The Direct Leaching of Nickel Sulfide Flotation Concentrates – A Historic and State-of-the-Art Review Part I: Piloted Processes and Commercial Operations

The extraction of nickel (Ni) from sulfide resources commences with flotation to produce a concentrate which is then smelted to produce a nickel-enriched phase called matte, and further refined to produce pure Ni products as well as by-products, such as cobalt (Co), copper (Cu) and precious metals. However, the traditional concentrate smelting-matte refining process, whilst technologically robust, is capital intensive and suffers from several environmental and technical issues such as sulfur dioxide emissions, poor recovery of cobalt and difficulty processing concentrates high in magnesia and arsenic without appropriate blending with high grade concentrates to dilute the concentration of these species. The direct hydrometallurgical processing of nickel sulfide concentrates and whole ores may be a remedy to these issues and hydrometallurgy offers several advantages over pyrometallurgy such as potentially lower capital costs, the ability to process lower grade materials and produce marketable metals or compounds directly from ore/concentrate. Despite the advantages of hydrometallurgy over traditional base metal sulfide smelting, the hydrometallurgical processing of nickel concentrates has been limited to a small handful of commercial operations, some of which only produce an upgraded intermediate for pyrometallurgical processing. In Part I of this three-part series, a comprehensive review of piloted processes for direct hydrometallurgical processing of nickel sulfide concentrates is presented, followed by a survey of industrial operations which have carried out direct leaching of nickel sulfide concentrates. A review of research activities and challenges/opportunities in the direct hydrometallurgical processing of nickel sulfide concentrates are presented in Part II and Part III of this series.