The Caron Process for Nickel Laterites: A Critical Review of Recent Developments, Limitations, and Research Gaps

The Caron process is among the earliest hydrometallurgical technologies for processing nickel laterite, combining selective reduction roasting with ammoniacal leaching to recover nickel and cobalt. Although historically significant, the process has gradually lost industrial relevance due to high energy consumption, moderate recoveries, and competition from high-pressure acid leaching (HPAL) and atmospheric leaching. This critical review reassesses the Caron process based on literature published between 2020 and 2025, with emphasis on feedstock characteristics, reduction thermochemistry, ammoniacal leaching mechanisms, metal recovery efficiency, and environmental performance. Mineralogical constraints associated with iron-rich laterites, selectivity challenges during reduction, and reagent recycling limitations are systematically analyzed. Recent efforts involving process intensification, hybrid flowsheets, and low-carbon modifications, including alternative reducing agents and improved heat integration, are critically evaluated. A comparative assessment indicates that while the classical Caron process remains disadvantaged in terms of energy intensity and iron management, selected improvements may enhance its competitiveness for specific low-grade or high-iron laterites. The review identifies key research gaps and defines the technical, environmental, and economic conditions under which the Caron process could regain relevance in future sustainable nickel supply chains. Rather than positioning Caron as a universal alternative, this review defines its conditional and niche relevance.