Thin Film Composite Nanofiltration Membranes Research Articles

Positively charged thin film composite nanofiltration membrane via layer-by-layer interfacial polymerization based on PU nanofibrous support

Positively charged Nanofibrous nanofiltration (NF) membranes were prepared via multi-step interfacial polymerization from polyethylenimine (PEI) and terimesoyl chloride (TMC) on a polyurethane (PU) nanofibrous support. In this way, electrospinning technique was applied for preparation of the PU nanofibrous support and at the following, NF membranes were formed via layer-by-layer interfacial polymerization and the cycle of sequential depositions. The nanofibrous NF membranes were characterized using ATR-FTIR, surface charge, morphology, MWCO, capillary flow porometery and NF performance techniques. Moreover, the effect of the reaction cycle number on NF performance was evaluated. The result of NF membrane prepared by three cycles of reactions with 1.5 wt% PEI and 0.5 wt% TMC presented appropriate salt rejection and flux; 99.1% for MgCl2, 82.3% for MgSO4, 81% for NaCl and 57.1% for Na2SO4 and electrolyte permeate flux; 70 L/m2 h for MgCl2, 73 L/m2 h for MgSO4, 72 L/m2 h for NaCl and 74 L/m2 h for Na2SO4 under filtration pressure of 8 bar. At the end, the performance of positively TFNC-NF membrane was compared with other positively nanofiltration membranes.

Facile fabrication of high performance nanofiltration membranes for recovery of triazine-based chemicals used for H2S scavenging

The synthesis of tailormade thin-film composite (TFC) nanofiltration (NF) membranes produced by interfacial polymerization is presented for the separation of unspent (MEA-triazine) and spent (DTZ) H2S scavengers obtained from an oil and gas wastewater from an offshore installation in the North Sea. The physicochemical properties, thermal stability, and hydrophilicity of the synthesized TFC membranes were investigated using SEM, FTIR, XRD, TGA, and contact angle. Filtration layer thicknesses from 25 to 400 µm were investigated and the optimal value (100 µm) was determined, based on the efficiency in the separation and the water permeability. Operating at 50% permeate recovery, rejections for MEA-triazine and monoethanolamine of 62% and 82%, respectively, were obtained, with zero rejection for DTZ. In 24 h batch recirculation tests, the water permeability remained stable at 6 L/(m2·h·bar), indicating insignificant fouling with 13 times higher compared to the 0.45 L/(m2·h·bar) achieved by the commercial NF270 membrane under comparable conditions. The results indicate that the NF of mixtures of spent/unspent H2S scavengers using tailored membranes is a promising strategy for recovering MEA-triazine, thus reducing costs for offshore oil and gas operators, while reducing the environmental impact associated to the discharge of this wastewater.

Preparation of high permeance thin-film composite nanofiltration membrane on macroporous ceramic support

Thin-film composite (TFC) nanofiltration (NF) membranes have been widely used in water purification processes. In harsh conditions, however, the application of TFC membrane was limited by selectivity loss because of swelling or dissolution. In this study, a defect-free polyamide (PA) layer was directly prepared on a tubular alumina ceramic membrane with a pore size of 100 nm to compensate these shortcomings. The ceramic support, owing to its superior hydrophilicity, showed excellent affinity with aqueous diamine monomers, preventing defects caused by large pore sizes. Besides, the narrow aperture distribution of support is conductive to control the water-oil interface at an appropriate position that the active layer can form near the support by simple air-drying. Different morphologies and performances were easily obtained by changing the monomer concentration and reaction time. The resulting organic–inorganic composite membrane exhibited pure water permeance of 21.7 LMH/bar and desirable rejection to Na2SO4 of 99.0%. Moreover, the prepared NF membrane showed satisfactory compaction resistance at pressure from 2 to 12 bar owing to the excellent mechanical strength of the support. The inorganic support also endowed the TFC membrane with good performance stability even at 75 °C and after soaking in different organic solvents for one week.

