摘要
Photocatalytic reduction of hexavalent chromium in wastewater has been widely investigated as an attractive treatment method. In this work, we reported an efficient method for photocatalytic reduction of Cr（VI） over transparent polyvinyl alcohol/titanium dioxide （PVA/TiO2） nanocomposite films under sunlight irradiation. The trans- parent PVA/TiO2 nanocomposite films were prepared by a simple hydrothermal method combined with a solution casting process. The results revealed that the anatase TiO2 nanoparticles with size less than 10 nm were in-situ generated in PVA matrix, which endowed the films with high trans- parency. Photocatalytic reduction of Cr（VI） over PVA/TiO2 nanocomposite films exhibited superior visible light pho- tocatalytic activity. Mechanism investigation demonstrated that the PVA acted not only as a transparent support for TiO2 nanoparticles, but also as holes scavengers simultaneously to improve the separation of photogenerated holes and elec- trons. Meanwhile, the transparent PVA/TiO2 nanocomposite films displayed remarkable stability and excellent recyclabil- ity during multicycle Cr（VI） photoreduction. Furthermore, the PVA/TiO2 nanocomposite films showed selective adsorp- tion ability for Cr（III）, and thus totally removal of Cr（VI） was achieved after photoreduction process.
光催化还原废水中的六价铬离子作为一种具有吸引力的处理方法得到广泛的研究.本文报道了一种利用高透明聚乙烯醇/二氧化钛(PVA/TiO_2)纳米复合薄膜光催化还原Cr(Ⅵ)的方法.通过简单的水热法和溶液涂抹技术制备了PVA/TiO_2纳米复合薄膜,并对其进行了表征.结果表明,原位生成的10 nm左右的锐钛矿型TiO_2纳米粒子均匀分散在PVA基体中,该薄膜在可见光下对Cr(Ⅵ)显示出优异的光催化还原速率.机理研究表明,PVA不仅作为TiO_2纳米粒子的透明载体,而且能有效地促进光致电子和空穴的分离.此外,在多次光催化循环中,PVA/TiO_2纳米复合薄膜展示出良好的稳定性和优异的可循环利用性能,并且该薄膜对还原后的Cr(Ⅲ)表现出良好的选择性吸附,从而可以实现废水中铬离子的彻底去除.
基金
supported by the Joint Program of Beijing Natural Science Foundation and Beijing Academy of Science and Technology (L140005)
the National Natural Science Foundation of China (51203094)
