Search

In this work, a conductive thin film composite forward osmosis (TFC-FO) membrane was firstly prepared via vacuum filtering MXenes nanolayer on the outer surface of polyethersulfone membrane followed by interfacial polymerization in the other side. Moreover, its feasibility of mitigating organic fouling under electric field was evaluated. Results indicated that the addition of MXenes greatly reduced the electric resistance of membrane from 2.1 × 1012 to 46.8 Ω, enhanced the membrane porosity and promoted the membrane performance in terms of the ratio of water flux to reverse salt flux. The modified TFC-FO membrane presented the optimal performance with 0.47 g/m2 loading amount of MXenes. Organic fouling experiments using sodium alginate (SA) and bovine serum albumin (BSA) as representative demonstrated that the introduction of MXenes could effectively enhance the anti-fouling ability of TFC-FO membrane under the electric field of 2 V. The interelectron repulsion hindered organic foulants attaching into membrane surface and thus effectively alleviated the membrane fouling. More importantly, the modified TFC-FO membrane showed good stability during the fouling experiment of 10 h. In all, our work proved that introducing MXenes into the porous layer of support is feasible to alleviate organic fouling of FO membrane.

Thin-film composite polyesteramide nanofiltration membrane prepared from carboxylated chitosan and trimesoyl chloride was carefully tailored during its fabrication process of interfacial polymerization. The effects of post-curing, mid-drying and the addition of phase transfer catalysts on the membrane properties were studied using single-factor experiment. Post-curing was found to be effective in improving the separation performance of the membrane containing high concentrations of carboxylated chitosan, and the optimal post-curing effect was achieved at a temperature of 40 °C and curing time range of 15−20 min. Mid-drying enhanced the permeation flux and salt rejection of the membrane containing low concentrations of carboxylated chitosan, and the optimum temperature range for the mid-drying process was obtained at 30−40 °C. Furthermore, the membrane properties were susceptible to the addition of phase transfer catalysts, and a uniformly distributed phase transfer catalyst is vital to its influence on membrane properties. The addition of 0.025 wt% benzyltriethylammonium chloride to the aqueous solution exhibited the best effect towards the improvement of the separation performance of the produced membrane.

Solvent resistant nanofiltration (SRNF) is now a powerful tool for addressing environmental issues. Hence, we report the fabrication of a thin film composite (TFC) membrane comprised of a novel HDPE support, a polydopamine (PDA)/Tannic acid-Fe(III) interlayer and a polyamide (PA) skin layer. In this respect, high density polyethylene(HDPE)-polystyrene(PS)-styrene-ethylene-butylene-styrene(SEBS) blends were formed with different compositions by mixing via a Brabender machine and making films by using a hot press instrument. Next, a solvent extraction technique was employed for extracting the dispersed phase and making the HDPE membranes. The support membrane with optimum properties was coated with a PDA interlayer. A tannic acid-Fe(III) interlayer was also formed on the as-prepared PDA layer so that the hydrophilicity of the support surface was enhanced to form a defect-free PA layer. The modified support was utilized for the fabrication of the PA top layer by using m-phenylene diamine (MPD) and trimesoyl chloride (TMC) monomers. The prepared TFC membrane provided a significant dye rejection ability (99.9% Direct Yellow, 99.7% Methyl Green, 99.2% Rhodamine B, and 96.1% Methyl Orange), extraordinary solvent resistance ability in harsh solvents, and good methanol (MeOH) Flux (2.25 L/m2.h.bar) in SRNF applications. The skin-substrate adhesion strength of the top layer was also evaluated by a back-ward flush operation. It was demonstrated that the interlayer and the skin layer had an excellent adhesion with the support membrane.

Monoethylene glycol (MEG) aqueous solution was regenerated in the forward osmosis (FO) process for further use. For this purpose, a novel thin-film composite (TFC) membrane was prepared and applied. To mitigate the internal concentration polarization (ICP), a proper support with a low structural parameter and high hydrophilicity was utilized. In addition, a chlorine-tolerant polyamide layer was synthesized using trimesic acid trichloride (TMC) and 4-methyl-m-phenylenediamine (MMPD) monomers. The latter aimed to improve the chlorine resistance of the polyamide layer and increase the membrane lifespan in practical applications where oxidants are utilized for membrane cleaning. The effect of MMPD concentration and interfacial polymerization (IP) reaction time on the characteristics of the top layer was studied thoroughly. During the FO test, the TFC membrane whose polyamide layer was prepared with 2 wt. % MMPD concentration and 1.4 min reaction time exhibited the highest reverse flux selectivity at 5.71 L/g, while its water flux and MEG rejection during the regeneration of a MEG aqueous solution sampled from a gas processing plant were 35.40 LMH and 93.85%, respectively. The chlorine exposure test confirmed a significantly higher chlorine resistance for the MMPD/TMC polyamide layer compared to the conventional MPD/TMC one.

