Polymersomes-based high-performance reverse osmosis membrane for desalination (original) (raw)
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A variety of polyamide thin film composite (PA-TFC) membranes was synthesized via interfacial polymerization (IP) technique. IP was carried out between aqueous solution of m-phenylene diamine (MPD) and trimesoyl chloride (TMC) in dodecane as organic solvent onto polysulfone (PSf) supporting membrane. The characterization of synthesized membranes was conducted using attenuated total reflection Fouier transform infrared spectroscopy (ATR-FTIR), scanning electron microscope (SEM) and contact angle measurement. Reverse osmosis performance included permeate flux (L/m2.hr) and salt rejection (%) was evaluated as a function of the synthesis conditions to investigate the optimum conditions that give the best performance membrane. The optimum conditions of synthesized membranes included MPD (1.5 wt.%) for 5 min. soaking time, TMC (0.05 wt. %) in dodecane for 30 sec. reaction time. The best synthesized membrane exhibited high salt rejection (99.81%) with high permeate flux (36.15 L/m2.h). Also, the concentration polarization modulus (M) and the true salt rejection (%) were measured using pure water with different salinities up to ≈ 10000 ppm NaCl feed solution. The obtained results showed that the concentration polarization modulus (M) ranged from 1.06 to 1.29 according to the salinity range.
Innovative Nanostructured Membranes for Reverse Osmosis Water Desalination
University of the Future: Re-Imagining Research and Higher Education
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 ...
Improved membrane structures for seawater desalination by studying the influence of sublayers
Desalination, 2012
This study describes the influence of polyethersulfone (PES) sublayers on the performance of polyamide (PA) reverse osmosis membranes. Asymmetric polymeric sublayers were synthesized by using the DIPS technique (Diffusion Induced Phase Separation). Sublayers are optimized mainly with respect to hydrophilicity, permeability and rejection potential by adjusting synthesis procedures. Parameters that were found to have an influence are the type of solvent (DMF and NMP were used), the air humidity, processing time, and concentrations of polymer. By carefully controlling these parameters, it was possible to prepare a range of sublayers with different characteristics, in the ultrafiltration-nanofiltration area. To visualize membrane surface characteristics, both scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were performed. In addition, titanium (TiO 2 ) nanoparticles were assembled with polyethersulfone (PES) membranes at ultralow concentrations of nanoparticles to characterize TiO 2 /PES composite membranes and evaluate their permeate flux and solute rejection. Subsequently, a polyamide top layer was added by interfacial polymerization using typical reagents both in the aqueous and in the organic phase. The membrane performance was evaluated in terms of flux and salt rejection. Experimental design was performed in order to obtain the importance of some experimental variables during the polymerisation process. It was found that depending on the type of sublayer used in the procedure, a different membrane performance could be obtained.
The objective of this work was to develop a suitable and highly efficient reverse osmosis membrane incorporating a co-solvent system. A polyamide thin-film composite membrane has been prepared by interfacial polymerization in n-heptane using diethyl ether and ethyl acetate as co-solvents at various concentrations. Heptane has a molecule of larger C-C chain than that of traditionally used hexane. Heptane was selected in order to study its effect on the morphology of the prepared membrane as well as on salt rejection ability and flux volume. Heptane appeared to produce an improved morphology, salt rejection ability, and flux volume, compared to hexane. To the best of our knowledge, this is the first attempt to prepare and characterize TFC RO membrane in n-heptane mixed with co-solvent. The membranes were characterized using microscopy, spectroscopy, and contact angle measurement techniques. From surface spectroscopic analyses, the addition of co-solvents led to a decrease in the roughness properties of the membranes. The synthesized polyamide membranes consist of large and ordinal ridgeand-valley formations. The salt rejection and water permeate flux were well controlled by the categories and amounts of co-solvents that were added. Thermal gravimetric analysis results indicated that all of the membranes exhibited high thermal stability with degradation temperatures of about 481 ± 2˚C. The high stability of the membranes was attributed to the sulfonic groups on the polymer chains. The contact angle also increased with an increasing co-solvent concentration. The performance characteristics of the membranes were evaluated by measuring the flux and rejection of isopropyl alcohol, NaCl, and MgCl 2 solutions. The rate of flux was proportional to the co-solvent concentration (i.e. flux increases with an increasing concentration), whereas the salt rejection properties were constantly high. Membranes formed with diethyl ether showed the highest salt rejection. Based on these data, membranes prepared using diethyl ether or ethyl acetate as a co-solvent in a non-polar heptane medium performed efficiently and exhibited high salt rejection characteristics with large flux values. These membranes represent promising candidates for freshwater desalination and removal of organic impurities.
