Preparation of Thin Film Composite Nanofiltration Membrane by Interfacial Polymerization with 3,5-Diaminobenzoylpiperazine and Trimesoyl Chloride

A new aromatic diamine,3,5-diaminobenzoylpiperazine （3,5-DABP）,was synthesized from 3,5-diaminobenzoic acid and 1-formyl piperazine.The structure of 3,5-DABP was identified by FT-IR spectra and 1H NMR spectra.With 3,5-DABP as aqueous monomer and trimesoyl chloride （TMC） as organic monomer,thin film composite （TFC） nanofiltration membranes were prepared by interfacial polymerization technology.The salt rejection order of these TFC membranes is Na2SO4MgSO4MgCl2NaCl.This sequence indicates that the membranes are negatively charged.

Reducing active layer thickness of polyamide composite membranes using a covalent organic framework interlayer in interfacial polymerization

Polyamide(PA)-based thin-film composite membranes exhibit enormous potential in water purification,owing to their facile fabrication,decent performance and desirable stability.However,the thick PA active layer with high transport resistance from the conventional interfacial polymerization hampers their applications.The controllable fabrication of a thin PA active layer is essential for high separation efficiency but still challenging.Herein,a covalent organic framework TpPa-1 interlayer was firstly deposited on a polyethersulfone(PES)substrate to reduce the thickness of PA active layer in interfacial polymerization.The abundant pores of TpPa-1 increase the local concentration of amine monomers by adsorbing piperazine molecules,while hydrogen bonds between hydrophilic groups of TpPa-1 and piperazine molecules slow down their diffusion rate.Arising from those synergetic effects,the PA active layer is effectively reduced from 200 nm to 120 nm.By optimizing TpPa-1 interlayer and PA active layer,the water flux of resultant membranes can reach 171.35 L·m^-2·h^-1·MPa^-1,which increased by 125.4%compared with PA/PES membranes,while the rejection rates of sodium sulfate and dyes solution remained more than 90%and 99%,respectively.Our strategy may stimulate rational design of ultrathin PA-based nanofiltration membranes with high performances.

Pebax/TSIL blend thin film composite membranes for CO_2 separation

In this study a thin film composite （TFC） membrane with a Pebax/Task-specific ionic liquid （TSIL） blend selective layer was prepared. Defect-flee Pebax/TSIL layers were coated successfully on a polysulfone ultrafiltration porous support with a poly- dimethylsiloxane （PDMS） gutter layer. Different parameters in the membrane preparation （e.g. concentration, coating time） were investigated and optimized. The morphology of the membranes was studied by scanning electron microscopy （SEM）, while the thermal properties and chemical structures of the membrane materials were investigated by thermo-gravimetric ana- lyzer （TGA）, differential scanning calorimetry （DSC） and Fourier transform infrared spectroscopy （FTIR）. The CO2 separation performance of the membrane was evaluated using a mixed gas permeation test. Experimental results show that the incorpora- tion of TSIL into the Pebax matrix can significantly increase both C02 permeance and CO2/N2 selectivity. With the presence of water vapor, the membrane exhibits the best CO2/N2 selectivity at a relative humidity of around 75%, where a CO2 permeance of around 500 GPU and a CO2/N2 selectivity of 46 were documented. A further increase in the relative humidity resulted in higher CO： permeance but decreased COIN2 selectivity. Experiments also show that CO2 permeance decreases with a CO2 partial pressure increase, which is considered a characteristic in facilitated transport membranes.

Surface-tailoring chlorine resistant materials and strategies for polyamide thin film composite reverse osmosis membranes

Polyamide thin film composite membranes have dominated current reverse osmosis market on account of their excellent separation performances compared to the integrally skinned counterparts.Despite their very promising separation performance,chlorine-induced degradation resulted from the susceptibility of polyamide toward chlorine attack has been regarded as the Achilles’s heel of polyamide thin film composite.The free chlorine species present during chlorine treatment can impair membrane performance through chlorination and depolymerization of the polyamide selective layer.From material point of view,a chemically stable membrane is crucial for the sustainable application of membrane separation process as it warrants a longer membrane lifespan and reduces the cost involved in membrane replacement.Various strategies,particularly those involved membrane material optimization and surface modifications,have been established to address this issue.This review discusses membrane degradation by free chlorine attack and its correlation with the surface chemistry of polyamide.The advancement in the development of chlorine resistant polyamide thin film composite membranes is reviewed based on the state-of-the-art surface modifications and tailoring approaches which include the in situ and postfabrication membrane modifications using a broad range of functional materials.The challenges and future directions in this field are also highlighted.

