Fabrication of fullerenol-incorporated thin-film nanocomposite forward osmosis membranes for improved desalination performances

Development and use of novel membranes for forward osmosis (FO) applications have gained popularity throughout the world. To enhance FO membrane performance, a novel thin-film nanocomposite membrane was fabricated by interfacial polymerization incorporating Fullerenol (C₆₀(OH)_n) nanomaterial, having n in the range of 24–28 into the active layer. Different concentrations of fullerenol loading (100, 200, 400, and 800 ppm) were added to the top skin layer. The structural and surface properties of the pure thin-film composite membrane (TFC) and fullerenol-incorporated thin-film nanocomposite (FTFC) membranes, were characterized by ATR-FTIR, SEM, and AFM. FO performance and separation properties were evaluated in terms of water flux, reverse salt flux, antifouling propensity, water permeability and salt permeability for all TFC and FTFC membranes. Osmotic performance tests showed that FTFC membranes achieved higher water flux and reverse salt flux selectivity compared with those of TFC membranes. The FTFC membrane with a fullerenol loading of 400 ppm exhibited a water flux of 26.1 L m^?2 h^?1 (LMH), which is 83.03% higher than that of the TFC membrane with a specific reverse salt flux of 0.18 g/L using 1 M sodium chloride draw solution against deionized water in FO mode. The fullerenol incorporation in FTFC membranes also contributed to a decreased fouling propensity.     

Effect of cellulose triacetate membrane thickness on forward‐osmosis performance and application for spent electroless nickel plating baths

Cellulose triacetate (CTA) forward‐osmosis (FO) membranes were prepared via the phase inversion method. The influence of thickness on the performance and morphology of CTA FO membranes was discussed in detail. When the thickness of the membrane was 50.0 ± 0.5 μm (CTA4), the prototype CTA membranes displayed a water flux of 20.2 L m^?2 h^?1 and a reverse salt transport of 14.6 g m^?2 h^?1 using 1 mol/L NaCl as the draw solution and deionized water as the feed solution during the FO process at 25 °C. In addition, the high‐performance CTA4 FO membranes have been used to process spent electroless nickel plating baths where the water flux could reach 13 L m^?2 h^?1 and NiSO₄·6H₂O crystals occurred in the feed solution of the spent electroless nickel plating baths. The recovery rates of NiSO₄·6H₂O and water from the spent electroless nickel plating baths were 44.54% and 53.53%, respectively. This study focused on improving membrane design for the FO process and finding a new method of waste liquor or wastewater treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45049.     

Engineering design of outer‐selective tribore hollow fiber membranes for forward osmosis and oil‐water separation

Outer‐selective thin‐film composite (TFC) hollow fiber membranes offer advantages like less fiber blockage in the feed stream and high packing density for industrial applications. However, outer‐selective TFC hollow fiber membranes are rarely commercially available due to the lack of effective ways to remove residual reactants from fiber's outer surface during interfacial polymerization and form a defect‐free polyamide film. A new simplified method to fabricate outer‐selective TFC membranes on tribore hollow fiber substrates is reported. Mechanically robust tribore hollow fiber substrates containing three circular‐sector channels were first prepared by spinning a P84/ethylene glycol mixed dope solution with delayed demixing at the fiber lumen. The thin wall tribore hollow fibers have a large pure water permeability up to 300 L m^?2 h^?1 bar^?1. Outer‐selective TFC tribore hollow fiber membranes were then fabricated by interfacial polymerization with the aid of vacuum sucking to ensure the TFC layer well‐attached to the substrate. Under forward osmosis studies, the TFC tribore hollow fiber membrane exhibits a good water flux and a small flux difference between active‐to‐draw (i.e., the active layer facing the draw solution) and active‐to‐feed (i.e., the active layer facing the feed solution) modes due to the small internal concentration polarization. A hyperbranched polyglycerol was further grafted on top of the newly developed TFC tribore hollow fiber membranes for oily wastewater treatment. The membrane displays low fouling propensity and can fully recover its water flux after a simple 20‐min water wash at 0.5 bar from its lumen side, which makes the membrane preferentially suitable for oil‐water separation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4491–4501, 2015     