Regulation of interfacial polymerization process based on reversible enamine reaction for high performance nanofiltration membrane

The regulation of interfacial polymerization (IP) is the critical procedure for the preparation and industrialization of thin film composite (TFC) nanofiltration (NF) membranes. However, the IP control is still a huge challenge based on the extremely rapid reaction rate during the fabrication of the membrane. Herein, a new strategy was developed to modulate the IP process to increase the NF membrane performance. The aldehyde oxidized dextran (ODex) interlayer was deposited on the polysulfone ultrafiltration substrate, and the enamine would form between the secondary amines of aqueous phase monomer piperazine (PIP) and aldehyde groups of the ODex. Based on the by-products of IP, the enamine gradually decomposed reversibly in a hydrogen ion environment and the immobilized PIP was released and continued to react with organic phase monomer trimesoyl chloride (TMC). Accordingly, a thinner and exhibiting nanowire structures separation layer with fewer defects was obtained. The permeance of the optimal NF membrane with 0.7 wt% ODex interlayer deposition concentration could reach up to 208 ± 10.4 Lm−2h−1MPa−1, which was more than 2.5 times permeance of the ordinary NF membrane, and the rejection rate for Na2SO4 could reach 99.3 ± 0.3%. In addition, the mono- and divalent ion selectivity of the modified membrane was also greatly improved (αNaCl/Na2SO4 = 115). This study provides a new idea for the regulation of IP process, thereby suggesting a reasonable proposal for improving the performance of TFC NF membranes.

Fabrication of anti-fouling polyamide nanofiltration membrane by incorporating streptomycin as a novel co-monomer

Polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membrane has extremely broad application prospects in separation of monovalent/divalent inorganic salts mixed solution. However, membrane fouling is the main obstacle to the application of PA TFC NF membrane. Streptomycin (SM) is a hydrophilic antibiotic containing a large number of hydroxyl and amino groups. In this work, the NF membrane was prepared via interfacial polymerization (IP) between trimesoyl chloride (TMC) in the organic phase and SM/piperazine (PIP) mixture in the aqueous phase. The NF membrane structure and performance were characterized in detail. The results showed that SM successfully participated in the IP. The negative charge and hydrophilicity of membrane surface were improved. The prepared membrane exhibited good anti-adhesion and anti-bacterial performance. Additionally, when the SM concentration was 2%, the prepared membrane exhibited the optimal permselectivity. The water permeance was 89.4 L·m –2 ·h –1 ·MPa –1 . The rejection of NaCl and Na 2 SO 4 were 17.17% and 97.84%, respectively. The NaCl/Na 2 SO 4 separation factor of the SM2-PIP/TMC membrane in 1000 mg·L –1 NaCl and 1000 mg·L –1 Na 2 SO 4 mixed solution was 40, which was 3.3 times that of PIP/TMC membrane. It indicated that SM2-PIP/TMC demonstrated excellent monovalent/divalent salts separation performance. This work provided an easy and effective approach to preparing anti-fouling NF membrane while possessing superior monovalent/divalent salts separation performance.

Exploiting interfacial polymerization to fabricate hyper-cross-linked nanofiltration membrane with a constituent linear aliphatic amine for freshwater production

