Search

In this work, we demonstrated the effectiveness of using spray-assisted interfacial polymerization (IP) technique in fabricating liposome-integrated thin film nanocomposite (TFN) membranes for seawater reverse osmosis (SWRO). The liposome loading within the selective polyamide (PA) layer of the TFN membrane can be precisely controlled by manipulating spraying conditions to eliminate the wastage of precious additives compared to the conventional blending method. Spraying the liposomes after applying the aqueous phase of M -phenylenediamine (MPD) could prevent the loss and disruption of liposome distribution over the substrate layer. Upon incorporating 4 mg/m2 of liposomes, the best-performing S4-a membrane is able to achieve 27% higher water permeability than the liposome-free membrane, demonstrating a permeability of 3.24 L/m2·h·bar along with 99.3% NaCl rejection for seawater desalination. Characterization showed that dynamic liposomes had affected the IP process by creating a larger miscible reaction zone for IP, which led to the formation of a rougher PA surface with more nanovoids in the ultra-thin selective layer, thus, contributing to higher effective surface area and less hydraulic resistance for improving water permeability. An additional PVA layer was coated atop the liposome-integrated membrane to effectively improve the membrane stability and fouling resistance, leading to a comparable level of salt rejection with the state-of-the-art commercial membranes in treating real seawater, while water permeability was enhanced by 26–185%. This work presents a readily scalable spray-assisted IP technique to fabricate liposome-integrated SWRO membrane for seawater desalination. [Display omitted] • DOPC liposomes were integrated into PA layer via spray-assisted IP approach. • Spraying DOPC liposomes after aqueous phase of IP ensured precise control of liposome amount. • DOPC liposomes resulted in forming a rougher PA surface with larger nanovoids. • The best membrane exhibited 3.24 L/m2·h·bar permeability with 99.3% NaCl rejection. • PVA coated liposome-integrated membrane demonstrated excellent stability and fouling resistance. [ABSTRACT FROM AUTHOR]

Developing a reverse osmosis membrane with desirable water/salt selectivity and boron removal has been recognized as crucial for high-efficient seawater desalination. Herein, fluorinated seawater reverse osmosis (SWRO) membranes were fabricated via fluorine-containing monomers-mediated interfacial polymerization or surface modification by grafting fluorine-containing monomers atop nascent polyamide (PA) layer via a second interfacial reaction. The fluorinated molecules, 5-(trifluoromethyl)-1.3-phenylenediamine (TFPD), 3,5-bis(trifluoromethyl) benzoyl chloride (TFBC) or 2,2,2-trifluoroethylamine (TFEA), were confirmedly integrated into the PA matrix presumably via strong chemical covalent bonds, which manipulated the physicochemical properties of the PA layer, including surface hydrophilicity, pore size distribution, cross-linking degree and interactions between membrane and solutes, thereby producing a high-selectivity thin-film composite (TFC) membrane. The optimized membranes, i.e. , TFC-TFPD, TFC-TFBC and TFC-TFEA, presented significantly excellent separation performance than the control and commercial membrane, both in water/salt selectivity and boron removal capability, accompanied by a comparable water permeance. Among the three proposed incorporation method of fluorinated monomers, direct grafting of TFEA upon the nascent PA layer demonstrates the best efficiency in introducing fluorine elements in the TFC PA membranes, compared to the addition of TFPD and TFBC into aqueous and organic phases during IP process, respectively. The fluorine-incorporated strategy employed in this present work offered a new design of the PA layer containing fluorinated molecules to obtain the desired permselectivity of TFC SWRO membranes towards efficient removal of salt and boron acid in seawater desalination. [Display omitted] • The fluorinated PA-based TFC SWRO membranes were successfully developed. • The fluorine-containing monomers were covalently bonded with PA matrix without sacrificing its integrity. • The incorporation of fluorine elements effectively regulated physicochemical properties of the PA layer. • The in-situ integrated fluorine components enabled high-efficient water/salt selectivity and boron removal. [ABSTRACT FROM AUTHOR]

