Simple method for preparing thin film composite polyamide nanofiltration membrane based on hydrophobic polyvinylidene fluoride support membrane

Influence of polar solvent in formation and organic solvent separation performance of novel fluorine-containing polyamide membranes

Poly(N-isopropylacrylamide) (PNIPAAm) was introduced into a polyethylene terephthalate (PET) nonwoven fabric to develop novel support for polyamide (PA) thin-film composite (TFC) membranes without using a microporous support layer. First, temperature-responsive PNIPAAm hydrogel was prepared by reactive pore-filling to adjust the pore size of non-woven fabric, creating hydrophilic support. The developed PET-based support was then used to fabricate PA TFC membranes via interfacial polymerization. SEM–EDX and AFM results confirmed the successful fabrication of hydrogel-integrated non-woven fabric and PA TFC membranes. The newly developed PA TFC membrane demonstrated an average water permeability of 1 L/m2 h bar, and an NaCl rejection of 47.0% at a low operating pressure of 1 bar. The thermo-responsive property of the prepared membrane was studied by measuring the water contact angle (WCA) below and above the lower critical solution temperature (LCST) of the PNIPAAm hydrogel. Results proved the thermo-responsive behavior of the prepared hydrogel-filled PET-supported PA TFC membrane and the ability to tune the membrane flux by changing the operating temperature was confirmed. Overall, this study provides a novel method to fabricate TFC membranes and helps to better understand the influence of the support layer on the separation performance of TFC membranes.

Application of cosolvent-assisted interfacial polymerization technique to fabricate thin-film composite polyamide pervaporation membranes with PVDF hollow fiber as support

The silver-zinc oxide (Ag-ZnO) polyamide thin film composite (PA-TFC) membrane was prepared by interfacial polymerization. The Ag-ZnO/PA-TFC membrane was characterized by attenuated total reflectance fourier-transform infrared spectroscopy (ATR-FTIR) for polyamide functional groups and contact angle for surface hydrophilicity. The Ag-ZnO/PA-TFC membrane was further characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for morphology and surface roughness, respectively. The performance of the fabricated membrane was investigated using pure water flux, permeability, rejection, flux recovery, and fouling resistance using low molecular weight organic pollutants, 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP). The results were compared to the neat (PA-TFC) membrane. It was observed that incorporation of Ag-ZnO nanocomposites into the PA-TFC membrane improved hydrophilicity, permeation, rejection, and fouling resistance properties of the membrane. The contact angle decreased from 62.8° to 54° for PA-TFC and the Ag-ZnO/PA-TFC membrane, respectively. The presence of Ag-ZnO enhanced permeability of the membrane from 0.9 (Lm−2h−1bar−1) to 1.9 (Lm−2h−1bar−1). Modification of the membrane with Ag-ZnO further showed an enhanced rejection of 2-CP and 2,4-DCP from 43% to 80% and 58% to 85%, respectively. The 2,4-DCP molecules were rejected more than 2-CP due to enhanced repulsive forces from the extra Cl ion. A high flux recovery of about 95% was achieved for the modified membrane compared to 64% for the neat membrane. The improved flux recovery was an indication of enhanced antifouling propensity.

Improved performance of polyamide thin-film composite nanofiltration membrane by using polyetersulfone/polyaniline membrane as the substrate

A polydopamine-coated polyamide thin film composite membrane with enhanced selectivity and stability for vanadium redox flow battery

As water molecules permeate ultrafast through carbon nanotubes (CNTs), many studies have prepared CNTs-based membranes for water purification as well as desalination, particularly focusing on high flux membranes. Among them, vertically aligned CNTs membranes with ultrahigh water flux have been successfully demonstrated for fundamental studies, but they lack scalability for bulk production and sufficiently high salt rejection. CNTs embedded in polymeric desalination membranes, i.e., polyamide thin-film composite (TFC) membranes, can improve water flux without any loss of salt rejection. This improved flux is achieved by enhancing the dispersion properties of CNTs in diamine aqueous solution and also by using cap-opened CNTs. Hydrophilic CNTs were prepared by wrapping CNT walls via bio-inspired surface modification using dopamine solution. Cap-opening of pristine CNTs is performed by using a thermo-oxidative process. As a result, hydrophilic, cap-opened CNTs-embedded polyamide TFC membranes are successfully prepared, which show much higher water flux than pristine polyamide TFC membrane. On the other hand, less-disperse, less cap-opened CNTs-embedded TFC membranes do not show any flux improvement and rather lead to lower salt rejection properties.

