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.     

抗污染芳香聚酰胺反渗透膜研究进展

聚酰胺反渗透膜具有选择透过性高、化学稳定性好等优点,在水处理领域应用广泛。但膜污染导致的通量下降、寿命降低等问题严重制约了其发展与应用,开发抗污染反渗透膜是缓解膜污染的重要手段。本文根据抗污染膜作用机理将抗污染反渗透膜分为抗黏附型、污染驱除型和杀菌型,综述了近年来相关方面的研究成果,并对合理组合多种机制制备抗污染反渗透膜的进展进行简要概括,最后对抗污染反渗透膜的发展前景进行了展望。     

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     

Tris(hydroxymethyl)aminomethane polyamide thin‐film‐composite antifouling reverse osmosis membrane

For the applications of reverse osmosis (RO) process, membrane fouling caused by organic molecule adsorption is still a serious problem which significantly decreases membrane lifespan and increases operation costs. In this present article, we report the thin film composite (TFC) RO membrane functionalized with tris(hydroxymethyl)aminomethane (THAM) using one‐step method for improved antifouling property. The results of surface characterization indicated that THAM was successfully grafted onto the active layer of membrane by covalent linkage. Mult‐hydroxyl‐layer was generated and remained steadily on TFC membrane surface after modification. The contact angle decreased from 75.9 ± 3.0° to 46.9 ± 2.3°, which showed a distinct improvement of membrane surface hydrophilicity after modification. The grafted THAM improved water flux by 28.3%, while salt rejection was almost unchanged in membrane property tests. The modified membranes presented preferable antifouling property to foulants of bovine serum albumin, sodium alginate, and dodecyl trimethyl ammonium bromide than that of pristine membranes during dynamic fouling experiments. The method in this study provided an effective way to improve antifouling property of the polyamide thin‐film‐composite RO membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45891.     

Novel thin-film composite forward osmosis membrane using polyethylenimine and its impact on membrane performance

ABSTRACT

Polyethylenimine (PEI), a cationic, hydrophilic flexible polymer has been incorporated into the polyamide (PA) skin layer through an interfacial polymerization (IP) reaction. The modified thin-film composite (TFC) membranes display improved forward osmosis performance: enhancement in water permeability and antifouling characteristics. The incorporation of PEI into the skin layer has been evidenced by different characterization techniques; FTIR for modification of surface functionalities, zeta potential for surface charge, water contact angle for hydrophilicity of the surface, SEM and AFM for surface morphologies including surface roughness, XPS for surface attachment of heteroatoms and their relative composition. PEI was found to induce a positive zeta potential, high degree of hydrophilicity and high factional free volume into the active skin layer. The increase in the relative composition of PEI in the active skin layer was found to decrease the surface roughness and the skin layer thickness. An optimized PEI composition showed significantly enhanced water permeability, salt rejection and fouling resistance in FO and pressure-retarded osmosis (PRO) mode.     

Dendritic molecules give excellent long-lasting desalination fouling resistance to reverse osmosis membrane by generating an amine-rich layer

The organic fouling of polyamide membranes is one of the most serious problems in reverse osmosis fields such as sea water desalination and sewage disposal. In this study, poly(ethylene imine)–poly(ethylene glycol) dendrimer is used to improve the fouling resistance of polyamide reverse osmosis membranes. A crucial pretreatment is carried out with a reaction between poly(ethylene imine) and acyl chloride on the nascent polyamide surface, generating an amine-rich selective layer. Poly(ethylene glycol) diglycidyl ether is then attached to the primary amine group. The results illustrate a remarkable improvement in membrane surface hydrophilicity after modification (the contact angle decreases from 96.7° to 49.5°). Dynamic fouling tests are implemented with bovine serum albumin as a typical protein foulant, in which the membranes show very low protein adsorption (flux recovery ratio 96.9%). After 11-cycle fouling tests, the membranes show excellent long-term stability and remarkable antifouling property and cleaning performance. This approach of grafting a dendrimer might provide new insight for antifouling modifications for membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47368.     

