Nanocomposite hollow fiber nanofiltration membranes: Fabrication,characterization, and pilot-scale evaluation for surface water treatment

Thin-film nanocomposite (TFN) membranes were fabricated by interfacial polymerization of a polyamide (PA) layer on the shell side of hollow fiber membrane supports. TiO₂ nanoparticle loadings in the thin-film layer were 0.01, 0.05, and 0.20 wt %. Nanoparticle-free PA thin-film composite (TFC) membranes served as the comparative basis. The TFN membranes were characterized in terms of the chemical composition, structure, and surface properties of the separation layer. Incorporating nanoTiO₂ improved membrane permeability up to 12.6-fold. During preliminary laboratory-scale evaluation, TFN membranes showed lower salt rejection but higher TOC rejection in comparisons with the corresponding values for TFC controls. Based on the performance in lab-scale tests, TFN membranes with 0.01 wt % nanoTiO₂ loading were selected for an evaluation at the pilot scale with synthetic surface water as the feed. While the permeate flux during long-term pilot-scale operation gradually decreased for TFC membranes, TFN membranes had a higher initial permeate flux that gradually increased with time. The TOC rejection by TFN and TFC membranes was comparable. We conclude that TFN membranes show promise for full-scale surface water treatment applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48205.     

Effects of Gelatin and Nano-ZnO on the Performance and Properties of Cellulose Acetate Water Membranes

Biodegradable cellulose acetate (CA) membranes were prepared via phase inversion induced by immersion precipitation method. Acetic acid and deionized water were used as solvent and non-solvent, respectively. The modifying effect of gelatin and zinc oxide (ZnO) nanoparticles additives was investigated on the membranes in terms of water flux, protein rejection percentage, and fouling ability during two hours of bovine serum albumin separation from aqueous solution. Specimens were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), tensile test, contact angle technique, and porosity measurement. The incorporation of gelatin and ZnO nanoparticles into the CA matrix increased the porosity coefficient and hydrophilicity. Moreover, gelatin improved the tensile properties of the membrane.     

Self‐Assembled PMMA Porous Membranes Decorated with In Situ Synthesized ZnO Nanoparticles with UV‐Tunable Wettability

This study reports a simple approach to fabricate porous poly(methyl methacrylate) (PMMA) membranes homogeneously decorated with exposed zinc oxide (ZnO) nanoparticles (NPs). This fabrication method significantly overcomes the disadvantages of both conventional foaming processes and incorporation of inorganic NPs in polymeric matrices. In particular, the porous structure is simply self‐assembled by slowly evaporating a suitable solvent. The ZnO NPs are in situ formed by a thermally activated conversion of the zinc acetate precursor, previously embedded in the polymeric matrix. Scanning and transmission electron microscopy investigations show the formation of the desired self‐assembled highly porous structure and ZnO NPs with branched morphology, respectively. The wetting behavior of the membranes surface is studied as a function of the ZnO content and UV irradiation, exploiting the switchable wettability of ZnO. The obtained unexpected results are then tentatively rationalized taking into account the surface chemistry and the roughness that arises from both porous structure and the different NPs dimensions and content.     

Improved separation performance of polyamide based reverse osmosis membrane incorporated with poly(dopamine) coated carbon nanotubes

A series of polyamide thin-film nanocomposite (PA TFN) membranes have been fabricated by incorporating hydrophilic poly(dopamine) (PDA) coated carbon nanotubes (CNTs@PDA) into the PA selective layer via interfacial polymerization. The effects of PDA coating thickness on surface characteristics and separation performances of membranes are studied in detail. The PDA coating makes the surface of PA TFN membrane more hydrophilic, smoother and less electronegative. The desalination performance is obviously influenced by the coating thickness of PDA and the loading concentration of PDA@CNTs. The water fluxes of PDA@CNTs incorporated PA TFN membranes have been improved without sacrificing NaCl rejections. When the loading concentration is 0.0010%, the maximum water flux is 48.1 L m⁻² h increasing by 45% compared with that of pristine PA membrane. Meanwhile, the NaCl rejection is up to 99.8%. The CNTs@PDA incorporated PA TFN membranes exhibit better anti-fouling property and separation performance durability. This work proves that CNTs@PDA has great potential application in PA TFN membranes.     

