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Novel TFN membranes were examined for the removal of heavy metals (Cu and Pb) from synthetic wastewater in forward osmosis (FO) experiments using MgCl2 as a draw solute. The TFN membranes were fabricated on top of a commercial PS35 ultrafiltration membrane by in-situ interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride (TMC) containing different amounts of dispersed functionalized halloysite nanotubes (HNTs) nanoparticles. The HNTs nanoparticles were functionalized with the first generation of poly(amidoamine) (PAMAM) dendrimers. The TFN and the control TFC membranes showed rejections of Cu2+ and Pb2+, ranging from 94.5% to 98.1%. The presence of heavy metal in the feed solution enhanced the FO performance of all membranes. In particular, the reverse flux of MgCl2 decreased at least 2.5 times compared to the experiments with pure water as a feed. Simultaneously, the water flux also increased. The improved FO performance of the membranes in the presence of heavy metal ions is attributed to their adsorption by the membranes. The adsorption of heavy metals was confirmed by a decrease in the negativity of zeta potential and the results from inductively coupled plasma mass spectrometry (ICP-MS) of the membranes after the FO experiments.

In this study, two different methods were used to introduce functionalized graphene oxide (GO) onto the surface of nanofiltration (NF) membrane to improve its performance for heavy metal removal. The first method was based on coating in which the surface of NF membrane was coated with cross-linked GO, while the second method was introducing GO into monomer solution during interfacial polymerization. The efficiency of different methods was then compared by characterizing membrane physiochemical properties, as well as separation performance. With regard to performances, the water flux of TFN-i2 membrane (with GOs incorporated into thin layer) was reported to be 95 L/m2 h compared to 75 L/m2 h found in the TFN-c2 membrane (with GOs coated on the surface) at 8 bar. Both modified membranes exhibited higher water flux than the control membrane without GO incorporation (40 L/m2 h). Although the water flux of TFN-c2 membrane was lower, it achieved higher cobalt removal (97%) than that of TFN-i2 membrane (73%) due to its higher negative surface charge that improved separation via the Donnan exclusion effect.

In this study, a hybrid of nanofiltration (NF) and forward osmosis (FO) has been used with the aim of improving the efficiency of heavy metal removal. Here, black TiO2 nanoparticles (BNPs) were synthesized first and embedded in the polyamide (PA) active layer of TFC NF membrane to rectify the performance of membranes. The resulting TFN NF membranes were then tested in hybrid NF/FO system properly. The presence of BNPs was confirmed with XPS and FTIR, while the morphological alterations in the synthetized membranes were characterized using FESEM and AFM. Nanofiltration membrane performance was examined using multivalent ions such as of MgSO4, Na2SO4, CaCl2, and NaCl monovalent ion. We demonstrated that the addition of BNPs led to a significant decrease in surface roughness and hydrophilicity, showing a further reduction with increased concentrations of BNPs. In addition, TFC membrane showed a water flux of 25 L/m2h compared to 39, 41, and 66 L/m2h for TFN0.01, TFN0.05, and TFN0.1 membranes, respectively. We also showed that under the FO process, TFN membrane demonstrated the best performance with regards to heavy metal rejection and the highest Cr (III) and Pb (II) rejection was shown in TFN0.05 under the FO process. The ideal heavy metal rejections and acceptable water flux indicate the potential of these developed membranes under FO process for the removal of heavy metals from wastewater.

In this study, thin-film nanocomposite nanofiltration (TFN) membranes were fabricated using interfacial polymerisation by incorporating modified cellulose nanoparticles (mNCs). In the first place, ...

Reverse osmosis (RO) and nanofiltration (NF) membranes in spiral wound configurations have been widely used in food processing ranging from dairy to fruit juice for concentration, purification and recovering valuable components. In this work, intelligent systems, i.e., back-propagation artificial neural network (BPNN), radial basis function (RBF), fuzzy inference system (FIS) and adaptive Neuro-fuzzy inference system (ANFIS) were employed to predict the water flux and solute rejection of RO and NF membrane during concentration of licorice solution. To develop the intelligent systems, normalized membrane type, temperature, pressure, pH and cross-flow velocity are taken as inputs while normalized permeate flux and rejection are as outputs of the models. The proposed intelligent systems have been compared based on statistical parameters of the coefficient of determination (R 2 ) and the mean absolute error (MAE). The results indicate that the ANFIS model is more accurate and reliable compared to the BPNN, RBF and FIS approaches. It was found that the predictions using ANFIS model were usually in good agreement with the experimental data, showing the R 2 values within the range of 0.932–0.997 and the MAE values in the range of 0.01–1.7%. On the basis of comparison among the results obtained from this investigation, it is suggested that the ANFIS model could be potentially utilized to forecast the rejection and permeate flux of membrane during the concentration process of a licorice solution.

