Non-solvent Induced Phase Inversion Research Articles

The anti-fouling and mechanism of Fe3O4@PVDF catalytic membrane in-situ coupling Fenton oxidation for organic pollutants removal

Polyvinylidene fluoride (PVDF) membrane is a promising technique for deep treatment of organic wastewater. However, the unavoidable membrane contamination greatly restrictions its field of application. Herein, we successfully prepared Fe3O4@PVDF membrane with excellent anti-fouling and catalytic ability by non-solvent induced phase inversion method. Meanwhile, Fe3O4@PVDF membrane was characterized by SEM, XRD, FTIR, Water contact Angle and membrane aperture analyzer. The properties of separation and anti-fouling were also evaluated by cross flow filtration of humic acid (HA). Compare with pristine membrane, the pure water flux, rejection rate and FRR respectively increase from 556.81 L m-2 h−1, 65.42 %, 68.26 % to 656.96 L m-2 h−1, 99.64 %, 90.17 % under in-situ Fenton reaction condition. In addition, further mechanistic insights by XDLVO theory, 3D-EEM and EPR verified that high anti-fouling mainly attribute to excellent hydrophilicity of Fe3O4@PVDF and in-situ degradation of HA by OH and 1O2· This work provides insights for improving the separation properties and anti-fouling properties of PVDF membrane in the field of treatment organic wastewater.

Development of conductive two-dimensional metal-organic frameworks self-cleaning membrane for enhanced antibiotics rejection and sustainable fouling mitigation

In this study, a novel electroactive NF membrane was constructed for ultrafast rejection of antibiotics with high selectivity and self-cleaning by incorporating a conductive two dimensional metal-organic frameworks (Cu-HHTP) into porous polyvinylidene fluoride (PVDF) matrix with facile and scalable non-solvent induced phase inversion strategy. Cu-HHTP membrane showed two orders of magnitude higher permeability (198.4 L m−2 h−1·bar−1) than the commercial and most reported NF membranes without sacrificing rejection toward negatively charged tetracycline (95.4 %), positively charged vancomycin (99.9 %) and neutrally charged valinomycin (99.9 %). Interestingly, loading Cu-HHTP with hydrophilic and porous nature can break the permeability-rejection trade-off effect and the mechanism was due to the improved water channel and pollutants sieving. Furthermore, it has stable antibiotics rejection and high flux recovery rate of 93.9 % for long-term filtration of wastewater over 264 h with low energy consumption of 0.1007 W h/L and without adding chemical cleaning agents, which demonstrated its excellent fouling control and stability. This study may guide the development of advanced self-cleaning NF membranes tailored for removal of small molecular emerging contaminants.

Enhancing Water Purification by Integrating Titanium Dioxide Nanotubes into Polyethersulfone Membranes for Improved Hydrophilicity and Anti-Fouling Performance.

Water pollution remains a critical concern, one necessitated by rapidly increasing industrialization and urbanization. Among the various strategies for water purification, membrane technology stands out, with polyethersulfone (PES) often being the material of choice due to its robust mechanical properties, thermal stability, and chemical resistance. However, PES-based membranes tend to exhibit low hydrophilicity, leading to reduced flux and poor anti-fouling performance. This study addresses these limitations by incorporating titanium dioxide nanotubes (TiO2NTs) into PES nanofiltration membranes to enhance their hydrophilic properties. The TiO2NTs, characterized through FTIR, XRD, BET, and SEM, were embedded in PES at varying concentrations using a non-solvent induced phase inversion (NIPS) method. The fabricated mixed matrix membranes (MMMs) were subjected to testing for water permeability and solute rejection capabilities. Remarkably, membranes with a 1 wt% TiO2NT loading displayed a significant increase in pure water flux, from 36 to 72 L m2 h-1 bar-1, a 300-fold increase in selectivity compared to the pristine sample, and a dye rejection of 99%. Furthermore, long-term stability tests showed only a slight reduction in permeate flux over a time of 36 h, while dye removal efficiency was maintained, thus confirming the membrane's stability. Anti-fouling tests revealed a 93% flux recovery ratio, indicating excellent resistance to fouling. These results suggest that the inclusion of TiO2 NTs offers a promising avenue for the development of efficient and stable anti-fouling PES-based membranes for water purification.

