Synthesis of synthetic amorphous silica powder from palm oil mill fly ash extract by carbon dioxide impregnation

Abstract

Palm oil mill fly ash (POMFA) is rich in amorphous silica and can be extracted by sodium hydroxide solvent. This work aims to synthesize synthetic amorphous (SAS) powder silica that has mesoporous pores and a high specific surface area. The sol–gel precipitation process was applied by CO 2 impregnation and polyethylene glycol (PEG) 400 was used as the surfactant to obtain the synthetic silica powder from the extract. A temperature-controlled 1000 cm 3 glass precipitator equipped with a stirrer was used for the precipitation process. The extracted silica was mixed with PEG at pre-determine concentration, and 500 cm 3 of the mixed liquid was put in the precipitator and stirred at 1000 RPM. The carbon dioxide impregnated at a flow rate of 100 cm 3 min −1 to destabilize the silica extract. The study was done by using PEG-400 as a dispersant to improve the specific surface area of the obtained precipitated silica. The temperature, precipitation time, and the PEG concentration were varied to study their effect on SAS yield. The optimum SAS yield of 80.01% was obtained at a temperature of 70 °C, time of 90 min, and a PEG concentration of 5%. The characteristics of the SAS obtained are SSA of 198.55 m 2 g −1 , volume pore of 0.289 cm 3 g −1 , and pore diameter of 5.32 nm.