Alternative Separations
Eli GronowskiCBE 562
Overview Membranes Absorbents Ion-Exchange Resins
Membranes Thin films of porous material
Polymer Films Ceramics Carbon Fiber Porous Metal Substrates
Size: < 10 Angstroms to 100+microns
Types of Membranes Microporous 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
Types of Membranes Asymmetric Membranes
very thin (0.1-1.0 micron) skin layer on a highly porous (100-200 microns) thick substructure
Thin skin acts as the selective membrane
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
Microfiltration membrane
Polyvinylidene difluoride
Most widely used Sterile filtration
Pores (0.1-10.0 microns) Material can be selective
Mechanical strength Temperature resistance Chemical compatibility Hydrophobility
Hydrophobic membranes Resists water while simultaneously
venting gases Materials
Polytetrafluoroethylene (PTFE), nylon, glass fibers, polyethersulfone
How Does It work
Surface Tension• 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
Applications Underwater flashlights
Vent hydrogen gas from Batteries Auto Industry
Vent Heat / Gases• Windshield wiper motors• Halogen headlights
Most Popular Applications Hemodialysis Reverse
osmosis Micro/Ultra
Water Filtration
Membrane Industry
Growth Fueled by
Regulations for potable water/wastewater
Industrial recovery/recycling
Benefits Separations Require Energy
Distillation Membranes typically require a lower
amount of energy
Reduction of Energy Costs Replace Typical Units Ops Ethylene Production
C2 Splitter
Membrane Advantages Energy savings Clean technology with operational ease Replaces the conventional processes
Filtration Distillation
Produces high quality products Greater flexibility in designing systems.
Membrane Disadvantages Membranes are expensive. Certain solvents can quickly and
permanently destroy the membrane. Certain solids, especially graphite, can
permanently foul the membrane surface.
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
Molecular Sieve
Ethanol-Water System
Ion Exchange Resin Water Softeners
Pharmaceutical Technology Drug resinate more stable than
original drug. Vitamin B12 (2 months vs 2 Years)
Drug Abuse Control Reduce the “High”
Future of Separations Advancements in Membrane Tech
Better Materials• Higher Selectivity, Stability, Throughput
Chemical Industry Gas Separations
• Cryogenic distillation• Selective adsorption
References http://www.edmwt.com/membrane.htm Using Hydrophobic Membranes
to Protect Gas Sensors http://www.sensorsmag.com/articles/0598/gas0598/main.shtml
Clean Technologies and Environmental Policy. Berlin: Apr 2004. Vol. 6, Iss. 2; pg. 78 Pharmaceutical Technology. Cleveland: 2004. pg. 20, 5 pgs http://www.njit.edu/alumni/pdf/BeertoBlood.pdf http://www.tifac.org.in/news/memb.htm
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