Membranes - Principles of Chemical Separations with Environmental Applications - page 236

Equipment required to produce required high pressures for some applications can be
extremely noisy.

9.4 Environmental applications

Though still a relatively new commercial process in comparison with other technologies in
this text, membrane separation processes should increase in applications in the future. In
the near term, air and water treatment applications probably represent the best opportunities
for membranes - though there are important additional environmental applications. Below
is a list of various membrane processes and their environmental applications.
Gas separations
Carbon-dioxide removal from various gas streams.
Acid-gas (CO 2 ,H 2 S) separation from natural gas.
Drying of gas streams. One important example is dehydration of natural gas. Eliminates
use of solvents for this application.
Removal of organic compounds from vent streams. Recovery of ethylene and propy-
lene from vent streams from polyethylene and polypropylene pellet storage is one
commercial example.
Reverse osmosis (RO) and nanofiltration (NF)
Reduction of chemical oxygen demand (COD) of wastewater and groundwater streams.
Color removal from wastewater streams.
Removal of various ions from wastewater streams.
Clean-up of wastewaters from electroplating baths, landfill leachates and laundry
effluents.
Concentration of spent sulfite liquor from paper-plant effluents.
Recovery of homogeneous catalysts.
Ultrafiltration (UF)
Concentration of latex particles in water and recovery of latex particles from wastewaters
(painting processes, for example).
Removal of polymer constituents from wastewaters.
Separation of oil-water emulsions.
Microfiltration (MF)
Separation of oil-water emulsions.
Removal of precipitated metal hydroxides.
Removal of micron-size particles from a wide variety of liquid streams.
Concentration of fine solids.
Pervaporation
Removal of small amounts of water from organic solutions, e.g., water from isopropanol.
Removal of small amounts of organics from water, e.g., in wastewater clean-up.
Separate liquid-phase solutions that form an azeotrope. Replaces azeotropic distillation
which eliminates use of solvents.