Ionic Liquid-Reduced Graphene Oxide Membrane with Enhanced Stability for Water Purification

Rahul S Zambare; Xiaoxiao Song; S Bhuvana; Chuyang Y Tang; J S Antony Prince; Parag R Nemade

doi:10.1021/acsami.2c12488

Ionic Liquid-Reduced Graphene Oxide Membrane with Enhanced Stability for Water Purification

ACS Appl Mater Interfaces. 2022 Sep 28;14(38):43339-43353. doi: 10.1021/acsami.2c12488. Epub 2022 Sep 13.

Authors

Rahul S Zambare^{1

2}, Xiaoxiao Song³, S Bhuvana², Chuyang Y Tang⁴, J S Antony Prince², Parag R Nemade¹

Affiliations

¹ Department of Chemical Engineering, Institute of Chemical Technology (ICT), Nathalal Parekh Marg, Matunga, Mumbai 400019, India.
² Environmental and Water Technology Centre of Innovation (EWTCOI), Ngee Ann Polytechnic, Singapore 599489, Singapore.
³ Centre for Membrane and Water Science and Technology, Ocean College, Zhejiang University of Technology, Hangzhou 310014, China.
⁴ Department of Civil Engineering, The University of Hong Kong, Pok Fu Lam, Hong Kong 999077, China.

PMID: 36099395
DOI: 10.1021/acsami.2c12488

Abstract

There has been a growing interest in water purification by graphene oxide (GO) laminate membranes due to their exceptional hydrophilicity, high throughput, and extraordinary separation performance originating from their two-dimensional and well-defined nanostructure. However, the swelling and stability in an aqueous environment are areas of concern for the GO laminate membranes. Here, a novel methylimidazolium ionic liquid-reduced GO (mimG)-assembled GO laminate membrane (mimG-GO) with remarkable stability was fabricated by a vacuum-assisted strategy for water purification. Methylimidazolium-based ionic liquid-reduced graphene oxide (mimG) was prepared by a facile nucleophilic ring-opening mechanism. Fabricated membranes were thoroughly characterized for stability, structural, permeance, and rejection properties in an aqueous environment. A combination of cationic mimG and GO nanosheets improves membrane stability in the aqueous environment via cation-π interactions and creates nanofluidic channels for facile water transport while yielding significant enhancement in the salt and dye separation performance. The pore size and the number of nanofluidic channels were precisely controlled via material deposition and laminate thickness to remove salts from water. The mimG-GO laminate membrane containing 72.2 mg m^-2 deposition showed a permeance of 14.9 LMH bar^-1, 50% higher than 9.7 LMH bar^-1 of the neat GO laminate membrane, in addition to an increase in Na₂SO₄ salt rejection from 46.6 to 77.4%, overcoming the flux-rejection trade-off. The mimG-GO laminate membrane also rejected various anionic dyes (i.e., 99.9% for direct red 80 (DR 80), 96.8% for reactive black 5 (RB 5), and 91.4% for methyl orange (MO)). The mimG-GO laminate membrane containing 361.0 mg m^-2 deposition showed the highest rejection for Na₂SO₄ (92.1%) and 99.9% rejection for DR 80, 99.0% rejection for RB 5, and 98.1% rejection for MO dyes keeping a flux of 2.6 LMH bar^-1. Partial reduction and covalent grafting of ionic liquid moieties on GO helped to enhance the cation-π interaction between GO laminates, which showed enhanced stability, frictionless water transport, with high salt and dye rejection. Moreover, a simultaneous improvement in water permeance and solute rejection reveals the great potential of ionic liquid-functionalized GO laminate membranes for water-based applications.

Keywords: dye rejection; graphene oxide; graphene oxide membrane; methylimidazolium ionic liquid; salt rejection.