Ion Exchange in Geopolymers

Geopolymers have been widely used for construction and building materials. Nevertheless, some other applications have been found from their ability to be ion exchanged. An example is the encapsulation of heavy metals, but some others involve the ion exchange of the aluminosilicate structure to form photoactive particles or to link copper ions. In this chapter, we summarize some of the properties which make aluminosilicate inorganic polymer (geopolymers) ion exchangeable: the synthesized temperature, its effect over their porosity and their stoichiometric nature. Also, the effects of ion exchanging a geopolymer with an NH4+Cl, (NH4)2TiO2(C2O4)2 and (CH3)4N+Br are presented. The geopolymer was characterized by FT-IR, XRD, BET and MAS NMR, showing how a 100% of replacement was achieved for NH4+Cl. On the contrary, the efficiency was reduced in (NH4)2TiO2(C2O4)2 and (CH3)4N+Br, effect ascribed to the fact of the molecular size that did not allow the counterions to reach the aluminum atoms in the geopolymer. Finally, the procedure followed to ion exchange a metakaolinite-based geopolymer is described, and the potential applications related are presented

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

Effect of porosity on the absorbed, reemitted and transmitted light by a geopolymer metakaolin base

In the present paper, the optical characterization of a geopolymer synthesized at three different temperatures (40, 60 and 90 °C) is described. The results were correlated to the porosity fraction in order to obtain a photoluminescent geopolymer. A two-flux model was employed to relate the fraction of light absorbed, remitted and transmitted by a representative layer of geopolymer. Porosity was measured by nitrogen adsorption and correlated with the optical properties to determine the fraction of UV/Vis light transmitted through the samples. It was found that the geopolymer synthesize temperature and the incident wavelength greatly affect the fraction of light transmitted by the samples. The UV/Vis spectrum was divided into three zones according to the observed behavior. In the first zone, the difference in transmission fraction was significant; in the second zone, this difference decreased and practically vanished at the third one. Considering the highest transmission fraction at 90 °C, a photoluminescent geopolymer with the strongest emitting peak at 469 nm was synthesized. © 2010 Elsevier B.V. All rights reserved.Gasca-Tirado, JR.; Rubio-Ávalos, JC.; Muñiz-Villarreal, MS.; Manzano Ramirez, A.; Reyes-Araiza, JL.; Sampieri-Bulbarela, S.; Villaseñor-Mora, C.... (2011). Effect of porosity on the absorbed, reemitted and transmitted light by a geopolymer metakaolin base. Materials Letters. 65(5):880-883. doi:10.1016/j.matlet.2010.12.003S88088365

The effect of temperature on the geopolymerization process of a metakaolin-based geopolymer

This paper describes the effect of different curing temperatures on the geopolymerization process, physical, mechanical and optical properties of a metakaolin-based geopolymer activated by alkali. The influence of different curing temperatures (within the range 30 to 90 °C) was studied systematically by means of differential scanning calorimetry (DSC), SEM, UV/Vis Spectrophotometry, Leaching analysis and Brunauer-Emmet-Teller method (BET). The results showed the existence of an optimum temperature at which the geopolymer presents the best physical and mechanical properties. The geopolymers cured at 30 and 90 °C presented high porosity, and were translucent to the Visible light, which makes possible to tailor this inorganic polymers for optical and photocatalytic applications. © 2011 Elsevier B.V. All rights reserved.Muniz-Villarreal M.S. wants to thank CONACYT for scholarship, and Maria-Carmen Delgado, Eleazar-Urbina and Martin-Adelaido Landaverde for their technical assistance.Muñiz-Villarreal, MS.; Manzano Ramirez, A.; Sampieri-Bulbarela, S.; Gasca-Tirado, JR.; Reyes-Araiza, JL.; Rubio-Ávalos, JC.; Pérez Bueno, JJ.... (2011). The effect of temperature on the geopolymerization process of a metakaolin-based geopolymer. Materials Letters. 65(5):995-998. doi:10.1016/j.matlet.2010.12.049S99599865

Thermal Energy Storage by the Encapsulation of Phase Change Materials in Building Elements—A Review

The energy sector is one of the fields of interest for different nations around the world. Due to the current fossil fuel crisis, the scientific community develops new energy-saving experiences to address this concern. Buildings are one of the elements of higher energy consumption, so the generation of knowledge and technological development may offer solutions to this energy demand, which are more than welcome. Phase change materials (PCMs) included in building elements such as wall panels, blocks, panels or coatings, for heating and cooling applications have been shown, when heating, to increase the heat storage capacity by absorbing heat as latent heat. Therefore, the use of latent heat storage systems using phase change materials (PCMs) has been investigated within the last two decades. In the present review, the macro and micro encapsulation methods for construction materials are reviewed, the former being the most viable method of inclusion of PCMs in construction elements. In addition, based on the analysis of the existing papers on the encapsulation process of PCMs, the importance to pay more attention to the bio-based PCMs is shown, since more research is needed to process such PCMs. To determine its thermophysical and mechanical behavior at the micro and macro levels, in order to see the feasibility of substituting petroleum-based PCMs with a more environmentally friendly bio-based one, a section devoted to the excellent PCM with lightweight aggregate (PCM-LWA concrete) is presented due to the lack of description given in other reviews