Impregnated-Alkaline Roasting for Tailoring Nanoporous Silica from Ferronickel Slag Waste

This research outlines the potency of ferronickel slag (FS) in the recycling process for the ferronickel industry, primarily for silica raw material provision, preventing detrimental effects of FS accumulation, and supporting the circular economy. The amorphous and high content of precipitated silica (PS) was successfully produced from the FS, which has complex phases. The decomposition process at a low temperature was carried out to liberate the complex phases and to form water-soluble sodium silicate, that subsequently was separated by water leaching and precipitated as silica. This study discovered that sodium silicate could be formed by reacting FS with NaOH in the impregnation-roasting processes. It was then separated by water leaching with the optimum process condition at a temperature of 90 °C, leaching time for 60 min, and a solid-to-liquid ratio of 1/6 g/ml. Nanoporous silica that contains 95.74% of SiO₂ was generated. The series process contributes to liberating silica from complex phases of ferronickel slag for further applications and accelerates the extraction efficiency of Si by 85.58% compared to the previous study.