Membrane Post Treatment for Water Permeability
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Solution Overview
Problem
Existing polymeric membranes used in ultrafiltration and microfiltration applications, particularly those made from hydrophobic materials like PVdF, face challenges in achieving high water permeability while maintaining mechanical and chemical stability, as previous attempts to hydrophilize them often result in reduced permeability and instability.
Innovation Solution
Incorporating a cross-linkable hydrophilic component into the membrane dope and treating it with a cross-linking agent, such as hydroxyl radicals generated from an aqueous solution of transition metal ions and hydrogen peroxide, to enhance permeability without compromising mechanical integrity or chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrophobic polymeric membranes are used to maintain mechanical strength and chemical resistance, then reliability is improved, but water permeability deteriorates due to high pressure requirements (150-300 psi) and uneven wetting
Solution Approach 1:
The patent applies parameter changes by modifying the chemical properties of the membrane through cross-linking treatment. The cross-linking process changes the physical and chemical parameters of the polymeric structure, creating a network that simultaneously enhances mechanical strength and improves hydrophilicity, thereby increasing water permeability without requiring excessive pressure
Solution Approach 2:
The patent employs composite materials by combining the hydrophobic polymeric base material with hydrophilic cross-linking agents. This creates a composite structure where the cross-linked regions provide both mechanical reinforcement and enhanced water affinity, resolving the contradiction between durability and permeability
2Productivity
If previous hydrophilization methods are applied to improve water permeability, then productivity is improved, but reliability deteriorates due to reduced chemical stability and mechanical instability
Solution Approach 1:
The patent replaces mechanical hydrophilization methods (such as physical coating or surface modification) with a chemical cross-linking mechanism. This substitution allows for permanent integration of hydrophilic properties into the membrane structure through chemical bonds, ensuring both improved permeability and enhanced stability
Solution Approach 2:
The patent utilizes strong oxidizing agents (such as peracetic acid or hydrogen peroxide) to facilitate the cross-linking reaction. These oxidants accelerate the formation of cross-links between polymer chains, creating a stable hydrophilic network that permanently improves water permeability while maintaining structural integrity
3Productivity
If sufficient pressure (150-300 psi) is applied to force water through hydrophobic membranes, then water permeability is improved, but the membrane may be damaged and does not become wetted evenly
Solution Approach 1:
The patent introduces cross-linking as an intermediary mechanism that mediates between the hydrophobic polymer structure and water. The cross-linked hydrophilic groups act as intermediaries that facilitate water interaction with the membrane, enabling even wetting and permeation at lower pressures without mechanical damage
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 significantly improves water permeability by up to 200% while maintaining pore size and mechanical strength, making the membranes suitable for various filtration applications, including water and wastewater treatment.
Implementation Method 1
treating said porous polymeric membrane with a cross linking agent
Implementation Method 2
cross linking by the action of hydroxyl radicals generated from an aqueous solution of transition metal ions and hydrogen peroxide
Implementation Method 3
hydroxyl radicals generated from an aqueous solution of transition metal ions and hydrogen peroxide
Implementation Method 4
pressure driven processes
Implementation Method 5
the pore size gradient across the membrane is not homogeneous, but rather varies in relation to the cross-sectional distance within the membrane
Data Source
AI summary
Hydrophilic porous polymeric membranes with high permeabilities, and processes for the preparation thereof are disclosed. Membranes may be prepared by including a preferably hydrophilic cross-linkable component such as PVP (either by inclusion into the polymer dope prior to casting, or coating or quenching cast membranes); and treating the polymeric microfiltration or ultrafiltration membrane with a crosslinking agent to cross-link said cross-linkable component. Preferred cross-linking agents include Fenton's reagent.