layer, and subsequently immersed into an ice water coagulation bath to kinetically trap the disordered state in the block polymer selective layer and precipitate the support layer by nonsolvent-induced phase separation. Subsequent removal of the polylactide block generated porous membranes suitable for UF. The permeability of these dual-layer membranes was modulated by tuning the concentration of the PSF casting solution, while the size-selectivity was maintained because of the narrow pore size distribution of the self-assembled block polymer selective layer. Elimination of the thermal annealing step resulted in a dramatic increase in the water permeability without adversely impacting the size-selectivity, as the disordered nanostructure present in the concentrated casting solution was kinetically trapped upon rapid drying. The co-casting strategy outlined in this work may enable the scalable fabrication of block polymer membranes with both high permeability and high selectivity.

Preparation and characterization of TFC NF membrane with improved acid resistance behavior

In this study, we prepared the novel acid-resistant thin-film composite (TFC) piperazine(PIP)-based nanofiltration (NF) membrane using melamine (Mel), sulfonated-melamine formaldehyde (SMF), and sulfanilamide (SA) through interfacial polymerization on a polysulfone (PSf) support layer. A long-term acid-resistant experiment for divalent salt was carried out with static immersion tests in a 15 wt% sulfuric acid solution. The divalent rejection of the PIP1-SMF0.3-SA0.05 in a 15 wt% sulfuric acid solution was maintained at over 96% after 10 days, and then slightly decreased to 94% for 20 days, and finally was maintained over 90% for 30 days. The flux was maintained at about 20 GFD even after 30 days of immersion in acid. In order to confirm the degree of hydrolysis in amide, the bond dissociation energy (BDE) was calculated using the density functional theory (DFT). BDE values of PIP-TMC, Mel-TMC, and SA-TMC were 79.34, 83.78, and 93.91 kcal/mol. Consequently, PIP1-SMF0.3-SA0.05 having s-triazine and sulfonyl amide group exhibited acid-stable performance because the C–N bond is more stable and the slow hydrolysis reaction in acid. Our research for preparing high perm-selectivity and long-term acid stability membrane can extend NF technology in many industries, particularly in the recovery of rare metals from acidic solutions.

Enhancing the performance of TFC nanofiltration membranes by adding organic acids in polysulfone support layer

Throughout this study, the effect of certain organic acids, methacrylic acid, lactic acid and tartaric acid, doped in polysulfone (PSF) casting solution onto the performance of nanofiltration (NF) membranes was investigated. Different NF membranes have been prepared from m-phenylenediamine and trimesoylchloride onto the top surface of the acid-modified PSF membranes through regulating the concentration and contact time of the conventional interfacial polymerization process. The study of scanning electron microscopy (SEM) was used to investigate the influence of acids on the morphology of membranes and cross-sectional structures. The functional groups, hydroxyl and carboxylic acid, of the acids have resulted in a significant increase in membrane thickness, porosity and hydrophilicity, with a decrease in macrovoid capacity of the PSF layer. The acid-modified PSF/TFC membranes showed higher rejection of salt, with an increment in water flux compared to the neat membrane. Water flux and salt rejection (Rs %) of the control membrane was 7.6 L/m2 h and 65.4%, whereas polysulfone/methacrylic acid (PSF/MAAc), polysulfone/tartaric acid (PSF/TAc), and polysulfone/lactic acid (PSF/LAc) were 16.8, 18.5, and 20.2 L/m2 h and 88, 88.2 and 94.1%, respectively. Efficiency of prepared NF membranes under various inlet pressures and specific salts was investigated with selectivity and salt rejection. The salt rejection of a mixed salt solution was found to meet the order of Rs % CaSO4 ≥ Rs % Na2SO4 ˃ Rs % MgSO4 ˃ Rs MgCl2 ˃ Rs % NaCl.

Characterization and analysis of inorganic foulants in RO membranes for groundwater treatment

Thousands of small community-based RO plants have been installed in Rajasthan in the last few years by Public Health Engineering Department in compliance with the national guidelines. Recent reports from plant managers have indicated substantial premature replacement of RO membrane modules due to accelerated fouling. This paper describes the performance analysis of community RO plants in Bharatpur having high total dissolved solids in groundwater and attempts an ion balance to understand the fouling problem through chemical analysis of raw, permeate and reject water samples. The analysis gives new insights to field operations of brackish water systems indicating that in the majority of these plants, CaCO3 was the main foulant as per SEM-EDS; attributed to high hardness, relatively lesser solubility of hardness causing substances over sodium chloride, and inverse solubility-temperature behavior of CaCO3; water temperature being higher in Rajasthan compared to that of coastal areas. Oxides of Fe and Mn were other major foulants as they are sparingly soluble in water; thus precipitate immediately and foul the membrane. Cleaning efficiencies of HCl and citric acid were also investigated. An optimum time of 9 h cleaning through citric acid was found best while use of HCl resulted in damaging polysulfone support layer.

