Li X Z, Liu H, Cheng L F, Tong H J
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, China.
Environ Sci Technol. 2003 Sep 1;37(17):3989-94. doi: 10.1021/es0262941.
Since the suspended TiO2 powder enjoys free contact with UV irradiation in a photoreactor system, it can generally achieve better efficiency than the immobilized TiO2 catalysts. However, the separation and reuse of this catalyst powder from treated water often limit its application in practice. In this study, a new type of TiO2 catalyst called TiO2 microsphere was prepared by a sol-spraying-calcination method, which can easily settle in its aqueous suspensions under gravity. The SEM image of the TiO2 microsphere samples demonstrated that they had an almost spherical shape with a particle size of 30-160 microm, while the XRD analysis indicated that these TiO2 microspheres still had a crystal size of 8.1 nm. Since these TiO2 microspheres had a porous structure with higher specific surface area and pore volume than normal TiO2 powders, they appeared to have strong adsorption ability in its aqueous suspensions. The photocatalytic activity of the TiO2 microspheres was evaluated in the photodegradations of salicylic acid (SA) and sulfosalicylic acid (SSA). The experimental results showed that the reaction rate using the TiO2 microspheres was similar to that using the TiO2 powders in the SA suspensions and even higher than that in the SSA suspensions. Chemical and physical properties of the TiO2 microspheres and powders that are attributed to photoactivity were discussed based on the Langmuir-Hinshelwood kinetic model. The prepared TiO2 microsphere samples were reused in the photooxidation reaction more than 50 times. It was found that there was no significant weakening in their photoactivity and no change in their particle shape. This TiO2 microsphere catalyst can be simply used to conduct an effective photooxidation in its suspension for water and wastewater treatment with ease of recovery from treated water.
由于悬浮的TiO₂粉末在光反应器系统中可与紫外线辐射自由接触，其效率通常比固定化TiO₂催化剂更高。然而，从处理后的水中分离并重复使用这种催化剂粉末往往限制了其在实际中的应用。在本研究中，通过溶胶喷雾煅烧法制备了一种新型TiO₂催化剂——TiO₂微球，其在重力作用下能轻易沉降于水悬浮液中。TiO₂微球样品的扫描电子显微镜图像显示，它们几乎呈球形，粒径为30 - 160微米，而X射线衍射分析表明这些TiO₂微球的晶体尺寸仍为8.1纳米。由于这些TiO₂微球具有多孔结构，比普通TiO₂粉末具有更高的比表面积和孔体积，它们在水悬浮液中似乎具有很强的吸附能力。通过水杨酸（SA）和磺基水杨酸（SSA）的光降解反应评估了TiO₂微球的光催化活性。实验结果表明，在SA悬浮液中使用TiO₂微球的反应速率与使用TiO₂粉末时相似，在SSA悬浮液中甚至更高。基于朗缪尔 - 欣谢尔伍德动力学模型讨论了TiO₂微球和粉末的光活性相关的化学和物理性质。制备的TiO₂微球样品在光氧化反应中重复使用超过50次。结果发现它们的光活性没有明显减弱，颗粒形状也没有变化。这种TiO₂微球催化剂可简单地用于在其悬浮液中进行有效的光氧化，用于水和废水处理，且易于从处理后的水中回收。
