Sulfonated Poly(arylene Ether) Membranes for Monovalent Ion Rejection
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Solution Overview
Problem
Existing desalination membranes, particularly those made from anionic sulfonated poly(arylene ether) materials, struggle to effectively reject monovalent ions in the presence of polyvalent cations, which is a critical issue in seawater desalination where polyvalent salts are prevalent.
Innovation Solution
The development of sulfonated poly(arylene ether) polymers with specific structural features, such as linear sulfonated copolymers and crosslinked networks, which are designed to improve salt rejection and water permeability, even in the presence of polyvalent cations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sulfonated poly(arylene ether) membranes are used for water desalination, then water permeability is maintained at high levels, but monovalent ion rejection deteriorates in the presence of polyvalent cations
Solution Approach 1:
The patent introduces specific structural features at local positions within the polymer chain, namely sulfonate groups at defined locations and crosslinking at specific sites. This localized modification creates regions of high ion rejection capability while preserving overall water permeability, directly addressing the contradiction between maintaining water flux and improving monovalent ion rejection in mixed salt conditions.
Solution Approach 2:
The patent creates a composite structure by combining sulfonated poly(arylene ether) chains with crosslinking agents to form a crosslinked network. This composite approach integrates the high water permeability of the poly(arylene ether) backbone with the ion rejection capability of the crosslinked sulfonate groups, enabling simultaneous achievement of water flux and monovalent ion rejection performance.
2Strength
If crosslinking is introduced to improve membrane structure, then mechanical strength increases, but water permeability may be reduced
Solution Approach 1:
The patent optimizes the crosslinking density and sulfonate group concentration as key parameters to achieve the desired balance. By controlling the extent of crosslinking and the degree of sulfonation, the membrane structure is tuned to provide sufficient mechanical strength while maintaining adequate water permeability, resolving the contradiction between strength and productivity.
Solution Approach 2:
The crosslinking is performed at specific locations within the polymer structure, creating a three-dimensional network that provides mechanical reinforcement without completely blocking water transport pathways. This localized crosslinking approach maintains water permeability while significantly improving membrane strength and stability.
3Reliability
If sulfonate group concentration is increased to improve ion rejection, then monovalent ion rejection increases, but water permeability decreases
Solution Approach 1:
The patent optimizes the sulfonate group concentration and crosslinking density as critical parameters to achieve the optimal balance between ion rejection and water flux. By carefully controlling these parameters, the membrane achieves high monovalent ion rejection capability while maintaining sufficient water permeability for productive desalination operation.
Solution Approach 2:
The patent creates a composite structure where sulfonate groups are distributed within a crosslinked poly(arylene ether) matrix. This composite architecture allows the sulfonate groups to provide ion rejection functionality while the crosslinked network structure maintains water transport pathways, resolving the contradiction between ion rejection capability and water flux.
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
These advanced membranes exhibit high rejection of monovalent ions (>90%) despite the presence of polyvalent cations, while also maintaining good water permeability, thus addressing the limitations of previous desalination technologies.
Implementation Method 1
Anionic sulfonated poly(arylene ether) membranes for water desalination have been shown to have high water permeability and good rejection of monovalent salts
Implementation Method 2
membranes made from such materials are typically not very good at rejecting monovalent ions... These advanced membranes exhibit high rejection of monovalent ions (>90%) despite the presence of polyvalent cations
Implementation Method 3
Membrane based desalination processes are more economical and energetically efficient than thermal methods for seawater desalination
Data Source
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AI summary
Described herein are water desalination membranes and methods of desalinating water. Sulfonated poly(arylene ether) polymers are also disclosed, including those comprising one or more sulfonate groups at various points along the polymer chain. The polymers may be used as at least a portion of a water desalination membrane. The polymers described herein are useful for preventing transport of aqueous ionic species (e.g., Na+ and Cl-) across a membrane made from the polymers while allowing water to pass. Chlorine-stable polymers are described, as well as polymers exhibiting good performance for rejecting monovalent cations in the presence of polyvalent cations.