title: Capability of coupled CdSe/TiO(2) for photocatalytic degradation of 4-chlorophenol.
abstract: The photocatalytic process using TiO(2) and coupled semiconductor in the photodegradation reaction of 4-chlorophenol (4-CP) was investigated. Nanosized titanium dioxide powder was synthesized via the sol-gel procedure and modified via the coupled photocatalysts. The microstructural and chemical properties of TiO(2) and coupled CdSe/TiO(2) were also examined. For CdSe/TiO(2) samples, the specific surface area was 7.0 m(2)/g and the deposition proportion of CdSe was approximately 27.6%. In the photocatalysis results, higher photodegradation efficiency of 4-CP was observed at higher pH values. In the UV 254 nm system, the degradation efficiency of 4-CP and TOC with sol-gel produced TiO(2) (TiO(2)(SG)) powder was higher than with commercial TiO(2)(RdH) powder. For the coupled semiconductor system (CdSe/TiO(2)), the apparent first-order rate constants were 1.35 x 10(-2), 4.33 x 10(-2), 2.0 x 10(-3) and 1.9 x 10(-3)min(-1) at the conditions of pH 7 (254 nm), pH 11 (254nm), pH 7 (365 nm), and pH 11 (365 nm). The disappearance of 4-CP under CdSe/TiO(2)(RdH) photoreaction at pH 7 and 365 nm condition is better than that of TiO(2)(RdH) system, with 30% versus 22% 4-CP reduction in 180 min. In the same condition, CdSe/TiO(2)(RdH) provided more photomineralization efficiency than that of TiO(2)(RdH) in terms of TOC reduction. Both 4-CP and TOC reduction were significant for systems illuminated at 254 nm. Considering the direct photolysis effect at 254 nm where 4-CP reduction is near 100% and TOC removal is nil, CdSe/TiO(2)(RdH) exhibits a 50% photomineralization efficiency and a nearly four times faster reaction rate than the single TiO(2)(RdH) semiconductor.
authors.affiliation: Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Shih-Chen
authors.initials: SC
authors.lastname: Lo
authors.forename: Cheng-Fang
authors.initials: CF
authors.lastname: Lin
authors.forename: Chung-Hsin
authors.initials: CH
authors.lastname: Wu
authors.forename: Pin-Hung
authors.initials: PH
authors.lastname: Hsieh
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D002384:Catalysis; D002733:Chlorophenols / Q000737:chemistry* / Q000528:radiation effects; D006863:Hydrogen-Ion Concentration; D008027:Light; D008855:Microscopy, Electron, Scanning; D010777:Photochemistry; D011208:Powders; D018036:Selenium Compounds / Q000737:chemistry*; D012666:Semiconductors; D013056:Spectrophotometry, Ultraviolet; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D019187:Cadmium Compounds; D002733:Chlorophenols; D011208:Powders; D018036:Selenium Compounds; C009495:titanium dioxide; C029107:4-chlorophenol; C058667:cadmium selenide; D014025:Titanium