Synthesis of mesoporous silicon from industrial waste sodium-based slag

An increasing amount of waste sodium-based slag was generated during the purification process of metallurgical silicon that causes a posed problem to the environment. Here, a simple but effective approach was developed for the synthesis of mesoporous silicon from waste sodium-based slag. The as-received slag was leached and then calcined to fabricate silica as a precursor. Subsequently, the nanostructured silicon was produced through the reduction of the silica in a magnesium (Mg) vapor. The mechanism suggested that the Mg-containing phases (Mg2Si, MgSiO3, and MgO) were performed as an intermediary agent and facilitated the formation of nano-scale silicon. Nitrogen (N2) adsorption study of the final silicon product showed a BET surface area of 75.5 m2/g and a distributional BJH pore size of 3.7 nm. Significantly, the N2 absorption capacity of the mesoporous silicon reached 200 m3/g. The aim of this study is to recycle the waste sodium-based slag and provide an alternative for the synthesis of mesoporous silicon materials.