TFC Membrane Flux via Oxidation-Reduction Treatment
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Solution Overview
Problem
Existing methods for enhancing water flux in thin film composite (TFC) membranes often compromise salt rejection characteristics or are costly, difficult to control, or damage the membrane, leading to transitory improvements.
Innovation Solution
A post-formation treatment process involving exposure of the polyamide discrimination layer to an oxidizing agent, followed by a reducing agent, specifically using concentrations of free chlorine and alkali metal meta-bisulfite, to enhance water flux while maintaining or improving salt rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TFC membranes are treated with chlorine or chlorine generating agents to enhance water flux, then water flux is improved, but salt rejection and stability are compromised
Solution Approach 1:
The patent applies parameter changes by controlling the concentration of oxidizing agent (5-50 ppm), pH (8-11), and exposure time (1-24 hours) to achieve flux enhancement while preserving membrane performance. The reducing agent concentration (0.1-5 wt%) and its application timing are also optimized to restore membrane properties without compromising flux improvements
Solution Approach 2:
The reducing agent acts as an intermediary that mediates between the oxidizing agent treatment and the membrane structure. It quenches residual oxidizing agents and restores membrane properties, enabling the oxidizing treatment to be applied without permanent damage to salt rejection characteristics
2Productivity
If higher concentrations of oxidizing agents are used to improve water flux, then flux enhancement is greater, but membrane damage and performance degradation increase
Solution Approach 1:
The reducing agent is applied in preliminary anti-action to counteract the harmful effects of the oxidizing agent before they can cause significant membrane damage. This preventive approach restores membrane properties after controlled oxidation, allowing flux enhancement without proportional membrane degradation
Solution Approach 2:
The patent optimizes the concentration parameters of both oxidizing and reducing agents to achieve the right balance. By controlling oxidizing agent concentration (5-50 ppm) and reducing agent concentration (0.1-5 wt%), the process achieves flux improvement while minimizing membrane damage through precise parameter management
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 process significantly increases water flux while retaining salt rejection properties, providing a stable and cost-effective solution for TFC membranes used in reverse osmosis, particularly effective for brackish water treatment at low energy conditions.
Implementation Method 1
contacting a polyamide discrimination layer of a TFC membrane with a solution containing an oxidizing agent
Implementation Method 2
contacting the treated membrane with a solution containing a reducing agent
Data Source
Figure 1A
Figure 1B
AI summary
Provided is a post-formation process for preparation of a highly permeable thin film composite membranes for reverse osmosis, particularly for use with brackish water at low energy conditions. The process includes contacting a polyamide discrimination layer of a TFC membrane with a solution containing an oxidizing agent to form a treated membrane, followed by contacting the treated membrane with a solution containing a reducing agent. The resulting membrane exhibits enhanced water flux while maintaining salt rejection. Also provided are reverse osmosis membranes prepared in accord with the method, and modules containing the highly permeable thin film composite membranes, and methods of purifying water using the membranes or modules.