Hosseini Seyed Ghorban, Pasikhani Javad Vahabzadeh
Department of Chemistry, Malek Ashtar University of Technology, Tehran, Iran.
Fouman Faculty of Engineering, College of Engineering, University of Tehran, Fouman, Iran.
Environ Technol. 2021 Feb;42(6):914-931. doi: 10.1080/09593330.2019.1649466. Epub 2019 Aug 4.
In recent years, photocatalytic reduction of Cr(VI) to Cr(III) by TiO nanostructures, as a potent environmental technology has attracted a lot of attention. However, several defects including the large band gap energy of TiO, fast photogenerated charge recombination and re-oxidation of Cr(III) restrict their practical application. In this work, the incorporation of TiO nanotubes (TNTs) with magnetic activated carbon (MAC) and photoreduction in the presence of a hole scavenger were studied as a preferable approach. The results revealed that coupling TNTs with 2 wt% MAC can boost the surface area from 89.54 to 307.87 m g as well as decrease the band gap energy from 3.1 to 2.7 eV. As a consequence of the enhancement in textural features and optical properties, TNTs/MAC (2%) led to improvement of photoreduction efficiency (from 47% to 66%) in comparison with the TNTs. Meanwhile, the experiments demonstrated that using 0.2 g TNTs/MAC as an optimal dosage in acidic solution increases the photoreduction efficiency up to 81%. The hole scavenger investigation had a marvellous result. It was found that in the presence of oxalic acid, TNTs/MAC (2%) could reduce 97% of Cr(VI) which it was due to trapping oxidative species and charge-transfer-complex-mediated process. Furthermore, the kinetic study affirmed that the photoreduction follow first-order kinetics and the reaction rate constants by TNTs/MAC (2%) are 1.5 times as great as those of TNTs. Moreover, the reusability tests illustrated TNTs/MAC (2%) has good stability and is active even up to the six runs.
近年来，作为一种有效的环境技术，利用TiO纳米结构将Cr(VI)光催化还原为Cr(III)受到了广泛关注。然而，TiO的大带隙能量、快速的光生电荷复合以及Cr(III)的再氧化等几个缺陷限制了它们的实际应用。在这项工作中，研究了将TiO纳米管（TNTs）与磁性活性炭（MAC）结合以及在存在空穴清除剂的情况下进行光还原作为一种优选方法。结果表明，将TNTs与2 wt%的MAC耦合可以使比表面积从89.54提高到307.87 m²/g，同时将带隙能量从3.1 eV降低到2.7 eV。由于结构特征和光学性质的增强，与TNTs相比，TNTs/MAC（2%）使光还原效率提高（从47%提高到66%）。同时，实验表明，在酸性溶液中使用0.2 g TNTs/MAC作为最佳剂量可将光还原效率提高到81%。空穴清除剂的研究取得了惊人的结果。发现草酸存在时，TNTs/MAC（2%）可还原97%的Cr(VI)，这是由于捕获氧化物种和电荷转移络合物介导的过程。此外，动力学研究证实光还原遵循一级动力学，TNTs/MAC（2%）的反应速率常数是TNTs的1.5倍。而且，可重复使用性测试表明TNTs/MAC（2%）具有良好的稳定性，即使在六次运行后仍具有活性。
