Composite Membrane Protrusions for Low-Pressure Water Permeability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing composite semipermeable membranes used for desalination, such as those containing crosslinked polyamide as a separation active layer, face challenges in achieving high water permeability during low-pressure operation.
Innovation Solution
A composite semipermeable membrane design featuring a support membrane with a separation functional layer having protrusions with specific geometric characteristics, such as a ratio of maximum width to root width greater than 1.3, an average number density of 10-20 protrusions/μm, and a thickness of 15 nm or more, enhances water permeability by optimizing the structure and density of the protrusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional composite semipermeable membranes with crosslinked polyamide are used, then separation performance is achieved, but water permeability during low-pressure operation is insufficient
Solution Approach 1:
The patent applies local quality by creating protrusions with specific geometric characteristics (Wa/Wb ratio > 1.3) in the separation functional layer. These localized structural features concentrate water flux through the protrusion regions while maintaining the overall separation integrity of the membrane. The asymmetric geometry of protrusions creates preferential flow paths that enhance water permeability without compromising salt rejection.
Solution Approach 2:
The patent introduces dimensional complexity by forming three-dimensional protrusions on the membrane surface. This transforms the traditionally two-dimensional flat membrane structure into a three-dimensional configuration with height, width, and root width dimensions. The protrusions create additional water transport pathways in the vertical dimension while maintaining the horizontal separation function, thereby improving water permeability without sacrificing separation performance.
2Reliability
If the separation functional layer has a dense structure for good salt rejection, then separation performance improves, but water permeability decreases
Solution Approach 1:
The patent segments the separation functional layer into distinct regions: protrusion areas and base membrane areas. The protrusions act as segmented water transport channels that are less dense, while the base membrane maintains the dense structure required for salt rejection. This segmentation allows different regions to perform different functions optimally - water transport through protrusions and salt barrier function through the base membrane.
Solution Approach 2:
The protrusions function as porous structures with controlled porosity and interconnected pore networks. The porous nature of protrusions provides water transport pathways while the specific geometric parameters (Wa/Wb ratio, height, root width) control the pore size distribution to maintain salt rejection. The porous structure enables water permeability while the geometric constraints ensure separation performance.
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 excellent water production performance even under low-pressure conditions, improving water permeability and maintaining stable membrane performance.
Implementation Method 1
as a reverse osmosis membrane and a nanofiltration membrane, a composite semipermeable membrane containing a crosslinked polyamide as a separation active layer has been proposed
Implementation Method 2
use of a membrane separation method as a process for energy and resource conservation has expanded
Data Source
AI summary
The present invention relates to a composite semipermeable membrane including: a support membrane; and a separation functional layer provided on the support membrane, in which the separation functional layer comprises a plurality of protrusions formed of a thin membrane, and at least a part of the plurality of protrusions has a ratio (Wa/Wb) of larger than 1.3 in cross sections at arbitrary ten positions each having a length of 2.0 μm in a membrane surface direction of the support membrane, provided that Wa is a maximum width of the protrusion and Wb is a root width of the protrusion.