Capability of coupled CdSe/TiO2 for photocatalytic degradation of 4-chlorophenol

The photocatalytic process using TiO2 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 TiO2 and coupled CdSe/TiO2 were also examined. For CdSe/TiO2 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 TiO2 (TiO2(SG)) powder was higher than with commercial TiO2(RdH) powder. For the coupled semiconductor system (CdSe/TiO2), 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 (254 nm), pH 7 (365 nm), and pH 11 (365 nm). The disappearance of 4-CP under CdSe/TiO2(RdH) photoreaction at pH 7 and 365 nm condition is better than that of TiO2(RdH) system, with 30% versus 22% 4-CP reduction in 180 min. In the same condition, CdSe/TiO2(RdH) provided more photomineralization efficiency than that of TiO2(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/TiO2(RdH) exhibits a 50% photomineralization efficiency and a nearly four times faster reaction rate than the single TiO2(RdH) semiconductor. (C) 2004 Elsevier B.V. All rights reserved.