Environmental Engineering Reference
In-Depth Information
Process
Concept
Driving force
Species passed
Species retained
Fee
d
Ret
entate
Microfiltration (MF)
Pressure difference
Solvent (water)
Suspended solids, fine
100-500 kPa
and dissolved solutes
particulars, some colloids
Solvent
Microporous membrane
Fee
d
Ret
entate
Ultrafiltration (UF)
Pressure difference
Solvent (water) and
Macrosolutes and colloids
100-800 kPa
low molecular weight
solutes (
<
1000)
Solvent
UF membrane
Ret
entate
Fee
d
Nanofiltration (NF)
Pressure difference
Solvent (water), low
High molecular weight
0.3-3 MPa
molecular weight solutes, compounds (100-1000),
monovalent ions
multivalent ions
Permeate
NF membrane
Fee
d
Ret
entate
Reverse osmosis (RO)
Pressure difference
Solvent (water)
Virtually all dissolved
1-10 MPa
and suspended solids
Permeate
RO membrane
Concentrate
Product
Electrodialysis (ED)
Electric potential
Solutes (ions)
Non-ionic and
difference 1-2 V/cell
Small quantity of solvent
macromolecular species
−
−
pair
+
−
Feed
Ion-exchange membrane
Purified
str
eam
Fee
d
Dialysis (D)
Concentration difference Solute (ions and low Dissolved and suspended
molecular weight organics) solids with molecular
Small quantity of solvent
weight larger than 1000
Impurities
Dialysate
feed
Dialysis membrane
Re
tentate
Fee
d
Gas permeation (GS)
Pressure difference
High permeable
Less permeable
0.1-10 MPa
gases and vapours
gases and vapours
Permeate
Dense/Porous membrane
Fee
d
Re
tentate
Pervaporation (PV)
Chemical potential or
High permeable
Less permeable
Liquid
concentration difference
solute or solvents
solute or solvents
Vapour
Permeate
Dense membrane
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