A Quick Method For Evaluating the Suitability of Activated Carbon Adsorption For Wastewaters

To day, the activated Carbon is being
used to treat the industrial and domestic
wastewaters. The suitability of
activated carbon for treatment of industrial
wastewaters can be quickly predicted
by consideration of wastewater
characteristics. The results of this
paper represent a first step in determining
suitability of activated carbon
for treatment of wastewaters or effluent
of treatment plants containing carboxyl,
hydroxyl, and amine functional
groups as a function of aromaticity ,
molecular size, and PH.
Relative adsorbability of uncharged
suLstituted groups to activated carbon
followed the order : Acids>Ampiline>Phenol,
and for aliphatic organics in the
uncharged state followed the order:
Acids Alcohols)Amines. Since these
groups of aromatic and aliphatic compounds
were in the same molecular weight
range. The respective order of uncharged
organics compound up take is:
Aromatic Acids>aliphatic acids and Alcohols>
Aniline aliphaticAmines>Phenol.
The degree of adsorption was dependent
on organic solubility and acid dissociation
constant. Adsorbality increased
as solubility decreased and when the
organic compound was in an uncharged
state. Solubility decreased with increasing
carbon length which tended to
decrease functional group influence.
The importance of the number of functional
groups per molecule on solubility
and sorbability was demonstrated from
the results of the acidic polymer
(polymethylacrylic) and amine polymer
(polyethylenimine) studies:
organics containing carboxyl groups
adsorbed better in their uncharged state
(usually in acidic solutions). The
respective carbon adsorption in acidic
and basic environments followed the
order: Benzoic Acid (H )Valeric Acid
(H )polymethylacriylic Acid(H ),propionic
Acid (H )Valeric Acid (OH-)Benzoic
Acid (OH )propionic Acid (OH )
polymethlacrylic Acid (OH ).
Organic substituted with hydroxyl
groups demonstrated little affect in
adsorption with changing PH (with the
exception of Pentanol). Respective relative
adsorbability to activated carbon
follow the sequence:
Phentanol(H )Phenol(OH and H )Penta-
nol (OH )>Propanol (H and OH ).
organics substituted with amine
groups adsorbed better in the uncharged
state at PH values above thier PKa,
(usually in basic solution).
Respective adsorbability of these compounds
in acidic and basic environments
follow the sequence: Aniline (OH )Po1yethylenimine
(OH )>Pentylamine (OH )>
Nony1anmine (H )>Hepthylamine (H )>Pyridine
(OH ) >Aniline (H )>Polyethylenimine
(H ) >pyridine (H ) .
On the basis of this experiment, it
is recommended that four wastewater
characteristics to be investigated to
predict euitability of activated carbon
for wastewater treatment. These characterictics
are as follows: measurement
of total organic carbon, acidity ,organic
nitrogen and aromatic compounds .The
application of these organic wastewater
characteristics can aid in predicting
suitability of activated carbon for
wastewater treatment and answerd to
various questions about the design of
treatment plant.