Recent advances in polymer and polymer composite membranes for reverse and forward osmosis processes

Semipermeable membranes are the core elements for membrane water desalination technologies such as commercial reverse osmosis (RO) process and emerging forward osmosis (FO) process. Structural and chemical properties of the semipermeable membranes determine water flux, salt rejection, fouling resistance, and chemical stability, which greatly impact energy consumption and costs in osmosis separation processes. In recent years, significant progress has been made in the development of high-performance polymer and polymer composite membranes for desalination applications. This paper reviews recent advances in different polymer-based RO and FO desalination membranes in terms of materials and strategies developed for improving properties and performances.     

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.     

Taurine as an additive for improving the fouling resistance of nanofiltration composite membranes

A hydrophilic compound, taurine, was investigated as an additive in the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC) to prepare thin‐film composite (TFC) membranes. The resulting membranes were characterized by X‐ray photoelectron spectroscopy and attenuated total reflectance–Fourier transform infrared spectroscopy. The morphology and hydrophilicity of the membranes were investigated through scanning electronic microscopy and water contact angle measurements. The separation performance of the TFC membranes was investigated through water flux and salt rejection tests. The protein‐fouling resistance of the films was evaluated by water recovery rate measurements after the treatment of bovine serum albumin. The membrane containing 0.2 wt % taurine showed the best performance of 92% MgSO₄ rejection at a flux of 31 L m^?2 h^?1 and better antifouling properties than the PIP–TMC membranes. An appropriately low concentration of taurine showed the same MgSO₄ rejection as the PIP–TMC membranes but a better fouling resistance performance. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41620.     

Chlorine-resistant and internal-concentration-polarization-mitigated polyamide membrane via tethering poly(ethylene glycol) methacrylate

To improve chlorine resistance and mitigate the internal concentration polarization (ICP), a membrane surface was tethered with poly(ethylene glycol) methacrylate (PEGMA). Characterization by attenuated total reflection–Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy analysis, and field emission scanning electron microscopy indicated the successful tethering of PEGMA onto the membrane. The antifouling and antichlorine characteristics were assessed in reverse osmosis (RO) and forward osmosis (FO) processes. The water flux increased obviously to 85.00 from 60.00 L m⁻² h⁻¹ (LMH) in the RO process; the chlorine stability of the modified membrane was improved. The greatly reduced structural parameters indicated that the ICP of the FO membrane was successfully alleviated; the water flux decreased greatly for the original membrane from 3.40 to 0.01 LMH, whereas it fell only slightly from 10.99 to 9.32 LMH for the modified membrane during synthetic sewage treatment. The ICP was greatly mitigated; the antichlorine performances and the antifouling characteristics drastically improved after grafting with PEGMA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47406.     

Improvement of performance of polyamide reverse osmosis membranes using dielectric barrier discharge plasma treatment as a novel surface modification method

In this research, surface modification of aromatic polyamide thin film composite (TFC) reverse osmosis (RO) membranes was carried out using dielectric barrier discharge (DBD) plasma treatment to improve the performance and fouling resistance of prepared RO membranes. First, polyamide TFC RO membranes were synthesized via interfacial polymerization of m‐phenylenediamine and trimesoyl chloride monomers over microporous polysulfone support membrane. Next, the DBD plasma treatment with 15 s, 30 s, 60 s, and 90 s duration was used for surface modification. The surface properties of RO membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), SEM, AFM, and contact angle measurements. The ATR‐FTIR results indicated that DBD plasma treatment caused hydrogen bonding on the surface of RO membranes. Also, the contact angle measurement showed that the hydrophilicity of the membranes was increased due to DBD plasma treatment. The changes in the membranes surface morphology indicated that the surface roughness of the membranes was increased after surface modification. In addition, it was found that the DBD plasma treatment increased the water permeation flux significantly and enhanced sodium chloride (NaCl) salt rejection slightly. Moreover, the filtration of bovine serum albumin revealed that the antifouling properties of the modified membranes had been improved. POLYM. ENG. SCI., 59:E468–E475, 2019. © 2018 Society of Plastics Engineers     

