Nanosilica extraction from processed agricultural residue using green technology

Rice Husk Ash is a major voluminous and bulky by-product of rice-milling industries and its disposal is a major environmental concern. Considering this, a green technology was applied to obtain silica nano particles from Rice husk ash using sol-gel method. The solution of sodium silicate was prepared through hydrothermal activation of Rice husk ash instead of commercially available expensive and sometimes toxic raw materials. Further, the commercial production of silica requires high temperature up to 1300 degrees C, which makes the process energy and cost intensive. Structure, composition, morphology and size of synthesized silica powder were studied using by various techniques. X-ray Diffractometry analysis revealed broad peak of silica at diffraction angle of 22 degrees confirming its amorphous and non-crystalline nature. Fourier transform infrared spectroscopy results indicated the presence of silica oxygen bonding (- Si-O-Si-) at 796 cm(-1) and Si OH bonds (300-3500 cm(-1)). Scanning electron microscopy revealed the surface morphology of spheroid particles with little agglomeration and transmission electron microscopy gave a detailed view of internal morphology of particles interlinked with each other and of varying size in range of 10-30 nm. EDX analysis revealed presence of silicon and oxygen elements together comprising 99% by weight. Hence, proposed environmental-friendly method yielded nearly ultra-pure (98.9%) amorphous nano silica particles at lower temperature, which can be utilized in various industrial applications such as for the preparation of solar cells, nano medicine, cosmetics and filler in plastics and rubber. (C) 2016 Elsevier Ltd. All rights reserved.