High Flux Layer by Layer Polyelectrolyte FO Membrane: Toward Enhanced Performance for Osmotic Microbial Fuel Cell

Combination of microbial fuel cell (MFC) and forward osmosis (FO) is called an osmotic microbial fuel cell (OMFC). Because of the high cost of FO membranes, for the first time laboratory made FO membrane has been used in OMFC. This study investigates the performance of FO membrane in OMFC treating glucose as substrate and 2M NaCl as draw solution. The FO membrane was able to achieve 18.43 lm^?2 h^?1 (LMH) and for fouled FO membrane it was 15.26 lm^?2 h^?1. The OMFC constantly produced bioelectricity and achieved maximum current density 139.52 A/m³ and power density 27.38 W/m³. The energy production of OMFC was 0.438 kWh/m³.     

Synthesis and characterization of PVC-TFC hollow fibers for forward osmosis application

Forward osmosis (FO) is considered among the most encouraging water desalination processes as a result of its high performance and low energy demand. Thin-film composite (TFC) hollow fibers (HF) were synthesized and examined in the FO process. Three different concentrations of polyvinyl chloride (PVC) support polymer were fabricated via the phase inversion technique. The polyamide layer was synthesized on the outer surface of the PVC-HF substrate via interfacial polymerization (IP) reaction. To the best of our knowledge, PVC HF was used in this research for the first time as a support for TFC-FO membranes. PVC HFs have high-quality specifications that are expected to have outstanding performance in TFC-FO applications, especially for water desalination. The obtained membranes were characterized using contact angle measurement, scanning electron microscopy, atomic force microscope and Fourier-transform Infrared. The performance of the PVC-TFC HF was examined in the FO under standard conditions. Results showed that the membrane fabricated with a lower concentration of PVC substrate exhibited higher water flux in comparison to the higher concentration PVC membrane. Changing the concentration of PVC from 15% to 18% reduced water flux from 25 to 13 L m⁻² h⁻¹; however, salt flux also decreased from 8 to 3 g m⁻² h⁻¹.     

Novel carboxyethyl amine sodium salts as draw solutes with superior forward osmosis performance

A series of carboxyethyl amine sodium salts (CASSs) with different carboxyl group numbers are synthesized as draw solutes for forward osmosis (FO) application. Their chemical structures are examined by ¹HNMR and HRMS. FO performances are investigated and compared in terms of different physicochemical properties. The effects of the CASS concentration on the osmotic pressure and viscosity of the draw solutions, as well as the resulted FO performance are also systematically investigated. A high water flux of 23.07 LMH and an acceptable reverse salt flux of 0.75 gMH can be achieved with 0.5 g mL^?1 triethylenetetramine hexapropionic acid sodium (TTHP‐Na) draw solution under PRO mode, which is superior to most other draw solutes reported in previous literatures. TTHP‐Na draw solution is further evaluated to recycle the Congo red solution via FO process to examine its applicability for waste water treatment. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1226–1235, 2016     

Poly(ethylene glycol) crosslinked sulfonated polysulfone composite membranes for forward osmosis

Forward osmosis (FO) membranes were prepared by a coating method with poly(ethylene glycol) crosslinked sulfonated polysulfone (SPSf) as a selective layer. The poly(ether sulfone)/SPSf substrate was prepared by phase inversion. The composite membranes were characterized with respect to membrane chemistry (by attenuated total reflectance/Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy), hydrophilicity (by static contact angle measurement), and surface morphology (by scanning electron microscopy and atomic force microscopy). The FO performance was also characterized. The effects of the crosslinker concentration on the hydrophilicity and FO performance were investigated. The crosslinked membrane exhibited a high hydrophilicity with a lowest contact angle of 15.5°. Under FO tests, the membranes achieved a higher water flux of 15.2 L m^?2 h^?1 when used against deionized water as the feed solution and a 2 mol/L sodium chloride (NaCl) solution as the the draw solution. The membranes achieved a magnesium sulfate rejection of 96% and an NaCl rejection of 55% when used against a 1 g/L inorganic salt solution as the feed solution and a 2 mol/L glucose solution as the draw solution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43941.     

