Composite Membrane Projections for Stable Desalination
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Solution Overview
Problem
Conventional composite semipermeable membranes experience a decrease in water permeability and salt-removing ability when pressure fluctuations occur due to frequent operation and stopping, which affects their performance in desalination processes.
Innovation Solution
A composite semipermeable membrane with a porous supporting membrane and a separation functional layer, where the separation functional layer has a specific projection structure with an average number density of 10.0 to 30.0 projections/μm and an average height of less than 100 nm, and a multilayer porous supporting layer structure, is developed to maintain performance under fluctuating pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional composite semipermeable membranes are used for reverse osmosis, then high salt-removing ability is achieved, but water permeability decreases under fluctuating pressure conditions
Solution Approach 1:
The invention changes the physical parameters of the separation functional layer by controlling the height and number density of projections. The projections have a height of 10 nm to 100 nm and a number density of 10.0 to 30.0 projections/μm, which optimizes both salt rejection and water permeability under fluctuating pressure conditions.
Solution Approach 2:
The invention creates local structural variations in the separation functional layer through projections. These projections are distributed across the membrane surface with specific density and height characteristics, creating localized pathways that facilitate water transport while maintaining salt rejection performance.
2Reliability
If the separation functional layer is made denser to improve salt rejection, then salt-removing ability increases, but water permeability decreases
Solution Approach 1:
The invention utilizes a porous supporting membrane with controlled pore structure. The porous supporting layer provides mechanical strength while allowing water transport, and the projections on the separation functional layer create additional pathways that maintain water permeability without compromising salt rejection.
Solution Approach 2:
The invention employs a composite structure consisting of a porous supporting membrane and a separation functional layer with projections. This composite design combines the advantages of both layers: the porous support provides structural integrity and water transport pathways, while the projection-containing separation layer ensures efficient salt rejection.
3Productivity
If the membrane operates under high pressure for extended periods, then water production increases, but the membrane performance changes due to pressure-induced densification
Solution Approach 1:
The porous supporting membrane is designed with sufficient porosity and mechanical strength before operation to withstand high pressure conditions. This pre-engineered structural resilience prevents pressure-induced densification during operation, maintaining stable membrane performance over time.
Solution Approach 2:
The invention optimizes the porosity and mechanical properties of the porous supporting layer to resist compression under high pressure. The specific porosity and structural parameters of the support layer are tuned to maintain dimensional stability and prevent performance degradation during prolonged high-pressure operation.
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 water production rate of 1.0 m3/m2/day and a salt rejection of 99.5% or higher, even after repeated filtration cycles with pressure fluctuations, ensuring stable performance and efficiency in desalination processes.
Implementation Method 1
a composite semipermeable membrane useful for selective separation of a liquid mixture. The composite semipermeable membrane obtained is suitable, for example, for desalination of seawater or brackish water
Implementation Method 2
a porous supporting membrane having a substrate and a porous supporting layer disposed on the substrate
Data Source
AI summary
A composite semipermeable membrane includes a porous supporting membrane and a separation functional layer, in which, in cross-sections having a length of 2.0 μm in a membrane surface direction, the average number density of projections in the separation functional layer which have a height of one-fifth or more of the 10-point average surface roughness is 10.0-30.0 projections/μm and the projections have an average height less than 100 nm, and in which a water production rate and a salt rejection are predetermined values or more after an aqueous solution is passed through under certain conditions.