Deciphering the Role of Amine Concentration on Polyamide Formation toward Enhanced RO Performance

Lu Elfa Peng, Qimao Gan, Zhe Yang, Li Wang, Peng Fei Sun, Hao Guo, Hee Deung Park, Chuyang Y. Tang

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Polyamide surface morphology and its underneath nanosized voids have crucial influence on the separation performance of thin film composite (TFC) polyamide reverse osmosis membranes. Although there have been numerous studies reporting the impact of amine monomer concentration on polyamide formation and membrane performance, the observations and interpretations in the existing literature remain controversial. In this study, we performed interfacial polymerization (IP) of polyamide films over a wide range of m-phenylenediamine (MPD) concentration (0.05-8.0 w/w %). For the first time, we demonstrate that the water permeance of the resultant TFC membranes is governed by the competing effects of (1) promoted polyamide film growth for forming thicker polyamide films and (2) improved nanofoaming effect that results in more extensive nanovoids at higher MPD concentrations. To dissect these competing mechanisms, we further adopted a free-interface IP strategy to suppress the nanofoaming effect. The corresponding polyamide nanofilms had negligible nanovoids and monotonously increased film thickness, leading to decreased water permeance at high MPD concentrations. In contrast, the conventional TFC membranes exhibited optimal water permeance at the intermediate MPD concentration of 2.0 w/w %, which results from the trade-off between improved nanovoid formation (which promotes higher permeance) and increased film growth (which limits permeance). On the other hand, the better film growth at greater MPD concentration was generally beneficial for achieving better membrane rejection. The current study unveils the fundamental chemistry-morphology-performance relationship of TFC polyamide membranes and provides important implications on their synthesis and environmental applications.

Original languageEnglish
Pages (from-to)903-912
Number of pages10
JournalACS ES and T Engineering
Issue number5
Publication statusPublished - 2022 May 13

Bibliographical note

Funding Information:
The work is fully supported by a grant from the Research Grants Council of the Hong Kong Special Administration Region, China (SRFS2021-7S04).

Publisher Copyright:
© 2022 American Chemical Society.


  • amine concentration
  • interfacial polymerization
  • nanofoaming theory
  • polyamide film
  • reverse osmosis membrane

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Chemical Health and Safety
  • Process Chemistry and Technology
  • Environmental Chemistry


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