Thin-film Composite Forward Osmosis Membranes Research Articles

Incorporation of zeolitic imidazolate framework-8 (ZIF-8) in the polyamide and polysulfone layers of forward osmosis membranes for enhancing aquaculture wastewater recovery and PPCPs removal

Wastewater recovery is essential to alleviate water resource shortages, and this can be achieved through a high-energy-efficient forward osmosis (FO) process combined with an emerging material, zeolitic imidazolate framework-8 (ZIF-8). Here, we create thin-film composite FO membranes (TF-CFOMs) by incorporating ZIF-8 into the active polyamide (PA) and/or support polysulfone (PSf) layers to address the challenges of low water flux and loss of draw solutes during operation. Experimental factors included the dosage of ZIF-8 nanoparticles in PA preparation solutions and the dosages of 2-methylimidazole (2-Hmim) and zinc nitrate hexahydrate (ZNH) in n-methyl-2-pyrrolidone (NMP) to fabricate the PSf casting solutions with in-situ formed ZIF-8 nanoparticles. Successful ZIF-8 incorporation on the TF-CFOM surface was confirmed, and the ZIF-8 TF-CFOMs exhibited increased surface hydrophilicity and separation performance. Only modifying the PA layer by adding 0.025 wt% ZIF-8 nanoparticles in trimesoyl chloride (TMC) resulted in the membrane (PA0.025T-PSf0) with water flux 2.3 times higher than the pristine TF-CFOM (4.9 LMH). The pristine and modified TF-CFOMs were further applied for aquaculture wastewater (AWW) recovery and removal of pharmaceuticals and personal care products (PPCPs). Results of water recovery demonstrated that the recovery rate reached 89.1% in 3.5 days when using the dual-layer modified TF-CFOM. Results of PPCP removal indicated that both pristine and modified TF-CFOMs can achieve high PPCP rejection efficiency (>90%), with the modified TF-CFOM (PA0.025T-PSf2.0) performing the best. Overall, the PA0.025T-PSf2.0 TF-CFOM achieved high and stable separation efficiency in long-duration AWW recovery, making it well-suited for practical field applications.

Viability of Total Ammoniacal Nitrogen Recovery Using a Polymeric Thin-Film Composite Forward Osmosis Membrane: Determination of Ammonia Permeability Coefficient.

Total ammoniacal nitrogen (TAN) occurs in various wastewaters and its recovery is vital for environmental reasons. Forward osmosis (FO), an energy-efficient technology, extracts water from a feed solution (FS) and into a draw solution (DS). Asymmetric FO membranes consist of an active layer and a support layer, leading to internal concentration polarization (ICP). In this study, we assessed TAN recovery using a polymeric thin-film composite FO membrane by determining the permeability coefficients of NH4+ and NH3. Calculations employed the solution-diffusion model, Nernst-Planck equation, and film theory, applying the acid-base equilibrium for bulk concentration corrections. Initially, model parameters were estimated using sodium salt solutions as the DS and deionized water as the FS. The NH4+ permeability coefficient was 0.45 µm/s for NH4Cl and 0.013 µm/s for (NH4)2SO4 at pH < 7. Meanwhile, the NH3 permeability coefficient was 6.18 µm/s at pH > 9 for both ammonium salts. Polymeric FO membranes can simultaneously recover ammonia and water, achieving 15% and 35% recovery at pH 11.5, respectively.

Design and preparation of woven fabric-reinforced substrate: A new pathway for robust thin film composite membrane