One of the major reasons for the limited commercial availability of the TFN membranes is the poor compatibility and adhesion between the embedded nanoparticles and polyamide matrix. Herein, we addressed this issue by functionalization of nanoscale additives to enhance their interactions with the polymer matrix and thereby reducing their leachability. Reverse osmosis TFN membranes were fabricated by in-situ interfacial polymerization of MPD and TMC, and incorporation of functionalized Halloysite Nanotubes (HNT). Exterior surfaces of the HNT were modified by adding three different functional groups: amine groups (HNT-NH2), the first generation of poly(amidoamine) (PAMAM) dendrimers (HNT-G1), and carboxylic acid (HNT-COOH). The modified HNT were characterized by ATR-FTIR, TEM, SEM, zeta potential, and thermogravimetric TGA analyses. Surface morphology and physicochemical properties of the HNT-based TFN membranes were investigated by SEM, ATR-FTIR, XPS, and contact angle measurements. Potential reactions of the functionalized HNT with TMC were investigated by ATR-FTIR. Also, the leachability of HNT from the membranes was studied by using a leaching test in a batch incubator followed by their tracing with ICP-MS. Furthermore, membrane selectivity and permeate flux were evaluated in cross-flow reverse osmosis (RO) desalination experiments using a synthetic brackish water. The water flux of all HNT-based TFN membranes compared to the reference TFC membrane increased without sacrifice of salt rejection. The maximum increase of nearly 100% was observed for HNT-COOH-based TFN membrane with salt rejection of 99.1% ± 0.1%. The TFN membranes with HNT-NH2 and HNT-G1 exhibited significantly lower leaching of nanoparticles in comparison to other TFN membranes. Decreased leachability of these membranes is attributed to the formation of covalent bonds between the amine groups of HNT-NH2 and HNT-G1, and the acyl chloride of TMC monomers.

A novel TFN membrane was fabricated by embedding Cellulose Nanocrystals (CNCs) into the polyamide active layer. Membranes were synthesized by in-situ interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) containing different amounts of CNCs. Successful incorporation of CNCs into the polyamide layer was confirmed by XRD analyses. Surface morphology of the membranes was characterized by SEM and AFM. Water contact angle measurements showed improved hydrophilicity of the TFN membranes. Desalination experiments with synthetic brackish water at 20 bar(g) revealed doubling of the water flux from 30 to 63 ± 10 L/m2·h, without significantly compromising the salt rejection (97.8%) for 0.1% (w/v) CNCs loading. In the fouling/filtration experiments with 300 ppm of Bovine Serum Albumin (BSA) in the feed solution, the TFN membrane had 11% smaller water flux reduction compared to the control TFC membrane. The promising performance of the CNCs-based TFN membranes and the fact that CNCs are inexpensive and abundant nanoparticles indicates their potential for a large-scale use in water desalination. Moreover, since CNCs are safe and environmentally friendly nanoparticles their possible leaching out during membrane operation would not impose health and environmental concerns.

For the first time, engineered osmosis was performed using commercial nanofiltration (NF) membranes for the treatment process of aerobically treated palm oil mill effluent (AT-POME). Compared to conventional forward-osmosis (FO) membranes with dense rejection layer, the NF-like FO membranes offer a higher water flux with minimum reverse solute flux provided appropriate solutes like divalent salts or polyelectrolytes were used in the draw solution. Both NF membranes were able to treat the AT-POME by completely preventing the color component from passing through the permeate side under FO and pressure-retarded osmosis (PRO) orientation. The water fluxes of the membranes were higher under PRO orientation owing to the reduced internal concentration polarization effect. Relatively loose membranes for the engineered osmosis application could address severe surface fouling of membranes tested under pressure-driven filtration.

In this work, a new type of mixed matrix membranes (MMMs) composed of dual-nanofillers at different ratios of hydrous manganese oxide (HMO) and titanium dioxide (TiO2) was fabricated with the objective of improving properties of polyethersulfone (PSF)-based membrane for oil-water separation process. The morphology and surface chemistry of the resultant MMMs were characterized by several analytical instruments, i.e., SEM-EDX, contact angle goniometer and FTIR spectrometer prior to separation performance evaluation using oily solution composed of 500 or 2000 ppm. The results showed that the membrane surface hydrophilicity was greatly improved upon addition of hydrophilic nanofillers and HMO in particular showed greater extent of hydrophilicity enhancement owing to the fact that it is associated with higher amount of OH functional groups compared to TiO2. The improved surface hydrophilicity coupled with formation of long finger-like voids in the membrane structure are the main factors leading to greater water flux of MMMs in comparison to control PES membrane. MMM2 (membrane made of HMO:TiO2 ratio of 0.75:0.25) and MMM4 (HMO:TiO2 ratio of 0.25:0.75) in particular were the best two performing nanofillers-incorporated membranes owing to their good balance between water flux and oil removal rate. They achieved 31.73% and 26.41% higher water flux than that of the control membrane without sacrificing oil removal rate. Most importantly, these nanofillers-incorporated membranes showed significantly lower degree of flux decline as a result of improved surface resistance against oil fouling and are of potential for long-term operation with extended lifespan.

