Cross-linked PVDF Nanofiltration Membranes for Extreme pH
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Solution Overview
Problem
Membrane separation technologies face challenges in extreme conditions such as extreme pH and organic solvents, leading to poor performance and stability, particularly in nanofiltration applications, where current membranes are prone to fouling and require harsh chemical cleaning that can degrade the material.
Innovation Solution
Cross-linked poly(vinylidene difluoride) (PVDF) membranes are developed using a one-pot dehydrofluorination and para-xylenediamine cross-linking reaction, enhancing their stability and selectivity for use in nanofiltration under extreme pH and solvent conditions without the need for additional pyrolysis or coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nanofiltration membranes are used in extreme pH and solvent conditions, then membrane separation can be performed, but membrane stability and performance deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of PVDF through dehydrofluorination to create reactive vinylidene groups, then cross-linking with diamines to form stable C-N bonds. This chemical transformation changes the membrane's parameters from hydrophobic and chemically reactive to chemically stable and resistant to extreme pH and solvents, enabling reliable operation in previously incompatible conditions
Solution Approach 2:
The patent creates a composite cross-linked structure by combining PVDF polymer chains with diamine cross-linkers. The resulting cross-linked PVDF-diamine composite material integrates the mechanical properties of PVDF with the chemical stability of the cross-linked network, achieving both membrane separation functionality and resistance to extreme conditions
2Productivity
If membranes are used in extreme conditions, then separation performance can be maintained, but membrane material degrades
Solution Approach 1:
The cross-linking reaction fundamentally changes the chemical parameters of the membrane material by forming covalent bonds between polymer chains. This creates a three-dimensional network structure that maintains pore architecture and separation performance while resisting degradation from extreme pH, organic solvents, and thermal stress that would otherwise destroy the membrane composition
3Reliability
If cross-linking is applied to enhance membrane stability, then membrane performance in extreme conditions improves, but membrane material undergoes chemical modification
Solution Approach 1:
The patent deliberately introduces chemical complexity through controlled dehydrofluorination and cross-linking reactions. The transformation from linear PVDF chains to cross-linked PVDF-diamine networks increases structural complexity but creates a more stable three-dimensional architecture that maintains mechanical integrity and separation performance under extreme conditions
Solution Approach 2:
The cross-linked structure creates a composite material system where PVDF provides the base polymer matrix and diamine cross-linkers form the stabilizing network. This composite architecture combines the benefits of both components, achieving enhanced stability while maintaining the fundamental membrane separation function
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 cross-linked PVDF membranes demonstrate improved retention and permeance in both acidic and caustic conditions, maintaining separation performance and stability in harsh environments, allowing for effective filtration of small compounds from alkaline or acidic solutions and organic solvents, thus extending their applicability in industries like mining and pharmaceuticals.
Implementation Method 1
a one-pot dehydrofluorination and para-xylenediamine cross-linking reaction
Implementation Method 2
cross-linked poly(vinylidene difluoride) (PVDF) membranes are developed using a one-pot dehydrofluorination and para-xylenediamine cross-linking reaction
Implementation Method 3
Nanofiltration (NF) in particular is useful for the purification of various streams (e.g. from diary or food industry) because of its ability to separate small molecular weight solutes (MW 200-1000 Da) from their solvent
Implementation Method 4
Selectivity is based on differences in size, charge, and/or affinity between the components and the membrane
Data Source
AI summary
The invention relates to the use of an uncoated cross-linked non-pyrolysed selective vinyl based halopolymer-membrane with a mwco of between 100 and 1000 Da, in the filtration of compounds from liquids comprising organic solvents and/or from liquids with a pH below 2 or above 12.