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10

Gas-Phase Activated Carbon Adsorption

Lawrence K. Wang, Jerry R. Taricska,
Yung-Tse Hung, and Kathleen Hung Li

CONTENTS
INTRODUCTION AND DEFINITIONS
ADSORPTION THEORY
CARBON ADSORPTION PRETREATMENT
DESIGN AND OPERATION
DESIGN EXAMPLES
NOMENCLATURE
REFERENCES

1. INTRODUCTION AND DEFINITIONS

1.1. Adsorption
The phenomenon by which molecules of a fluid adhere to the surface of a solid is
known as adsorption. Through this process, these solids or adsorbents can be selective-
ly captured or removed from an airstream, gases, liquids, or solids, even at very small
concentrations. The material being adsorbed is called the adsorbate and the adsorption
system is called the adsorber (1–12).
A fluid’s composition will change when it comes into contact with an adsorbent and
when one or more components in the fluid are adsorbed by the adsorbent. The adsorption
mechanism is complex. At all solid interfaces, adsorption can occur, but it is usually
small unless the solid is highly porous and possesses fine capillaries. For a solid adsorbent
to be effective, it should possess the following characteristics: large surface-to-volume
ratio and a preferential affinity for the individual component of concern.
Adsorption can occur in a specific manner. It can be used effectively to separate
gases from gases, solids from liquid, ions from liquid, and dissolved gases from liquid.
For example, after a release of toxic gases such as sulfur dioxide and chlorine into a
room at a wastewater-treatment plant, an adsorption unit can be used to remove the
gases from air. Additionally, adsorption can be used to remove colloids or suspended
solids from the liquids, as in decolorizing and clarifying a liquid. Adsorption is also
used to improve the taste and odor of drinking water by removing dissolved gases
from the water.

From: Handbook of Environmental Engineering, Volume 1: Air Pollution Control Engineering
Edited by: L. K. Wang, N. C. Pereira, and Y.-T. Hung © Humana Press Inc., Totowa, NJ
395