Thin-Film Composite Osmosis Membranes with Porous Support Additives
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Solution Overview
Problem
Current polymeric membranes used in osmotically driven membrane processes, such as forward osmosis and pressure-retarded osmosis, are not ideal due to suboptimal membrane characteristics like support layer porosity, thickness, and hydrophilicity, which affect water flux performance without sufficient salt rejection.
Innovation Solution
Customized thin-film composite membranes are developed with a porous support layer and a selective barrier, incorporating polymeric additives dispersed in the support layer, and fabricated using specific polymer solutions and casting methods to enhance porosity, hydrophilicity, and tortuosity, while maintaining water permeability and salt rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If polymeric membranes are used in osmotically driven membrane processes, then water flux is generated through osmotic pressure differential, but salt rejection is insufficient due to suboptimal membrane characteristics
Solution Approach 1:
The patent employs a porous support layer with optimized porosity (40-60%) and specific pore size distribution (0.01-10 μm) to enhance water flux while maintaining salt rejection. The porous structure allows efficient water transport through the membrane under osmotic driving force while the selective barrier prevents salt passage.
Solution Approach 2:
The patent uses a thin-film composite structure consisting of a porous support layer and a selective barrier layer. This composite design combines the high porosity and water permeability of the support layer with the high salt rejection capability of the selective barrier, achieving both high water flux and effective salt rejection simultaneously.
2Quantity of substance
If support layer porosity is increased to enhance water flux, then water permeability improves, but membrane structural stability deteriorates
Solution Approach 1:
The composite structure separates the functions of water transport and structural support. The porous support layer provides high water permeability through its optimized porosity (40-60%), while the selective barrier layer provides the necessary structural integrity and stability, allowing the membrane to withstand operating pressures without collapsing.
Solution Approach 2:
The patent optimizes specific parameters of the support layer including porosity (40-60%), thickness (10-100 μm), and pore size (0.01-10 μm) to achieve the right balance between water permeability and structural stability. These parameter optimizations allow high water flux while maintaining sufficient mechanical strength.
3Quantity of substance
If selective barrier thickness is decreased to improve water flux, then water permeability increases, but salt rejection performance deteriorates
Solution Approach 1:
The thin-film composite structure enables the selective barrier to be extremely thin (20-500 nm) while maintaining high salt rejection. The thin barrier provides low resistance to water transport under osmotic driving force, while the underlying porous support layer with optimized characteristics ensures sufficient structural support and additional salt rejection capability.
Solution Approach 2:
The membrane exhibits different properties at different locations: the selective barrier layer has high density and low porosity for excellent salt rejection, while the porous support layer has high porosity (40-60%) for high water permeability. This local differentiation of properties allows the thin barrier to achieve high water flux without sacrificing salt rejection.
4Quantity of substance
If polymeric additives are incorporated in the porous support, then hydrophilicity and porosity are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent modifies the chemical composition of the support layer by incorporating hydrophilic polymeric additives (5-50 wt%) to enhance hydrophilicity and water affinity. This parameter change in composition improves water flux without requiring complex manufacturing processes, as the additives are simply mixed into the polymer solution during membrane fabrication.
Solution Approach 2:
The polymeric additives are incorporated into the porous support structure to enhance hydrophilicity while maintaining the porous morphology. The additives modify the surface properties and internal pore characteristics of the support layer, improving water wettability and transport without compromising the porous structure essential for high water permeability.
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 customized membranes demonstrate improved water flux and salt rejection performance, suitable for applications like desalination, wastewater purification, and energy generation through osmotically driven processes.
Implementation Method 1
one or more polymeric additives dispersed in the porous support in an amount from about 1% and about 50% by weight of the porous support
Implementation Method 2
Osmotically driven membrane processes, such as forward osmosis (FO) and pressure-retarded osmosis (PRO), rely on large osmotic pressure differentials across semi-permeable membranes to generate water flux
Implementation Method 3
a selective barrier; and one or more polymeric additives dispersed in the porous support
Implementation Method 4
rely on large osmotic pressure differentials across semi-permeable membranes to generate water flux, while retaining solutes on either side of the semi-permeable membrane
Implementation Method 5
a method of fabricating a porous support comprising the steps of: preparing a polymer solution comprising a polymer, a polymeric additive, and a first liquid; contacting a surface with the polymer solution; and evaporating the liquid
Data Source
AI summary
One aspect of the invention relates to customized thin-film composite membranes comprising: a porous support; a selective barrier; and one or more polymeric additives dispersed in the porous support in an amount from at least about 1% and about 50% by weight of the porous support. Another aspect of the invention relates to a method of fabricating a porous support comprising the steps of: preparing a polymer solution comprising a polymer, a polymeric additive, and a first liquid; contacting a surface with the polymer solution; and evaporating the liquid. Another aspect of the invention relates to the use of the thin-film composite membranes disclosed herein in osmotically driven membrane processes.