Cetylpyridinium chloride (CPC) is commonly used to precipitate hyaluronic acid (HA) from crude extract in a HA purification process. 3-(Trimethoxysilyl)-propyl-dimethyl octadecyl ammonium chloride (Si-QAC) has a structure very similar to CPC when it is bonded to surfaces through its silane base. By taking advantage of its easy surface bonding property, Si- QAC was bonded to the silica-coated magnetite to facilitate HA recovery. The effects of pH, salt concentration, and the temperature on HA adsorption to Si-QAC-magnetite were studied. Not only the positively charged nitrogen but also hydrophobic long tail of Si-QAC contributed to the strong interaction between HA and Si-QAC-magnetite. The maximum HA adsorption capacity was 38 mg/g-dry magnetite and the equilibrium dissociation constant was 0.016 g/l at pH 4 under 37 degrees C. The adsorbed HA could be effectively desorbed by 1 N NaCl supplemented with 0.1% Triton X100.