Polyamide Thin Film Composite Nanofiltration Research Articles

Photosensitive and high temperature resistant polyamide composite nanofiltration membranes with high flux and stable retention

Currently, most commercial membranes are used at temperatures below 50 °C. For high temperature water treatment, nanofiltration membranes with good thermal stability are highly sought after. In order to construct a novel polyamide thin-film composite nanofiltration (TFC NF) membrane, Congo red (CR) as monomer was introduced to the aqueous phase and the chemical structure of the selective layer was changed. Next, a thorough investigation was conducted into the impacts of the piperazine (PIP) to CR ratio on the surface morphology, separation efficiency and chemical structure of the membranes. The TFC NF membrane prepared after parameter optimization exhibited high retention (Na2SO4, >98 %) and flux up to 30 L·m−2·h−1·bar−1 at room temperature. Moreover, the Na2SO4 retention of the TFC NF membrane decreased by less than 1 % when used at 90 °C, demonstrating excellent heat resistance. Meanwhile, the incorporation of CR allowed the structure of the TFC NF membranes to be altered under UV irradiation conditions, which provided new insights into the optical modulation of the composite membrane properties. A promising and reproducible methodology for the development of high flux TFC NF membrane with thermal stability was offered, achieving a breakthrough in water treatment technology under high-temperature conditions.

Thin film composite polyamide nanofiltration membranes with interlayer constructed with core-shell structured polystyrene-polyacrylamide nanospheres for antibiotics separation

Nanofiltration (NF) is an efficient and economic separation technology which has great application potential in solving worldwide water shortage. Constructing interlayer is an effective approach to fabricate thin film composite (TFC) polyamide (PA) NF membranes with better performance. Herein, the polystyrene-polyacrylamide nanospheres with core-shell structure were synthesized using an emulsion polymerization method. The PA NF membranes were prepared via interfacial polymerization (IP) on the mixed cellulose esters microfiltration (MCE MF) membranes which modified with the core-shell structured nanospheres. The fabricated PA NF membranes showed good performance with a pure water permeability of 18.9 L·m−2·h−1·bar−1 and Na2SO4 rejection of 97.4 %. The NF membranes also showed good antibiotics separation performance with rejection to levofloxacin (LEV), penicillin G (PG), tetracycline (TC), and erythromycin (ERY) of 97.1 %, 86.9 %, 92.2 %, and 96.4 %, respectively and efficient separation to antibiotics and NaCl. This work provides a feasible strategy to construct an interlayer of PA NF membranes with the core-shell structured polystyrene-polyacrylamide nanospheres.

Preparation of high temperature resistant polyamide composite nanofiltration membranes by thermally assisted interfacial polymerization

The temperature of interfacial polymerization (IP) and feed temperature both have importance effects on the structure and properties of polyamide thin film composite nanofiltration (TFC NF) membranes. This experiment involved preparing TFC NF membranes using IP at 25, 60, 80, and 100 °C, and their performance was evaluated in the range of 25 to 90 °C. Results showed that the membrane prepared at an IP temperature of 100 °C maintained more than 99% retention of divalent salts. The high temperature allowed the reaction between piperazine (PIP) and 1,3,5-benzoyl chloride (TMC) to become more complete and the degree of crosslinking increased, resulting in a thicker and denser defect-free polyamide layer. With increasing the temperature of the feed solution, the increase of pores sizes caused by swelling made the permeance increase by 2 ∼ 3 times, but the rejection rate of salt (Na2SO4, MgSO4) by TFC NF membranes prepared at 80 and 100 °C remained unchanged (>99%). In addition, the TFC NF membrane obtained by high-temperature IP has excellent anti-fouling and long-term stability. By adopting high-temperature IP, the TFC NF membranes exhibited excellent anti-fouling and long-term stability, making them an economical and versatile method for treating water in high-temperature environments.

