The use of a macroporous char for treatment and disposal of mixed wastes

The ChemChar process was employed on mixed wastes to destroy organic materials, and retain the inorganic materials for long-term disposal, using environmentally beneficial chemical and thermal processes. Actinide metals were included in the study. Because the ChemChar process is based on gasification, a thermally reductive process, it reduces or entirely avoids many environmental problems found in related waste treatment processes such as incineration which involve oxidative reactions that form SO_x and NO_x gases and other toxic products of incomplete combustion such as polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF). The final products of the ChemChar gasification process are CO₂, a mixture of combustible gases (H₂, CO, trace amounts of CH₄) and a dry, nonreactive, char solid. The char matrix will retain the inorganics, acid gases as well as any ash. These products can be converted by cementation or vitrification to a safe, nonleachable form suitable for disposal.; The retention of metals, such as the actinides, in a vitrified matrix produced by gasification of a macroporous char, called Triple Reverse Burn (TRB) char, will reduce the storage volume compared to the original waste material. Assorted leachability studies of cemented, vitrified and char waste forms were conducted to quantify the behaviors of uranium, thorium, protactinium, neptunium, cerium, cobalt, cesium, cadmium, strontium, zinc, mercury and chromium directly. In addition to the leachability aspects of the waste forms, the compressive characteristics of stress and strain for the cemented waste form were analyzed.; Overall, results found that greater than 90% of the metals were retained on the TRB char during reverse mode gasification and, in most cases, less than 1% of the metals were able to escape the ChemChar gasification. Leachability of post-gasified chars varied widely depending on the leachant. The unconfined compressive strength of cylindrical cemented waste forms was optimized to approximately 3870 pounds per square inch.; The U.S. Department of Energy Radiochemistry Education Advancement Program DE-FC09-93SR18262 (Coop #135), the Seaborg Institute for Transactinium Science, Los Alamos National Laboratories, the University of Missouri-Columbia, Department of Chemistry and ChemChar Research, Incorporated provided financial support for this research.