Chlorination Routes for Limonitic Nickel Laterites: A Critical Review of Solid-State and Gas-Phase Selective Volatilization

Chlorination has re-emerged as a strategic alternative for processing limonitic nickel laterites, providing selective conversion of Ni and Co into volatile or soluble chlorides under controlled thermal and chemical conditions. Compared to traditional hydrometallurgical and pyrometallurgical methods—such as HPAL, atmospheric leaching, Caron-type processes, and sulfation roasting—chlorination offers unique process windows where nickel and cobalt chlorides are highly stable and tend to volatilize, while iron remains mostly refractory as hematite or decomposes into ferric chloride. This comprehensive review consolidates recent advances in solid-state chlorination (using NaCl, CaCl₂, and NH₄Cl), gas-phase chlorination (Cl₂, HCl, and Cl₂/CO mixtures), and emerging chlorohydrometallurgical systems employing ionic liquids and deep eutectic solvents. Special focus is given to (i) The reaction pathways controlling chlorination and volatilization of Ni/Co from goethite–hematite matrices, (ii) The kinetic and mass transfer limitations in mixed-laterite systems, (iii) The effects of mineralogical factors like silica, serpentine, and chromite on chloride conversion, and (iv) Opportunities for integrating processes to recover critical elements such as Sc, Ti, and REEs. The review also assesses the technology readiness, environmental impacts, chloride-circuit regeneration, corrosion challenges, and energy demands compared to established commercial processes. Overall, the synthesis underscores chlorination as a technically promising but underdeveloped pathway, with industrial application depending on advances in reactor design, recycling of chlorinating agents, materials suitability, and multi-metal recovery methods.