Adsorption of cadmium(ii) from aqueous media onto a mesoporous silica chemically modified with 2-mercaptopyrimidine

Abstract

A mesoporous silica (SBA-15) has been chemically modified with 2-mercaptopyrimidine using the homogeneous route. This synthetic route involved the reaction of 2-mercaptopyrimidine with 3-chloropropyltriethoxysilane prior to immobilization on the support. The resulting material has been characterized by powder X-ray diffraction, nitrogen gas sorption, FT-IR and MAS NMR spectroscopy, thermogravimetry and elemental analysis. The solid was employed as a Cd(II) adsorbent from aqueous solutions at room temperature. The effects of several variables (stirring time, pH, metal concentration and presence of other ions in the medium) have been studied using the batch technique. Flame atomic absorption spectrometry was used to determine the Cd(II) concentration in the filtrate after the adsorption process. The results indicate that under the optimum conditions, the maximum adsorption value for Cd(II) was 0.99 ± 0.03 mmol Cd(II) g⁻¹, whereas the adsorption capacity of the unmodified mesoporous silica was only 0.04 ± 0.02 mmol Cd(II) g⁻¹. On the basis of these results, it can be concluded that it is possible to modify chemically SBA-15 with 2-mercaptopyrimidine and to use the resulting modified mesoporous silica as an effective adsorbent for Cd(II) in aqueous media.