Degradation of dye pollutants by immobilized polyoxometalate with H2O2 under visible-light irradiation.
A Keggin polyoxometalate (POM, i.e., PW12O40(3-)) and its lacunary derivative are immobilized on an anionic exchange resin through electrostatic interaction at pH 4.6 in an aqueous dispersion. The resin-supported POM thus obtained catalyzes the efficient degradation of cationic dye pollutants in the presence of H2O2 under visible-light irradiation. To evaluate the photocatalytic system, degradation of a rhodamine B (RB) dye was investigated in detail using UV-visible spectroscopy, high performance liquid chromatography, and gas chromatography/mass spectrometry techniques to identify the intermediates and final products. Fluorescence lifetime measurements revealed the electron transfer from the visible-light-excited RB molecules to the POMs. Electron paramagnetic resonance measurements, investigation of the effects of *OH and *OOH scavengers on the photoreaction kinetics, and IR analysis indicated that de-ethylation of RB was due to *OOH radicals, but the decomposition of the conjugated xanthene structure was caused by the peroxo species formed by interaction of H2O2 with the lacunary POM loaded on the resin. A total organic carbon removal of ca. 22% was achieved, and the recycle experiment suggested excellent stability and reusability of the heterogeneous catalyst. On the basis of the experimental results, a photocatalytic mechanism is discussed.
Lei
Pengxiang
P
Key Laboratory of Photochemistry, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China.
Chen
Chuncheng
C
Yang
Juan
J
Wanhong
Ma
M
Zhao
Jincai
J
Zang
Ling
L
D002384:Catalysis; D004396:Coloring Agents / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D004785:Environmental Pollutants; D006861:Hydrogen Peroxide / Q000737:chemistry*; D008027:Light; D017973:Tungsten Compounds / Q000737:chemistry*; D000099294:Polyoxometalates
D004396:Coloring Agents; D004785:Environmental Pollutants; D006861:Hydrogen Peroxide; D017973:Tungsten Compounds; C102296:polyoxometalate I; D000099294:Polyoxometalates