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 TiO2. Metakaolin base geopolymers synthesized at 40 and 90 °C were chosen to be ion-exchanged with a solutions of (NH4)2 TiO (C2O4)2-H2O with and without previous treatment with NH4Cl. 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 TiO2 particles inside the geopolymer, affecting the geopolymers bond vibration modes of the AlO4–SiO4 framework. The observed blue shift in the UV/Vis spectra, suggest that those TiO2 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.

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► Growth of TiO2 inside a geopolymer is achieved by ion-exchange.
► The presence of micropores inside geopolymers makes TiO2 particles grow to nanometric sizes, causing quantum size effects.
► These particles are anchored to the geopolymer framework and have photoactivity.
► The TiO2 optical properties may change as a function of the low synthesis temperature of geopolymers.