Thermal,mechanical, and structural properties of zno/polyethylene membranes made by thermally induced phase separation method

In this study, ZnO/polyethylene membranes were fabricated via thermally induced phase separation method. A set of tests including FE‐SEM, EDX, XRD, DSC, TGA, DMA, mechanical test, and pure water flux (PWF) for characterization of membranes were carried out. The results of EDX, XRD, and TGA analyses confirmed the presence of ZnO nanoparticles in the polymer matrix. The results of DSC analysis revealed that the melting point as well as the crystallinity of the membranes increased slightly with increasing ZnO content. However, glass transition temperature of the membranes was not affected by presence of the particles. Addition of nanoparticles also increased storage modulus, loss modulus. and tensile at break of the membranes due to the stiffness improvement effect of inorganic ZnO. Finally, it was observed that incorporation of the nanoparticles improved PWF of the membranes, whereas humic acid rejection decreased due to the increase in mean pore radius of membranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42338.     

Supported Electrospun Ultrafine Fibrous Poly(tetrafluoroethylene)/ZnO Porous Membranes and their Photocatalytic Applications

Supported photocatalytic poly(tetrafluoroethylene) (PTFE)/ZnO porous membranes were prepared by sintering electrospun PTFE/poly(vinylalcohol)/zinc acetate dehydrate composite membranes. Electrospun PTFE membranes were utilized as supports with excellent chemical stability and high specific surface area, while the photocatalyst‐ZnO particles derived from the thermal decomposition of zinc acetate dehydrate were homogeneously immobilized on the surface of ultrafine PTFE fibers. The PTFE/ZnO membranes could be easily recovered and reused after water treatment. PTFE/ZnO membranes are expected to have a wide range of potential applications in photocatalysis and photocatalysis‐membrane reactors, playing the role of a catalyst as well as a selective barrier against contaminants of interest.     

A high flux graphene oxide nanoparticles embedded in PAN nanofiber microfiltration membrane for water treatment applications with improved anti-fouling performance

A high flux and anti-fouling graphene oxide (GO) nanoparticles embedded in polyacrylonitrile (PAN) nanofiber microfiltration membranes (PANGMs) were fabricated through the facile electrospinning method and were characterized by water treatment applications. The synthesized GO nanoparticles and GO nanoparticles embedded in PAN nanofiber membranes were characterized by FESEM, FTIR, and EDS. SEM images showed that the PANGMs possessed randomly overlaid fibers with a network-like highly porous structure similar to the pristine PAN nanofiber membrane, while agglomeration of GO nanoparticles was observed at high GO concentration. The introduction of GO nanoparticles into the PAN polymeric matrix significantly increased the permeation flux of the resulting membrane in both dead-end and cross-flow filtration systems. A high flux recovery ratio of 96.6% and a low irreversible fouling ratio of 3.4% were obtained at 2% (wt.) GO nanoparticles. More importantly, a high flux recovery ratio of GO nanoparticles embedded in PAN nanofiber membrane was retained after 20 repeated cycles of activated sludge suspension filtration. Therefore, it can speculate that the incorporation of GO nanoparticles into the PAN nanofibers could efficiently improve the anti-fouling ability of membranes which had opened up an alternative for the preparation of high flux and anti-fouling microfiltration membranes in practical water treatment applications such as membrane bioreactors.

