New insights into method development and characterization of amorphous silica from wheat straw

Abstract Amorphous silica is extensively extracted from agricultural residues. Wheat straws are a rich source of silica that have earlier been overlooked however demand for value addition. The proposed study describes an innovative approach for extracting silica from wheat straw and evaluating its structural, textural, and physico-chemical characteristics. Optimum temperature, concentration and pH were identified for the cleaner production of silica. The crystallographic properties analysed by the X-Ray diffraction revealed amorphous nature of silica extracted from ash at 650°C for 4h. The structure of phytolith present in the wheat straw was observed in the form of articulated elongate undulate epidermal phytolith under scanning electron microscope. The energy dispersive X-ray spectrum exhibited higher amount of silica (Si %) of 70.10% with a minimal percentage of potassium (9.96%). The sharp bend at 1025 cm -1 attributed the siloxane (Si-O-Si) vibrations in Fourier transform infrared spectroscopic graph of amorphous silica. The specific surface area measurements of amorphous silica showed type II isotherm curve with a hysteresis of H3 type. The optimum conditions to obtain amorphous silica were 3M NaOH, 3M H 2 SO 4 and pH 9.