Tailor-made polyamide membranes for water desalination.

Reverse osmosis (RO) is considered as the most widely utilized technique worldwide for water treatment. However, the commercial thin-film composite (TFC) membranes, which are normally made of polyamide (PA) through interfacial polymerization (IP), still experience certain major issues in performance and fabrication. The spin assisted layer-by-layer (SA-LbL) technique was established for overcoming some drawbacks with commercially available PA membranes. Also, recent investigations have recognized the nanoparticle inclusion into the selective layer as a powerful technique for improving the membrane efficiency. Hence, two different methodologies are presented here to improve the membrane performance, i.e., (1) SA-LbL technique to fabricate TFC membrane by the deposition of alternate ultrathin layers of different polyelectrolytes on polysulfone (PSF) commercial ultrafiltration membrane and (2) the nanoclay incorporation into the membranes during IP process to develop TFC membrane. Two types of nanoclays, cloisite (CS)-15A and montmorillonite (MNT), were incorporated to enhance the separation efficiency. This SA-LbL is an innovative method for the RO membrane manufacture, and has not been described earlier to the best of our knowledge. In addition, this work validated for the first time, the efficiency of the two nanoclays at the PA selective layer in the RO membrane. The membrane performance was evaluated using sodium chloride solution in a cross-flow permeation-testing cell for salt rejection and water flux. The results show significant improvement in water flux and salt rejection. The permeation test of 120 bilayers of poly (allylaminehydrochloride)/poly (vinylsulfate) on PSF substrate showed water flux of 37 L/ (m2.h) and salt rejection of 53%, for a 2000-ppm salt solution feed. The highest water flux of 40 L/m2.h with 80% salt rejection, relative to the control membrane was obtained for the membranes containing nanoclays at 25oC temperature, 40.0 bar pressure and 2000 ppm feed concentration. Thus, our study demonstrated that these TFC membranes are promising, and these novel fabrication techniques are great tool to manufacture the RO membrane.

Correlations between conditions of the polyaniline (PANI) interlayer formation on the surface of a polysulfone (PSF) porous membrane substrate and the structure and performance of thin-film composite (TFC) membranes for nanofiltration with a polyamide (PA) selective layer prepared via interfacial polymerization (IP) were studied. It was shown that application of the PANI layer significantly enhanced hydrophilicity (the water contact angle decreased from 55 ± 2° down to 26-49 ± 2°), decreased pore size and porosity, and increased the surface roughness of the selective layer surface of porous PSF/PANI membrane substrates due to the formation of bigger PANI globules, which affect the formation of the PA layer of TFC membranes via IP. It was shown that the application of the PANI intermediate layer yielded the formation of a thinner PA selective layer, a decline in surface roughness, and an increase in hydrophilicity (the water contact angle declined from 28 to <10°) and crosslinking degree of the selective layer of TFC NF membranes. The developed approach allows us to enhance the water permeation up to 45-64 L·m-2·h-1 at ΔP = 0.5 MPa and improve membrane selectivity (rejection coefficient of MgSO4->99.99%; LiCl-5-25%; sulfadimetoxine-80-95%) and also ensure enhanced long-term operational stability of TFC nanofiltration membranes with a PANI interlayer. Moreover, Mg2+/Li+ separation factor values were found to increase to 37 and 58 for PANI-modified membranes compared to 9 and 8 for the reference NF-PSF membranes.

Interfacial polymerization of thin film selective membrane layers: Effect of polyketone substrates

Sulfonated polyaniline interlayer with controllable doping conditions for high-performance nanofiltration

