New Amine-Modified Silicas: Synthesis, Characterization and Its Use in the Cu(II)-Removal from Aqueous Solutions

Abstract

Porous silica has been chemically modified with conjugated phenylamine and phenyldiamine moieties using the homogeneous route. This synthetic route involved the reaction of carbaldehyde derivatives with 3-aminopropyltrimethoxysilane prior to immobilization on the support. The resulting materials have been characterized by elemental analysis, FT-IR, 13 C NMR of the solid state, nitrogen adsorption-desorption isotherm, BET surface area, B.J.H. Pore sizes, thermogravimetry analyser (TGA) curves, X-ray diffraction (XRD) and scanning electron microscope (SEM). The new chelating surfaces exhibit good chemical and thermal stability. The solids were employed as Cu(II) adsorbents from aqueous solutions at room temperature. The effects of pH and adsorption kinetics have been studied 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 24.5 mg Cu(II) g −1 modified silica, whereas the adsorption capacity of the unmodified silica was only 1 mg Cu(II) g −1 silica. On the basis of these results, it can be concluded that it is possible to modify chemically silica with amine derivatives and to use the resulting modified porous silica as an effective adsorbent for Cu(II) in aqueous media.