Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
J Environ Sci (China). 2020 May;91:35-42. doi: 10.1016/j.jes.2019.12.013. Epub 2020 Jan 3.
Much attention has been paid to the pollutant dimethylarsenic acid (DMA), because of its high toxicity even at very low doses. Although TiO photocatalytic oxidation (PCO) is one of the few effective methods for treating DMA-containing water, the efficient decomposition of DMA and simultaneous removal of toxic arsenic species remains a significant but challenging task. Here, defective mesoporous TiO with mixed-phase structure was synthesized and used as both photocatalyst and adsorbent for DMA removal. Due to the reduced band-gap and enhanced separation of photogenerated charge carriers, the oxygen-deficient TiO nanostructures exhibited 4.2 times higher PCO efficiency than commercial TiO (P25). More importantly, the high surface area of the mesoporous TiO provided sufficient active sites for in-situ adsorption and reaction, resulting in the efficient removal of as-formed As(V). Combining the experimental and characterization results, the different roles of reactive species during PCO reactions were clarified. In the presence of hole (h) as the dominant oxidation species, DMA was demethylated and transformed into MMA. Thereafter, MMA was subsequently reduced to As(III) by photo-generated electrons. Superoxide radicals (O) played a significant role in oxidizing As(III) into As(V), which was finally adsorptively removed by the mesoporous TiO.
人们高度关注污染物二甲基砷酸（DMA），因为其即使在很低的剂量下也具有很高的毒性。尽管 TiO 光催化氧化（PCO）是处理含 DMA 水的少数几种有效方法之一，但高效分解 DMA 并同时去除有毒砷物种仍然是一项重大但具有挑战性的任务。在此，合成了具有混合相结构的缺陷介孔 TiO，并将其用作 DMA 去除的光催化剂和吸附剂。由于带隙减小和光生载流子分离增强，氧缺陷 TiO 纳米结构的 PCO 效率比商业 TiO（P25）高 4.2 倍。更重要的是，介孔 TiO 的高表面积为原位吸附和反应提供了足够的活性位点，从而有效地去除了形成的 As(V)。结合实验和表征结果，阐明了在 PCO 反应中不同反应物种的作用。在空穴（h）作为主要氧化物种的存在下，DMA 被脱甲基并转化为 MMA。此后，光生电子将 MMA 进一步还原为 As(III)。超氧自由基（O）在氧化 As(III)为 As(V)方面发挥了重要作用，最后被介孔 TiO 吸附去除。
