Surface modification of nanofiltration membranes to improve the removal of organic micro-pollutants (EDCs and PhACs) in drinking water treatment: Graft polymerization and cross-linking followed by functional group substitution
- Authors
- Kim, Jae-Hyuk; Park, Pyung-Kyu; Lee, Chung-Hak; Kwon, Heock-Hoi
- Issue Date
- 15-Aug-2008
- Publisher
- ELSEVIER SCIENCE BV
- Keywords
- endocrine disrupting chemicals; pharmaceutically active compounds; nanofiltration; membrane modification
- Citation
- JOURNAL OF MEMBRANE SCIENCE, v.321, no.2, pp.190 - 198
- Journal Title
- JOURNAL OF MEMBRANE SCIENCE
- Volume
- 321
- Number
- 2
- Start Page
- 190
- End Page
- 198
- URI
- http://scholarworks.bwise.kr/ssu/handle/2018.sw.ssu/16820
- DOI
- 10.1016/j.memsci.2008.04.055
- ISSN
- 0376-7388
- Abstract
- A commercially available thin film composite (TFC) polyamide (PA) nanofiltration (NF) membrane was chemically modified to improve its rejection capacity for selected organic micro-pollutants categorized as endocrine disrupting chemicals (EDCs) and pharmaceutically active compounds (PhACs): bisphenol-A (BPA), ibuprofen, and salicylic acid. The raw NF membrane was altered using the following modification sequence: graft polymerization (methacrylic acid (MA)-membrane); cross-linking of grafted polymer chains (ethylene diamine (ED)-membrane); and, substitution of functional groups (succinic acid (SA)membrane). Attenuated total reflective Fourier transform infrared (ATR-FTIR) was used to verify each modification in the sequence: the formation of amide bonds; graft polymerization and cross-linking; and, increased carboxylic acids on the modified membrane. Based on zeta-potential and contact angle measurements, graft polymerization increased the negative charge and hydrophilicity of the raw membrane, while cross-linking replaced carboxylic acid with amide bonds, which made the modified membrane almost neutral at pH 6.5. The water fluxes of the ED- and SA-membranes were similar to that of the raw membrane; however, the water flux of the MA-membranes varied with polymerization time (the membrane polymerized for 15 min revealed >= 20% higher flux than the raw membrane). BPA rejection by the raw membrane was substantially improved from 74% to >= 95% after this series of modifications. However, the rejection capacity of the ED-membrane for ibuprofen and salicylic acid was slightly reduced compared with those of the MA-membrane, which was polymerized for 15 min, due to the lack of an electrical repulsion mechanism. The SA-membrane recovered its negative surface charge and showed a clear enhancement in the rejection of all pollutants. (c) 2008 Elsevier B.V. All rights reserved.
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