Composite Membranes with Crosslinked Polyamide Films
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Solution Overview
Problem
Existing filtration membranes used in water purification and desalination processes face significant challenges with fouling due to contaminants, leading to reduced flux and shortened service life, and existing anti-fouling coatings are not well-suited for large-scale manufacturing and can compromise water flux.
Innovation Solution
A composite membrane with an active layer comprising two chemically distinct polyamide films, where one film is crosslinked with the other at their interface, and includes a structure with a side chain ammonium salt, enhancing antifouling and antimicrobial properties while maintaining ultrathin thickness to prevent flux drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective coating layer is applied to the membrane surface to reduce fouling, then fouling resistance is improved, but water flux decreases due to the additional layer thickness
Solution Approach 1:
The patent applies a thin film protective coating layer on the membrane surface to provide fouling resistance while minimizing flux reduction. The coating is designed as an ultrathin layer that maintains membrane permeability while offering protective functionality against fouling.
Solution Approach 2:
The patent uses composite material structure combining the base membrane with a protective coating layer made from specific polymers (polyacrylonitrile, polyacrylic acid, or their copolymers). This composite structure integrates the mechanical strength of the support membrane with the fouling-resistant properties of the coating layer.
2Reliability
If additional protective coating layers are applied to mitigate fouling, then fouling resistance is improved, but the number of manufacturing steps increases
Solution Approach 1:
The patent combines the protective coating formation with the existing membrane manufacturing process by applying the coating layer during the same production line operations. This integration merges multiple functions (membrane formation and protective coating application) into a unified manufacturing process, reducing the number of separate steps.
Solution Approach 2:
The protective coating layer is applied in advance during the membrane manufacturing process, before the membrane is put into service. This preliminary action ensures the coating is already in place to prevent fouling from the start, eliminating the need for subsequent coating applications or pre-treatment steps.
3Reliability
If the protective coating layer thickness is increased to enhance fouling resistance, then fouling resistance is improved, but water flux decreases
Solution Approach 1:
The patent specifically employs an ultrathin protective coating layer that is sufficiently thin to maintain high water flux while providing adequate fouling resistance. The thin film design optimizes the balance between protective functionality and permeability, avoiding the flux reduction associated with thicker coatings.
Solution Approach 2:
The patent optimizes the thickness parameter of the protective coating layer to achieve the desired balance between fouling resistance and water flux. By controlling the coating thickness within a specific range, the patent maximizes fouling protection while minimizing the impact on water 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 composite membrane effectively reduces fouling and maintains high water flux by repelling organic and biofoulants, inhibiting biofilm growth, and is suitable for large-scale manufacturing without compromising membrane performance.
Implementation Method 1
The second polyamide film is crosslinked with the first polyamide film at an interface therewith
Implementation Method 2
The second polyamide film includes a structure having a side chain group including an ammonium salt
Data Source
AI summary
A polymeric membrane includes an active layer over a support, wherein the active layer includes at least two chemically distinct polyamide films. A first one of the films is in contact with the support, and a second one of the films is not in contact with the support. The second polyamide film is crosslinked with the first polyamide film at an interface therewith, and the second polyamide film includes a structure having a side chain group including an ammonium salt.