Simple process for synthesis of layered sodium silicates using rice husk ash as silica source

• β, δ, and α phases of layered sodium silicates are prepared from rice husk ash using a simple process.
• The phases transform from β to δ to α as time and temperature increase.
• Optimal synthesis conditions produced layered sodium silicates that exhibited excellent Ca2+ and Mg2+ binding capacities.
• Agricultural waste is converted to valuable products for potential use as detergent builders.

β, δ, and α phases of layered sodium silicates were synthesized using waste rice husk ash (RHA) as the raw material by a simple sintering process. X-ray diffraction (XRD) measurements revealed a phase transformation from β through δ to α as the reaction temperature and time of synthesis was increased. Raman studies confirmed the synthesized products have a layered SiO4 tetrahedral structure. Further, a SiOSi (Na) band bond force constant sequence for the three phases was speculated (δ > β > α) that agrees with the ion binding sequence of the phases. Scanning electron microscopy (SEM) elucidated the typical micromorphology of the synthesized products, which was structurally similar to that of RHA. Optimal synthesis conditions produced layered sodium silicates that exhibited Ca2+ and Mg2+ binding capacities of 406 and 453 mg/g, respectively. This method can therefore be used to simply and cheaply convert agricultural waste into valuable products.

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