Degradation of environmental hormone by visible light active double layer photocatalyst

以纯钛金属和Ar+O_2混合气体为原料，采用直流反应溅射法制备了光催化TiO_2薄膜。用紫外光照射在水溶液中制备的TiO_2膜表面，对含有雌性环境激素17β-雌二醇的水溶液进行了降解。紫外灯打开时，用高效液相色谱法测定水溶液中17β-雌二醇的浓度。在初始阶段，随着紫外光强度的增加，降解速率更快。照射时间为6小时后，降解速率达到饱和状态，且与紫外光强度无关。这可能是由于薄膜的表面积和孔隙率不同。为了提高其在太阳光下对可见光的光催化活性，我们制备了由TiO_2和WO_3薄膜组成的双层光催化剂。首先，用反应溅射法在玻璃衬底上沉积WO_3薄膜。我们对沉积的WO_3薄膜进行了退火处理，以改善其结晶度、光学性能和表面微观结构。然后，用反应溅射法在退火后的WO_3薄膜上沉积TiO_2薄膜。在人造太阳光照射下，采用双层光催化剂对17β-雌二醇进行了分解。同时，利用高效液相色谱法测定了17β-雌二醇在人工日光照射下的浓度。光照6小时后，17β-雌二醇水溶液对单层TiO_2膜的降解率为45%，对双层TiO_2膜的降解率为57%。这些结果表明，双层光催化剂中下层WO_3能够有效地对可见光进行活化，并有助于增强上层TiO_2的光催化活性。

We have prepared photocatalytic TiO_2 films by reactive DC sputtering from Ti pure metal and mixture gas of Ar+O_2. The degradation of water solution containing 17β-estradiol well known as female sex environmental hormone was performed under irradiation of UV light to the surface of TiO_2 film set up in the water solution. The concentrations of 17β-estradiol in the water solution were estimated from the measurement of HPLC in intervals during UV light was turned on. At initial stage, the degradation rate was faster with increasing UV light intensity After irradiation period was six hours, the degradation rate was saturated and independent of UV light intensity The degradation rate was different in the films deposited at different sputtering pressure. This may be due to the difference of surface area and porosity in the films.To enhance the photocatalytic activity to visible light in solar light, we have prepared the double-layered photocatalyst composed of TiO_2 and WO_3 films. First, the WO_3 films were deposited on glass substrates by reactive sputtering. We annealed the as-deposited WO_3 films to improve the crystallinity, optical properties and surface microstructure. Then, TiO_2 films were deposited on the annealed WO_3 films by reactive sputtering. The 17β-estradiol was decomposed by the double-layered photocatalyst under irradiation of artificial solar light to the surface of TiO_2 film. The concentrations of 17β-estradiol were also estimated from HPLC, during the artificial solar light was turned on. When six hours passed after the light was turned on, the degradation rates of 17β-estradiol water solution were obtained as a values of 45% for single-layered TiO_2 films, and 57% for the double-layered photocatalyst, respectively.These results suggest that WO_3 under layer in double-layered photocatalyst could be effectively activated for visible light and assist with the enhancement of photocatalytic activity of TiO_2 upper layer.