Optimizing separation layer structure of polyamide composite membrane for high permselectivity based on post-treatment: A review

Interfacially polymerized thin-film composite polyamide membranes: Effects of annealing processes on pervaporative dehydration of aqueous alcohol solutions

The long-term sustainability of beneficial effects resulting from the modification of polyamide thin-film composite (PATFC) membranes with zwitterionic poly(sulfobetaine methacrylate) (pSBMA) and silver nanoparticles (AgNPs) in real-world application scenarios remains uncertain. This study used response surface methodology and innovative anti-biofouling evaluation method to optimize the conditions for AgNP- and pSBMA-co-modified PATFC membranes, with reverse osmosis seawater desalination as the test application scenario. A 180-day continuous seawater treatment test was conducted to evaluate the long-term sustainability of anti-biofouling resistance. Results indicated that loading AgNPs before grafting pSBMA enhanced their stability during use and cleaning. Co-modification under optimal conditions led to a 6.3% improvement in membrane flux reduction over long-term operation. The effect of AgNPs was significant for 30 days, while pSBMA remained effective until the end of the test. Water contact angle measurements, confocal laser scanning microscopy, and quorum sensing signal molecule analysis revealed anti-bioflouling improvements due to the hydration layer and electrostatic barrier from pSBMA, as well as quorum sensing inhibition and disinfection from AgNPs. These findings confirm the discount effectiveness and feasibility of the pSBMA and AgNPs co-modification technique during long working time, offering valuable insights into modification operations and anti-biofouling mechanisms.

Development of microporous substrates of polyamide thin film composite membranes for pressure-driven and osmotically-driven membrane processes: A review

Pervaporation, mainly utilized to separate azeotropic mixtures, has been paid much attention for desalination in recent years due to its numerous advantages. The membranes based on thin-film composite structure have gained great interest in pervaporation due to their thin thickness, controllable hydrophilicity, and crosslinking density which affects the permeation flux and selectivity of the membranes. In this study, a polyamide thin-film composite (PA-TFC) membrane was fabricated through interfacial polymerization between amine monomers and trimesoyl chloride (TMC) on a polysulfone porous substrate (PSf). Four different diamine monomers, including ethylenediamine (EDA), triethylenetetramine (TETA), m-phenylenediamine (MPD), and piperazine (PIP) were used to investigate the effect of the monomers on the pervaporation performance of the resulting membrane for separation of sodium chloride (NaCl) and arsenate (As(v)) aqueous solution. The physicochemical properties of the membrane were characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and pure water contact angle measurement. Furthermore, the performance of the fabricated membranes was studied by pervaporation separation of 0.15 mg L−1 As(v) and 5 g L−1 NaCl aqueous solution at 40 °C, respectively. The results show that the rejections of the membrane are insignificantly affected by the chemical structures of the amines, and both the As(v) rejection and NaCl rejection are higher than 99.9%. However, the permeation flux decreases in the order of PIP-TMC membrane > TETA-TMC membrane ∼ EDA-TMC membrane > MPD-TMC membrane. Furthermore, the operating conditions are found to affect the separation performance of the PIP-TMC membrane significantly. In particular, the elevating operation temperature profoundly increases the permeation flux, while the increase in high salt concentration leads to a slight decrease in rejection but a significant decline in permeation flux. The derived membrane shows a reasonable permeation flux of 16.1 kg m−2 h−1 and ca. 99.9% rejection for 1.5 mg L−1 As(v) removal, as well as 13 kg m−2 h−1 and 99.3% rejection for 30 g L−1 NaCl separation at 60 °C. The sufficient permeation flux and good rejection of As(v) and NaCl of the membrane suggested the promising application of PA-TFC membrane for pervaporation removal of toxic arsenic from water and desalination of seawater.

Silk sericin-coated polyamide thin-film composite membranes to simultaneously improve anti-scaling properties, long-term storage, and waste-to-resource recovery

Triptycene based polyamide thin film composite membrane for high nanofiltration performance

Use of 2,4,6-pyridinetricarboxylic acid chloride as a novel co-monomer for the preparation of thin film composite polyamide membrane with improved bacterial resistance