Polyamide Separation Membrane with Quaternary Ammonium Coating
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Solution Overview
Problem
Separation membranes face a challenge in maintaining water permeability when exposed to raw liquids containing cationic substances, leading to decreased performance.
Innovation Solution
A separation membrane design featuring a polyamide separation functional layer supported by a porous substrate and coated with a polymer containing a quaternary ammonium cation, which prevents cationic substances from adhering to the membrane surface, thus minimizing water permeability loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polyamide separation membrane is used, then good separation performance is achieved, but water permeability decreases significantly when exposed to cationic substances in raw liquid
Solution Approach 1:
The patent applies preliminary anti-action by pre-coating the polyamide separation layer with a polymer containing quaternary ammonium cations before the membrane encounters cationic substances in raw liquid. This pre-applied positive charge creates electrostatic repulsion against cationic contaminants, preventing their adhesion to the membrane surface and thereby maintaining stable water permeability throughout operation.
Solution Approach 2:
The patent introduces a polymer coating containing quaternary ammonium cations as an intermediary layer between the polyamide separation layer and the raw liquid. This intermediary layer serves as a protective barrier that interacts with cationic substances through electrostatic repulsion, preventing direct contact between contaminants and the separation layer, thus maintaining both separation performance and water permeability.
2Reliability
If the membrane surface is modified to resist cationic substances, then water permeability is maintained, but the complexity of membrane structure increases
Solution Approach 1:
The patent employs composite materials by combining a polyamide separation layer with a polymer coating containing quaternary ammonium cations. This composite structure integrates the separation functionality of polyamide with the anti-fouling properties of the charged polymer, achieving both cationic substance resistance and maintained water permeability through material composition rather than structural complexity.
Solution Approach 2:
The patent applies parameter changes by modifying the surface charge characteristics of the membrane through the quaternary ammonium cation coating. This chemical parameter modification (introducing permanent positive charges) fundamentally changes the interaction between the membrane surface and cationic substances, providing resistance without requiring complex structural modifications to the base membrane.
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 effectively retains high water permeability even when exposed to cationic substances, ensuring sustained performance and efficiency in separation processes.
Implementation Method 1
a coating (40) covering the separation functional layer (30) and containing a polymer having a repeating unit represented by the following formula (1)... N+... The technique of the present disclosure makes it possible to provide a separation membrane whose water permeability is decreased little by contact with a raw liquid containing a cationic substance
Data Source
Figure 1
AI summary
A separation membrane (10) of the present disclosure includes: a separation functional layer (30) composed of a polyamide; and a coating (40) covering the separation functional layer (30) and containing a polymer having a repeating unit represented by the following formula (1). In the formula (1), N+ is a nitrogen atom constituting a quaternary ammonium cation, and R1 and R2 are each independently a substituent containing a carbon atom bonded to the nitrogen atom.