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Wen's Research Group
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Zhang’s research primarily focuses on environmental nanotechnology and interfaces of nanomaterials such as photocatalysis and reactive oxygen species (ROS) generation mechanisms. Recently, we have employed hematite (α-Fe2O3) nanoparticles anchored to graphene oxide (GO) nanosheet (α-Fe2O3@GO) to evaluate the degradation of methylene blue (MB) as a model cationic dye under UV irradiation. The decolorization rate using α-Fe2O3@GO+H2O2+UV was shown to be approximately 2.9 times that of classical Degussa P25 TiO2+UV and 2.4 times that of α-Fe2O3+H2O2+UV. This enhanced decolorization is largely attributed to the unique electrochemical properties (e.g., high electron conductivity) of GO and electrostatic interaction between negatively charged GO with cationic MB. Mineralization pathways of MB were proposed as shown in Fig. 1a based on the intermediates analysis by LC/MS/MS. The toxicity of the photodegradation intermediates was also proved to decrease with the increasing irradiation time.
2. Photo-Fenton reaction for the degradation of BPA
To address the need to widen the working pH, a heterogeneous Fenton catalyst, goethite (α-FeOOH), was investigated by PI Zhang. α-FeOOH has a mesoporous structure with excellent photocatalytic performances and large specific surface area. Different organic acids were added to evaluate the impacts on the photodegradation of BPA and to verify our hypothesis that organic acid complexing with α-FeOOH (ferric-carboxylate complexes) could boost the generation of H2O2 and hydroxyl radicals (•OH). Compared with acetic acid (AA), citric acid (CA), malic acid (MA), and tartaric acidoxalic (TA), oxalic acid (OA) was found to be the most effective in enhancing the photodegradation of BPA. This was due to the formation of ferric-oxalate complexes and •OH radicals in the synergistic interactions of OA and a-FeOOH. Moreover, the addition of OA could significantly extend the working pH from acidic to pH 6.
In addition, we also evaluated the photocatalytic degradation of BPA using ZnFeS. This catalyst was further immobilized on a nickel foam as a solid matrix support to promote BPA degradation and to retain catalyst activity as illustrated in Fig. 1b. The hybridization of ZnFeS catalyst and nickel foam was achieved using the silane cross-linker because of its low cost and high binding strength. The silane cross-linker such as Bis[3-(triethoxysilyl)propyl] Tetrasulfide (TESPT) contain functional groups that can form bonds with organic and inorganic materials and serve as an intermediary binder for organic materials to inorganic materials.
1. Photo-Fenton reaction for dye degradation
Fig.1. Our previous work related photo-Fenton processes: (a) The proposed degradation diagram of MB in α-Fe2O3@GO+H2O2+UV system. (b) Proposed degradation pathways of BPA by ZnFeS/nickel foam.