PH-mediated polyethyleneimine-based thin-film composite membranes for high-performance pervaporation desalination

ABSTRACTThe purpose of this research is to explain the surface modification of fabricated polyamide reverse osmosis (RO) membranes using UV‐initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g L−1). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm) followed by the same UV irradiation times was investigated. After that, the membranes modification was done by grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. The characterization of membranes surface properties and their performance were systematically carried out. The results demonstrated the enhanced hydrophilicity of modified membranes and confirmed the presence of acrylamide and nanoparticles on the membranes surface. Acrylamide‐grafted membranes could reach to higher water flux than pristine membrane with little reduction in salt rejection. Moreover, TiO2‐coated membranes indicated enhancement of water flux continuously with increase in nanoparticles concentration and irradiation time and rejection of membranes was slightly decreased at low irradiation times. Also, RO membranes modified simultaneously with acrylamide and TiO2 nanoparticles under UV irradiation exhibited improved water flux up to 18%, slightly higher rejection, and considerable better fouling resistance compared with pristine one. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48461.RESEARCH HIGHLIGHTS Aromatic polyamide thin film composite reverse osmosis (RO) membranes fabricated through interfacial polymerization process between m‐phenylenediamine and trimesoyl chloride on the porous polysulfone support. The desirable UV irradiation time for surface modification of RO membranes was up to 90 s. Modification of RO membranes surface was carried out by UV‐initiated grafting of acrylamide, coating of membranes surface with TiO2 nanoparticles followed by the UV irradiation, and grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. ATR‐FTIR, SEM, EDX, and AFM confirmed modification of membranes surface with acrylamide, TiO2 nanoparticles, and both of them. All modified membranes had lower contact angle than unmodified one indicating enhanced surface hydrophilicity. Acrylamide‐grafted membranes could result in higher water flux than unmodified membrane with little reduction in salt rejection. TiO2‐coated membranes indicated improvement of water flux with increase in nanoparticles concentration and irradiation time and rejection of membranes was decreased slightly at low UV irradiation times. RO membranes modified simultaneously with acrylamide and TiO2 nanoparticles under UV irradiation had improved water flux, slightly higher rejection, and considerable enhanced antifouling property compared with unmodified one.

Desalination is the process of removing salts and minerals from saline water to produce potable water. It is a critical global challenge due to the increasing demand for freshwater. Pervaporation (PV) is a membrane-based separation process that combines sorption and permeation, and it has emerged as a promising alternative to traditional desalination methods. This review provides a comprehensive overview of recent advancements in the development and application of polymer membranes for PV desalination. We begin by discussing the fundamental principles of PV and exploring its mechanism, underscoring its preparation methods, such as solution coating, solution casting, and interfacial polymerization. The review then delves into various types of polymer membranes used in PV desalination, such as cellulose and its derivatives, polyvinyl alcohol, polyacrylonitrile, polyamides and sulfonated block copolymers, describing their chemical structures, synthetic techniques, and performance characteristics. Special attention is given to the role of membrane properties—such as hydrophilicity, compositions and functionality—in determining the efficiency of salt rejection and water flux. Then, the cleaning of contaminated PV polymer-based membranes is reviewed. Furthermore, we discuss the challenges and limitations associated with polymer membranes in PV desalination, which include fouling, swelling, and chemical degradation, and present strategies to mitigate these issues. The review aims to serve as a resource for researchers, engineers, and policymakers interested in advancing the state of the art in PV desalination technologies and addressing the global water scarcity crisis through innovative membrane science.