In this work, we explored the practicability of a nanochannel-based biomimetic membrane (NBM) incorporating pillar[5]arene water channels for seawater reverse osmosis (SWRO) desalination. Two classes of peptide-attached biomimetic channels, (pR)-pillar[5]arenes (pRPH) and (pS)-pillar[5]arenes (pSPH) were integrated into the selective layer of SWRO membranes via interfacial polymerization on the top side of a polysulfone (PSf) support membrane. Here, pSPH is a non-identical stereoisomer of pRPH and was used as a negative control to pRPH to elucidate the flux enhancement effect contributed by pRPH. The optimized NBM presented a water permeability of 2.52 L m-2 h-1 bar-1 and 99.5% rejection under SWRO testing conditions of 50 bar applied pressure and 32,000 mg/L NaCl as feed solution. The 62% permeability increment with reference to the control membrane is hypothesized to originate from hybrid polyamide layers that were rougher with more voids (higher effective surface area and lower hydraulic resistance for water transport) as well as the conceivable water transport pathways provided by the pRPH channels. The simulation results from module-scale modelling suggest that the optimized NBM could lead to 7.2% savings in specific energy consumption of the membrane unit stage (or reduce the required membrane area by 25%) with respect to the commercial SWC4-LD membrane. The performance of the optimized NBM was further assessed in a one-week desalination test using an actual seawater feed gathered from an SWRO plant in Singapore. The robust NBM exhibited stable performance and ∼28% higher water flux (42 L m-2 h-1) than SWC4-LD with a comparable rejection of 99.3%, suggesting the feasibility of pillar[5]arene-based biomimetic membranes for seawater desalination. [Display omitted] • pRPH nanochannel-based biomimetic membrane (NBM) was used for SWRO application. • pRPH channels were incorporated into the PA layer via interfacial polymerization. • High permeability of 2.52 Lm-2h-1bar-1 (99.5% NaCl rejection) was reported in SWRO. • The energy and footprint savings achievable was quantified by module-scale modelling. • The NBM exhibited stable flux in a 7-day desalination test using real seawater. [ABSTRACT FROM AUTHOR]

The addition of co-solvents in aqueous or organic phases of interfacial polymerization is a feasible strategy to tune the performance of aromatic polyamide (PA) thin-film composite (TFC) membrane for brackish water desalination, however, limited progress has been made in developing co-solvent-tailored seawater reverse osmosis (SWRO) membrane. Herein, SWRO membranes were prepared by adding various types of aqueous and organic co-solvents to reveal their impacts on the formation of the PA crumples. It was found that the aqueous/organic co-solvents affected the solubility parameter distance and interfacial tension between two immiscible phases, facilitating the diamine diffusion rate and resulting in a significant change in PA structure. The PA layer with modulated microstructure and varied surface features such as widened void structure, rougher surface, better wettability, and controlled cross-linking degree can be derived from the high interfacial instability that existed between the co-solvent and initial PA film due to the close mutual affinity. Besides, the additional polyvinyl alcohol coating layer atop the PA membrane successfully further enhanced the membrane selectivity. Overall, the mechanistic insights attained in this study revealed the relationship of diamine diffusion, physicochemical properties of PA layer and membrane separation performance for co-solvent-assisted membrane fabrication to render resultant SWRO membrane with more comparable permselectivity. The optimized TFC-SWRO membranes exhibited pure water permeability of 2.2 and 3.2 L m−2 h−1 bar−1 upon the assistance of aqueous and organic co-solvents, respectively, while maintaining excellent NaCl rejection of approximately 99% under seawater desalination tests. [Display omitted] ✓ Aqueous or organic co-solvents were used aiming to flexibly design high-performance SWRO membrane. ✓ The synergistic impacts of solubility parameter and interfacial tension were established to elucidate diamine diffusion behavior. ✓ The relationship of "monomer diffusion - structure property - separation performance" was elaborated. ✓ The formation of a PVA coating layer enhanced the selectivity of co-solvent-assisted SWRO membrane. [ABSTRACT FROM AUTHOR]

