Composite Separation Membrane Chlorine Resistance
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Solution Overview
Problem
Conventional nanofiltration and reverse osmosis membranes with polyamide-type composite separation membranes have low resistance to chlorine, making them unsuitable for treating water containing sodium hypochlorite, and the manufacturing process for hollow fiber membranes is complex, while membranes with sulfonated polyarylene ether (SPAE) offer high chlorine resistance but face challenges with solvent solubility and adhesion to porous support membranes.
Innovation Solution
A composite separation membrane is developed with a sulfonated polyarylene ether copolymer as the separation layer on a porous support membrane made of polyphenylene ether, using specific solvents like dimethyl sulfoxide and N-methyl-2-pyrrolidone to ensure good adhesion and high mechanical strength, allowing for effective chlorine resistance and long-term water permeation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyamide-type composite separation membrane is used, then separation property and water permeation property are improved, but resistance to chlorine deteriorates
Solution Approach 1:
The patent uses a composite structure consisting of a porous support membrane and a separation layer formed by interfacial polymerization. The support membrane provides mechanical strength and chlorine resistance, while the thin separation layer provides high separation performance. This composite approach allows both good separation property and chlorine resistance to be achieved simultaneously.
Solution Approach 2:
The separation layer is formed as a thin film only on the surface of the support membrane through interfacial polymerization, concentrating the separation function in a localized region. This allows the bulk support membrane to maintain its chlorine resistance while the surface layer provides high separation performance.
2Object-affected harmful factors
If sulfonated polyarylene ether (SPAE) is used for separation layer, then resistance to chlorine is improved, but adhesion to porous support membrane deteriorates
Solution Approach 1:
The patent uses a porous support membrane with specific surface properties as an intermediary between the SPAE separation layer and the substrate. The support membrane's surface characteristics facilitate good adhesion of the SPAE layer while maintaining the layer's chlorine resistance properties.
Solution Approach 2:
The patent optimizes parameters such as the chemical composition of the support membrane, the concentration of SPAE in the coating solution, and drying conditions to achieve both good adhesion and chlorine resistance. By adjusting these parameters, the adhesion problem is resolved without compromising the chlorine resistance of the SPAE layer.
3Productivity
If thin film separation layer is formed to improve water permeation, then water permeation property is improved, but mechanical strength deteriorates
Solution Approach 1:
The membrane is segmented into two functional parts: a thin separation layer for high water permeation and a thicker support membrane for mechanical strength. This segmentation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
The composite structure combines a thin separation layer with a mechanically strong support membrane, allowing the thin layer to provide high water permeation while the support membrane provides the necessary mechanical strength.
4Reliability
If interfacial polymerization method is used, then separation layer formation is improved, but manufacturing complexity deteriorates
Solution Approach 1:
The patent combines the support membrane preparation and separation layer formation into an integrated process. The support membrane is prepared first, and then the separation layer is formed directly on its surface through interfacial polymerization, merging two steps into a coordinated manufacturing process.
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 maintains excellent separation and water permeation properties, resistance to chlorine and alkali, and exhibits a long lifespan, overcoming the limitations of previous technologies.
Implementation Method 1
thin film of cross-linked polyamide is formed on the surface of a porous support membrane by means of interfacial polymerization
Implementation Method 2
A nanofiltration membrane and a reverse osmosis membrane have such a filmy structure that a pore size of membrane thereof is in an order of from nanometers to angstroms
Implementation Method 3
a polymer which constitutes the separation layer has been demanded to be excellent in the resistance to chemicals or, particularly, in the resistance to chlorine and alkali
Data Source
AI summary
The present invention provides a composite separation membrane having a separation layer formed of SPAE on the surface of a porous support membrane wherein the porous support membrane and a coat of SPAE are firmly adhered with each other so that separation property and water permeation property continue for a long period. The present invention is a composite separation membrane having a separation layer on the surface of a porous support membrane, characterized in that said porous support membrane contains 50% by mass or more of polyphenylene ether, and that said separation layer is formed of a sulfonated polyarylene ether copolymer constituted from a repeating structure of a specific hydrophobic segment and a specific hydrophilic segment. The composite separation membrane of the present invention is suitable as a liquid treating membrane such as a nanofiltration membrane and a reverse osmosis membrane.