     

Controllable preparation of ZnO porous flower through a membrane dispersion reactor and their photocatalytic properties

Three dimensional (3D) flower-like basic zinc carbonate constructed by multilayered nanoplates were rapidly prepared at room temperature through the direct precipitation method coupled with membrane dispersion technology, and porous ZnO with similar structures could be obtained after calcining the precursor. The structural properties of the products before and after the calcining process were characterized by SEM, TEM and XRD. The supersaturation of the reaction system due to the membrane dispersion played an important role in the formation of uniform Zn₅(CO₃)₂(OH)₆ precursors. A plausible mechanism was proposed for the formation of the flower-like ZnO assembled by nanoplates composed of nanoparticles. The obtained ZnO microspheres showed excellent photocatalytic properties, which could be attributed to the open structure and remarkable amount of porous nanoplates.     

Fabrication of polyamide thin film nanocomposite reverse osmosis membrane incorporated with a novel graphite-based carbon material for desalination

The properties of polyamide (PA) thin film composite (TFC) membranes are affected by many variables, especially the additives in the process of interfacial polymerization that play an important role in the properties of membranes. In this study, a new type graphite carbon was added into organic phase containing trimesoyl chloride for interfacial polymerization with aqueous phase containing m-phenylenediamine to prepare modified polyamide thin film nanocomposite (TFN) membranes for reverse osmosis (RO) adhibition. Polysulfone ultrafiltration membranes were used as the carrier of the interfacial polymerization. The concentration of graphite carbon was selected from 0.002 to 0.01 wt%. The polyamide nanocomposite membrane prepared with the concentration of 0.004 wt% graphite carbon showed the best RO desalination performance, which the water flux of this TFN membrane is over 2.3 times as much as pristine TFC membrane, and the salt rejection is over 99%. This article provides a well-performing polyamide thin film nanocomposite membrane modified by a new-type carbon nanoparticles consequently.     

Enhanced the antifouling and antibacterial performance of PVC/ZnO-CMC nanoparticles ultrafiltration membrane

Inorganic nanoparticles (NPs) have been employed in modification for polyvinyl chloride (PVC) membrane intrinsic hydrophobicity. Carboxymethyl chitosan (CMC), a natural organic matter, was used to relieve the agglomeration of zinc oxide (ZnO) NPs in the membrane matrix. In this paper, ZnO-CMC NPs were successfully prepared via co-precipitation approach, blended with PVC membranes, and the effect of ZnO-CMC NPs for the membrane properties was studied. The SEM and EDX confirmed excellent dispersion of ZnO-CMC NPs on the membrane surface. The enhanced hydrophilicity, porosity and inter-connected finger-like strcture of modified membranes confirmed by water contact angle and SEM. In addition, pure water flux of PVC/ZnO-CMC composite membrane was 107.36 L m⁻² h⁻¹ (PVC/ZnO-CMC (0.25 wt%)), which was higher than that of neat PVC membrane (83.11 L m⁻² h⁻¹). Importantly, the modified membranes exhibits lower static BSA adsorbtion because of the improved hydrophilicity, and a higher flux recovery rate (>90%) after three sequential filtration cycles. The antibacterial behavior of PVC/ZnO-CMC membrane was tested simply using Escherichia coli, and the results indicated that all composite membranes possess excellent antibacterial properties. Our work presents PVC/ZnO-CMC NPs composite membrane a promising future in wastewater treatment and antibacterial application.     

Preparation and application of zinc oxide/poly(m-phenylene isophthalamide) hybrid ultrafiltration membranes

A small molecular-weight cut-off (MWCO) of 6000 Da poly(m-phenylene isophthalamide) (PMIA) embedded zinc oxide (ZnO) hybrid ultrafiltration (UF) membrane was synthesized via nonsolvent-induced phase separation (NIPS). Tests of field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), thermal gravimetric analyzer (TGA), Fourier transform infrared (FTIR), capillary flow porometer (CPF), mechanical test, and pure water flux (PWF) for characterization of membranes were carried out. The EDX, FTIR, and TGA indicated the presence of ZnO in the polymer matrix. The hybrid membranes showed enhanced pore density, PWF by the presence of the particles. The contact angle and water flux of modified membrane with 0.03 wt % of nano-ZnO were 47.7° and 52.58 L·m⁻²·h⁻¹ compared to 71.6° and 36.27 L·m⁻²·h⁻¹ respectively; Compared with the hydrophobic membrane, the PMIA membrane, with hydrophilicity, is supposed to exhibit good antifouling properties. Furthermore, the thermal stability and mechanical properties of the modified membranes were increased. Finally, the hybrid membrane was used in treating papermaking white wastewater and exhibited good separation and high water flux. The great properties of the ultrafiltration PMIA membranes indicate their potential for excellent performance in industrial applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47583.     