Antimicrobial thin-film composite polyamide nanofiltration membrane with high desalination and flux performance manufactured through a novel UV light driven photoreduction method that generates dispersed silver nanoparticles

Antimicrobial thin-film composite polyamide nanofiltration membrane with high desalination and flux performance manufactured through a novel UV light driven photoreduction method that generates dispersed silver nanoparticles

Recent Advanced Development of Acid-Resistant Thin-Film Composite Nanofiltration Membrane Preparation and Separation Performance in Acidic Environments

Membrane filtration technology has attracted extensive attention in academia and industry due to its advantages of eco-friendliness related to environmental protection and high efficiency. Polyamide thin-film composite nanofiltration (PA TFC NF) membranes have been widely used due to their high separation performance. Non-acid-resistant PA TFC NF membranes face tremendous challenges in an acidic environment. Novel and relatively acid-resistant polysulfonamide-based and triazine-based TFC NF membranes have been developed, but these have a serious trade-off in terms of permeability and selectivity. Hence, how to improve acid resistance of TFC NF membranes and their separation performance in acidic environments is a pivotal issue for the design and preparation of these membranes. This review first highlights current strategies for improving the acid resistance of PA TFC NF membranes by regulating the composition and structure of the separation layer of the membrane performed by manipulating and optimizing the construction method and then summarizes the separation performances of these acid-resistant TFC NF membranes in acidic environments, as studied in recent years.

Trimethylamine N-oxide-derived zwitterionic polyamide thin-film composite nanofiltration membranes with enhanced anti-dye deposition ability for efficient dye separation and recovery

Organic dyes from textile industries are becoming the second largest pollutants in the world. In this study, inspired by the seawater fish, a new diamine monomer, N,N-bis(3-aminopropyl)methylamine N-oxide (DNMAO) with a trimethylamine N-oxide (TMAO)-derived “N+─O−” zwitterionic functionality, has been designed for the fabrication of polyamide thin-film composite (TFC) membranes to purify dye-contaminated water and recover organic dyes. The fabricated membranes show enhanced permeability and improved anti-dye-deposition performance. The optimum membrane fabricated at 0.5 wt% of DNMAO feed solution exhibits an ultrahigh pure water permeability (PWP) of 37.5 LMH bar−1, a superior Congo red (CR) rejection of 99.93%, and a low sodium chloride (NaCl) rejection of 9.3%, indicating its outstanding performance for dye/salt separation. It can also achieve the complete CR removal from a feed with a low CR concentration of 1 ppm, demonstrating its superior separation performance for the production of clean potable water. In addition, the low dye loss rate (6.22%) and high salt removal rate (85.6%) are achieved during the purification and recovery test with CR/NaCl mixtures. Furthermore, the optimum membrane possesses an excellent anti-dye-deposition performance with a flux recovery ratio (FRR) of 92.1%. All these results demonstrate its potential for applications in not only textile wastewater treatment but also organic dye purification and recovery.

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.

Trimethylamine N-Oxide-Derived Zwitterionic Polyamide Thin-Film Composite Nanofiltration Membranes with Enhanced Anti-Dye Deposition Ability for Efficient Dye Separation and Recovery

Trimethylamine N-Oxide-Derived Zwitterionic Polyamide Thin-Film Composite Nanofiltration Membranes with Enhanced Anti-Dye Deposition Ability for Efficient Dye Separation and Recovery

Intensification of mass transfer for zwitterionic amine monomers in interfacial polymerization to fabricate monovalent salt/antibiotics separation membrane

Zwitterionic groups are conducive to improve the antifouling performance and water permeability of nanofiltration membranes because of the excellent hydrophilicity and charged property. However, the transport of zwitterionic monomers during interfacial polymerization process is much slower than the reaction, leading to form many defects in the separation layer. In this study, phase transfer catalysts were used to intensify the interfacial mass transfer of zwitterionic amine monomers for fabricating polyamide thin-film composite nanofiltration membranes. The transport process was explored by measuring the diffusion kinetics of monomers to regulate the structures and properties of zwitterionic membranes. Consequently, low concentration of N-aminoethyl piperazine propane sulfonate (AEPPS) as aqueous monomer could be used to prepare membranes with excellent nanofiltration performance. When the concentration of AEPPS was as low as 1 w/v%, the as-prepared zwitterionic membrane possessed a pure water flux of 10.6 L m−2 h−1 bar−1 with a high erythromycin retention of 91.7% and a low NaCl retention of 7.3%, which exhibited great application potential in the separation of monovalent salt/antibiotics. Moreover, the flux recovery ratio of the zwitterionic membrane was still maintained at ∼96.5% after undergoing twice fouling-rinse experiments of bovine serum albumin, exhibiting exceptional antifouling performance.