Humanity is facing a global challenge of dwindling water resources and the situation is intensifying due to growing population leading to excessive water pollution. Nanofiltration is an important membrane-based technology for the production of clean and potable water for domestic and industrial setups. Hyper-cross-linked polyamide thin film composite nanofiltration (HCPA-TFC-NF) membranes have been fabricated by using multifunctional amine 1 (possessing two primary -NH2 and two secondary -NH groups) and bifunctional terephthaloyl chloride 2 (TPC) through interfacial polymerization. The structure of the hyper-cross-linked polyamide network has been successfully confirmed by solid (CP-MAS) 13C NMR, XPS, AFM, FT-IR, elemental mapping, and EDX analysis. The membrane features such as surface morphology and hydrophilicity have been established by FE-SEM and water contact angle measurements. The FE-SEM analysis revealed the formation of uniform polyamide active layer on the surface of PS/PET support, and the pore structure of the membranes was tuned by studying the effect of curing temperature and curing time. The nanofiltration membranes efficiently rejected a series of divalent salts including MgCl2, CaCl2, Na2SO4, MgSO4, and NaCl using cross-flow filtration setup. Based on the cross-flow filtration performance, the best conditions for the membrane fabrication were found to be curing temperature of 80 °C with a curing time of 1 h. The highest salt rejection was observed in case of MgCl2 reaching to a value of 98.11% in case of HCPA-TFC-NF@M3 and it was found to be 97.45% in case of HCPA-TFC-NF@M2 while the rejection of MgCl2 was reduced to 94.59% in case HCPA-TFC-NF@M1. HCPA-TFC-NF@M2 showed NaCl rejection of 87.36%. The hydrofluoric acid treatment of HCPA-TFC-NF-M2 increased the water flux while keeping the rejection high. The HCPA-TFC-NF@M2 showed a rejection of >99% for EBT with a permeate flux of 75 LMH.

Solvent-resistant polyimide aerogel film as ultrapermeable support for thin-film composite and covalent organic framework nanofiltration membranes

Organic solvent nanofiltration (OSN) membranes require robust selective layers and support materials. In this study, polyamide and polyester thin-film composites (TFCs) and covalent organic frameworks (COFs) were fabricated as selective layers on a polyimide aerogel support. The ultrapermeable support was stable in various organic solvents including harsh polar aprotic solvents such as N,N-dimethylformamide (DMF), dimethylsulfoxide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone for more than six months. The support enabled fabricating both amorphous and crystalline selective layers at both room and higher temperatures. Moreover, the polyimide aerogel support had 85% porosity, facilitating high solvent flux. The compatibility of the selective layers and support was excellent, and as low molecular weight cutoff values (MWCO) as 356 and as high as 591 g mol−1 were obtained in methanol at 10 bar for the COFs and polyester TFC membranes, respectively. Both experimental MWCO and permeance values of the COF membrane agreed with those predicted using the pore flow model. The effect of the operating temperature on the OSN performance was examined in DMF at 20 and 100 °C. Both membranes demonstrated constant permeance and rejection for more than nine days of continuous filtration.

Development of braid reinforced hollow fiber membranes as both ultrafiltration and nanofiltration membranes: Effect of pore forming additive on structure and performance

AbstractHollow fiber membranes have higher surface area and are easy to be applied in systems. Because of theirs self‐supporting construction, they have limited mechanical durability. By reinforcing these membranes with a braid, the mechanical strength can be improved. In this study, the impact of polyvinyl pyrrolidone (PVP) as a pore‐forming additive with different contents on the fabrication of polysulfone braid reinforced hollow fiber membranes was investigated both as a ultrafiltration membrane and as a support for the fabrication of thin film composite (TFC) nanofiltration membranes. Characterization and filtration studies of all membranes were performed to examine membrane performance. It was discovered that the porosity and hydrophilicity of the ultrafiltration membranes were enhanced by enhancing PVP concentration, thus increasing the pure water flux in the membranes. As regards to results of fabricated TFC membranes, salt rejections were increased with increasing PVP ratios. The rejection efficiency of magnesium sulfate and sodium chloride was found to be approximately 80% and 49%, respectively, when a PVP ratio of 8% was used.