The thin film composite (TFC) membrane possesses the highest commercial application potential among all types of forward osmosis (FO) membranes. The support layer of the membrane plays a crucial role in both bearing mechanical loads and facilitating the active layer formation. Herein, we addressed the issues of low permeability and poor mechanical strength of the conventional TFC FO membrane by selecting suitable fabrics and optimizing membrane design and preparation. Polyester (PS) woven fabric, with its high strength, low thickness, and high porosity, served as an excellent material for reinforcing the strength of the FO membrane. We employed a novel double-blade casting method to address the defect issue associated with the conventional single-blade casting method. The influencing factors and quality control strategies of the fabric-reinforced substrate were systematically investigated. Furthermore, membrane characterization techniques, including scanning electron microscopy (SEM), liquid-liquid displacement porometer, and cross-flow FO system, were used to reveal the influences of different substrates, including polysulfone (PSU), polyacrylonitrile (PAN), and polyetherimide (PEI), on the structure and performance of the fabric-reinforced TFC-FO membrane. Compared to commercial FO membranes, the TFC/PSU membrane exhibited superior FO performance, with a water flux of 24.1 LMH, and outstanding mechanical strength that was more than 10-times higher than that of free-standing membranes. This study demonstrates a new pathway for engineering robust TFC-FO membranes with low structural parameters as well as excellent scalability of the membrane fabrication method.

Optimized preparation route for polyamide top-coated forward osmosis membrane for enhanced water flux using industrial wastewater as feed.

The forward osmosis (FO) process has recently gained significant interest in treating wastewater, brackish/seawater and concentrating feedstocks for various operations, including desalination. The study investigates the effect of different synthesis conditions of the polyamide-based thin-film composite (TFC) FO membranes on the membranes' final performance. Taguchi statistical analyses were used to fabricate and optimize the polyamide TFC FO membrane. The process parameters as factors were the amount of polyethersulfone (PES), polyethylene glycol 400 (PEG-400), polyvinyl pyrrolidone (PVP), m-phenylenediamine (MPD), and trimesoyl chloride (TMC), and TMC reaction-time (RT). The Taguchi method was adopted to investigate the optimal conditions and the significance of individual factors using an L16 (45) orthogonal array. Another Taguchi analysis (Taguchi 2) was adopted to investigate the influence of other important parameters like optimal conditions for MPD, TMC, and TMC reaction-time factors using an L9 (33) orthogonal array. Confirmation tests validated a maximum water flux of 46.4 ± 2.32 L/m2·h with a specific combination of control factors for membrane synthesis: PES/PEG/PVP/MPD/TMC/TMC RT-16/7/0.5/1/0.05/30. These tests demonstrated a high-water flux of 7.05 ± 0.35 L/m2·h when exposed to industrial wastewater (secondary effluent) as the feed solution (FS) and fertilizer as the draw solution (DS) in the FO process. The R2 values were more than 90%. The experimental validation confirmed the models' predictive ability with different FSs, including industrial wastewater.

Synthesis of sandwich structure forward osmosis membrane with calcium-carboxyl modified polyamide and tannic acid-Fe3+ interlayer and its application in coconut water concentration

In this study, a sandwich structure thin-film composite forward osmosis (TFC-FO) membrane based on calcium-carboxyl interfacial polymerization was synthesized using tannic acid-Fe (TA-Fe) as the interlayer. Additionally, the concentration effect of Ca2+ surface modification, TA-Fe intermediate layers, and their combination on coconut water concentration, membrane efficiency, anti-fouling ability, and quality of the concentrate was investigated. Compared to the TFC-Ca or TFC-TA-Fe membrane, the TFC-TA-Fe-Ca membrane significantly enhanced the concentration effect and reverse salt flux (p < 0.05) and exerted the lowest attenuation of permeability. Furthermore, the total soluble solids content increased from 5.13 °Brix to 13.17 °Brix after 8 h. The TFC-TA-Fe-Ca membrane showed a 61.20 % increase in its efficiency compared to the TFC membrane. The total reducing sugar, acids, and polyphenol contents increased by 1.72, 1.34, and 1.22 times, respectively. Overall, the sandwich structure FO membrane exhibited significant feasibility and potential for industrial application in fruit juice concentrate production.