Development of high performance pervaporation desalination membranes: A brief review

Thin film nanocomposite (TFN) reverse osmosis (RO) membranes were prepared by dispersing 3-aminopropyltriethoxysilane (APTES) modified hydrotalcite (HT), designated as A-HT, in aqueous solution and incorporating the nanoparticles in polyamide layers during the interfacial polymerization process. Results of Fourier transform infrared spectroscopy and zeta potential characterization showed the successful modification of nanoparticles by APTES. In addition, Fourier transform infrared spectroscopy suggested that amidation would take place between the aminosilane on APTES and trimesoyl chloride in organic solution, providing firm covalent interaction between the nanoparticles and polyamide matrix. Dynamic light scattering and transmission electron microscopy indicated that aminosilane modification improved dispersibility of the nanoparticles in aqueous solution and obtained membranes, which suppressed the aggregation. Both the covalent interaction and aggregation suppression were beneficial to compatibility between nanoparticles and the polyamide matrix. TFN RO membranes incorporated with A-HT demonstrated excellent performance. Compared with the pristine RO membrane, the water flux of A-HT-0.050 prepared with an optimum A-HT concentration of 0.050 wt% was enhanced by 18.6% without sacrificing the salt rejection. Moreover, the selectivity of A-HT-0.050 was superior to that of HT-0.050 prepared with HT of 0.050 wt%, which proved aminosilane modification of hydrotalcite was beneficial to high membrane performance especially to selectivity.

Studies on the fouling behavior and cleaning method of pervaporation desalination membranes for reclamation of reverse osmosis concentrated water

Although pervaporation (PV) desalination is a promising solution to global freshwater scarcity, membranes suffer from unstable separation performance. This study utilized resource recycling to prepare a porous ceramic membrane using solid waste fly ash as raw material, which was then combined with polyimide (PI) to produce a high-performance composite membrane (abbreviated to as PI/ceramic membrane). In this composite membrane, the ceramic membrane provides mechanical support and promotes rapid water passage, while the PI layer intercepts hydrated salt ions through size screening and electronic repulsion. Through their synergistic action, the composite membrane can preferentially adsorb and diffuse water molecules while retaining. Results indicate in addition to a retention efficiency of nearly 99.9%, the PI/ceramic membranes achieved a permeability of 10.88 L (m−2 h−1), which is superior to other existing polymer-modified membranes. Simultaneously, the membrane demonstrates selective ion rejection (e.g., SO42− and Mg2+) while maintaining stable rejection performance at 90 °C. A 45-hour continuous operation test confirmed the composite membrane's stability, demonstrating consistent performance. This study provides a novel approach for the preparation of polymer-modified membranes for industrial wastewater desalination.

A nanofibrous composite reverse osmosis (RO) membrane with a polyamide barrier layer containing interfacial water channels was fabricated on an electrospun nanofibrous substrate via an interfacial polymerization process. The RO membrane was employed for desalination of brackish water and exhibited enhanced permeation flux as well as rejection ratio. Nanocellulose was prepared by sequential oxidations of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and sodium periodate systems and surface grafting with different alkyl groups including octyl, decanyl, dodecanyl, tetradecanyl, cetyl, and octadecanyl groups. The chemical structure of the modified nanocellulose was verified subsequently by Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), and solid NMR measurements. Two monomers, trimesoyl chloride (TMC) and m-phenylenediamine (MPD), were employed to prepare a cross-linked polyamide matrix, i.e., the barrier layer of the RO membrane, which integrated with the alkyl groups-grafted nanocellulose to build up interfacial water channels via interfacial polymerization. The top and cross-sectional morphologies of the composite barrier layer were observed by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) to verify the integration structure of the nanofibrous composite containing water channels. The aggregation and distribution of water molecules in the nanofibrous composite RO membrane verified the existence of water channels, demonstrated by molecular dynamics (MD) simulations. The desalination performance of the nanofibrous composite RO membrane was conducted and compared with that of commercially available RO membranes in the processing of brackish water, where 3 times higher permeation flux and 99.1% rejection ratio against NaCl were accomplished. This indicated that the engineering of interfacial water channels in the barrier layer could substantially increase the permeation flux of the nanofibrous composite membrane while retaining the high rejection ratio as well, i.e., to break through the trade-off between permeation flux and rejection ratio. Antifouling properties, chlorine resistance, and long-term desalination performance were also demonstrated to evaluate the potential applications of the nanofibrous composite RO membrane; remarkable durability and robustness were achieved in addition to 3 times higher permeation flux and a higher rejection ratio against commercial RO membranes in brackish water desalination.

