Extraction and Recovery of Pure Nickel Metal From Hazardous Plating Sludge

Sludge waste from many plating operations is classified as a hazardous waste. Its disposal is a major environmental concern. In this proposal, the nickel values in sludge that result from electroless nickel plating and from chromium plating will be extracted and recovered as pure nickel metal. The sludge first will be converted into a purified nickel carbonate using an innovative combination of pyrometallurgical, hydrometallurgical, and mineral processing techniques. The sludge cannot be converted directly to a metallurgically usable product because of the relatively high concentration of metallic and nonmetallic impurities it contains. Climax Research Services' proposed innovative recovery procedure removes these impurities from the sludge waste and ultimately generates a purified nickel oxide. The purified nickel oxide then is reduced to form nickel metal powder. This powder can be used in nickel-metal hydride batteries for electrical power generation, or it can be briquetted and used in the nonferrous metal foundry industry. Solid wastes generated throughout the processing will be converted in an environmentally acceptable manner into a vitrified product. The composition of the pure metal will meet the American Society for Testing and Materials (ASTM) specification for pure nickel metal.