Yin Mingcai, Li Zhaosheng, Kou Jiahui, Zou Zhigang
Eco-materials and Renewable Energy Research Center (ERERC), Nanjing University, Nanjing 210093, P. R. China.
Environ Sci Technol. 2009 Nov 1;43(21):8361-6. doi: 10.1021/es902011h.
Visible light-induced degradation of rhodamine B (RhB) and eosin Y (EO) in a heterogeneous TiO(2) P-25/EO/RhB system was investigated in the present work. The results showed that the photodegradation of RhB is enhanced significantly when EO is introduced into the P-25/RhB system. Under optimal conditions (50 mg P-25, 20 mg L(-1) EO), RhB (4 mg L(-1)) almost decomposed completely after 35 min of visible light irradiation, though EO was photodegraded simultaneously. The possible photodegradation mechanism was studied by the examination of active species HO*, O(2)(-) anions, or dye radical cations through adding their scavengers such as methanol, t-butanol, benzoquinone, EDTA, and the I(-) anion. In addition, the electron paramagnetic resonance (EPR) spin trapping technique was also used to monitor the active oxygen species formed in the photocatalytic process. Combined with the contrastive experiments under different atmospheres (N(2)-purged or air) and in different systems, it can be deduced that dissolved O(2) plays a crucial role in dye photodegradation and the O(2)(-) anion is possibly the major active oxygen species. The low degradation rate with the introduction of EDTA or I(-) indicated that dye radical cations also play a part in photodegradation. Furthermore, except for the dye-sensitized photodegradation on the P-25 surface, reaction in bulk solution also occurs in this system, leading to effective photodegradation of RhB.
本工作研究了在非均相TiO₂ P-25/EO/RhB体系中可见光诱导的罗丹明B（RhB）和曙红Y（EO）的降解。结果表明，将EO引入P-25/RhB体系时，RhB的光降解显著增强。在最佳条件下（50 mg P-25，20 mg L⁻¹ EO），尽管EO同时发生光降解，但在可见光照射35分钟后，RhB（4 mg L⁻¹）几乎完全分解。通过添加甲醇、叔丁醇、苯醌、EDTA和I⁻阴离子等清除剂来检测活性物种HO*、O₂⁻阴离子或染料自由基阳离子，研究了可能的光降解机制。此外，还采用电子顺磁共振（EPR）自旋捕获技术监测光催化过程中形成的活性氧物种。结合不同气氛（N₂吹扫或空气）和不同体系下的对比实验，可以推断溶解的O₂在染料光降解中起关键作用，O₂⁻阴离子可能是主要的活性氧物种。引入EDTA或I⁻时降解速率较低，表明染料自由基阳离子也参与了光降解。此外，除了P-25表面的染料敏化光降解外，该体系中本体溶液中也发生反应，导致RhB的有效光降解。