In this work, nanocomposite ultrafiltration (UF) membranes were synthesized through addition of different quantities of amino-functionalized nanocrystalline cellulose (NCs) in order to improve membrane anti-fouling resistance against oil depositions. The characterization results demonstrated that the overall porosity and hydrophilicity of the membranes were improved significantly upon addition of NCs despite a decrease in the pore size of nanocomposite membranes. The UF performance results showed that the nanocomposite membrane incorporated with 1 wt% NCs achieved an optimal water flux improvement, i.e., approximately 43% higher than the pristine membrane. Such nanocomposite membrane also exhibited promising oil rejection (>98.2%) and excellent water flux recovery rate of ˜98% and ˜85% after one and four cycles of treating 250-ppm oil-in-water emulsion solution, respectively. The desirable anti-fouling properties of nanocomposite membrane can be attributed to the existence of hydrophilic functional groups (−OH) on the surface of membrane stemming from addition of NCs that renders the membrane less vulnerable to fouling during oil-in-water emulsion treatment.

The water sources contaminated by toxic dyes would pose a serious problem for public health. In view of this, the development of a simple yet effective method for removing dyes from industrial effluent has attracted interest from researchers. In the present work, flat sheet mixed matrix membranes (MMMs) with different physiochemical properties were fabricated by blending P84 polyimide with different concentrations of cadmium-based metal organic frameworks (MOF-2(Cd)). The resultant membranes were then used for simultaneous removal of eosin y (EY), sunset yellow (SY) and methylene blue (MB) under various process conditions. The findings indicated that the membranes could achieve high water permeability (117.8–171.4 L/m2.h.bar) and promising rejection for simultaneous dyes removal, recording value of 99.9%, 81.2% and 68.4% for MB, EY and SY, respectively. When 0.2 wt% MOF-2(Cd) was incorporated into the membrane matrix, the membrane separation efficiency was improved by 110.2% and 213.3% for EY and SY removal, respectively when compared with the pristine membrane. In addition, the optimization and modeling of membrane permeate flux and dye rejection was explored using response surface methodology. The actual and model results are in good agreement with R2 of at least 0.9983 for dye rejection and permeate flux. The high flux of the developed MMMs coupled with effective separation of dyes suggests a promising prospect of using P84 polyimide MMMs incorporated with MOF-2(Cd) for water purification.

Novel forward osmosis (FO) is a membrane-based separation process with significant potentials for low energy desalination. While this technology offers various benefits, overcoming its low water flux performance caused by internal concentration polarization (ICP) of solutes in porous substrates remains a challenge. This study aims at addressing this issue by introducing hydrophilic halloysite nanotubes (HNTs) into substrate made of polysulfone (PSF). The thin film nanocomposite (TFN) membranes suitable for FO applications were prepared via interfacial polymerization on the top surface of PSF-HNT nanocomposite substrates. The results obtained from filtration experiments showed that the TFN membrane prepared with 0.5 wt% HNTs (TFN0.5 membrane) demonstrated the most satisfactory results by exhibiting high water permeability and low reverse solute flux. Furthermore, TFN0.5 membrane exhibited remarkably higher water flux than that of control TFC membrane in both FO (27.7 vs 13.3 L/m 2 h) and PRO (42.3 vs 26.0 L/m 2 h) configurations when they were tested with 10 mM NaCl as feed solution and 2 M NaCl as draw solution. This improvement can be ascribed to the fact that the structural parameter of TFN0.5 is much lower compared to control TFC membrane (0.37 vs 0.95 mm), leading to reduced ICP effect.

In this work, titanate nanotubes (TNTs) were self-synthesized and amino functionalized to produce titanate nanotubes (NH2-TNTs) for thin film nanocomposite (TFN) reverse osmosis (RO) membrane fabrication. The novel RO membranes were fabricated by embedding NH2-TNTs of different quantities into polyamide (PA) layer. The nanotubular morphology of NH2-TNTs was studied using TEM while FTIR was employed to confirm the reaction of TNTs with [1-(2-amino-ethyl)-3-aminopropyl] trimethoxysilane. The effect of NH2-TNTs on the PA layer of TFN with respect to surface morphology, separation performance and antifouling properties was thoroughly investigated and discussed. The presence of NH2-TNTs in PA layer was verified using XPS while the “leaf-like” outgrowth morphology of PA layer was observed using FESEM. Results showed that the TFN membrane with 0.05% NH2-TNTs embedded was the most promising membrane as it exhibited 93% higher water flux than the control thin film composite (TFC) membrane, without compensating NaCl rejection. In terms of organic fouling tendency, the TFN0.05 membrane also showed higher tolerance compared to the control membrane during RO process. Furthermore, as high as 94% of the water flux of TFN0.05 was able to retrieve by a simple water rinse process, which suggests that organic fouling in TFN0.05 is highly reversible.

