Thin Film Composite Membranes for Forward Osmosis Supported by Commercial Nanofiber Nonwovens (original) (raw)
Related papers
Drinking Water Engineering and Science
The forward osmosis (FO) process has been considered to be a viable option for water desalination in comparison to the traditional processes like reverse osmosis, regarding energy consumption and economical operation. In this work, a polyacrylonitrile (PAN) nanofiber support layer was prepared using the electrospinning process as a modern method. Then, an interfacial polymerization reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) was carried out to generate a polyamide selective thin-film composite (TFC) membrane on the support layer. The TFC membrane was tested in FO mode (feed solution facing the active layer) using the standard methodology and compared to a commercially available cellulose triacetate membrane (CTA). The synthesized membrane showed a high performance in terms of water flux (16 Lm −2 h −1) but traded the salt rejection (4 gm −2 h −1) compared with the commercial CTA membrane (water flux = 13 Lm −2 h −1 and salt rejection = 3 gm −2 h −1) at no applied pressure and room temperature. Scanning electron microscopy (SEM), contact angle, mechanical properties, porosity, and performance characterizations were conducted to examine the membrane.
Desalination, 2018
This work investigated the influence of a new polymeric blend of polysulfone/polyacrylonitrile (PSf/PAN) nanofibers prepared via the electrospinning process as substrate to produce thin film composite forward osmosis (TFC-FO) membrane. The solvents in the electrospinning process were optimized. A polyamide (PA) thin layer was successfully fabricated on the electrospun nanofibrous substrate via interfacial polymerization. The performance of the nanofiber-based thin film composite (NTFC) membranes was compared with the in-house-made (PSf/PAN) TFC membrane, in which its substrate was fabricated by phase inversion. The NTFC membrane demonstrated significant improvement in hydrophilicity and water permeability, and the reverse salt flux (RSF) was reduced. In addition, the structural parameter (S) value of the fabricated NTFC decreased considerably which represented the reduction of internal concentration polarization (ICP) during the FO process. These achieved results were due to nanofiber structural characteristics such as high porosity and interconnected open pore structure. The effects of different salts as draw solutions (NaCl, KCl, MgCl 2 , MgSO 4) on the osmotic performance of the NTFC and TFC membranes were evaluated. Among the tested draw solutions with the same osmotic pressure, the NTFC membrane exhibited higher water flux (38.3 LMH) than that of the TFC membrane (14.3 LMH) for KCl draw solution.
Keywords Highlights A Review of Electrospun Nanofiber Membranes Article info
Electrospun nanofiber membranes Water treatment Adsorptive membranes Membrane distillation Desalination • A new generation of membranes offering higher flux at lower applied pressure • Highly porous with interconnected pores • High specific surface area, suitable for adsorption applications • Have found applications in water treatment, air cleaning, membrane distillation, among many other uses Electrospun nanofiber membranes (ENMs) are new generation of membranes with many favorable properties such as high flux and low pressure drop. Although electrospinning has been known for more than a century, its applications in filtration and separation processes are relatively new. Electrospinning has provided the means to produce ultrathin fibers -as thin as a few nanometers -that can be used in preparing membranes with small and defined pore sizes. In addition, due to the small fiber diameter ENMs exhibit high surface area to volume ratio, making them suitable adsorption media with enhanced capacity compared with conventional adsorbents. This paper familiarizes the reader with the history and laboratory-scale preparation of ENMs, discusses parameters that influence properties of the fibers and the final membranes, and introduces a number of applications in which, ENMs have exhibited superior performances compared to competing conventional processes.
Fabrication of high-performance nanofiber-based FO membranes
DESALINATION AND WATER TREATMENT, 2019
Being partially commercialized and has specific application areas, where the reverse osmosis technology cannot serve, forward osmosis (FO) technology is continually receiving extensive research to promote its performance. In this study, high-performance FO nanofiber-based substrate membrane was fabricated for potential application of saline water desalination. Sulfonated polysulfone (sPSU) with definite sulfonation level was used to fabricate support layer. Tubular beadless fiber network owning scaffold-like structure with a fiber diameter of 247 nm was formed. Polysulfone was sulfonated by heterogeneous method using chlorosulfonic acid as a sulfonation agent. The substrate and FO membranes were characterized mainly by means of scanning electron microscopy (SEM), water permeation flux, porometry, contact angle, Fourier transform infrared (FTIR), as well as other tests, while the characterization of thin-film composite separation layer was restricted to SEM and FTIR. The characterization illustrates that the sPSU support layer is highly porous with a narrow pore size distribution. FO performance evaluation of two commercial and newly developed membranes was probed using FO and pressure-retarded osmosis (PRO) modes with cocurrent and counter-current flow scheme. The active layer presents excellent intrinsic properties with A/B of 17.31 and a high salt separation ratio of 99.54%. The newly developed membrane can achieve a high FO and PRO water flux of 65.7 and 313 L m −2 h −1 , respectively, using a 1 M NaCl draw solution and deionized water feed solution. The corresponding salt flux is only 2.5 and 5.3 g m −2 h −1. The reverse flux selectivity represented by the ratio of water flux to reverse salt flux (J w /J s) was kept as high as 26.3 and 58.8 L g-1 for FO and PRO modes. To the best of our knowledge, the performance of the current work-developed membrane is superior to all FO membranes previously reported in the literature.
