Advanced Review on Extraction of Nickel

In this review, resources of nickel and status of different processes/technologies in vogue or being developed for extraction of nickel and associated metals from both primary and secondary resources are summarized. Nickel extraction from primary resources such as ores/minerals (sulfides, arsenides, silicates, and oxides) including the unconventional one viz., the polymetallic sea nodules, and various secondary resources has been examined. Though sulfide ores after concentration are generally treated by the pyrometallurgical route, most processes for lateritic ores deal with either the acid leaching at ambient temperature and pressure, or high pressure, and a few based on the microbial treatment and owing to the extensive research on laterites, a special emphasis is put forth in this review. Prominent sources that are covered in some detail include the solid wastes like spent batteries viz., end-of-life nickel-cadmium (NiCd) and nickel metal hydride (NiMH), spent catalysts, and spent/scrap superalloys, and liquid wastes such as copper bleed stream and electrowinning effluents. In particular pre-treatment of the spent nickel-based batteries, leaching of metals from the electrode materials in different lixiviants, besides separation/solvent extraction is discussed.