2013 Buyers' Guide 2013 Buyers' Guide - Filtration News

Testing | GAED
GAED Determines Needed Adsorption
Energies in Activated Carbon Applications
By Henry Nowicki, Wayne Schuliger, George Nowicki and Barbara Sherman
Agood question for every
manufacturer and user of
physical adsorbents is what
sized adsorption spaces are used in
specific real-world applications This
article covers the answer to this important
question for a drinking water
plant using granular activated carbon
(GAC) to polish Lake Ontario water.
All activated carbons are not the same;
one size does not fit all applications.
They have different ranges of adsorption
spaces. Smaller nanometer sized
and shaped adsorption spaces hold adsorbate
molecules stronger than larger
Figure 1. Volume based Carbon Characteristic Curves - Cumulative
adsorption spaces. Most purchasers
buy activated carbons (AC) because it
provides physical adsorption of unwanted
molecules from water or air
streams passing through various forms
of AC. AC media comes in powder,
granular, pellet, block, fabric, composites
and chemical impregnations of
these forms. Gravimetric Adsorption
Energy Distribution or GAED has
been used on all forms of AC for both
aqueous- and vapor-phase applications.
The authors provide short
courses on AC.
Gravimetric Adsorption Energy Distribution
or GAED
is the best available
test method to answer
these questions:
What is the
best technical and
cost effective AC for
specific applications
and when should
one change-out the
used AC GAED
test method has its
roots in the early
1900’s largely due to Michael Polanyi.
He developed fundamental concepts
for heterogeneous physical adsorption,
which are utilized in the present day
GAED instrument and software. GAED
provides full characterizations for AC
and answers your questions for both
aqueous- and vapor-phase applications.
All one need to do to determine
what adsorption energies are consumed
in AC applications is to do GAED on
the starting unused sample and its used
sample. The starting test sample needs
to be representative of what was used
in the application. Comparison of the
initial and final GAED sample runs reveals
the adsorption spaces consumed
in the application. This information is
useful in improving your next AC purchase,
when to change-out the partially
used AC, and what options are for disposal
of the used AC. This case study
reported here is for two different virgin
GAC samples or unused and their corresponding
spent or used samples.
Mick Greenbank capitalized on
Polanyi’s potential adsorption energy
model to design and build instruments
Figure 2. Volume Based Differential Characteristic Curves
30 • August 2012 • www.filtnews.com