Antifouling properties of the polysulfone (PSf) and titanium nanotube (TNT) mixed matrix ultrafiltration membrane were investigated. The membrane was prepared by phase separation process using different concentrations of TNT and PSf. The pure water flux, protein removal and fouling parameters were studied to analyze the performance of the membrane. Morphology of the membrane was characterized by using scanning electron microscopy and atomic force microscopy. The most prominent observation was the significant improvement in water flux which attributed to improved hydrophilicity. The improvement of hydrophilicity was confirmed by water contact angle measurement and porosity measurements. This improvement in hydrophilicity is because of hydroxyl group present on TNT as determined by ATR-IR spectra. Fouling resistance of the membranes assessed by BSA solution filtration showed that 0.3 and 0.5 wt.% TNT loading membrane exhibited the best antifouling property that resulted in 100% flux recovery. The results also showed that 0.3 wt.% TNT loading membrane possessed the highest mean pore radius, porosity, and water flux. The effect of different washing directions in fouling experiment was reported. The perpendicular washing and parallel washing were carried out during fouling experiment and effects were discussed. The TNT nanocomposite membrane with parallel washing showed significant reusability during filtration.

An overview of the development of nanocomposite ultrafiltration (UF) membranes that are composed of organic polymer and inorganic nanomaterials for water treatment applications is provided in this chapter. Particular focus is placed on the roles of carbon-based nanomaterials embedded within the microporous membranes made via phase inversion technique for antifouling improvement and heavy metal removal. Compared to pristine membranes, the use of nanomaterials such as carbon nanotubes (CNTs) and graphene oxide (GO) to modify the surface morphology and chemistry of UF membranes was reported to have minimum adsorption and/or deposition of foulants, mainly due to the enhanced surface hydrophilicity coupled with greater charge properties that reduce the interaction between foulants and membrane surface. Such nanocomposite membranes also showed potential to be applied for heavy metal removal that is not possible to be achieved with pristine membranes. Compatibility between polymer and nanomaterials is not the main issue as most carbon-based nanomaterials are reported to distribute quite uniformly within the polymeric membranes, provided the loading used is at the appropriate range. This updated information is of great importance to provide good insights into the design and fabrication of advanced nanocomposite membranes for UF processes.

Electrospinning was used to fabricate beadless microfibrous polyacrylonitrile (ePAN) mats with an average fiber diameter of 1448 ± 380 nm from a 10 wt.% PAN in dimethylformamide (DMF) dope solution at applied voltage of 18 kV and 20 cm fiber collection distance. Urease (EC 3.5.1.5) was then covalently immobilized on dispersed microfibrous ePAN mats following the chemical treatment of fibers with ethylenediamine (EDA) and glutaraldehyde (GA). The optimal concentration of GA for immobilization was 5%. The amount of loaded urease reached 157 μg/mg mat, exhibiting 54% of the free urease activity. The surface chemistry of as-spun and chemically treated fibers was examined with Fourier transform infrared (FTIR) spectroscopy. Field emission scanning electron microscopy (FESEM) was used to study the morphology and diameter of the pristine, chemically treated, and urease-immobilized microfibrous mats. Immobilized urease showed increased temperature for maximum activity (from 37 to 50 °C for free and immobilized urease, respectively) and improved storage stability (20 days). The immobilized urease was also less sensitive to the changes in pH, especially in acid conditions. In addition, nearly 70% of initial activity of the immobilized urease was retained after 15 cycles of reuse, which proved the applicability of the electrospun fibers as successful enzyme carriers.

In this study, a new type of thin film nanocomposite (TFN) forward osmosis (FO) membranes was prepared by incorporating different quantities of halloysite nanotubes (HNTs) into the polyamide layer via interfacial polymerization. The FO performance of all fabricated TFN membranes in terms of water permeability and reverse solute flux was compared and the best performing membrane which showed good balance between permeability and solute flux, among all, was selected for further organic fouling investigation. Using 10 mM NaCl concentration in feed solution and draw solution of 2 M NaCl, the TFN membrane that was embedded with 0.05% HNTs (i.e. TFN0.05) was identified as the best performing membrane due to its high water permeability and low reverse solute flux. Confirmed by the results of BSA removal in the presence of Ca 2 + , the TFN0.05 membrane also exhibited significantly higher fouling resistance compared to a typical TFC membrane. As an indication to the TFN0.05 fouling reversibility, it was found that > 96% permeate flux could be recovered after a simple water rinse process. Overall, it can be concluded that the addition of an appropriate amount of HNTs into the polyamide layer can remarkably improve the antifouling affinity of conventional TFC membranes for FO applications.

