TFC Membrane Backside Treatment for Water Flux
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Solution Overview
Problem
Thin film composite (TFC) membranes used for water purification in reverse osmosis and nanofiltration face a reduction in water flux due to drying and coating processes, which can lead to fouling and pore collapse, especially under brackish conditions, and are prone to osmotic blister formation.
Innovation Solution
Treating the backside of TFC membranes with a pore structure protection agent, such as a tertiary amine salt of camphorsulfonic acid, before drying and coating to preserve membrane performance and prevent osmotic blisters, thereby maintaining or enhancing water flux and salt rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the TFC membrane is dried and coated to improve durability and protection, then the membrane structure is stabilized, but water flux is reduced due to pore collapse
Solution Approach 1:
A pore structure protection agent is applied to the membrane before the drying and coating processes. This preliminary action prevents pore collapse during subsequent processing, thereby maintaining water flux while still allowing the membrane to be dried and coated for durability.
Solution Approach 2:
The pore structure protection agent acts as an intermediary substance that temporarily maintains the pore structure during critical processing steps. This intermediary protects the membrane pores from collapse while the membrane undergoes drying and coating, enabling both durability improvement and flux preservation.
2Reliability
If conventional drying and coating processes are applied to improve membrane protection, then durability is enhanced, but osmotic blister formation occurs
Solution Approach 1:
The pore structure protection agent is applied in advance to counteract the harmful effect of osmotic blister formation. By establishing protective action before the drying and coating processes begin, the agent prevents blisters from forming during subsequent processing while still allowing the membrane to be protected.
3Productivity
If the membrane is treated to maintain pore structure, then water flux is improved, but additional processing steps are required
Solution Approach 1:
The pore structure protection agent application is combined with the existing rinsing step in the membrane manufacturing process. By integrating the flux enhancement treatment into the existing process flow rather than adding a completely separate step, the water flux is improved while minimizing the increase in processing 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 process significantly improves water flux and maintains salt rejection, with moderate to large improvements observed in sea water and brackish water membranes, respectively, while avoiding osmotic blister formation and reducing operational pressures.
Implementation Method 1
treating the backside of TFC membranes with a pore structure protection agent, such as a tertiary amine salt of camphorsulfonic acid, before drying and coating to preserve membrane performance
Implementation Method 2
it is capable, under a suitable applied pressure, of preferentially permeating water and rejecting dissolved salts
Data Source
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AI summary
Provided is a process for preparation of a highly permeable thin film composite membranes for nanofiltration, reverse osmosis, and forward osmosis, particularly for reverse osmosis of brackish water. The process includes treating a prepared TFC membrane containing a discrimination layer on a frontside, a support layer, and a felt layer on the backside by contacting the backside of TFC membrane with a solution containing a pore protection agent that includes a tertiary amine salt of camphorsulfonic acid prior to or at the same time as contacting the frontside of the membrane with a solution containing a coating agent and drying the membrane. Also provided are reverse osmosis membranes prepared in accord with the method, and modules containing the highly permeable thin film composite membranes.