Photocatalytic Reduction of Se(VI) in Aqueous Solutions in UV/TiO₂ System:  Kinetic Modeling and Reaction Mechanism

Abstract

The kinetics of UV/TiO 2 photocatalytic reduction of Se(VI) in the presence of formic acid was investigated. Competitive adsorption models for the Se(VI) and HCOOions onto the same active sites on TiO 2 surface were derived, based on the adsorption of one Se(VI) ion onto two adsorptive sites. The use of the above adsorption models allows for the modeling of the Se(VI) photoreduction rates on the basis of the Langmuir-Hinshelwood (LH) reaction mechanism. The new model was able to represent the experimental data reasonably well, and it supported the experimental observation that the optimum Se(VI) photoreduction rate occurred at the molar adsorption ratio of formate-to-Se(VI) ions of approximately 3:1. A composite rate expression incorporating the effect of catalyst loading was also presented.

Sorption of selenium(VI) onto anatase: Macroscopic and microscopic characterization

“…In addition, the significant sorption capacity of titanium dioxide towards selenium oxyanions has been observed (Saeki and Matsumoto, 1994;Gruebel et al, 1995;Sanuki et al, 1999Sanuki et al, , 2000Li and Deng, 2002;Tan et al, 2002Tan et al, , 2003aWang et al, 2004;Shi et al, 2009;Zhang et al, 2009). However, as far as we know, studies dealing with the elucidation of selenium oxyanion retention mechanisms onto titanium dioxide are still missing.…”

Photocatalytic reduction of Cr(VI) over different TiO2 photocatalysts and the effects of dissolved organic species

“…The application of the TiO 2 photocatalytic reduction process is reported to effectively remove various toxic metal ions, such as Hg(II) [9,10], Se(IV) [11], Se(VI) [12,13], Cd(II) [14,15], Zn(II) [14], Cu(II) [16,17] and Cr(VI) [18][19][20]. Here, the photocatalytic system cannot be used directly to remove a toxic metal from a wastewater, but should be followed by an effective separation method (e.g.…”

Photochemical formation of semiconducting nanostructures

“…Thus, the photoreduction of selenite and selenate ions on the surface of the TiO 2 nanoparticles leads to the formation of TiO 2 /Se [97][98][99][100][101][102] nanostructures. Realization of this reaction in the presence of Cd II and Pb II makes it possible to produce TiO 2 /CdSe [103] and TiO 2 /PbSe [100,101] nanostructures respectively.…”