Crosslinked Ion-Exchange Membrane for Electrodialysis
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Solution Overview
Problem
Existing ion-exchange membranes used in electrodialysis are not satisfactory in all respects, particularly in terms of sheet resistance and mechanical strength, which affects the efficiency and cost of water desalination processes.
Innovation Solution
A polymer with a specific structure, comprising alternating or random arrangements of repeating units with grafted anionic groups and ungrafted maleic anhydride units, is crosslinked to form a membrane with improved properties, including lower sheet resistance and enhanced mechanical strength, achieved through the use of a grafting reagent and crosslinking reagent like diamine or triamine, allowing for better film-forming ability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing ion-exchange membranes are used in electrodialysis, then the basic desalination function is achieved, but the sheet resistance is high and mechanical strength is insufficient
Solution Approach 1:
The patent uses a composite polymer structure combining styrene-maleic anhydride units with grafted amino groups and crosslinked diamine structures. This composite approach integrates the ion-exchange functionality of maleic anhydride groups with the mechanical strength provided by the crosslinked network, resolving the contradiction between functional performance and mechanical strength.
Solution Approach 2:
The patent modifies the polymer parameters by controlling the molar ratios of different repeating units (m:n:o where m:(n+o) is 60:40 to 85:15) and the degree of crosslinking. By adjusting these parameters, the membrane achieves optimal balance between ion-exchange capacity (sheet resistance) and mechanical strength.
2Productivity
If existing ion-exchange membranes are used in electrodialysis, then the basic desalination function is achieved, but the sheet resistance is high affecting efficiency
Solution Approach 1:
The patent optimizes the polymer composition parameters, specifically the molar ratio of ion-exchange groups to total units (m:(n+o) from 60:40 to 85:15), to achieve lower sheet resistance. The high density of ion-exchange groups (A−) per unit length reduces electrical resistance, thereby improving desalination efficiency.
3Duration of action of stationary object
If crosslinking is performed to enhance mechanical strength, then the membrane durability is improved, but the film-forming ability must be maintained
Solution Approach 1:
The patent incorporates crosslinkable maleic anhydride groups into the polymer chain before membrane fabrication. These pre-installed functional groups enable subsequent crosslinking treatment to enhance durability without affecting the initial film-forming ability, as the crosslinking occurs after the membrane structure is already formed.
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 resulting ion-exchange membranes exhibit reduced sheet resistance, enabling efficient ionic dialysance at lower operating voltages, reduced energy loss, and increased mechanical strength, leading to improved desalination rates and operational costs.
Implementation Method 1
the polymer is crosslinked to form a membrane with improved properties, including lower sheet resistance and enhanced mechanical strength, achieved through the use of a grafting reagent and crosslinking reagent like diamine or triamine
Implementation Method 2
Cations can only penetrate through a cation-exchange membrane and anions can only penetrate through an anion-exchange membrane. Electrodialysis (ED) utilizes this property to separate selected cations and anions from each other in water through an ion-exchange membrane
Implementation Method 3
The resulting ion-exchange membranes exhibit reduced sheet resistance, enabling efficient ionic dialysance at lower operating voltages
Data Source
AI summary
The present disclosure provides a polymer, including a first repeating unit represented by formula (I), a second repeating unit represented by formula (II), and a third repeating unit represented by formula (III). The first repeating unit, the second repeating unit, and the third repeating unit are arranged in an alternating fashion, in a random fashion, or in discrete blocks. The molar ratio of the first repeating unit, the second repeating unit and the third repeating unit is m:n:o, and m:(n+o) is from 60:40 to 85:15. The definitions of a, R1, R2, A−, and R+ are as defined in the specification.