Synthesis of 4-Aminobenzoylpiperazine for Preparing the Thin Film Composite Nanofiltration Membrane by Interfacial Polymerization with TMC

A new synthesis method of aromatic diamine, 4-aminobenzoylpiperazine (4-ABP), was studied from 4-aminobenzoic acid and 1-formyl piperazine for the preparation of nanofiltration membrane. The structure of 4-ABP was identified by FT-IR spectra and ¹H NMR spectra. The resulting 4-ABP was used as aqueous monomer to fabricate a thin film on porous polyethersulfone (PES) ultra filtration membranes by interfacial polymerization (IP) with trimesoyl chloride (TMC) as organic monomer. The salt rejection order of these thin film composite (TFC) nanofiltration(NF) membranes is Na₂SO₄>MgSO₄>MgCl₂>NaCl. This sequence indicated that the membranes were negatively charged.     

Silane‐Crosslinked Asymmetric Polythiosemicarbazide Membranes for Organic Solvent Nanofiltration

Crosslinked polythiosemicarbazide (PTSC) membranes with a positively charged surface are fabricated via a reaction with (3‐glycidyloxypropyl)trimethoxysilane. The integrally asymmetric ultrafiltration membranes discussed here can be easily prepared by water‐induced phase separation using a PTSC solution in dimethylsulfoxide (DMSO). The crosslinked PTSC membranes are stable in DMSO, N,N‐dimethylformamide, and tetrahydrofuran and they reject molecules of molecular weights (MW) above 1300 g mol^?1. The influence of the crosslinking agent on the surface charge, membrane solvent resistance, and membrane performance is discussed. The crosslinked asymmetric PTSC membranes totally reject Direct Red dye (MW 1373 g mol^?1), while the pristine PTSC membrane does not show any rejection for this dye. This finding suggests that an inorganic‐type‐network is formed during the crosslinking reaction, which tunes the pore size of the prepared membranes.     

Reproducible Measurement Results in Organic Solvent Nanofiltration with Ceramic Membranes

Ceramic membranes are still quite innovative to organic solvent nanofiltration. Nevertheless, flux and rejection results obtained in filtration measurements seem to depend largely on the experimental procedure, membrane production batch and setup. Therefore, an experimental approach is described, which proved to provide reproducible and reliable results that may be used as data set to derive parameters in model development.     

Enhancement of flux and solvent stability of Matrimid® thin‐film composite membranes for organic solvent nanofiltration

The development of high flux and solvent‐stable thin‐film composite (TFC) organic solvent nanofiltration (OSN) membranes was reported. A novel cross‐linked polyimide substrate, consisting of a thin skin layer with minimum solvent transport resistance and a sponge‐like sublayer structure that could withstand membrane compaction under high‐pressure was first fabricated. Then the solvent flux was significantly enhanced without compromising the solute rejection by the coupling effects of (1) the addition of triethylamine/camphorsulfonic acid into the monomer solution, and (2) the combined post‐treatments of glycerol/sodium dodecyl sulphate immersion and dimethyl sulfoxide (DMSO) filtration. Finally, the long‐term stability of the TFC membrane in aprotic solvents such as DMSO was improved by post‐crosslink thermal annealing. The novel TFC OSN membrane developed was found to have superior rejection to tetracycline (MW: 444 g/mol) but was very permeable to alcohols such as methanol (5.12 lm^?2h^?1bar^?1) and aprotic solvents such as dimethylformamide (3.92 lm^?2h^?1bar^?1) and DMSO (3.34 lm^?2h^?1bar^?1). © 2014 American Institute of Chemical Engineers AIChE J, 60: 3623–3633, 2014     

Application of Cross‐Flow Microfiltration for Purifying Solvent Naphtha with Ceramic Membranes

The microfiltration process of solvent naphtha 200 containing impurities was studied using multichannel ceramic membranes with pore diameters of 0.5 and 0.8 μm. The effects of operating time, transmembrane pressure, cross‐flow velocity, and temperature on permeate flux and rejection were investigated. The scanning electron microscop and energy dispersive spectrometry were conducted for the clean and fouled membranes. Effect of backflushing on permeate flux was also studied. Results show that it is possible to recover over 94 % of the original flux by a program of backflushing. A concentration process was carried out and furthermore, various membrane resistances were calculated. Finally, commercial detergent, HNO₃, and NaOH + NaClO cleaning stages were used for the 0.5‐μm membrane.     

