Biosilica from frustul diatom Navicula sp. TAD was isolated under optimal conditions by washing with 20% HCl and baking at 600 °C. The treatments successfully removed 78.00 ± 0.514% of impurities from the biosilica during washing, and 93.072 ± 0.347% were further removed after baking. Biosilica Frustule Navicula sp. TAD resulting from HCl washing and burning at 600oC has a whiter silica color. Biosilica was identified by Fourier transform infrared spectroscopy (FTIR) at wave numbers 1601, 1062, 962, 799, and 470 cm-1, which were associated with stretching, bending, and vibrational groups of Si-O-Si bonds. Scanning electron microscopy (SEM) observations show that the silica frustule nanoporous surface structure can be seen, and the results of Energy Dispersive X-Ray (EDX), silica from Navicula sp. TAD is composed of silicon and oxygen. This shows that silica was obtained from the diatom Navicula sp. TAD. X-ray diffraction (XRD) analysis shows that the morphology of SiO2 in biosilica is a typical amorphous silica