COMPETITIVE ADSORPTION OF ORGANIC MATERIALS
BY ACTIVATED CARBON
Ju-Chang Huang, Professor
Department of Civil Engineering and Environmental Health
University of Missouri-Rolla
Rolla, Missouri 65401
Charles T. Steffens, Sanitary Engineer
Randolph & Associates, Inc.
Peoria, Illinois 61601
INTRODUCTION
Not too long ago, conventional secondary biological treatment was considered adequate by most municipal and industrial waste treatment plants in their water pollution
control programs.   However, recent establishments of certain stringent effluent and/or
water quality standards by both federal and state governments have suggested that the
use of secondary treatment alone will no longer be satisfactory for many of these plants.
This is because biological treatment processes are not highly effective in the removal of
many organic pollutants, particularly those of synthetic nature.   Therefore, more efficient
treatment means have to be employed either as a supplement or as a substitute for the
conventional treatment method.   One of the most promising methods for improving the
removal of organic pollutants is the use of activated carbon to adsorb and remove the
last quantities of organic matter from wastewaters.
Much of the past and present research in carbon adsorption has  been concerned with
either removing a single solute from its pure solution or removing a particular solute
from a solution of ill-defined chemical character.   Numerous other works have also been
dealing with the removal of gross organics, which are measured in terms of BOD or COD,
from wastewater.   However, it must be noted that treatment of wastewater by activated
carbon normally involves a multitude of adsorbates competing for adsorption sites on the
carbon surface.   Thus, a thorough understanding of the competitive effect of various organic compounds on the carbon adsorption would appear to be important.   Unfortunately, the amount of current knowledge about the competitive adsorption in aqueous
solution is quite meager.
Weber and Morris [ 1 ] have noted that in mixed solutions each solute competes in
some way with the other in both the rate and capacity of adsorption.   Weber [2] has
further observed in a column study that a solute tends to have a more rapid breakthrough in a mixed solution than in a pure solution due to the apparent effect of competitive adsorption.   Jain and Snoeyink [3] have recently investigated the quantitative effect
of competitive adsorption in some bisolute systems involving P-nitrophenol, P-bromo-
phenol and sodium benzenesulfonate.   They have found that the competitive adsorption
can be predicted by a modified model of the original Langmuir equation.   In view of the
facts that, on the one hand, competitive adsorption is important in determining the final
result of carbon adsorption but, on the other hand, little has been explored in this area,
it is obviously important to conduct further research in this particular subject.   The purposes of this study were, therefore, to evaluate:   (a) the relative rates and capacities of
adsorption among several selected homologous lower-chain fatty acids (aliphatic compounds) as well as some chemically related phenolic materials (aromatic compounds), and
(b) the phenomenon of competitive adsorption between the selected fatty acids and
phenolic substances.
107