Inhibiting the concentration polarization of FO membranes based on the wettable microporous supporting layer and the enhanced dense skin layer

A novel thin film composite‐type forward osmosis (FO) membrane with inhibited concentration polarization phenomenon and expectant separation performance was prepared by continuous interfacial polymerization method. The nylon‐6,6 microfiltration membrane with the average pore size of 5 μm and the self‐wetting property was for the first time used as the supporting layer of the FO membranes, which decreased the mass transfer resistance in the porous supporting layer. The skin layer was prepared via the continuous interfacial polymerization of polyamide as a relatively dense layer, with the reverse salt flux of less than 1 g/m^?2 h^?1. The mass transfer resistance and the reverse salt flux of the prepared FO membranes were remarkably reduced due to the functional design of the double‐layer structure, which effectively enhanced the separation selectivity and restrain the concentration polarization of the FO membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45133.     

Preparation of mesh-reinforced cellulose acetate forward osmosis membrane with very low surface roughness

Mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting compositions such as CA percent and 1, 4-dioxane/acetone ratio and also preparation conditions such as evaporation time, coagulation bath and annealing temperatures were tested for membranes’ performance. The results were compared with commercially CTA membranes. The best membrane (17.9% polymer and 1, 4-dioxane/acetone ratio of 1.89) showed water flux of 9.3 L/m²h (LMH) and RSF of 0.536 mol NaCl/m²h. Moreover, the membrane structure was reinforced by a polyester mesh, which created micro pores in the back of the membrane. This caused higher water flux and RSF compared to membranes without mesh. FO membrane prepared under best conditions, had a smoother surface than commercial ones. This feature enhances the fouling properties of the membrane, which can be appropriate for wastewater treatment applications.     

Developing thin‐film‐composite forward osmosis membranes on the PES/SPSf substrate through interfacial polymerization

A new scheme has been developed to fabricate high‐performance forward osmosis (FO) membranes through the interfacial polymerization reaction on porous polymeric supports. p‐Phenylenediamine and 1,3,5‐trimesoylchloride were adopted as the monomers for the in‐situ polycondensation reaction to form a thin aromatic polyamide selective layer of 150 nm in thickness on the substrate surface, a lab‐made polyethersulfone (PES)/sulfonated polysulfone (SPSf)‐alloyed porous membrane with enhanced hydrophilicity. Under FO tests, the FO membrane achieved a higher water flux of 69.8 LMH when against deionized water and 25.2 LMH when against a model 3.5 wt % NaCl solution under 5.0 M NaCl as the draw solution in the pressure‐retarded osmosis mode. The PES/SPSf thin‐film‐composite (TFC)‐FO membrane has a smaller structural parameter S of 238 μm than those reported data. The morphology and topology of substrates and TFC‐FO membranes have been studied by means of atomic force microscopy and scanning electronic microscopy. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Synthesis and characterization of PES/PSF/PEG by immersion precipitation for Mediterranean seawater desalination by FO membrane

