The synthesis of TiO₂and TiO₂–Pt and their application in the removal of Cr (VI)

Abstract

The deposition of noble metal on titanium dioxide (TiO2) has been considered as an effective strategy to improve the activity of TiO2. In this paper, TiO2 nanoparticles were prepared via a sol-gel route, followed by heat treatment at elevated temperatures. TiO2-Pt catalyst was prepared by deposition of platinum (Pt) on the surface of as-prepared TiO2 nanoparticles. TiO2 and TiO2-Pt were characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, ultraviolet-visible differential reflectance spectra and infrared spectroscopy. TiO2 and TiO2-Pt were used as heterogeneous catalysts for the removal of Cr (VI) under ultraviolet-light illumination. TiO2 prepared at low temperature had smaller particle size and higher specific surface area, and consequently had higher activity on the removal of Cr (VI). The Pt deposited on the surface of TiO2 favoured the separation of photo-produced electrons (e-) and holes (h+), inhibited the recombination of e- and h+, and enhanced Cr (VI) removal. However, its blocking of active sites also inhibited the removal of Cr (VI). The deposition of 1% (wt.%) Pt to TiO2 produced the optimum activity for the removal of Cr (VI). A lower pH favoured the adsorption of Cr (VI) on the surface of TiO2, and correspondingly enhanced the removal of Cr (VI).

Hollow spheric Ag–Ag2S/TiO2 composite and its application for photocatalytic reduction of Cr(VI)

“…Cr(VI) exists in the aqueous solution as Cr 2 O 7 2− . The significantly increased H + concentration would assist the Cr 2 O 7 2− in trapping electrons and therefore favors the reduction of Cr(VI) [27,28]. Moreover, the produced Cr(III) reduced from Cr(VI) would possibly attach on the surface of catalyst as Cr(OH) 3 under alkaline condition, which covers the active sites of catalyst and hinders to some extent the photocatalytic reaction.…”

Synthesis of TiO2 and TiO2‐Pt and Their Application in Photocatalytic Degradation of Humic Acid

“…The photocatalyst of TiO 2 deposited by platinum (TiO 2 -Pt, 1 wt%) was prepared as follows (Fan et al, 2009;Fan et al, 2011): 1) The prepared TiO 2 was distributed in water by means of an ultrasonic apparatus; 2) Excessive methanol and a certain amount of H 2 PtCl 6 were added into the TiO 2 suspension; 3) The pH of this suspension was adjusted to 3.0 by adding NaOH and HClO 4 ; 4) The suspension was magnetically stirred in the dark for approximately 1 hour prior to irradiation to achieve an adsorption-desorption equilibrium. During this process, N 2 was pumped into the suspension; 5) The suspension was irradiated by UV light (120 W) for 5 hours; 6) The suspension sample was filtered, washed, and dried.…”

Pt nanoparticles/TiO2for photocatalytic degradation of phenols in wastewater

“…Special attention has been focused on doping TiO 2 -based materials with noble elements. [16][17][18][19][20][21] Study revealed that Ag dopant accelerates the transformation of anatase TiO 2 to its rutile form, and relatively low Ag concentration (2-5%), results in increase in specific surface areas of the TiO 2 powders. [22] The presence of Ag in crystalline TiO 2 was found to strongly enhance the photocatalytic activity of TiO 2 in various degradation processes.…”