Preparation and characterization of polyzwitterionic hydrogel coated polyamide-based mixed matrix membrane for heavy metal ions removal

A novel polyzwitterionic hydrogel coated mixed matrix membrane (MMM) was successfully prepared, characterized and used for Cu²⁺, Mn²⁺, and Pb²⁺ heavy metal ions removal from water. Hydrophilic and porous covalent organic framework (COF) nanoparticles (NP) as filler were synthesized from melamine and terephthalaldehyde, and then incorporated into polyamide (PA) thin film composite (TFC) membrane. The hydrogel coating was applied by using a tailored cross-linkable polymer system in combination with concentration polarization enabled cross-linking. The effects of COF NP loading into PA layer and polyzwitterionic hydrogel coating on the membrane morphology and separation performance were studied using different analyses. The MMM prepared with a COF NP loading of 0.02 wt/wt% in the hexane dispersion used for NP deposition during PA layer formation (leading to 0.42 g/m²) exhibited an increased pure water permeability of around 200% compared with the neat PA TFC membrane while the Mn²⁺ ion rejection maintained above 98%. Scanning electron microscopy surface images and zeta potential profiles showed that the hydrogel was successfully deposited on the membrane surface. Furthermore, the hydrogel coating could decrease net surface charge of membranes but did not significantly influence the heavy metal ions rejections under nanofiltration conditions. The results of filtration experiment with protein solution indicated that the hydrogel coated membranes exhibited superior antifouling property, as shown by higher flux recovery ratio after washing with water, compared with neat PA TFC membrane and not coated MMM, respectively.     

Facile Synthesis and Antibacterial Activity of Bioplastic Membrane Containing In Doped ZnO/Cellulose Acetate Nanocomposite

The present work addresses a facile synthesis of Indium doped zinc oxide (IZO) cellulose acetate nanocomposite membrane. The membrane was prepared by casting method. Various weights of In:ZnO nanoparticles were added to solution formed by dissolution of cellulose acetate granules in acetone. The harvested membrane, after acetone evaporation, was characterized by various techniques including X ray diffraction, scanning electron microscopy, energy dispersive X ray and elemental mapping, Fourier transform infrared spectroscopy. The results show that the In:ZnO nanoparticles are well embedded in the cellulose acetate host matrix. The elemental mapping reveals that the nanoparticles are uniformly distributed. The optical characterization reveals the reduction of the transmittance in the UV (A and B range) of the CA/IZO composite with increasing the weight of the added IZO powder. This reduction was attributed to ZnO UV absorption. No noticeable peak assigned to ZnO bond are observed. However, IR peaks are shifted towards the higher wavenumber due to the change of the bonds environment with including IZO in the CA matrix. The antibacterial action of the synthetized nanocomposite membranes was tested against Escherichia coli (E. coli). Staphylococcus aureus (S. aureus). The assay results have shown that the membrane has no activity against (E. coli). In contrary, the synthetized membrane exhibits an interesting antibacterial activity against S. aureus. The inhibition region varies from 6 to 15 mm with increasing the weight ratio of filler. A zone of inhibition (ZOI) of 18 mm was observed for the membrane prepared with 30% wt. of In:ZnO. We noticed that the ZOI radius increases with the added weight of IZO. Due the settling down of the nanoparticles only one face of the membrane exhibits an antibacterial activity.