The performance of the existing forward osmosis membranes is mainly restricted by the internal concentration polarization (ICP) of solutes inside the substrate. In the current work, the poly (methyl methacrylate) (PMMA) grafted ZnO nanoparticle (ZnO@PMMA) was synthesized and introduced as a novel nanofiller to minimize the ICP effect within the polysulfone (PSf) support layer. It was revealed that the ZnO@PMMA nanoparticles could improve the characteristics of the PSf membrane substrate, including the porosity, hydrophilicity, pure water permeability (PWP) and morphology. The optimal support layer has a porosity of 82.4% and PWP of 186.5. The FO performance of modified membranes in terms of water flux (Jw, LMH) and reverse salt flux (Js, gMH) were thoroughly evaluated using a cross-flow system. Also, the water permeability (A, LMH.bar−1) and salt rejection (R, %) were measured by a dead-end RO setup. The obtained TFN-ZP.2 membrane (modified with 0.25 wt% of ZnO@PMMA) showed significantly improved FO water flux (up to 14.6 LMH) and water permeability (2.3 LMH/bar) which was about 2 times that of the bare TFC-FO membrane (5.9 LMH and 1.2 LMH/bar). Additionally, the structure parameter (S) was significantly alleviated (693 ± 85 µm) after the ZnO@PMMA incorporating, indicating reducing the unwanted ICP in TFN-FO membranes.

Membrane-based separation is an appealing solution to mitigate CO2 emission sustainably due to its energy efficiency and environmental friendliness. Attributed to its excellent separation endowed by nanomaterial incorporation, nanocomposite membrane is rigorously developed. This study explored the feasibility of boron nitride (BN) embedment and changes to formation mechanism of ultrathin selective layer of thin film nanocomposite (TFN) are investigated. The effects of amine-functionalization on nanosheet-polymer interaction and CO2 separation performance are also identified. Participation of nanosheets during interfacial polymerization reduced the crosslinking of selective layer, hence, improved TFN permeance while the formation of contorted diffusion paths by the nanosheets favors transport of small gases. Amine-functionalization enhanced the nanosheet-polymer interaction and elevated the membrane affinity towards CO2 which led to enhanced CO2 selectivity. The best TFN prepared in this study exhibited 37% and 20% increment in permeability and selectivity, respectively with respect to neat thin film composite (TFC). It is found that the CO2 separation performance of BN incorporated TFN is on par with many non-porous nanosheet-incorporated TFNs reported in literatures. The transport and barrier effects of BN and functionalized BN are discussed in detail to provide further insights into the development of commercially attractive CO2 selective TFN membranes.

The fabrication of chemically stable and high-permeance polymeric membranes, compatible with both polar and nonpolar solvents, for use in solvent filtration is reported. Herein, poly(divinylbenzene...

Water recycling is one of the most sustainable solutions to growing water scarcity challenges. However, wastewaters usually contain organic pollutants and often are at extreme pH, which complicates the treatment of these streams with conventional membranes. In this work, we report the synthesis of a robust membrane material that can withstand prolonged exposure to extreme pH (of 1 or 13 for 2 months). Polyamine thin film composite (TFC) membranes are prepared in situ by interfacial polymerization between 1,3,5-tris(bromomethyl)benzene (tBrMeB) and p-phenylenediamine (PPD). Contrary to conventional polyamide TFC membranes, enhanced pH stability is achieved by eliminating the carbonyl groups from the polymer network. The membranes showed pure water permeance and molecular weight cutoff (MWCO) of 0.28 ± 0.09 L m-2 h-2 bar-1 and 820 ± 132 g mol-1, respectively. The membrane performance is further enhanced by manipulating the monomer structures and replacing p-phenylenediamine with m-phenylenediamine, resulting in a higher permeance of 1.3 ± 0.3 L m-2 h-1 bar-1 and a lower MWCO of 566 ± 43 g mol-1. Given the ease of fabrication and excellent stability, this chemistry represents a step forward in the fabrication of robust membranes for industrial wastewater recycling.

Outer-selective thin film composite (TFC) hollow fiber membranes have the advantages of fiber blockage with less pressure drop and high surface area module. This work highlights novel strategies to design continuous interfacial polymerization that can allow mass production, performance controllability, and small margin of error in performance. Processing parameters were symmetrically optimized to maximize high water flux and salt rejection using poly(piperazine-amide) TFC membranes. For further improving the membrane performance, polyvinyl alcohol was incorporated for an interlayer, thereby having the water flux of 48 LMH/bar and the salt rejection (Na2SO4) of 99.6%. The system can be used in a variety of applications such as reverse osmosis, forward osmosis, or gas separations by simply replacing the monomers.

A new intrinsically and molecularly porous highly dense hyper-cross-linked polyamide thin film composite nanofiltration membrane was fabricated by incorporating graphitic carbon nitride (g-C3N4) nanosheets in the polyamide (PA) active layer through interfacial polymerization on the surface of ultrafiltration PSf/PET support (fabricated by phase inversion). The g-C3N4 nanosheets were fabricated through thermal pyrolysis and homogenously dispersed in an aqueous solution of a linear aliphatic tetra-amine prior to interfacial polymerization with non-aqueous solution of terephthaloyl chloride (TPC) and the fabricated membrane was named as g-C3N4/PA@PSf/PET membrane. The g-C3N4 nanosheets and g-C3N4/PA@PSf/PET membrane were thoroughly characterized by TEM, FE-SEM, FT-IR, Water contact angle (WCA), elemental mapping and EDX analysis. The FE-SEM of the g-C3N4/PA@PSf/PET membrane showed uniform and equal distribution of the g-C3N4 nanosheets in the polyamide active layer. In the crossflow nanofiltration performance test, the membrane showed a water flux of 55.71 L m-2h-1 and % rejection of >85 % of MgSO4 while the % rejection of Eriochrome Black T reached to > 99.5 % leading to clean and potable water as a permeate. The membrane followed the following trend of % rejection as MgSO4 > MgCl2 > Na2SO4 > CaCl2 > NaCl. This study shows that the incorporation of g-C3N4 nanosheets is an excellent option for enhancing the nanofiltration performance of the membranes.