Desalination, 2012
The present paper describes the synthesis of poly sulphonyl amino benzamide (PSAB) and methyalated poly sulphonyl amino benzamide (mPSAB) polymer, using terephthalic acid chloride and substituted 4-amino-1-benzensulphonmide in N-methyl-2-pyrrolidone. Polymers were characterized by FT-IR, NMR and GPC. Polysulfone composite membranes were prepared using these novel poymers by DIPS (Diffusion Induced Phase Seperation) method. These composite membranes are useful for water purification with special emphasis on sea water desalination. Newly prepared membranes were studied for salt rejection, water flux, molecular weight cut off by PEG solution, effect of the pH on water swelling and salt rejection and flux decline was also studied. 30 to 70% of the salt rejection was observed in all membranes. Effect of the dilution on salt rejection was studied using different concentration of NaCl solution varying from 1000 ppm to 3500 ppm. All the membranes showed 80% rejection for PEG having 1000 Da molecular weight. Contact angle and water swelling was measured to determine hydrophilicity of the membrane. Water swelling and salt rejection in different pH was also studied.
Membranes, 2019
For the fulfilment of increasing global demand and associated challenges related to the supply of clean-and-safe water, PV has been considered as one of the most attractive and promising areas in desalinating salty-water of varied salinities. In pervaporative desalination, the sustainability, endurance, and structural features of membrane, along with operating parameters, play the dominant roles and impart paramount impact in governing the overall PV efficiency. Indeed, polymeric- and organic-membranes suffer from several drawbacks, including inferior structural stability and durability, whereas the fabrication of purely inorganic membranes is complicated and costly. Therefore, recent development on the high-performance and cost-friendly PV membrane is mostly concentrated on synthesizing composite- and NCP-membranes possessing the advantages of both organic- and inorganic-membranes. This review reflects the insights into the physicochemical properties and fabrication approaches of d...
Journal of Membrane Science, 2020
State-of-the-art desalination and water purification processes use reverse osmosis and nanofiltration membranes. Their thin polyamide (PA) top-layers ensure concurrent high water permeances and salt rejections, but are also intrinsically sensitive to chlorine, originating from disinfectant added upstream. The chlorine resistance of PA-based membranes has been thoroughly studied at lab-scale, as opposed to industrial-scale membrane modules, where fundamental studies are lacking. Therefore, to better understand chlorine-induced changes in membrane performance and physicochemical properties at industrial scale, chlorination of commercial 8" elements was conducted at different pH (4-7-10) in pressurized modules with low chlorine concentrations (0, 1, 20, 50 ppm NaOCl) during 2.5 h. After 50 ppm acidic chlorination, water permeability decreased (-40%) but salt rejection increased significantly (+0.4%, i.e., salt passage decreased with-78.8%). Boron (+27%) and isopropanol (+8%) rejection also increased. Chlorination with 20 ppm NaOCl at pH 7 and with 50 ppm NaOCl at pH 10 caused boron rejection to drop with-17% and-33%, respectively, but had negligible influence on isopropanol rejection. However, neutral and alkaline chlorination drastically improved water permeability with +40% and salt rejection with +0.6% (i.e., salt passage decreased with-66.9%), approaching and in some cases even slightly exceeding the salt/water permselectivity limit. It can thus be concluded that, under controlled conditions, chlorination can boost the performance of membrane modules. Significant changes in the membrane physicochemical properties were observed at pH 4. At pH 7 and pH 10, a low chlorine-uptake in the PA network was observed, although no significant PA deterioration was observed with XPS and ATR-FTIR. This study is the first to fundamentally investigate chlorination of PA-based realscale membrane modules as a function of feed pH. Furthermore, it provides a promising strategy to boost membrane performance at real scale and highlights the importance of chlorination conditions. 2. Table Of Contents 2 3. Introduction Water treatment and desalination allow access to unconventional water sources and the (re-)use of contaminated waters for domestic and industrial consumption [1]. Water purification is hence an energy-efficient solution to overcome water scarcity, one of the major sustainable development goals of the United Nations [2]. State-of-the-art nanofiltration (NF) and reverse osmosis (RO) membranes have a polyamide (PA) top-layer, synthesized through the interfacial reaction of m-phenylene diamine (MPD) and trimesoyl chloride (TMC), that ensures excellent salt rejection and water permeance [3]. However, some micro-pollutants, such as endocrine disruptive compounds (EDCs), perfluoroalkyl substances (PFAs) and pharmaceutically active compounds (PhACs) are only poorly rejected and may cause health threats [4-7]. Another poorly rejected species is boron, typically found as boric acid at 4.5 mg L-1 in sea water [8]. As boron can also have adverse effects on human, animal and plant health, the World Health Organization (WHO) recommends a boron concentration of 2.4 mg/L for drinking water [9]. For agricultural irrigation, boron concentration should ideally be lower than 0.3 mg L-1 [10]. However, as current commercially available RO membranes exhibit boron rejections below 90%, a single-pass RO process does not meet the regulatory guidelines for water