37    REMOVAL OF HYDROPHOBIC ORGANIC COMPOUNDS
FROM WASTES CONTAINING NATURAL ORGANIC
AND INORGANIC MATTER
Ahmad I. Jamrah, Assistant Professor
Department of Civil Engineering and Construction
Bradley University
Peoria, Illinois 61625
Steven K. Dentel, Associate Professor
Department of Civil Engineering
University of Delaware
Newark, Delaware 19716
INTRODUCTION
Traditional activated carbon adsorption processes1,2 for the removal of the organic pollutants are
often impaired due to substantial adsorptive interference by the NOM. It has been documented3-5 that
severe reductions in the adsorption capacity of activated carbon for the targeted micropollutants
occur as a result of this interference. Further, these interference effects are cumulative over time.
Recent research has suggested that chemically modified clays represent a promising new group of
adsorbents that may circumvent the non-selectivity drawbacks associated with activated carbon. The
chemical modification utilizes charge and structural characteristics of clays to allow synthesis of an
adsorbent capable of preferential uptake of contaminants.
Clays generally possess a negative charge due to isomorphic substitution in the tetrahedral and
octahedral layers of the mineral. In the case of montmorillonite, the tetravalent Si in the tetrahedral
sheet may be partly replaced by trivalent Al, while there might be a replacement of the trivalent Al in
the octahedral sheet by divalent Mg without complete filling of the third vacant octahedral position.
The surplus of the negative charge is usually compensated for by the adsorption of cations such as
Na+ and Ca + 2. In aqueous environments, these cations can be exchanged easily due to their tendency
to form soluble hydroxides, which, combined with the presence of Si-O groups at the mineral surface,
grants hydrophilic properties to the clay surface. Poor adsorption of hydrophobic organic compounds
results, due to the competition of the more polar water molecules for adsorption sites at the mineral
surface.6
MATERIALS AND METHODS
ADSORPTIVES
Tannic acid
This material was used in the experiments as a laboratory surrogate for natural organics present in
natural waters which are competing adsorbates. The tannic acid used in the experiments was supplied
by Sigma Chemical Company, and reported to have a mean molecular mass of 1700.
The use of tannic acid in the experiments was favored because it contains both saccharide and
aromatic acid components that are significant in surface waters.7,8
1,2,4-Trichlorobenzene (TCB)
This is a synthetic organic compound and one of the EPA priority pollutants. Maximum Contaminant Level (MCL) and Maximum Contaminant Level Goal (MCLG) were set to 0.07 mg/L for TCB in
the fourth phase of Safe Drinking Water Act regulations.9 TCB may be considered as representative
of halogenated organic water pollutants and disinfection by-products that have been detected in
groundwater'0 and in surface waters.3
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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