In the forward osmosis (FO) processes, the semipermeable membranes are used. These membranes are prepared from several types of polymers. In this research, the characterizations of each polymer were studied to conversance the effect of polymer type on the efficiency of the forward osmosis process. The prepared membrane’s roughness was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM) to compare the formation of the TFC polyamide selective layer on each polymer type. Also, SEM images showed the distribution of pores on the prepared membrane. Contact angle (CA) measurements explained the hydrophilic and hydrophobic properties of membrane types. Finally, Energy dispersion spectrometry (EDS) was tested to determine the type, amount, and distribution of atoms in the prepared membranes. All of these characterizations proved that the Polysulfone (PSU) polymer was the best choice in the FO process. It can be proved that by test results, the PSU membrane gave the optimal water flux and salt rejection.

An innovative photocatalytic thin film nanocomposite (TFN) membrane was prepared and used for the simultaneous separation/degradation of methylene blue (MB) under UV irradiation. For this purpose, we used the sol-gel method to prepare the TiO2/MWCNTs nanophotocatalyst and added to the 1,3-phenylenediamine (MPD) solution during interfacial polymerization (IP) of 1,3,5-benzenetricarbonyl chloride (TMC) and 1,3-phenylenediamine monomers on the polysulfone (PSF) support. Using scanning electron microscopy (SEM) analysis and studying the cross-sectional images of membrane samples, it was revealed that the polyamide (PA) thin layer was well fabricated over the support membrane. The attendance of the TiO2/MWCNTs nanophotocatalyst in the PA thin layer of TFN samples was also proved using EDX (energy-dispersive X-ray) analysis. According to the results of the contact angle (CA), it is clear that the hydrophilicity of membrane samples first increased and then decreased by enhancing the TiO2/MWCNTs nanophotocatalyst content in the PA thin layer. In comparison with the pristine thin film composite (TFC) membrane, TFN samples showed higher water flux and MB removal when they were exposed to UV light. Finally, it turned out that the TFN membrane comprising 0.2 wt. % TiO2/MWCNTs nanophotocatalyst (TFN 0.2) had the foremost efficiency among TFNs with the water flux of 13 L/m2·hr and dye separation/degradation of almost 100% under UV irradiation.

Separation process based on polyamide (PA) thin film composite (TFC) membrane is the dominant desalination technology in the 21st century to produce potable water to meet the growing global freshwater demand. Despite offering good filtration performance and exhibiting stable chemical and mechanical properties, TFC membrane still encounters other technical challenges such as surface fouling and trade-off feature between water permeability and solute selectivity which prompt continuous research efforts. There has been growing interest in recent years among researchers to alter the surface properties of PA layer via various modification methods to overcome the drawbacks of typical selective layer. But the question that remains to be answered – Does the modified PA layer effective for performance improvement? It is the aim of this article to provide a comprehensive review on the modification techniques (i.e., surface coating, surface grafting, plasma treatment and layer-by-layer assembly) and the modifying materials (both organic and inorganic materials) that have been commonly employed to establish a functionalized layer atop PA layer to improve its characteristics for desalination process. We hope this review that covers the relevant articles published over the past 10 years could provide insights to scientists in modifying selective layer of TFC membranes for better performance in water treatment processes.

Polyamide (PA) Thin-Film Composite (TFC) membranes are widely used for large-scale water and wastewater treatment processes worldwide owing to their good balance between water permeability and dissolved solutes separation rate. The physicochemical properties of the cross-linked PA layer are the main criteria determining the filtration performance of the resultant TFC membrane, and this selective layer can be created through Interfacial Polymerization (IP) between two immiscible active monomers, i.e., amine monomer in aqueous solution and acyl chloride monomer in organic solution. This patent review article intends to provide insights to researchers in fabricating improved properties of TFC membranes through the utilization of secondary monomers during IP process. To the best of our knowledge, this is the first review that gives a state-of-the-art account of the subject matter by emphasizing the impacts of secondary monomers (both amine and acyl chloride monomers) on the properties of conventional TFC membranes for nanofiltration and reverse osmosis applications. Our review indicated that the introduction of secondary monomers into either aqueous or organic solution could alter the physical and chemical properties of PA layer, which led to variations in membrane filtration performance. Nevertheless, more research is still required, as most of the secondary monomers reported in the literature did not overcome the membrane trade-off effect between permeability and selectivity. The subject of improved PA layer development is a multi-disciplinary study that requires researchers with different backgrounds (e.g., materials science, chemistry, physics and engineering) to work together.

One of the most daunting challenges faced by the planet is a reliable and accessible supply of water in sufficient quantity. The membrane technology has emerged as a cost-effective alternative for water purification. One such pressure-driven membrane separation process is nanofiltration (NF), where the interfacial polymerization (IP) is predominantly used to prepare the thin polyamide selective layer. Over the last decade, a wide variety of novel/modified IP techniques have been explored to improve the performance of the polyamide (PA) thin-film composite and thin-film nanocomposite (TFN) membrane in both pressure-driven and osmotic driven applications. This paper explores different IP fabrication techniques viz. support-free IP technique, filtration-assisted IP technique, reverse IP technique, electrospray-based IP technique, etc. The thickness of the PA layer can be precisely monitored by many of these modified IP techniques. The incorporation of nanoparticles on the PA layer and membrane matrix could enhance the fouling resistance, increase the rejection efficiency and improve the water permeability. The efficiency of these membranes has been explored for the separation/removal of emerging contaminants, divalent/multi-valent ions, low molecular weight organics, micropollutants, and inorganic salts. Several advantages of these IP techniques are discussed in detail; however, the various associated challenges must be overcome before these techniques can be transferred from lab-scale to commercial applications.

