A novel and efficient method for the synthesis of amorphous nanosilica from fly ash tiles

The present study reveals an efficient and cost-effective one-step method for the synthesis of nano-silica from silico-aluminous fly ash-based tiles. The fly ash and their products being rich in silica act as renewable source material for the synthesis of silica. A simple alkali fusion method developed to synthesize white amorphous nano silica directly from the fly ash-tiles by the acidic treatment which was analysed by UV–Vis, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD) and Field-Emission Scanning electron microscopy-electron diffraction spectroscopy (FESEM-EDS). The XRD revealed a broad hump from 2θ, 10–30° with a peak centered at 2θ = 21.7° confirms the formation of amorphous nanosilica. FTIR also reveals the characteristic bands of silica in the range of 400–1200 cm−1. While particle size analyser (PSA) confirmed the particle size distribution of nanosilica and FEMSEM confirmed the spherical shape and aggregated form of the synthesized nanosilica of size range varies from 10 to 60 nm. The prominent peak for Si and O confirmed the formation and purity of the nanosilica from the fly ash tiles. Around 99–100% of silicates were recovered by this method in the form of an insoluble precipitate. The developed method is an efficient and economical approach for the recovery of major fractions of silicates from the fly ash based tiles.