Significant progress has been made in recent years in the fabrication of CO2 separation membranes using thin-film composite membranes (TFCs) prepared by the interfacial polymerization (IP) process. However, more advancement is still required to realize the full potential of IP-TFCs in highly permeable/selective gas separation membranes. Here, nitrogen-doped graphene oxide (N-GO) nanosheets and dicationic imidazolium ionic liquids (ILs) with two different aliphatic linkers (i.e., trimethylene and hexamethylene), C3IL and C6IL, respectively, are added in the polyamide (PA) selective layer of a TFC membrane, and the gas separation performance of the membranes is investigated. With the incorporation of the C3IL/N-GO additive, the CO2 permeance and CO2/CH4 and CO2/N2 selectivities of the TFC membranes are increased by 900, 2, and 6%, respectively. On the other hand, the corresponding increases in the CO2 permeance and CO2/gas selectivities, by introducing the C6IL/N-GO additive are 700, 9, and 16%, respectively. These enhancements are attributed to the role of IL molecules in improving the distribution of N-GO nanosheets in the PA selective layer of TFCs, tuning the N-GO sieving channels in favor of CO2 transport, and creating ultrasmall holes which are highly accessible to CO2 molecules. We believe that the incorporation of IL/GO additives into the selective layer of IP-TFCs will pave the way to improving the gas separation performance of thin-film composite membranes.

With the blooming of oil and gas industries, oily saline wastewater treatment becomes a viable option to resolve the oily water disposal issue and to provide a source of water for beneficial use. Reverse osmosis (RO) has been touted as a promising technology for oily saline wastewater treatment. However, one great challenge of RO membrane is fouling phenomena, which is caused by the presence of hydrocarbon contents in the oily saline wastewater. This study focuses on the fabrication of antifouling RO membrane for accomplishing simultaneous separation of salt and oil. Thin film nanocomposite (TFN) RO membrane was formed by the layer by layer (LbL) assembly of positively charged TNS (pTNS) and negatively charged TNS (nTNS) on the surface of thin film composite (TFC) membrane. The unique features, rendered by hydrophilic TNS bilayer assembled on TFC membrane in the formation of a hydration layer to enhance the fouling resistance by high concentration oily saline water while maintaining the salt rejection, were discussed in this study. The characterization findings revealed that the surface properties of membrane were improved in terms of surface hydrophilicity, surface roughness, and polyamide(PA) cross-linking. The TFC RO membrane coated with 2-bilayer of TNS achieved >99% and >98% for oil and salt rejection, respectively. During the long-term study, the 2TNS-PA TFN membrane outperformed the pristine TFC membrane by exhibiting high permeability and much lower fouling propensity for low to high concentration of oily saline water concentration (1000 ppm, 5000 ppm and 10,000 ppm) over a 960 min operation. Meanwhile, the average permeability of uncoated TFC membrane could only be recovered by 95.7%, 89.1% and 82.9% for 1000 ppm, 5000 ppm and 10,000 ppm of the oily saline feedwater, respectively. The 2TNS-PA TFN membrane achieved almost 100% flux recovery for three cycles by hydraulic washing.

Thin-film composite (TFC) structure has been widely employed in polymeric membrane fabrication to achieve superior performance for desalination and water treatment. In particular, TFC membranes with a thin active polyamide (PA) selective layer are proven to offer improved permeability without compromising salt rejection. Several modifications to TFCs have been proposed over the years to enhance their performance by altering the selective, intermediate, or support layer. This study proposes the modification of the membrane support using nanozeolites prepared by a unique ball milling technique for tailoring the nanofiltration performance. TFC membranes were fabricated by the interfacial polymerization of Piperazine (PIP) and 1,3,5-Benzenetricarbonyl trichloride (TMC) on Polysulfone (PSf) supports modified with nanozeolites. The nanozeolite concentration in the casting solution varied from 0 to 0.2%. Supports prepared with different nanozeolite concentrations resulted in varied hydrophilicity, porosity, and permeability. Results showed that optimum membrane performance was obtained for supports modified with 0.1% nanozeolites where pure water permeance of 17.1 ± 2.1 Lm−2 h−1 bar−1 was observed with a salt rejection of 11.47%, 33.84%, 94%, and 95.1% for NaCl, MgCl2, MgSO4, and Na2SO4 respectively.