Pervaporation (PV) desalination, a promising technology to produce clean water, lacks some fundamental understanding of the molecular transport mechanism. We perform molecular dynamic simulations to unravel the molecular transport mechanism in polyvinyl alcohol PV desalination membranes. It is revealed that the dispersion forms of confined water molecules transform from nano-sized clusters to single molecules as the concentration gradient decreases within the membrane. The diffusion modes of confined water molecules with various dispersion forms are distinguished. The solvation free energy analysis explains the compensation mechanism of ions in membranes. Based on the simulation results, an analytical expression is derived to describe the relationship between the transport diffusion coefficient and solubility of confined water molecules. Using this analytical expression, a solution-diffusion model is established to calculate the permeability of PV desalination, and is validated with experimental results. These findings pave an avenue for building a theoretical framework of PV desalination.

Silicalite nanosheet (SN) laminated membranes are promising for pervaporation (PV) desalination of concentrated brines for water purification and critical material concentration and recovery. However, scaling up the SN-based membranes is limited by inefficient synthesis of monodispersed open-pore SN single crystals (SNS). Here, we report a scalable approach to fabricate multilayered silicalite nanosheet plate (SNP) laminated membranes on porous alumina and PVDF substrates and demonstrate their excellent PV desalination performance for simulated brines containing lithium and high total dissolved salts (TDS). At 73 ± 3 °C, the SNP laminated membrane on alumina support achieved a remarkable water flux () of nearly 20 L/m2·h, significantly outperforming the alumina-supported SNS laminated membrane ( = 9.56 L/m2·h), while both provided near-complete salt rejection ( ~99.9%) when operating with vacuum pressure on the permeate side. The PVDF-supported SNS and SNP laminated membranes exhibited excellent (14.0 L/m2·h) and near-complete (>99.9%), surpassing the alumina-support SNP laminated membranes when operating by air sweep on the permeate side. However, the of the PVDF-supported membranes was found to decline when operating with vacuum pressure on the permeate side that was apparently caused by minimal liquid permeation through the inter-SNP spaces driven by the transmembrane pressure. With scalable SNP production, SNP-A membranes show potential for PV desalination of high-TDS solutions, especially in harsh environments unsuitable for polymer membranes.

Emerging sandwich-like reverse osmosis membrane with interfacial assembled covalent organic frameworks interlayer for highly-efficient desalination

Tuning interlayer structure to construct steady dual-crosslinked graphene oxide membranes for desalination of hypersaline brine via pervaporation

This study validates, for the first time, the effectiveness of two nanoclays, that is, cloisite (CS)-15A and montmorillonite (MNT) at the polyamide (PA) active layer in the reverse osmosis (RO) membrane. Cloisite-15A is natural montmorillonite modified with dimethyl dihydrogenated tallow quaternary ammonium salt. Thin-film composite (TFC) membranes were fabricated by the interfacial polymerization (IP) process between the trimesoylchloride (TMC)–n-hexane solution and m-phenylenediamine (MPD)–aqueous solution; the IP process took place on a polysulfone support sheet. The two types of nanoparticles were added in various weight ratios (0.005 wt.%–0.04 wt.%) in the n-hexane solution of TMC. Different characterizations like X-ray diffraction (XRD), contact angle, transmission electron microscopy (TEM), and membrane performance tests were performed to analyse the membrane properties. Both XRD and TEM studies proved that the two nanoclays are successfully anchored at the different sites of the PA layer. CS-15A could accelerate the water flux from 15 to 18.65 L/m2·h with NaCl rejection enhancement from 72% to 80%, relative to the control membrane. Conversely, MNT also enhanced the flux from 15 to 40 L/m2·h, but NaCl rejection reduced from 70% to 23%. The mechanism of water uptake in nanoclays was also discussed. The results pave the way for a complete future study, in which these phenomena should be studied in great detail.