Controlling amine monomers via UiO-66-NH2 defect sites to enhance forward osmosis membrane performance for lithium recovery

The excessive thickness of the separation layer and the presence of cracks cause low water flux and poor lithium recovery in conventional forward osmosis (FO) membranes. According to the influence of the diffusion behavior of amine monomers in interfacial polymerization, the use of an interlayer optimizes the separation layer structure of traditional thin-film composite FO membrane. However, it is difficult to accurately control the separation layer structure by simply adjusting the amount of the interlayer material loaded. Herein, FO membranes with defect-containing metal–organic framework (MOF) interlayers were constructed. By adjusting the concentrations of competitive ligands, the MOFs showed different degrees of linker loss, which exposed the metal ions in the MOFs to different extents. The defective sites of the constructed MOFs increased the interaction between the interlayer and m-phenylenediamine (MPD), and density functional theory (DFT) simulations also revealed an increase in the binding energy of the two materials. Therefore, MPD attachment and diffusion were controlled by changing the proportion of defects in the MOFs, thereby finely regulating the separation layer structure. Additionally, tannic acid (TA) was predeposited to improve the stability of the interlayer. The prepared membrane exhibited water fluxes of 33.84 and 65.81 LMH and reverse salt fluxes of 0.58 and 2.38 gMH in the active layer facing feed solution (AL-FS) and active layer facing draw solution (AL-DS) modes, respectively. Excellent lithium ion recovery and fouling resistance was also demonstrated in battery wastewater treatment.

Resilient forward osmosis membranes against microplastics fouling enhanced by MWCNTs/UiO-66-NH2 hybrid nanoparticles

The escalating presence of microplastics (MPs) in wastewater necessitates the investigation of effective tertiary treatment process. Forward osmosis (FO) emerges as an effective non-pressurized membrane process, however, for the effective implementation of FO systems, the development of fouling-resistance FO membranes with high-performance is essential. This study focuses on the integration of MWCNT/UiO-66-NH2 as metal-organic frameworks (MOFs) and multi-wall carbon nanotubes (MWCNT) nanocomposites in thin film composite (TFC) FO membranes, harnessing the synergistic power of hybrid nanoparticles in FO membranes. The results showed that the addition of MWCNT/UiO-66-NH2 in the aqueous phase during polyamide formation changed the polyamide surface structure, and enhanced membranes’ hydrophilicity by 44%. The water flux of the modified FO membrane incorporated with 0.1 wt% MWCNTs/UiO-66-NH2 increased by 67% and the reverse salt flux decreased by 22% as in comparison with the control membrane. Moreover, the modified membrane showed improved antifouling behavior against both organic foulant and MPs. The MWCNT/UiO-66-NH2 membrane experienced 35% flux decline while the control membrane experienced 65% flux decline. This proves that the integration of MWCNT/UiO-66-NH2 nanoparticles into TFC FO membranes is a viable approach in creating advanced FO membranes with high antifouling propensity with potential to be expanded further to other membrane applications.

Electric field forward osmosis (EFFO) fouling mitigation in algae harvesting

Efficient microalgae harvesting is crucial for sustainable biofuel production. Forward osmosis (FO) membranes offer a cost-effective solution for algae separation but are prone to membrane fouling. To address this, a bench-scale FO membrane unit was created, utilizing an aquaporin thin film composite FO membrane. The unit was combined with an electric field in both continuous and pulsing modes, employing stainless steel (SS) meshes to mitigate fouling during Chlorella vulgaris dewatering. Generally, applying higher electric potentials in continuous mode demonstrated improved water flux and flux recovery. The electric field forward osmosis (EFFO) configuration achieved significantly higher fluxes at applied potentials of −0.1, −0.4, and −1.0 V compared to the control. An electric potential as high as −10 V effectively removed fouling by inducing H2 gas formation on the SS cathode. Additionally, the application of high electric potential led to increased settling velocity, possibly due to electrocoagulation and the release of metals. Conversely, carbon fiber electrodes had no impact on algal cell morphology. Both higher salinity levels and increased potential enhanced lipid contents in algal biomass. Overall, EFFO technology in algae harvesting offers improved efficiency by reducing membrane fouling and increasing water flux, enabling cost-effective and sustainable biofuel production from microalgae.

