Liquid Membranes

1
Liquid Membranes
Phase 2
Membrane
Phase 1
2
Types of LM

• Volumetric or Bulk (VLM)

• Immobilised (ILM) or Supported (SLM)

• Emulsion (ELM)

3
Facilitated Transport
Diffusive transport
Facilitated transport
4
Carrier Mediated Transport
Mobile Carrier
Fixed Carrier
Diffusivities (cm2/s)
Mobile
Gel
Fixed
10-5-10-7
10-6-10-8
gt10-7
5
Types of FT
Uncoupled
Reaction ACltgtAC
Coupled
6
Coupled configurations
Counter coupled transport
Reaction ACBltgtACB
Co-coupled transport
7
FT Mechanism
Source phase
LM
Strip phase
M
M
HC
MC
H
H
1) Carrier reacts with solute 2) The complexed
carrier diffuses across the membrane 3) Because
the adjacent solution is dilute, the solute
carrier reaction is reversed, releasing solute 4)
The carrier returns across the membrane
8
FT fast reaction case

• Carrier-solute Complex reaction

k...distribution coefficient
Flux of solute A
K...equilibrium constant
Flux due to diffusion
Flux due to complexation
9
Limiting cases
Diffusion of the complex
Total Flux
Fickean Flux
CA,0gtgtCAC,0
Intermediate Region
CAC,0gtgtCA,0
Fickean diffusion
Damkolher number
10
SLM Geometry
Planar Flat
Laboratory
Industry
Hollow Fiber
Spiral wound
11
Comparing

• Flat Sheet

• Hollow Fiber

Small leaks do not seriously affect the
performance If the membrane liquid is
contaminated, it can be easily be
replenished. The pressure drop in fibre bundles
is larger
Feed and strip solutions mix directly and the
integrity of separation is lost.
Can be fabricated easily in the lab
12
SLM Problems
evaporation disolution large Dp
Solvent loss
Irreversible side reactions Solvent condensation
Carrier loss
Liquid flows
13
Stabilization techniques
14
Classical Fields of Applications

• Facilitated transport of gases
• Oxigen
• Carbon Dioxide
• Carbon Monoxide
• Hydrogen Sulfide
• Olefins
• Nitric Oxide
• Sensor development

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... more Applications

• Immobilized Liquid Membranes
• Metal ion separations
• Control of heavy metals pollutants
• Recovery of copper, uranium and cobalt
• Separation of fermentation products
• Acetic and citric acid

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...and more

• Emulsion Liquid Membranes
• Metal ion extraction
• Amino acid extraction
• Removal of species without chemical carriers

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Hollow fiber membrane-based enzyme-facilitated
separation
18
Purification using ELM
Inner Phase
19
Balance of using LM

• Benefits
• High fluxes
• Very selective separations
• Ions can be concentrated
• Expensive extractants can be used
• Major Limitations
• Rupture
• Long term stability