Morphology of Thin Film Composite Membranes Explored by Small-Angle Neutron Scattering and Positron-Annihilation Lifetime Spectroscopy.

The morphology of thin film composite (TFC) membranes used in reverse osmosis (RO) and nanofiltration (NF) water treatment was explored with small-angle neutron scattering (SANS) and positron-annihilation lifetime spectroscopy (PALS). The combination of both methods allowed the characterization of the bulk porous structure from a few Å to µm in radius. PALS shows pores of ~4.5 Å average radius in a surface layer of about 4 μm thickness, which become ~40% smaller at the free surface of the membranes. This observation may correlate with the glass state of the involved polymer. Pores of similar size appear in SANS as closely packed pores of ~6 Å radius distributed with an average distance of ~30 Å. The main effort of SANS was the characterization of the morphology of the porous polysulfone support layer as well as the fibers of the nonwoven fabric layer. Contrast variation using the media H2O/D2O and supercritical CO2 and CD4 identified the polymers of the support layers as well as internal heterogeneities.

Effect of TiO2 content on the properties of polysulfone nanofiltration membranes modified with a layer of TiO2–graphene oxide

Graphene oxide (GO)-based membranes have been widely used for molecular separation due to their size exclusion effect. However, it remains a challenge to prepare a structurally stable, freestanding GO-based membrane that exhibits efficient separation. Herein, GO nanofiltration (NF) membranes with different loadings of TiO2 (TiO2@GO) were successfully prepared on top of a polysulfone (PSF) support layer and showed high efficiency in dye separation/desalination, along with antifouling and antibacterial activity. The resulting TiO2@GO NF membranes also showed excellent structural stability. The membrane prepared with the same contents of GO and TiO2 (NFG-2) exhibited high dye rejection (>98%) and low Na2SO4 rejection (<6%) and thus could be applied in the treatment of dye wastewater. Moreover, its permeation flux (3.6 L·m−2·h−1·bar−1) and dye rejection (98.0%) remained constant at high levels after 9 h of operation. Antifouling and antibacterial properties were also observed. This new kind of NF membrane may be a promising candidate for use in dye separation and desalination applications.

Water transport properties of boron nitride nanosheets incorporated thin film nanocomposite membrane for salt removal

This work has focused on the fabrication of thin film composite (TFC) and thin film nanocomposite (TFN) membranes for reverse osmosis (RO) application. Raw boron nitride (BN) and chemically activated boron nitride (A-BN) were used as nanofillers in polysulfone support layer and trimesoyl chloride (TMC) to improve the membrane performance. Different concentrations of BN and A-BN (ranging from 0 to 1 wt %) were added to the polysulfone (PSf) microporous support and polyamide layer was formed on top of PSf support through interfacial polymerization of 1,3-Phenylendiamine and trimesoyl chloride. The fabricated TFN membranes were characterized in terms of membranes structure, contact angle, separation properties, as well as RO performance. According to AFM and SEM images, TFN membranes showed larger average pore size and higher surface roughness as compared with TFC membrane. Thus, TFN membrane showed higher pure water flux but lower NaCl rejection. The addition of BN led to increase in pore size of membrane without increase the selectivity of membrane. The addition of both BN and A-BN into polyamide layer does not aid to improve the properties of membrane. In conclusion, BN nanoparticles showed the potential to be used as nanofillers that aid in formation of larger pore size.

Facile integration of halloysite nanotubes with bioadhesive as highly permeable interlayer in forward osmosis membranes

In this study, new type of thin film nanocomposite (TFN) membrane with polysulfone (PSf) support layer having highly permeable interlayer using halloysite nanotubes (HNT) and hydrophilic polydopamine (pDA) was fabricated to improve the surface wettability of the PSf support layer, and to play a positive role in the development of a PA active layer. ATR-FTIR and XPS analysis confirmed the presence of the pDA/HNTx interlayer on the PSf support layer. Contact angle measurements confirmed that the surface wettability of support layer for TFN FO membrane was enhanced with increasing HNT loading. It was revealed that a pDA/HNT nanocomposite interlayer has considerable potential for enhancing the performance of TFN FO membranes. A TFN membrane with a pDA/HNT interlayer showed outstanding FO performance, due to its superior water flux of 26.9 L/m2 h (FO mode, 1 M NaCl draw solution), without a significant increase in reverse salt flux. This was attributed to the superior hydrophilicity and permeability of the interlayer, as well as the formation of a selective PA layer on the interlayer.