Free-standing graphene oxide membrane with tunable channels for efficient water pollution control

Area of Science:

• Materials Science
• Nanotechnology
• Environmental Science

Background:

• Graphene oxide (GO) membranes are promising for separation technologies.
• Controlling interlayer spacing is crucial for optimizing membrane performance.
• Existing methods for tuning GO membranes have limitations.

Purpose of the Study:

• To fabricate a graphene oxide (GO) membrane with tunable interlayer spacing.
• To investigate the effect of interlayer spacing on dye and heavy metal ion rejection.
• To explore the water diffusion mechanism within the GO membrane.

Main Methods:

• Fabrication of GO membrane via inter-layer modification and external treatment.
• Adsorption of Congo red (CR) dye onto GO nano-sheets.
• Cross-linking of GO interlayers using Ca²⁺ ions.
• Thermal reduction and hot-pressing for π-π stacking modification.
• Climbing image nudged elastic band (cNEB) method for diffusion studies.

Main Results:

• Achieved tunable interlayer spacing from 7.7 Å to 11.7 Å.
• Demonstrated high rejection rates for dyes (e.g., methylene blue 99.5%) and heavy metals (e.g., Cu²⁺ 98.6%, Cd²⁺ 99.1%) at 7.7 Å.
• Obtained a permeation flux of 17.1 L/m²·h·bar.
• Identified hydrogen bonding as a factor constraining water diffusion.

Conclusions:

• The developed GO membrane offers tunable selectivity for water purification.
• Reduced interlayer spacing enhances rejection of contaminants.
• The membrane exhibits a balance of high rejection and good water permeability.
• Understanding water diffusion mechanisms aids in designing advanced separation membranes.