Heavy metal remediation using functionalized mesoporous silicas with controlled macrostructure

A synthesis procedure is described for making functionalized mesoporous sil ica macrostructures that can serve as self-supporting adsorbents for enviro nmental remediation and other separations applications. The material, whose mesopores were functionalized with 3-mercaptopropyltrimethoxysilane ligand s, can be made into spheres, irregular particles, and truncated cones havin g diameters from 1 to 15 mm through a one-step emulsion synthesis procedure . Other shapes such as pellets can be formed by molding the precursor gel. The macro- and mesomorphology of the materials were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy , and Si-29 MAS NMR. Physisorption properties were investigated using nitro gen adsorption measurements. The surface area of these materials determined via the BET method ranged from 864 to 1184 m(2) g(-1). The materials are e xtremely effective in the removal of mercury and silver ions from aqueous s olutions. The amount of mercury adsorbed ranged from 0.24 to 1.26 mmol g(-1 ), depending on the degree of functionalization. Silver is less strongly ad sorbed than mercury, with a maximum loading of 0.89 mmol g(-1). In binary a dsorption of mercury and silver ion mixtures, the selectivity for mercury r anged from 1.39 to 2.24. The adsorption capacity of the functionalized mate rials for nitrogen is comparable to that of unfunctionalized materials.