Design and fabrication of fouling resistant cross-linked polyamide thin film composite nanofiltration membrane consisting of an aliphatic triamine and terephthaloyl chloride for water desalting applications

Although a lot of polyamide thin film composite nanofiltration (TFC-NF) membranes have been developed but organic and biofouling are affecting the performance and lifespan of such membranes. Hence, the development of new and efficient polyamide membrane with a great potential against fouling is desperately needed. A new polyamide TFC-NF membrane was fabricated by reacting a linear aliphatic diethylene triamine (DETA) and linear cross-linker terephthaloyl chloride (TPC) through interfacial polymerization on ultrafiltration porous support. The resulting membrane namely Polyamide@PSf/PET was further treated with 15% hydrofluoric acid (HF) for 1 week. Membranes were extensively characterized by XPS, AFM, Zeta-potential, FESEM, FTIR, EDX, Elemental mapping and Contact angle. The HF treated Polyamide@PSf/PET showed superior performance in terms of pure water flux and rejection of tested salts and flux recovery. The highest observed water flux was 48 LMH at 24 bars while the rejection of MgSO4 reached to > 95%. HF treated Polyamide@PSf/PET membrane showed greater flux recovery of 86.4% compared to Polyamide@PSf/PET which showed a flux recovery of 84.5%. The HF treated membrane showed lower tendency towards biofouling. The bacteriostatic studies revealed that the HF treated Polyamide@PSf/PET membrane inhibited S. aureus growth by 70.7%.

Facile fabrication of graphitic carbon nitride nanosheets and its integrated polyamide hyper-cross-linked TFC nanofiltration membrane with intrinsic molecular porosity for salts and organic pollutant rejection from water

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. FE-SEM of the g-C3N4/PA@PSf/PET membrane showed uniform and equal distribution of 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 % rejection of 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.

Facile preparation of polyvinylidene fluoride substrate supported thin film composite polyamide nanofiltration: Effect of substrate pore size

Polyvinylidene fluoride (PVDF) is rarely used as substrate membrane for thin film composite polyamide (PA) nanofiltration (NF) membrane due to its hydrophobic surface pushes water away during interfacial polymerization. According to Jurin's law, the pressure of membrane surface pushed water away is inversely proportional to the radius of membrane pore. In this study, a series of commercial PVDF membranes with pores ranging from 25 to 450 nm were used as substrates in a traditional interfacial polymerization. This preparation process does not need any pre-modification on substrate or specific equipment. It was found that the PVDF substrate pore size greatly influences the morphologies and surface properties of the corresponding TFC PA NF membrane. Only when a PVDF substrate has moderate pore size, such as 50 and 100 nm, could a continuous and defect-free PA layer will be formed, as verified through SEM characterization. The TFC membrane prepared with the PVDF substrate of 100 nm exhibits a 27.0 L m-2 h-1 bar-1 pure water permeance, and a 96.2% Na2SO4 rejection. The facile and effective method demonstrated in this study provides a new thought for the preparation of PVDF substrate supported PA NF membrane.