Hollow fiber (HF) membranes are considered one of the emerging technologies in the field of membrane separation. It has undergone massive development for its various efficient applications during the past few decades. To further improve and develop the membrane technology, HF membranes have been fabricated for the nanofiltration (NF) process and found to yield higher efficiencies toward various environmental remediation applications. In this work, an elaborate discussion on the various fabrication methods and advantages of thin-film composite (TFC) NF HF membranes in the field of separation processes was listed. Moreover, the surface functionalization of such membranes to provide better separation efficiency is critically reviewed. The utilization of such thin-film HF membranes in several environmental remediation applications such as treating textile industry wastewater and other operations such as heavy metal removal, organic micropollutant removal, and inorganic salt removal has been explored in detail in this chapter. Further to this, the scope of improvements has been discussed in the conclusion section, which may enhance the overall efficiency of the thin-film composite NF HF membrane. This article will be much beneficial to the researchers for acquiring in-depth knowledge on the latitudes of various TFC HF fabrication methods, its functionalization, and wide ranges of promising environmental remediation applications.

Membrane separation has been widely used for various applications including microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) processes in the fields of biomedicine, food, and water purification. In this work, a facile synthesis of new polyamide thin-film composite nanofiltration membranes (NF-TFC) for water purification was described. The polyamide thin film was deposed over a synthetic cellulose acetate (CA) support by interfacial polymerization method. 1,3 cyclohexane bis (methylamine) (CHMA) and trimesoyl chloride (TMC) were used as monomers. The membranes were characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectroscopy (FT-IR), water uptake, porosity, contact angle, water permeability and rejection towards specific salt and dye molecules. The effect of the variation of the CHMA concentration (0.2–2 wt.%) on the morphology, porosity, water permeation and rejection properties of the prepared membranes was studied. SEM results displayed the growth of the membrane thickness when the CHMA concentration increased from 0.2 to 2 wt.%. The strong adhesion between the cellulose acetate substrate and the polyamide layer explained by the formation of the polyamide film in the substrate surface and inside the pores. The water permeability varied from 36.02 to 17.09 L h−1 m−2 bar−1. The salt rejection of Na2SO4 and NaCl increased from 9 to 68% and from 38.41% to 89.4%, respectively, when the CHMA concentration was changed from 0.2 to 2 wt.%. The prepared membranes were further applied successfully for the removal of malachite green and congo red. The results indicated that the maximum rejection reached 89% and 85% for malachite green and congo red, respectively.

The treatment of wastewater is an essential option to solve the water deficiency issue and can help inhibit the harmful effects of algal blooms and eutrophication in the urban water system. Municipal wastewater presents a high potential for water reuse as it is available in large quantity. Treatment with membrane technology presents advantages over other treatment methods due to the low treatment cost, unit operations reduction, and constant operation. The membrane bioreactor (MBR) process is practically used as the appropriate technique to treat municipal wastewater; nevertheless, it requires an advanced treatment of the effluent such as reverse osmosis (RO), as some of the contaminants are not removed. However, treatment of wastewater using RO results in membrane fouling which causes degradation and poor performance. This study aimed to minimise fouling of an aromatic polyamide thin film composite (TFC) RO membrane through the graft polymerisation of N,N'-dimethyl aminoethyl methacrylate (DMAEMA) by redox initiation with sodium metabisulfite and potassium persulfate. Biofouling tests using a bench-scale RO system with a secondary membrane bioreactor (MBR) effluent were used to assess the impact of surface modification. Significant changes in chemical and morphological structures were observed through attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis and scanning electron microscopy (SEM). The salt rejection decreased as DMAEMA concentration increased. Furthermore, the flux recovery ratio increased from 68.61 to 83.57% and the flux decline ratio decreased from 38.21 to 25.54%. The modified membrane’s sterilisation ratios were far higher than the unmodified membrane, thus showing better anti-biofouling properties when using Escherichia coli (E. coli) bacteria as model biofoulant. The DMAEMA modified membrane with the highest sterilisation ratio (76.8%) showed better anti-microbial properties against microorganism tested, obstruct growth and multiplication. This was further confirmed with the pure water flux test, where the unmodified and DMAEMA modified membranes declined by 46.0 and 37.3%, respectively.

A new class of a polyvinyl alcohol (PVA) hydrogel support was used to fabricate a forward osmosis (FO) membrane with high performance and excellent pH resistance. The intrinsically hydrophilic PVA support formed by non-solvent-induced phase separation and subsequent crosslinking exhibited a thin (∼40 μm) and highly porous scaffold-like structure with high pore interconnectivity, achieving a considerably low structural parameter (∼184 μm). Toluene-assisted interfacial polymerization was also employed to fabricate a polyamide (PA) selective layer with high water permeance and salt selectivity on the prepared hydrophilic PVA support. The fabricated PVA supported-thin film composite (PVA-TFC) membrane exhibited 2.7–3.7 times higher FO mode water flux and 70–78% lower specific salt flux than commercial FO membranes with a draw solution of 1.0 M NaCl and a feed solution of DI water. The PVA-TFC membrane also outperformed other previously reported FO membranes. In addition, the PVA-TFC membrane had superior pH resistance when compared with commercial FO membranes, which is imparted by the excellent pH stability of both its PA selective layer and PVA support. Our strategy paves the way for the fabrication of high-performance and pH-resistant FO membranes that can be employed in harsh water environments.

