1. Janus charged polyamide nanofilm with ultra-high separation selectivity for mono-/divalent ions.
- Author
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Qiu, Ze-Lin, Yu, Wen-Han, Shen, Yu-Jie, Zhu, Bao-Ku, and Fang, Li-Feng
- Subjects
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IONS , *WATER softening , *POLYAMIDES , *COMPLEX ions , *WATER hardness , *MEMBRANE separation - Abstract
[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]
- Published
- 2021
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