Polyamide Membrane Chlorine Resistance via Interfacial Polymerization
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Solution Overview
Problem
Conventional water-treatment separating membranes have a short chlorine resistance duration and require separate post-treatment processes to maintain high salt rejection and permeation flux, which complicates their operation and maintenance.
Innovation Solution
A water-treatment separating membrane is manufactured by forming an aqueous amine solution layer on a porous support and dropping droplets of an organic solution containing an acyl halide compound, resulting in a polyamide active layer with increased specific surface area and extended chlorine resistance without the need for additional post-treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film of polyamide active layer is formed by conventional interfacial polymerization, then high salt rejection is achieved, but chlorine resistance decreases rapidly over time
Solution Approach 1:
The invention changes the physical state and surface morphology parameters of the polyamide active layer by controlling the interfacial polymerization process. By adjusting reaction conditions and polymerization kinetics, the membrane surface develops increased roughness and higher specific surface area, which enhances chlorine resistance while preserving salt rejection capabilities
Solution Approach 2:
The invention creates a composite structure within the polyamide active layer by forming an embossed or wrinkled surface morphology. This composite topography combines regions of varying thickness and density, resulting in improved chlorine resistance without compromising the thin film's salt rejection function
2Duration of action of stationary object
If the specific surface area of the active layer is increased to improve chlorine resistance, then a separate post-treatment process is required to coat the surface with electrically neutral polymer
Solution Approach 1:
The invention merges the active layer formation process with the surface morphology modification process. By controlling the interfacial polymerization conditions, the embossed or wrinkled surface structure is formed simultaneously with the polyamide layer, eliminating the need for separate post-treatment coating steps
Solution Approach 2:
The polyamide active layer serves dual functions: it provides salt rejection as its primary function and simultaneously provides the surface morphology needed for chlorine resistance. The layer self-organizes into an embossed or wrinkled structure during formation, eliminating the need for external post-treatment processes
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 achieves a high degree of salt rejection and permeation flux for an extended period, improving the membrane's durability and operational efficiency by enhancing surface roughness and chlorine resistance.
Implementation Method 1
impregnating the minute and porous support with an organic solution including trimesoyl chloride (TMC) so that the mPD contacts the TMC to allow interfacial polymerization and to form a polyamide layer
Implementation Method 2
When a level of external pressure, higher than osmotic pressure, is applied, the solvent may move from the solution having the higher concentration of the solute to the solution having the lower concentration of the solute. This phenomenon is known as reverse osmosis. By using the principle of reverse osmosis, various salts and organic materials may be separated by the semi-permeable membrane by using a pressure gradient as a driving force
Data Source
AI summary
A method of manufacturing a water-treatment separating membrane includes forming an aqueous amine solution layer on a porous support, and forming a polyamide active layer by dropping droplets of an organic solution including an acyl halide compound on the aqueous amine solution layer. A water-treatment separating membrane manufactured by the same also is provided.