Conductive Polymer CNT Composite Nanofiltration Membrane
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Solution Overview
Problem
Nanofiltration (NF) membranes face a trade-off between permeability and selectivity, and exhibit low rejection rates for monovalent ions, limiting their effectiveness in water treatment.
Innovation Solution
A conductive polymer/CNT composite NF membrane is prepared by polymerizing conductive polymers into CNT membranes and in-situ cross-linking with glutaraldehyde under acidic conditions, with electrical assistance to enhance surface charge density and improve rejection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If membrane pore size is reduced to improve rejection performance, then selectivity is improved, but permeability declines
Solution Approach 1:
The patent changes the surface charge density parameter of the membrane through surface modification with conductive polymers and carbon nanotubes. This allows the membrane to enhance electrostatic interaction with ions without reducing pore size, thereby improving rejection performance while maintaining high permeability.
Solution Approach 2:
The patent creates a composite membrane structure by integrating conductive polymers (such as polyaniline, polypyrrole, or polythiophene) and carbon nanotubes onto the membrane surface. This composite approach enhances surface charge density and electrostatic interaction capabilities, enabling improved ion rejection without compromising water permeability.
2Manufacturing precision
If surface charge density is increased to enhance electrostatic interaction, then rejection performance is improved, but the thin separation layer and limited surface area restrict further improvement
Solution Approach 1:
The patent utilizes porous conductive polymer structures and carbon nanotube networks that provide high surface area-to-volume ratios. These porous materials enable significant increases in effective surface charge density without requiring a larger membrane area, thus overcoming the limitation of limited surface area in thin-film membranes.
Solution Approach 2:
The patent concentrates charge-enhancing materials (conductive polymers and carbon nanotubes) specifically at the membrane separation layer where they are most needed for ion rejection. This localized modification maximizes the effect on rejection performance while minimizing impact on overall membrane structure and permeability.
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 method achieves improved ion rejection and permeability, alleviating the permeability-selectivity trade-off and enhancing the removal of small molecular organic pollutants, while maintaining high permeability.
Implementation Method 1
polymerizing conductive polymer into a CNT membrane
Implementation Method 2
in-situ cross-linking with glutaraldehyde (GA) under acidic condition
Implementation Method 3
enhancing electrostatic interaction between the membrane and charged target species
Implementation Method 4
nanofiltration (NF) membranes are still subject to some limitations... NF membranes exhibit low rejection rates for monovalent salt ions
Data Source
AI summary
A method for preparation of conductive polymer/carbon nanotube (CNT) composite nanofiltration (NF) membrane and the use thereof. This conductive polymer/CNT composite NF membrane is obtained by polymerizing conductive polymer into a CNT membrane and then in-situ cross-linking with glutaraldehyde under acidic condition. The synthetic method for the conductive polymer/CNT composite NF membrane is simple and has no need of expensive equipment. The prepared membrane has controllable membrane structure and possesses superior electrical conductivity and electrochemical stability. The membrane can couple with electrochemistry for electrically assisted filtration. With the electrical assistance, the membrane can achieve improved ion rejection performance while retaining high permeability by enhancement of membrane surface charge density, which alleviates the permeability-selectivity trade-off. Furthermore, the electrically assisted NF membrane filtration can also enhance the removal for small molecular organic pollutants.