Porous SiO₂ has been chemically modified with functional ortho-, meta- or para-nitrophenyl moieties using the heterogeneous route. This synthetic route involved the reaction of carbaldehyde derivatives with 3-aminopropyl trimethoxysilane prior to immobilization on the support. The new modified surfaces have been characterized by elemental analysis, FT-IR, ¹³C NMR of the solid state, nitrogen adsorption-desorption isotherm, BET surface area, B.J.H. Pore sizes, thermogravimetry curves (TGA) and scanning electron microscope (SEM). The new materials exhibit good chemical and thermal stability. These products were employed as a Cu(II) adsorbent from aqueous solutions at room temperature using the batch technique. Flame atomic absorption spectrometry was used to determine the Cu(II) concentration in the filtrate after the adsorption process. The results indicate that under the optimum conditions, the maximum adsorption value for Cu(II) was 20.0 mg Cu(II) g^-1 modified silica, whereas the adsorption capacity of the unmodified silica was only 1.0 mg Cu(II) g^-1 silica. On the basis of these results, it can be concluded that it is possible to modify chemically SiO₂ with functional groups and use it as adsorbents for metals in aqueous media.