Alkaline Hydrothermal Treatment and Leaching Kinetics of Silicon from Laterite Nickel Ore

Abstract

A new process of extracting silica from laterite nickel ore by hydrothermal treatment with sodium hydroxide as reaction auxiliary agent was proposed. The mineralogical transformation and silicon extraction kinetics of laterite nickel ore in alkaline hydrothermal treatment were studied. The effects of reaction temperature (175 ~ 250℃), molar ratios of sodium hydroxide to ore (1.05 ~ 1.2:1), and laterite nickel ore particle size (44 ~ 178 μm) on the extraction ratio of silica were investigated by using the shrinking core model. The results show that the extraction ratio of silica increases with the increase of reaction temperature, sodium hydroxide to ore molar ratio, reaction time, and the decrease of raw ore particle size. The kinetic analysis shows that the separation of silica in laterite ore can be described by internal diffusion model. The apparent activation energy (E a ) of the reaction was 8.87 kJ mol −1 , and the kinetic modeling was established. KeywordsLaterite nickel ore • Sodium hydroxide • Hydrothermal • Silica • Kinetics Abbreviations C HCl Concentration of hydrochloric acid standard solution (mol/mL) V a Volume of hydrochloric acid consumed in titration (mL) V c Volume of hydrochloric acid consumed in the blank test (mL) C NaOH Concentration of the standard solution of sodium hydroxide (mol/mL) V b Volume of sodium hydroxide consumed in titration (mL) V d Volume of sodium hydroxide consumed in blank test (mL) V Total volume of the solution (L) v Volume of the solution taken (mL) m Mass of silica in the sample (g) k d Diffusion rate constant (min −1 ) k r Reaction rate constant (min −1 ) A Frequency factor (s −1 ) E a Apparent reaction activation energy (J mol −1 ) R Molar gas constant (J/mol K) T Thermodynamic temperature (K) α Extraction rate of SiO 2 (%) d 2 Square of the initial diameter of the raw ore (µm −2 ) XRD X-ray diffraction SEM Scanning electron microscopy EDS Energy disperse spectroscopy XRF X-ray fluorescence * Longjiao Chang

The future nickel metal supply for lithium-ion batteries

“…126 Recently, novel methods such as selective reduction followed by magnetic separation have gained extensive research interests, which are expected to lower the reduction temperature and improve the efficiency of pyrometallurgical process. 127 In the hydrometallurgical process, sulfuric acid, hydrochloric acid or ammonia solution are employed as leaching agents to leaching nickel and cobalt metal ions from the laterite nickel ore. 128 Hydrometallurgy technology is applied to process limonitic ore, which includes high-pressure acid leaching (HPAL), atmospheric acid leaching (AL), and ammonia leaching (Caron process). 128 Although the hydrometallurgical process has the merits of high recovery rates and low impurities, it still suffers from the following shortcomings including high pressure and temperature of HPAL process, high acid consumption of AL process and low metal recovery of Caron process.…”

“…127 In the hydrometallurgical process, sulfuric acid, hydrochloric acid or ammonia solution are employed as leaching agents to leaching nickel and cobalt metal ions from the laterite nickel ore. 128 Hydrometallurgy technology is applied to process limonitic ore, which includes high-pressure acid leaching (HPAL), atmospheric acid leaching (AL), and ammonia leaching (Caron process). 128 Although the hydrometallurgical process has the merits of high recovery rates and low impurities, it still suffers from the following shortcomings including high pressure and temperature of HPAL process, high acid consumption of AL process and low metal recovery of Caron process. Certainly, some new technologies such as chlori- nation/sulfation/alkali leaching processes, microwave heating and bioleaching have also emerged in the extraction of laterite nickel ore. 129 Meanwhile, much efforts are still needed to explore environmentally friendly and economic technology for the extraction of nickel ores.…”