Substrate-Free Gas Diffusion Layer Based on a Nonsolvent-Induced Phase Inversion Approach for High-Performance Proton Exchange Membrane Fuel Cells

Substrate-Free Gas Diffusion Layer Based on a Nonsolvent-Induced Phase Inversion Approach for High-Performance Proton Exchange Membrane Fuel Cells

Stabilizing High-Nickel Cathodes via Interfacial Hydrogen Bonding Effects Using a Hydrofluoric Acid-Scavenging Separator

Nickel-rich layered Li transition metal oxides are the most promising cathode materials for high-energy-density Li-ion batteries. However, they exhibit rapid capacity degradation induced by transition metal dissolution and structural reconstruction, which are associated with hydrofluoric acid (HF) generation from lithium hexafluorophosphate decomposition. The potential for thermal runaway during the working process poses another challenge. Separators are promising components to alleviate the aforementioned obstacles. Herein, an ultrathin double-layered separator with a 10 μm polyimide (PI) basement and a 2 μm polyvinylidene difluoride (PVDF) coating layer is designed and fabricated by combining a non-solvent induced phase inversion process and coating method. The PI skeleton provides good stability against potential thermal shrinkage, and the strong PI–PVDF bonding endows the composite separator with robust structural integrity; these characteristics jointly contribute to the extraordinary mechanical tolerance of the separator at elevated temperatures. Additionally, unique HF-scavenging effects are achieved with the formation of –CO···H–F hydrogen bonds for the abundant HF coordination sites provided by the imide ring; hence, the layered Ni-rich cathodes are protected from HF attack, which ultimately reduces transition metal dissolution and facilitates long-term cyclability of the Ni-rich cathodes. Li||NCM811 batteries (where “NCM” indicates LiNixCoyMn1−x−yO2) with the proposed composite separator exhibit a 90.6% capacity retention after 400 cycles at room temperature and remain sustainable at 60 °C with a 91.4% capacity retention after 200 cycles. By adopting a new perspective on separators, this study presents a feasible and promising strategy for suppressing capacity degradation and enabling the safe operation of Ni-rich cathode materials.

A loose polyethersulfone hybrid nanofiltration membrane incorporated with polyethyleneimine-decorated silica nanoparticles for highly-efficient dye/salt separation

Loose nanofiltration (LNF) is a newly-developing technology for desalting dye-containing saline effluents, but suffers from membrane materials with low permeance and poor dye/salt separation selectivity. Herein, a hybrid polyethersulfone (PES) LNF membrane for dye/salt separation was prepared via a nonsolvent-induced phase inversion method, which was carried out using polyethyleneimine (PEI)-modified silica nanoparticles as a dopant. This design not only featured a hybrid PES LNF membrane with high porosity and small mean pore size, but also partially neutralized its charge and enhanced its hydrophilicity. Hybrid PES LNF membrane from a 21-wt% PES solution with 3-wt% PEI-decorated silica nanoparticles addition was demonstrated to achieve high water permeance (92.0 L m−2 h−1 bar−1) and dyes retention ratio (98.4 % for Congo Red, 98.8 % for Nile Blue A, and 95.1 % for Methyl Blue) accompanied with fully-pass for various salts (Na2SO4, NaCl, MgCl2 and CaCl2). In addition, the hybrid membrane exerted excellent resistances to strong acidic, oxidative and hot water (90 °C) environments and exhibited a pH-sensitive permeability. Multicycle test revealed that the hybrid membrane had high permeance recovery ratio (>92.8 %) and maintained its high dye retention and complete salt permeation even after 10 cycles, manifesting its outstanding fouling resistance and recyclability. Besides, the hybrid membrane repelled 92.6 % of dyes from a simulated wastewater consisting of multiple industry-applied direct dyes and salts after 12 h consecutive test, but allow 100 % of mixed salts passing through the membrane, proving its practical applicability to industrial dyeing wastewater. This study provided a simple and economically feasible route to high-performance LNF membrane production for dye/salt separation, thus popularizing LNF process in dyeing wastewater treatment, organic products purification, and resource recovery.

