Department of Environmental Sciences and Biotechnology, Hallym University , Chuncheon, Gangwon-do 200-702, South Korea.
Environ Sci Technol. 2014 Nov 18;48(22):13384-91. doi: 10.1021/es504082r. Epub 2014 Oct 31.
The effect of As(III) on the photocatalytic degradation of phenolic pollutants such as 4-chlorophenol (4-CP) and bisphenol A (BPA) in a suspension of platinized TiO2 (Pt/TiO2) was investigated. In the presence of As(III), the photocatalytic degradation of 4-CP and BPA was significantly enhanced, and the simultaneous oxidation of As(III) to As(V) was also achieved. This positive effect of As(III) on the degradation of phenolic pollutants is attributed to the adsorption of As(V) (generated from As(III) oxidation) on the surface of Pt/TiO2, which facilitates the production of free OH radicals ((•)OHf) that are more reactive than surface-bound OH radicals ((•)OHs) toward phenolic pollutants. The generation of (•)OHf was indirectly verified by using coumarin as an OH radical trapper and comparing the yields of coumarin--OH adduct (i.e., 7-hydroxycoumarin) formed in the absence and presence of As(V). In repeated cycles of 4-CP degradation, the degradation efficiency of 4-CP gradually decreased in the absence of As(III), whereas it was mostly maintained in the presence of As(III), which was either initially present or repeatedly injected at the beginning of each cycle. The positive effect of As(III) on 4-CP degradation was observed over a wide range of As(III) concentrations (up to mM levels) with Pt/TiO2. However, a high concentration of As(III) (hundreds of μM) inhibited the degradation of 4-CP with bare TiO2. Therefore, Pt/TiO2 can be proposed as a practical photocatalyst for the simultaneous oxidation of phenolic pollutants and As(III) in industrial wastewaters.
三价砷（As(III)）对负载铂的二氧化钛（Pt/TiO2）悬浮液中酚类污染物（如 4-氯酚（4-CP）和双酚 A（BPA））的光催化降解的影响进行了研究。在存在 As(III)的情况下，4-CP 和 BPA 的光催化降解明显增强，同时也实现了 As(III)的氧化为 As(V)。As(III)对酚类污染物降解的这种积极影响归因于 As(V)（由 As(III)氧化生成）在 Pt/TiO2表面的吸附，这促进了自由羟基自由基（(•)OHf）的生成，(•)OHf 比表面结合的羟基自由基（(•)OHs）对酚类污染物更具反应性。通过使用香豆素作为羟基自由基捕获剂并比较在不存在和存在 As(V)的情况下形成的香豆素-OH 加合物（即 7-羟基香豆素）的产率，间接证实了 (•)OHf 的生成。在重复的 4-CP 降解循环中，在不存在 As(III)的情况下，4-CP 的降解效率逐渐降低，而在存在 As(III)的情况下，降解效率则主要保持不变，As(III)要么最初存在，要么在每个循环开始时重复注入。在 Pt/TiO2 存在的情况下，观察到 As(III)对 4-CP 降解的积极影响在很宽的 As(III)浓度范围内（高达 mM 水平）。然而，高浓度的 As(III)（数百 μM）抑制了裸 TiO2 对 4-CP 的降解。因此，Pt/TiO2 可被提议作为一种实用的光催化剂，用于同时氧化工业废水中的酚类污染物和 As(III)。
