63    LEAD AND OTHER HEAVY METAL FIXATION IN SOILS
AND SOLID WASTE BY THE MAECTITE® CHEMICAL
TREATMENT PROCESS
Karl W. Yost, Director of Treatment Services
Sevenson Environmental Services, Incorporated
Niagara Falls, New York 14302
Dhiraj Pal, Manager of Research and Development
Sevenson Environmental Services, Incorporated
Munster, Indiana 46321
S.A. Chisick, Senior Geologist
Sevenson Environmental Services, Incorporated
Munster, Indiana 46321
W.V. Jesernig, Engineer
W.V. Jesernig and Associates, Incorporated
Bolingbrook, Illinois 60440
INTRODUCTION
Waste stabilization/solidification (S/S) methods utilize the engineered concept of physical binding
mechanisms to encapsulate (micro and/or macro), entrap, absorb, contain, coat, or seal target analytes
within the waste matrix. These treatment methods physically immobilize heavy metals by surface effects,
plate polarity, hydration and/or adhesion principles to render waste characteristically non-hazardous
(Conner, 1985).' To confirm treatment, S/S treated material is exposed to geotechnical test criteria that
apply various physical forces or conditions to the treated mass. Failure is determined by the identification or quantification of fractures, permeability, strength, or defects. If failure occurs, physical immobilization binder mechanisms are also destroyed and new surfaces are created in the waste mass allowing
for release or direct attack of formerly immobilized metal species. Further, in the presence of acidity,
weakly absorbed metals may disassociate and readily diffuse to aqueous media or carrier fluid. The
alleged physically immobilized mixtures generate a problem that compromise long-term stability thereby
increasing inherent risk of future or current remediation costs.
While the current status of risk-free solid hazardous waste treatment for heavy metals is far from
optimal efficiency (i.e., 100% removal of the total metals from the waste), many inroads to a solution
have emerged. One approach is chemical treatment. With this technology, heavy metals are chemically
induced to nucleate forming crystals of mineral and mixed mineral forms. These minerals are microscopic, hard, geometrically dense, acid resistant, and will not degrade or fail under traditional
geotechnical and environmental forces that prevail in landfill or natural settings. The MAECTITE®
chemical process falls into the chemical treatment category.
MAECTITE® CHEMICAL PROCESS DISCUSSION
Leachable lead and other metals are chemically bound in hard and superhard mineral species that
are resistant to acid leaching such as those simulated during EP toxicity leach test, toxic characteristic
leaching procedure (TCLP), multiple extraction procedure (MEP) and other tests developed and
approved by USEPA. Two categories (Group I and II) of treatment chemicals are usually required in
variable amounts for the MAECTITE® chemical process to be effective in decreasing the TCLP lead
from thousands of mg/L to less than 1 mg/L in a diverse variety of waste media.
Treatment chemicals of Group I are in the main calcium (Ca) and/or magnesium based buffers,
salts and/or bases. Treatability studies are designed and executed to identify which additive of Group
I is most cost effective on a particular waste type. Treatment additives from Group I form insoluble
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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