Forward Osmosis Membrane Reducing Internal Concentration Polarization
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Solution Overview
Problem
Existing forward osmosis membranes face limitations such as low water permeability, inferior salt rejection, and internal concentration polarization due to unsuitable membrane substructures, which hinder efficient separation of water and solutes.
Innovation Solution
A thin film composite forward osmosis membrane is developed with a porous substrate and a rejection layer formed by immersing a polymer solution in a coagulant bath, followed by interfacial polymerization to create a polyamide rejection layer, which minimizes internal concentration polarization and maintains high water permeability and salt rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse osmosis membrane with high water permeability and high salt rejection is used, then water permeability and salt rejection are improved, but internal concentration polarization increases due to thick non-woven fabric substrate
Solution Approach 1:
The patent employs a porous non-woven fabric substrate with controlled pore size and distribution to facilitate mass transport while maintaining mechanical strength. The porous structure reduces internal concentration polarization by enabling efficient solute and water transport, thereby resolving the contradiction between salt rejection and internal concentration polarization.
Solution Approach 2:
The patent creates a composite membrane structure combining a non-woven fabric substrate with a selective rejection layer. This composite structure allows the substrate to provide mechanical support and mass transport pathways while the rejection layer provides salt separation, achieving both high water permeability and low internal concentration polarization.
2Strength
If a thick non-woven fabric substrate is used to provide mechanical strength, then mechanical strength is improved, but membrane porosity decreases and water flux is reduced
Solution Approach 1:
The patent utilizes a porous non-woven fabric substrate where pore size and porosity are optimized to balance mechanical strength and water flux. The porous structure allows sufficient water and solute transport while maintaining the structural integrity needed for forward osmosis operation.
Solution Approach 2:
The patent adjusts key parameters of the non-woven fabric substrate including pore size, porosity, and fiber diameter to achieve optimal performance. By controlling these parameters, the substrate provides adequate mechanical strength while maintaining high water flux and low internal concentration polarization.
3Strength
If a sponge-like polymeric layer is used in reverse osmosis membrane, then mechanical strength under high pressure is improved, but mass diffusion is hindered and water flux is reduced under forward osmosis conditions
Solution Approach 1:
The patent replaces the dense sponge-like polymeric layer with a porous non-woven fabric substrate. This porous structure maintains mechanical strength through fiber network architecture while enabling efficient mass diffusion and water transport, thereby resolving the contradiction between mechanical strength and water flux under forward osmosis conditions.
Solution Approach 2:
The patent substitutes the pressure-driven mechanical strength mechanism of reverse osmosis membranes with a structure-based mechanical strength approach suitable for forward osmosis. The porous non-woven fabric provides structural support without relying on high-pressure resistance, enabling efficient mass transport at lower osmotic pressures.
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 enhanced water flux and solute separation efficiency, reducing internal concentration polarization and improving salt rejection, making it suitable for various applications including water purification and desalination.
Implementation Method 1
forming a thin film of a polymer solution on a suitable substrate, wherein the polymer solution comprises at least one polymer and optionally one or more additives in a suitable solvent; immersing the thin film in a coagulant bath to form the porous substrate
Implementation Method 2
Forward osmosis (FO), also referred to as osmosis or direct osmosis, is a natural phenomenon, which can be defined as the net movement of water molecules across a semi-permeable membrane from a less concentrated solution to a more concentrated solution
Implementation Method 3
the semi-permeable membrane prevents the passage of solute molecules and ions through the membrane while allowing water molecules to pass through it
Implementation Method 4
mass diffusion between bulk solution and the interior surface of selective layer will be greatly hindered by this substrate
Data Source
AI summary
A method of forming a forward osmosis membrane having a porous substrate and a rejection layer is provided. The method comprises a) forming a thin film of a polymer solution on a suitable substrate, wherein the polymer solution contains at least one polymer and optionally one or more additives in a suitable solvent, b) immersing the thin film in a coagulant bath to form the porous substrate; and c) forming a rejection layer on the porous substrate. A forward osmosis membrane is also provided.