In the present study, a simple, inexpensive, nontoxic, and environmentally friendly polyethylene glycol (PEG) polymer was used to enhance the hydrophilicity of the forward osmosis (FO) membrane using various PEG concentrations as a pore forming agent in the casting solution of polyethersulfone/polysulfone (PES/PSF) blend membranes. A nonwoven PES/PSF FO blend membrane was fabricated via the immersion precipitation phase inversion technique. The membrane dope solution was cast on polyethylene terephthalate (PET) nonwoven fabric. The results revealed that PEG is a pore forming agent and that adding PEG promotes membrane hydrophilicity. The membrane with 1 wt% PEG (PEG1) had about 27% lower contact angle than the pristine blend membrane. The PEG1 membrane has less tortuosity (which reduces from 3.4–2.73), resulting in a smaller structure parameter (S value) of 277 μm, due to the presence of open pores on the bottom surface structure, which results in diminished ICP. Using 1 M NaCl as the draw solution and distilled water as the feed solution, the PEG1 membrane exhibited higher water flux (136 L m⁻² h⁻¹) and lower reverse salt flux (1.94 g m⁻² h⁻¹). Also, the selectivity of the membrane, specific reverse salt flux, (J_s/J_w) showed lower values (0.014 g/L). Actually, the PEG1 membrane has a 34.6% higher water flux than the commercial nonwoven-cellulose triacetate (NW-CTA) membrane. By means of varied concentrations of NaCl salt solution (0.6, 1, 1.5, and 2 M), the membrane with 1 wt% PEG showed improved FO separation performance with permeate water fluxes of 108, 136, 142, and 163 L m⁻² h⁻¹. In this work, we extend a promising gate for designing fast water flux PES/PSF/PEG FO blend membranes for water desalination.     

Thin film composite forward osmosis membranes with poly(2‐hydroxyethyl methacrylate) grafted nano‐TiO2 as additive in substrate

The poly(2‐hydroxyethyl methacrylate) grafted titanium dioxide nanoparticles were synthesized and added to the substrate of flat‐sheet thin film composite forward osmosis (TFC‐FO) membranes. The hydrophilicity of substrate was improved, which was advantageous to enhance the water flux of TFC‐FO membranes. The membranes containing a 3 wt % TiO₂‐PHEMA in the substrate exhibited a finger‐like structure combined with sponge‐like structure, while those with lower or without TiO₂‐PHEMA content showed fully finger‐like structures. As for FO performance, the TFC‐FO membranes with 3 wt % TiO₂‐PHEMA content achieved the highest water flux of 42.8 LMH and 24.2 LMH against the DI water using 2M NaCl as the draw solution tested under the active layer against draw solution (AL‐DS) mode and active layer against feed solution (AL‐FS) mode, respectively. It was proven that the hydrophilic property of membrane substrates was a strong factor influencing the water flux in FO tests. Furthermore, the structural parameter was remarkably decreased with an increase of TiO₂‐PHEMA content in membrane substrate, indicating the reducing of internal concentration polarization. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43719.     

Fabrication of a pilot scale module of thin film composite hollow fiber membrane for osmotic pressure‐driven processes

Polyamide thin film composite hollow fiber membranes have advantages in their unique structure compared to flat sheet membranes. This study examined interfacial polymerization methods for fabricating pilot scale hollow fiber membranes (membrane area: 1.2 m², number of hollow fiber strands: 1200). For use in osmotic pressure‐driven processes, a one‐pot hydrophilic interfacial polymerization procedure was developed simultaneously to modify the surface property and synthesize polyamide thin film. With the procedure, a pilot scale module has a water flux of 13 LMH using a draw solution of 0.6M NaCl and a feed solution of distilled water through the design of the module configuration. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46110.     

Characteristics and potential applications of a novel forward osmosis hollow fiber membrane

There has been a resurgence of interest in forward osmosis (FO) as a potential means of desalination, dewatering and in pressure retarded osmosis, which Sidney Loeb was advocating over 3 decades ago. This paper describes the characteristics and potential applications of a newly developed FO hollow fiber membrane, which was fabricated by interfacial polymerization on the inner surface of a polyethersulfone (PES) hollow fiber. This FO membrane presents excellent intrinsic separation properties, with a water flux of 42.6 L/m² h using 0.5 M NaCl as the draw solution and DI water as the feed with the active layer facing the draw solution orientation at 23 °C. The corresponding ratio of salt flux to water flux was only 0.094 g/L, which is superior to all other FO membranes reported in the open literature. To evaluate different application scenarios, various NaCl solutions (500 ppm (8.6 mM), 1 wt.% (0.17 M) and 3.5 wt.% (0.59 M)) were used as the feed water to test the performance of the FO membrane. The membrane can achieve a water flux of 12.4 L/m² h with 3.5 wt.% NaCl solution as the feed and 2 M NaCl as the draw solution, suggesting it has good potential for seawater desalination.     

