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