Composite Membrane Thickness Control for Water Permeability
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Solution Overview
Problem
Current composite semipermeable membranes face challenges in achieving high water permeation performance and chemical resistance, leading to decreased membrane performance over time due to surface pollution and limited durability during chemical washing processes.
Innovation Solution
A composite semipermeable membrane with a polyamide separation functional layer having a standard deviation of membrane thickness of 2.00 nm or less, formed on a porous support membrane with a multilayered structure, utilizing polysulfone and polyfunctional amine/polyfunctional acid halide interfacial polycondensation, which enhances mechanical strength and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the separation active layer is made thinner to increase water permeability, then water permeation performance improves, but the membrane becomes more susceptible to chemical damage and pollution
Solution Approach 1:
The invention applies local quality by creating a non-uniform thickness distribution in the separation active layer, with thinner regions (higher permeability) and thicker regions (higher chemical resistance). The standard deviation of membrane thickness is controlled to be 1.5 nm or less, ensuring that while the overall thickness varies to optimize performance, the variation is limited to maintain structural integrity and resistance to chemical damage.
2Productivity
If the membrane is used for extended periods to increase productivity, then more water is produced, but the membrane surface becomes polluted and performance deteriorates
Solution Approach 1:
The invention applies beforehand cushioning by designing a separation active layer with controlled thickness variation that provides a buffer against pollution and chemical damage. The thicker portions of the layer act as a protective cushion that preserves the underlying support structure and maintains performance even when surface pollution occurs, allowing for extended operation periods between chemical washes.
3Reliability
If chemical washing is performed frequently to maintain membrane performance, then membrane performance is maintained, but operational time is lost and running costs increase
Solution Approach 1:
The invention applies preliminary action by designing the separation active layer with inherent resistance to pollution and chemical damage through controlled thickness distribution. This preliminary design feature reduces the frequency and intensity of chemical washing required, allowing the membrane to maintain acceptable performance levels for longer periods without intervention, thus reducing operational time loss.
4Productivity
If additives are added during interfacial polycondensation to enlarge protuberances and improve water permeability, then water permeability increases, but the removal rate decreases
Solution Approach 1:
The invention applies parameter changes by controlling the thickness distribution parameters of the separation active layer, specifically maintaining a standard deviation of membrane thickness of 1.5 nm or less. This parameter control achieves the desired balance between water permeability and removal rate without requiring additives during polycondensation, thereby avoiding the trade-off between these two performance metrics.
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 water permeability and chemical resistance, maintaining performance stability over a long period with minimal deterioration during chemical washing, ensuring continuous operation.
Implementation Method 1
utilizing polysulfone and polyfunctional amine/polyfunctional acid halide interfacial polycondensation
Implementation Method 2
the use of a membrane separation process... reverse osmosis membrane... selective separation of a liquid mixture
Data Source
AI summary
A composite semipermeable membrane in which a polyamide separation functional layer is formed on a porous support membrane comprising a substrate and a porous support, wherein the standard deviation of the membrane thickness of the separation functional layer is 2.00 nm or less. A high-performing composite semipermeable membrane that has high water permeability and high chemical resistance is provided.