Preparation of high‐performance zeolite NaA membranes in clear solution by adding SiO2 into Al2O3 hollow‐fiber precursor

Zeolite NaA membranes were prepared in a clear synthesis solution without the aid of nanoseeds. To improve the properties of the membranes formed in a clear solution, alumina hollow fibers were fabricated by adding silica powder to the conventional spinning slurry, resulting in hollow fibers with a mullite phase. Prior to the membrane synthesis, the hollow fibers were pretreated by dipping in an aged synthesis solution diluted with isopropanol. Dense zeolite NaA membranes on mullite‐containing alumina hollow fibers were successfully obtained at 100°C for 2 h without the aid of nanoseeds. The membranes have a good pervaporation performance with a high flux of 10.8 kg m^?2 h^?1 and a separation factor of over 10,000. The abundant mullite‐phase hydroxyl groups on the support surface promote the nucleation and growth of zeolite crystals on the support, resulting in dense membranes. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2679–2688, 2018     

Morphological controlling of CTA forward osmosis membrane using different solvent-nonsolvent compositions in first coagulation bath

Cellulose triacetate (CTA) membranes were fabricated via a modified nonsolvent induced phase separation (NIPS) method. Different solvent-nonsolvent compositions in first coagulation bath (FCB) were introduced to optimize CTA membrane structures. The effects of FCB compositions, immersion time and mass ratio of solvent (N-methyl-2-pyrrolidone, NMP) and nonsolvent (water, ethanol, ethylene glycol and glycerol) on membrane morphology and performance were systematically investigated. Prospective membranes with a dense bottom layer and a scaffold-like top layer were obtained under room temperature, owing to the low relative energy difference (RED) between nonsolvent and polymer as well as the high viscosity of FCBs. A high water flux J_v (12.6 L m^?2 h^?1) and a low reserve salt flux J_s (1.32 g m^?2 h^?1) were obtained in the optimized membrane, with a structural parameter S of 119 μm. Compared with membranes prepared via conventional NIPS method and commercial CTA forward osmosis (FO) membranes, a remarkable improvement of J_s/J_v value and S value was achieved, indicating membranes with single dense-layer structure might suffer less from internal concentration polymerization (ICP) which is the main obstacle for the development of FO process. This study might help us pave the way to design superior CTA membrane structures for forward osmosis application.     

High performance forward osmosis cellulose acetate (CA) membrane modified by polyvinyl alcohol and polydopamine

Cellulose acetate (CA) is a low cost and readily available material widely used in forward osmosis (FO) membranes. However, the performance of pure CA membranes is not good enough in salt separation and the traditional modification methods are generally multistep and difficult to control. In this paper, we reported high performance cellulose acetate (CA) composite forward osmosis (FO) membranes modified with polyvinyl alcohol (PVA) and polydopamine (PDA). PVA was first cross-linked onto the surface of CA membranes, and then PDA was coated with a rapid deposition method. The membranes were characterized with respect to membrane chemistry (FTIR and XPS), surface properties comprising wettability (by water contact angle), and osmosis performance. The modified membrane coated by PVA and PDA shown better hydrophilicity and exhibited 16.72 LMH osmotic water flux and 0.14 mMH reverse solute flux with DI water as feed solution and 2.0 M NaCl as draw solution and active layer facing the feed solution. This simple and highly effective modification method makes it as an excellent candidate for further exploration for FO.     