Sulfonated poly (ether ether ketone) (SPEEK) membranes and their modifications are viewed as arguably the most promising in microbial fuel cell (MFC) applications due to their non-fluorinated base, superior chemical stability, and lower costs compared with Nafion membranes. In this work, SPEEK membranes with different degrees of sulfonation (DSs) (60% to 76%) and blended with charged surface modifying macromolecule (cSMM) were used as electrolytes in an MFC for simultaneous electricity generation and wastewater treatment. RESULTS: Performance evaluation of newly fabricated membranes was carried out and was compared with that of Nafion 117. The MFC with SPEEK76/cSMM generated about 16.5% higher maximum power density (172.1 mW m-2) than that with Nafion 117 (143.7 mW m-2). In addition, the SPEEK76/cSMM exhibited the highest coulombic efficiency (CE) of 17.6%, which was 21.6% higher than that of Nafion 117 (13.8%). Chemical oxygen demand (COD) removal of all characterized membranes was above 80% in our particular MFC. CONCLUSION: MFC is a suitable method for simultaneous wastewater treatment and electricity generation. SPEEK76/cSMM is a promising membrane to be applied in MFC. © 2014 Society of Chemical Industry.

A major limiting factor of forward osmosis (FO) membrane, particularly in pressure retarded osmosis (PRO) mode, is fouling by natural organic matters. In this work, we investigated the effect of the nanocomposite substrate on the fouling of a thin film nanocomposite (TFN) membrane due to organic foulants in PRO mode. The TFN membrane was synthesized by coating a polyamide film over the surface of substrate made of polysulfone–titanium dioxide. The TFN membrane always showed much higher FO water flux than the typical thin film composite TFC membrane prepared from the pristine polysulfone substrate. Reduced internal concentration polarization following a significant decrease of the structural parameter in the nanocomposite substrate causes the mass transfer coefficient of the substrate to increase. In the PRO mode, BSA removal in the presence of Ca2 + confirmed that the TFN FO membrane could significantly mitigate fouling tendency compared to a typical TFC membrane. Results also showed that fouling in TFN FO is highly reversible, recovering > 92% permeate flux after a simple water rinse process. A complete study of the membrane fouling was reported with detailed scientific discussion. To the best of our knowledge, this is the first report on the effect of the nanocomposite membrane on membrane fouling in PRO mode.

Dry–wet phased inversion method was used to fabricate polyvinylidene fluoride (PVDF) hollow fiber membranes. Different concentration of surface modifying macromolecules (SMM) i.e., 2, 4 and 6 wt.% were used as additives in the spinning dope. In the phase inversion SMM migrates to the membrane surface and changes the surface morphology with chemical properties on the membrane surface. This modification results into larger pore size, higher gas permeance, effective surface porosity and water contact angle. The surface modified membrane was used in membrane contactor for CO 2 stripping from water by using self-fabricated gas–liquid membrane contactor module. The result of CO 2 stripping experiment shows that the performance of surface modified membrane is better than plain PVDF membrane. CO 2 desorption flux increased with respect to SMM concentration, considerably. The membrane fabricated with 6 wt.% SMM as additive showed higher CO 2 desorption flux and efficiency of 2.1 × 10 −3 (mol m −2 s −1 ) and 80%, respectively at 200 ml/min of liquid flow rate. For this membrane CO 2 stripping flux was investigated for different liquid phase temperature. It was found that desorption flux increased by increasing liquid temperature and the highest stripping flux was obtained in the temperature of 90 °C. The enhancement of the gas flow rate increased the CO 2 desorption flux but this change was negligible.

In this work, a novel forward osmosis (FO)-ultrafiltration (UF) hybrid membrane is designed, constructed and its performance tested. The membrane consists of FO and UF membrane bilayer, between which highly concentrated sodium polyacrylate (SPAA) solution is sandwiched as a draw solution. When the FO side of the hybrid membrane is brought into contact with waste water, seawater or brackish water, clean water is drawn into the SPAA solution through FO membrane. The clean water is then squeezed out of the SPAA solution through the UF membrane by applying pressure, which can be either hydraulic or mechanical. Experiments were carried out to prove the validity of the design concept. Some model equations were derived to simulate the performance of the hybrid membrane and the experimental data were analyzed based on the model equations. The novel hybrid membrane is believed to allow the production of RO quality water at the UF pressure that is much lower than the pressure for RO, thus leading to significant reduction of energy consumption for water production.

In this work, polysulfone (PSf)–titanium dioxide (TiO2) nanocomposite substrates were prepared by incorporating different amounts of TiO2 nanoparticles (ranging from zero to 1 wt%) into PSf matrix. The nanocomposite substrates so prepared were then characterized with respect to hydrophilicity, overall porosity, surface roughness and cross-sectional morphology. It was found that both hydrophilicity and porosity of the substrate were increased upon addition of TiO2. In addition, long finger-like structures were developed by increasing the TiO2 loading, leading to water permeability enhancement. In order to fabricate thin film nanocomposite (TFN) membranes for forward osmosis (FO) application, a thin polyamide layer was formed by interfacial polymerization of 1,3-phenylendiamine and 1,3,5-benzenetricarbonyl trichloride on the top surface of PSf–TiO2 nanocomposite substrates. Under the conditions for FO performance evaluation (10 mM NaCl concentration in feed solution, 0.5 and 2.0 M NaCl concentration in draw solution, and both active layer facing the feed solution (AL–FS) and active layer facing the draw solution (AL–DS) orientations), the TFN membrane prepared using PSf substrate embedded with 0.5 wt% TiO2 nanoparticles (denoted as TFN0.5) exhibited the most promising results by showing high water permeability and low reverse solute flux. In comparison with control TFC membrane, the water flux of TFN0.5 membrane was improved by 86–93%, depending on the membrane orientation and draw solution concentration. The increase in water permeability can be attributed to decrease in structural parameter which resulted in decreased internal concentration polarization (ICP). Although further increase in TiO2 nanoparticles loading to 0.75 and 1 wt% could result in higher water permeability, their FO performances were compromised by a significant increase in reverse solute flux. Based on the results obtained in this work, it can be concluded that adding an appropriate amount of TiO2 nanoparticles into PSf substrate could potentially improve the performance of TFC membrane during FO applications.

