Silica surface modified with silylbenzoxazine monomers having different bulky groups at ortho and para positions on the oxazine ring, i.e. 3-triethoxysilyl-n-propyl-3,4-dihydro-2H-1,3-benzoxazine coupled with silica (4), 3-triethoxysilyl-n-propyl-3,4-dihydro-6-methyl-2H-1,3-benzoxazine coupled with silica (5), and 3-triethoxysilyl-n-propyl-3,4-dihydro-6,8-dimethyl-2H-1,3-benzoxazinc coupled with silica (6) are synthesized to obtain a series of ion extraction resins. Fourier transform infrared spectroscopy (FT-JR) and elemental analysis support the successful coupling of benzoxazine-functional silane onto silica surface. The ion extraction studies of various alkali and alkaline earth metal ions from aqueous phase via the surface treated silica column chromatography shows the significant ion extraction ability of (6) compared to those of (4) and (5).