Synthesis of mesoporous silica MCM-41 using sodium silicate derived from copper ore tailings with an alkaline molted-salt method

•A green approach was developed to synthesize mesoporous silica MCM-41 from the copper ore tailings.•The alkaline molten-salt method was taken to effectively extract silicon from the tailings at low temperature.•The obtained MCM-41 had a typical hexagonal mesoporous structure and a high BET specific surface area of 946.68m2/g.•Hematite was kept stable in the alkaline molten-salt system, thus avoiding ferruginous impurity of MCM-41 product. The alkaline molten-salt method was taken to effectively extract silicon from the copper ore tailings at 500–600°C. The extraction rate of SiO2 and Fe2O3 was ca. 82% and below 2%, respectively. Hematite was not converted to soluble NaFeO2 in low temperature NaOH–NaNO3 molten system. Mesoporous MCM-41 was synthesized using a hydrothermal method with the extracted Na2SiO3. The analysis of small angle XRD, N2 adsorption–desorption and HRTEM showed that the silica sample had a regular hexagonal structure of typical mesoporous MCM-41. The obtained MCM-41 silica had a BET specific surface area of 946.68m2/g and mesopore volume of 0.76cm3/g.