Membrane Pore Control via Polyetheramine for Virus Removal
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Solution Overview
Problem
Current ultrafiltration membranes are inadequate for purifying drinking water due to their inability to effectively remove bacteria and viruses smaller than 1-2 microns and 17 nanometers, respectively, as they often suffer from defects, low mechanical strength, fouling, and inconsistent pore formation.
Innovation Solution
Incorporating a specific class of polyetheramine into the casting mixture of membrane-forming polymers, ensuring no reactive components are present, results in membranes with a dense, uniform surface layer and high permeability, reducing defects and enhancing rejection capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ultrafiltration membranes with pore size 2 microns to 50 nanometers are used, then liquid flux is maintained, but the ability to remove small viruses and bacteria is insufficient
Solution Approach 1:
The patent changes the pore size parameter of the membrane to be smaller than 17 nanometers, which is below the size of the smallest virus (Porcine circovirus at 17 nm). This parameter change enables the membrane to remove both viruses and bacteria while maintaining acceptable liquid flux through optimized membrane structure
2Reliability
If membrane pore size is reduced to remove smaller particles, then virus and bacteria removal improves, but liquid flux decreases steeply
Solution Approach 1:
The patent creates a membrane with non-uniform pore distribution, where the surface layer has smaller pores for high rejection of particles, while the bulk membrane maintains larger pores and higher porosity for maintaining liquid flux. This local quality differentiation resolves the contradiction between removal efficiency and productivity
3Reliability
If membrane pore size is made smaller than 17 nanometers, then complete virus removal is achieved, but membrane defects and mechanical strength issues arise
Solution Approach 1:
The patent applies local quality by creating a thin surface layer with small pores for virus removal, while the bulk membrane maintains larger pores and standard mechanical properties. This prevents the entire membrane from suffering mechanical weakness due to uniformly small pores throughout the structure
4Manufacturing precision
If membrane surface pores are minimized, then molecular cut-off is improved, but membrane fouling increases
Solution Approach 1:
The patent creates a membrane where the surface layer has small pores for precise molecular cut-off, while the bulk membrane has larger pores that prevent fouling by allowing trapped particles to be flushed through during operation, thus resolving the contradiction between precision and anti-fouling
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 resulting membranes exhibit exceptional water permeability, reduced fouling, and precise control over pore size and architecture, making them suitable for ultrafiltration applications such as drinking water purification and reverse osmosis.
Implementation Method 1
the membrane-forming polymer, which is itself insoluble in water, is dissolved in a solvent which is soluble in water. The resulting solution is cast into a quenching tank containing water, whereupon the solvent dissolves in the water and the polymer precipitates out into the solid phase
Implementation Method 2
It is known to use pore-forming additives, for example LiCl and high molecular weight organic additives such as polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG, also known as polyethylene oxide, PEO), to help control pore formation
Implementation Method 3
If the surface pores of the membrane skin layer are the smallest pores in the membrane, the surface pore size determines the molecular cut-off of the membrane
Data Source
AI summary
A method of preparing a membrane comprising the steps of: a) mixing together a membrane-forming polymer, a water-soluble polyetheramine, and a solvent, said mixture containing no component which will react chemically with the polyetheramine; and b) casting said mixture to form the polymer into a solid membrane.