Thin-film Composite Forward Osmosis Membranes Research Articles

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.

Photocatalytic thin film composite forward osmosis membrane for mitigating organic fouling in active layer facing draw solution mode

As a high-flux operation mode of thin film composite-forward osmosis (TFC-FO) membrane, active layer facing draw solution (AL-DS) mode suffers from the severe membrane fouling tendency, which is not addressed well. Here, we introduced a photocatalyst (Anatase titanium dioxide, A-TiO2) onto the support layer of TFC-FO membrane via the bonding of polydopamine (PDA) and polytetrafluoroethylene (PTFE), and prepared two photocatalytic membranes, A-TiO2/PDA@TFC and A-TiO2/PTFE@TFC. Compared with the pristine TFC-FO membrane, both A-TiO2/PDA @TFC and A-TiO2/PTFE@TFC had an improved water permeability (10.5 L m−2h−1 and 9.5 L m−2 h−1, respectively) and reduced reverse NaCl flux salt (0.8 g m−2 h−1 and 0.7 g m−2 h−1, respectively) in the AL-DS mode using 1 mol/L NaCl as draw solution and pure water as feed solution. Moreover, in the 16 h fouling experiment using 200 ppm bovine serum albumin (BSA) solution as a representative pollutant, the flux decline rate of both photocatalytic membranes was dramatically alleviated from 39.7% and 21.7% in the darkness to 8.5% and 9.7% under UV irradiation, respectively, indicating a significant anti-fouling capacity of photocatalytic effect. In all, the presence of A-TiO2 endowed membrane with high permeability, high rejection efficiency and excellent anti-fouling capacity under UV spotlight. As bonding agent, PTFE provided the modified membrane with a high photocatalytic effect and high self-cleaning capacity, while PDA increased the membrane permeability and protected membrane against photocatalytic damage. This work provides a simple and feasible method to improve the anti-fouling capacity of TFC-FO membrane in AL-DS mode.

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.

Improved Forward Osmosis Performance of Thin Film Composite Membranes with Graphene Quantum Dots Derived from Eucalyptus Tree Leaves.

The major challenges in forward osmosis (FO) are low water flux, high specific reverse solute flux (SRSF), and membrane fouling. The present work addresses these problems by the incorporation of graphene quantum dots (GQDs) in the polyamide (PA) layer of thin-film composite (TFC) membranes, as well as by using an innovative polyethersulfone nanofiber support for the TFC membrane. The GQDs were prepared from eucalyptus leaves using a facile hydrothermal method that requires only deionized water, without the need for any organic solvents or reducing agents. The nanofiber support of the TFC membranes was prepared using solution blow spinning (SBS). The polyamide layer with GQDs was deposited on top of the nanofiber support through interfacial polymerization. This is the first study that reports the fouling resistance of the SBS-nanofiber-supported TFC membranes. The effect of various GQD loadings on the TFC FO membrane performance, its long-term FO testing, cleaning efficiency, and organic fouling resistance were analyzed. It was noted that the FO separation performance of the TFC membranes was improved with the incorporation of 0.05 wt.% GQDs. This study confirmed that the newly developed thin-film nanocomposite membranes demonstrated increased water flux and salt rejection, reduced SRSF, and good antifouling performance in the FO process.

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.

Anti-fouling and highly permeable thin-film composite forward osmosis membranes based on the reactive polyvinylidene fluoride porous substrates

Currently, thin-film composite (TFC) forward osmosis (FO) membranes are widely developed for wastewater purification, although it is a pressing subject to further improve its permeability, selectivity, and fouling resistance. Here, the polyvinylidene fluoride (PVDF) membranes were modified with dopamine (DA) and polyethyleneimine (PEI) via surface segregation during non-solvent induced phase separation (NIPS). And then some residual amine groups on the as-prepared PVDF/DA-PEI membranes participated in the reaction with 1,3,5-benzenetricarboxylic acid chloride (TMC) by interfacial polymerization (IP), forming the TFC FO membranes. Furthermore, they were co-deposited by tannic acid (TA) and taurine, engineering the tTFC FO membranes. The introduction of DA and PEI in the substrate enhances the selectivity of the membrane having a low specific reverse solute flux (Js/Jw), and the TA-taurine layer improves the anti-fouling of the surface. Especially, tTFC6 (6 represents the weight concentration of DA and PEI in the substrate) has an excellent performance has a large Jw of 42.10 ± 0.86 L m−2 h−1, a low Js/Jw of 0.06 ± 0.02 g/L, and a high flux recovery (FRR) of more than 90% using bovine serum albumin (BSA), sodium alginate (SA), and SiO2 nanoparticles as model contaminants. The results provide new insights into the preparation of highly permeable and anti-fouling FO membranes.

Biogenic silver nanoparticles-modified forward osmosis membranes with mitigated internal concentration polarization and enhanced antibacterial properties

Thin-film composite forward osmosis (TFC-FO) membranes show the potential to be applied in water treatment applications. However, the TFC-FO membrane performance was limited by internal concentration polarization (ICP) and membrane fouling. In this study, a well-functioning TFC-FO membrane was produced by embedding biogenic silver nanoparticles (BioAg) into the polysulfone (PSf) substrate of a FO membrane. Effects of BioAg on membrane structure, filtration performance, antifouling, and antibacterial properties of the as-prepared FO membranes were examined. Results indicated that BioAg-modified FO membranes achieved improved surface hydrophilicity, higher porosity, and mitigated ICP, resulting in 2.5–4.4 times higher water flux than the pristine FO membranes. The BioAg-modified FO membrane also showed significantly improved antifouling and antibacterial ability. Moreover, the release velocity of silver nanoparticles in FO membranes was significantly slowed down by the construction of the polyamide layer. After 30 days of immersion in an aqueous solution, 96.5% of silver was retained in the optimized BioAg-modified FO membrane. The study offers an effective approach to simultaneously mitigate ICP and enhance the antifouling property of TFC-FO membranes through substrate modification.