A novel antifouling polyamide thin-film composite forward osmosis membrane fabricated by poly(m-phenylene isophthalamide) for seawater desalination

Forward osmosis (FO) technology has attracted the interest of many researchers due to its excellent properties such as low energy consumption, fouling resistance, and easy cleaning. However, the lack of high-performance membrane materials makes it far from being practical on a large scale application. In this study, the poly(m-phenylene isophthalamide) (PMIA) was used as the substrate to be embedded in a high-porosity polyester mesh to form a support layer, and a forward osmosis composite membrane was prepared through an interfacial polymerization process. The effects of preparation conditions such as mesh size, scraping membrane thickness, and casting solution concentration on performance were studied. In the FO operation mode, with DI water as the feed solution and 1 mol/L NaCl as the draw solution, the water flux is 8.62 L•m−2•h−1, the reverse salt flux is 0.118 mol•m−2•h−1, and the rejection for NaCl exceeds 99%. Moreover, the membrane behaved excellent mechanical properties, with a tensile strength of 95 MPa. Compared with the two commercial FO membranes, the self-made PMIA TFC-FO showed excellent hydrophilicity and fouling resistance. This research demonstrated that PMIA is a proper candidate for fabricating of the TFC-FO membranes to achieve high water flux and selectivity in seawater desalination.

Modification of polyacrylonitrile TFC-FO membrane by biowaste-derived hydrophilic N-doped carbon quantum dots for enhanced water desalination performance

Effective membranes are critical for enhancing the productivity of the forward osmosis (FO) desalination process. In this work, a straightforward approach is presented for constructing a hydrophilic and high-flux thin film composite FO (TFC-FO) membrane onto a polyacrylonitrile (PAN) sublayer. To this purpose, biowaste-derived nitrogen-doped carbon quantum dots (BWD-NCQDs) were incorporated into the polymeric structure of the TFC selective layer, which improved surface hydrophilicity and caused the creation of more water channels, resulting in better intrinsic transport properties. In both FO and pressure retarded osmosis (PRO) membrane orientations, TFC-FO membranes containing 0.01–0.1 wt% of BWD-NCQDs showed better water permeation and NaCl rejection than the pristine TFC membrane. In the presence of 0.05 wt% of BWD-NCQDs, water flux increased by 54.7 % and reached 24.6 Lm−2 h−1, and reverse solute flux decreased by 43.3 % to 3.81 g−2 h−1 compared to the pristine membrane. The optimum membrane also showed better fouling and water desalination behavior. Therefore, modification of the membranes by hydrophilic BWD-NCQDs represents superior performance in the FO processes. This study demonstrates the potential of using hydrophilic NCQDs derived from biowaste materials to incorporate into TFC membranes and improve their FO proficiency in water desalination.

Harnessing the power of metal-organic frameworks to develop microplastic fouling resistant forward osmosis membranes

With the gradual increase of microplastics (MPs) in water and wastewater streams, it is imperative to investigate their removal using tertiary treatment systems to minimize and preferably prevent their entrance into aquatic environments. Forward osmosis (FO) is a non-pressurized membrane process with potential applications in MPs removal from wastewater. However, efficient application of FO systems relies on developing high-performance FO membranes with low fouling tendency. MPs are proven as emerging foulants in membrane systems, diminishing their performance and lifetime and this highlights the need to consider MP fouling in developing sustainable membranes. The current study focuses on a novel modification of thin film composite (TFC) FO membranes by MIL-53(Fe) as a water-stable and hydrophilic metal-organic framework. Experimental results demonstrated that the optimized FO membrane (0.2 wt% MIL-53(Fe)) achieved a significantly higher water flux (90% increase) with a 23% less reverse salt flux. The modified membrane also had significantly less flux decline in fouling experiments and higher flux recovery after physical cleaning compared to the control membrane affirming its higher antifouling efficiency. MIL-53(Fe) integration in the FO substrate proved to be a practical method for developing high-performance TFC FO membranes with improved antifouling properties against MPs and organic foulants.

