Lo Shih-Chen, Lin Cheng-Fang, Wu Chung-Hsin, Hsieh Pin-Hung
Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 106, Taiwan.
J Hazard Mater. 2004 Oct 18;114(1-3):183-90. doi: 10.1016/j.jhazmat.2004.08.007.
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.
研究了使用TiO₂和耦合半导体在4-氯苯酚（4-CP）光降解反应中的光催化过程。通过溶胶-凝胶法合成了纳米二氧化钛粉末，并通过耦合光催化剂进行了改性。还研究了TiO₂和耦合的CdSe/TiO₂的微观结构和化学性质。对于CdSe/TiO₂样品，比表面积为7.0 m²/g，CdSe的沉积比例约为27.6%。在光催化结果中，在较高pH值下观察到4-CP具有更高的光降解效率。在UV 254 nm系统中，溶胶-凝胶法制备的TiO₂（TiO₂(SG)）粉末对4-CP和TOC的降解效率高于商业TiO₂（RdH）粉末。对于耦合半导体系统（CdSe/TiO₂），在pH 7（254 nm）、pH 11（254 nm）、pH 7（365 nm）和pH 11（365 nm）条件下，表观一级速率常数分别为1.35×10⁻²、4.33×10⁻²、2.0×10⁻³和1.9×10⁻³ min⁻¹。在pH 7和365 nm条件下，CdSe/TiO₂（RdH）光反应中4-CP的消失情况优于TiO₂（RdH）系统，在180分钟内4-CP的降解率分别为30%和22%。在相同条件下，就TOC降低而言，CdSe/TiO₂（RdH）比TiO₂（RdH）具有更高的光矿化效率。对于在254 nm光照的系统，4-CP和TOC的降低都很显著。考虑到在254 nm处的直接光解效应，此时4-CP的降解接近100%，而TOC去除为零，CdSe/TiO₂（RdH）表现出50%的光矿化效率，反应速率比单一的TiO₂（RdH）半导体快近四倍。
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