Abstract
The work in this thesis focuses on the synthesis of porous materials for wastewater treatment. These novel porous materials have enhanced functional performances than the original ones. There are three projects in this thesis (in chapter 4-6), including Co-doped UiO-66 for enhanced adsorption of organic dyes. Porous g-C3N4 for improved photodegradation of RhB, and g-C3N4/UiO-66 nanocomposites for promoted photodecomposition of RhB.Firstly, a novel CoUiO-66 adsorbent was successfully prepared by doping the Co element into the framework of UiO-66 with an in-situ oil bath synthesis. This modification ensures that the materials retain relatively good crystallinity. The Co-doping has a major impact on the particle size and morphology of the original MOFs. The CoUiO-66 exhibits larger surface area and pore size than pristine UiO-66. Accordingly, the maximum adsorption amount of malachite green (MG) on CoUiO-66 (628.93 mg/g) was significantly larger compared with UiO-66 (343.64 mg/g), which was due to more active adsorption sites. In addition, the CoUiO-66 also showed a superior adsorption capacity on rhodamine B (RhB) (1106.22 mg/g). The CoUiO-66 material could be a promising adsorbent for wastewater treatment.
In the second part, a novel mesoporous g-C3N4 was fabricated with a one-pot route successfully. A series of characterisations revealed that the mesoporous sample maintained the typical structures of g-C3N4. The findings displayed that this mesoporous material had enlarged porosity and optical properties. The mesoporous g-C3N4 (99.60%) exhibited 3.88 times better photocatalytic efficiency than bulk g-C3N4 (25.63%) and a 11.19 times faster reaction rate in the same period.
Thirdly, a new composite of Zr-MOFs (UiO-66) and porous g-C3N4 was prepared through an in-situ preparation route. The photocatalytic properties of these obtained samples were measured through photodegradation of rhodamine B using visible light illumination. The nanocomposites were analysed by a series of characterizations. The photodegradation tests demonstrated that the nanocomposites (CNU-0.5) could achieve almost 100% efficiency in degrading RhB (60 mg/L, 100 mL) in 70 min under visible light. CNU-0.5 showed much better photocatalytic removal efficiency of RhB, which was 6.46 and 10.56 times higher than UiO-66 and g-C3N4. The improved photocatalytic performances were due to large surface area, enhanced optical adsorption, and excellent heterojunction.
Lastly, some recommendations are proposed for future work, such as more experiments could be performed to assess the practical potential. Like the effect of ion strength, easy recovery, and the test in some real water environments. Moreover, more investigations to reveal the mechanism and product in each process could be further studied, which is also very essential for the understanding of the interface mechanism of these reactions and inspiring the direction and relationship for the future design and synthesis of related functional materials.
| Date of Award | 13 Jul 2024 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Tao Wu (Supervisor), Mengxia Xu (Supervisor) & Xiang Luo (Supervisor) |