Efficient Removal of Hg(II) from Water under Mildly Acidic Conditions with Hierarchical SiO₂ Monoliths Functionalized with –SH Groups

In this work, novel adsorbents based on 3D hierarchical silica monoliths functionalized with thiol groups were used for the removal of Hg(II) ions from an acidic aqueous solution (pH 3.5). Silica monoliths were synthesized by using two different pluronic triblock polymers (P123 and F127) to study the effect of porous structure on their sorption capacity. Before and after functionalization by grafting with 3-mercaptopropyltrimethoxysilane (MPTMS), the monoliths were characterized by several techniques, and their Hg(II) removal potential was evaluated in batch experiments at 28 °C and pH 3.5, using different initial concentrations of Hg(II) ions in water (200–500 mg L−1). The thiol groups of the monoliths calcined at 550 °C showed thermal stability up to 300 °C (from TG/DTG). The functionalized monolith synthesized with P123 polymer and polyethylene glycol showed favorable hierarchical macro-mesopores for Hg(II) adsorption. M(P123)–SH exhibited 97% removal of Hg(II) at concentration 200 mg L−1. Its maximum adsorption capacity (12.2 mmol g−1) was two times higher than that of M(F127)–SH, demonstrating that the 3D hierarchical macro-mesoporosity allowing accessibility of Hg(II) to thiol groups favors the physical and chemical adsorption of Hg(II) under slightly acidic conditions

Incorporation of photoactive TiO2 in an aluminosilicate inorganic polymer by ion exchange

In the present paper, it is described a procedure to ion exchange in an aluminosilicate inorganic polymer (geopolymer) in order to incorporate photoactive TiO 2. Metakaolin base geopolymers synthesized at 40 and 90 °C were chosen to be ion-exchanged with a solutions of (NH 4) 2 TiO (C 2O 4) 2-H 2O with and without previous treatment with NH 4Cl. The final geopolymers were characterized by SEM, FT-IR, Raman, XRD, BET, UV/Vis spectroscopy and fluorescence. It was confirmed that ion-exchange method incorporated anatase TiO 2 particles inside the geopolymer, affecting the geopolymers bond vibration modes of the AlO 4-SiO 4 framework. The observed blue shift in the UV/Vis spectra, suggest that those TiO 2 nanoparticles grew inside the micropores of the geopolymer producing quantum size effects. The photoactivity of such particles was determined by means of photoluminescent spectra and bleaching of methylene blue (MB), which confirms the potential applications of ion-exchanged geopolymers (IEGs) for photocatalytic purposes. © 2011 Elsevier Inc. All rights reserved.J.R. Gasca-Tirado wants to thank CONACYT for scholarship and to A. Galindo-Sifuentes, M.A. Hernandez-Landaverde, J.E. Urbina-Alvarez, F. Rodriguez-Melgarejo, A. Mauricio-Sanchez, J.L. Ojeda-Elizarraras, M.S. Garcia-Guillen, C. Vazquez-Ramos and G. Fonseca-Hernandez for their kind technical assistance.Gasca-Tirado, JR.; Manzano Ramirez, A.; Villaseñor-Mora, C.; Muñiz-Villarreal, MS.; Zaldivar-Cadena, AA.; Rubio-Ávalos, JC.; Amigó Borrás, V.... (2012). Incorporation of photoactive TiO2 in an aluminosilicate inorganic polymer by ion exchange. Microporous and Mesoporous Materials. 153:282-287. doi:10.1016/j.micromeso.2011.11.026S28228715