Composite Polyamide Membrane via Non-Polar Solvent Interfacial Polymerization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current composite polyamide membranes for fluid separations, such as reverse osmosis and nanofiltration, face limitations in salt rejection and molecular weight cutoff, with a need for improved performance through new combinations of monomers, additives, and post-treatments.
Innovation Solution
A method involving the application of a polar solution with a polyfunctional amine monomer and a non-polar solution with a polyfunctional acyl halide monomer to a porous support for interfacial polymerization, followed by treatment with an aqueous nitrous acid solution to enhance the thin film polyamide layer's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional monomer combinations and coating solutions are used for interfacial polymerization, then the membrane formation process is straightforward, but salt rejection and molecular weight cutoff performance are limited
Solution Approach 1:
The patent changes the solvent system parameters by using a non-aqueous polar solvent (acetonitrile) instead of traditional aqueous solutions, and combines it with specific monomer ratios (mPD:TDMC = 1:1 to 1:4) to achieve improved salt rejection performance while maintaining a manageable process
Solution Approach 2:
The patent creates a composite membrane structure by combining polysulfone support material with a polyamide thin film layer formed through interfacial polymerization of m-phenylenediamine and trimesoyl chloride in a non-aqueous system, achieving enhanced separation performance
2Productivity
If the polyamide layer is made thinner to improve flux rates, then permeability increases, but salt rejection performance deteriorates
Solution Approach 1:
The patent changes the chemical environment parameters by using a non-aqueous polar solvent system (acetonitrile) with specific monomer concentrations and ratios, which enables the formation of a thin polyamide layer that maintains both high flux rates and excellent salt rejection performance
Solution Approach 2:
The patent optimizes the local composition of the polyamide layer by controlling the distribution and reaction of m-phenylenediamine and trimesoyl chloride monomers in the non-aqueous system, creating a thin layer with heterogeneous structure that provides both high permeability and selective rejection
3Reliability
If traditional aqueous coating solutions are used for interfacial polymerization, then the process is well-established, but membrane performance in rejecting salts and organic molecules is insufficient
Solution Approach 1:
The patent fundamentally changes the solvent system from aqueous to non-aqueous polar (acetonitrile), which alters the polymerization kinetics and membrane structure formation, resulting in enhanced separation efficiency for salts and organic molecules while maintaining ease of manufacture through a modified but straightforward process
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 results in membranes with improved salt rejection and flux rates, particularly effective in rejecting salts and larger organic molecules, enhancing the membrane's separation efficiency in reverse osmosis and nanofiltration applications.
Implementation Method 1
interfacially polymerizing the monomers to form a thin film polyamide layer
Implementation Method 2
applying an aqueous solution of nitrous acid to the thin film polyamide layer
Implementation Method 3
reverse osmosis and nanofiltration applications
Implementation Method 4
nanofiltration applications
Data Source
AI summary
A method for making a composite polyamide membrane comprising a porous support and a thin film polyamide layer, wherein the method includes: i) applying a polar solution comprising a polyfunctional amine monomer, and a non-polar solution comprising a polyfunctional acyl halide monomer to a surface of a porous support and interfacially polymerizing the monomers to form a thin film polyamide layer, wherein the non-polar solution further comprises at least 50 vol % of a C5 to C20 aliphatic hydrocarbon and from 2 to 25 vol % of benzene or benzene substituted with one or more C1 to C6 alkyl groups; and ii) applying an aqueous solution of nitrous acid to the thin film polyamide layer.