Utilization of Pure Silica Extracted from Rice Husk and FTIR Structural Analysis of the Prepared Glasses

Abstract

Egyptian rice husk was subjected to different chemical and thermal treatment methods, aiming to extract high pure silica. Three samples (S1, S2 and S3) were prepared applying three different chemical treatment methods. Two sets of the obtained samples were prepared, where the first set was calcinated at 600oC and the other set was calcinated at 750 oC by slow heating (starting at RT and ending at the desired calcinations temperature for 2 h).XRF was applied to identify the chemical composition and purity of the extracted silica, while XRD was applied to confirm the amorphous nature and the presence of some induced carbon black in the obtained silica. It was found that S3 slowly heated at 750 oC presents the highest silica content (98.6 %). Such sample was fed directly to the calcinations furnace at 750 oC (sudden heating for comparison) where it presents only 90.6% silica, and 3.74 % residual carbon black. However, the extracted silica from sample S3 was used to prepare glasses obeying the composition (75-x) mol% RH-silica, x mol% Bi2O3, 25 mol% Na2O, (where 0 ≤ x ≤ 20).FTIR spectroscopic analysis was applied to investigate the internal structure of the prepared glasses, where the glass networks were found to contain mainly SiO4, BiO3 and BiO6 structural groups, as well as some bridging and non-bridging oxygen anions. Also, some O-H and H-O-H groups were also detected which may be due to the used KBr disk technique.