Comparative Assessment of the Yields of Silica from Husk Ashes of Digitaria exilis (acha), wheat and rice

Abstract

The isolation of amorphous silica from acha husk ash (AHA), wheat husk ash (WHA) and rice husk ash (RHA) was carried out in this work. The different husk ashes were obtained by the calcination of the respective husks in a muffle furnace at 500 o C for five hours. Silica was extracted as sodium silicate from the respective ashes using NaOH solution. A solution of HCl was added to the sodium silicate to lower the pH to 7.0 to produce silica aquagels which were subsequently dried to give silica xerogels. The mineral contents of the xerogels, AHA, WHA and RHA were determined by energy dispersive x-ray fluorescence spectroscopy (ED-XRF, Model PW 4025/45B). The percentage of silica in the AHA, WHA and RHA were (57.50±1.10)%, (59.68±1.10)% and (68.50±0.20)% respectively, while the silica content of the respective xerogels were (92.03±0.82)%, (88.43±2.13)% and (88.55±0.20)%. The results distinguish AHA as an effective alternative source of silica, having the highest yield with minimal mineral contaminants.