Preparation of thin film nanocomposite membranes with surface modified MOF for high flux organic solvent nanofiltration

Preparation of defect‐free and optimized thin film nanocomposite (TFN) membranes is an effective way to enhance the process of organic solvent nanofiltration. However, it still remains a great challenge due to poor filler particle dispersibility in organic phase and compatible issue between fillers and polymers. Aiming at these difficulties, UiO‐66‐NH₂ nanoparticles were surface modified with long alkyl chains and used in the preparation of TFN membranes. As a result, defect‐free TFN membranes with ultrathin MOF@polyamide layer were successfully prepared benefited from the improved particle dispersibility in n‐hexane. Significant enhancement was found in methanol permeance after nanoparticle incorporation, without comprising the tetracycline rejection evidently. Especially, the novel TFN membrane prepared with organic phase solution containing 0.15% (w/v) modified UiO‐66‐NH₂ nanoparticles showed a superior methanol permeance of 20 L·m^?2·h^?1·bar^?1 and a tetracycline rejection of about 99%, which is appealing to the application in pharmaceutical industry for example. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1303–1312, 2017     

Development of thin‐film composite hollow‐fiber membranes from modified polyphenylene oxide for gas separation applications

The effect of sulfonation and bromination‐sulfonation on the gas transport properties of polyphenylene oxide has been investigated. These high‐performance modified polymers have been studied in the form of TFC membranes by solution coating on the skin side of polyetherimide hollow fibers. TFC membrane modules prepared from sulfonated‐brominated polyphenylene oxide as the active layer coated on polyetherimide hollow fibers. Stability of the TFC membranes was greatly improved when a wet feed stream was used instead of a dry one. Water vapor in the feed stream most likely prevented the active layer from stress cracking on drying. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 275–282, 2001     

A study on the characteristics and pervaporation performance of polyamide thin‐film composite membranes with modified polyacrylonitrile as substrate for bioethanol dehydration

To improve the pervaporation performance in separating an aqueous ethanol solution, polyamide thin‐film composite (TFC) membranes (m‐tolidine‐H‐TMC/mPAN) were prepared through the interfacial polymerization reaction between trimesoyl chloride (TMC) and 2,2'‐dimethylbenzidine hydrochloride (m‐tolidine‐H) on the surface of a modified polyacrylonitrile (mPAN) membrane. The effects of the feed ethanol concentration on the pervaporation performance and the durability of m‐tolidine‐H‐TMC/mPAN TFC membranes were investigated. To choose the optimal mPAN membrane as the TFC substrate, the effect of hydrolysis time on the chemical properties and separation performance of an mPAN substrate was also studied. An appropriate hydrolysis time of 15 min was chosen to obtain the mPAN substrate due to the corresponding high permeation flux. The m‐tolidine‐H‐TMC/mPAN TFC membrane exhibited a high pervaporation performance for ethanol dehydration. A positron annihilation lifetime spectroscopy experiment was used to estimate the mean free‐volume radius of the m‐tolidine‐H‐TMC polyamide selective layer, which lay between the radii of the water and ethanol molecules. © 2013 Society of Chemical Industry     

Engineering design of outer‐selective tribore hollow fiber membranes for forward osmosis and oil‐water separation

