Download Liquids Membranes

Liquid Membranes
Phase 2
Membrane
Phase 1
1
Types of LM

Volumetric or
Bulk (VLM)

Immobilised (ILM)
or Supported (SLM)

Emulsion (ELM)
Porous
support
liquid
Organic liquid
& surfactant
Receiving
phase
2
Facilitated Transport
A
Diffusive
transport
A
Facilitated A
transport
AC
A
3
Carrier Mediated Transport
Mobile Carrier
Mobile
10-5-10-7
Diffusivities (cm2/s)
Gel
10-6-10-8
Fixed Carrier
Fixed
>10-7
4
Types of FT…
A
Uncoupled
AC
Reaction
A+C<=>AC
A
A
AC
B
B
BC
A
Coupled
5
Coupled configurations
A
Counter
coupled
transport B
AC
B
BC
A
Reaction
A+CB<=>AC+B
A
Co-coupled
transport
AC
B
A
B
B
6
FT Mechanism
Source phase
M+
H+
LM
HC
MC
Strip phase
M+
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
7
FT: fast reaction case

Carrier-solute Complex reaction:
A  C  AC
Flux of solute A:
k
DAC  Kkc C A, f
DA k
JA 
C A, f 

L
L 1  KkCA, f
Flux due to
diffusion
k...distribution
coefficient



Flux due to
complexation
C A, 0
C A, f
K...equilibrium
constant
K
C AC ,0
C A8,0CC
Limiting cases
Diffusion
of the
complex
Total Flux
Fickean Flux
CA,0>>CAC,0
Fickean
diffusion
Intermediate
CAC,0>>CA,0
Region
2

Damkolher number

Dt 0.5
9
SLM Geometry
Planar
Flat
Hollow Fiber
Spiral wound
Laboratory
Industry
10
Comparing

Flat Sheet
Feed and strip solutions
mix directly and the
integrity of separation is
lost.
Can be fabricated easily
in the lab

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
11
SLM Problems
Solvent loss
evaporation
disolution
large Dp
Carrier loss
Irreversible
side reactions
Liquid flows
Solvent
condensation
12
Stabilization techniques
13
Classical Fields of Applications
 Facilitated
transport of gases
 Oxigen
 Carbon
Dioxide
 Carbon Monoxide
 Hydrogen Sulfide
 Olefins
 Nitric Oxide
 Sensor development
14
... more Applications
 Immobilized
 Metal
Liquid Membranes
ion separations
 Control
of heavy metals pollutants
 Recovery of: copper, uranium and cobalt
 Separation
 Acetic
of fermentation products
and citric acid
15
...and more
 Emulsion
Liquid Membranes
 Metal
ion extraction
 Amino acid extraction
 Removal of species without chemical carriers
16
Hollow fiber membrane-based enzymefacilitated separation
17
Purification using ELM
Inner Phase
Addition of LM
components
Recovered
components
of the LM
Emulsifier
Wastewater
Fresh emulsion
Emulsion reflux
Settler
Mixer
Inner
Phase
Purified
Water
18
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

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