CNT-Polymer Membrane Phase Inversion Desalination
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Solution Overview
Problem
Current methods for preparing carbon nanotube membranes are complex, limited to small areas, and not scalable for industrial applications, while existing membranes face challenges with membrane fouling, high energy requirements, and limited salt retention in reverse osmosis processes.
Innovation Solution
Development of asymmetric composite membranes using a polymeric matrix with randomly oriented carbon nanotubes, specifically cellulose acetate and multi-walled carbon nanotubes, formed through a phase inversion technique, which includes functionalization of carbon nanotubes and the addition of pore-forming additives to enhance permeability and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If current methods for preparing carbon nanotube membranes are used, then membrane performance is achieved, but the preparation process is complex and limited to small areas with poor scalability
Solution Approach 1:
The invention changes the preparation method from complex multi-step processes to a simple one-step phase inversion technique by modifying the chemical parameters of the membrane formation process, enabling large-area production while maintaining membrane performance
Solution Approach 2:
The invention utilizes phase inversion transition to form the membrane structure in a single step, where the polymer solution undergoes phase separation upon contact with coagulation bath, enabling scalable production of large-area membranes with controlled porosity
2Reliability
If reverse osmosis processes are used for desalination, then salt retention is achieved, but high energy requirements and membrane fouling occur
Solution Approach 1:
The invention employs carbon nanotubes with precisely controlled porous structures that provide size-based ion exclusion, enabling salt retention through physical sieving rather than high-pressure forcing, thereby reducing energy requirements while maintaining desalination effectiveness
Solution Approach 2:
The invention creates a composite membrane structure combining carbon nanotubes with polymer matrices, where the CNTs provide selective ion rejection channels and the polymer provides structural support, achieving both salt retention and reduced fouling through the synergistic combination of materials
3Productivity
If carbon nanotubes are added to polymer matrices, then water permeation is enhanced, but salt retention may be compromised
Solution Approach 1:
The invention applies local quality by creating regions with different pore sizes and properties within the membrane - carbon nanotube channels provide high-permeability pathways while the polymer matrix regions provide salt rejection, achieving both high water flux and effective salt retention through spatial differentiation of functions
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 solution achieves high water permeation rates with improved salt retention and reduced fouling, maintaining performance comparable to existing membranes while being simpler and more economical to produce, suitable for industrial-scale desalination processes.
Implementation Method 1
Studies have demonstrated water conduction through the hydrophobic channel of a carbon nanotube, including osmotic water transport. Molecular dynamics simulations have also revealed that water ordering near the smooth hydrophobic walls of CNTs helps to facilitate enhanced, frictionless water transport.
Implementation Method 2
Studies have demonstrated water conduction through the hydrophobic channel of a carbon nanotube, including osmotic water transport.
Implementation Method 3
The polymer-CNT composite membranes are prepared by a simple one-step phase-inversion process
Implementation Method 4
Oxidation is the most common method for functionalizing CNTs. Using this process, carbons on defected sites of the crystalline structure of CNTs, or on the sites of misaligned π bonds, or usually on both, are oxidized to install COOH hydrophilic groups.
Implementation Method 5
Both charge and size effects can impact exclusion. For example, when nanotubes are charged with positive or negative charges, charged particles in the liquid can be repulsed from or attracted to the nanotubes.
Implementation Method 6
Both charge and size effects can impact exclusion. For example, when nanotubes are charged with positive or negative charges, charged particles in the liquid can be repulsed from or attracted to the nanotubes.
Data Source
AI summary
This invention relates to an asymmetric composite membrane containing a polymeric matrix and carbon nanotubes within a single membrane layer, where the carbon nanotubes are randomly oriented within the polymeric matrix and the composite membrane is formed by phase inversion. This invention also relates to a method for producing the composite membrane which includes: coating a surface with a film of a polymer solution containing a polymeric matrix and carbon nanotubes dissolved in at least one solvent; immersing the coated surface in a non-solvent to affect solvent/non-solvent demixing resulting in phase inversion to form a carbon nanotube-containing membrane; and optionally, removing the carbon nanotube-containing membrane from the surface. The invention also relates to a desalination method using the composite membrane.