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

Area of Science:

• Materials Science
• Nanotechnology
• Environmental Science

Background:

• Graphene oxide (GO) laminate membranes show promise for water purification due to their unique nanostructure, hydrophilicity, and high throughput.
• However, challenges remain regarding the swelling and long-term stability of GO membranes in aqueous environments.
• Addressing these limitations is crucial for advancing GO-based water treatment technologies.

Purpose of the Study:

• To fabricate a novel methylimidazolium ionic liquid-reduced GO (mimG)-assembled GO laminate membrane (mimG-GO) with enhanced stability and separation performance for water purification.
• To investigate the structural, stability, permeance, and rejection properties of the mimG-GO membrane in aqueous environments.
• To explore the potential of ionic liquid functionalization in overcoming the trade-off between flux and rejection in GO membranes.

Main Methods:

• Fabrication of methylimidazolium-based ionic liquid-reduced graphene oxide (mimG) via a nucleophilic ring-opening mechanism.
• Assembly of mimG-GO laminate membranes using a vacuum-assisted strategy.
• Comprehensive characterization of membrane properties, including stability, structure, water permeance, and rejection of salts (Na2SO4) and dyes (DR 80, RB 5, MO).

Main Results:

• The mimG-GO laminate membrane exhibited significantly improved stability in aqueous environments compared to neat GO membranes.
• A mimG-GO membrane with 72.2 mg m⁻² deposition showed a 50% increase in water permeance (14.9 LMH bar⁻¹) and enhanced Na2SO4 rejection (77.4%) compared to GO membranes.
• High rejection rates for various anionic dyes were achieved, with up to 99.9% for Direct Red 80, demonstrating effective separation performance.
• A higher deposition loading (361.0 mg m⁻²) resulted in superior Na2SO4 rejection (92.1%) and dye rejection while maintaining a flux of 2.6 LMH bar⁻¹.

Conclusions:

• The novel mimG-GO laminate membrane offers remarkable stability and superior water purification performance, overcoming the limitations of traditional GO membranes.
• The cation-π interactions facilitated by ionic liquid functionalization contribute to enhanced membrane stability and efficient water transport.
• The precisely controlled nanofluidic channels and tunable pore sizes enable effective removal of salts and dyes, highlighting the potential for advanced water treatment applications.