THE EFFECTS OF CHLORINE ON THE PROPERTIES AND
PERFORMANCE OF ACTIVATED CARBON
Walter J. Weber, Jr., Professor
College of Engineering
The University of Michigan
Ann Arbor, Michigan 48109
James D. Sherrill, Project Manager
Massoud Pirbazari, Engineer
Environmental Dynamics, Inc.
Ann Arbor, Michigan 48104
INTRODUCTION
This chapter details results from an investigation of potential effects of high concentrations of avadable chlorine compounds (HOC1 and OC1") and chlorate (C103") on activated carbon adsorption systems. The study relates to direct treatment of industrial waste
streams containing these compounds, as well as to industrial discharges of such materials
to municipal facdities which incorporate activated carbon treatment.
Activated carbon is frequently used for dechlorination of waters and wastewaters.
That contact of HOC1/OC." with carbon wdl result in chemical reduction of these compounds is well known. It is therefore conceivable that sufficiently high concentrations of
HOC1/OC1" might ultimately cause oxidative degradation of carbon and/or impair its adsorptive functions. Although the rates and extent of removal of HOCl/OCf by carbon
have been elaborated in some detad [ 1 ] there is little quantitative information available
with respect to concentrations of these oxidizing agents that can be tolerated without
adverse effects on the carbon.
The behavior of C103", which has a higher thermodynamic oxidation potential than
HOC1/OC1", is even less weU known. The oxidation potential of C103~ is not effectively
exercised in ddute aqueous systems because of high associated activation energies, and
thus insignificant rates of reaction. However, the possibUity for surface catalysis of the
reduction of C103" by activated carbon-a recognized catalyst for many oxidation/
reduction reactions-has not been explored in this context.
In view of the increasing significance of activated carbon in industrial and municipal
wastewater treatment and the lack of information regarding potential interactions with
the aforementioned chlorine compounds, the present study was designed and executed to
develop a data base upon which to assess the effects, if any, of selected concentrations of
these compounds on the physical and chemical properties of activated carbon, and on its
function as an adsorbent. The concentrations selected for study exceed those that might
be anticipated for most treatment situations, and therefore represent a conservative
boundary condition for evaluating whether adverse effects are manifest by the presence
of HOC1/OC1" and/or C103" in activated carbon treatment systems.
SCOPE AND EXPERIMENTAL DETAIL
It is generally recognized that the adsorptive characteristics and physical properties of
an activated carbon wdl change as a function of successive exhaustions and regenerations,
the extent of change being determined in large measure by the type of carbon, the waste
stream being treated, and the conditions of regeneration. The investigations described in
this chapter were designed to evaluate whether HOC1/OC." and/or C103", even in very
large concentrations, have statistically significant effects on the rates and extent of such
changes.
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