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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 19