Polyelectrolyte Modified Graphene Oxide/Polypropylene Composite Membranes for Organic Solvent Nanofiltration

Polyelectrolyte Modified Graphene Oxide/Polypropylene Composite Membranes for Organic Solvent Nanofiltration

Dan Hua and Tai-Shung Chung^∗

Department of Chemical & Biomolecular Engineering, National University of Singapore, Singapore 117585, Singapore

* Corresponding author. Tel.: (+65) 6516 6645; fax: (+65) 6779 1936.

E-mail address: chencts@nus.edu.sg (T. S. Chung).

Abstract:

In this work, we have molecularly designed graphene oxide (GO) /polypropylene (PP) composite membranes by three steps: (1) grafting the PP surface with polyethylene glycol (PEG) with the aid of argon plasma (TPP), (2) a pressure-assisted filtration of GO dispersion and (3) functionalization by various polyelectrolytes. The fabricated polyelectrolyte modified GO/PP composite membranes not only show excellent adhesion between the GO layer and PP support, but also  exhibit satisfying separation performance for organic solvent nanofiltration (OSN) of dye/ethanol mixtures. It is interesting to find that the TPP/GO membrane with hyperbranched polyethylenimine (HPEI) modified on its outmost layer has high rejections toward cationic dyes. It has a rejection of 95% toward Alcian blue with a high permeance of 14.9 L m^-2 h^-1 bar^-1. Similarly, it exhibits excellent anionic dye/ethanol separation with poly(styrenesulfonate) (PSS) modified on its outmost layer. It shows a rejection up to 97% toward Rose bengal with a total permeance of 3.1 L m^-2 h^-1 bar^-1. Experimental results indicate that both molecular sieving and electrostatic repulsion are critical factors for GO based membranes to separate dye/organic solvent mixtures. This work may both widen the selection of membrane support materials for GO deposition and provide useful insights for developing GO based membranes for OSN.

Acknowledgements

The authors are grateful to National Research Foundation, Prime Minister¡¯s Office, Singapore for funding this research under its Competitive Research Program for the project entitled, ¡°Development of solvent resistant nanofiltration membranes for sustainable pharmaceutical and petrochemical manufacture¡±; (CRP Award NO. NRF-CRP14-2014-01 (NUS grant number: R-279-000-466-281)). Special thanks are due to Dr. Gui Min Shi, Ms. Yu Zhang, Miss Anastasia Frances Frederica and Miss Jie Gao for their valuable suggestions and help.