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[Display omitted] • A novel binary organic phosphonic acid was firstly integrated into nanofiltration membrane. • The rejection of membrane incorporated with AA was improved, while the permeability exhibited no decline. • Mono-/divalent anion selective separation factor surpass 500 even in high saline solution up to 20 g/L. • The membrane exhibit excellent chlorine resistance and anti-fouling performance. Nanofiltration membrane (NF) have become increasingly crucial in ion separation. However, traditional polyamide (PA) NF suffers from poor selectivity for mono-/divalent anions due to weak charges and structure defects. Thus, a novel binary organic phosphonic acid, alendronic acid (AA), was firstly used as an aqueous co-monomer via interfacial polymerization (IP) to create negatively charged nanofiltration membranes with both higher charge density and pore size homogeneity for the separation of mono-/divalent anions. Both structure characterization and performance tests demonstrated the successful introduction of AA in the separation layer. Compared with pristine membrane, the NaCl/Na 2 SO 4 selectivity of membrane incorporated with AA was four times improved, while the permeability exhibited no decline. Simultaneously, the separation efficiency of Cl-/SO 4 2- was tested in NaCl/Na 2 SO 4 binary mixed solutions with varying total concentrations and different mass ratios, and the separation factor consistently exceeded 500 across a concentration range of 1 g/L to 20 g/L. Moreover, the AA-integrated membrane exhibited excellent chlorine resistance after 20000 ppm·h of chlorine treatment, which is promising for high efficiency separation of mono-/divalent anions in industrial applications. [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]