Distinct impact of substrate hydrophilicity on performance and structure of TFC NF and RO polyamide membranes

Substrate properties have profound impacts on the structure and performance of both thin-film composite (TFC) nanofiltration (NF) and reverse osmosis (RO) polyamide (PA) membranes. Some studies have previously investigated the impact of substrate hydrophilicity on PA formation and TFC membrane performance. However, the observed phenomena and explanations remain contradictory in literature. Herein, we performed interfacial polymerization (IP) reactions of both piperazine (PIP)-trimesoyl chloride (TMC) and m-phenylenediamine (MPD)-TMC systems on substrates with different hydrophilicity. We found that the TFC RO membrane showed higher water permeance and NaCl rejection on the relatively hydrophobic substrate, while the TFC NF membrane favored the relatively hydrophilic substrate. The critical importance of interfacial degassing and local monomer concentration was highlighted to dissect the distinct impact of substrate hydrophilicity. For the MPD-TMC system, interfacial nanobubble generation was inhibited because of the decreased local MPD concentration and heat production for the more hydrophilic substrates, resulting in a decrease in the roughness feature and compromised water permeance of RO membranes. In contrast, interfacial degassing was not a dominant mechanism in the PIP-TMC system due to the slower reaction rate of PIP-TMC than MPD-TMC. Consequently, the PA layer of NF membrane became thinner and looser when the substrate became more hydrophilic, resulting from the diluted local PIP concentration. Our study unveils the fundamental relationship among substrate hydrophilicity, PA structure, and separation performance of both TFC NF and RO PA membranes, providing important guides on their design and synthesis.

Surface Modification of a Thin-Film Composite (TFC) Nanofiltration Membrane with 3-Aminopropyltriethoxysilane (APTES) for Efficient Dye–Salt Separation

Nanofiltration (NF) technology is attractive in desalting and concentrating dyeing wastewater in the textile industry. A highly efficient NF membrane is critical in reducing the cost of the process. Here, a facile and reliable approach to prepare an NF membrane for the selective separation of dye/salt is proposed by surface grafting of 3-aminopropyltriethoxysilane (APTES) on a fresh polyamide (PA) layer after interfacial polymerization (IP). A thin layer of APTES with a thickness of ∼64 nm was found successfully covalently bonded onto the PA surface via esterification and amidation reactions. The thin-film composite (TFC)-1.0 membrane grafted with 10% APTES achieved a high water permeance of 44.8 L m–2 h–1 bar–1, which was 4.7 times higher than that of the control TFC membrane. Interestingly, the rejection of monovalent salt (NaCl, 11.5%) and divalent salt (Na2SO4, 17.2%) decreased significantly, while the rejection for different dyes (Congo red, reactive blue-19, Coomassie blue G-250, and methyl blue) remained over 99.0%. These noticeable changes in separation performances could be attributed to the large pore size of the active layer, resulting from the interference of APTES on the post-cross-linking of a PA network. The poly(ethylene glycol) (PEG) filtration experiments confirmed that the mean pore size of the membrane was enlarged significantly from 0.51 to 1.17 nm after surface modification. Finally, the modified membrane showed good long-term stability and excellent separation efficiencies in fractionation of a high salinity Congo red/NaCl (0.2/50 g L–1) mixture. Overall, this work provides a practical strategy to prepare a permeable and selective NF membrane for dye and salt separation by surface grafting of the nascent PA layer.

Naturally Derived Allylated Gallic Acid for Interfacially Polymerized Membranes

A naturally derived monomer, allylated gallic acid (AG), was herein proposed as a monomer for interfacially polymerized thin-film composite nanofiltration membranes. We investigated the synthesis of the thin-film composite polyester membranes by varying the concentration of the AG monomer and the reaction time with trimesoyl chloride. In addition, we demonstrated the synthesis of a polyesteramide film using a mixture of AG and m-phenylene diamine, although there are a few orders of magnitude differences in their reactivity. While membranes prepared using the classical polyamide process had a water permeance of 0.54 L m–2 h–1 bar–1 , the prepared polyesteramide and polyester films had water permeances of 12.3 and 47.6 L m–2 h–1 bar–1, respectively The rejection of dyes was larger than 700 g mol–1 and could be tuned to 327 g mol–1 by changing the chemical composition and reaction time. The retention of inorganic salts followed the order Na2SO4 > MgSO4 ≈ NaCl. Therefore, the membrane performance demonstrates the potential of the phenolic monomer to be integrated into the synthesis of thin-film composite membranes. Besides, the availability of the free allyl group holds potential for further modification and covalent binding onto the surface.

