Gradient Pore Porous Membrane for Depth Filtration
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Solution Overview
Problem
Porous membranes used in depth filtration face challenges with low mechanical strength due to sparse support layer structures, leading to durability issues under repeated pressure applications and filtration-reverse flow washing cycles.
Innovation Solution
A porous membrane with a specific layered structure, including a first layer, a central layer, and a third layer, where the average trunk size of the third layer is larger than the second layer, and the number of pores and pore diameters are strategically distributed to enhance mechanical strength and permeability, using polysulfone-based polymers and controlled non-solvent vapor during phase separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the porous membrane uses a sparse support layer structure for depth filtration, then permeability is improved, but mechanical strength deteriorates
Solution Approach 1:
The membrane employs a gradient pore structure where the support layer has larger pores for high permeability and mechanical strength, while the separation layer has smaller pores for filtration. This local differentiation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
The membrane is constructed as a composite structure combining a support layer and a separation layer with different pore characteristics. The support layer provides mechanical strength and permeability, while the separation layer provides filtration capability, creating a synergistic composite material system.
2Ease of operation
If the porous membrane undergoes repeated filtration-reverse flow washing cycles, then cleaning efficiency is improved, but durability deteriorates
Solution Approach 1:
The gradient pore structure creates a transition zone that distributes mechanical stress from reverse flow washing across the membrane thickness. The larger pores in the support layer and smaller pores in the separation layer work together to reduce stress concentration, improving fatigue resistance while maintaining cleaning efficiency.
3Speed
If the pore diameters are increased for high permeability, then filtration speed is improved, but mechanical strength deteriorates
Solution Approach 1:
The membrane is segmented into two functional layers: the support layer with larger pores that provide mechanical strength and high permeability, and the separation layer with smaller pores that provide filtration. This segmentation allows the system to achieve both high filtration speed and adequate mechanical strength.
Solution Approach 2:
Different pore diameters are assigned to different regions of the membrane. The support layer has larger pores optimized for permeability and strength, while the separation layer has smaller pores optimized for filtration, creating local quality variations that satisfy multiple requirements simultaneously.
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 maintains high permeability over time, facilitates easy cleaning through backwashing, and provides long-lasting durability against fatigue, ensuring effective filtration and cleaning efficiency.
Implementation Method 1
a membrane that can perform so-called depth filtration is developed, in which pore diameters on a surface of the porous membrane are larger than the size of substance to be removed, and a minimum pore diameter layer is present either on the other surface or in a membrane thickness portion, and impurities are captured inside the membrane
Implementation Method 2
As a method for cleaning such substance accumulated inside a membrane, reverse flow washing is effective, which causes cleaning liquid, such as water, or clear liquid obtained by filtration to flow in a reverse direction to filtration
Data Source
AI summary
When the porous membrane, which has two surfaces of a surface A and a surface C, is equally divided in the thickness direction of the porous membrane into three layers of a first layer including the surface A, a second layer that is a central layer in the thickness direction, and a third layer including the surface C, an average trunk size of the third layer is larger than an average trunk size of the second layer, and when a continuous layer from the surface A having a thickness of 10 μm in the first layer is a first layer component, a continuous layer component having a thickness of 10 μm and an average trunk size smaller than an average trunk size of the first layer component is present in the first layer, the second layer, and the third layer other than the first layer component.