Environmental Engineering Reference
In-Depth Information
Table 2.3 Some examples of separation processes using other than conventional fields to
facilitate separation [2]. Reproduced with permission of the American Institute of
Chemical Engineers. Copyright 1987 AIChE. All rights reserved.
Process
Uses
Centrifugation
Separation of finely divided solids from liquids.
Separation of liquid-liquid dispersions.
Gaseous separation of isotopes.
Electrophoresis
Separation of charged macromolecules.
Separation of mixtures of simple cations or anions.
Electrodialysis
Desalting of brackish water.
Concentration of seawater.
Electrostatic separation
Removal of particulates from air and gas streams.
Concentration and separation of various ores.
Electrosorption
Desalination.
High-gradient magnetic separation
Elective separation of weakly magnetic materials.
Separation of inorganic-sulfur-containing particles
from coal.
Field flow fractionation
Separation of particles by size in a shear field.
energy-separating agent, used in distillation. External fields, such as magnetic and elec-
tric, are sometimes used as energy-separating agents.
A different component distribution between two phases is obtained. This distribution
change can be accomplished in two ways:
1 Alteration of the original phase equilibrium. Two phases are originally present and
the role of the separating agent is to change the composition in each phase relative to
the initial values.
Examples:
Mass-separating agent : one approach would be the addition of a selective com-
plexing agent to a liquid phase to increase the solubility of a solute. An example
would be the addition of a selective chelating agent to an organic phase which can
complex with a metal ion in an aqueous phase when the two phases are contacted.
Energy-separating agent : heat input to change the temperature of a gas/liquid
system. The most common example is distillation.
2 Generation of a second phase with a different component distribution.
Examples:
Mass-separating agent : solid sorbent which is selective for a solute in a feed stream.
An example would be the removal of VOCs from an air stream using activated
carbon.
Energy-separating agent : heat input to a liquid phase to change the solute solubility
in that phase. An example would be evaporation to remove water from a waste
stream and concentrate it prior to disposal.
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