Surface modification of polyamide reverses osmosis membrane by phosphonic acid group with improved performance

A facial method for preparing reverse osmosis polyamide (PA) membranes of excellent antifouling and separation performance was developed via covalently grafting phosphonic acid on membrane surface. First, a pristine PA layer was synthesized by interfacial polymerization between m-phenylenediamine and trimesoyl chloride. Then, a second interfacial reaction was implemented between ethylenediamine and the residual acryl chloride on the pristine PA layer, generating an active layer enriched by primary amine. Finally, the amine-rich surface treated by formaldehyde and phosphorous acid to produce a membrane surface modified by phosphonic acid groups. Surface characterization by attenuated total reflectance infrared, X-ray photoelectron spectroscopy and zeta-potential measurements illustrated the presence of phosphonic acid group. The lowest contact angle of modified membrane was 26°, demonstrating the membrane possessed an outstandingly wettable surface. The optimal separation performance was 88 L m⁻² h⁻¹ of water flux and 99.4% of salt rejection under 1.55 MPa. In addition, bovine serum albumin was used as organic foulant to measure the antifouling property of membranes. The result of dynamic fouling experiments indicated that the modified membrane exhibited better antifouling (of which the irreversible fouling degree was 7.1%) compared with commercial membrane BW30 (of which the irreversible fouling degree was 13.5%). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46931.     

Physical modification of polymeric support layer for thin film composite forward osmosis membranes by metal–organic framework-based porous matrix membrane strategy

Physical modification of support layers (SLs) for thin-film composite (TFC) forward osmosis (FO) membranes is the main goal of this study. Accordingly, the strategy of metal–organic framework (MOF)-based porous matrix membrane (PMM) was used for the fabrication of controllable SLs. Fourteen different TFC FO membranes were successfully fabricated by interfacial polymerization (IP) technique over the fourteen different SLs made of polyetherimide (PEI), polyethersulfone (PES), and twelve MOF-based PMM. The controllable MOF particles, fabricated SLs, and TFC membranes were characterized by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle (CA), inductively coupled plasma (ICP), and developed SHN1 method. The results showed that the PMM strategy can lead to an increase in the degree of crosslinking of polyamide (PA) as a result of physical modification of the original SLs. Also, the PMM strategy reduced the structural parameters and hence the internal concentration polarization (ICP) was controlled. However, according to the characteristic curve, physical modification of the structure of PES and PEI by MOF-based PMM strategy caused a small and dramatic effect (respectively) on the performance of the TFC FO membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48672.     

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.     

Effects of free volume in thin‐film composite membranes on osmotic power generation

For the first time, the effects of free volume in thin‐film composite (TFC) membranes on membrane performance for forward osmosis and pressure retarded osmosis (PRO) processes were studied in this work. To manipulate the free volume in the TFC layer, a bulky monomer (i.e., p‐xylylenediamine) was blended into the interfacial polymerization and methanol immersion was conducted to swell up the TFC layer. Results from positron annihilation lifetime spectroscopy (PALS) show that p‐xylylenediamine blending and methanol induced swelling enlarge and broaden the free volume cavity. In addition, the performance of TFC membranes consisting of different free volumes were examined in terms of water flux, reverse salt flux, and power density under high pressure PRO operations. The TFC‐B‐5 membrane (i.e., a TFC membrane made of blending monomers) with a moderate free volume shows the highest power density of 6.0 W/m² at 9 bar in comparison of TFC membranes with other free volumes. After PRO operations, it is found that the free volume of TFC layers decreases due to high pressure compression, but membrane transport properties in terms of water and salt permeability increase. Interestingly, the membrane performance in terms of resistance against high pressures and power density stay the same. A slow positron beam was used to investigate the microstructure changes of the TFC layer after PRO operations. Compaction in free volume occurs and the TFC layer becomes thinner under PRO tests but no visible defects can be observed by both scanning electronic microscopy and PALS. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4749–4761, 2013     

