Adsorption - Principles of Chemical Separations with Environmental Applications - page 187

Table 7.1 Adsorbent types [1]. Reproduced with permission of the American Institute of
Chemical Engineers. Copyright c 1988, AIChE. All rights reserved.

Adsorbent Characteristics Commercial uses Strengths Weaknesses

Activated carbon Hydrophobic

surface, favors
organics over air
or water

Removal of
organic pollutants
from aqueous and
gaseous effluents

Cheapest
hydrophobic
adsorbent,
workhorse of the
pollution-control
business

Difficult to
regenerate if
fouling occurs,
sometimes can
catch fire during
regeneration

Carbon molecular
sieves

Separates on the
basis of different
intra-particle
diffusivities

Production of N 2
from air

The only practical
adsorbent favoring
O 2 adsorption
over N 2

Has not found any
uses except for air
separation

Silica gel High-capacity,

hydrophilic
adsorbent

Primarily drying
of gas streams,
sometimes used
for hydrocarbon
removal from
gases

Higher capacity
than zeolite
molecular sieves
(zms)

Not as effective as
zms in removing
traces of H 2 O
from gases

Activated alumina High-capacity

hydrophilic
adsorbent

Primarily drying
of gas streams

Higher capacity
than zms

Not as effective as
zms in removing
traces of H 2 O
from gases

Zeolite molecular
sieves (zms)

Hydrophilic
surface; polar,
regular chemicals

Dehydration, air
separation,
geometry-based
separations, many
others

Can make
separations based
both on polarity
and geometry

Lower total
capacity than
many other
adsorbents

Silicalite Hydrophobic

surface;
adsorption
characteristics
similar to those of
activated carbon

Removal of
organics from gas
streams

Can be burned off
more easily than
activated carbon

More costly than
activated carbon

Polymer
adsorbents

Usually styrene Removal of

organics from gas
streams

Not as subject to
fouling as
activated carbon

Much more costly
than activated
carbon

Irreversible
adsorbents

Surfaces that react
selectively with
components of gas
streams

Removal of low
levels of H 2 S,
SO 2 , etc., from
gases

Excellent in
removing trace
contaminates

Only economical
for removal of
<

day of
adsorbents

100 kg /

Biosorbents Activated sludge

on a porous
support

Removal of
organics from gas
streams

No regeneration
needed

Percent removals
often lower than
for other
adsorbents