Application of sulfation roasting leaching to the extraction of Ni from serpentine-rich ore

Abstract

The demand for nickel has been steadily increasing in the 21st century, primarily driven by the rising demand for electric vehicle batteries. Nickel in laterite associated within silicate in saprolite ore and hydroxide/oxide in limonite ore. Recently, the sulfation-roasting-leaching process has been developed to address the challenges of extracting nickel from laterite ores. It involves the formation of sulfates through the sulfation process using sulfuric acid and decomposition of iron sulfates in roasting process to produce SO3 gas to react with oxide and forms soluble nickel and cobalt sulfates for water leaching process. However most of the previous researches focus on limonite-type ore resulted in limited understanding on saprolite-type ore. In this study, sulfation-roasting-leaching process for nickel extraction from saprolite-type ore was investigated to observe the behavior of saprolite-type ore which rich in magnesium silicate under sulfation-roasting-leaching process. Experiments were conducted to obtain optimum condition to extract nickel and cobalt from saprolite-type ore. Various variable such as moisture, acid concentration, roasting temperature and time, pre-roasting temperature and time as well as leaching condition were investigated. The phase changes, mechanism and influence of other oxides/elements existed in original ore was also discussed. Results obtained in experiments show 70% Ni, 68% Co can be extracted under optimum condition. However, the presence of magnesium oxide in the ore posed a challenge, as it thermodynamically favored reacting with the SO3 gas instead of the nickel and cobalt oxides. Additionally, the presence of SiO2 originating from serpentine minerals affected the recovery of nickel and cobalt by adsorbing onto amorphous silica during the leaching process. These factors likely contributed to the lower recovery observed in the results of this study. Shrinking core model was applied to the results to determine rate of controing step in this process and to evaluate activation energy. The activation energy of Ni for roasting step was evaluated based on internal diffusion where it exhibited R2 value of 0.933 with 19.85 kJ/mol. While for the leaching step of Ni was evaluated based on film diffusion of shrinking sphere where it exhibited R2 value over 0.957 with 46.80 kJ/mol.