Thin-Film Composite Membranes with a Carbon Nanotube Interlayer for Organic Solvent Nanofiltration.

Compared to the traditional chemical-crosslinking-based polymer, the porous polytetrafluoroethylene (PTFE) substrate is considered to be an excellent support for the fabrication of thin-film composite (TFC) organic solvent nanofiltration (OSN) membranes. However, the low surface energy and chemical inertness of PTFE membranes presented major challenges for fabricating a polyamide active layer on its surface via interfacial polymerization (IP). In this study, a triple-layered TFC OSN membrane was fabricated via IP, which consisted of a PA top layer on a carbon nanotube (CNT) interlayer covering the macroporous PTFE substrate. The defect-free formation and cross-linking degree of the PA layer can be improved by controlling the CNT deposition amount to achieve a good OSN performance. This new TFC OSN membrane exhibited a high dye rejection (the rejection of Bright blue B > 97%) and a moderate and stable methanol permeated flux of approximately 8.0 L m−2 h−1 bar−1. Moreover, this TFC OSN membrane also exhibited an excellent solvent resistance to various organic solvents and long-term stability during a continuous OSN process.

Influence of molecular weight cut-off (MWCO) of commercial ultrafiltration substrate on the performance of thin film composite nanofiltration membrane

This study investigated the impacts of polyether sulfone (PES) substrate with four different molecular weight cut-offs (MWCO) on the performance of the thin-film composite (TFC) nanofiltration membranes. When the MWCO of the substrate increased: (i) the effective thickness of the substrate decreased; (ii) the average pore size of the substrate enlarged in general; and (iii) the surface roughness of the substrate increased. When the MWCO of substrates was increased, the TFC membranes synthesized from them showed the following characteristics: (i) the thickness of the polyamide layer expanded; (ii) average size of the nodules on the membrane surface enlarged, (iii) permeate flux enhanced in general, (iv) rejection of NaCl (RNaCl) increased and rejection of MgSO4 (RMgSO4) did not change significantly; (v) flux recovery rates decreased. The study showed that the MWCO of the substrate had a similar influence on the permeate fluxes produced by the substrate and the TFC membrane. Lower MWCO substrates induced higher selectivity to divalent and monovalent ions.

Hyaluronic acid-modified nanofiltration membrane for ultrahigh water permeance and efficient rejection of PFASs

Emerging contaminants (ECs) in water, such as per- and polyfluoroalkyl substances (PFASs), require more efficient separation technology for water treatment. Although nanofiltration (NF) has exhibited the potential to remove small organic molecules, enhancing water permeance without sacrificing the rejection of the membrane is still a big challenge. Herein, we fabricate a novel thin-film composite (TFC) membrane by introducing a hyaluronic acid (HA) interlayer. The hydrogen bonds between HA and amine monomers depress the mass transfer of piperazine, which is beneficial for constructing a thinner and denser polyamide (PA) layer. As a result, we finally obtained a novel TFC membrane with a PA layer with a more negative surface, reduced thickness, crumpled structure and higher degree of cross-linking. Moreover, the obtained TFC membrane exhibits an excellent water permeance of 29.53 L m−2 h−1 bar−1 and high rejection for Na2SO4 (94.90 %) and perfluorohexane sulfonic acid (PFHxS) (93.4 %). In light of the low cost and ease of performance, our study proposes a new, green strategy for fabricating TFC NF membranes for environmental water treatment that could feasibly be extended to industrial applications.