Forward osmosis (FO) process has been considered as a viable option for water desalination in comparison to the traditional processes like reverse osmosis regarding the energy consumption and economical operation. In this work, polyacrylonitrile (PAN) nanofiber support layer was prepared using electrospinning process as a modern method. Then, an interfacial polymerization reaction between mphenylenediamine (MPD) and trimesoyl chloride (TMC) was carried out to generate a polyamide selective thin film composite (TFC) membrane on the support layer. The TFC membrane was tested in FO mode (feed solution facing the active layer) using standard methodology and compared to a commercially available cellulose triacetate membrane (CTA). The synthesized membrane showed a high performance in terms of water flux (16 Lm-2 h-1) but traded the salt rejection (4 gm-2 h-1) comparing with the commercially CTA membrane (water flux= 13 Lm-2 h-1 and salt rejection= 3 gm-2 h-1) at no applied pressure and room temperature. Scanning electron microscopy (SEM), contact angle, mechanical properties, porosity, and performance characterizations were conducted to examine the membrane.
2013
Engineered osmosis (EO) is a state-of-the-art technology which harnesses the natural phenomenon of osmosis to address global issues related to water and energy. In this process, an osmotic pressure drives water across a semi-permeable membrane from a dilute feed solution to a concentrated draw solution. EO has the potential to sustainably produce fresh water at low energy cost, generate electricity and recover high-value dissolved solids. However, EO has not progressed beyond conceptualization and lab scale studies due to obstacles in membrane design, draw solution recovery, system integration, scale-up, and definitive process economics. This study focuses on addressing the primary obstacle to EO development: the lack of adequately designed membrane. Departing from traditional design of polyamide composite membrane, this dissertation presents one of the first known studies in which a novel thin-film composite/nanocomposite membrane supported on an effective nanofibrous structure was tailored for EO applications. With the integration of nanotechnology and membrane science, this membrane design shows immense promise as a next generation membrane platform for EO. Furthermore, this work shed insight on the critical structureperformance relationships with respect to mass transfer models for further advancing membrane design and EO development. It will eventually lead to widespread adoption of this emerging technology platform in sustainable waterenergy production and life sciences.
Nanofiber composite membranes with low equivalent weight perfluorosulfonic acid polymers
Journal of Materials Chemistry, 2010
Two low equivalent weight perfluorosulfonic acid (PFSA) polymers (825 EW and 733 EW) were successfully electrospun into nanofibers by adding as little as 0.3 wt% of high molecular weight poly(ethylene oxide) as a carrier polymer. The electrospun fiber morphology transitioned from cylindrical filaments to flat ribbons as the total concentration of PFSA + carrier in solution increased from 5 wt% to 30 wt%. PFSA nanofiber mats were transformed into defect-free dense membranes using a four-step procedure: (i) annealing the PFSA polymer during which time intersecting fibers were welded to one another at cross points (ii) mechanically compacting the mats to increase the volume fraction of nanofibers to $75%, (iii) imbibing an inert polymer, Norland Optical Adhesive (NOA) 63, into the mats (to fill entirely the void space between nanofibers) and then crosslinking the NOA with UV light, and (iv) removing the poly(ethylene oxide) carrier polymer by boiling the membrane in 1.0 M H 2 SO 4 and then in deionized water. The resulting membranes exhibited higher proton conductivities than that of commercial Nafion 212 membrane (0.16 S/cm at 80 C and 80% relative humidity and 0.048 S/cm at 80 C and 50% relative humidity for a membrane with 733 EW nanofibers), with low water swelling (liquid water swelling of 18% for membrane with high conductivity). The proton conductivity of both EW nanofiber composite membranes increased linearly with the PFSA nanofiber volume fraction, whereas gravimetric water swelling was less than expected, based on the volume fraction of ionomer. There was a significantly improvement in the mechanical properties of the nanofiber composite membranes, as compared to recast homogeneous PFSA films.
A Review of Electrospun Nanofiber Membranes
2017
Electrospun nanofiber membranes Water treatment Adsorptive membranes Membrane distillation Desalination • A new generation of membranes offering higher flux at lower applied pressure • Highly porous with interconnected pores • High specific surface area, suitable for adsorption applications • Have found applications in water treatment, air cleaning, membrane distillation, among many other uses
Journal of Membrane Science, 2016
Nanofibers fabricated with electrospinning method have several prominent properties such as high specific surface area, high porosity and uniform pore size distribution in nanoscale or microscale. These unique features are vital for separation processes in water and wastewater treatment applications. In this study, we have developed a new type of nanofiber electrospun membrane for the first time by collecting nanofibers on a hollow braided rope. The nanofiber membranes were characterized with Scanning Electron Microscope images, pore size, contact angle and porosity measurements. Filtration performances of tubular nanofiber and a commercial hollow braided reinforced membrane were determined for both standard particle solutions and surface water under low vacuum pressures. The novel tubular nanofiber (TuEN) membranes exhibited high water fluxes in even low vacuum pressures, relatively high removal efficiencies of turbidity (% 95), total organic carbon (29 %) and UV 254 (45%) compared to other microfiltration membranes. We claim that the tubular nanofiber membrane will attract more attention in coming years in the fields of water and wastewater treatment.