Date Palm Tree Leaf-Derived Cellulose Nanocrystal Incorporated Thin-Film Composite forward Osmosis Membranes for Produced Water Treatment.

Worldwide water shortage and significant issues related to treatment of wastewater streams, mainly the water obtained during the recovery of oil and gas operations called produced water (PW), has enabled forward osmosis (FO) to progress and become advanced enough to effectively treat as well as retrieve water in order to be productively reused. Because of their exceptional permeability qualities, thin-film composite (TFC) membranes have gained increasing interest for use in FO separation processes. This research focused on developing a high water flux and less oil flux TFC membrane by incorporating sustainably developed cellulose nanocrystal (CNC) onto the polyamide (PA) layer of the TFC membrane. CNCs are prepared from date palm leaves and different characterization studies verified the definite formations of CNCs and the effective integration of CNCs in the PA layer. From the FO experiments, it was confirmed that that the membrane with 0.05 wt% of CNCs in the TFC membrane (TFN-5) showed better FO performance in PW treatment. Pristine TFC and TFN-5 membrane exhibited 96.2% and 99.0% of salt rejection and 90.5% and 97.45% of oil rejection. Further, TFC and TFN-5 demonstrated 0.46 and 1.61 LMHB pure water permeability and 0.41 and 1.42 LHM salt permeability, respectively. Thus, the developed membrane can help in overcoming the current challenges associated with TFC FO membranes for PW treatment processes.

Mechanism for regulation of a forward osmosis membrane by the SA/UiO-66-NH2 composite interlayer and the resulting lithium ion concentration performance

The traditional thin-film composite (TFC) forward osmosis (FO) membrane has problems such as poor water permeability and low lithium concentration selectivity because the separation layer is too thick and has many defect pores. In this study, a thin and dense separation layer was obtained by constructing a sodium alginate (SA)/UiO-66-NH2 interlayer to control the attachment amount and diffusion rate of m-phenylenediamine (MPD), which enhanced the performance of the membrane. This paper studies the effect and mechanism of the interlayer on the structure and separation performance of the FO membrane, and explores the lithium ion concentration performance of the interlayer membrane. According to the results, based on the strong interaction between the interlayer and MPD, the equilibrium concentration of MPD available for interfacial polymerization was increased and the diffusion rate of MPD was slowed, resulting in the generation of a thin and dense separation layer. Since the interlayer restricted the escape of bubbles formed in the interfacial polymerization, the separation layer showed a leaf-like structure with increased filtration area and water storage space. Due to the reduced thickness of the separation layer and its leaf-like structures, the water flux increased significantly, and the water flux of the interlayer membrane was 47.9% greater than that of the original membrane. Drawing upon the heightened density of the separation layer and secondary separation of the interlayer, the reverse solute flux was lowered by 37.4%. The interlayer membrane exhibited efficient Li+ rejection (R>93%) and the concentration ratio of Li+ was close to its theoretical concentration ratio at 1.46 ± 0.03.

Fabrication of novel thin-film composite membrane based on ultrathin metal-organic framework interlayer for enhancing forward osmosis performance

To improve operation efficiency, an interlayered thin-film composite forward osmosis (iTFC-FO) membrane was designed by introducing an ultrathin and porous interlayer based on aluminum tetra-(4-carboxyphenyl)porphyrin (a stable metal−organic framework nanosheet, Al-MOF). Surface characterization results revealed that Al-MOF spread evenly in the macro-porous substrate, and provided a flat and smooth reaction interface with moderate hydrophilicity and uniform small aperture. The resultant polyamide (PA) layer had a thin base (without intrusion into substrate) and crumpled surface (with abundant leaves). The leaves size and cross-linking degree of PA layer firstly increased and then decreased with the Al-MOF loading. Compared to the original membrane, the iTFC-FO showed an enhanced water permeability and a reduced reverse sodium flux in both modes of active layer facing feed solution (AL-FS) and active layer facing draw solution (AL-DS). To be specific, the specific reverse sodium flux (reverse sodium flux/pure water flux) decreased from 0.27 g/L to 0.04 g/L in the AL-FS mode, while from 1.36 g/L to 0.23 g/L in the AL-DS mode with 2 mol/L NaCl as DS. Moreover, the iTFC-FO maintained high stability and high permeability under high-salinity and contaminated environment. This study offers a new possibility for the rational fabrication of high-performance TFC-FO membranes.

