Nickel laterite processing and electrowinning practice

Nickel as cathodes, rounds, powders, and salts, is recognized as a useful substance in heavy industry. Today, only a few producers recover this important metal, which is employed worldwide in diverse commercial and residential applications. Nickel and associated metal values are traditionally recovered from ores by mineral processing, smelting and refining processes. Associated host minerals contain non-ferrous metals such as copper, cobalt, precious metals such as gold and silver, and the platinum group of metals. The future trend is expected to involve the processing of laterites, which account for about 70% of the world's nickel resources, by means of efficient pressure acid leaching and SX-EW facilities. Large quantities of laterites are found in Australia, Cuba, Indonesia, New Caledonia, and the Philippines. Laterites are easily mined by open pit methods whereas sulphidic ores generally involve more expensive underground mining. Cobalt, zinc, and copper are extracted from these sources as by-products. Modern automated plants for processing laterites feature state-of-the-art technology and environmental compliance. Production plants range in nameplate annual capacity from 10 to 50 thousand metric tonnes of nickel contained in the final product(s). On a worldwide basis the writers are aware of 12 nickel electrowinning refineries which produce class I nickel products. The paper describes the established industrial processes for nickel recovery by means of being electrowon from either an aqueous sulphate medium or chloride medium after initial leaching and solution purification techniques. Laterites are the main source of feedstock for production of ferronickel as described herein. The paper includes information regarding nickel-bearing deep sea nodules and secondary scrap processing to recover nickel values. For completeness, other extraction processes involving pellets from the carbonyl process, nickel powders, and briquettes are noted in the compendium of nickel processing practice which includes pyrometallurgical principles. The purpose of the review for nickel operating practice is to provide a complete extractive processing summary rather than the reader reviewing many authors. (C) 2002 Elsevier Science Ltd. All rights reserved.