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Title: Process for removing cadmium from scrap metal

A process for the recovery of a metal, in particular, cadmium contained in scrap, in a stable form. The process comprises the steps of mixing the cadmium-containing scrap with an ammonium carbonate solution, preferably at least a stoichiometric amount of ammonium carbonate, and/or free ammonia, and an oxidizing agent to form a first mixture so that the cadmium will react with the ammonium carbonate to form a water-soluble ammine complex; evaporating the first mixture so that ammine complex dissociates from the first mixture leaving carbonate ions to react with the cadmium and form a second mixture that includes cadmium carbonate; optionally adding water to the second mixture to form a third mixture; adjusting the pH of the third mixture to the acid range whereby the cadmium carbonate will dissolve; and adding at least a stoichiometric amount of sulfide, preferably in the form of hydrogen sulfide or an aqueous ammonium sulfide solution, to the third mixture to precipitate cadmium sulfide. This mixture of sulfide is then preferably digested by heating to facilitate precipitation of large particles of cadmium sulfide. The scrap may be divided by shredding or breaking up to expose additional surface area. Finally, the precipitated cadmium sulfide can bemore » mixed with glass formers and vitrified for permanent disposal.« less
  1. (Aiken, SC)
Issue Date:
OSTI Identifier:
United States of America as represented by United States (Washington, DC) SRS
Patent Number(s):
US 5405588
Contract Number:
Research Org:
Country of Publication:
United States
process; removing; cadmium; scrap; metal; recovery; particular; contained; stable; form; comprises; steps; mixing; cadmium-containing; ammonium; carbonate; solution; preferably; stoichiometric; amount; free; ammonia; oxidizing; agent; mixture; react; water-soluble; ammine; complex; evaporating; dissociates; leaving; optionally; adding; water; third; adjusting; ph; acid; range; whereby; dissolve; sulfide; hydrogen; aqueous; precipitate; digested; heating; facilitate; precipitation; particles; divided; shredding; breaking; expose; additional; surface; finally; precipitated; mixed; glass; formers; vitrified; permanent; disposal; stable form; optionally adding; glass former; permanent disposal; hydrogen sulfide; process comprises; cadmium sulfide; oxidizing agent; scrap metal; carbonate solution; glass formers; stoichiometric amount; adding water; removing cadmium; oxidizing agen; ammine complex; /423/106/