| The high toxic and hydrophobic Endocrine Disrupting Chemicals (EDCs) in low concentration cause adverse effects on human health and environment, which has become a hotpot and difficulty in environmental pollution control. Photocatalysis is one of most promising water treatment technologies, which is green and environmentally friendly. Titanium dioxide (TiO2) has been widely used to degrade organic pollutants because TiO2 is with good photocatalytic efficiency, physical and chemical inertness, low cost and nontoxicity. However, the small specific surface area and hydrophilic nature of nanosized TiO2 powders make it have little adsorption capacity for the hydrophobic organic pollutants because of its hydrophilic nature under light illumination. The degradation efficiency of EDCs is good when the concentration of EDCs is high. Howerver, the real concentration of EDCs is μg/L-ng/L and the removal efficiency on bare TiO2 powder is poor. Therefore, it is the important subject that how to prepare the TiO2 composites, which has good adsorption ability for high hydrophobic organic pollutants in low concentration.In this thesis, we combine TiO2 photocatalyst with three kinds of adsorbents. These adsorbents are graphene, organic-inorganic hybrid mesoporous silica and wood charcoal.The four kinds of TiO2 composites with good adsorption capacity were prepared and characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption/desorption measurement, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF), element analysis and Fourier Transform Infrared Spectroscopy (FTIR). The four kinds of TiO2 composites were applied to remove bisphenol A (BPA) by adsorption and photocatalytic degradation synergistically.(1) Because the graphene has strong adsorption ability for BPA and can suppress the combination of photogenerated electron-hole pairs due to its excellent electron conductivity. We prepared the The RGO-P25 nanocomposites using commercial P25 and self-made reduced graphene oxide oxide (GO) as starting materials via a facile hydrothermal reaction in the solvent of ethanol-water after sonication treatment. The mass ratios of RGO to P25 in nanocomposites and the volume ratios of water to ethanol were optimized, and the effect of these factors on the photocatalytic degradation rate contansts of BPA were investigated. When the mass ratio of RGO to commercial TiO2 (P25) was 3.0wt%(P25-3RGO), P25 nanoparticles with size of 20-30 nm were well-dispersed and loaded on the RGO sheets without obvious aggregation. The adsorption removal ratio of BPA over P25-3RGO and P25 were 12.2% and 1.0%, the photocatalytic degradation removal ratio of BPA over P25-3RGO and P25 were 70.4% and 44%, and the total removal ratio of BPA over P25-3RGO and P25 were 82.6% and 45%, respectively. The kinetic rate constant of BPA over P25-3RGO (0.0132min-1)was 2.93 times of that over P25(0.00451min-1).(2)Surface fluorinated TiO2/reduced graphene oxide nanocomposites (denoted as F-TiO2-RGO) were synthesized using TiCl4, HF (40 wt%) and reduced graphene oxide (GO) as starting materials as the starting materials via hydrothermal method. In order to improve the photocatalytic activity of preprared titania, we take advantage of the strong adsorption ability of graphene for BPA, and the adsorbed F ion on the surface of TiO2-RGO and RGO in the composites may reduce the recombination rate of the photo-generated electrons and holes synergistically.The pure anatase TiO2 particles with uniform size (about 30-35 nm) were anchored on the surface of reduced graphene oxide (RGO).The stable Ti-C bond was formed between RGO and TiO2, and about 46.70% removal of oxygen containing groups of GO occurred through the hydrothermal reduction.The HF added during the preparation process can not only prevent phase transformation from anatase to rutile, but also the adsorbed F- ion on the surface of TiO2-RGO surface can improve the photocatalytic activity of F-TiO2-RGO composites. The optimal mass content of RGO and molar ratio of F element to TiO2 in composite was 10.0 wt% and 1:1,respectively. Under optimal degradation condition (5 mg/L BPA initial concentration,1.0 g/L photocatalyst and the solution pH 5.0), the degradation rate constant of BPA over F-TiO2-10RGO (0.01501 min-1) was 3.41 times than that over P25 (0.00440 min-1).(3) TiO2/phenyl functionalized mesoporous silica core/shell photocatalysts (TiO2-Ph-MS) was synthesized by coating a layer of phenyl functionalized mesoporous silica (Ph-MS) on the surface of well-crystallized commercial TiO2 nanoparticles (P25) via sol-gel method. The layer of silica shell in TiO2-Ph-MS photocatalyst can make the TiO2 particles separated in order to reduce the agglomeration of suspended powder TiO2. The core and shell layer of TiO2-Ph-MS composite is 20-30 nm and 2.5nm, respectively. The silica shell possesses mesporous structure and the phenyl groups exist in the pore channel of mesporous silica. The TiO2-Ph-MS composite was applied to remove BPA by adsorption and photocatalytic degradation. The results indicated that the indroduced phenyl group is hydrophobic and has strong adsorption ability for BPA through π-π interaction strong between BPA and phenyl group. The adsorption removal ratio of BPA over the TiO2-Ph-MS (74.8%) was 17.8 times than that over TiO2-MS (4.2%). The photocatalytic experiment results indicated that the degradation rate constant of BPA over TiO2-Ph-MS (0.00169 min-1) was1.57 times than that over TiO2-MS (0.00108 min-1).(4) We take advantage of the strong adsorption ability of wood charcoal (WC)for BPA, the TiO2/wood charcoal composites (TiO2-WC)were prepared by using the wood tissue as charcoal resources and bio-template. The results showed that TiO2-WC composites mimicked wood tissue structure,and titania particles of 15-20 nm were dispersed on the wood charcoal,the mass ratio of anatase to rutile can be adjusted by controlling the calcination temperature because the additional energy resulted from burning wood can make the calcination temperature increase, and thus the anatase TiO2 can be transformed to rutile. The wood charcoal mass ratio in TiO2-WC was 28.20-39.94 wt%, and it is highly aromatic and hydrophobic. The TiO2 in TiO2-WC contained both anatase and rutile TiO2 and mass ratio of anatase to rutile varied from 75:25 to 58.5:41.5. The wood tissue was not only used as raw charcoal resources, and but also as bio-template during the preparation process. The TiO2-WC composites were applied to remove BPA in water. Comparing to extremely low adsorption ability of P25 (1.03%), TiO2-WC-400 and TiO2-WC-450 composites had much higher adsorption ability for BPA, with adsorption removal ratio of 58.67% and 24.96% respectively. Meanwhile, the photocatalytic degradation removal ratio of BPA over TiO2-WC-400 and TiO2-WC-450 was 21.41% and 53.40%, respectively. The photocatalytic activity of TiO2-WC-450 was 1.85 times than that of commercial TiO2 (P25). Compared to the total removal ratio of BPA over P25 (28.80%), the total removal ratio over TiO2-WC-400 and TiO2-WC-450 was as high as 80.08% and 78.32%, respectively. The results showed that BPA could be synergistically removed by adsorption over WC because of strong hydrophobic interaction between WC and BPA, and high photocatalytic activity of TiO2 in TiO2-WC.(5) We compared the adsorption ability, photocatalytic activity, and adsorption/photocatlytic performance synergistically of P25-3RGO, F-TiO2-10RGO, TiO2/Ph-MS, TiO2-WC(TiO2-WC-400、TiO2-WC-450). Moreover, we compared the feasibility of four TiO2 composites from the perspective of the cost. |
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