Improved performance of thin-film composite membrane with PVDF/PFSA substrate for forward osmosis process

Nanofiltration membranes (NFMs) with superior permeability and high rejection of both divalent anions and cations are highly desirable to meet the increasing separation demands of complex systems. Herein, we propose a three-in-one strategy to develop a state-of-the-art dually charged thin-film composite (TFC) nanofiltration membrane consisting of a positively charged electrospun nanofiber substrate (NFS) with surface mineralization and a negatively charged polyamide (PA) selective layer prepared by interfacial polymerization (IP). The highly hydrophilic mineralized nanofiber substrate not only effectively reduces the thickness of the PA selective layer but also crumples its structures by the abundant zirconia nanoparticles on the substrate surface, resulting in excellent water flux (15.0 L m-2 h-1 bar-1) for the TFC NFMs. The relationship between the thickness of the selective layer and substrate is further investigated using dissipative particle dynamics (DPD) simulations. Meanwhile, the dually charged NFM exhibits relatively high rejection for both anions (97.1% for Na2SO4 and 97.9% for MgSO4) and cations (87.9% for MgCl2) in aqueous solutions compared with single-charged membranes, which is attributed to the dual-repulsion effect of the selective layer and the substrate surface bearing opposite charges. Moreover, the prepared NFMs exhibit good stability and excellent antifouling performance. This work may pave the way for the development of highly efficient nanofiltration membranes for the practical separation of comprehensively charged solutes.

Thin film composite membranes containing intrinsic CD cavities in the selective layer

Poly(N-isopropylacrylamide) (PNIPAAm) was introduced into a polyethylene terephthalate (PET) nonwoven fabric to develop novel support for polyamide (PA) thin-film composite (TFC) membranes without using a microporous support layer. First, temperature-responsive PNIPAAm hydrogel was prepared by reactive pore-filling to adjust the pore size of non-woven fabric, creating hydrophilic support. The developed PET-based support was then used to fabricate PA TFC membranes via interfacial polymerization. SEM–EDX and AFM results confirmed the successful fabrication of hydrogel-integrated non-woven fabric and PA TFC membranes. The newly developed PA TFC membrane demonstrated an average water permeability of 1 L/m2 h bar, and an NaCl rejection of 47.0% at a low operating pressure of 1 bar. The thermo-responsive property of the prepared membrane was studied by measuring the water contact angle (WCA) below and above the lower critical solution temperature (LCST) of the PNIPAAm hydrogel. Results proved the thermo-responsive behavior of the prepared hydrogel-filled PET-supported PA TFC membrane and the ability to tune the membrane flux by changing the operating temperature was confirmed. Overall, this study provides a novel method to fabricate TFC membranes and helps to better understand the influence of the support layer on the separation performance of TFC membranes.

Thin-film composite membranes fabricated directly on a large-porous ceramic support using poly (4-styrenesulfonic acid) as a scaffold for ethanol dehydration

Water scarcity has intensified the demand for efficient desalination technologies, making membrane engineering a crucial research focus. A novel type of thin film composite nanofiltration membrane was developed by doping exfoliated molybdenum disulfide nanosheets as fillers within polysulfone and thin film composite membranes. Thin film composite membranes were achieved by interfacial polymerization using m ‐phenylenediamine and trimesoyl chloride monomers. Exfoliated molybdenum disulfide nanosheets were finely dispersed in a polysulfone matrix as observed by optical microscopy. The synergistic integration of molybdenum disulfide nanosheets with the polyamide layer led to improved hydrophilicity, porosity and mechanical strength, promoting rapid water transport. The optimized membrane containing 1.5 wt% molybdenum disulfide achieved a pure water flux of 118 L m −2 h −1 and salt rejection of 40.1% (NaCl) and 64.4% (MgSO₄), compared with 70 L m −2 h −1 , 19.9% and 32.6% for pristine polysulfone. These results highlight the potential of 2D‐material engineering for high‐efficiency water purification. © 2026 Society of Chemical Industry.

Thin-film composite P84 co-polyimide hollow fiber membranes for osmotic power generation

Integrated polyamide thin-film nanofibrous composite membrane regulated by functionalized interlayer for efficient water/isopropanol separation