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Alternative Separations
Eli Gronowski CBE 562
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Overview Membranes Absorbents Ion-Exchange Resins
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Membranes Thin films of porous material
Polymer Films Ceramics Carbon Fiber Porous Metal Substrates Size: < 10 Angstroms to 100+microns
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Types of Membranes Microporous Membranes Homogeneous Membranes
Separate by pore diameter and particle size Homogeneous Membranes Dense film Separation by pressure, concentration or electrical potential gradient Separation of similar size particles
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Types of Membranes Asymmetric Membranes
very thin ( micron) skin layer on a highly porous ( microns) thick substructure Thin skin acts as the selective membrane
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Types of Membranes Electrically Charged Membranes Electrodialysis
ions are transported through a membrane from one solution to another under the influence of an electrical potential. production of potable water from sea or brackish water ED can be utilised to perform several general types of separations such as separation and concentration of salts, acids and bases from aqueous solutions or the separation and concentration of monovalent ions from multiple charged components or the separation of ionic compounds from uncharged molecules.
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Microfiltration membrane
Most widely used Sterile filtration Pores ( microns) Material can be selective Mechanical strength Temperature resistance Chemical compatibility Hydrophobility MF has a wide array of applications as mentioned below: Preparation of parenterals and sterile water for pharmaceutical industry Food & beverages (concentration of fruit juices and alcoholic beverages Chemical industry Microelectronics industry Fermentation Laboratory/analytical uses etc. Polyvinylidene difluoride
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Hydrophobic membranes
Resists water while simultaneously venting gases Materials Polytetrafluoroethylene (PTFE), nylon, glass fibers, polyethersulfone
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How Does It work Surface Tension Polarity Differences
Only liquids with surface energy lower than that of the membrane can wet out the membrane. Polarity Differences Nonpolar membranes tend to resist passage of polar compounds Polyvinylidene fluoride Two main principiles
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Applications Underwater flashlights Auto Industry
Vent hydrogen gas from Batteries Auto Industry Vent Heat / Gases Windshield wiper motors Halogen headlights
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Most Popular Applications
Hemodialysis Reverse osmosis Micro/Ultra Water Filtration In hemodialysis, blood flows through a semipermeable cellulose acetate membrane. This membrane separates proteins and cellular constituents in the blood from smaller molecular solutes. The solutes are then discharged from the apparatus allowing for pure blood to be generated back into the body.
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Membrane Industry
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Growth Fueled by Regulations for potable water/wastewater
Industrial recovery/recycling
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Benefits Separations Require Energy
Distillation Membranes typically require a lower amount of energy
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Reduction of Energy Costs
Replace Typical Units Ops Ethylene Production C2 Splitter
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Membrane Advantages Energy savings
Clean technology with operational ease Replaces the conventional processes Filtration Distillation Produces high quality products Greater flexibility in designing systems.
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Membrane Disadvantages
Membranes are expensive. Certain solvents can quickly and permanently destroy the membrane. Certain solids, especially graphite, can permanently foul the membrane surface.
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Absorbents MOLECULAR SIEVE crystallized synthetic zeolite
Selective, microporous adsorbent Premium catalyst and catalytic carrier Ion exchanger. Contains a network of uniform pores and empty cavities Zeolite is an inorganic porous material having a highly regular structure of pores and chambers that allows some molecules to pass through, and causes others to be either excluded, or broken down. It is in many ways, the inorganic equivalent of organic enzymes, many of which also have specific sized chambers that trap chemicals within our bodies, holding them where they either break down, or react with specific chemicals.
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Molecular Sieve
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Ethanol-Water System
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Ion Exchange Resin Water Softeners
Ion exchange resins are insoluble polymers that contain acidic or basic functional groups and have the ability to exchange counter-ions within aqueous solutions surrounding them
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Pharmaceutical Technology
Drug resinate more stable than original drug. Vitamin B12 (2 months vs 2 Years) Drug Abuse Control Reduce the “High” This technology is still used commercially today, more than 40 years after it was first introduced
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Future of Separations Advancements in Membrane Tech Chemical Industry
Better Materials Higher Selectivity, Stability, Throughput Chemical Industry Gas Separations Cryogenic distillation Selective adsorption
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References http://www.edmwt.com/membrane.htm
Using Hydrophobic Membranes to Protect Gas Sensors Clean Technologies and Environmental Policy. Berlin: Apr 2004. Vol. 6, Iss. 2; pg. 78 Pharmaceutical Technology. Cleveland: 2004. pg. 20, 5 pgs
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