Leaching residue of nickeliferous laterites as a source of iron concentrate

Abstract

The lateritic nickeliferous iron ore deposits of Central and Northern Greece (Euboea, Locris, Boeotia and Kastoria) provide the feed material for the production of an iron-nickel alloy at a pyrometallurgical plant located in Larymna. Due to the low quality of feed ore, about 0.90–1.00% nickel, the metallurgical processing cost is high and the quantity of the slag produced and disposed amounts to millions of tonnes yearly. During the past 20 years, the Laboratory of Metallurgy of NTUA has been developing a novel method of hydrometallurgical processing of laterites, based on heap leaching of the ore with dilute sulphuric acid. Nickel is recovered from the pregnant leach liquor by solvent extraction and electrowinning. The solid leach residue is a material consisting mainly of hematite, quartz and chromite. The present research is an investigation on upgrading of this residue to a saleable iron concentrate. The upgrading, if proved successful, will potentially relieve the environment from the disposal of such a large quantity of slag, which today is produced by pyrometallurgical processing of laterites. The accomplishment of this target faces problems related mainly to the fine dissemination and interweaving of mineralogical phases and the present work is focused on addressing the associated mineralogical issues.