Photo‐induced grafting of poly(ethylene glycol) onto polyamide thin film composite membranes

In this study, the surface grafting of poly(ethylene glycol) (PEG) onto commercial polyamide thin film composite (TFC‐PA) membranes was carried out, using ultraviolet photo‐induced graft polymerization method. The attenuated total reflection Fourier transform infrared spectra verify a successful grafting of PEG onto the TFC‐PA membrane surface. The scanning electron microscope and atomic force microscope analyses demonstrate the changes of the membrane surface morphology due to the formation of the PEG‐grafted layer on the top. The contact angle measurements illustrate the increased hydrophilicity of the TFC‐PA‐g‐PEG membrane surfaces, with a significantly reduced water contact angles compared to the unmodified one. Consequently, the separation performance of the PEG‐grafted membranes is highly improved, with a significant enhancement of flux at a great retention for removal of the different objects in aqueous feed solutions. In addition, the antifouling property of the modified membranes is also clearly improved, with the higher maintained flux ratios and the lower irreversible fouling factors compared to the unmodified membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45454.     

Polyethyleneimine-Mediated Polyamide Composite Membrane with High Perm-Selectivity for Forward Osmosis

Thin-film composite (TFC) membranes comprised of a polyamide (PA) selective layer upon a porous substrate dominate the forward osmosis (FO) membrane market. However, further improvement of perm-selectivity still remains a great challenge. Herein, a polyethyleneimine (PEI) interlayer is intentionally designed prior to interfacial polymerization (IP) to tailor the PA layer, which thus improves the separation performance. The PEI interlayer not only improves the substrate hydrophilicity for adsorbing more diamine monomer and controlling its release rate, but also participates in IP reaction by crosslinking with acyl chloride (TMC). Furthermore, it can decrease the electronegativity of the substrate for decreasing reverse salt diffusion. Consequently, a denser, thinner and smoother PA layer is formed due to the uniform distribution, controllable release of diamine monomer and the extra crosslinking between PEI and TMC. Furthermore, the PA layer becomes more hydrophilic with PEI involvement. As a result, the asprepared TFC membrane exhibits a favorable water flux of 16.1 L m⁻² h⁻¹ and an extremely low reverse salt flux (1.25 g m⁻² h⁻¹). Meanwhile, it achieves an excellent perm-selectivity with a ratio of water to salt permeability coefficient of 8.25 bar⁻¹. Moreover, it exhibits an outstanding antifouling capacity. The work sheds light on fabricating high perm-selective membranes for desalination.     

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     

Feasibility of using polycarbonate as a substrate of thin film composite membrane in forward osmosis

In the present study, thin film composite (TFC) forward osmosis (FO) membranes with polycarbonate (PC (and polyether sulfone (PES) as substrates were fabricated to investigate the impact of the structural parameters of substrate on the performance of the membranes. Firstly, the substrates were prepared by Loeb-Sourirajan method. Characterization techniques including FESEM, contact angle measurement, pure water flux, gas permeability test, and tensile test were applied to investigate the properties of the substrates. After preparing suitable substrates, active layers were fabricated via interfacial polymerization (IP) technique. The performance and characterization test showed that PC is a relatively hydrophilic polymer with a good property for using as a substrate of FO TFC membrane but as the result of gas permeability test show, this membrane has large surface pore size in comparison with PES membrane. Mean pore size of PC and PES membrane is 378 and 139 nm, respectively. Also, the results show that the effective surface porosity of PC (285, 1/m) is more than PES (213, 1/m) substrate.     

正渗透膜过程中临界通量的影响因素

临界通量是膜过程中一种重要的污染特性指标.采用阶梯汲取液浓度递增法测定不同污染物、架桥离子浓度及膜面流速对正渗透(FO)膜过程临界通量的影响.结果表明,海藻酸钠(SA)、腐殖酸(HA)及二氧化硅(SiO2)污染时FO膜临界通量值分别为29.32,46.35和32.17 L/(m2·h);随 Ca2+浓度由0 mmol/...