     

Effect of additives concentration on the surface properties and performance of PVDF ultrafiltration membranes for refinery produced wastewater treatment

The aim of this study was to investigate the effect of pore-forming hydrophilic additives on the porous asymmetric polyvinylideneflouride (PVDF) ultrafiltration (UF) membrane morphology and transport properties for refinery produced wastewater treatment. PVDF ultrafiltration membranes were prepared via a phase inversion method by dispersing lithium chloride monohydrate (LiCl·H₂O) and titanium dioxide (TiO₂) nanoparticles in the spinning dope. The morphological and performance tests were conducted on PVDF ultrafiltration membranes prepared from a different additive content. The top surface and cross-sectional area of the membranes were observed using a field emission scanning electron microscope (FESEM) and energy dispersive X-ray (EDX) analysis. The surface wettability of porous membranes was determined by the measurement of a contact angle. The mean pore size and surface porosity were calculated based on the permeate flux. The results indicated that the PVDF/LiCl/TiO₂ membranes with lower TiO₂ nanoparticles loading possessed smaller mean pore size, more apertures inside the membrane with enhanced membrane hydrophilicity. LiCl·H₂O has been employed particularly to reduce the thermodynamic miscibility of dope which resulted in increasing the rate of liquid–liquid demixing process. The maximum flux and rejection of refinery wastewater using PVDF ultrafiltration membrane achieved were 82.50 L/m² h and 98.83% respectively at 1.95 wt.% TiO₂ concentration.     

沸石/聚酰胺反渗透复合膜的制备

为了提高反渗透膜的通量,通过在界面聚合反应过程中添加NaA型纳米沸石分子筛制备了沸石/聚酰胺反渗透复合膜,采用SEM及复合膜性能测试的方法比较了沸石分子筛添加在水相或者油相中时对膜结构及分离性能的影响.SEM图谱结果表明:沸石分子筛添加在油相中时,沸石在聚酰胺基质中分散均匀,膜结构比较均一;但当沸石分子筛添加在水相中时...     

Fabrication of innovative forward osmosis membranes via multilayered interfacial polymerization on electrospun nanofibers

Practical application of forward osmosis (FO) membranes is beset by low water flux and vulnerability of selective polyamide (PA) layers. Herein, novel composite membranes were fabricated with multilayered PA via cyclic interfacial polymerization (IP) on electrospun polyethersulfone (PES) nanofiber substrates to realize high performance FO. The membrane fabrication conditions were optimized detailedly with respect to the morphologies, physicochemical properties, and FO performances. It is indicated that the PES concentration has great impacts on the morphology, thickness, and fiber diameter of the electrospun substrates and the optimal concentration is proved to be 26 wt %. After multilayered IP, the membrane thickness, surface hydrophilicity, and mechanical strength increased with IP cycles. The optimized FO membranes with two PA layers show much higher water flux and membrane selectivity compared with the commercial thin film composite membranes, holding great promise for water purification and seawater desalination. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47247.     

Comparative impact of SiO2 and TiO2 nanofillers on the performance of thin-film nanocomposite membranes

Nanoparticle (NP) additions can substantially improve the performance of reverse osmosis and nanofiltration polyamide (PA) membranes. However, the relative impacts of leading additives are poorly understood. In this study, we compare the effects of TiO₂ and SiO₂ NPs as nanofillers in PA membranes with respect to permeate flux and the rejection of organic matter (OM) and salts. Thin-film nanocomposite (TFN) PA membranes were fabricated using similarly sized TiO₂ 15 nm and SiO₂ (10 – 20 nm) NPs, introduced at four different NP concentrations (0.01, 0.05, 0.2, and 0.5% w/v). Compared with PA membranes fabricated without NPs, membranes fabricated with nanofillers improved membranes hydrophilicity, membrane porosity, and consequently the permeability. Permeability was increased by 24 and 58% with the addition of TiO₂ and SiO₂ , respectively. Rejection performance and fouling behavior of the membranes were examined with salt (MgSO₄ and NaCl ) and OM (humic acid [HA] and tannic acid [TA]). The addition of TiO₂ and SiO₂ nanofillers to the PA membranes improved the permeability of these membranes and also increased the rejection of MgSO₄ , especially for TiO₂ membranes. The addition of TiO₂ and SiO₂ to the membranes exhibited a higher flux and lower flux decline ratio than the control membrane in OM solution filtration. TFN membranes' HA and TA rejections were at least 77 and 71%, respectively. The surface change properties of NPs appear to play a dominant role in determining their effects as nanofillers in the composite membrane matrix through a balance of changes produced in membrane pore size and membrane hydrophilicity.     