Recovery of cleaning agents from clean-in-place (CIP) wastewater using nanofiltration (NF) and forward osmosis (FO)

This study proposed a Nanofiltration (NF) – Forward Osmosis (FO) membrane system to recover the cleaning agents from model dairy CIP wastewater. The NF steps consist of 4 kDa and 200 Da Nanofiltration (NF) membrane to reduce the lactose and whey protein before the forward osmosis (FO) concentration step. It was found that a series of NF filtration (4 kDa-200 Da) eliminated the lactose under detection level and protein by 96.3 %. The permeates from 4 kDa or 200 Da NF were further treated with FO. Two different FO membranes, cellulose triacetate (CTA) and thin-film composite (TFC). The increase of salts concentration from 0.5 M to 2.0 M increased the water flux from 17.8 LHM to 31.7 LHM when the TFC membrane was used. 4 times increase in the salts concentration did not result in the same magnitude increase in the water flux due to concentration polarization.. In addition, the TFC membrane was found to show an enhanced level of water flux compared to the CTA membrane over the same draw solution concentration due to improved water permeability. The TFC membrane with 2 M of NaCl was selected for further concentrating the NF permeates. Concentration using TFC FO membranes resulted in an increase the active alkali between 0.5% - 0.6%. The cleaning effectiveness of the recovered cleaning agents was assessed using Quartz Crystal Microbalance with Dissipation (QCM-D). The cleaning agents recovered by 4 kDa/200 Da NF and FO were found to present no significant difference as compared to fresh cleaning agents.

Integration of nitrogen-doped carbon dots onto active layer of forward osmosis membrane for highly efficient antibacteria and enhanced membrane performances

Biofouling severely hampered the development of thin-film composite (TFC) forward osmosis (FO) membrane. Herein, novel nitrogen-doped carbon dots (N-C-dots) with fluorescence and long-lived afterglow dual-emission were fabricated using Na2EDTA and urea as co-precursors. The N-C-dots aqueous solution can synchronously produce superoxide anion radical (O2-ˑ) and singlet oxygen (1O2) under light irradiation, exhibiting immense nanoenzyme activities. The membranes (PEI-M and N-C-dots/PEI-M) were prepared by grafting PEI and N-C-dots/polyethyleneimine nanocomposites (N-C-dots/PEI) onto the active layer of pristine TFC FO membrane (Control-M), respectively. The N-C-dots/PEI-M exhibited much better hydrophilicity and smoothness than Control-M and PEI-M, resulting in a higher water permeability. Most significantly, N-C-dots/PEI-M possessed a unique dual-mode biofouling resistance, which responded to the potentials of N-C-dots as oxidase mimic and photosensitizer. In dynamic sewage treatment test, N-C-dots/PEI-M displayed much lower reduction in water flux and much better anti-biofouling behavior. Results above demonstrated that the modification strategy with N-C-dots/PEI is highly effective, pioneering a new horizon for the highly efficient inhibition of biofilm growth and biofouling development under visible light.

Calcium Alginate Production through Forward Osmosis with Reverse Solute Diffusion and Mechanism Analysis

