Reverse Osmosis Membrane Pore Structure Control
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Solution Overview
Problem
Conventional reverse osmosis membranes suffer from low initial permeation flux efficiency, deterioration of water purifying function, and reduced salt rejection due to fouling, necessitating a solution for improved durability and water permeability characteristics.
Innovation Solution
A method of manufacturing a reverse osmosis membrane by forming a polysulfone layer using a mixed solvent with solvents having different solubility parameter values, such as N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL), to adjust pore diameter distribution, density, and pore area ratio, resulting in improved permeation flux, antifouling properties, and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional polyamide-based reverse osmosis membrane is manufactured by forming a polyamide active layer on a microporous support, then salt rejection is achieved, but initial permeation flux efficiency is low
Solution Approach 1:
The patent changes the chemical composition parameters of the polysulfone layer by incorporating hydrophilic polymers (polyethylene glycol, polyvinyl alcohol, or carboxymethyl cellulose) in specific ratios (1-50 wt% of total polysulfone). This parameter change modifies the pore structure and hydrophilicity, resulting in improved permeation flux while maintaining salt rejection capability.
Solution Approach 2:
The patent creates a composite polysulfone layer by combining polysulfone with hydrophilic polymers. This composite structure integrates the mechanical strength and pore-forming capability of polysulfone with the hydrophilicity and antifouling properties of the added polymers, achieving both high permeation flux and sustained water purifying function.
2Productivity
If water treatment is performed using a reverse osmosis membrane, then water purification is achieved, but solutes or ionic compounds are adsorbed to the membrane surface causing fouling and degradation of permeability characteristics
Solution Approach 1:
The patent modifies the surface chemistry parameters of the membrane by incorporating hydrophilic polymers with specific functional groups. This changes the surface energy and wettability, creating a fouling-resistant surface that reduces adsorption of solutes and ionic compounds, thereby maintaining permeability characteristics over time.
Solution Approach 2:
The patent converts the potential harm of polymer addition into a benefit by selecting hydrophilic polymers that, while potentially adding complexity, actually reduce fouling through their hydrophilic nature. These polymers create a hydration layer that prevents foulant adhesion, turning a compositional modification into an antifouling mechanism.
3Manufacturing precision
If the polysulfone layer is formed using a single solvent, then the manufacturing process is simple, but the pore diameter distribution and density cannot be optimized
Solution Approach 1:
The patent changes the physical-chemical parameters of the solvent system by using mixed solvents with different solubility parameters and evaporation rates. This allows precise control over phase inversion kinetics, resulting in optimized pore diameter distribution and density in the polysulfone layer.
Solution Approach 2:
The patent uses mixed solvents as intermediaries that mediate the phase inversion process. The different solvents in the mixture play complementary roles: one provides good polymer dissolution while the other controls evaporation rate and pore formation, together achieving precise pore structure control.
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 method enhances permeation flux and salt rejection while maintaining superior antifouling properties and durability, outperforming existing membranes in water treatment applications.
Implementation Method 1
The polysulfone is dissolved in a mixture of solvents and cast on a polyethylene terephthalate fabric followed by phase inversion
Implementation Method 2
using a mixed solvent containing two solvents having different solubility parameter values to thereby adjust the pore diameter distribution, density, pore area ratio
Implementation Method 3
when external pressure having a level greater than that of osmotic pressure is applied, the solvent moves towards the solution having a low solute concentration, and such a phenomenon is known as reverse osmosis
Implementation Method 4
Osmosis is a phenomenon in which a solvent moves from a solution having a low solute concentration to another solution having a high solute concentration by passing through a semi-permeable separation membrane
Implementation Method 5
adjust the pore diameter distribution, density, pore area ratio, and the like, of pores formed in a polysulfone layer using a difference in the outflow rates of the solvents
Data Source
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Figure 5
AI summary
There are provided a method of manufacturing a reverse osmosis membrane and a reverse osmosis membrane manufactured thereby. The method includes forming a polysulfone layer by applying a solution including a mixed solvent containing two or more solvents having different solubility parameter values to a surface of a porous support; and forming an active layer on the polysulfone layer.