In-situ ionized construction of PVDF/sodium polyacrylate-grafted-PVDF blend ultrafiltration membrane with stable anti-oil-fouling ability for efficient oil-in-water emulsion separation

Traditional polymeric membranes usually suffer from serious oil fouling and quick decline of water flux when separating oil-in-water emulsions. In this work, we report the fabrication of the sodium polyacrylate (PAAS) blended polyvinylidene fluoride (PVDF) ultrafiltration membrane which behaves hydrophilicity, underwater low-oil-adhesive superoleophobicity and outstanding anti-oil-fouling ability even for viscous crude oil. The blend membrane was fabricated via a two-step method, including the nonsolvent-induced phase inversion of PVDF/polyacrylic acid-grafted-PVDF (PVDF/PAA-g-PVDF) blend membrane and the subsequent in-situ ionization of PAA into PAAS. The two-step method improves the affinity between the strong hydrophilic additive PAAS and the hydrophobic polymer matrix PVDF, thus endowing the blend membrane with long-term stable superwetting property for 1,100 days. The PVDF/PAAS-g-PVDF blend membrane can efficiently separate multiple emulsifier-stabilized oil-in-water emulsions with ultrahigh separation efficiency of 99.97% (the residual oil content in the filtrate is lower than 3 ppm after one-step separation) and high water flux of 350 L m-2 h-1 bar-1. The blend membrane also shows good cycling performance, and can be easily cleaned by water washing during several separation cycles of the crude oil-in-water emulsion. This work inspires a feasible route of fabricating stable anti-oil-fouling membranes for separation of emulsified oily water.

Preparation of heterogeneous cation exchange membrane and its contributions in enhancing the removal of Ni2+ by capacitive deionization system

Capacitive deionization (CDI), an emerging method to eliminate ions from water at a low cost, has garnered significant interest in recent years. This study evaluates the implication of cation exchange resin loading on the membrane via the nonsolvent-induced phase inversion method. After determining the quantity of resins efficiently loaded on the membrane, it was subsequently utilized as a cation exchange membrane in the membrane capacitive deionization (MCDI) unit to examine the performance removal of Ni2+. The results show that the amount of resins influenced the membrane structure and significantly improved the efficiency of Ni2+ removal. The sulfonic acid group show a strong intensity directly proportional to the quantity of resins based on the FTIR measurement. In conjunction with the enhanced resin amount, ion exchange capacity and water content were increased. Simultaneously, there was an observed elevation in the water contact angle and the roughness of the membrane surface with increased resin amount. In the MCDI unit, membrane M20 (20% by weight resin) was employed to elucidate its roles in the CDI unit, encompassing an examination of various concentrations and flow rates, with Ni2+ utilized as a test contaminant. The results demonstrated that using membrane M20 in the MCDI (MCDI-M20) unit consistently exhibited higher adsorption levels than the CDI unit, reaching 19.80 mg g−1 ACC in the MCDI-M20 unit, while CDI unit achieved 10.27 mg g−1 ACC at 200 mg L−1 Ni2+ concentration and a flow rate of 10 mL min−1 at 1.2 V. Additionally, Ni2+ concentrations and flow rates in CDI system had an evident impact on the duration of adsorption due to the mechanisms of ions transport on the membrane. This study suggests that employing the prepared membrane in the MCDI unit enhanced the removal of Ni2+ from the solution, contributing to sustainable development goals.

