Anti-fouling graphene-based membranes for effective water desalination

Dong Han Seo,Yun Chul Woo,Ho Kyong Shon,Sung Il Lim,Adrian T Murdock,Zhao Jun Han,Shafique Pineda,Malcolm Lawn,Yalong Jiao,Teng Yong Ng,Myoung Jun Park,Kostya Ostrikov,Graeme Millar,Fabricio Frizera Borghi,Ming Xie,Aijun Du,Stephen Gray,Elisa Y M Ang

doi:10.1038/s41467-018-02871-3

Abstract

The inability of membranes to handle a wide spectrum of pollutants is an important unsolved problem for water treatment. Here we demonstrate water desalination via a membrane distillation process using a graphene membrane where water permeation is enabled by nanochannels of multilayer, mismatched, partially overlapping graphene grains. Graphene films derived from renewable oil exhibit significantly superior retention of water vapour flux and salt rejection rates, and a superior antifouling capability under a mixture of saline water containing contaminants such as oils and surfactants, compared to commercial distillation membranes. Moreover, real-world applicability of our membrane is demonstrated by processing sea water from Sydney Harbour over 72 h with macroscale membrane size of 4 cm2, processing ~0.5 L per day. Numerical simulations show that the channels between the mismatched grains serve as an effective water permeation route. Our research will pave the way for large-scale graphene-based antifouling membranes for diverse water treatment applications.

Highlights

The inability of membranes to handle a wide spectrum of pollutants is an important unsolved problem for water treatment
The permeable graphene is grown by an ambient-air chemical vapour deposition (CVD) process, described in more detail elsewhere[18], and wettransferred to a commercial polytetrafluoroethylene (PTFE) MD membrane
The ambient-air CVD process enables the growth of continuous graphene films with a high density of nanocrystalline grain boundaries on polycrystalline Ni substrate, which are desirable as water vapour-permeable channels

Summary

Introduction

The inability of membranes to handle a wide spectrum of pollutants is an important unsolved problem for water treatment. Key advantageous features of the MD process include water production almost independent of the feed solution salinity, and the potential to reject majority of non-volatile constituents, such as dissolved salt, organics, colloids and the ability to utilise low-grade waste heat to drive the process These merits enable MD to be a promising green technology for zero liquid discharge purification processes[8]. Conventional MD membrane’s heat conduction across the membrane often leads to low water vapour flux with degradation of performance over a long period of operation that remains as another significant challenge[12] Such limitations of conventional membranes necessitate new materials for antifouling membranes to successfully address these challenges. Most of these methods have been unable to achieve antifouling membranes that demonstrated high water vapour flux and long-term stability during MD operation under diverse mixtures of membranedamaging contaminants[13,14]

Methods

Results

Conclusion