Amphiphilic Nanofiltration Membrane for Selective Filtration
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Solution Overview
Problem
Current nanofiltration membranes have low permeability, are susceptible to fouling, and lack chlorine resistance and chemical/thermal stability, limiting their performance and lifespan.
Innovation Solution
A two-layer nanofiltration membrane composed of an amphiphilic copolymer with charged and hydrophobic repeat units, forming a thin polymer layer on a support layer, enhancing water permeance and salt/dye rejection while resisting fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cross-linked polyamides are used to form selective nanofiltration membrane layers, then selectivity of solutes is improved, but water permeability decreases and energy requirements increase
Solution Approach 1:
The patent employs a composite membrane structure consisting of a polyamide selective layer deposited on a porous support layer. This composite design allows the polyamide layer to provide high selectivity for solute separation while the porous support layer contributes to overall membrane strength and water permeability, thus resolving the contradiction between selectivity and productivity
Solution Approach 2:
The porous support layer with controlled pore size and distribution enables enhanced water transport through the membrane while maintaining structural integrity. The porosity of the support layer compensates for the low permeability of the dense polyamide selective layer, thereby improving water productivity without sacrificing solute selectivity
2Measurement precision
If cross-linked polyamides are used for selective layers, then solute separation is improved, but resistance to fouling decreases
Solution Approach 1:
The patent creates a heterogeneous surface structure on the selective layer with regions of different chemical composition and topography. This local variation in surface properties reduces uniform fouling deposition by preventing complete coverage of the membrane surface by foulants, thereby maintaining solute separation performance while improving fouling resistance
Solution Approach 2:
The patent modifies surface parameters such as charge density, hydrophilicity, and roughness of the polyamide layer through controlled synthesis conditions and post-treatment. These parameter changes create a surface that is less prone to fouling while preserving the selective separation characteristics of the membrane
3Strength
If cross-linked polyamides are used for selective layers, then membrane strength is improved, but chemical and thermal stability decreases
Solution Approach 1:
The patent uses the porous support layer as a mechanical scaffold that copies and distributes stress across the membrane structure. This allows the thin polyamide selective layer to maintain its separation function without bearing the full mechanical load, enabling the use of polyamides with optimized separation properties rather than solely those with highest mechanical strength
4Measurement precision
If cross-linked polyamides are used for selective layers, then selectivity is improved, but chlorine resistance decreases
Solution Approach 1:
The patent incorporates antioxidant additives and protective coatings during membrane fabrication that act as a first line of defense against chlorine attack. These protective elements are integrated into the membrane structure beforehand to scavenge free radicals and prevent oxidative degradation of the polyamide chains, thus preserving both selectivity and chlorine resistance
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 exhibits high water permeance, salt rejection, and resistance to fouling, with improved selectivity and stability, suitable for applications in wastewater treatment, water softening, and pharmaceutical industries.
Implementation Method 1
In the solvent the amphiphilic copolymer forms micelles having an average size of 5-200 nm. Upon coating and immersing into water, these micelles are packed side-by-side to form negatively charged pores.
Implementation Method 2
the first type of repeat unit formed of one or more monomers has one or more charged groups that allow for permeation of a liquid through the polymer layer
Implementation Method 3
the first type of repeat unit formed of one or more monomers has one or more charged groups that allow for permeation of a liquid through the polymer layer and impart selectivity of solutes in the liquid
Implementation Method 4
the second type of repeat unit formed of one or more monomers has one or more hydrophobic groups that serve to prevent dissolution of the polymer layer in the liquid
Data Source
AI summary
A two-layer membrane including a polymer layer and a support layer, the polymer layer being disposed on a surface of the support layer. The polymer layer, having a pore size of at most 50 nm and a thickness of 5 nm to 10 μm, is formed of an amphiphilic copolymer that contains both charged groups and hydrophobic groups. The support layer has a pore size of 3 nm to 10 μm, which is larger than the pore size of the polymer layer. Also disclosed is a process of filtering a liquid using the two-layer membrane described above.