Parametric evaluation of silica extraction from oil palm empty fruit bunches

Abstract

Oil palm empty fruit bunches serve as a sustainable silica source to address solid waste challenges. This study evaluated five parameters for silica extraction including calcination temperature between 500 and 700 °C, calcination time from 90 to 150 minutes, fiber size of 1 cm versus 0.25 mm, and alkali type using NaOH or KOH at concentrations of 5 to 15%. The highest silica yield was obtained at 500 °C; however, the product remained brownish due to residual carbon. Calcination at 600–700 °C produced significantly whiter silica, indicating improved purity through more complete removal of carbonaceous impurities. Characterization confirmed the amorphous nature of the product. FTIR identified key silica functional groups, while SEM showed a dense lamellar morphology for NaOH-extracted silica. BET analysis revealed that NaOH treatment significantly enhanced the surface area to 39.86 m2/g compared to 5.37 m2/g for KOH. XRF analysis further indicated that NaOH treatment achieved a higher purity of 42.8 wt% which corresponds to an intrinsic framework purity of 91.2 wt% upon a salt-free normalization basis. These results demonstrate that oil palm empty fruit bunches are viable precursors for high-quality silica in advanced applications.