In-situ sol-gel generation of SiO2 nanoparticles inside polyamide membrane for enhanced nanofiltration

Interfacial polymerization (IP) has been deemed as the principal strategy to fabricate thin film composite (TFC) nanofiltration (NF) membranes. However, the separation performances of TFC membrane are prone to be impaired with the issue of trade-off relationship between selectivity and permeability. Herein, a combined IP and in-situ sol-gel method was proposed to synthesis novel thin film nanocomposite (TFN) NF membrane. The nano-enhanced polyamide (PA) functional layer was created by the IP reaction, while the in-situ generated silicon dioxide (SiO2) nanoparticles were formed through the hydrolysis and condensation process. The optimal separation performance was obtained by tailoring the formation process of SiO2 nanoparticles via varying the NaOH concentration. The results revealed that the in-situ generated SiO2 nanoparticles were uniformly distributed within the PA layer, which greatly enhanced the hydrophilicity due to the abundant Si-OH groups. The membrane decorated by 1 ml TEOS under 0.3 wt% NaOH condition possessed a pure water permeability up to 70.69 L m−2 h−1 bar−1 and high rejection rates against dyes (99.99 % for Congo red, 99.55 % for Coomassie blue G-250, 99.39 % for Reactive blue 19), while maintaining low salt rejections (4.92 % for NaCl, 7.14 % for Na2SO4). Meanwhile, the membrane presented an excellent long-term operational stability.

Development of Composite Thin-Film Nanofiltration Membranes Based on Polyethersulfone for Water Purification

The development of thin-film composite membranes has gained more importance as they exhibit higher permeability, higher solute rejection and improved antifouling behavior. The incorporation of hydrophilic nanomaterials within the composite thin film has reported to effectively increase the hydrophilicity and improve the membrane performance. In this study novel thin-film composite nanofiltration membranes were prepared by interfacial polymerization of trimesoyl chloride, polyvinylpyrolidone (PVP) and montmorillonite (MMT) composite on the porous polyethersulfone membrane. The effect of preparation parameters was studied as; reaction time, PVP concentration and MMT content. The properties of the prepared composite thin-film membranes were analyzed in terms of their chemical structure, surface morphological features, pure water contact angle, zeta potential, pure water permeation flux (PWP) and solutes rejection. The prepared composite thin-film membranes showed smoother surfaces, different surfaces functionality and amphoteric surfaces with points of zero charge at pH 7–7.5. The PWP was found to increase with increasing MMT content up to 0.10 wt%. The rejection of crystal violet dye (CV) was studied using the prepared membranes. The membrane with 0.5% PVP, 0.10% MMT and 6 min reaction time showed PWP of 18.1 L/m2 h bar and CV rejection of 80.01%. The rejection of Na2SO4 and MgCl2 increased with increasing MMT content and reached 96% and 35.4%, respectively. The steady state flux was decreased by 5% with increasing MMT content from 0.10 to 0.12 wt% indicating improved antifouling behavior with MMT.

A CNT/PVA film supported TFC membranes for improvement of mechanical properties and chemical cleaning stability: A new insight to an alternative to the polymeric support

Thin film composite (TFC) nanofiltration (NF) membranes supported by polymeric membranes have suffered from limited mechanical properties and chemical cleaning stability, resulting in an increasing operation cost. Strengthening the support of TFC membranes is expected to provide great stability for membranes. This work provided a TFC membrane constructed on the poly (vinyl alcohol) (PVA) incorporated carbon nanotube film, which was named CNT/PVA-TFC. Characteristics of substrates, including morphology, pore size, and mechanical properties, were investigated by scanning electron microscopy (SEM), intrusion mercury porosimetry and tensile method. The results demonstrated that PVA can improve the mechanical properties and hydrophilicity of the CNT film. The morphology, physicochemical properties and separation performance of CNT/PVA-TFC were also investigated. CNT/PVA-TFC showed great enhancement of mechanical properties with its elastic modulus and hardness approximately 330% and 200% of the control, respectively. Furthermore, CNT/PVA-TFC achieved greater resistance to caustic cleaning than TFC membranes supported by polymeric membranes. In addition, CNT/PVA-TFC exhibited an excellent flux decline of 29.3% and a flux recovery of 97.0%. The mechanism of the support of CNT and enhancement of PVA was systematically studied. This work highlighted the feasibility of fabricating TFC membranes on the CNT/PVA film, providing a new insight to alternate the polymeric substrate of TFC membranes.

