Engineered Osmosis for Sustainable Water and Energy: Novel Nanofiber-supported Thin-film Composite Membrane Design & Updated Flux Model Proposal (original) (raw)
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Thin Film Composite Membranes for Forward Osmosis Supported by Commercial Nanofiber Nonwovens
Industrial & Engineering Chemistry Research, 2017
Nanofiber supported thin film composite (TFC) for forward osmosis (FO) have shown great promise as a viable FO membrane in comparison to commercially available forward osmosis membranes. In numerous studies on the subject, nanofiber supports for TFC membranes are commonly made by electrospinning. In this study, we have chosen a different nanofiber medium to use as a support for a FO TFC membrane. This nonwoven, which is a commercially available, nanofiber mats from E.I. duPont de Nemours company (DuPont). This unique nanofiber based nonwoven is produced as long rolls and is unsupported, unlike other nanofiber products that are produced on top a typical spunbond or wetlaid nonwoven due to the lack of mechanical integrity. The DuPont PES materials demonstrated better strength than typical electrospun materials and was used to support a polyamide selective layer formed by in-situ interfacial polymerization. The Dupont PES TFC membrane was tested in FO and found to generate twice the water flux and one-tenth the reverse solute flux compared to a commercial TFC FO membrane. The membrane was also found to match performance of laboratory based electrospun nanofiber supported TFC, but exhibited better selectivity and strength.
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.
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.
Polymers
The commercial thin-film composite (TFC) nanofiltration (NF) membrane is unsuitable for engineered osmosis processes because of its thick non-woven fabric and semi-hydrophilic substrate that could lead to severe internal concentration polarization (ICP). Hence, we fabricated a new type of NF-like TFC membrane using a hydrophilic coated polyacrylonitrile/polyphenylsulfone (PAN/PPSU) substrate in the absence of non-woven fabric, aiming to improve membrane performance for water and wastewater treatment via the engineered osmosis process. Our results showed that the substrate made of a PAN/PPSU weight ratio of 1:5 could produce the TFC membrane with the highest water flux and divalent salt rejection compared to the membranes made of different PAN/PPSU substrates owing to the relatively good compatibility between PAN and PPSU at this ratio. The water flux of the TFC membrane was further improved without compromising salt rejection upon the introduction of a hydrophilic polydopamine (PDA)...
Desalination, 2020
Recently, forward osmosis (FO) has attracted a great deal of attention in desalination and wastewater treatment. Nevertheless, there are several critical challenges such as the need for new advances in designing membranes that must be met to enhance the water flux in FO processes, control the reverse salt flux, concentration polarization and fouling. Therefore, designing a suitable membrane with a high-water flux, low reverse salt flux, low fouling, and controlled concentration polarization seems to be essential. Thin film composite (TFC) membranes are the most widely used membranes in the FO field. Extensive research has been performed to fabricate and design high performance TFC membranes which can be exclusively used in FO processes. This paper aims to review three types of TFC membranes i.e. TFC's with polyamide active layer (TFC-A), thin film nanocomposites (TFC-N) and double-skinned TFC membranes (TFC-D) in flat sheet and hollow fiber configuration. Finally, an attempt is made to generate a general performance curve based on the water flux and reverse salt flux of these three TFC FO types and the future direction of the R and D on the FO membrane are discussed.
Journal of Membrane Science, 2011
Osmotically driven membrane processes have the potential to treat impaired water sources, desalinate sea/brackish waters, and sustainably produce energy. The development of a membrane tailored for these processes is essential to advance the technology to the point that it is commercially viable. Here, a systematic investigation of the influence of thin-film composite membrane support layer structure on forward osmosis performance is conducted. The membranes consist of a selective polyamide active layer formed by interfacial polymerization on top of a polysulfone support layer fabricated by phase separation. By systematically varying the conditions used during the casting of the polysulfone layer, an array of support layers with differing structures was produced. The role that solvent quality, dope polymer concentration, fabric layer wetting, and casting blade gate height play in the support layer structure formation was investigated. Using a 1 M NaCl draw solution and a deionized water feed, water fluxes ranging from 4 to 25 L m −2 h −1 with consistently high salt rejection (>95.5%) were produced. The relationship between membrane structure and performance was analyzed. This study confirms the hypothesis that the optimal forward osmosis membrane consists of a mixed-structure support layer, where a thin sponge-like layer sits on top of highly porous macrovoids. Both the active layer transport properties and the support layer structural characteristics need to be optimized in order to fabricate a high performance forward osmosis membrane.
2015
Novel and promising forward osmosis (FO) is a membrane-based separation with significant potentials for the desalination process. While this technology offers various benefits, overcoming its internal concentration polarization (ICP) and membrane fouling in polyamide (PA) skin layer remain as a challenge. In this study, three types of novel thin film nanocomposite (TFN) membranes were synthesized by either coating a typical PA film over the surface of substrate made of polysulfonehalloysite nanotubes (HNTs) or embedding HNTs and titanium dioxide (TiO2)/HNTs nanocomposites into PA thin layer formed over a typical polysulfone (PSF) substrate. These approaches aim to reduce membrane fouling and/or ICP during FO applications. In the first stage of this study, both hydrophilicity and porosity of the substrate were increased using HNTs. The results obtained from filtration experiments showed that the TFN membrane prepared with incorporation of 0.5 wt% HNTs (TFN 0.5) demonstrated the most ...
DESALINATION AND WATER TREATMENT
The performance evaluation of forward osmosis (FO) nanofibers based membranes against model solutions and real seawater were investigated. The desalination of seawater performed using 2 M NaCl as a draw solution. Performance data showed that when real seawater used as a feed solution, the newly fabricated FO membrane has a water flux of 15.1 and 49.4 LMH in both co-current FO and co-current pressure retard mode (PRO) respectively. Two different model solutions (NaCl and MgSO 4), have a salt concentration equal to that of the real seawater sample, were prepared to characterize the performance of the fabricated membrane against them under the same operating conditions. The flux obtained in 1.1% model NaCl in FO mode was 8 LMH, whereas in PRO mode was 54 LMH and 10.3 LMH in FO mode, whereas 45.6 LMH in PRO mode for model 1.1% MgSO 4 solution using 2 M NaCl solution as a draw solution. The structural parameter (S-value) of the sulfonated polysulfone (sPSf) thin-film-composite membrane is estimated to be 125 µm, which is considered one of the smallest values ever reported in the literature. In this manuscript, the performance study of thin-film composite (TFC-FO) nanofiber flat-sheet membrane on sPSf substrate is proven that fabricated membranes are perfectly meet the high rejection ratios whether strong enough to sustain high flux and durability through the operation.