Investigation of the effect of tetrahydrofuran and acetone as cosolvents in acrylonitrile–butadiene–styrene–based nanofiltration membranes

In this study, novel nanofiltration membranes were prepared with acrylonitrile–butadiene–styrene (ABS)–poly(ethylene glycol)–N,N ‐dimethylacetamide–[tetrahydrofuran (THF)–acetone] as a cosolvent. All of the membranes were prepared by the phase‐inversion method and a casting solution technique. The effects of the cosolvent concentration in the casting solution and the evaporation time before the immersion/precipitation step on the membrane performance and properties were investigated. The prepared membranes were characterized through their permeation flux, salt rejection, and phase‐inversion time values. The salt rejection was increased from 53% for the bare ABS membrane to 73% for the membrane prepared with 40 wt % THF as a cosolvent. The water flux was decreased from 4345 to 1121 cc m^?2 h^?1 with the addition of THF to the casting solution. The addition of acetone to the casting solution improved the water flux from 4345 to 5607 cc m^?2 h^?1 and reduced the salt rejection from 53 to 36%. The evaporation time of THF and acetone led to similar effects on flux and rejection. However, with evaporation time, membranes prepared with acetone were denser than those prepared with THF; this was due to the lower boiling point and higher boiling rate of acetone at the same temperatures. This resulted in greater effects on the ABS performance and structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44993.     

Preparation and characterization of poly(vinyl chloride)/polystyrene/poly(ethylene glycol) hollow‐fiber ultrafiltration membranes

Hollow‐fiber ultrafiltration (UF) membranes were prepared from blends of poly(vinyl chloride) (PVC) and polystyrene (PS) with a dry/wet phase inversion method. Poly(ethylene glycol) (PEG) and N,N‐dimethylacetamide were used as the additive and solvent, respectively. The effects of the PEG concentration in the dope solution as an additive on the cross sections and inner and outer surface morphologies, permeability, and separation performance of the hollow fibers were examined. The mean pore size, pore size distribution, and mean roughness of both the inner and outer surfaces of the produced hollow fibers were determined by atomic force microscopy. Also, the mechanical properties of the hollow‐fiber membranes were investigated. UF experiments were conducted with aqueous solutions of poly(vinyl pyrrolidone) (PVP; K‐90, M_w = 360 kDa). From the results, we found that the PVC/PS hollow‐fiber membranes had two layers with a fingerlike structure. These two layers were changed from a wide and long to a thin and short morphology with increasing PEG concentration. A novel and until now undescribed shape of the nodules in the outer surfaces, which was denoted as a sea‐waves shape, was observed. The outer and inner pore sizes both increased with increasing PEG concentration. The water permeation flux of the hollow fibers increased from 104 to 367 L m^?2 h^?1 bar^?1) at higher PEG concentrations. The PVP rejection reached the highest value at a PEG concentration of 4 wt %, whereas at higher values (from 4 to 9 wt %), the rejection decreased. The same trend was found also for the tensile stress at break, Young's modulus, and elongation at break of the hollow fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 989‐1004, 2013     

Poly(vinylidene fluoride)–polyacrylonitrile blend flat‐sheet membranes reinforced with carbon nanotubes for wastewater treatment

In this reported study, poly(vinylidene fluoride) (PVDF) and polyacrylonitrile (PAN) blend flat‐sheet membranes were prepared via a phase‐inversion method with various loadings of multiwalled carbon nanotubes. The effects of the carbon nanotubes (CNTs) on the performance and morphology of the PVDF–PAN composites were investigated via tests of the pure water flux and rejection of bovine serum albumin, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and contact angle (CA) analysis. The experimental results demonstrate that the CNTs contributed to the improvement of the flux and hydrophilicity of the membranes. The maximum value of the flux was 398.1 L m^?2 h^?1, and the value of CA for the composite membranes was found to be 48°. In addition, the results of the mechanical properties tests illustrate that the brittleness and plasticity of the hybrid membranes were greatly improved by the presence of the CNTs. The flux recovery ratio was maintained at 75%; this demonstrated that the PVDF–PAN membranes enhanced with the CNTs possessed good antifouling performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46155.