Atmospheric acid leaching of nickel laterites review. Part II. Chloride and bio-technologies

Most existing hydrometallurgical processes for the leaching of nickel laterites employ sulphuric acid. Alternative technologies that utilise other leaching agents such as hydrochloric acid and various organic acids are currently being examined and developed, and are the topics of this review.The first section examines the hydrochloric acid leaching of nickel laterites, focusing on the reactivity of limonitic and serpentine ores. The recovery of iron oxides from chloride systems is then briefly reviewed. The next section examines some recently developed non-conventional processes such as the Atmospheric Chloride Leaching Process (ACLP) and Intec Process using strong magnesium chloride liquors whilst the final section considers the use of citric and oxalic acids commonly produced by heterotrophic organisms.