Adsorptive properties of a [3-(methylamino)propyl]trimethoxysilane-modified corn. SiO2 towards sinapic acid were detd. Model Freundlich, Langmuir, Jovanovic, Dubinin-Astakhov and Redlich-Peterson isotherms were used. Non-linear fitting anal. was employed for estn. of isotherm parameters. The adsorption capacity (Dubinin-Astakhov model) of modified SiO2 towards phenolic acid was 136.8 mg/g and the adsorption efficiency exceeded 90% at the lowest initial adsorbate concentration.