Sustainable additive manufacturing of polysulfone membranes for liquid separations

Membranes serve as important components for modern manufacturing and purification processes but are conventionally associated with excessive solvent usage. Here, for the first time, a procedure for fabricating large area polysulfone membranes is demonstrated via the combination of direct ink writing (DIW) with non-solvent induced phase inversion (NIPS). The superior control and precision of this process allows for complete utilization of the polymer dope solution during membrane fabrication, thus enabling a significant reduction in material usage. Compared to doctor blade fabrication, a 63% reduction in dope solution volume was achieved using the DIW technique for fabricating similarly sized membranes. Cross flow filtration analysis revealed that, independent of the manufacturing method (DIW vs. doctor blade), the membranes exhibited near identical separation properties. The separation properties were assessed in terms of bovine serum albumin (BSA) rejection and permeances (pressure normalized flux) of pure water and BSA solution. This new manufacturing strategy allows for the reduction of material and solvent usage while providing a large toolkit of tunable parameters which can aid in advancing membrane technology.

Pioneering the preparation of porous PIM-1 membranes for enhanced water vapor flow.

In this study, porous polymers of intrinsic microporosity (PIM-1) membranes were prepared by non-solvent induced phase inversion (NIPS) and investigated for water vapor transport in view of their application in membrane distillation (MD). Due to the lack of high boiling point solvents for PIM-1 that are also water miscible, the mixture of tetrahydrofuran (THF) and N-methyl-2-pyrrolidone (NMP) was found to be optimal for the formation of a membrane with a developed porous system both on the membrane surface and in the bulk. PIM-1 was synthesized by using low and high temperature methods to observe how molecular weight effects the membrane structure. Low molecular weight PIM-1 was produced at low temperatures, while high molecular weight PIM-1 was obtained at high temperatures. Several membranes were prepared, including PM-6, PM-9, and PM-11 from low molecular weight PIM-1, and PM-13 from high molecular weight PIM-1. Scanning electron microscopy (SEM) was used to image the surface and cross-section of different porous PIM-1 membranes. Among all the PIM-1 membranes (PM) obtained, PM-6, PM-9, PM-11 and PM-13 showed the most developed porous structure, while PM-13 showed large voids in the bulk of the membrane. Contact angle measurements showed that all PIM-1 porous membranes are highly hydrophobic. Liquid water flux measurements showed that PM-6, PM-9 and PM-11 showed minimal water fluxes due to small surface pore size, while PM-13 showed a high water flux due to a large surface pore size. Water vapor transport measurements showed high permeance values for all membranes, demonstrating the applicability of the developed membranes for MD. In addition, a thin film composite (TFC) membrane with PIM-1 selective layer was prepared and investigated for water vapor transport to compare with porous PIM-1 membranes. The TFC membrane showed an approximately 4-fold lower vapor permeance than porous membranes. Based on these results, we postulated that the use of porous PIM-1 membranes could be promising for MD due to their hydrophobic nature and the fact that the porous membranes allow vapor permeability through the membrane but not liquid water. The TFC membrane can be used in cases where the transfer of water-soluble contaminants must be absolutely avoided.

A strategy to build high-performance thick electrodes for lithium-ion batteries with enhanced compressive modulus and regulated tortuosity in the phase-inversion process

By tuning the composition of the non-solvent bath used in the non-solvent induced phase inversion process for fabricating thick and low-tortuosity battery electrodes, optimal electrochemical performances and compressive modulus were achieved.