Enhanced removal efficiency of heavy metal ions by assembling phytic acid on polyamide nanofiltration membrane

The water pollution caused by heavy metals is bringing serious damage to public health and environment, and significant efforts have been devoted to explore advanced materials and technologies for eliminating toxic metal ions more efficiently. Herein, a phytic acid (PA)-incorporated polyamide thin-film composite nanofiltration (NF) membrane is constructed though traditional interfacial polymerization and electrostatic assembly of PA with polyethyleneimine. Owing to the high negative charges of PA, the resultant NF membrane exhibits ultrahigh binding affinity for heavy metals cations, and is highly capable of removing heavy metal ions from aqueous solution. As a result, the PA-functionalized NF membrane can reduce Cd2+ and Pb2+ concentrations from 500 ppm to the ultralow level of ~0 and 5 ppb, and achieve record-breaking remove rates of 100.000% for Cd2+ and 99.999% for Pb2+. Additionally, the as-prepared NF membrane also delivers excellent long-term stability in continuous 120-h operation, and can be easily regenerated and reused without remarkable fading of the initial Cd2+ removal rate even after six filtration cycles. This work demonstrates the potential usage of the PA-functionalized NF membrane for serving as a promising platform to eliminate heavy metal ions in waste water.

Processing of Black Carrot Juice by Nanofiltration and Forward Osmosis

Juice concentration is traditionally achieved with thermal evaporators. However, many nutrients and sensorial attributes suffer from degradation at high temperature. In order to preserve the sensorial and nutritional attributes of the juice, non-thermal processes based on membranes have arisen as an alternative.In the present work, 6.7 °Brix black carrot juice has been subjected to a sequence of processes based on nanofiltration (NF) and forward osmosis (FO) operated at room temperature with the aim of concentrating acylated anthocyanins. Four polymeric membranes with molecular weight cut-offs in the range 150 – 2000 Da were compared in terms of flux and anthocyanin rejection. The membrane showing the best performance was a polyamide thin film composite NF membrane with a reported cut-off of 600 – 800 Da. With this membrane, the rejection of anthocyanins was 98% and the rejection of total soluble solids was 65 %. The juice was pre-concentrated to 10 °Brix with minimal anthocyanin loss. The resulting retentate was further concentrated to 43 °Brix using FO biomimetic membranes and a solution of MgCl2 as draw.

Preparation and Characterization of Polyamide Thin Film Composite Nanofiltration Membrane Based on Polyurethane Nanofibrous Support

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.

Grafting of zwitterion polymer on polyamide nanofiltration membranes via surface-initiated RAFT polymerization with improved antifouling properties as a new strategy

Special radical grafting strategies, e.g. surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization, are considered as promising techniques for the purpose of not only uniformly modifying nanofiltration (NF) membranes with the functional polymers but also preventing nonspecific protein adsorption. In this research work, we decide to report for the first time an efficient approach to stabilize RAFT initiators on the surface of polyamide NF membranes and study the effect of the chain length of the polymer on the membrane fouling performance. For this purpose, using interfacial polymerization between trimesoyl chloride (TMC) and a mixture of diamines (i.e. 1,3-phenylenediamine (MPD) and (3,5-diamino phenyl) methanol (DAPM), polyamide thin film composite NF membranes were synthesized. Afterward, the reaction between the polyamide thin film composite layer and α-bromoisobutyryl bromide (BIBB) was carried out. It was found that the stabilized amount of BIBB on the surface of the prepared membranes could be efficiently enhanced by using the DAPM treatment. Finally, using RAFT polymerization technique, a zwitterionic polymer, poly[(2-methacryloyloxy)ethyl]dimethyl[3-sulfopropyl]ammonium hydroxide (pMEDSAH), was successfully grafted on the membrane surface. It is noteworthy that the irreversible adsorption amount of proteins on the prepared pMEDSAH-grafted membrane appreciably decreased to >96%. All the provided results indicate that all the pMEDSAH-grafted membranes, which were prepared using a facile and efficient method, have proved promising for practical applications.

High water permeating thin film composite polyamide nanofiltration membranes showing thermal responsive gating properties

High water permeating thin film composite (TFC) polyamide (PA) nanofiltration (NF) membranes were prepared by grafting 2-(Dimethylamino)ethyl methacrylate (DMAEMA) monomers onto their surfaces through a free radical polymerization process. Grafted PDMAEMA layer increased the water permeation of TFC-PA NF membranes up to 2.6 times without trading off their salt rejection capability. The anti-fouling performance of the NF membranes was improved by further surface zwitterionization processes involving 1,3-propane sulfone(1,3-PS). Thermal-responsive gating property for water and salt permeation was observed in these high flux NF membranes and found to be useful in trapping and releasing protein molecules via temperature variations. These high flux NF membranes with thermal-responsive gating property may find applications in material enrichment, drug delivery and water treatments.