Polyvinyl alcohol (PVA) is a promising membrane material for pervaporation (PV) desalination. However, the adjustment and control of the cross‐linking structure is still a challenge for PVA membrane. In this study, a novel pH‐resistant PVA‐based composite membrane for efficient pervaporation desalination was developed by precisely adjusting the cross‐linking behavior. Vinyl alcohol‐vinylamine copolymer (VA‐co‐VAm) containing both hydroxyl and amino groups was synthesized. Cross‐linking reaction was carried out based on the Schiff base reaction between amino groups (in VAm moiety) and glutaraldehyde (GA) under alkaline conditions. Cross‐linking degree of PVA selective layer was carefully controlled by adjusting the amino group content in copolymer. Results showed that membrane prepared with VA‐co‐VAm that containing 5 wt% N‐vinylformamide (NVF) displayed superior hydrophilicity and the largest free volume fraction. Pervaporation test indicated that the modified cross‐linking membrane showed good stability under extreme pH conditions. Specifically, under strong acid conditions (pH ~ 1) and alkaline conditions (pH ~ 14), the membrane showed excellent desalination performance with water flux over 12 kg/(m2 h), and the salt rejection higher than 99.95%. Based on the above results, the prepared membrane offers a promising platform for desalination under extreme pH conditions, which shows great potential in industrial wastewater treatment.

A novel thin-film nanocomposite (TFN) reverse osmosis (RO)/non-woven fabric (NWF) membrane was prepared by adding zinc oxide (ZnO) nanospheres (30+-10 nm) during the interfacial polymerization process of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on self-made polysulfone (PSF) membrane/polyester (PET) non-woven fabric support. The improved performance of TFN RO membrane was verified in terms of water contact angle (WCA), water flux, salt rejection, antifouling properties and chlorine resistance. The results showed that the WCA value of TFN RO surface had a continuous decrease with the increasing of ZnO content in MPD aqueous solution. The water flux of composite TFN RO membranes acquired a remarkable increase with a stable high solute rejection (94.5 %) in 1 g.L-1 NaCl aqueous solution under the optimized addition amount of ZnO (1 wt%). The continuous testing of membrane separation performance after the immersion in sodium hypochlorite solution indicated that the introduction of ZnO nanospheres also dramatically enhanced the antifouling properties and the chlorine resistance of composite RO membranes.

The polyamide reverse osmosis (RO) membranes were prepared through interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). The use of dimethyl sulfoxide (DMSO) and glycerol as additives for the formation of thin-film composite (TFC) was investigated. We studied the effect of DMSO and glycerol addition on membrane property and RO performance. Microscopic morphology was examined by atomic force microscopy and scanning electron microscopy. The surface hydrophilicity was characterized on the basis of water contact angle and surface solid-liquid interfacial free energy (-ΔGSL). Water flux and salt rejection ability of the membranes prepared with or without the additives were evaluated by cross-flow RO tests. The results reveal that the addition of DMSO and glycerol strongly influences the property of the TFC RO membrane. Compared to the MPD/TMC membrane fabricated without DMSO and glycerol, the MPD/TMC/DMSO/glycerol membrane has a rougher surface and is more hydrophilic, showing smaller water contact angle and larger -ΔGSL value. Without decrease in salt rejection ability, the MPD/TMC/DMSO/glycerol membrane shows water flux significantly larger than that of the MPD/TMC membrane. The unique property of the MPD/TMC/DMSO/glycerol membrane is attributed to the cooperative effect of DMSO and glycerol on membrane structure during the interfacial polymerization process.