Innovative methodology for comprehensive utilization of saprolite laterite ore: Recovery of metal-doped nickel ferrite and magnesium hydroxide

• A new process for comprehensive utilization of saprolite laterite ore was developed.
• Selective extraction of Ni and Fe from laterite ore was investigated.
• RFe/Ni plays an important role in the preparation of single-phase spinel ferrite.
• Metal-doped NiFe2O4 and Mg(OH)2 were obtained.

A new hydrometallurgical process was developed to synthesize metal-doped nickel ferrite (NiFe2O4) and magnesium hydroxide (Mg(OH)2) from saprolite laterite ore. Selective extraction of Ni and Fe with a controlled Fe-to-Ni mole ratio (RFe/Ni) from saprolite laterite ore was investigated. It is shown that the leaching efficiencies of Ni and Fe were approximately 85.0% and 17.0% with an RFe/Ni of 2.6 after hydrothermal leaching at 200 °C with a liquid-to-solid ratio of 6:1 mL·g− 1 and HCl solution concentration of 2 mol·L− 1. After the leaching process, the hydrothermal coprecipitation method (200 °C, 2 h) was adopted to separate Ni, Co, Fe, Mn and Al from Mg ions in the leaching solution by controlling the initial pH value of 7.0. Under optimal conditions, metal-doped NiFe2O4 magnetic material with a cubic spinel structure was successfully synthesized directly from the precipitate; meanwhile, Mg(OH)2 (96.8 wt.%) was obtained from the filtrate. Moreover, it is estimated that 96.95 g of metal-doped NiFe2O4 and 278.6 g of Mg(OH)2 could be produced from 1000 g of processed saprolite laterite ore.