NMC811 Electrodes with High Mass Loadings Enabled By Non-Solvent Induced Phase Inversion

Higher energy density Li-ion batteries that can enable longer driving ranges are currently subject to intensive research interest. Increasing the thickness of electrodes and reducing the proportion of inactive components per cell is one way to achieve this. In thick electrodes, a higher electronic and ionic overpotential and mechanical failure (cracking, delamination etc.) induced by binder migration during the drying process leads to sluggish (dis)charge performance or even cell failure respectively. Here we report non-solvent induced phase inversion as a scalable, effective method to arrive at thick NMC811 electrodes.By tuning the non-solvent properties and other processing conditions to be compatible with Ni-rich electrodes, it was possible to obtain NMC811 electrodes with mass loadings up to 11 mAh/cm2 (single sided) which outperform their conventional processed counterparts in Li/NMC half cells. This improvement could be attributed to the altered carbon-binder structure, which improves the pore connectivity and lowers the electrode tortuosity factor. The rapid solvent removal also reduces the long-range binder migration during drying. With imaging and porosimetry techniques we show the structural change which leads to the observed improved electrochemical performance. The method also shows good compatibility with double sided slot-die electrode coating procedure, making this a technique with potentially high industrial feasibility towards making thicker NMC811 and other electrodes.

Spray-assisted assembly of thin-film composite membranes in one process

Spray coating has been exploited to fabricate and tailor the morphologies of various components in thin film composite membranes separately. For the first time, here we exploit this technology to construct and assemble both the selective layer and porous support of a thin-film composite membrane in a single process. In our approach, spray-assisted non-solvent induced phase inversion and interfacial polymerization reduced the time required to fabricate thin-film composite membranes from 3 – 4 days to 1 day and 40 min. Our approach did not sacrifice membrane separation performances during desalination of a mixture comprising 2000 ppm of NaCl in water at 4 bar and room temperature. At these conditions, compared to traditional thin film composite membranes, the water permeance of our spray coated membranes was higher by 35.7 %, reaching 2.32 L m−2 h−1 bar−1, while achieving a NaCl rejection rate of 94.7 %. This demonstrated the feasibility of fabricating thin film composites via spray coating in a single process, potentially reducing fabrication time during scale-up production.

Integrating radical polymerization and non-solvent induced phase inversion strategy for functionalized ultrafiltration membrane fabrication

The facile fabrication of high-performance membranes with attractive water permeability, retention ability, and fouling resistance holds a significant interest within the realm of membrane technology advancement. In this study, we developed an integrated radical polymerization and non-solvent induced phase separation strategy for functionalized ultrafiltration membrane fabrication. This innovative approach enabled the compositive of membrane preparation and functionalization by introducing a radical initiator into the casting solution and incorporating functional monomers into the coagulation bath. We demonstrated the effectiveness of this integrated membrane fabrication method by using zwitterionic sulfobetaine methacrylate (SBMA) as a classic test case. By optimizing radical polymerization time, the SBMA/PVDF membrane achieved simultaneous enhancements in water flux (187.6 L m−1 h−1), retention ability (99.0 % rejection for BSA protein), and antifouling property (9.8 % improvement) compared with the pristine PVDF membrane. Additionally, the microstructure, hydrophilicity, and zeta potential of SBMA/PVDF membranes were deliberately controlled by regulating the radical polymerization time. Furthermore, we demonstrated the universal applicability of the integrated membrane fabrication method by replacing SBMA with antimicrobial agent monomers in the coagulation bath. Our research contributes to the field of functionalized ultrafiltration membrane fabrication by developing the integration strategy of radical polymerization and non-solvent induced phase separation.

High performance photodegradation resistant PVA@TiO2/carboxyl-PES self-healing reactive ultrafiltration membrane

