| Summary: | Geothermal sludge waste has a high silica content in an amorphous phase (∼92 SiO2). Preparation of nanosilica using cationic surfactant as a template and geothermal waste as a source of silica has been carried out using sol-gel method. lt involves extraction of silica to form sodium silicate using alkalis solution and added with acid (5M HCl) to form gel. Cetyltrimethylammonium bromide (CTAB) was added to the sol phase to control the size of the particles. This study was carried out to determine the effect of reaction temperature (70°C, 80°C, and 90°C) and concentration of NaOH (2.5M; 3.5M; and 4.5M) on the product of nanosilica. From this study, the highest yield of nanosilica at 99 can be obtained by the extraction temperature of 90°C, and NaOH concentration of 4.5M. Chemical composition of nanosilica shows a silica purity of 98. Characterization of the nanosilica using XRD revealed that the sample with the addition of surfactant is mainly amorphous, with the crystallite size was about 16nm. © 2022 Author(s).
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