Abstract: A two zone pyrolysis unit having a first drying zone and a second pyrolysis zone is provided for detoxifying heavy metals contained in sludges, soils and similar materials. A condenser and an afterburner are in flow communication with the first and second zones respectively.

Abstract: Heavy metals and compounds thereof and other toxic materials in industrial wastes, sludges, soils, incinerated ashes and the like are fixed and stabilized in a char residue, obtained by critical region pyrolyzing techniques and appropriate proportions of carbonaceous materials intimately mixed with the sludge, to encapsulate the heavy metals with carbon bonded thereto which effectively detoxifies the residue and renders it immune to any substantial leaching out or later exposure to the toxic metals, such that the same is environmentally safe for such uses as landfill and the like.

Abstract: Heavy metals and compounds thereof and other toxic materials in industrial wastes, sludges, soils, incinerated ashes and the like are fixed and stablized in a char residue, obtained by critical region pyrolyzing techniques and appropriate proportions of cabonaceous materials intimately mixed with the sludge, to encapsulate the heavy metals with carbon bonded thereto which effectively detoxifies the residue and renders it immune to any substantial leaching out or later exposure to the toxic metals, such that the same is environmentally safe for such uses as landfill and the like.

Abstract: A process is disclosed for incinerating tannery waste solids containing organic material and chromium which comprises burning at least one ton per day of said waste in the combustion zone of an industrial furnace at a low temperature, preferably between about 800.degree. F. and 1200.degree. F., to convert at least a portion of the organic material to gases and the chromium to ash, removing the gases from the combustion zone and subjecting them to further oxidation, and removing the ash from the furnace. The waste solids include sludge separated from liquid waste, leather scrap, or preferably both. By controlling temperature, waste composition, or both, the chromium in the ash can be obtained in either trivalent or hexavalent form. The hexavalent chromium can be extracted with solvent for reuse in the tanning process. Trivalent chromium, with or without carbon, can be recovered as chromic oxide in an improved stable form for landfill, storage or shipment to a reprocessing center.