Graphene Membrane Charge Tuning for Ion Selectivity
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Solution Overview
Problem
Graphene-based membranes face a challenge in achieving improved ionic rejection and ion selectivity while maintaining acceptable water flux performance, as reducing nanochannel size to enhance ionic rejection negatively impacts water flux.
Innovation Solution
A graphene-based membrane is developed with a stacked arrangement of layers defining nanochannels, where the surface electrical charge is varied to control size and ionic selectivity, allowing for enhanced ion rejection without compromising water flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If nanochannel size is reduced to enhance ionic rejection, then ionic rejection is improved, but water flux deteriorates
Solution Approach 1:
The patent changes the electrical charge parameter of the nanochannel surfaces through chemical functionalization (adding oxygen-containing groups, carboxylic acid groups, or other charged groups). This allows the membrane to achieve high ionic rejection through electrostatic repulsion without reducing nanochannel size, thereby maintaining high water flux. The charge density and sign can be tuned to optimize both ionic rejection and water permeability.
Solution Approach 2:
The patent creates composite graphene-based membranes by combining graphene layers with charged functional groups or coating the graphene surfaces with charged materials. This composite structure provides both the mechanical strength and nanochannel geometry of graphene and the ionic selectivity of charged surfaces, resolving the contradiction between ionic rejection and water flux.
2Manufacturing precision
If nanochannel size is reduced to achieve smaller cutoff size, then size selectivity is improved, but water flux deteriorates
Solution Approach 1:
The patent changes the surface charge parameter to achieve size and charge selectivity without reducing nanochannel dimensions. By introducing charged functional groups on the nanochannel surfaces, the membrane can selectively reject ions based on their charge and size through electrostatic interactions, maintaining both high size selectivity and water flux.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The membrane achieves improved ionic rejection and selectivity, making it suitable for desalination, nanofiltration, and electrodialysis applications while maintaining ultra-high water flux.
Implementation Method 1
Ionic rejection of the graphene-based membranes may be driven by geometric size exclusion
Implementation Method 2
varying an electrical charge on a surface of the layers of the graphene-based material defining the one or more nanochannels to control size selectivity and/or ionic selectivity
Data Source
AI summary
A method of preparing a graphene-based membrane is provided. The method may include providing a stacked arrangement of layers of a graphene-based material, wherein the layers of the graphene-based material define one or more nanochannels between neighboring layers, and varying an electrical charge on a surface of the layers of the graphene-based material defining the one or more nanochannels to control size selectivity and/or ionic selectivity of the graphene-based membrane. A graphene-based membrane and a method of separating ions from a fluid stream are also provided.