This research aimed to synthesize silica from sugarcane bagasse and to determine adsorption kinetics model. Synthesis of silica was prepared by sol-gel method by adding HCl 1 M into Na₂SiO₃ solution from the synthesis of sugarcane bagasse. The synthesized silica was characterized by FTIR spectroscopy and XRD. The product was then used for the adsorption of NO₃^- anion. Result of characterization by FTIR showed that the silica was successfully synthesized by the presence of the absorption of silanol (Si-OH) and siloxane (Si-O-Si) groups. XRD characterization showed that silica had amorphous structure. The optimum time for the adsorption of anion NO₃^- by silica was 2880 minutes or 2 days. From the results of the study it was found that the adsorption kinetic follows the Lagergren Pseudo-Second-Order model with the rate constant (k₂) of -3.120 x 10³ min^-1. Based on the Elovich equation, the initial adsorption rate of -6.054 x 10^-14 mg g-1 min-1 and the magnitude of surface area and activation energy (β) were -1.415 x 106 g mg^-1. Based on the intra-particle diffusion kinetics and Boyd model, mechanism of nitrate anion adsorption by silica sorbent occurred through two stages of the reaction controlled by intra-particle diffusion and the rate of adsorption process was controlled by the mass transfer rate of the external anion nitrate molecule onto the silica adsorbent

Keywords: silica; adsorption kinetics; nitrate anion; intra-particle; Boyd