Poly(vinylidene fluoride) membrane based thin film microextraction for enrichment of benzoylurea insecticides from water samples followed by their determination with HPLC

Thin-film microextraction（TFME）,a new geometry for solid-phase microextraction,has become an attractive sample-preparation technique.Compared to other microextraction approaches,the sensitivity of this technique was enhanced without sacrificing the sampling time due to the high surface area-tovolume ratio together with the increase of extraction-phase volume.In this paper,a new TFME method based on poly（vinylidene fluoride） membrane was developed for the extraction of benzoylurea insecticides（diflubenzuron,triflumuron,hexaflumuron and teflubenzuron） from water samples followed by their determination with high performance liquid chromatography-diode array detection.Under the optimal conditions,good linearity was observed over the concentration range of 0.5-100.0 ng/mL with correlation coefficient greater than 0.9994.The limits of detection（S/N = 3） of the method for the target analytes were 0.1 ng/mL.Mean recoveries ranged from 87.7% to 103.9% with relative standard deviations lower than 6.5%.The results indicated that the developed TFME method is simple,efficient,and cost effective.

Polydopamine/Imogolite Nanotubes(PDA/INTs)Interlayer Modulated Thin Film Composite Forward Osmosis Membrane for Minimizing Internal Concentration Polarization

Forward osmosis(FO)as an energy-saving membrane process has attracted much attention in food concentration,water treatment,and desalination.Thin film composite(TFC)membrane is the most popular FO membrane,but it suffers from the internal concentration polarization(ICP),which significantly limits the water flux and FO efficiency.In this report,we demonstrate a novel and high-performing thin film nanocomposite(TFN)membrane that employs a hydrophilic interlayer composed of imogolite nanotubes(INTs)and polydopamine(PDA).The INTs can be adhered to the porous substrate by the self-polymerization of PDA,and the as-prepared PDA/INTs interlayer displays a nanostructured network with outstanding hydrophilicity.The detailed investigation was conducted to understand the relationship between the structure and property of the PDA/INTs interlayer and the morphology and performance of the TFN membrane.The TFN membrane with the PDA/INTs interlayer performs a thinner and smoother polyamide selective layer.Correspondingly,the TFN membrane shows a water flux of 18.38 L·m^(-2)·h^(-1),which is 2.18 times of the pristine TFC membrane.Moreover,the TFN membrane has a minimized structural parameter(577μm),almost a half of that of the pristine one(949μm).It reveals that the ICP effect of TFC membrane can be effectively alleviated by using a hydrophilic PDA/INTs interlayer.This TFN membrane with a satisfactory water permeability is promising in terms of future applications.

The effect of altering crosslinker chemistry during interfacial polymerization on the performance of nanofiltration membranes for desalination, organic, and micropollutants removal

Chemistry of the polyamide active layer of a desalination membrane is critical in determining both its physical and chemical properties.In this study,we designed and fabricated three novel membranes with different active layers using the crosslinkers:terephthaloyl chloride,isophthaloyl chloride,and trimesoyl chloride.The crosslinkers were reacted with an aqueous solution of an aliphatic tetra-amine.Because these crosslinkers differ in their structures and crosslinking mechanisms during interfacial polymerization,the resultant membranes also possess different structural properties.The water contact angle of the fabricated membranes also varies;the water contact angles of 4A-3P-TPC@PSF/PET,4A-3P-TMC@PSF/PET,and 4A-3P-IPC@PSF/PET,are 68.9°,65.6°,and 53.9°,respectively.Similarly,the desalination performance of resultant membranes also showed variations,with 4A-3P-TPC@PSF/PET,4A-3P-IPC@PSF/PET,and 4A-3P-TMC@PSF/PET having a permeate flux of 17.14,25.70,and 30.90 L·m^(−2)·h^(−1),respectively,at 2.5 MPa.The 4A-3P-TPC@PSF/PET membrane exhibited extensive crosslinking with aliphatic linear amine,and cationic dye rhodamine B,MgCl_(2),and amitriptyline rejection rates of 98.6%,92.7%and 80.9%,respectively.The 4A-3P-TMC@PSF/PET membrane showed mediocre performance,while 4A-3P-IPC@PSF/PET membrane showed even lower performance,with a 35%rejection of methyl orange dye.

Recent Advances in Metal-Organic Cages-Based Composite Membranes

Conventional polymeric membranes face several limitations,such as the trade-off between permeability and selectivity,and physical aging or membrane fouling.In this case,fabrication of composite membranes,usually including mixed matrix membranes(MMMs)or thin film nanocomposite(TFN)membranes by introduction of porous materials as fillers has gained much attention.To achieve excellent membrane performance,it is of great importance to select proper porous materials to avoid agglomeration or precipitation during the composite membrane fabrication processes.Metal-organic cages(MOCs)have been explored as additives for the fabrication of defectfree composite membranes owing to their diversified topologies,well-defined pore structures,nanoscale size,and excellent solubility.This review mainly focuses on the recent advances in applications of MOCs for membrane separation,including synthetic artificial channels,reverse osmosis,nanofiltration,pervaporation and gas separation.Besides,two types of MOCs that have been extensively investigated for composite membrane fabrication are also highlighted.Furthermore,challenges and possible directions are also discussed in details,hoping to provide insightful guidance on the development of more MOC-based membranes with impressive separation performance.