Synthesis and Characterisation of Nano-silica Based on Pumice Using NaOH


Nano-silica was synthesised from pumice by extraction method using sodium hydroxide (NaOH), sulphuric acid (H2SO4) and hydrochloric acid (HCl). The raw material of pumice was collected from local area, Tanggamus-Lampung Indonesia. After grinding, the pumice powder was activated at 450°C for 2 h before mixing with NaOH for extraction. After extraction, the powder was heated at 800°C for 4 h, to maintain the silica is in amorphous phase. Physical characteristics were analysed using transmission electron microscopy (TEM) for measuring particle size, Brunauer-Emmett-Teller (BET) technique for surface area measurement, x-ray diffraction (XRD) for structure and x-ray fluorescence (XRF) for determination of oxides. XRD analysis proved that besides amorphous nano-silica, there are peaks of sodium sulfate (Na2SO4) as representation of crystalline structure. The maximum silicon dioxide (SiO2) content was found on 3.0 molar (M) NaOH. The highest surface area of 165 m2/g was obtained in sample of 3.5 M NaOH. The truly amorphous nano-silica content was found in NaOH of 3.0 M. The formation temperature may occur between 1100°C–1200°C. The particle size is in the range of 9 nm–17 nm.