Composite Semipermeable Membrane Pore Radius Control
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Solution Overview
Problem
Current composite semipermeable membranes for seawater and brackish water desalination lack high fresh water productivity due to limitations in pore radius distribution and permeability coefficients.
Innovation Solution
A composite semipermeable membrane with a porous supporting membrane and a separation functional layer, where the standard deviation of pore radius is 0.025 nm or less, and the average pore radius is 0.15 nm or more, with a relative standard deviation of 0.089 or less, and a specific relationship between the pure water permeability coefficient and average pore radius, achieved through interfacial polycondensation using a polyfunctional amine and polyfunctional acid halide, and additional treatments to enhance permeability and salt removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pore radius distribution of the separation functional layer is not controlled, then the membrane structure is simpler to produce, but the fresh water productivity is reduced
Solution Approach 1:
The patent controls the pore radius distribution by adjusting the standard deviation to 0.025 nm or less and the average pore radius to 0.15 nm or more. This precise parameter control in the pore structure enables high fresh water productivity while maintaining effective salt removal, directly resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent employs a composite semipermeable membrane structure consisting of a porous supporting membrane and a separation functional layer. The separation functional layer is formed by interfacial polycondensation of polyfunctional amine and polyfunctional acid halide, creating a composite structure with controlled pore characteristics that achieves both high productivity and precise pore distribution.
2Productivity
If the pure water permeability coefficient is increased, then the fresh water productivity improves, but the salt removal ratio may be compromised
Solution Approach 1:
The patent establishes a specific relationship between the pure water permeability coefficient A and average pore radius R, where A/R^4 falls within 1.2×10^-9 to 5.1×10^-9 m/s/Pa/nm^4. This parameter optimization ensures that high permeability (improving productivity) is achieved while maintaining the pore size characteristics necessary for effective salt removal, thus resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent uses positron annihilation lifetime measurement to precisely characterize and control the pore radius distribution, creating a reproducible pore structure model. By copying this optimized pore structure through controlled interfacial polycondensation, the membrane achieves consistent high productivity and salt removal performance.
3Productivity
If the standard deviation of pore radius is reduced to 0.025 nm or less, then the fresh water productivity increases, but the manufacturing complexity increases
Solution Approach 1:
The patent achieves the extremely low standard deviation of pore radius (0.025 nm or less) through controlled interfacial polycondensation parameters, including the choice of polyfunctional amine and polyfunctional acid halide, reaction conditions, and processing parameters. This parameter control enables the formation of uniform pore structures that drive high fresh water productivity despite the manufacturing complexity.
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 high fresh water productivity with improved salt removal ratios and permeability coefficients, effectively addressing the limitations of existing membranes.
Implementation Method 1
composite semipermeable membrane useful for selective separation of a liquid mixture
Implementation Method 2
reverse osmosis membrane
Implementation Method 3
a diffusion coefficient of water in the separation functional layer
Implementation Method 4
a composite semipermeable membrane obtained by coating a porous supporting membrane with a separation functional layer including a crosslinked polyamide obtained by polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide
Data Source
AI summary
This composite semipermeable membrane is provided with: a porous supporting membrane that comprises a base and a porous supporting layer; and a separating function layer that is provided on the porous supporting layer. With respect to this composite semipermeable membrane, the standard deviation of pore radius of the separating function layer as determined by positron annihilation lifetime measurement is 0.025 nm or less.