Surface modification of nanofiltration membranes to improve the removal of organic micropollutants: Linking membrane characteristics to solute transmission

Shiyang Huang; James A McDonald; Rhiannon P Kuchel; Stuart J Khan; Greg Leslie; Chuyang Y Tang; Jaleh Mansouri; Anthony G Fane

doi:10.1016/j.watres.2021.117520

Surface modification of nanofiltration membranes to improve the removal of organic micropollutants: Linking membrane characteristics to solute transmission

Water Res. 2021 Sep 15:203:117520. doi: 10.1016/j.watres.2021.117520. Epub 2021 Aug 6.

Authors

Shiyang Huang¹, James A McDonald², Rhiannon P Kuchel³, Stuart J Khan², Greg Leslie¹, Chuyang Y Tang⁴, Jaleh Mansouri⁵, Anthony G Fane⁶

Affiliations

¹ UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, The University of New South Wales (UNSW), Sydney, NSW 2052, Australia.
² Water Research Centre, School of Civil and Environmental Engineering, UNSW, Sydney, NSW 2052, Australia.
³ Electron Microscopy Unit, Mark Wainwright Analytical Centre, UNSW, Sydney, NSW 2052, Australia.
⁴ Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong 999077, China.
⁵ UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, The University of New South Wales (UNSW), Sydney, NSW 2052, Australia. Electronic address: j.mansouri@unsw.edu.au.
⁶ UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, The University of New South Wales (UNSW), Sydney, NSW 2052, Australia. Electronic address: a.fane@unsw.edu.au.

PMID: 34392040
DOI: 10.1016/j.watres.2021.117520

Abstract

Surface modification of nanofiltration (NF) membranes has great potential to improve the removal of organic micropollutants (OMs) by NF membranes. This study used polydopamine (PDA) as a model coating to comprehensively link the changes in membrane properties with the changes in transmission of 34 OMs. The membrane characterization demonstrated that a thicker, denser, and more hydrophilic PDA coating can be achieved by increasing the PDA deposition time from 0.5 to 4 hours. Overall, the transmissions of target OMs were reduced by PDA-coated NF membranes compared to unmodified NF membranes. The neutral hydrophobic compounds showed lower transmissions for longer PDA coating (PDA4), while the neutral hydrophilic compounds tended to show lower transmissions for shorter PDA coating (PDA0.5). To explain this, competing effects provided by the PDA coatings are proposed including sealing defects, inducing cake-enhanced concentration polarization in the coating layer for neutral hydrophilic compounds, and weakened hydrophobic adsorption for neutral hydrophobic compounds. For charged compounds, PDA4 with the greatest negative charge among the PDA-coated membranes showed the lowest transmission. Depending on the molecular size and hydrophilicity of the compounds, the transmission of OMs by the PDA4 coating could be reduced by 70% with only a 26.4% decline in water permeance. The correlations and mechanistic insights provided by this work are highly useful for designing membranes with specific surface properties via surface modification to improve the removal of OMs without compromising water production.

Keywords: Nanofiltration membrane; Organic micropollutants; Solute transport; Surface modification.

MeSH terms

Adsorption
Hydrophobic and Hydrophilic Interactions
Membranes, Artificial
Surface Properties
Water Purification*

Substances

Membranes, Artificial