Stepwise Interfacial Polymerization for Low-Pressure Nanofiltration Membranes
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Solution Overview
Problem
Current nanofiltration (NF) membrane technologies are limited by high operation pressure requirements and lack of cost-effective methods for fabricating hollow fiber NF membrane composites with improved performance for separating or concentrating organic compounds.
Innovation Solution
A stepwise interfacial polymerization method is employed to create a hollow fiber NF membrane composite, comprising a cross-linked aromatic polyamide layer on a hollow fiber ultrafiltration membrane, using specific monomeric reactants and interfacial polymerization steps to form a NF-functionalized layer, allowing for operation at lower pressures and enhanced rejection rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nanofiltration membranes are used, then separation capability is achieved, but operation pressure requirement is high
Solution Approach 1:
The patent modifies the chemical composition and cross-linking density parameters of the polyamide active layer through controlled interfacial polymerization conditions (monomer concentration, reaction time, temperature, catalyst usage) to optimize pore size and charge density, enabling effective separation at lower operating pressures
Solution Approach 2:
The patent creates a composite membrane structure with a microporous support layer and a cross-linked polyamide active layer, combining the mechanical strength of the support with the selective separation properties of the polyamide network, achieving both low pressure operation and high separation capability
2Reliability
If hollow fiber NF membrane composites are fabricated with improved performance, then rejection rate increases, but fabrication cost and complexity increase
Solution Approach 1:
The fabrication process is divided into distinct sequential steps: (1) preparation of hollow fiber UF support, (2) first interfacial polymerization step forming initial polyamide layer, (3) second interfacial polymerization step forming cross-linked NF-functionalized layer. This segmentation enables precise control of each layer's properties and simplifies process optimization
Solution Approach 2:
The hollow fiber ultrafiltration membrane is prepared and characterized before the interfacial polymerization steps, establishing a controlled porous support structure that pre-determines the morphology and performance of the final NF composite layer, enabling better rejection rates with controlled fabrication complexity
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 enables NF membrane composites to operate at pressures less than 0.5 MPa with a molecular weight cut-off of 400 Da, achieving a rejection rate higher than 80% and suitable for pH 2-10 feed solutions, with water flux ranging from 8-20 L/m²hr, suitable for selective separation or concentration of organic compounds.
Implementation Method 1
A stepwise interfacial polymerization method is employed to create a hollow fiber NF membrane composite, comprising a cross-linked aromatic polyamide layer on a hollow fiber ultrafiltration membrane
Implementation Method 2
Nanofiltration is a membrane filtration capability which can be used to filter both natural and synthetic organic compounds. The nominal pore size of NF membrane is typically around 1 nm
Implementation Method 3
the organic molecules or inorganic ions in aqueous solutions can be concentrated or separated by a positive osmotic pressure to one side of a filtration membrane
Data Source
AI summary
Novel low-pressure nanofiltration membrane composites for rejecting organic compounds are prepared by interfacial polymerization on a microporous hollow fiber supporting membrane. The interfacial polymerization reaction is carried out using an essentially monomeric polyamine reactant having at least two amine functional groups per molecule, and an essentially monomeric amine-reactive polyfunctional aromatic or cycloaliphatic acyl halide having at least two acyl halide groups per molecule. The composite can be fabricated by stepwise polymerization reactions with different reactant recipes at each step.