Composite Semipermeable Membrane for Oxidation-Resistant Salt Separation
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Solution Overview
Problem
Conventional composite semipermeable membranes with a crosslinked aromatic polyamide separation functional layer suffer from limitations in separation performance and are prone to decomposition by oxidants, leading to irreversible impairment of their performance.
Innovation Solution
A composite semipermeable membrane is developed with a support membrane and a separation functional layer containing a crosslinked aromatic polyamide at 50 mass% or higher, incorporating sulfo groups in the range of 7.0×10 -5< to 5.0×10 -2< g/m 2< , and a structure represented by a specific formula, with a C/D ratio of 3-10, enhancing oxidation resistance and separation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crosslinked aromatic polyamide separation functional layer is used, then separation performance and permeation performance are achieved, but the membrane is decomposed by oxidants and separation performance is irreversibly impaired
Solution Approach 1:
The patent modifies the chemical structure of the aromatic polyamide by introducing specific substituents (sulfonic acid groups, amino groups, or carboxylic acid groups) at controlled ratios. This changes the chemical parameters of the membrane material to enhance oxidation resistance while preserving separation performance
Solution Approach 2:
The patent creates a composite aromatic polyamide structure by combining the base polyamide with functional groups having different chemical properties (sulfonic acid, amino, or carboxylic acid groups). This composite structure provides both the mechanical strength needed for membrane integrity and chemical resistance to oxidants
2Reliability
If conventional crosslinked aromatic polyamide is used, then basic membrane function is achieved, but separation performance is limited
Solution Approach 1:
The patent introduces functional groups at specific locations within the polymer structure (as substituents on the aromatic rings) to create local areas with enhanced separation properties. The sulfonic acid groups provide negative charge for anion rejection, while amino and carboxylic acid groups provide positive charge for cation rejection, enabling tailored separation capabilities
Solution Approach 2:
The patent systematically varies the ratio of functional groups (sulfonic acid, amino, carboxylic acid) to optimize separation performance for different applications. By controlling the concentration and distribution of these groups, the membrane can be tuned for specific separation requirements while maintaining structural integrity
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 exhibits excellent salt-separating performance, permeation performance, and oxidation resistance, maintaining high performance even when exposed to oxidants like hypochlorous acid.
Implementation Method 1
a separation functional layer disposed on the porous support layer and including a crosslinked aromatic polyamide
Implementation Method 2
the separation functional layer contains sulfo groups in an amount of 7.0×10 -5< to 5.0×10 -2< g/m 2< and has a value of C/D of 3-10
Data Source
Figure 1(a)~1(c)
AI summary
The composite semi-permeable membrane according to the present invention is provided with: a support film including a base material and a porous support layer; and a separation function layer containing a crosslinked aromatic polyamide as a main component. The sulfo group content of the separation function layer is 7.0×10-5-5.0×10-2g/m2, and the separation function layer has a structure represented by formula 1.