Visible light-sensitized S, N and C co-doped polymorphic TiO2 for photocatalytic destruction of microcystin-LR

Motivated from the increasing environmental concerns associated with the formation of cyanotoxins released by cyanobacteria in waters, this study focused on the synthesis and evaluation of visible light-sensitized S, N and C co-doped polymorphic titanium dioxide (CDPM-TiO2) nanoparticles for photocatalytic destruction of microcystin-LR, one of the most common and toxic cyanotoxins. The CDPM-TiO2, containing anatase, brookite and rutile phase, was synthesized using a modified sal-gel method followed by calcination at 300-600 degrees C. Thiourea was utilized as a precursor for the dopants. This work took the initiative to have detailed characterization on the co-doped polymorphic TiO2 by several techniques and utilize the CDPM-TiO2 on cyanotoxin treatment. The results showed that the physicochemical properties of CDPM-TiO2 samples were highly dependent on the calcination temperature. The CDPM-TiO2 sample calcined at 300 degrees C (CDPM300) exhibited better physicochemical characters including higher surface area and stronger photo-absorption in the visible light region. The sulfur dopant was attributed to S6+ species; nitrogen was ascribed to interstitial N; carbon was assigned to the Ti-O-C bond. Moreover, CDPM300 showed highest photocatalytic activity for microcystin-LR destruction under visible light irradiation among all CDPM-TiO2 nanoparticles, which can be considered as a promising demonstration of such visible light-sensitized photocatalysts in the treatment of an important cyanotoxin in water. (C) 2013 Elsevier B.V. All rights reserved.