Nanoporous High Surface Area Silicas With Chelating Groups For Heavy Metal Ion Adsorption From Aqueous Solution

Abstract

Nanoporous high surface area silicas are an ideal substrate for the design of materials with useful properties via chemical surface modification. The adsorption of heavy metals for contaminated water detoxification is one potential application. In this work we have used three different kinds of silica substrates with varying pore structures; commercially available narrow pore and wide pore silica gels, as well as surfactant templated mesoporous SBA-15 exhibiting a relatively narrow pore size distribution. These silicas have each been subjected to post-synthesis modification with an organosilane consisting of ethylenediamine triacetic acid functionalities for chelation/adsorption of metal ions from aqueous solution. The surface modified materials have been characterized by N2 adsorption for the determination of surface area and pore size distribution and FTIR spectrometry to probe metal ion - surface bonding interactions with the help of computational calculations. Metal ion adsorption isotherms for Hg(II), Cd(II), Cu(II), Sr(II) and Cr(III) are reported. Previous studies have shown that postsynthesis modification of narrow pore silicas results in a significant reduction of surface area, with dramatically reduced adsorption capacity. In this work chemical surface modification has been achieved with little to no reduction in surface area, thus adsorption capacity remains high even for narrow pore silicas. Very large adsorption capacities, approaching one gram Hg(Il)/gram of silica have been achieved. Diffuse reflectance FTIR spectrometry show changes after metal adsorption indicating specific metal - organosilane interactions are responsible for adsorption.

Date of Award	2010
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Jonathan Blitz (Supervisor)