Mechanism of Nickel, Magnesium, and Iron Recovery from Olivine Bearing Ore during Leaching with Hydrochloric Acid Including a Carbonation Pre-Treatment

Abstract

This work continues on from previous studies showing that mineral sequestration by carbonation of magnesium or calcium silicates under high pressure and high temperature can be successfully carried out by processing in an autoclave. The paper is focused on the influence of experimental parameters on avoiding scale formation during pre-treatment in an autoclave and a subsequent leaching. Amorphous silica and magnesite, respectively, were the main reaction products in a carbonation of olivine under high pressure conditions in an autoclave. In addition, the examined peridotites may be accompanied by small to medium amounts of nickel or other metals, the recovery of which will be investigated in the present study: Extraction of metals such as nickel, iron, and magnesium from olivine bearing ore using hydrochloric acid under atmospheric pressure was studied between 50 and 90 °C in 1 h. The obtained results have shown maximal leaching efficiency of about 35% for Ni, Fe, and Mg under atmospheric pressure, in comparison to more than 60% obtained under the same conditions after a carbonation pre-treatment in an autoclave. Silica gel was formed during leaching without a pre-treatment of peridotite blocking the leaching process, which is not the case for the pre-treated material. The influence of temperature, reaction time, particle size and pre-treatment of peridotite in an autoclave during carbonation at 175 °C and 71.5 bar was studied. A new mechanism model for metal extraction from olivine-bearing ore by avoiding silica gel formation during leaching with hydrochloric acid including a carbonation pre-treatment is proposed. This study explains additionally a behavior of metals such as nickel, magnesium, and iron during a carbonation of olivine bearing ore and leaching of a carbonated solid product.