Composite Membrane Projections for High-Pressure Stability
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Solution Overview
Problem
Existing composite semipermeable membranes used for seawater desalination face challenges in maintaining high salt removal performance and water permeability under high pressure, as excessive projection size leads to deformation and membrane structure deterioration.
Innovation Solution
A composite semipermeable membrane with a supporting membrane and a separation functional layer, where the average number density of projections is 10.0 pieces/µm or more and the average height is 100 nm or more, is developed, ensuring uniform projection size and stability under pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the projection size is increased to improve water permeability, then water permeability is improved, but salt removal performance deteriorates due to projection crushing under high pressure
Solution Approach 1:
The invention changes the geometric parameters of projections by specifying precise ranges for height (10-500 nm) and number density (10.0 pieces/μm or more). This parameter optimization allows projections to provide sufficient membrane area for high water permeability while maintaining uniform, crush-resistant dimensions that preserve salt removal performance under operating pressure.
Solution Approach 2:
The invention creates local quality variations in the separation functional layer by forming projections with specific dimensional characteristics. The projections provide localized increased surface area for water transport while their controlled size and distribution prevent localized stress concentration that would lead to crushing and performance degradation.
2Productivity
If the projection height is increased to increase substantial membrane area, then water permeability is improved, but manufacturing precision deteriorates due to uneven projection size
Solution Approach 1:
The invention optimizes the projection height parameter within a specific range (10-500 nm) that balances two competing requirements: sufficient height to increase substantial membrane area for water permeability, and limited height to maintain manufacturing precision and prevent projection crushing. This parameter window ensures uniform projection formation while achieving the desired permeability enhancement.
3Reliability
If the projection number density is increased to improve salt removal performance, then salt removal performance is improved, but water permeability deteriorates due to reduced projection height
Solution Approach 1:
The invention uses local quality variation through projections to simultaneously achieve high salt removal and water permeability. The projections create localized regions of increased surface area that enhance water transport pathways while their controlled dimensions and distribution maintain the necessary separation characteristics for salt rejection, resolving the trade-off between these two performance metrics.
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
This design achieves compatible high salt removal performance and water permeability, preventing projection deformation and maintaining stable membrane performance even under high pressure.
Implementation Method 1
impregnating the polymer solution in the substrate and thereafter bringing the polymer solution into contact with a coagulation bath, thereby forming a porous supporting layer in which 10 to 90% by weight thereof is impregnated in the substrate, by phase separation
Implementation Method 2
a composite semipermeable membrane obtained by coating a supporting membrane with a separation functional layer including a cross-linked polyamide obtained by polycondensation reaction of a multifunctional amine with a multifunctional acyl halide
Implementation Method 3
the composite semipermeable membrane obtained by the invention can be suitably used, for example, for desalination of seawater or brackish water
Data Source
Figure 1
AI summary
The present invention relates to a composite semipermeable membrane including: a supporting membrane having a substrate and a porous supporting layer; and a separation functional layer provided on the supporting membrane, in which, when any 10 cross sections of the composite semipermeable membrane, having a length of 2.0 µm in a membrane surface direction, are observed using an electron microscope, an average number density of projections on the separation functional layer, which have a height equivalent to or higher than 1/5 of a 10-point average surface roughness of the separation functional layer, is 10.0 pieces/µm or more, in each cross section, and an average height of the projections is 100 nm or more.