sources with high boron content [11]. The low boron rejection of PA-based RO membranes is mainly caused by the small and uncharged nature of boric acid (pKa ~ 8.6-9.2) under operating conditions (< pH 8), impairing rejection mechanisms based on ion exclusion [12]. Additionally, hydrogen bonding between water and boric acid can possibly drag boric acid through the membrane [13]. To achieve low enough boron concentrations in permeates, membranes with improved rejection of small and uncharged species, as well as innovative desalination process designs are actively investigated [7,12,14-17]. Another drawback of PA-based membranes is their sensitivity to chlorine, originating from disinfectant added upstream of the membrane filtration unit to minimize bio-fouling [18]. To avoid PA chlorination, chlorine removal is executed by dosing sodium metabisulfite or sodium bisulfite to the feed water in the so-called dechlorination step. However, complete continuous chlorine removal sometimes fails because of various practical factors, such as imperfect mixing of the chlorine-quencher, dechlorination system upsets and indirect monitoring of chlorine residuals. When this happens, accidental chlorination of the PA membrane takes place [18-21]. Chlorine, often dosed as sodium hypochlorite (NaOCl), will attack the PA network in various ways, depending on, amongst others, the pH of the feed solution and the presence of other ions [18]. Under acidic conditions, chlorine reacts through N-chlorination of the amide bond, and direct or indirect ring-chlorination of the aromatic MPD moieties inside the PA network. In alkaline environments, chlorination-promoted hydrolysis takes place, causing cleavage of the amide
Development of novel thin film composite reverse osmosis membranes for desalination
PROCEEDINGS OF THE 2ND INTERNATIONAL CONFERENCE ON BIOSCIENCES AND MEDICAL ENGINEERING (ICBME2019): Towards innovative research and cross-disciplinary collaborations
Microporous Polyetherimide (PEI) membranes were prepared by wet phase inversion at different temperatures. The thin film composites (TFC) of polyamide on microporous PEI were prepared using meta-Phenylenediamine (MPD) and 1,3,5-Benzenetricarbonyl chloride (BTC). The ATR FTIR characterization showed the formation of polyamide (PA) on microporous PEI membrane, whereas scanning electron microscopy (SEM) revealed that a thin film of polyamide is formed on microporous PEI. The cross-sectional SEM of PEI prepared at 60 °C, showed finger like morphology and sparingly distributed balloon like morphology for PEI synthesized at 80 °C. The performance of PEI membranes and PA TFCs were ascertained by studying permeation of water and rejection of sodium chloride by reverse osmosis. The polyamide TFC with hydrophobic PEI support structures exhibited permeation of 28 to 50 lm-2h-1, with 98-95 % 2000 ppm NaCl rejection at 60 bar pressure.
Forward osmosis (FO) is a promising alternative to reverse osmosis (RO) in membrane-based water desalination. In the current study, carboxylated multiwalled carbon nanotubes (MWCNTs) were incorporated in a polyamide (PA) layer formed on top of a polysulfone porous support, resulting in a thin film nanocomposite (TFN) membrane. The amount of MWCNTs was varied (0.01, 0.05, 0.1, and 0.2 wt/vol %). The FO performance was investigated using deionized water as the feed solution and 2 M NaCl as the draw solution. It was found that the carboxylated MWCNTs enhanced the membrane hydrophilicity, surface roughness, and porosity. Such combined effects are believed to have led to enhanced FO water flux. TFN 0.2 showed the highest FO water flux of 73.15 L/m 2 h, an improvement of 67% compared to the blank thin-film composite (TFC) membrane and significantly better than the values reported in the literature. Direct observation by transmission electron microscopy revealed the presence of some open-ended CNTs favorably oriented across the PA layer. Those are believed to have facilitated the transport of water through their inner cores and contributed to the increase in water flux. However, this was at the expense of salt rejection and reverse solute flux performance. The best performing membrane was found to be TFN 0.01. It exhibited a salt rejection of 90.1% with a FO water flux of 50.23 L/m 2 h, which is 13% higher than the TFC membrane, and a reverse solute flux of 2.76 g/m 2 h, which is 21% lower than the TFC membrane. This TFN 0.01 membrane also outperformed the TFN membranes reported in the literature.
Applied Surface Science, 2005
Ultrathin, multilayered membranes of polyvinylamine (PVA) and polyvinylsulfate (PVS) were electrostatically adsorbed on a porous polymer (polyacrylonitrile/polyethylene terephthalate) support. Their use for desalination of aqueous salt solutions, diluted and non-diluted artificial seawater was investigated under reverse osmosis conditions. Using 60 layer pairs of PVA/PVS as separating membrane, it was possible to completely reject MgCl 2 and MgSO 4 from feed solutions of 1 and 10 mM concentration independently from the operative pressure applied. The rejection of NaCl and Na 2 SO 4 increased from 84 and 96% at 5 bar to 93.5 and 98.5% at 40 bar, respectively. From diluted seawater (1:10; 1:100; 1:1000), 99 AE 1% of Mg 2+ , 97.0 AE 1% of Ca 2+ , and 92.5 AE 1% of Na + were rejected at 40 bar, and from non-diluted seawater, 98 AE 1% of Mg 2+ , 96.4 AE 1% of Ca 2+ , and 74.5 AE 0.8% of Na + were rejected at 40 bar. The permeation flux J increased linearly with the pressure applied. For a membrane of 60 PVA/PVS layer pairs, a flux value of 4 AE 0.2 L m À2 h À1 was found at 40 bar. The influence of the number of deposited layer pairs on R and J was also investigated. #