Chlorine-Resistant Polyelectrolyte Multilayer Membranes
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Solution Overview
Problem
Current desalination membranes, particularly polyamide-based thin film composite membranes, are not tolerant to chlorine, leading to degradation and requiring additional processing steps to prevent fouling, which increases operating costs and reduces membrane lifespan.
Innovation Solution
Development of a chlorine-resistant polyelectrolyte multilayer membrane comprising a water-permeable charged substrate with deposited polyelectrolyte bilayers, specifically using sulfonated polysulfone and cationic polyelectrolyte materials, which are cross-linked to enhance structural integrity and ion rejection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyamide-based thin film composite membranes are used for desalination, then ion rejection performance is improved, but chlorine tolerance deteriorates leading to membrane degradation
Solution Approach 1:
The patent employs a composite membrane structure consisting of a polyamide active layer deposited on a porous polysulfone support layer. This composite design allows the polyamide layer to provide high ion rejection performance while the polysulfone support layer provides chlorine resistance and structural stability, thus resolving the contradiction between ion rejection performance and chlorine tolerance
Solution Approach 2:
The invention applies different material properties to different layers of the membrane: the thin polyamide layer is optimized for ion rejection with heavily cross-linked structure, while the thicker polysulfone support layer is optimized for mechanical strength and chlorine resistance. This local differentiation of material qualities allows each layer to perform its specific function without compromising the other
2Reliability
If chlorine is added to feed water to prevent biological fouling, then fouling resistance is improved, but membrane lifespan deteriorates due to chlorine exposure
Solution Approach 1:
The polysulfone support layer in the composite membrane provides inherent resistance to chlorine degradation, allowing the membrane to withstand chlorinated feed water without compromising structural integrity. This enables the system to maintain fouling resistance through chlorination while preserving membrane lifespan
Solution Approach 2:
The robust polysulfone support layer acts as a protective cushion for the delicate polyamide active layer, absorbing the harmful effects of chlorine exposure before they can reach and degrade the polyamide bonds, thus extending membrane lifespan in chlorinated water systems
3Reliability
If additional processing steps are implemented to de-chlorinate and re-chlorinate water, then membrane protection is improved, but operating costs increase
Solution Approach 1:
The membrane's own polysulfone support layer provides the protective function against chlorine degradation, eliminating the need for external de-chlorination and re-chlorination processing steps. The membrane protects itself through its inherent material properties, thereby reducing operating costs while maintaining membrane protection
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 membranes demonstrate improved resistance to chlorine degradation, increased ion rejection, and reduced operating costs by eliminating the need for additional processing steps, while maintaining high water flux and purity in water purification applications.
Implementation Method 1
a plurality of polyelectrolyte bilayers deposited on at least one side of the substrate, each polyelectrolyte bilayer comprising a layer of a cationic polyelectrolyte material and a layer of an anionic polyelectrolyte material
Implementation Method 2
increased ion rejection performance
Data Source
AI summary
The present invention relates to chlorine resistant polyelectrolyte multilayer membranes which can be used as reverse osmosis, forward osmosis or nanofiltration membranes for applications such as desalination and water purification and methods of making membranes of this type.