Realizing that one of the most important challenges in the forward osmosis (FO) membrane is internal concentration polarization (ICP), thin film nanocomposite (TFN) membranes were prepared by incorporating different loadings of titanium dioxide (TiO 2 ) nanoparticles (ranging from 0 to 0.90 wt%) into the polysulfone (PSf) substrate in order to reduce ICP. The nanocomposite substrates prepared were characterized with respect to hydrophilicity, overall porosity, surface roughness and cross-sectional morphology by different methods. Results revealed that both hydrophilicity and porosity of the substrate were increased upon addition of TiO 2 nanoparticles. Moreover, a large number of finger-like macrovoids were developed by increasing the loading of TiO 2 nanoparticles, leading to enhancement in water permeability. As for the FO performance tested at AL-FS orientation and with DI water as feed and 0.5 M NaCl as draw solution, the TFN membrane prepared using PSf substrate embedded with 0.60 wt% TiO 2 nanoparticles (designated as TFN0.60) exhibited the most promising result by showing water flux of 18.81 L/m 2 h, i.e. 97% higher than the control TFC membrane prepared by substrate without TiO 2 incorporation (designated as TFC), with no significant change in reverse solute flux. Compared to the control TFC membrane, the FO water flux of TFN0.60 was also reported to increase significantly from 4.2 to 8.1 L/m 2 h (AL-FS orientation) and from 6.9 to 13.8 L/m 2 h (AL-DS orientation) when seawater was used as feed solution and 2 M NaCl was used as draw solution. The increase in water flux can be attributed to the decrease in structural parameter ( S value=0.39 mm), mainly due to the formation of finger-liked macrovoids that connect the top and bottom layer of the substrate and reduce the tortuosity, resulting in decreased ICP. Although further increasing TiO 2 nanoparticles loading to 0.90 wt% could increase membrane water permeability, the FO performance was compromised by a significant increase in reverse solute flux. To the best knowledge of the authors, this is the first report on TFN membrane using PSf-TiO 2 nanocomposite substrate for FO applications.

Surface Modifying Macromolecule (SMM) blended PSf hollow fibers were spun at different air-gaps to evaluate CO2 stripping from aqueous DEA solution and water. The fabricated membranes were firstly subjected to different characterization methods such as contact angle and liquid entry pressure measurement to evaluate the membrane's hydrophobicity and wetting resistance, respectively. To determine pore size and effective porosity of the membranes, a pure helium permeation test was performed. Morphological study of the membranes was conducted by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A CO2 stripping test was carried out to investigate the effects of operating variables such as liquid and gas velocity, temperature and DEA concentration on the CO2 stripping flux. It was found that the increase of liquid velocity resulted in enhanced CO2 stripping flux. On the other hand, the increase in gas velocity did not exert significant influence on the stripping flux. The increase in temperature and DEA concentration both enhanced the stripping flux. Lastly, it was concluded that the hollow fibers spun in this work at a 15 cm air-gap could achieve the best stripping flux among all the membranes fabricated so far for CO2 stripping.

In this study, thin film nanocomposite (TFN) membrane was developed using novel polysulfone–titanium dioxide (PSf–TiO 2 ) nanocomposite substrate. The effects of TiO 2 on the PSf substrate morphologies, hydrophilicity and water permeability were investigated and discussed. The results revealed that the hydrophilicity and the porosity of the substrate were improved upon the TiO 2 addition, leading to significant enhancement in water flux. TFN membrane was then fabricated by establishing a polyamide layer made of 1,3-phenylendiamine and 1,3,5-benzenetricarbonyl trichloride monomers over the surface of the modified substrate. Compared with the typical TFC and commercial CTA membranes, the TFN membrane prepared always demonstrated much higher FO water flux without showing a significant increase in reverse solute flux when tested under same conditions. When tested in AL–FS orientation using 0.5 M NaCl as a draw solution and 10 mM NaCl as feed solution, the water flux of the TFN membrane was ∼ 120% and ∼ 87% higher than that of the commercial membrane and typical TFC membrane, respectively. The water flux of the TFN membrane was also reported to be much higher under prolonged filtration time, mainly due to the improved properties of substrate upon addition of TiO 2 .

