Polyethylenimine (PEI) was grafted on silica particles by using γ-chloropropyltrimethoxysilane as couplant, and the novel composite adsorption material of PEI/SiO₂ for medical application was prepared, which has strong adsorption ability toward uric acid. Static adsorption experiment results show that the macromolecules of PEI on silica particles can produce strong adsorption force for trihydroxyl purine that is a tautomer of uric acid by hydrogen bond interaction. The isothermal adsorption was accorded with Freundlich equation, and the saturated adsorption amount was able to reach 84.9 mg/g. The pH value of the aqueous solution might exert great effect on adsorption property of PEI/SiO₂. In neutral solution PEI/SiO₂ had very strong adsorption ability. In acidic or basic solution the adsorption actions were all week. Temperature had a certain influence on adsorption property of PEI/SiO₂, and the adsorption amount was increased with increment of temperature.

Key words: uric acid, medical adsorption material, polyethylenimine, hydrogen bond interaction