1 liquid membranes membrane phase 1 phase 2. 2 types of lm immobilised (ilm) or supported (slm) ...
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Liquid Membranes
Membrane
Phase 1
Phase 2
2
Types of LM
Immobilised (ILM) or Supported (SLM)
Emulsion (ELM)Organic liquid & surfactant
Receiving phase
Porous support
liquid
Volumetric or Bulk (VLM)
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Facilitated TransportA
A
Facilitated transport
Diffusive transport
A
A
AC
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Carrier Mediated TransportMobile Carrier Fixed Carrier
10-5-10-7
Diffusivities (cm2/s)
10-6-10-8 >10-7
Mobile Gel Fixed
5
A
A
AC
BCB
B
Types of FT…
ReactionA+C<=>AC
Uncoupled A
A
AC
Coupled
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A
A
AC
BCB
B
Coupled configurations
AACA
BB
B
Counter coupled transport
ReactionA+CB<=>AC+B
Co-coupled transport
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FT Mechanism
M+
H+
M+HC
MC H+
Source phase LM Strip phase
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
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FT: fast reaction case Carrier-solute Complex reaction:
fA
fAACfA
AA KkC
CcKk
L
DC
L
kDJ
,
,, 1
Flux of solute A:
Flux due to diffusion
Flux due to complexation
ACCA
fA
A
CC
k,
0,
CA
AC
CC
CK
0,
0,
K...equilibrium constant
k...distribution coefficient
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Limiting cases
Fickean diffusion
Diffusion of the
complex
Total Flux
Fickean Flux
Damkolher number
Intermediate Region
5.0
2
Dt
CA,0>>CAC,0
CAC,0>>CA,0
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PlanarFlat
Laboratory
Hollow Fiber Industry
Spiral wound
SLM Geometry
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Comparing Flat Sheet Hollow Fiber
Feed and strip solutions mix directly and the integrity of separation is lost.
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
Can be fabricated easily in the lab
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Solvent loss
Carrier loss
Liquid flows
evaporationdisolutionlarge p
Irreversible side reactions
Solvent condensation
SLM Problems
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Stabilization techniques
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Classical Fields of Applications Facilitated transport of gases
OxigenCarbon DioxideCarbon MonoxideHydrogen SulfideOlefinsNitric OxideSensor development
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... more Applications
Immobilized Liquid MembranesMetal ion separations
Control of heavy metals pollutantsRecovery of: copper, uranium and cobalt
Separation of fermentation productsAcetic and citric acid
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...and more
Emulsion Liquid MembranesMetal ion extractionAmino acid extractionRemoval of species without chemical carriers
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Hollow fiber membrane-based enzyme-facilitated separation
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Emulsifier
Fresh emulsion
SettlerPurified Water
Mixer
Wastewater
Inner Phase
Recovered components
of the LM
Addition of LM components
Emulsion reflux
Inner PhasePurification using ELM
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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