Interfacial polymerization of polyamide was conducted using hydrophobic and hydrophilic membrane support. The effects of monomer concentration were investigated, and the resulting thin-film composite membranes were tested for their performance in dye removal using different flow configurations. The results showed that a dense polyamide layer was successfully formed on the hydrophilic support, while a polyamide layer with a very loose structure was formed on the hydrophobic support. The polyamide layer became smoother and more hydrophilic as the concentration of trimesoyl chloride was increased, leading to increased permeate flux and reduced dye rejection. The highest sunset yellow rejection of 45.7% with a permeate flux of 4.9 L/m2.h was obtained when the polyamide layer was formed from trimesoyl chloride concentration of 0.05 w/v% (a high amine to acid chloride monomer ratio of 20) and the filtration was in cross-flow configuration.

In this study, we were able to impart antimicrobial properties onto the surface of a commercial thin-film composite (TFC) membrane using sustainably derived cellulose nanocrystals (CNC) extracted from elephant grass (Pennisetum purpureum) leaves. Carboxylic acid-containing CNC were chemically bound to the amine-terminated polyamide active layer of TFC membranes using a cross-linking reaction. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy were conducted to confirm the presence of CNC on the membrane surface. TFC membranes functionalized with needle-like and antimicrobial CNC nanoparticles showed robust toxicity to bacteria, inactivating ∼89% of attached Escherichia coli cells under contact. These findings establish that functionalization with CNC is a promising approach for mitigating biofouling on TFC membranes and substantiates the application of sustainable materials for the design of the next-generation membranes for water purification.

Polymeric membranes offer economic separation processes but are less explored for H2 separation application. This work aims to unveil the H2 separation potential of polymeric membrane by developing PVA-based reverse selective composite membrane. CO2-selective PEBAX was blended at different PVA:PEBAX ratio. The effect of PEBAX blending on membrane morphology, crystallinity and gas separation behavior was studied. Incorporation of PEBAX at 60 wt% PEBAX enhanced both permeance and selectivity of the resulted composite as the host matrix was dominated by this PEO containing material thus greatly enhancing polymer chain mobility and promoting CO2-solubility. The best composite which contains 60 wt% PEBAX exhibited CO2 permeability of 20.0 Barrer and CO2/H2 selectivity of 7.6. This performance surpasses the Robeson's boundary and unleashes the potential of tailoring the properties of polymeric nanocomposite membrane for H2 separation application through facile PVA/PEBAX blending.

2D Molybdenum disulfide (MoS2) nanoplatelets were synthesized via a green bottom-up strategy using non-toxic l -Cysteine as sulfur source. The hydrophobic MoS2 nanoplatelets assisted by hydrophilic 3-(3, 4-dihydroxyphenyl)-l-alanine ( l -DOPA) were coated on a thin film composite nanofiltration (TFC-NFG) membrane. The accelerated fouling experiments were conducted by using bovine serum albumin (BSA) as model organic foulant, and MoS2 coated membrane demonstrated excellent resistance with almost no flux decline within first hour of filtration, whereas the uncoated membrane showed flux decline immediately from the beginning of the experiment. After 5-hour filtration, the flux reduced by only 26% for MoS2 coated membrane with a higher flux recovery rate of 85.4% after washing by de-ionized (DI) water, whereas 45% flux decline was observed for uncoated membrane with lower flux recovery of 68%. These antifouling effects attributed by MoS2 coated membrane were underpinned by combined unique interfacial properties offered by 2D tri-atomic layered MoS2 morphology including dispersive surface tension, reduced surface roughness, weaker MoS2-foulant interactive forces, and negatively charged surface. This research positively confirms the role of 2D MoS2 nanoplatelets as an anti-fouling coating on membranes and brings up more possibility for applying other nanomaterials in 2D family in water applications such as desalination and water treatment.

Potable water has become a valuable, and sometimes, scarce resource due to population growth and industrial activities. Therefore, technologies that can process and generate this product are necessaries to avoid a global scenario of water scarcity in the following years. Reverse osmosis desalination using membranes is one of the most used strategies to produce potable water. However, polymeric membranes are susceptible to fouling and chlorine attack, which reduce their lifespan. Different approaches have been used to solve these problems such as the incorporation of nanocharges on the polymeric matrix of the membranes. In this work, the incorporation of graphene oxide on the polyamide membranes using different insertion routes was reviewed. The main results show that using graphene oxide as an additive for the thin film composite membranes, highly improves their performance in desalination systems as shown with the increase in 80% of the permeate flux while retaining salt rejection, besides, the addition of this nanocharge potentially increased chlorine resistance in 25%.

Osmotically assisted reverse osmosis (OARO) has become an emerging membrane technology to tackle the limitations of a reverse osmosis (RO) process for water desalination. A strong membrane that can withstand a high hydraulic pressure is crucial for the OARO process. Here, we develop ultra-strong polymeric thin film composite (TFC) hollow fiber membranes with exceptionally high hydraulic burst pressures of up to 110 bar, while maintaining high pure water permeance of around 3 litre/(m2 h bar) and a NaCl rejection of about 98%. The ultra-strong TFC hollow fiber membranes are achieved mainly by tuning the concentration of the host polymer in spinning dopes and engineering the fiber dimension and morphology. The optimal TFC membranes display promising water permeance under the OR and OARO operation modes. This work may shed new light on the fabrication of ultra-strong TFC hollow fiber membranes for water treatments and desalination., Osmotically assisted reverse osmosis can overcome limitations of the reverse osmosis process but a strong membrane which can withstand a high hydraulic pressure is crucial. Here, the authors develop strong polymer thin film composite hollow fiber membranes with exceptionally high hydraulic burst pressures of up to 110 bar, while maintaining high water permeance and salt rejection.

