Rice husk ash as a renewable source for synthesis of sodium metasilicate crystal and its characterization

The objective of the present work is to develop an environmentally friendly ("green") and economically effective process to synthesize sodium metasilicate crystal from cheap rice husk ash (RHA). We made full use of the silica in RHA as raw material, extracting the silica liquid via an alkali dissolving method and using it to prepare sodium metasilicate crystal by solvent-induced crystallization. The as-synthesized samples were characterized by X-ray diffraction, infrared spectra, optical microscopy and thermal gravimetric analysis. As per the results, we concluded that the optimum condition for the maximum dissolution rate of silica was sodium hydroxide and RHA after acid pre-treatment at a solid/liquid ratio of 1:8 with 10 wt% of NaOH at 90 °C for 2.5 h. Meanwhile, we can prepare sodium metasilicate pentahydrate qualified with silica under the mild condition.