The occurrence of ultrafiltration (UF) membrane fouling frequently hampers the sustainable advancement of UF technology. Reactive self-cleaning UF membranes can effectively alleviate the problem of membrane fouling. Nevertheless, the self-cleaning process may accelerate membrane aging. Addressing these concerns, we present an innovative design concept for composite self-healing materials based on self-cleaning UF membranes. To begin, TiO2 nanoparticles were incorporated into the polymer molecular structure via molecular design, resulting in the synthesis of TiO2/carboxyl-polyether sulfone (PES) hybrid materials. Subsequently, the nonsolvent-induced phase inversion technique was employed to prepare a novel of UF membrane. Lastly, a polyvinyl alcohol (PVA) hydrogel coating was applied to the hybrid UF membrane surface to create PVA@TiO2/carboxyl-PES self-healing reactive UF membranes. By establishing a covalent bond, the TiO2 nanoparticles were effectively and uniformly dispersed within the UF membrane, leading to exceptional self-cleaning properties. Furthermore, the water-absorbing and swelling properties of PVA hydrogel, along with its capacity to form hydrogen bonds with water molecules, resulted in UF membranes with improved hydrophilicity and active self-healing abilities. The results demonstrated that the water contact angle of PVA@5%TiO2/carboxyl-PES UF membrane was 43.1°. Following a 1-h exposure to simulated solar exposure, the water flux recovery ratio increased from 48.16% to 81.03%. Moreover, even after undergoing five cycles of 12-h simulated sunlight exposure, the UF membranes exhibited a consistent retention rate of over 97%, thus fully demonstrating their exceptional self-cleaning, antifouling, and self-healing capabilities. We anticipate that the self-healing reactive UF membrane system will serve as a pioneering and comprehensive solution for the self-cleaning antifouling challenges encountered in UF membranes while also effectively mitigating the aging effects of reactive UF membranes.

A novel interfacial polymerization assisted phase inversion process for the facile fabrication of ion-selective nanofiltration membranes

Interfacial polymerization (IP) and non-solvent induced phase inversion (NIPS) are the two most commonly used mainstream technologies to fabricate separation membranes. Taking their advantages, we developed a simple, facile and scalable method to integrate the IP and NIPS processes together for the fabrication of ion-selective nanofiltration membranes. Herein, amphiphilic polysulfone block hyperbranched polyglycerol (PSf-b-hPG) copolymer was synthesized and blended with polyethylene imide (PEI) to prepare a polymer casting solution in organic solvents. After casted into the liquid film of PSf-b-hPG and PEI blending solution, it was then immersed into a cross-linking solution with 0.2 wt.% trimethylchloride (TMC) in n-hexane for the generation of the polyamide layer first on top of the liquid film, and finally transferred into a water coagulation bath for the formation of the porous matrix of PSf-b-hPG membrane. The fabricated membrane exhibited a high water permeance of 12.57 L m-2h−1 bar−1 and a high separation factor of 25.08 towards Mg2+ and Li+ ions, which is superior to the perm-selectivity of the most reported nanofiltration membranes. This novel and facile process can be directly applied to the NIPS manufacturing line, eliminating a separate IP production line and holding immense potentials and advantages in scale-up production.

Novel hexa-fluorinated intrinsically porous polyimide membranes for the desalination of high saline water by air-gap membrane distillation

Hexa-fluorinated porous membranes were prepared from 4,4′-(hexafluoroisopropylidene) diphtalic anhydride (6FDA)- 2,3,5,6- tetramethyl-p-phenylenediamine (TMPD) (6FDA-TMPD), which prepared by a polycondensation reaction between the dianhydride 6FDA and the diamine TMPD at 200 °C, by nonsolvent induced phase inversion process for the desalination of highly saline water (70,000 mg L−1) via membrane distillation (MD) technology. Here, for the first time, we demonstrate the significance of the intrinsic porosity of 6FDA-TMPD polyimide membranes, that not only result in an excellent performance in MD without the addition of porogen chemicals but also outperform other membranes including commercially available membranes. The membrane characteristics were optimized by varying the coagulation bath, dope solution concentration, and thickness. Notably, the developed membranes possess high porosity which can be attributed to the high BET surface area (550 m2 g−1) of 6FDA-TMPD. Membranes developed from an ethanol-based coagulation bath resulted in spongy-like morphology and demonstrated excellent desalination performance with a high flux (∼ 18.20 kg m−2 h−1) and stable salt rejection (> 99.96 %). The reported fabrication approach can be used to delineate the key design parameters for the fabrication of highly efficient intrinsically porous polyimide-based membranes which may pave the way for the practical application of MD for the desalination of highly saline water.Graphical abstract.