Calcium alginate (Ca-Alg) is a novel target product for recovering alginate from aerobic granular sludge. A novel Ca-Alg production method was proposed herein where Ca-Alg was formed in a sodium alginate (SA) feed solution (FS) and concentrated via forward osmosis (FO) with Ca2+ reverse osmosis using a draw solution of CaCl2. An abnormal reverse solute diffusion was observed, with the average reverse solute flux (RSF) decreasing with increasing CaCl2 concentrations, while the average RSF increased with increasing alginate concentrations. The RSF of Ca2+ in FS decreased continuously as the FO progressed, using 1.0 g/L SA as the FS, while it increased initially and later decreased using 2.0 and 3.0 g/L SA as the FS. These results were attributed to the Ca-Alg recovery production (CARP) formed on the FO membrane surface on the feed side, and the percentage of Ca2+ in CARP to total Ca2+ reverse osmosis reached 36.28%. Scanning electron microscopy and energy dispersive spectroscopy also verified CARP existence and its Ca2+ content. The thin film composite FO membrane with a supporting polysulfone electrospinning nanofiber membrane layer showed high water flux and RSF of Ca2+, which was proposed as a novel FO membrane for Ca-Alg production via the FO process with Ca2+ reverse diffusion. Four mechanisms including molecular sieve role, electrification of colloids, osmotic pressure of ions in CARP, and FO membrane structure were proposed to control the Ca-Alg production. Thus, the results provide further insights into Ca-Alg production via FO along with Ca2+ reverse osmosis.

Fabrication of highly permeable thin-film composite forward osmosis membrane using poly-l-lysine as an additive in polysulfone substrate

Forward osmosis (FO) has received considerable interest for water and energy-related applications in recent years. However, FO has not been commercialized yet because of a few reasons. The lack of a high-performance FO membrane is one of the important barriers. To overcome this issue, a novel high-performance thin-film composite (TFC) membrane was successfully fabricated via interfacial polymerization with poly-L-lysine incorporated polysulfone substrate (PSf). Compared to the pristine PSf substrate, the incorporation of lysine (ranging 1 – 15 wt.%) meaningfully alternates the substrates chemical structure, porosity, contact angle, and morphology leading to an enhancement of the lysine -TFC membranes performance. The results showed that the new substrates with higher porosity, more hydrophilic, and smaller in pore size after the introduction of L-lysine. The membrane achieved the highest FO water flux at 15% concentration of lysine and the maximum FO water flux was 35 L/m2.h (LMH) with a comparable specific salt flux (Js/Jw) of 0.002 g/L in the active layer facing the feed side (AL-FS) when 1M NaCl was applied as draw solution. The water flux was increased with increasing concentration of lysine. The addition of poly-L-Lysine in casting solution resulted in a more porous and hydrophilic support layer.

Enhancing the Permeability and Fouling Resistance of Thin-Film Composite Forward Osmosis Membranes via Poly(ethylene glycol) Diamine as a Comonomer

Enhancing the Permeability and Fouling Resistance of Thin-Film Composite Forward Osmosis Membranes via Poly(ethylene glycol) Diamine as a Comonomer

Graphene Quantum Dot-Added Thin-Film Composite Membrane with Advanced Nanofibrous Support for Forward Osmosis.

Forward osmosis (FO) technology for desalination has been extensively studied due to its immense benefits over conventionally used reverse osmosis. However, there are some challenges in this process such as a high reverse solute flux (RSF), low water flux, and poor chlorine resistance that must be properly addressed. These challenges in the FO process can be resolved through proper membrane design. This study describes the fabrication of thin-film composite (TFC) membranes with polyethersulfone solution blown-spun (SBS) nanofiber support and an incorporated selective layer of graphene quantum dots (GQDs). This is the first study to sustainably develop GQDs from banyan tree leaves for water treatment and to examine the chlorine resistance of a TFC FO membrane with SBS nanofiber support. Successful GQD formation was confirmed with different characterizations. The performance of the GQD-TFC-FO membrane was studied in terms of flux, long-term stability, and chlorine resistance. It was observed that the membrane with 0.05 wt.% of B-GQDs exhibited increased surface smoothness, hydrophilicity, water flux, salt rejection, and chlorine resistance, along with a low RSF and reduced solute flux compared with that of neat TFC membranes. The improvement can be attributed to the presence of GQDs in the polyamide layer and the utilization of SBS nanofibrous support in the TFC membrane. A simulation study was also carried out to validate the experimental data. The developed membrane has great potential in desalination and water treatment applications.