No 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 21 , whereas the adsorption capacity of the unmodified mesoporous silica was only 0.04 ¡ 0.02 mmol Cd(II) g 21 . 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.

No abstract

Recent advances in the development of new materials are having a major impact on Analytical Chemistry. For example, the unique properties of ordered mesoporous silicas have been shown to enhance the analytical performance of many existing techniques or allow new, exciting ones to be developed. Likewise, the introduction of organo-functional groups makes mesoporous silicas highly versatile and enables them to perform specialized tasks, such as the adsorption of toxic heavy metals from aqueous solutions. In this tutorial review, we present readers with a brief introduction to the most relevant achievements in the preparation of hybrid mesoporous silicas functionalized with chelating ligands for the complexation of heavy metals. We also provide some recent examples from the last ten years regarding the analytical applications of such hybrid silicas. Two topics of great current interest in environmental water analysis for heavy metal detection, namely the use of hybrid mesoporous silicas as sorbents for solid-phase extraction and the use of these materials to develop new strategies for electrochemical detection of heavy metals by stripping voltammetry, are addressed.