چكيده به لاتين
Nanosilica exhibits a high porosity and specific surface area, and could be widely used in various industrial applications such as insulation, fillers, rubber, etc. Reusing and recycling industrial wastes as affordable and available precursors could efficiently help the environment. The main purpose of this study is to use the foundry slag as a source of silica for synthesis of nanosilica through a facile and environmentally friendly method. The proposed method includes hydrochloric acid dissolution of the slag, washing, and gelation stages. The experimental results showed that a dissolution efficiency of around 75±3% could be achieved at liquid-to-solid (L/S) ratio of 15 ml/g, dissolution time of 1 h, dissolution temperature of 80 °C, and acid concentration of 2 M. Also, the efficiency of silica extraction was about 82%. It is shown that the proposed process is compatible with the principles 1, 2, 3, 4, 6, 8, 11, 12 of green chemistry. The obtained silica was characterized by X-ray diffractometry (XRD), X-ray fluorescence (XRF) spectroscopy, field emission scanning electron microscope (FESEM), and nitrogen sorptometry. The characterization results indicated that the obtained silica has a high purity of more than 99% and a high specific surface area of 658 m2/g. The FESEM images of the silica revealed agglomerates of nanometricparticles of 30-50 nanometer. The solid residue at the end of the silica extraction process was also characterized. The characterization results showed that the solid residue is MgAl2O4 spinel with a purity of more than 97%. The FESEM clearly disclosed octagonal particles larger than 1 µm. Overall, the proposed process suggests a promising waste valorization way to convert almost 100% of the foundry slag into valuable and widely-used materials.
