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