TiO2 hydrosols with high activity for photocatalytic degradation of formaldehyde in a gaseous phase

Abstract

Two types of TiO2 hydrosols (TOSO and HTO) were prepared from titanium sulfate (TiOSO4) and metatitanic acid (H2TiO3) by a chemical precipitation-peptization method, respectively. The prepared hydrosols were characterized by means of X-ray diffraction, particle size distribution, scanning electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller and Barret-Joyner-Halender methods. The results showed that the TiO2 hydrosols with an anatase crystal structure had smaller particle sizes, higher surface areas, larger pore volume, and higher transparence than Degussa P-25 suspension. The photocatalytic activity of the TiO2 hydrosols was evaluated for formaldehyde degradation under UVA illumination in a gaseous phase. The results demonstrated that the photocatalytic activity with the catalyst loading of 2mgcm(-2) was ranked as an order of HTO>TOSO>P-25. The photocatalytic activity was further studied using the HTO catalyst under different experimental conditions. The results showed that catalyst loading, relative humidity, and initial concentration could influence the efficiency of HCHO photocatalytic degradation. It was found that a catalyst loading of more than 2mgcm(-2) and a relative humidity of 55% were two essential conditions for achieving the best performance under these experimental conditions. The repeated experiments indicated that the HTO catalyst was reasonably stable and could be repeatedly used for the HCHO oxidation under UVA irradiation. This investigation would be helpful to promote the application of TiO2 photocatalytic technique for indoor air purification.

An amorphous TiO2 sol sensitized with H2O2 with the enhancement of photocatalytic activity

“…The enhancement of photocatalytic activity due to a synergistic effect of anatase and rutile mixed phases was supported by other experimental evidences [14]. In fact, a controllable phase composition of TiO 2 could be selectively prepared by changing nucleation mode [13], but an amorphous phase usually accompanied with the crystalline phase [9,15]. It is reported that amorphous TiO 2 is nearly inactive due to the facilitated recombination of the photoformed electron and hole [9,16], but one with large surface area and special microstructures is excepted [17].…”

“…The TiO 2 hydrosols could be facilely prepared by using titanium alkoxides and inorganic salts as precursors [5][6][7][8][9]. However, these TiO 2 hydrosols contained a significant amount of impurities which came from the above-mentioned precursors and peptizing agents, such as hydrochloric acid and nitric acid.…”

Effects of peptizing conditions on nanometer properties and photocatalytic activity of TiO2 hydrosols prepared by H2TiO3

“…1] [ Table 1] To illustrate the trends of changes in crystallinity and particle sizes clearly, the crystallite sizes from XRD results and the average particle sizes from PSD results were calculated and are shown in Table 1. It is clear that the average particle sizes were all much larger than the crystallite sizes due to the slight aggregation of the hydrosol particles, which was mentioned in the pervious work [22]. It was…”

“…In particular, the k values for the CH 3 SH degradation were even three times higher than P-25. Our previous study [22] suggested that the TiO 2 hydrosols in comparison with P-25 powder had smaller particle size, more uniform particle size distribution, larger surface area and pore volume, and better transparency. All of these features would contribute to achieve higher photocatalytic activity.…”

“…Others prepared TiO 2 hydrosols by means of chemical precipitation-peptization process at low temperature (<100 C) using inorganic and organic titanium sources [18][19][20][21]. In our previous works, two types of TiO 2 hydrosols were prepared from titanium sulfate (TiOSO 4 ) and metatitanic acid (H 2 TiO 3 ) by a chemical precipitationpeptization method [22], and it has been found that the TiO 2 hydrosols prepared from H 2 TiO 3 achieved the higher activity for formaldehyde degradation for indoor air purification than other…”