Screening and reduction roasting of limonitic laterite and ammonia-carbonate leaching of nickel–cobalt to produce a high-grade iron concentrate

• Laterite screened to remove silicates and subjected to roasting and ammonia leaching.
• High-grade iron concentrates (Fe > 60%) can be directly produced for ironmaking.
• Extractions of Ni and Co can be improved under the identical optimal conditions.
• Thermodynamic analysis of the reduction roasting process was discussed.
• Phase transformation of the improved reduction roasting process was clarified.

This study focuses on the comprehensive utilization of a limonitic laterite from the Philippines. The ore was screened to remove some silicate minerals and then treated via reduction roasting-ammonia leaching. The optimal conditions of reduction roasting of screened ore (Ore I) were determined through a series of tests. Compared with the extractions of nickel and cobalt from the initial ore, those from Ore I increased from 84.0% to 87.9% and from 35.5% to 47.4%, respectively. The iron in leach residue increased from 56.2% to 60.7% without any further treatment, and the final recovery of iron was up to 85.2%. The improved reduction roasting process was analyzed to illustrate the phase transformations of iron, nickel, and cobalt, as well as the effects of such behaviors on the recoveries of these metals.

Producing iron concentrate in nickel–cobalt extraction form a limonitic laterite by reduction roasting–ammonia leaching.Figure optionsDownload as PowerPoint slide