The successful synthesis of poly(aryl cyanurate) nanofiltration membranes via the interfacial polymerization reaction between cyanuric chloride and 1,1,1-tris(4-hydroxyphenyl)ethane (TPE), atop a polyethersulfone ultrafiltration support, is demonstrated. The use of cyanuric chloride allows for the formation of a polymer that does not contain hydrolysis-susceptible amide bonds that inherently limit the stability of polyamide nanofiltration membranes. In order to achieve a thin defect-free cross-linked film via interfacial polymerization, a sufficient number of each monomer should react. However, the reactivities of the second and third chloride groups of the cyanuric chloride are moderate. Here, this difficulty is overcome by the high functionality and the high reactivity of TPE. The membranes demonstrate a typical nanofiltration behavior, with a molecular weight cutoff of 400 ± 83 g·mol-1 and a permeance of 1.77 ± 0.18 L·m-2 h-1 bar-1. The following retention behavior Na2SO4 (97.1%) > MgSO4 (92.8%) > NaCl (51.3%) > MgCl2 (32.1%) indicates that the membranes have a negative surface charge. The absence of amide bonds in the membranes was expected to result in superior pH stability as compared to polyamide membranes. However, it was found that under extremely acidic conditions (pH = 1), the performance showed a pronounced decline over the course of 2 months. Under extremely alkaline conditions (pH = 13), after 1 month, the performance was lost. After 2 months of exposure to moderate alkaline conditions (pH = 12), the MgSO4 retention decreased by 14% and the permeance increased by 2.5-fold. This degradation was attributed to the hydrolysis of the aryl cyanurate bond that behaves like an ester bond.

OBJECTIVE: In this article, monomers (tannic acid (TA) and m- phenylenediamine (MPD)) were used in the fabrication of a novel PES based thin-film composite nanofiltration (TFC-NF) membrane for the treatment of a common effluent treatment plant (CETP) of textile industrial wastewater. MEMBRANE SYNTHESIS: PES support sheets and TFC layers were fabricated via non-solvent induced phase inversion and in-situ interfacial polymerization (IP) process. The ultra-thin active layer was synthesized via the IP process with monomers such as tannic acid (TA) and m- phenylenediamine (MPD). T and M series membranes correspond to (PES/x wt% TA, x = 2, 4, 6) as T1, T2, T3 -TA and (PES/x wt% MPD, x = 2, 4, 6) as M1, M2, M3–MPD respectively. M0 corresponds to PES which is the virgin membrane. RESULTS: The chemical structure, surface morphology, surface roughness and surface properties were explored using fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and contact angle, respectively. The filtration performance of the thin-film composite nanofiltration (TFC-NF) membranes was investigated by various properties like pure water flux, salt rejection, porosity, mean pore radius and antifouling analysis. CONCLUSION: T1-TA membrane showed better water permeability, high salt rejection and better industrial effluent rejection with 94.4% of TDS that are suitable for industrial reuse and agricultural irrigation. Moreover, for T1-TA membrane, the water flux, porosity, mean pore radius, salt rejection, surface roughness and contact angle of 43.5lm(− 2)h(− 1), 47.1%, 16.7nm, 72.7%, 11.7nm and 41.48°was achieved respectively that was found to be higher than that of all the other fabricated membranes. Further, the rejection efficiency rate of textile effluent characteristics such as pH, turbidity, TDS, alkalinity, total hardness, BOD and COD were also achieved with maximum deduction in the T1-TA TFC-NF membrane compared to the M0-Virgin PES membrane. From the results, it can be confirmed that the T1-TA membrane significantly reduced the alkalinity, total hardness, BOD and COD rejections of 78%, 77.3%, 58.5% and 67.5% respectively, present in the effluent. Water flux recovery ratio (FRR) was improved from 74.6% for M0-Virgin PES membrane to 94.8% for T1-TA membrane. The modified TFC-NF membranes especially T1-TA, had better anti-fouling property and excellent hydrophilicity than the unmodified M0-Virgin PES membrane. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40201-021-00624-x.

A novel low-cost polyvinyl chloride (PVC) membrane was synthesized by phase inversion and fast and facile bio-inspired technique was used for substrate modification of a thin-film composite (TFC) forward osmosis (FO) membrane. Using DI water as feed solution (FS) and 1 M NaCl as draw solution (DS), water flux (WF) ranging from 4.15 to 15.95 LMH and reverse salt flux (RSF) ranging from 0.87 to 3.50 gMH were produced when the dope polymer solution concentration decreased from 17 to 10 wt%. Then, the substrate with 10 wt% PVC was selected for modification and the substrate was coated by dopamine (DA) solution for 1 and 3 h to enhance the membrane hydrophilicity and facilitate interfacial polymerization. Compared to the pristine membrane, the 1 h polydopamine (PDA) modified membrane displayed higher WF (18.90 LMH) and lower RSF (3.35 gMH). Whereas, for the longer coating time, WF decreased (9.70 LMH) due to the membrane surface pores blocking by the PDA layer. Finally, for understanding whether the experimental data can be supported by a theoretical model, the obtained experimental results were compared with a developed computational fluid dynamics (CFD) model and the results showed acceptable agreement with each other. The results of this work introduce a low-cost and facile approach for FO membrane fabrication by utilizing PVC polymer and PDA coating.