Anti-fouling PVDF membranes incorporating photocatalytic biochar-TiO2 composite for lignin recycle

In this study, a photocatalytic biochar-TiO2 (C–Ti) composite was prepared using lignin as carbon precursor, and blended with PVDF polymer to fabricate PVDF/C–Ti MMMs via non-solvent induced phase inversion. The prepared membrane demonstrates both 1.5 times higher initial and recovered fluxes than the similarly prepared PVDF/TiO2 membrane, suggesting the C–Ti composite can help maintain higher photodegradation efficiency and better anti-fouling performance. In addition, the comparison of PVDF/C–Ti membrane against pristine PVDF membrane show that the reversible fouling and photodegradation reversible fouling of BSA increased from 10.1% to 6.4%–35.1% and 26.6%, respectively. And the FRR of PVDF/C–Ti membrane was 62.12%, 1.8 times that of PVDF membrane. The PVDF/C–Ti membrane was also applied for lignin separation, where the rejection to sodium lignin sulfonate was maintained at about 75%, and the flux recovery ratio after UV irradiation reached 90%. The demonstrated the advantages of PVDF/C–Ti membrane in photocatalytic degradation and antifouling performance.

Efficiency of Fabricated Adsorptive Polysulfone Mixed Matrix Membrane for Acetic Acid Separation.

The ultrafiltration mixed matrix membrane (UF MMMs) process represents an applicable approach for the removal of diluted acetic acid at low concentrations, owing to the low pressures applied. The addition of efficient additives represents an approach to further improve membrane porosity and, subsequently, enhance acetic acid removal. This work demonstrates the incorporation of titanium dioxide (TiO2) and polyethylene glycol (PEG) as additives into polysulfone (PSf) polymer via the non-solvent-induced phase-inversion (NIPS) method to improve the performance of PSf MMMs performance. Eight PSf MMMs samples designated as M0 to M7, each with independent formulations, were prepared and investigated for their respective density, porosity, and degree of AA retention. Morphology analysis through scanning electron microscopy elucidated sample M7 (PSf/TiO2/PEG 6000) to have the highest density and porosity among all samples with concomitant highest AA retention at approximately 92.2%. The application of the concentration polarization method further supported this finding by the higher concentration of AA solute present on the surface of the membrane compared to that of AA feed for sample M7. Overall, this study successfully demonstrates the significance of TiO2 and PEG as high MW additives in improving PSf MMM performance.

Covalent organic frameworks modified with TA embedded in the membrane to improve the separation of heavy metals in the FO

The Schiff base network-1 (SNW-1) was synthesized by the Schiff-base reaction method and then modified using tannic acid (TA). To make a thin film nanocomposite (TFC) membrane by using the nonsolvent-induced phase inversion (NIPs) method, it was embedded in the matrix of the forward osmosis (FO) polyethersulfone (PES) membrane and used to check the performance of the desalination and removal of heavy metals. SNW-1 and covalent organic framework modified tannic acid (STA) nanoparticles were characterized using FTIR, XRD, FESEM, TEM, BET, and TGA analyses. The results indicated the successful synthesis and modification nanoparticles. The effect of SNW-1 and STA nanoparticles on the surface properties of membranes were investigated using contact angle, porosity, pore size, ATR-FTIR, SEM, and AFM analyses. The results showed an extraordinary increase in hydrophilicity, softening of the membrane surface, and an enhancement in finger-like pores for water passage. Due to the presence of the hyperbranched polymer like TA next to SNW-1, in addition to creating a synergistic effect in increasing hydrophilicity and porosity, caused the removal of impurities. The results showed an increase in the permeability and rejection of the membranes modified with STA compared to the pure membrane and the modified membrane with SNW-1. Also, the TFC-STA membrane showed lower coefficient of salt permeability (B) to coefficient of water permeability (A) of RO setup (B/A), and lower salt permeation (Js) to water permeation (Jw) of FO setup (Js/Jw) coefficients than the modified TFC@SNW-1 membranes.