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Novel antifouling and chlorine-resistant ultrafiltration membranes were successfully fabricated using poly(vinyl chloride-co-acrylonitrile-co-sodium 4-styrenesulfonate) (PVC-PAN-PSS), a novel poly(vinyl chloride)-based copolymer, via a non-solvent induced phase separation (NIPS) method. Quartz crystal microbalance data revealed reduced levels of bovine serum albumin (BSA) adsorption on PVC-PAN-PSS films when compared to those of pure poly(vinyl chloride) and polyacrylonitrile films. The morphologies, chemical compositions, surface roughness and hydrophilicity of the membrane surfaces were characterized by field-emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle goniometer, respectively. The hydrophilicity and antifouling properties of the membranes were clearly shown to increase with increasing level of poly(sodium 4-styrene-sulfonate) (PSS) in the copolymer; the membrane with 2 wt% PSS exhibited the best antifouling properties, namely ~99% of flux recovery ratio for humic acid (1.0 g L −1 ). Furthermore, the pore structures and antifouling properties of the PVC-PAN-PSS ultrafiltration membranes were maintained after soaking in 1000 ppm sodium hypochlorite for 168 h, while common membrane additives such as methacryloyloxyethylphosphorylcholine-co-poly(propylene glycol) methacrylate and Pluronic ® F-127 were rapidly degraded in this oxidizing environment. PVC-PAN-PSS is expected to be a promising ultrafiltration membrane material with both superior antifouling properties and excellent chlorine resistance. [ABSTRACT FROM AUTHOR]

To functionalize poly(vinyl chloride) (PVC) for various applications, monomers containing tertiary amine group are incorporated into PVC via atom transfer radical polymerization (ATRP) initiated by the labile chlorines in their backbones. The kinetics of synthesis was carefully investigated, and it is proven that the grafting polymerization process can be effectively controlled by regulating the reaction time. The membranes are fabricated using PVC and copolymers by non-solvent induced phase separation (NIPS) process. The hydrophilicity and pore structure of copolymer membranes were enhanced as well, these membranes are endowed with positive charge. When PDMA% ( i.e., the PDMA weight percentage in copolymer) is 31.1%, the flux and Victoria blue B rejection are 26.0 L·m·h (0.5 MPa) and 91.2%, respectively. Thus, the newly synthesized polymer is proven to be a promising material for dye separation with positive charges. [ABSTRACT FROM AUTHOR]

To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene- block-ethylene glycol) (PE- b-PEG) via thermally induced phase separation (TIPS) process. By measuring the composition, morphology, crystallinity, ion conductivity, etc, the influence of PE- b-PEG on structures and properties of the blend separator were investigated. It was found that the incorporated PEG chains yielded higher surface energy for HDPE separator and improved affinity to liquid electrolyte. Thus, the stability of liquid electrolyte trapped in separator was increased while the interfacial resistance between separator and electrode was reduced effectively. The ionic conductivity of liquid electrolyte soaked separator could reach 1.28 × 10 S·cm at 25°C, and the electrochemical stability window was up to 4.5 V (versus Li/Li). These results revealed that blending PE- b-PEG into porous HDPE membranes could efficiently improve the performances of PE separators for lithium batteries. [ABSTRACT FROM AUTHOR]

