Abstract: The process of the present invention destroys cyanide, especially that associated with spent aluminum potliners, by reacting, in a preferred embodiment the crushed potliners with an effective amount of a mixture made from a chloride salt and bleach in cyanide destroying conditions. The chloride salty preferably is calcium chloride. The bleach is calcium or sodium hypochlorite. The reaction mixture generally also includes calcium carbonate as a source of carbon dioxide to accelerate the reaction rate.

Abstract: Electric arc furnace production of recycled steel is plagued by the formation of an iron-depleted, metal-rich electric arc flue dust (EAFD). In the present invention, we recover at least about 85 wt. % of the base metals in the EAFD (i.e., lead, cadmium, copper, and zinc) as high quality metals products without producing any solid, liquid, of gaseous wastes. We use a recyclable calcium chloride/hydrochloric acid leach mill solution to extract the base metals from the EAFD in a reactor under a controlled pH of about 2.6 at an elevated temperature and pressure in an oxygen environment wherein the solids content in the reaction slurry is about 15-30 wt. %. In this way, we place the base metals in solution while leaving the iron as a solid hematite iron complex. When separated from the metal-rich solution, the solid hematite iron complex is recycled to the electric arc furnace. The base metals are precipitated and recovered.

Abstract: We recover chlorine-free zinc solids in substantially 100% yield from a solution of base metals extracted from electric arc flue dust (EAFD) by reacting a zinc chloride solution formed after leaching metals from the EAFD with a calcium reactant at an elevated temperature and pressure under an inert atmosphere to produce the chlorine-free zinc precipitate and a calcium chloride solution for recycle to the EAFD reactor. We generally use about 90-110% of the theoretical stoichiometric amount of calcium hydroxide (hydrate of lime) to reduce the amount of calcium in the solid zinc. The metastasis process at the elevated temperature and pressure at which we perform it produces both ZnO and Zn(OH)2, so that the recovered solid has a Zn composition of at least about 55-65 wt. % with less than 1.0 wt. % Cl.

Abstract: The method of the present invention detoxifies spent aluminum potliners to remove hazardous cyanides, fluorides, and polynuclear aromatics by reacting crushed potliners with a CaCl2/HCl leach mill solution in the presence of iron. The method produces a solid waste suitable for landfill disposal and a recyclable reaction liquor. The reaction to destroy the polynuclear aromatics preferably occurs at a pH of no more than about 0.2, at about 120° C. and 80 psig following destruction of the cyanides and converting of the fluorides to florspar in an initial oxidation at a lower temperature, lower pressure, and higher pH.

Abstract: Electric arc furnace production of recycled steel is plagued by the formation of an iron-depleted, metal-rich electric arc flue dust (EAFD). In the present invention, we recover at least about 85 wt. % of the base metals in the EAFD (i.e., lead, cadmium, copper, and zinc) as high quality metals products without producing any solid, liquid, of gaseous wastes. We use a recyclable calcium chloride/hydrochloric acid leach mill solution to extract the base metals form the EAFD in a reactor under a controlled pH of about 2.6 at an elevated temperature and pressure in an oxygen environment wherein the solids content in the reaction slurry is about 15-30 wt. %. In this way, we place the base metals in solution while leaving the iron as a solid hematite iron complex. When separated from the metal-rich solution, the solid hematite iron complex is recycled to the electric arc furnace. The base metals are precipitated and recovered.

Abstract: Metal values are separated from arsenic sulfide ores in a hydrometallurgical oxidation process using a balanced reactant slurry. The molar concentration of As and Sb in the reactant slurry is controlled with respect to the molar concentration of Cu, Pb, and Zn in the slurry so that, upon reacting, soluble arsenic compounds or toxic arsenic vapors are not formed.