Carboxyl-functionalized mesoporous silica-carbon composites as highly efficient adsorbents in liquid phase

Mesoporous silica-carbon composites functionalized with acidic oxygen groups were prepared by oxidation of a layer of carbon deposited inside the silica pores. The synthesis procedure involved the following steps: a) removal of the silica surfactant, b) impregnation of the silica pores with a carbon precursor, c) carbonization and d) oxidation with ammonium persulfate. The resulting silica-carbon composites contained around 25-30 wt % of carbonaceous matter with a high density of acid oxygen groups attached to the deposited carbon (i.e. -COOH, -C=O and -OH). The structural characteristics of the parent silica were retained by the oxidized composite materials, which exhibit a high surface area, a large pore volume and a well-ordered porosity made up of uniform mesopores. The oxygen-functionalized silica-carbon composites were found to be excellent adsorbents of basic dyes (e.g. methylene blue) and heavy metals (i.e. Cu, Zn and Pb) in aqueous media.