Synthesis of sodium silicate crystals from rice husk ash

Abstract

The rich husk is an agricultural waste of rice cultivation worldwide, which is highly rich in amorphous silica. Rice husk obtained from Dagiri was pyrolysed at 750 ? to give white ash (RHA) which was further treated with acid (ARHA). The ash was reacted with sodium hydroxide at 90 ? for 2 hours 30 min to produce Sodium silicate crystals. Sodium silicates synthesized in the study were characterized with some physicochemical parameters. Their structural and morphological properties were assessed using a Fourier Transform Infra-red spectrophotometer (FTIR), X-ray Diffractometer (XRD) and Scanning Electrode Microscope (SEM). The mineralogical composition of the ash and sodium silicate was investigated with Energy-dispersive X-ray fluorescence (EDXRF) spectrometer. The sodium silicate produced has a melting point of 61 ?, a pH of 12.03 and appeared as brownish-white to clear-white in colour. The RHA and ARHA from XRD investigation showed patterns which match the mineral phase cristobalite, while that of the sodium silicate XRD patterns match the mineral heptahydrate disodiumtrioxosilicate as the most dominant phase. Rietveld refinement of the XRD pattern for the sodium silicate gave Rwp = 12.81, Rexp = 5.55, ?2 = 5.3274 and GoF = 2.3081 against a dual phase analysis. The sodium crystal-synthesized is suitable for use in cosmetic formulations.