Synthesis of sodium silicate crystals from rice husk ash Scientific paper

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 pyrolyzed at 750 °C to give white ash (RHA) which was further treated with acid (ARHA). The ash was reacted with sodium hydroxide at 90 °C for 2.5 h to produce sodium silicate crystals. Sodium silicate synthesized in the study was characterized for some physicochemical parameters. Their structural and mor­phological properties were assessed using a Fourier transform infra-red spec­trophotometer (FTIR), X-ray diffractometer (XRD) and scanning electron 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 °C, 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 disodium trioxosilicate as the most dominant phase. Rietveld refine­ment of the XRD pattern for the sodium silicate gave Rwp = 12.81, Rexp = 5.55, χ2 = 5.3274 and GoF = 2.3081 against a dual phase analysis. The cry­stals synthesized are suitable for use in cosmetic formulations.