Poly(vinylidene difluoride) Membrane Assisted by Modified ZnO/ZIF Nanoparticles for Membrane Distillation

Poly(vinylidene difluoride) (PVDF) polymeric membranes incorporated by synthesized hydrophobic agents were applied for membrane distillation. ZnO nanoparticles were modified with a silane coupling agent (n‐octyltriethoxysilane) and coupled by zeolite imidazole framework (ZIF)‐8 crystals. In particular, hydrophobic and porous membranes were prepared with ZIF crystals and modified ZnO/ZIF‐coupled nanoparticles. The influences of feed concentration and temperature of NaCl solution and seawater during filtration were evaluated. The hydrophobic modified membranes showed a higher permeate flux than pure PVDF membranes at different feed concentrations and feed temperatures. After modification, the porosity increased significantly and the contact angle became larger.     

Core–sheath nanofibrous membranes based on poly(acrylonitrile-butadiene-styrene), polyacrylonitrile,and zinc oxide nanoparticles for photoreduction of Cr(VI) ions in aqueous solutions

This investigation addresses the design of a series of poly(acrylonitrile-butadiene-styrene)/polyacrylonitrile–zinc oxide(ABS/PAN–ZnO) membranes by coaxial electrospinning. In the first instance, an optimization of ABS and PAN electrospinning was performed, thus establishing suitable compositional and processing parameters for obtaining homogenous fibers. Then, coaxial electrospinning of ABS and PAN solutions containing different amount of ZnO nanoparticles was carried out. The coaxial morphology of the nanofibers and ZnO distribution/dispersion were studied by the combination of several techniques such as scanning electron microscopy, X-ray energy dispersive analysis, contact angle, and thermogravimetric analysis. The performance of the obtained membranes for chromium (VI) ions removal from aqueous solutions was assessed by photoreduction using ultraviolet–visible spectroscopy. Electrospun mats composed of ABS (core)/PAN (sheath) embedded with 30 wt % of ZnO nanoparticles exhibited the highest chromium photoreduction (about 80%), suggesting the potential use of these membranes as filters for water purification. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48429.     

Fabrication of halloysite nanotubes embedded thin film nanocomposite membranes for dye removal

Environmental friendly Halloysite nanotubes (HNTs) are used to fabricate novel nanofiltration membranes by in situ interfacial polymerization of piperazine and trimesoyl chloride. The removal of excess amine solution from the porous support membrane surface is a critical step to obtain defect free active layer. Hereby, two main removal tools for the excess aqueous amine solution; a rubber roll or air knife are compared to fabricate a defect free thin film nanocomposite (TFN) nanofiltration (NF) membrane. Removal by the rubber roll is eventuated more favorable than air knife in terms of the reproducibility of NF membranes by comparing salt rejections. By determining the removal step of excess amines, various HNTs concentrations are used to fabricate NF membranes and, these membranes are tested with salt and dye solutions at various pH and temperature ranges. R2 membrane (containing 0.02% [w/v] HNTs) performs the best flux results beside higher rejections of MgSO₄ (93.0%) and dye (99.5%). To evaluate the extreme conditionals, further performance tests such as pH and temperature resistance are also performed for R2 membrane. Considering the performances of R2 membrane, HNTs can be demonstrated for tailoring the balance between flux and separation performance of NF membranes.