Agro-wastes, especially ash containing silica, are promising sources of silica for synthetic amorphous silica production. In this research, palm oil mill fly ash (POMFA) was used as a raw material for silica gel production. The response surface method-central composite design was applied to study and to optimize the temperature and stirring speed for silica extraction from POMFA using sodium hydroxide solvent. Filtrates were analyzed using inductively plasma optical emission spectroscopy to measure their silica content. At the optimum condition, 60.42±0.83% of the silica can be extracted from the POMFA. The extract silica was acidified using 10% (v/v) H2SO4 to form silica gel. The chemical composition, the phases, and the micrograph of silica gel product are similar to the commercial silica gel.
