Chemical Engineering Journal 155 (2009) 916–924 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Preparation of mesoporous silica with grafted chelating agents for uptake of metal ions Zeid A. Alothman a,∗ , Allen W. Apblett b a Department of Chemistry, College of Science Building #5, PO Box 2455, King Saud University, Riyadh 11451, Saudi Arabia b Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, OK, USA article info Article history: Received 13 May 2009 Received in revised form 6 September 2009 Accepted 19 September 2009 Keywords: Mesoporous silica TEOS GPTMS 29 Si NMR Copper abstract Functionalized hexagonal mesoporous silicas were prepared by chemical modifcation of a surfactant free mesoporous silica (OSU-6-W) with 3-glycidoxypropyltrimethoxysilane. Different degrees of derivitiza- tion with 3-glycidoxypropyl were realized by using either a single silylation reaction or two silylation reactions with an intermediate hydrolysis step. The two resulting inorganic–organic hybrids were characterized by solid-state 29 Si nuclear magnetic resonance (NMR) spectroscopy, a titration method, and elemental analysis of the modified samples and the average numbers of pendant groups were found to be 2.17 and 3.49 groups/nm 2 , respectively. Surface area analysis showed that these materials have pore diameters of 40.7 and 33.2 Å and surface areas of 966 and 720 m 2 /g, respectively. Infrared spectroscopy, solid-state NMR for 13 C and 29 Si nuclei and X-ray diffraction patterns are in agreement with the success of the preparation of organically modified mesoporous silicas. The basic centers of the attached pendant groups provide the capacity to extract copper from aqueous solution via an adsorption process that followed the Langmuir model and had a remarkably high capacity of 6.75 mmol g -1 for adsorption of copper. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The covalent grafting of organic molecules with desired func- tions onto a variety of inorganic surfaces has significant practical advantages, such as improved structural and thermal stability, swelling behavior, accessibility to the reactive centers, and insolu- bility in organic and aqueous solvents [1,2]. One example of such materials is inorganic–organic hybrids based on porous inorganic substrates with pendant metal-coordinating groups that provide green chemical solutions in the areas of catalysis and removal of contaminants [3,4]. Among the many inorganic materials that are capable of covalently binding organic compounds, mesoporous sil- ica materials are extremely promising due to their exceptionally high surface area, large pores, and high thermal and chemical sta- bilities [1,4]. The presence of high concentrations of silanol (Si–OH) groups on the surface of mesoporous silicas enables the immobi- lization of a great number of organic molecules [5]. Furthermore, a large family of different mesoporous silicate structures can be synthesized through the variation of reaction conditions and the nature of the templating molecules or ion used [6]. ∗ Corresponding author. Tel.: +966 14675999; fax: +966 14675992. E-mail address: zaothman@ksu.edu.sa (Z.A. Alothman). Materials containing glycidyl functional groups have proven extremely popular for the attachment of various reactive groups and ligands due to the facile nucleophilic ring-opening reaction of the pendant epoxide functionality [7]. Amines react to yield mate- rials with favorable exchange kinetics for transition metal ions, due to the hydrophilic character of the resultant material that is the result of the ring-opening reaction which generates a hydroxyl group on the carbon atom  to the incoming amine [8]. This group makes this site rather hydrophilic, and is believed to make these materials particularly effective in applications involving the treat- ment of aqueous feed streams for metal-ion recovery. It is much less clear whether this hydroxyl group is able to function as an additional binding site for chelation of metals [9]. The purpose of this work was to develop a new family of mesoporous silicas with grafted chelating agents for complexing metal ions with increased functional group coverage and pore sizes that were maintained as large as possible. To realize these objectives a single grafting step with 3-glycidoxypropyltrimethoxysilane was compared to a procedure that used two silylation reactions with an intermedi- ate hydrolysis reaction. The products were characterized using several techniques including X-ray powder diffraction (XRD), N 2 adsorption–desorption analysis (BET), solid-state 13 C and 29 Si MAS NMR spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, UV–vis spectrometer, and elemental analy- sis. 1385-8947/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2009.09.028