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Synthesis of visible light sensitized S, N and C co-doped polymorphic TiO2 for Microcystin-LR MC-LR removal
Citation:
Nadagouda, M., G. Zhang, C. Han, K. O'Shea, A. Ismail, S. El-Sheikh, AND D. Dionysiou. Synthesis of visible light sensitized S, N and C co-doped polymorphic TiO2 for Microcystin-LR MC-LR removal. Presented at 2013 International Symposium on Environmental Science and Technology (2013ISEST), Dalian, Liaoning Province, CHINA, June 04 - 07, 2013.
Impact/Purpose:
Water Treatment
Description:
Microcystin-LR (MC-LR) is considered as one of the most widespread and toxic cyanotoxins, which had been discovered to be hepatotoxic, cytotoxic and neurotoxic. It is the only cyanotoxin that has been proposed by Word Health Organization (WHO) for a provisional guideline (1 ppb) in drinking water. Furthermore, many researches had shown that under long term exposure even low concentration of MC-LR can promote liver cancer. Therefore, effective treatment of MC-LR in waters, especially in drinking water, is extremely important for public health and environmental safety. Titanium dioxide (TiO2) photocatalysis, as one of the advanced oxidation technologies (AOT), has been investigated and demonstrated to be effective for MC-LR decomposition. However, conventional TiO2 photocatalyst can only utilize the light in UV range due to its wide band gap, which limits its application with solar light. A lot of efforts have been made in the last two decades in order to overcome this limitation. One of the approaches is doping with impurities. Many non-metals (N, F, S or C) doped TiO2 (mainly anatase phase) had been successfully synthesized with narrowed band gap. Moreover, co-doped TiO2 usually shows higher photocatalytic activity in visible range due to the merits benefited from each dopant. The most of these researches were mostly dealing with anatase phase TiO2 and only a few researches are regarding visible light activated polymorphic TiO2. S, N and C co-doped polymorphic TiO2 as well as its photocatalytic activity have not been reported. In addition, minimum information is available on the co-doped polymorphic TiO2 for cyanotoxin destruction under visible light. In this study, the synthesis of S, N and C co-doped polymorphic titanium dioxide (CD-TiO2) nanoparticles with visible light photocatalytic activity was investigated. . CD-TiO2, containing brookite, anatase and rutile phase, was synthesized using an ambient condition sol process followed by calcination. Thiourea (5%) was utilized as the dopant precursor. The effect of calcination temperature was optimized for developing CD-TiO2 with higher activity. The CD-TiO2 nanoparticles was characterized using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman, Fourier transform infrared (FT-IR) spectroscopy, porosimetry analysis and UV-vis spectrophotometry. The photocatalytic degradation of microcystin-LR (MC-LR) under visible light irradiation using CD-TiO2 nanoparticles was studied. From the experimental results, the CD-TiO2 calcined at 300 0C for 2 hours has outstanding physiochemical properties and the highest photocatalytic activity under visible light irradiation. Moreover, adding thiourea in-situ instead of ex-situ can obtain CD-TiO2 with higher activity.
