Preparation Of H₃PW₁₂O₄₀/Ag-TiO₂Composites And Their Photocatalytic Degradation Of Atrazine

In this clissatation, we prepared H3PW12O40and Ag codoped TiO2-based ternary composite photocatalyst H3PW12O40/Ag-TiO2in order to overcome the disadvantages of the semiconductor TiO2and composite materials H3PW12O40/TiO2. The composition, structure, optical absorption property, specific surface area, and surface morphology of the composite catalyst were characterized by the test technologies of atomic absorption (AAS), inductively coupled plasma-atomic emission (ICP-AES), x-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-visible diffuse reflectance (Uv-vis/DRS) and N2adsorption-desorption. The photocatalytic performances of the composite H3PW12O40/Ag-TiO2were evaluated by the degradation of atrazine (AT) under simulated sunlight.Additionally,the best degradation conditions of atrazine was determine through systematical investigation, and the same time the photodegradation mechanism of atrazine was explored.The novel and efficient heterogeneous photocatalytic material, nanocomposite H3PW12O40/TiO2was prepared by the combination of the sol-gel method and hydrothermal treatment at a lower temperature. The characterized results show that the BET surface area of H3PW12O40/Ag-TiO2is159.7m2/g with a microporous (0.44nm) and mesoporous (3.8nm) double aperture anatase phase composite material, in which Kiggen type H3PW12O40evenly is dispersed in the whole TiO2lattice and Ag nanoparticles is evenly distributed on the TiO2surface. The composite H3PW12O40/Ag-TiO2exhibits the strong absorption in both200-380nm (UV region) and400-600nm (visible light), which shows the composite catalyst has apparent visible light response.The optimum reaction conditions of composite H3PW12O40/Ag-TiO2towards photodegrade atrazine are as following:the best loading of Ag and H3PW12O40is0.8wt%and19.7wt%respectively. In100mL aqueous solution of atrazine (5mg/L, pH=3.5), added0.1g catalyst, the degradation rate of atrazine is99.3%after the reaction60min, After the five times’reuse of composite material, its degradation rate is still more than95%. In addition, the experimental results, by adding isopropyl alcohol (hydroxyl inhibitor) and EDTA (hole scavenger), confirmed that the active species·OH radicals plays a decisive role during the process of atrazine degradation in this degradation system.The intermediates of the photocatalytic degradation of atrazine were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS), ion chromatography (IC) and total organic carbon analysis (TOC). Three kinds of degradation pathways were speculated.· OH radical attack i) the side chain of atrazine isopropyl central carbon atom, ii) carbon atom side chain B amino Chung, and iii) Cl-C bond respectively, and then form2,4,6-trihydroxy-1,3,5-triazine (OOOT) through the dealkylation and hydroxylation reactions. Finally, the intermediates were thoroughly oxidized into CO2, H2O, Cl-,NO3-.