SYNTHESIS AND CHARACTERIZATION OF NANO-STRUCTURED SILICA FROM CORN COB BY SOL-GEL METHOD

Abstract

Extraction of amorphous silica from corn cob ash (CCA) was carried out by sol-gel method. Silica xerogel was produced by dissolving CCA with alkali solution to form sodium silicate solution. The pH was lowered to7.0 by the addition of hydrochloric acid to form silica aqua gel followed by drying to form silica xerogel. Silica and mineral contents of CCA and xerogel were determined by X-ray diffraction (XRD) and x-ray fluorescence (XRF). X-ray diffraction patterns revealed amorphous nature of extracted silica. Fourier transform infrared (FTIR) data indicated the presence of siloxane and silanol groups. Silica yield from CCA was 52.32% while moisture content was 2.89%. Extracted silica was nanostructured with templating concept which resulted in silica nanoparticle. X-ray diffraction (XRD) of nanostrurtured silica showed average particle size of 54 nm. SEM study indicates that the particles possess disordered morphology with the particles attached to each other through grain boundary to form agglomerated structure. Scanning Electron Microscope (SEM) spectral analyses using Scanning Probe Image Processor (SPIP 6.0.13) shown that particle size varied from 44-98 nm in diameter, with an average diameter of 55 nm. EDS spectrum reveals a strong intensity of Si. The nano-structured silica was used for the production of porous filter and applied in the filtration of contaminated water containing Bromothymol Blue. Adsorption isotherm studies using Langmuir isotherm, shows linearity with correlation = 0.9897, however there was deviation of the slope from unity.