Nanoscale permeation channels are a key factor for molecules or/and ions separation in membrane field. In this work, molecular deposition strategy is designed to construct high-performance nanochannel separation layer for selective separation of small molecules. Herein, octaammonium polyhedral oligomeric silsesquioxane (8NH 3 Cl-POSS) and tannic acid (TA), two kinds of multifunctional molecules with a size of about 1 nm, were used to prepare robust and perm-selective composite membrane through covalently-bonded layer-by-layer (LbL) self-assembly method. The optimized TA-POSS composite membrane exhibited a narrowed pore size distribution from 0.3 to 1.6 nm with a high water permeance of 21 L m−2 h−1 bar−1. The membrane showed desirable rejection of antibiotics (>90%) and enabled to separate them from NaCl solution. In addition, TA-POSS composite membrane showed outstanding stability due to the high degree of crosslinking between TA and 8NH 3 Cl-POSS and their rigid structures. This work gives a novel and green strategy to construct nanochannel composite membranes, which can efficiently separate molecules and salt. Image 1 • TA-POSS membrane was prepared by covalently-bonded LbL self-assembly method. • The membrane showed a permeance of 21 LMH/Bar with MWCO of 440 Da. • The membrane enabled to efficiently separate the antibiotics and NaCl solution. • The membrane showed good stability performance due to the cross-linked structure. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) membrane has an extensive application in the field of water treatment, but weakly negative surface-charge and even charge inversion in acidic environment restrict wide applications of traditional aromatic polyamide (PA) thin film composite (TFC) NF membrane in a broad pH range. In this work, 4, 4′-diaminostilbene-2, 2′-disulfonic acid (DSDA), a novel acidic aqueous monomer, was introduced into interfacial polymerization to fabricate a TFC NF membrane with enhanced negative charge and pH stability. The effects of interfacial polymerization parameters were investigated to improve membrane performance. The optimal membrane exhibits a pure water permeance (PWP) of 10.0 ± 0.5 L m−2 h−1·bar−1 and a high Na 2 SO 4 rejection (i.e., ~97.0%). The resultant membrane remains a strongly negative charge when the pH value is changed from 2 to 12. Due to enhanced negative charge, Donnan exclusion plays a significant role in membrane separation process, which results in a huge superiority in removal of Na 2 SO 4 , Na 3 PO 4 and K 2 Cr 2 O 7 in a broad pH range especially in acidic environment. Hence, it is demonstrated that the negative-charged NF membrane prepared in this work has improved and stable separation performance under a broad pH range, which expands application scopes of NF membrane, especially in removing Cr (VI) and phosphate in acidic environments. Besides, this study also provides a feasible route for preparation of suitable TFC NF membrane for working in acidic environment via introducing strongly acidic groups in selective layer. [Display omitted] • The thin film composite nanofiltration membrane with enhanced negative charge was fabricated. • A novel monomer-4, 4′-diaminostilbene-2, 2′-disulfonic acid was used for interfacial polymerization. • The membrane had great superiority in removal of Cr (VI) and phosphate in acidic environment. • This novel membrane expands the application range of nanofiltration in wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cationic poly(amido-amine)s (PAMAMs) were synthesized for a novel PA nanofilm. • Cationic PAMAM incorporated polyamide (PA) nanofilm is Janus charged. • Selectivity of the Janus charged PA nanofilm to mono-/divalent ions is up to 65. • The Janus charged PA nanofilm shows enhanced hard water softening performance. Nanofiltration (NF) membranes with ultra-high separation selectivity to both mono-/divalent anions and cations are desirable for treatment of practical water with complex composition of ions. In this work, a facile and universal method for fabricating polyamide (PA) NF membranes with both ultra-high separation selectivity to mono-/divalent anions and cations was developed. Cationic poly(amido-amine) (PAMAM) dendrimers with different numbers of terminal quaternary ammonium groups were synthesized and incorporated into the polyamide (PA) matrix by interfacial polymerization (IP) to modulate both charge properties and network structures of the PA nanofilms. Contributed by the heterogenous distribution of PAMAM G5-TAC2, a Janus charged PA nanofilm was successfully fabricated. The negatively charged top surface of the PA nanofilm leads to a high electrostatic repulsion to divalent anions while its positively charged back surface exerts a high electrostatic repulsion to divalent cations. Moreover, the network structures of the PA nanofilms are precisely modulated to accelerate the transport of water molecules (103.5 L m−2h−1 MPa−1). Based on the synergistic effect of steric and Donnan effects, the transports of both divalent anions and cations through the G5-TAC2/PIP membrane are hindered, while the transports of monovalent ions are free, so that both ultra-high separation selectivity to mono-/divalent anions and cations (both above 65) can be achieved. Compared to PIP only membrane, G5-TAC2/PIP membrane exhibits high-efficiency in mixed ion separation process. [ABSTRACT FROM AUTHOR]

High-efficient separation of molecules is of great significance in food, biotechnology, pharmaceutical and dairy industries. To this end, cationic hyperbranched poly (amido-amine)s (HBPs) with different numbers of quaternary ammonium groups were employed as a new kind of 3D spherical macromonomers to fabricate nanofiltration (NF) membranes, through interfacial polymerization (IP) between cationic HBPs and trimesoyl chloride (TMC) on a polyvinyl chloride ultrafiltration (PVC-UF) hollow fiber membrane surface. Apart from the inner voids inside cationic HBP molecules for fast transport of water molecules, sizes and charge properties of the outer voids between cationic HBP molecules can be modulated by changing the numbers of quaternary ammonium groups on cationic HBP molecule surfaces for enhancing both high permeability and selectivity (water permeance and MgCl 2 rejection rate of the resultant NF membrane are up to 310.5 L m−2 h−1 MPa−1 and 92.0% respectively). Based on the separation mechanism of combined steric and Donnan effects, the resultant NF membrane exhibits ultrahigh retentions to molecules with high molecular weights (MWs) or positive charges, thus molecular-level selectivity to VB12/VB2 (neutral molecules with distinct MWs) or VB1/VB2 (cationic/neutral molecules with similar MWs) can be achieved. [Display omitted] • Cationic HBPs were synthesized as a novel kind of macromonomers for IP. • Nanochannel in NF membrane selective layers were engineered by cationic HBPs. • HBP-TAC2/TMC membrane exhibits higher water permeability and MgCl 2 rejection. • Separation of molecule mixtures can be achieved based on steric and Donnan effects. [ABSTRACT FROM AUTHOR]