Membrane Defect Abatement Using PDMS Permeable Layer
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Solution Overview
Problem
Existing membrane structures with fine pores face challenges in achieving high permeance and selectivity due to defects, which affect their reproducibility, stability, and separation performance, especially in industrial-scale production.
Innovation Solution
A membrane structure comprising a substrate, a support layer, and a selective layer with a permeable layer on top, where the permeable layer is designed to reduce defect flow contributions and support spreading effects without significantly increasing flow resistance, using polydimethylsiloxane (PDMS) as a defect abatement layer to restore membrane performance to near intrinsic values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thin membranes with small pores are used to achieve high selectivity, then selectivity is improved, but mechanical strength deteriorates
Solution Approach 1:
The membrane is divided into multiple thin layers, each with specific pore sizes and functions. The support layer provides mechanical strength while the selective layer provides separation performance, resolving the contradiction between strength and selectivity through functional segmentation
Solution Approach 2:
The invention uses composite membrane structures combining different materials with complementary properties. The support layer uses materials optimized for mechanical strength while the selective layer uses materials optimized for separation, creating a composite system that achieves both strength and selectivity
2Productivity
If thin membranes are used to increase flux, then permeance is improved, but mechanical stability deteriorates
Solution Approach 1:
The membrane structure is segmented into a thick support layer for mechanical stability and a thin selective layer for high permeance. This segmentation allows each layer to optimize its thickness for its specific function, resolving the contradiction between permeance and stability
Solution Approach 2:
Different regions of the membrane have different thicknesses and properties. The support layer is thick and mechanically robust while the selective layer is thin and highly permeable, with each region optimized for its local function to achieve both high permeance and mechanical stability
3Ease of manufacture
If defects are present in the membrane, then manufacturing ease is improved, but separation performance deteriorates
Solution Approach 1:
The support layer acts as a cushioning layer that compensates for defects in the selective layer. By designing the support layer with appropriate properties, the system anticipates and mitigates the harmful effects of defects before they can significantly impact separation performance
Solution Approach 2:
The support layer serves as an intermediary between the feed side and the selective layer, providing a buffer that reduces the impact of defects on overall membrane performance. This intermediary layer allows easier manufacturing while maintaining 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 achieves high selectivity and permeance by reducing defect-related flow contributions, leading to improved gas separation performance and increased operational stability, with PDMS modification demonstrating significant improvements in CO2/N2 and H2/CO2 separation values.
Implementation Method 1
a permeable layer formed on the selective layer, wherein the permeable layer has a higher permeance than the selective layer but a lower permeance than any pinholes in the membrane
Implementation Method 2
Gas transport in membrane supports is generally in the Knudsen regime
Implementation Method 3
Such meso- (2-50 nm) and macro-defects (>50 nm) have a deleterious effect on the gas separation performance due to significant contributions of Knudsen flow, viscous flow, or both to the overall flow
Data Source
AI summary
Disclosed herein are membranes comprising a substrate, a support layer, and a selective layer. In some embodiments the membrane may further comprise a permeable layer. Methods of forming membranes are also disclosed comprising forming a support layer on a substrate, removing adsorbed species from the support layer, preparing a solution containing inorganic materials of a selective layer, contacting the support layer with the solution, drying the membrane, and exposing the membrane to rapid thermal processing. Also disclosed are methods of fluid purification comprising providing a membrane having a feed side and a permeable side, passing a fluid mixture across the feed side of the membrane, providing a driving force for transmembrane permeation, removing from the permeate side a permeate stream enriched in a purified fluid, and withdrawing from the feed side a fluid that is depleted in a purified fluid.