Recent research pays much attention to the correlations between structural properties of porous substrate and the separation performance of polyamide (PA) thin film composite (TFC) membrane prepared by interfacial polymerization (IP). However, there are limited studies focused on seawater reverse osmosis (SWRO) membrane preparation and optimization. This study reveals profound impacts of substrate surface properties on the separation properties of SWRO membranes, by using different substrates including commercial ultrafiltration (UF) membrane, lab-scale casted polysulfone (PSF) substrate and pilot-scale casted PSF substrates. We demonstrate that the membrane substrates casted using pilot-scale machine led to better SWRO performance than hydrophilic UF membrane or lab-scale casted substrate; and very different SWRO membranes could be made from pilot-scale substrates casted using the same polymer dope solution. These results showed that a high-performance SWRO membrane relies on appropriate substrate possessing the surface properties of relatively hydrophobic, small surface pore size (20-35 nm) and high surface porosity, which directly affect the supply and transport rate of amine for the IP reaction. Our best SWRO membrane exhibits an excellent NaCl rejection of 99.5% together with high water permeance of 1.72 L m−2 h−1 bar−1 under seawater desalination conditions. This work helps pave the way for substrate selection for SWRO membrane fabrication, narrowing the gap between lab-made and commercial SWRO membranes. [Display omitted] • Substrates with tuned surface properties were used to tailor SWRO membrane performance. • PSF substrates casted by a pilot-scale machine exhibited better SWRO performance. • The best-performing membrane demonstrated water permeance of 1.72 Lm−2h−1bar−1 and rejection of 99.5%. • Hydrophobic substrate of small surface pore size and high surface porosity was important for making excellent SWRO membrane. [ABSTRACT FROM AUTHOR]

Seawater reverse osmosis (SWRO) is the key technology driving an energy-efficient and cost-effective desalination process. At the center of this technology are the thin film composite (TFC) membranes, which not only promise a stable operation but also high separation performances. The objective of this review is to consolidate recent advances in SWRO membranes from the standpoint of membrane materials, fabrication methodologies and applications. First, the thermodynamic limit and energy consumption of SWRO desalination are reviewed, before we discuss the current status of SWRO membranes, highlighting the four main challenges to date – permselective tradeoff, relatively low single-pass boron rejection, membrane fouling and poor chlorine resistance. Thereafter, a comprehensive review of the membrane development is presented. We examine findings reported in research papers and patents, and various methods to achieve SWRO membranes of higher permselectivity, boron rejection, and chlorine resistance as well as lower fouling propensity. Key insights from the membrane industry are also furnished. Then, we put together an outlook, featuring our perspectives on SWRO membrane development. Empirical data in this review are collated into an upper-bound relationship, which is tailored specifically for SWRO membranes and expected to provide benchmarking for future SWRO membrane development. Since the traits of SWRO membranes are unique from those of brackish water RO (BWRO) membranes, we also distinguish the methods used for SWRO membrane fabrication to help zero in on the correct strategies, and provide insights for advancing new membrane designs. Overall, this review sums up the current state-of-the-art SWRO membranes, looking at the array of fabrication methods used thus far, and putting into perspective critical strategies to realize the next-generation TFC membranes that can address the future demands of SWRO and deliver a more competitive desalination process. [Display omitted] • Recent advances in SWRO membrane are collated from papers and industrial patents. • Current status and future outlook of SWRO membrane industry are discussed. • A permselectivity upper bound is established specifically for SWRO membranes. • The upper bound is given by A/B = 46.75 A −1.72 (A/B in bar−1 and A in Lm−2h−1 bar−1). • A roadmap for SWRO membrane fabrication is proposed (short/long-term strategies). [ABSTRACT FROM AUTHOR]