Chemical Engineering May 2023 - 26

Cover Story
Introduction to
Activated Carbon
Understanding the different types of activated carbon products, their specific properties and
best practices for use is essential to the design of effective environmental treatment processes
Martin O'Brien,
Rebecca
DiStefano and
Andrew Harris
Calgon Carbon Corp.
A
IN BRIEF
HOW ACTIVATED
CARBON IS MADE
HOW ACTIVATED
CARBON IS USED
LIQUID-PHASE BEST
PRACTICES
VAPOR-PHASE BEST
PRACTICES
SPENT MEDIA AND
REACTIVATION
SYSTEM DESIGN AND
SCAELUP
SAFETY
industrial
ctivated carbon is a type of manufactured
carbon material used for
a range of adsorptive processes,
including drinking water treatment,
operations,
environmental
remediation
and many other applications. Reports
suggest that crude activated carbons have
been used in various ways for millennia, for
example by ancient Egyptians and Romans as
medicine or for water filtration, but the science
of more effective modern activated carbons
has been continuously developing over many
decades. Today's activated carbon products
include cutting-edge manufactured materials
that are crucial to society's water and energy
infrastructure, as well as modern industry. Activated
carbon provides an environmental solution
for ensuring clean air and drinking water
and contributes to the efficient production of
many industrial products. Understanding the
different types of activated carbon products,
their specific properties, and best practices
for use is important to the design of effective
treatment processes.
Activated carbon is ubiquitous because it is
a versatile adsorbent material with the ability
to separate and retain components of many
liquids and gases (Figure 1). Within an activated
carbon particle, the immense specific
surface area facilitates the physical adsorption
of molecules onto the carbon surface. In contrast
to absorption, where fluids enter the internal
area of a material, causing it to expand,
adsorption is a phenomenon that describes
how molecules physically adhere to a surface.
Physical adsorption onto activated carbon
occurs through weak intermolecular forces
called Van der Waals forces in the internal
surface area of carbon, often called the pores
of the carbon, which give activated carbon
its exceptional ability to adsorb and retain organic
compounds. Activated carbon adsorption
is non-specific and the adsorbate properties
contribute to practical capacity for a given
contaminant. The adsorption strength of a
compound onto activated carbon increases
with molecular weight and aromaticity, and
can be influenced by functional groups. This
adsorptive capability allows activated carbon
to be utilized in a wide range of separation
processes. Some common factors that affect
adsorption are detailed in Table 1.
How activated carbon is made
Activated carbon is manufactured by carbonizing
a carbon-rich material and then generating
new internal surface area in a process
called activation. The type of activation process
used and the selected raw materials will
produce finished activated-carbon products
with different properties.
There are two types of activation processes
used to generate internal surface area: physical
activation, which uses a high-temperature
gas, such as H2O or
CO2,
to
react
with
FIGURE 1. Activated carbon is used in treatment processes when manufacturing a wide variety
of industrial products, as well as in environmental treatment for water, air and more
26
carbon to increase
surface area; or
chemical activation,
which produces surface
area by reaction
of carbon sources
with an added chemical,
such as HP3O4.
Physical activation
with H2O vapor is the
most common activation
process practiced
industrially, but
chemical activation is
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