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.

STUDY ON THE DESALINATION BEHAVIORS OF PA/PSF THIN FILM COMPOSITE

A polypiperazine amide （PA）/polysulfone （PSF） thin film composite （TFC） was prepared by interracial polymerization （IP） using a trimesoyl chloride hexane solution as the oil phase and a piperazine aqueous solution as the water phase on a porous polysulfone hollow fiber substrate. Its separating behaviors were investigated systematically to various salts such as NaCl KCl, Na2SO4, MgCl2, CaCl2 and MgSO4, showing the highest rejection rate to Na2SO4, the second to MgSO4 the third to MgCl2 and CaCl2, and the lowest to KCI, NaCl, being 99%, 98%, 70%, 60%, 15% and 10% respectively. Under an increasing pressure or with time, the rejection rate of the TFC rises to a plateau. To various concentration of the feed, the rejection rate reduced gradually with the higher concentration.

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.

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.

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.

Magnetostatic Coupling in CoFe204/Pb（Zr0.53Ti0.47）O3 Magnetoelectric Composite Thin Films of 2-2 Type Structure

CoFe204/Pb（Zr0.53Ti0.47）O3 （CFO/PZT） magnetoelectric composite thin films of 2-2 type structure had been prepared onto Pt/Ti/SiO2/Si substrate by a sol-gel process and spin coat- ing technique. The structure of the prepared thin film is substrate/PZT/CFO/PZT/CFO. Two CFO ferromagnetic layers are separated from each other by a thin PZT layer. The upper CFO layer is magnetostatically coupled with the lower CFO layer. Subsequent scan- ning electron microscopy （SEM） investigations show that the prepared thin films exhibit good morphologies and compact structure, and cross-sectional micrographs clearly display a multilayered nanostructure of multilayered thin films. The composite thin films exhibit both good magnetic and ferroelectric properties. The spacing between ferromagnetic layers can be varied by adjusting the thickness of intermediate PZT layer. It is found that the strength of magnetostatic coupling has a great impact on magnetoelectric properties of composite thin films, i.e., the magnetoelectric voltage coefficient of composite thin film tends to increase with the decreasing of pacing between two neighboring CFO ferromagnetic layers as a result of magnetostatic coupling effect.

Composition change and capacitance properties of ruthenium oxide thin film

Ru O2·n H2O film was deposited on tantalum foils by electrodeposition and heat treatment using Ru Cl3·3H2O as precursor.Surface morphology, composition change and cyclic voltammetry from precursor to amorphous and crystalline RuO2·n H2O films were studied by X-ray diffractometer, Fourier transformation infrared spectrometer, differential thermal analyzer, scanning electron microscope and electrochemical analyzer, respectively. The results show that the precursor was transformed gradually from amorphous to crystalline phase with temperature. When heat treated at 300 °C for 2h, RuO2·n H2O electrode surface gains mass of2.5 mg/cm2 with specific capacitance of 782 F/g. Besides, it is found that the specific capacitance of the film decreased by roughly20% with voltage scan rate increasing from 5 to 250 m V/s.

AC Impedance Spectroscopy of a-nc-Si:H Thin Films

The AC impedance of amorphous-nano-crystalline silicon composite thin films (a-nc-Si:H) from mHz to MHz at different temperatures has been studied. The samples were prepared by Plasma Enhanced Chemical Vapor Deposition technique. The X-ray diffraction and high resolution electron microscopy showed that films consist of isolated nano-crystals embedded in amorphous matrix. In analysis of impedance data, two approaches were tested: the ideal Deby type equivalent circuit and modified one, with CPE (constant phase elements). It was found that the later better fits to results. The amorphous matrix showed larger resistance and lower capacity than nano-crystals. By heat treatment in vacuum, the capacity for both phases changes, according to expected change in size of ordered domains.

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.

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.