Enhancing the flux and salt rejection of thin-film composite nanofiltration membranes prepared on plasma-treated polyethylene using PVA/TS-1 composite

The high hydrophobicity of polyethylene (PE) film restricts its application as a thin-film composite (TFC) support layer. Therefore, in this study, oxygen plasma treatment was used to generate hydrophilic groups on PE and facilitate the formation of the TFC membrane. The difference in the performance of the plasma treated-PE (P-PE) membrane compared to untreated-PE indicated the significant effect of plasma pretreatment. In the following, to enhance the hydrophilicity of the P-PE membrane, titanium silicate-1 (TS-1) was synthesized as a zeotype through the hydrothermal method and added to the aqueous solution of the interfacial polymerization process. Due to the decrease in the agglomeration of TS-1 in the membrane matrix, PVA/TS-1 composites with distinct concentrations of polymer were prepared and applied for modifying membrane properties. Membranes were characterized by FESEM, ATR-FTIR, AFM, zeta potential, and water contact angle analyses. Permeability, rejection of monovalent and divalent salts, and antifouling ability of the fabricated nanofiltration membranes were studied and the optimal polymer concentration was determined. Comparison of P-PE-TFC 0.1 membrane with P-PE showed an increase of ~42% in pure water flux. Also, the rejection of Na2SO4, MgSO4, MgCl2, and NaCl salts were 90.28%, 81.77%, 74.79%, and 70.94% for P-PE-TFC 0.1 membrane, respectively, which showed a notable improvement compared to the P-PE membrane. Evaluation of antifouling ability showed that P-PE-TFC 0.1 membrane had a higher resistance to fouling compared to other membranes. Flux recovery ratio of this membrane after three cycles of bovine serum albumin (BSA) filtration was higher than other membranes resulting from the reduced roughness due to the combined effect of PVA and TS-1.

Highly permeable composite nanofiltration membrane via γ-cyclodextrin modulation for multiple applications

The treatment of pharmaceutical wastewater has become a worldwide problem. Highly efficient treatment for wastewater is extremely critical for ecological environment. Herein, a thin-film nanofibrous composite (TFNC) nanofiltration (NF) membrane modulated by γ-cyclodextrin (γ-CD) was prepared via interfacial polymerization. The γ-CD and piperazine (PIP) were adopted and acting as the mixed reaction monomers in aqueous phase for the fabrication of the separation layer. Not only PIP, γ-CD units would also react with organic phase trimesoyl chloride (TMC) at the interface and participate into the polymerization network. Compared with pure polyamide TFNC membranes, the γ-CD modulated TFNC membranes demonstrated thinner skin thickness. Owing to the 3D hollow structure of γ-CD, the self-contained through cavities would provide additional direct nanochannels to facilitate the water transport. Under 0.5 MPa, the optimized PIP0.5γCD0.5 and PIP0.5γCD1.5 TFNC membranes showed much higher permeate flux of 23.27 and 26.34 L m-2h−1 bar−1, respectively, than that of pure polyamide membranes (9.13 and 9.85 L m-2h−1 bar−1) and the Na2SO4 rejection remained high (>98.7%). Moreover, both TFNC membranes exhibited extremely high rejection (>99%) for several pharmaceuticals (doxycycline hydrochloride, tetracycline, and amoxicillin), and the PIP0.5γCD0.5 TFNC membrane exhibited a good separation factor (31.8) for NaCl/tetracycline solution. In addition, both optimized TFNC membranes showed good pressure resistance and long-term operating stability. This research revealed a facile modulation strategy for the fabrication of high-performance NF membrane and indicated the great promise for desalination, pharmaceuticals wastewater treatment and antibiotics concentration.

Assessing the impact of membrane support and different amine monomer structures on the efficacy of thin-film composite nanofiltration membrane for dye/salt separation

Assessing the impact of membrane support and different amine monomer structures on the efficacy of thin-film composite nanofiltration membrane for dye/salt separation