Polyetherimide Nanofiltration Membrane Room-Temperature Imidization
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Solution Overview
Problem
Current nanofiltration membrane preparation methods, particularly involving thermal or chemical imidization, face challenges such as high energy consumption, environmental pollution, and low rejection rates for compounds with molecular weights between 150 to 200, due to the use of expensive monomers and complex, energy-intensive processes.
Innovation Solution
A method for preparing a polyetherimide composite nanofiltration membrane using interfacial polymerization with 1,2,4,5-benzene tetracarbonyl chloride (BTC) on a polyetherimide support membrane, involving specific solvent and additive combinations, followed by surface modification with m-phenylenediamine and EDC.HCl, to create a membrane with improved rejection and reduced energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal imidization method is used to prepare polyimide membrane, then the membrane shows good separation performance, but high energy consumption occurs due to continuous high temperature treatment
Solution Approach 1:
The patent changes the temperature parameter from high temperature thermal imidization to room temperature operation by using EDC.HCl as a zero-length crosslinking agent, which enables the imidization reaction to proceed without external heating, thereby significantly reducing energy consumption while maintaining membrane separation performance
Solution Approach 2:
The patent replaces the thermal energy input system with a chemical reaction system using EDC.HCl that proceeds at room temperature, substituting the need for continuous high temperature treatment with a chemically-driven self-sufficient imidization process
2Ease of manufacture
If chemical imidization method is used with agents like benzene, acetic anhydride, acetone, then the imidization process can be conducted, but environmental disruption occurs and the membrane has larger MWCO (500-800)
Solution Approach 1:
The patent uses EDC.HCl as a disposable zero-length crosslinking agent that reacts completely and forms stable amide bonds without requiring recovery or disposal of hazardous solvents, eliminating environmental disruption associated with traditional chemical imidization agents like benzene and acetic anhydride
Solution Approach 2:
The patent changes the chemical parameters by using EDC.HCl in aqueous or alcoholic solutions instead of hazardous organic solvents, enabling the imidization process to proceed under environmentally benign conditions while achieving the desired membrane performance with appropriate MWCO
3Reliability
If traditional interfacial polymerization is used with trimesoyl chloride, then the membrane shows good performance, but high cost occurs due to expensive monomer
Solution Approach 1:
The patent changes the monomer parameter from expensive trimesoyl chloride to cheaper 1,2,4,5-benzene tetracarbonyl chloride (BTC), which provides similar or improved membrane performance while significantly reducing material cost, thereby resolving the cost-performance trade-off
4Ease of manufacture
If thermal imidization is used for treating composite membrane, then imidization can be achieved, but uneven heating surface occurs which increases energy consumption
Solution Approach 1:
The patent replaces the thermal heating system with a chemical reaction system using EDC.HCl that proceeds uniformly at room temperature, eliminating the uneven heating problem inherent in thermal imidization methods and reducing energy consumption simultaneously
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 a polyetherimide composite nanofiltration membrane with high rejection rates (>90%) for low molecular weight compounds, reduced energy consumption, and lower environmental impact, while being cost-effective and having a longer membrane lifetime.
Implementation Method 1
the interfacial polymerization method has become the most commonly-used method for preparing a composite nanofiltration membrane. A polymerization reaction is conducted on an interface of a two-phase solution
Implementation Method 2
nanofiltration is a pressure-driven membrane separation process between reverse osmosis and ultrafiltration with a molecular weight cut-off (MWCO) generally in a range of 200 to 1000
Implementation Method 3
blade coating at a range from 12 g to 20 g of the casting solution onto a smooth surface of a nonwoven fabric, placing under an air atmosphere for 0 to 60 seconds and putting into deionized water for 5 to 60 min of immersion, taking out and drying in the air
Data Source
AI summary
The present invention relates to a polyetherimide composite nanofiltration membrane and a preparation method thereof, the method comprises the following steps: (1) dissolving polyetherimide and an additive into an organic solvent, stirring and keeping aside for deaeration to prepare a casting solution, blade coating of the casting solution onto a smooth surface of a nonwoven fabric, and placing under an air atmosphere and then putting into deionized water to obtain a support membrane 1, wherein the surface of the nonwoven fabric coated with the casting solution is referred to as surface A; (2) immersing the surface A of the support membrane 1 into an aqueous solution of m-phenylenediamine, taking out and drying in the air, then immersing the surface A into a solution of 1,2,4,5-benzene tetracarbonyl chloride in n-hexane or cyclohexane, and taking out and drying in the air to obtain a support membrane 2; and (3) immersing the surface A of the support membrane 2 into an aqueous solution of EDC.HCl, then adding NHS into the aqueous solution of EDC.HCl, then adding an aqueous solution of ethylene diamine and keeping aside, and then rinsing with deionized water to obtain a polyetherimide composite nanofiltration membrane. The method of the invention has the advantages of low cost, low energy consumption and low pollution; and also has high rejection towards low-molecular-weight compound, stable performance and a longer lifetime.