【摘要】 三价铁离子对TiO2 光催化降解X3B活性艳红染料具有明显的促进作用 .但是 ,当Fe(III)全部转化为Fe(II)离子以后 ,X3B的降解不再加快 .研究表明 ,Fe(III)捕获表面光生电子是导致X3B降解速率增加的主要原因 ,而Fe(III)光解产生羟基自由基使降解X3B的贡献则相对较小 .由于体系缺乏Fe(III) /Fe(II)循环 ,(Photo) Fenton反应参与X3B降解过程的可能性极小 .X3B和Fe(III)竞争吸附催化剂表面 ,促进了光生电子 -空穴对的分离和转移 .Fe(II)吸附相当微弱 ,这可能是导致Fe(II)难以被表面空穴或其它活性物质重新氧化的原因之一更多还原

【Abstract】 Ferric ions present in an acidic aqueous suspension of TiO 2 can promote significantly the photocatalytic degradation of a textile dye X3B upon UV light irradiation (λ≥320 nm). The initial rate of X3B degradation was observed to increase exponentially with the initial concentration of Fe(III). However, this enhancement disappeared as all ferric species were transferred into ferrous ions, and after that the degradation of X3B proceeded via a regular pathway of photocatalysis. Several control experiments revealed that the beneficial effect of Fe(III) was attributed mainly to electron trapping at the semiconductor surface, whereas the contribution from homogeneous Fe(III) photolysis, capable of producing hydroxyl radicals, was not significant. In the liquid phase, more than 98 2% of Fe(II) was detected, implying that the involvement of (Photo)-Fenton reaction was less possible. On the other hand, the ferrous ion, once produced, exhibited no obvious effect on X3B degradation, but its formation became faster in the presence of X3B, suggesting that hole oxidation of X3B might be involved as well. Both Fe(III) and X3B were adsorbed strongly on the catalyst surface, allowing efficient separation and utilization of the electron-hole pairs, whereas Fe(II) was hardly adsorbed, which probably was one of the reasons that Fe(II) could not be re-oxidized in situ by hole or other reactive species generated in the system. Moreover, the increase in the initial pH from 1 6 to 3 7 did not affect obviously the initiate rate of X3B degradation, but led to significant decrease in the initial rate of Fe(II) formation. Together with the exponential increase of Fe(II) formation rate with initial Fe(III) concentration, the primary evidence suggests that the efficiency of electron trapping by Fe(III), similar to Fe(III) photolysis, is also dependent of ferric species polymerization on the surface. The results obtained in this work will be relevant to the study on Fe-doped photocatalyst.更多还原