Study On Preparation And Photocatalytic Activity Of Nano-titania/Activated Carbon Composite Materials Based On Self-assembled Monolayers(SAMs)

Titanium dioxide as powder materials, which exist recovery and inactive problems in the application of the photocatalysis. So titanium dioxide fixing on the surface of the porous sorbent carrier, not only could overcome the problems, still could couple the adsorption of porous adsorbent and the photocatalytic of TiO2. Then it would improve the photocatalytic efficiency. On the basement of the modified activated carbon to make SH/AC, which was the self-assembled monolayer of the hydrosulfuryl (SH) as lateral functional group. Take SH/AC as the template to prepare the TiO2/AC composite materials in the system of low temperature liquid phase. With methylene blue (MB) as object, the influence of different experimental conditions, which including activated carbon in sizes、initial concentration of MB, illumination conditions and reuses of the photocatalytic activity of TiO2/AC has been studied. The coupling mechanism of the adsorption of the activated carbon and the photocatalysis of the TiO2was discussed. The main results in the paper were as follows:(1) The functional groups including hydroxyl and carboxyl, ether group on the surface of modified AC. With modified AC for basement, we got self-assembled monolayer the (SH/AC), of which SH as lateral functional groups.(2)The self-assembled monolayers (SH/AC) were adopted as the template for synthesis of the nano-films of TiO2in aqueous system of TiCl4-HCl at low temperature. TiO2/AC composite materials were characterized by X-ray diffraction (XRD), Raman spectrometer (Raman), Infrared Spectrometer (FTIR) and Transmission Electron Microscopy (TEM).The result shows that TiO2/AC was mixed phases of anatase and rutile with about3-6nm in size. And the Ti-O bond vibration peak also existed on the TiO2/AC. The functional groups, such as hydroxyl and carboxyl, phenol ether also remained on the surface of TiO2/AC. The porous could still clearly visible after plating TiO2on the surface AC.(3)The photocatalytic degradation of MB with5mg/L could reach to99.7%and71.19%in ultraviolet and visible light respectively; therefore the catalytic degradation efficiency was higher in the UV light. The photocatalytic degradation rate of TiO2/AC has increased by69.4%and61.1%in the ultraviolet and visible light comparing with one of TiO2in ultraviolet and visible light. Further it was proved that the nano-TiO2/AC photocatalytic degradation of methylene blue which accordant with first-order kinetics. Namely, the apparent reaction rate constant of the photocatalytic degradation of TiO2/AC was about5.18times of one of TiO2.(4) Using FTIR to analysis functional groups of the methylene blue molecular on TiO2/AC from the system of (TiO2/AC-MB)after the ultraviolet irradiation for4h.It showed that the vibration absorption peaks, including C=N、C=S、C-S-C and benzene ring were disappeared. The structure of methylene blue molecular was completely destroyed and mineralized. Therefore TiO2AC has good utilization.(5)The TiO2/AC photocatalytic coupling function model has been suggested. It was illuminated that the strong adsorption of AC and the photocatalytic activity of TiO2in the TiO2/AC composite materials existed coupling enhance mechanism.