Surface modified polyvinylidene fluoride (PVDF) hollow fiber membranes were fabricated via a dry–wet phased inversion process. Surface modifying macromolecules (SMMs) (0, 2, 4 and 6 wt.%) were used as additives in the spinning dope. During phase inversion SMM migrates to the membrane surface, resulting in different surface morphology and surface chemistry. The surface modified PVDF membranes showed the larger pore size, higher gas permeance, effective surface porosity, contact angle and overall porosity but lower critical water entry pressure compared to the PVDF hollow fiber membrane without SMM. The performance of the surface modified membrane in contactor application for physical CO 2 absorption was investigated by the fabricated gas–liquid membrane contactor module, where distilled water was used to dissolve CO 2 . It was found that the liquid phase resistance was dominant in the absorption experiment. The results show that the surface modified PVDF membrane has a higher performance compared to control PVDF membrane. By increasing SMM concentration in the spinning dope, the CO 2 absorption flux increased significantly. With the membrane prepared from 6 wt.% of SMM in the spinning dope, a maximum CO 2 absorption flux of 5.4 × 10 −3 mol/m 2 s was achieved at 300 ml min −1 of absorbent flow rate, which was almost 650% more than the fabricated membrane without SMM.

Carbon dioxide (CO2) stripping from water was conducted through the porous asymmetric polysulfone (PSf) hollow fiber membrane contactor. The effect of the liquid and gas flow rates on the stripping performance, the liquid phase CO2 concentration and the CO2 stripping efficiency of the membrane module and the effect of liquid phase temperature on CO2 stripping flux were studied. The experimental results showed that the stripping gas velocity had a minor effect on the CO2 desorption flux while the increase in the liquid velocity could enhance CO2 desorption flux in the gas stripping membrane contactor. By increasing liquid flow rate to 200 ml/min, the maximum CO2 stripping efficiency of almost 66% was achieved. Enhancement of liquid flow rate from 50 to 200 ml/min increased the CO2 flux around 482%. It was found that the CO2 stripping flux was significantly affected by the liquid phase temperature. By increasing liquid temperature from 80 to 90 °C, the CO2 stripping flux increased from 1.3 × 10−4 to 4.9 × 10−4 mol m−2 s−1 at liquid velocity of 200 ml min−1. Hence, the higher stripping efficiency can be achieved by applying the higher liquid flow rate in the membrane contactor module. As well, the liquid phase temperature is a key parameter that needs to be controlled.

In order to fabricate hollow fiber mixed matrix membrane (HFMMM) for long-term CO2 absorption process, ZSM-5 (Zeolite Socony Mobil–5) zeolite was modified using hexadecyltrichlorosilane for increasing hydrophobicity and then added to the polyvinylidene fluoride (PVDF) spinning dope. The in-house made HFMMMs were characterized in terms of gas permeance, overall porosity, average pore size, effective surface porosity, surface roughness, mechanical stability, and wetting resistance. The morphology of the HFMMMs was studied using SEM. The cross-sectional SEM images indicated that the membrane structure has changed from sponge-like to finger-like by ZSM-5 loading. The surface roughness increased by increasing ZSM-5 concentration in the spinning dope. The HFMMM spun from the spinning dope with 0.5 wt % of ZSM-5 zeolite showed that the CO2 absorption flux decreased 18.9% in the initial 115 h of the operation and then the absorption flux remained constant until the end of the operation. For plain PVDF HFM the absorption flux decreased 36% from the initial value in the first 15 h of the experiment. Thus it could be concluded that the long term stability of HFM was improved by the incorporation of ZSM-5. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44606.

The membrane technology is still considered a costly method to produce potable water. In view of this, RO membrane with enhanced water permeability without trade-off in salt rejection is desirable as it could further reduce the cost for water desalination. In this study, thin film nanocomposite (TFN) membranes containing 0.05 or 0.10 w/v% hydrophilic nanofillers in polyamide layer were synthesized via interfacial polymerization of piperazine and trimesoyl chloride monomers. The resultant TFN membranes were characterized and compared with a control thin film composite (TFC) membrane. Results from the filtration experiments showed that TFN membranes exhibited higher water permeability, salt rejection and fouling resistance compared to that of the TFC membrane. Excessive amount of nanofillers incorporated in the membrane PA layer however negatively affected the cross-linking in the polymer matrix, thus deteriorating the membrane salt rejection. TFN membrane containing 0.05 w/v% of nanofillers showed better performances than the TFC membrane, recording a pure water flux of 11.2 L/m2∙h, and salt rejection of 95.4%, 97.3% and 97.5% against NaCl, Na2SO4 and MgSO4, respectively.

