Dual functionality of TiO2-flyash nanocomposites: Water vapor adsorption and photocatalysis

TiO2 nanoparticles were in situ supported on lignite fly ash (TiO2-FA) and investigated by several techniques. X-ray diffraction (XRD) analysis supplied information about the generation of anatase phase. Scanning electron microscopy (SEM) images with energy dispersive X-ray analysis (EDX) revealed variations in the surface morphology of raw FA after TiO2 loading. Nitrogen adsorption-desorption isotherms (BET) isotherms indicated the formation of a mesoporous structure. X-ray photoelectron spectroscopy (XPS) confirmed the buildup of TiO2 nanoparticles on the FA matrix with the form of TO4+ oxidation state. The optimum FA content of the composite was found as 88%. The supported nanocatalysts were tested for water vapor adsorption towards evaporative cooling of hydrophilic surfaces and for decolorization and degradation of methyl orange (MO) under UV irradiation. The mesoporous TiO2-FA was found to be hydrophilic with capillary condensation in the water vapor adsorption isotherm. Dark adsorption experiments followed pseudo-second order kinetics and Langmuir type of isotherms. Kinetics was discussed in terms of Langmuir-Hinshelwood model. The repeatability of photocatalytic activity was also tested. H2O2 used as an electron scavenger accelerated decolorization and degradation of MO. (C) 2014 Elsevier B.V. All rights reserved.