The partitioning of solutes into the polyamide active layers of reverse osmosis (RO) membranes is a key membrane property determining solute permeation. Quantification of partition coefficients and their dependence on feed water pH would contribute to the development of predictive transport models of contaminant transport through RO membranes; however, neither solute partitioning nor the effect of feed solution pH on partitioning has been thoroughly characterized in the literature. Accordingly, we characterized the partitioning of all chloride salts of alkali metals (CsCl, RbCl, KCl, NaCl, and LiCl) from the aqueous phase into the polyamide active layers of five polyamide RO membranes, including one prepared in-house and four commercial membranes. We evaluated the effect of pH on the partitioning of alkali metal salts and whether the effect of pH on salt partitioning and rejection is consistent with Donnan theory predictions. Results showed that, for all membranes, the partition coefficients of all salts were less than one and did not differ substantially among RO membranes. Results also indicated that, for all membranes tested, Donnan theory provided an appropriate theoretical framework to estimate the effect of pH on salt partitioning (evaluated for all chloride salts of alkali metals) and salt rejection (evaluated for NaCl). Thus, we conclude that changes in salt rejection resulting from feed solution pH are primarily driven by changes in salt partitioning with comparatively small changes in salt diffusion coefficients.

A thin film composite (TFC) membrane with superior characteristics for organic solvent nanofiltration (OSN) was successfully prepared. Accordingly, a state-of-the-art polyethylene (PE) membrane sup...

Membrane fouling is a persistent problem that deteriorate membrane performance, impose additional cost for membrane cleaning and even membrane replacement. The objective of this work is to synthesis membranes that show high fouling resistance and demonstrate high membrane performance. Thin film composite nanofiltration membranes were fabricated through spin-assisted layer-by-layer assembly by depositing alternate layers of poly(diallyl dimethyl ammonium chloride) (PDAC) and poly(sodium 4-styrenesulfonate) (PSS) on polyethersulfone membranes as substrates. The membrane consisting of 35 layers of PDAC/PSS prepared from polyelectrolyte solution containing 0.05 M NaCl showed a rejection rate of 94.58% for MgCl2 and a permeability of 3.32 L/m2·h·bar during tests performed using a cross-flow permeation cell, MgCl2 concentration of 600 ppm, pressure of 10 bar, and temperature of 33 °C. The performance of the membranes with respect to organic foulant using a solution containing 20 mg/L bovine serum albumin showed approximately 10% decrease in permeation flux from the initial level within the first 24 h of testing, with the subsequent changes being only marginal for the next 72 h of testing. These results suggest that this new fabrication method is suitable for producing polyelectrolyte multilayered NF membranes that exhibit relatively high fouling resistance and excellent membrane performance.

Ammonium is known to be one of the most significant pollutants in water bodies. The presence of ammonium in water is mainly originated from agricultural activities, domestic sewage and industrial effluent. This study evaluates the performance of two commercial thin film composite (TFC) membranes, i.e., NF270 and XLE from FilmTec™ for ammonium removal using synthetic wastewater and domestic sewage. The filtration experiment was conducted at different feed ammonium concentrations, humic acid concentrations, pHs and pressure. Results showed that the membrane rejection against ammonium increased dramatically with increasing ammonium concentration. However, the membrane flux was slightly compromised at higher ammonium concentration. With respect to pH, highest ammonium removal rate was able to be achieved at an optimum pH of 10. Besides, the permeation flux increased gradually with increasing feed pressure. From the results, the XLE membrane outperformed the NF270 membrane in terms of ammonium rejection. The retentate of XLE membrane filtration process was found to be useful as liquid fertiliser for plant growth. The results indicated that the TFC membrane process is not only able to produce permeate with an ammonium concentration below the acceptable limit of 10 mg/L but also able to produce retentate with enriched ammonium for plant growth.

Polyurethane nanofibers recognized to perform as a sub-layer were employed herein as a medial-layer of high porosity in the fabrication of a novel class of thin-film nanofiltration membranes. In line with the primary aim of high throughput production of PU electrospun nanofibrous membranes (ENMs) with different fiber sizes and proper morphologies, the needle-free electrospinning technique was employed. An interfacial polymerization procedure was also utilized to conveniently coat a polyamide (PA) thin film on the polyurethane ENMs. The effects of the nanofibrous interconnecting network, fiber size, pore size, and morphology on the NF performance were investigated. The nanofiltration performance including the separation of various salts, water flux, and the MWCO test were performed. The results implied that the fiber size decrement, nanofibers interconnection increment, as well as nanofibrous membrane pore size decrement, and the nanofibrous layer increment (with different fiber size) would lead the interfacial polymerization to perfection and obtaining a uniform PA thin layer. The salts rejection and water flux of Na2SO4, MgSO4, MgCl2 and NaCl were (~ 99 ± 0.5 %, 37 ± 2.7 L/m2h), (~ 98 ± 1 %, 40 ± 1.5 L/m2h), (~ 95 ± 2 %, 33 ± 2 L/m2h) and (~ 52 ± 1 %, 30 ± 3 L/m2h), respectively. In the final analysis, a comparison of filtration performance between PU nanofibrous NF membranes with other well-known nanofibrous NF membranes was conducted.

