Metal (M = Co2+, Ni2+, and Cu2+) grafted mesoporous SBA-15: Effect of transition metal incorporation and pH conditions on the adsorption of Naproxen from water

Incorporation of transition metals onto the surface of mesoporous silica via grafting techniques could become a potential strategy for the bottom-up design of sorbents for the removal of pharmaceutical drugs and other emerging contaminants from water sources. Here we report the incorporation of Co2+, Ni2+, or Cu2+ onto the surface of mesoporous SBA-15 via an amino-organic grafting method and the screening of the materials as sorbents for the removal of Naproxen from water. The functionalization procedure involved the reaction of 3-aminopropyltriethoxysilane with OH groups available on SBA-15 surfaces, followed by the anchoring of the desired metal. Removal of traces of sulfates from the metal sources and further metal anchoring were achieved after post-synthesis treatment at alkaline conditions. The resulting metal-modified materials were fully characterized using X-ray powder diffraction, N2 adsorption/desorption isotherms gathered at −196 °C, SEM/EDX, FT-IR, and TGA. Aqueous phase single point adsorption experiments showed that Cu-based materials are good sorbents for the uptake of low-concentration Naproxen at 25 °C and approaching alkaline conditions. The materials uptake capacities decreased as follows: CuNH2_g_SBA-15 > NiNH2_g_SBA-15 > CoNH2_g_SBA-15. In general, the adsorption results correlate well with the observed structural and textural properties of the materials, suggesting also that the metal amino-organic loading is highly dependent on the nature of grafting process and choice of metal.