Polyelectrolyte Complex Membrane Formation via Salt Dilution
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Solution Overview
Problem
Current membrane fabrication processes for microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes rely on hazardous organic solvents and multiple time-consuming steps, limiting the feasibility of continuous production for flat-sheet, hollow fiber, and tubular geometries.
Innovation Solution
A salt dilution induced phase separation process is used to produce polyelectrolyte complex (PEC) membranes, where polyanions and polycations are dissolved in an aqueous medium at an overcritical salt concentration, suppressing complexation, and then exposed to a dilution process to form PEC membranes without organic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-solvent induced phase separation (NIPS) with organic solvents is used to fabricate polymeric membranes, then membrane formation and pore structure can be achieved, but hazardous components and environmental damage occur
Solution Approach 1:
The patent changes the fundamental parameter of the fabrication medium from organic solvents to aqueous electrolyte solutions. By using water-soluble polyelectrolytes and controlling ionic strength, the invention achieves membrane formation without hazardous organic solvents, directly resolving the contradiction between reliable membrane formation and elimination of harmful factors
Solution Approach 2:
The patent converts the typically problematic role of salts (which can interfere with polymer solutions) into a beneficial mechanism. By utilizing salt-induced phase separation, where added electrolytes trigger complex coacervation and membrane formation, the invention transforms a potential harm into the core mechanism for safe, solvent-free membrane fabrication
2Manufacturing precision
If traditional multi-step fabrication processes are used for NF membranes, then selective separation layers can be formed, but production time and process complexity increase
Solution Approach 1:
The patent merges multiple traditional fabrication steps into a single integrated process. By combining polymer dissolution, complex formation, and membrane structure creation into one salt-induced phase separation step, the invention simultaneously achieves selective separation layer formation while dramatically reducing fabrication time and process complexity
Solution Approach 2:
The patent employs preliminary complex formation between polycations and polyanions in aqueous solution before membrane fabrication. This pre-complexation creates a ready-to-form membrane structure that rapidly solidifies upon salt addition, eliminating the need for time-consuming intermediate steps and enabling quick, efficient membrane production
3Object-affected harmful factors
If layer-by-layer polyelectrolyte coating is used to form selective layers, then non-hazardous materials can be used, but additional support structures and process steps are required
Solution Approach 1:
The patent extracts and eliminates the need for separate support structures by enabling the formation of self-supporting, freestanding polyelectrolyte complex membranes. The salt-induced phase separation process creates mechanically stable membranes that do not require additional substrates, thereby simplifying the overall device structure while maintaining the use of non-hazardous materials
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
This method enables the production of PEC membranes with predetermined porosity in various geometries, reducing the need for hazardous components and simplifying the fabrication process, allowing for flexible tunability and cost-effective production.
Implementation Method 1
salt dilution induced phase separation
Implementation Method 2
the polymer precipitates and a porous membrane structure is formed
Implementation Method 3
the complexation of the polyelectrolyte is suppressed by the overcritical salt concentration
Data Source
AI summary
The present invention relates to a method for producing a polyelectrolyte complex (PEC) membrane having a predetermined porosity via salt dilution induced phase separation, in which a liquid polymer solution (P) containing polyanions (A) and polycations (C) dissolved in an aqueous medium at an overcritical salt concentration is exposed to an aqueous medium.