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vironmental
Adsorption,
2.4 En Ion Exchange, and Catalysis 47
Applications of
• heavy-metal removal in clay barriers
• i.e. remo ery of nutrients v v al and reco nitrogen and phosphorus removal from wastewater,
• solvent recovery and solvent v apor fractionation
• volatile organic compounds recoery from gas streams and groundw v ater
• water removal from gas streams containing acid gases

Other important applications of adsorption are the control of “greenhouse” gases (CO,
CH 4 ,N 2 O), the utilization of CH 4 , the flue gas treatment (SO x ,N O x , Hg remo and the al), v
v recoery of the ozone-depleting CFCs (Dabro 2001). Actiated carbons and
wski,
v
hydrophobic zeolites are used for the adsorption of HCFCs (Tsai, 2002).
The most commonly used adsorbents are shown in Table 2.7. The adsorption process
can be used for substance recoery as well as for the abatement of undesirable emissions v
in wwaters (Table 2.8) and gas streams (Table 2.9). aste

Table 2.7
The most common adsorbents
Wastewater treatment VOC removal

Activated carbon (mainly as granulates) Granular activated carbon
Lignite cok e Zeolites
Activated aluminum oxide Macroporous polymer particles
Adsorber resins Silica gel
Zeolites Sodium–aluminum silicates

Table 2.8
Representative commercial liquid-phase adsorption separations

Liquid bulk separations Adsorbent
(adsorbate concentration in the feed 10% wt.)
Fructose/glucose Zeolites
p -Xylene/ o -xylene, m -xylene Zeolites
Detergent-range olefins/paraffins Zeolites
Normal paraffins/isoparaffins, aromatics Zeolites
p -Diethyl benzene/isomer mixture Zeolites
Liquid Purif ications Adsorbent
(adsorbate concentration in the feed 3% wt.)
Sulfur compounds/or ganics Zeolites
Organics/H O Activated carbon
2
Odor, taste/drinking H O Activated carbon
2
H O/organics Silica, alumina, zeolite
2
Decolorizing petroleum fractions, sugar syrups,
vegetable oils, etc. Activated carbon