Fabrication of thin-film composite polyamide nanofiltration membrane based on polyphenol intermediate layer with enhanced desalination performance

Nanofiltration (NF) membrane is of great significance for desalination of light brine and purification of drinking water. Although the development of novel preparation methods and membrane materials has improved the separation performance, it is still a major challenge to promote NF membrane toward industrial production with simpler and more controllable process. Herein, the polyphenol intermediate layer was designed by 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) with twist structure and polyethyleneimine (PEI) co-deposition to increase the surface hydrophilicity and electropositivity of the polysulfone ultrafiltration substrate. Subsequently interfacial polymerization (IP) was carried out on the polyphenol intermediate layer to assemble a polyamide ultrathin selective layer using trimesoyl chloride and piperazine monomer. Through adjusting the co-deposition time of TTSB and PEI, a unique nano-pleated structure was successfully formed on the thin-film composite membrane surface. The water permeance of the membrane was determined as 23.7 L m−2 h−1 bar−1 with 99.4% Na2SO4 rejection, which was almost triple fold of the flux of the controller membrane without the intermediate layer. Our results provide an efficient and convenient way to fabricate the advanced NF membrane with higher divalent/monovalent ion selectivity and water permeance simultaneously, which will provide advices for the gas separation and pervaporation membranes with the IP method.

Modulating hydrophobicity of composite polyamide membranes to enhance the organic solvent nanofiltration

A kind of thin film composite polyamide nanofiltration (NF) membrane was synthesized via the interfacial polymerization between a new diamine monomer of 4,4′-diaminodiphenylmethane and trimesoyl chloride on the surface of cross-linked polyetherimide, and evaluated in some organic solvents including ACN, MeOH, EtOH, THF, etc. The optimal organic solvent NF membrane was selected to prepare respectively the hydrophilic membrane (Phi-NF) via grafting of Tris and the hydrophobic membrane (Pho-NF) via grafting of 2,2,2-trifluoroethylamine, combining with the characterization of ATR-FTIR, XPS, SEM, 13C NMR, AFM, etc. The permeance values of Phi-NF and Pho-NF membranes change greatly with organic solvents. Pho-NF-2 possesses the highest permeance of 66.4 L m−2 h−1 MPa−1 in THF with the erythrosin B (EB) rejection of 99.5%. Through analyzing the physiochemical properties of the organic solvents and calculating the surface energy, the correlations are deduced for the synthesized membranes, illustrating that the permeances of organic solvents are roughly proportional to the specific solvent properties for Phi-NF-2 and Pho-NF-2. The results suggest one promising method to enhance the separation performance of organic solvent NF membranes.

Water Softening Using a Light-Responsive, Spiropyran-Modified Nanofiltration Membrane.

A novel technique for the covalent attachment of a light-responsive spiropyran onto polyamide thin film composite nanofiltration (NF) membranes in a one-step reaction using low-energy electron beam technology is described. The effect of illumination of the immobilized spiropyran was studied, as well as the resulting membrane properties with respect to MgSO4 retention, water permeability rate, and chlorine resistance. Electron beam irradiation showed a direct effect on the transformation of the rough PA NF membrane surface into a ridge-and-valley structure. Upon UV light irradiation, the spiropyran transformed into zwitterionic merocyanine, which had shown MgSO4 removal of >95% with water permeation rates of 6.5 L/(m2·h·bar). Alternatively, visible light was used to convert merocyanine to spiropyran, which achieved >95% of MgSO4 retention with a water flux of around 5.25 L/(m2·h·bar). The modified NF membranes showed higher chlorine resistance as well as a higher normalized water flux as compared to the reference membrane, without a loss of ion retention. All the NF membranes were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. This study demonstrates a simple and inexpensive method for the immobilization of molecules onto polymeric membranes, which may be applied in water softening.