Composite Semipermeable Membrane with Local Density Substrate
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Solution Overview
Problem
Current composite semipermeable membranes face challenges in balancing strength and permeability, with excessive porous support infiltration leading to damage and insufficient salt rejection performance.
Innovation Solution
A composite semipermeable membrane with a substrate having press-bonded and non-press-bonded parts, where the porous support is moderately impregnated into the substrate, creating a structure that enhances mechanical strength and permeability while maintaining salt rejection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate bulk density is increased to prevent excessive porous support infiltration, then the porous support infiltration is reduced, but the porous support cannot sufficiently infiltrate the substrate resulting in peeling and membrane damage
Solution Approach 1:
The substrate is designed with spatially varying bulk density: the front surface region (contacting porous support) has lower bulk density (0.85-0.95 g/cm³) to enable sufficient porous support infiltration and strong bonding, while the back surface region has higher bulk density (0.97-1.05 g/cm³) to prevent excessive infiltration and protect the separation functional layer. This local quality differentiation resolves the contradiction between preventing infiltration and ensuring bonding strength.
2Strength
If the porous support infiltration is allowed to reach the back surface to ensure sufficient infiltration, then the bonding strength is improved, but the porous support sticks to or rubs against the separation functional layer causing damage
Solution Approach 1:
The substrate exhibits local quality variation in bulk density along its thickness direction. The front surface region has lower bulk density (0.85-0.95 g/cm³) allowing controlled infiltration, while the back surface region has higher bulk density (0.97-1.05 g/cm³) acting as a barrier to prevent the porous support from reaching the separation functional layer, thus eliminating the harmful effect of support contact with the functional layer.
3Object-affected harmful factors
If the substrate bulk density is uniformly high throughout, then excessive infiltration is prevented, but insufficient infiltration occurs resulting in peeling and membrane damage
Solution Approach 1:
Rather than uniform high bulk density, the substrate implements local quality differentiation: the front surface region maintains lower bulk density (0.85-0.95 g/cm³) to ensure sufficient porous support infiltration and strong bonding, while only the back surface region has higher bulk density (0.97-1.05 g/cm³) to prevent excessive infiltration. This resolves the contradiction by localizing the high density function.
4Strength
If the substrate is made with low bulk density to allow sufficient porous support infiltration, then bonding strength is improved, but the porous support excessively infiltrates and reaches the back surface causing damage
Solution Approach 1:
The substrate uses local quality differentiation where the front surface region has lower bulk density (0.85-0.95 g/cm³) to allow sufficient infiltration for strong bonding, while the back surface region has higher bulk density (0.97-1.05 g/cm³) to stop infiltration before reaching the separation functional layer. This localized approach resolves the contradiction between enabling infiltration and preventing damage.
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 a balance between strength and permeability, ensuring durability and effective salt removal, as demonstrated by high salt rejection ratios and permeation flux.
Implementation Method 1
the porous support is moderately impregnated into the substrate
Implementation Method 2
composite semipermeable membrane useful for selective separation of a liquid mixture
Implementation Method 3
reverse osmosis membranes and nanofiltration membranes are composite semipermeable membranes
Data Source
Figure 1
AI summary
The purpose of the present invention is to provide a composite semipermeable membrane having achieved both strength and water-permeable properties. This composite semipermeable membrane is provided with a substrate, a porous support body disposed on the substrate, and a separation function layer provided on the porous support body. The substrate has a structure provided with a crimped portion and a non-crimped portion. The porous support body is impregnated inside a crimped portion and inside a non-crimped portion of the substrate.