Outer‐selective thin‐film composite (TFC) hollow fiber membranes offer advantages like less fiber blockage in the feed stream and high packing density for industrial applications. However, outer‐selective TFC hollow fiber membranes are rarely commercially available due to the lack of effective ways to remove residual reactants from fiber's outer surface during interfacial polymerization and form a defect‐free polyamide film. A new simplified method to fabricate outer‐selective TFC membranes on tribore hollow fiber substrates is reported. Mechanically robust tribore hollow fiber substrates containing three circular‐sector channels were first prepared by spinning a P84/ethylene glycol mixed dope solution with delayed demixing at the fiber lumen. The thin wall tribore hollow fibers have a large pure water permeability up to 300 L m^?2 h^?1 bar^?1. Outer‐selective TFC tribore hollow fiber membranes were then fabricated by interfacial polymerization with the aid of vacuum sucking to ensure the TFC layer well‐attached to the substrate. Under forward osmosis studies, the TFC tribore hollow fiber membrane exhibits a good water flux and a small flux difference between active‐to‐draw (i.e., the active layer facing the draw solution) and active‐to‐feed (i.e., the active layer facing the feed solution) modes due to the small internal concentration polarization. A hyperbranched polyglycerol was further grafted on top of the newly developed TFC tribore hollow fiber membranes for oily wastewater treatment. The membrane displays low fouling propensity and can fully recover its water flux after a simple 20‐min water wash at 0.5 bar from its lumen side, which makes the membrane preferentially suitable for oil‐water separation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4491–4501, 2015     

Alkyl amine functional dextran macromonomer‐based thin film composite loose nanofiltration membranes for separation of charged and neutral solutes

Thin film composite (TFC) nanofiltration membranes with defined porous structure of the separation layer are desirable for the concentration of neutral solute and separation of salts from a mixture. Herein, we report the formation of TFC membranes composed of polyamide (PA) separation layer by the interfacial polymerization between new dextran‐butyl amine (Dex‐NH₂) macromonomer and trimesoyl chloride on polysulfone support membrane. The membranes prepared with 1%–1.5% (wt/vol) of Dex‐NH₂ exhibited water permeance of 110–116 L m^?2 h^?1 MPa^?1 with 62%–71% rejection of Na₂SO₄ and 12%–14% rejection of MgCl₂. The membranes also showed about 91% rejection of poly(ethylene glycol) of molecular weight 2000 g/mol and about 11% rejection of NaCl. A decrease in permeance and ions selectivity was observed with increasing concentration of Dex‐NH₂. The dextran chains attached to the PA network restrict the diffusion of Dex‐NH₂ toward the interfacial zone and thereby assist the formation of porous and thin PA layer compared to that when free amine (alkyl diamine) was used. These membranes are applicable for the separation of small molecular weight neutral solutes from mixture containing monovalent salts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45301.     

Electrospun Sandwich‐Structure Composite Membranes for Wound Dressing Scaffolds with High Antioxidant and Antibacterial Activity

In this study, the sandwich‐structured composite (SSC) membranes with well‐antibacterial and antioxidant properties, which have the promising application as wound dressing, are successfully fabricated by combining an electrospinning process. The SSC membranes are composed of three layers, including the bottom polyvinylidene fluoride fibrous layer, the middle curcumin/polylactic acid (PLA) microsphere layer, and the top enrofloxacin/PLA fibrous layer, respectively. The obtained SSC membranes are characterized in terms of morphology, component, and mechanical property using scanning electronic microscope, X‐ray diffractometer, Fourier transform infrared spectroscopy, and universal electronic testing machine, respectively. Moreover, in vitro drug release, antioxidant activity, antimicrobial activity, and biocompatibility of the SSC membranes are also evaluated. The results showed that the obtained composite membranes indeed possess the sandwich structure, where the middle microsphere layer is located between two fibrous surface layers. It is found that the drug‐loaded SSC membranes show excellent antioxidant activity against ^?OH and DPPH free radicals and antibacterial activity against Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Candida albicans. The combination of electrospinning and electrospraying opens up a new way to fabricate a variety of composite membranes with a sandwich structure, which have promising potential application as wound dressing scaffolds.