47    SORPTION OF SELECTED ORGANIC POLLUTANTS
BY FLY ASH
Kashi Banerjee, Research Assistant
P. Y. Horng, Graduate Assistant
Paul N. Cheremisinoff, Professor
M. S. Sheih, Post-Doctoral Student
S. L. Cheng, Professor
Department of Civil & Environmental Engineering
New Jersey Institute of Technology
Newark, New Jersey 07102
INTRODUCTION
Power plants that burn fossil fuels generate large quantities of solid residues/by-product materials.
Annual production of this by-product material in the United States is nearly 75 million tons.1 A large
portion of the mineral matter, present in coal, is transformed into the residual by-products during the
carbonization process. These by-products include slag, bottom ash and fly ash. At present, there are
very few commercial uses of fly ash. Therefore, a need exists for an inexpensive management technology for environmentally safe disposal or storage until such uses are developed. Uncontrolled release
of the hazardous wastes into the environment causes severe problems. This can be avoided by the
destruction of the wastes or irreversible transformation to non-hazardous forms. Wastes for which
neither destruction nor transformation is currently practical, immobilization/isolation is often a
suitable control strategy.
Studies have indicated that some clay soils can be used as liners to retard the mobility of hazardous
leachate from landfill because of their low permeability, or can be used as a sorbent material to adsorb
the pollutants from the waste stream.2'3'4'5 Because of their dynamic and heterogenous nature, the
clay soils have the property of reacting with certain anions and cations and retaining these in an
exchangeable state. By these reactions, the clay soils may serve as a medium for either waste storage or
for ultimate waste disposal. With these backgrounds, many investigators have shown that leachate
and waste streams containing organics, pesticides, herbicides, heavy metals, can be attenuated by clay
soils and thermal power plant's by-products (fly ash). Some research has explored the application of
^lyj^L ;n t^ittinfi aratiamifr Nelson and Guarino6 reported that fly ash can be used to remove
appreciable ^jjantitie&ciLCOD and BOD. Ballance et al.7 used fly ash as a coagulant aid in water
TxeaTmeTuT reporting that fly ash has certain properties which enhances chemical coagulation and
setting of turbid water. Chan et al.8 reported that a combination of acidic and basic sorbents (illite/
flyash/zeolite) is most efficient for the removal of heavy metals^ and fluoride ions from petroleum
sludge leachate.
This study affords possibilities in techniques of waste immobilization utilizing a by-product of
combustion, as well as an opportunity to study the adsorption process.
MATERIALS AND METHODS
Fly ash was used as sorbent material throughout the study. This is a fine particulate matter, sandy
material, dark gray in color, usually collected by the electrostatic precipitator from the flue gas before
it escapes from the stack. The principal chemical constituents are silica, alumina, iron, sulfur dioxide,
alkali and alkaline earth metals. The constituents of flyash vary according to the type of coal used and
the degree of combustion.
43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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