This work aims to investigate the polyamide (PA) morphology on polysulfone (PSf) membrane supports with different morphologies. It was achieved by systematically varying the N-Methyl-2-Pyrrolidone (NMP) and Dimethylformamide (DMF) solvent composition ratios in dope solution as adapted in Tiraferri et al. The PSf membrane support was firstly synthesized via phase separation technique. Next, the PA layer of the thin film composite (TFC) membrane was synthesized via consistent interfacial polymerization parameters on the PSf membrane support. The PA layer over the resulting array of membrane supports was investigated on their surface wettability, top and cross-sectional morphologies, and performances. Result shows that with more NMP content in the dope solution produces thin and dense sponge-like top skin layer with intense extended finger-like macrovoids sublayer. Meanwhile, more DMF content in the dope solution produces thicker and dense sponge-like morphology on the top skin with finger-like pores underneath. A layer of smaller and loosen ridge-and-valley PA structures is formed on the thicker and dense sponge-like morphology. TFC membrane over support made of NMP to DMF (40:60) was observed had the highest hydrophilicity with the lowest contact angle measurement of 61.9 ± 3.1°. It also performed the highest water permeability of 4.06 LMH/bar, moderate salt rejection of 95.65% with salt permeability of 1.9 gMH.

Polyester thin film composite (PE-TFC) membranes featuring excellent chlorine-resistant property hold grand promise in seawater desalination and wastewater treatment. However, the low reactivity of alcohol or phenolic hydroxyl groups with acyl chloride groups usually leads to the formation of a relatively loose PE network, resulting in undesirable salt rejection. Preparing high-performance PE-TFC membranes remains a daunting challenge. In this study, we propose a thermal-facilitated interfacial polymerization (TFIP) approach to fabricate PE-TFC membranes with high desalination performance. The elevated temperature promoted the diffusion of glucose monomers across the water/heptane interface and then facilitated the reaction rate between glucose and TMC during interfacial polymerization (IP), resulting in the formation of PE layer with a higher cross-linking density compared to that fabricated via conventional IP. The PE membrane prepared via TFIP exhibited a superior ion rejection of 99.5% for Na2SO4 and high water permeance up to 16.1 L m−2 h−1 bar−1, outperforming all the polyester membranes with similar rejection in literature. The resultant PE-TFC membrane displayed unprecedented chlorine resistance (960 000 ppm h) and maintained separation efficiency after exposed to sodium hypochlorite solution (1000 ppm) for 36 days. Polyols including sucrose, raffinose and β-CD were also utilized as monomers, confirming the universality of the TFIP approach for facile preparation of high-performance desalination membranes.

This work reports a study on employing lignin in the formation of a selective layer of thin-film composite (TFC) membranes for pervaporation desalination. The TFC membranes with lignin-based separation layers are fabricated using a solution-casting method. With a reduction of the separation layer thickness to about 0.47 μm, a water permeation flux of 18.5 kg h−1 m−2 and a salt rejection of above 99.95% have been recorded on the lignin based TFC membrane with a feeding solution of 3.5 wt% NaCl(aq) at 45 °C. The membrane also exhibits high stability in long-term operation tests and can be applied for operations on high salinity water (up to 15 wt% NaCl(aq)). While being applied to seawater desalination, the membrane exhibits a water permeation flux of about 20.4 kg h−1 m−2 and a salt rejection of above 99.95% at 45 °C. A membrane separation process, which uses sustainable materials for salty wastewater treatments and water resource generation, has been demonstrated.

Chlorophenols are persistent pollutants posing environmental and health impacts. This work proposes a thin film nanocomposite (TFN) membrane with zeolitic imidazole frameworks (ZIF–8) for 2,4- Dichlorophenol removal from wastewater. Different characterization techniques were used to confirm the formation of the ZIF-8. The performance of the TFN membranes was assessed by pure water flux and rejection of 2, 4- Dichlorophenol, Glucose, NaCl. The TFN membrane with 0.05 wt% ZIF-8 showed highest pure water flux (14.52 ± 1.94 L/m2h), excellent rejection of glucose (90.72 ± 3.76%), NaCl (63.54 ± 1.64%) and 2, 4-Dichlorophenol (80 ± 5.03%).

Applying an interlayer of nanomaterial to the support layer during interfacial polymerization results in a change in the polyamide (PA) properties that can be leveraged to improve the performance of desalination membranes. While studies have shown that permeability and selectivity can be increased using an interlayer of nanomaterials, the potential of using this approach to improve the PA properties relevant for fouling and biofouling is less understood. In this study, we investigated how using an interlayer of alumina nanoparticles (Al-NP) to template the interfacial polymerization process affects the fouling and biofouling propensity of thin film composite membranes. Performance was measured by static bacteria and protein deposition assays as well as dynamic reverse osmosis biofouling experiments. The low and medium Al-NP loadings were found to reduce bacteria and protein adhesion while, at a high Al-NP loading, both bacteria and protein adhesion increased. A similar trend was observed in dynamic fouling conditions, with the low and medium Al-NP loadings experiencing less flux decline and lower biofilm volume on the membrane compared to the control or high Al-NP loaded membrane. The superior antifouling properties of these membranes were correlated with the change in the free energy of cohesion of the PA layer formed on the Al-NP interlayer. Our results demonstrate that using an interlayer of Al-NP can alter the PA surface chemistry in a way that reduces membrane fouling; however, there is a threshold loading of Al-NP beyond which fouling propensity increases due to the effect of Al-NP agglomeration on the PA morphology. These results provide useful insights into how NP can be added to the interlayer during interfacial polymerization to improve the performance of desalination membranes.