Asymmetric Polyamide Membrane for Water Permeation and Oxidant Resistance
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Solution Overview
Problem
Existing composite semipermeable membranes face challenges in achieving high water permeation and solute removal performance while maintaining durability against oxidizing agents and organic matter, particularly hypochlorous acid and alcohol, with low neutral molecule removal rates and permeate flow rates.
Innovation Solution
A composite semipermeable membrane with a porous support membrane coated with a separating functional polyamide layer formed by polycondensation of polyfunctional aromatic amines and polyfunctional acid halides, featuring carboxy, amino, phenolic hydroxyl, and azo groups, where the ratio of amino groups on the feed water contact surface is 0.5 or less and on the permeate-side surface is between 0.5 and 1, and the azo groups are more concentrated on the feed water side for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a composite semipermeable membrane with cross-linked polyamide active layer is used to achieve high permeability and selective separation, then water permeation performance is improved, but durability against oxidizing agents and organic matter deteriorates
Solution Approach 1:
The patent applies local quality by creating an asymmetric distribution of functional groups within the active layer. The feed water contact surface is engineered with specific functional group compositions (different from the permeate-side surface) to provide localized resistance against oxidizing agents and organic matter, while maintaining high water permeation performance throughout the membrane structure.
Solution Approach 2:
The patent employs composite materials by incorporating multiple functional groups (carboxy, amino, phenolic hydroxyl, and azo groups) within the polyamide active layer. This composite functional structure provides both high water permeability and enhanced durability against chemical degradation from oxidizing agents and organic matter.
2Quantity of substance
If the membrane structure is optimized for high ion removal rate, then solute removal performance is improved, but neutral molecule removal rate and permeate flow rate deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratios and distributions of different functional groups (carboxy, amino, phenolic hydroxyl, and azo groups) within the active layer. By adjusting these chemical parameters and their spatial distribution, the membrane achieves simultaneous high ion removal, neutral molecule removal, and permeate flow rate performance.
Solution Approach 2:
The patent uses local quality by creating different functional group compositions at different locations within the active layer. The feed water contact surface has a specific functional group distribution optimized for initial separation, while the permeate-side surface has a different distribution optimized for maintaining flow rates and removing neutral molecules, thereby achieving balanced overall performance.
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 achieves high water permeation and solute removal performance with improved durability against oxidizing agents and organic matter, maintaining high permeate flow rates and solute removal efficiency.
Implementation Method 1
a composite semipermeable membrane comprising a porous support membrane on which a separating functional polyamide layer is formed
Implementation Method 2
high water permeation performance and high solute removal performance
Implementation Method 3
a separating functional polyamide layer resulting from the polycondensation reaction of polyfunctional aromatic amines with polyfunctional acid halides
Implementation Method 4
high solvent resistance and a method for producing same... improved durability against oxidizing agents and organic matter
Data Source
AI summary
A composite semipermeable membrane comprising a porous support membrane on which a separating functional polyamide layer resulting from the polycondensation reaction of polyfunctional aromatic amines with polyfunctional acid halides is formed, wherein the separating functional polyamide layer has carboxy groups, amino groups, phenolic hydroxyl groups, and azo groups, wherein XA, the ratio of the amino groups (molar equivalent of the amino groups/(molar equivalent of the azo groups+molar equivalent of the phenolic hydroxyl groups+molar equivalent of the amino groups)) on a feed water contact surface of the separating functional polyamide layer (an A surface), is in the range 0.5 or less, and XB, the ratio of the amino groups (molar equivalent of the amino groups/(molar equivalent of the azo groups+molar equivalent of the phenolic hydroxyl groups+molar equivalent of the amino groups)) on a permeate-side surface of the separating functional polyamide layer (a B surface), i.e., the opposite side to the A surface, is in the range of 0.5 to 1. The present invention provides a composite semipermeable membrane that achieves a balance between high solute removal properties and a high permeate flow rate and has high organic-solvent resistance, and a method for producing same.