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Issue 43, 2016
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Polyacrylonitrile nanofiber membranes modified with ionically crosslinked polyelectrolyte multilayers for the separation of ionic impurities

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Abstract

Nanofiltration membranes were prepared by forming multilayers of branched polyethylenimine (BPEI) and polyacrylic acid (PAA) on a polyacrylonitrile (PAN) nanofibrous mat by layer-by-layer (LbL) assembly. The degree of ionization (DI) of PAA, estimated using FTIR spectra both in the absence and presence of added salt, was shown to have a strong influence on the BPEI/PAA film growth. BPEI/PAA multilayers grew exponentially when the DI of PAA was less than 30%, or when the pH of PAA during LbL formation was less than 3.5. Subsequently, BPEI/PAA multilayers were formed on the PAN nanofiber mats by depositing the polyelectrolytes at the experimental conditions that favored maximum film growth. The separation layer formed with 15 bilayers of BPEI/PAA has a thickness of 1100 nm. PAA ionization was favored within the BPEI/PAA multilayers due to the presence of abundant amine groups in BPEI, and as a result, a strong negative charge was seen for PAN nanofibrous membranes for solution conditions above pH 4.5. Nanofiber membranes modified with 15 bilayers of BPEI/PAA multilayers at an applied pressure of 4 bar had a pure water flux of 19.7 Lm−2 h−1 and a MgSO4 rejection of 98.7%. This performance represents 1.6 times higher flux and 1.1 times higher salt rejection than the multilayers formed on a conventional asymmetric polymeric support. The higher separation and higher flux capabilities of BPEI/PAA multilayer modified PAN nanofiber membranes was due to the combined effect of high charge density and high porosity of the nanofiber membranes.

Graphical abstract: Polyacrylonitrile nanofiber membranes modified with ionically crosslinked polyelectrolyte multilayers for the separation of ionic impurities

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Publication details

The article was received on 08 Aug 2016, accepted on 17 Oct 2016 and first published on 18 Oct 2016


Article type: Paper
DOI: 10.1039/C6NR06295D
Citation: Nanoscale, 2016,8, 18376-18389
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    Polyacrylonitrile nanofiber membranes modified with ionically crosslinked polyelectrolyte multilayers for the separation of ionic impurities

    S. Rajesh, Y. Zhao, H. Fong and T. J. Menkhaus, Nanoscale, 2016, 8, 18376
    DOI: 10.1039/C6NR06295D

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