In this study, nanoporous titanate (NT) nanoparticle synthesized by the solvothermal method was used to modify polyamide layer of thin film composite membranes with the aim of improving membrane resistances against organic and inorganic fouling. Thin film nanocomposite membranes (NMs) were synthesized by adding mNTs (modified nanoparticles) into polyamide selective layer followed by characterization using different analytical instruments. The results of XPS and XRD confirmed the presence of mNTs in the polyamide layer of NMs, while FESEM, AFM, zeta potential and contact angle measurement further supported the changes in physical and chemical properties of the membrane surface upon mNTs incorporation. Results of fouling showed that NM1 (the membrane incorporated with 0.01 w/v% mNTs) always demonstrated lower degree of flux decline compared to the control membrane when membranes were tested with organic, inorganic and multicomponent synthesized water, brackish water or seawater. Besides showing greater antifouling resistance, the NM also displayed significantly higher water flux compared to the control M membrane. The findings of this work confirmed the positive impact of mNTs in improving the properties of NM with respect to fouling mitigation and flux improvement.

In this research, novel ultrafiltration nanocomposite membranes were prepared by incorporating self-synthesized nanoporous titanium dioxide (NTiO2) nanoparticles into polysulfone. The surface of the nanoparticle was treated with a silane-based modifier to improve its distribution in the host polymer. Atomic-force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller, transmission electron microscopy, energy-dispersive x-ray spectroscopy, porosity and contact angle tests were conducted to characterize the properties of the particles as well as the fabricated nanocomposite membranes. The effects of the nanoparticle incorporation were evaluated by conducting ultrafiltration experiments. It was reported that the membrane pure water flux was increased with increasing NTiO2 loading owing to the high porosity of the nanoparticles embedded and/or formation of enlarged pores upon addition of them. The antifouling capacity of the membranes was also tested by ultrafiltration of bovine serum albumin fouling solution. It was found that both water flux and antifouling capacity tended to reach desired level if the NTiO2 added was at optimized loading.

This review focuses on the development of polyamide (PA) thin film nanocomposite (TFN) membranes for various aqueous media-based separation processes such as nanofiltration, reverse osmosis and forward osmosis since the concept of TFN was introduced in year 2007. Although the total number of published TFN articles falls far short of the articles of the well-known thin film composite (TFC) membranes, its growth rate is significant, particularly since 2012. Generally, by incorporating an appropriate amount of nanofiller into a thin selective PA layer of a composite membrane, one could produce TFN membranes with enhanced separation characteristics as compared to the conventional TFC membrane. For certain cases, the resulting TFN membranes demonstrate not only excellent antifouling resistance and/or greater antibacterial effect, but also possibly overcome the trade-off effect between water permeability and solute selectivity. Furthermore, this review attempts to give the readers insights into the difficulties of incorporating inorganic nanomaterials into the organic PA layer whose thickness usually falls in a range of several-hundred nanometers. It is also intended to show new possible approaches to overcome these challenges in TFN membrane fabrication.

In the present study, the self-synthesized thin film nanocomposite (TFN) membrane incorporated with hydrophilic functionalized titanate nanotubes (TNTs) has been fabricated and tested for forward osmosis (FO) desalination. The ATR-FTIR results showed that NH 2 -TNT S were successfully modified by AATPS and while TEM and XRD revealed the tubular morphology and crystal structure of NH 2 -TNTs nanotubes, respectively. The presence of the chemical bondings between NH 2 -TNTs and polyamide (PA) selective top layer of TFN is corroborated with the FTIR results. The existence of NH 2 -TNTs in PA top layer was further confirmed by XPS analysis on the control and TFN membranes. The effect of NH 2 -TNTs on the PA layer was investigated and discussed in terms of surface morphology and separation performance. The morphology of the PA layer was investigated through FESEM and AFM micrographs and the outgrowth of the “leaf-like” structure was observed following the increase in NH 2 -TNTs content. Compared to the thin film composite (TFC) control membrane, the TFN membrane embedded with 0.05 wt% NH 2 -TNTs (designated as TFN0.05) exhibited two times improvement in water flux without sacrificing salt rejection.

In the current study, the impact of self-synthesized nanoporous titanium oxide (NT) on the morphology, performance and fouling of a polyamide (PA) thin-film composite (TFC) membrane was investigated when the membrane was applied for engineering osmosis (EO). The nanoporous structure and the spindle-like shape of NT were revealed through transmission electron microscopy (TEM), while the AATPS modification of NT was verified by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The results of x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) confirmed the presence of modified NT (mNT) in the PA dense active layer of the TFC membrane. The outgrowth of the 'leaf-like' structure, upon mNT loading, at the surface of the PA layer was observed by field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The TFC membrane prepared with 0.05 wt% mNT loading in the organic phase showed the water flux of 26.4 l m(-2) h(-1) when tested in the forward osmosis (FO) mode using 0.5M and 10 mM NaCl solution as the draw and feed solution, respectively. Moreover, the TFC-mNT membrane also demonstrated an intensified antifouling property against organic foulant during FO application and it was possible to retrieve the initial water flux almost completely with a simple water-rinsing process.