Formation and efficacy of TiO sub(2)/AC composites prepared under microwave irradiation in the photoinduced transformation of the 2-propanol VOC pollutant in air

• Published in: Applied catalysis. B, Environmental Environmental, 2013-09, Vol.140-141, p.646-651
• Main Authors: Horikoshi, Satoshi, Sakamoto, Shintaro, Serpone, Nick
• Format: Article
• Language: English
• ISSN: 0926-3373

This article reports on the preparation and characterization (SEM, SEM-EDX, XRD, diffuse reflectance spectroscopy, and BET surface area) of TiO sub(2) particles supported on activated carbon (AC) particulates using a titanium oxysulphate precursor and subjecting the aqueous dispersion to microwave (MW) heating and to a more traditional heating method with an oil bath. The TiO sub(2)/AC composites were subsequently tested for their photoactivity through an examination of the transformation of a volatile organic pollutant (VOC) in air: iso-propanol. Under MW irradiation at 70 degree C the synthesis resulted in the formation of a thin coating about the AC support, while TiO sub(2) particles formed at higher temperatures; the average particle size of TiO sub(2) tended to decrease with increase in reaction temperature from 426nm at 80 degree C to 243 nm at 180 degree C The accelerated heating of the AC-dispersed solution above 80 degree C was confirmed by determining the dielectric loss ( epsilon ") of the dispersion at various temperatures at the microwave frequency of 2.45 GHz. Subjecting the dispersion to oil-bath heating only led to formation of a thin film about the AC particulates. In the absence of the AC support TiO sub(2) particle sizes averaged ca. 460 nm for the MW method, while they averaged around 682 nm with the oil-bath method. The BET specific surface area of the TiO sub(2)/AC composites was significantly greater for the MW heating method (ca. 990 m super(2) g super(-1) versus 848 m super(2) g super(-1) for the oil-bath method). Both UV-vis spectroscopy (estimated band-gap energy of TiO sub(2)/AC composites was 3.3 eV) and XRD spectra confirmed the anatase nature of the TiO sub(2) specimens. The MW-produced TiO sub(2)/AC particulates proved to be nearly six-fold more photoactive in the photoinduced degradation of the VOC pollutant than those produced by the oil-bath method. A possible growth mechanism of the TiO sub(2)/AC composites is proposed.