Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India.
J Hazard Mater. 2011 Nov 15;195:214-22. doi: 10.1016/j.jhazmat.2011.08.030. Epub 2011 Aug 16.
Degradation of dimethoate under UV irradiation using TiO(2)/polymer films prepared by the layer-by-layer (LbL) method was investigated. The thin films were fabricated on glass slides and the surface morphology and roughness of the thin films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effect of lamp intensity, catalyst loading in the layers, number of bilayers, pH and initial dimethoate concentration on the degradation of dimethoate was systematically studied. The degradation was monitored using high performance liquid chromatography (HPLC) analysis and total organic carbon (TOC) measurements as a function of irradiation time, to see the change in concentration of dimethoate and mineralization, respectively. Complete degradation of dimethoate was achieved under TiO(2) optimum loading of 4 g/L at an UV irradiation time of 180 min. Increase in the lamp intensity, catalyst loading and number of bilayers increased the rate of degradation. At a pH of 4.62, complete degradation of dimethoate was observed. The degradation efficiency decreased with increase in initial dimethoate concentration. The degradation byproducts were analyzed and confirmed by gas chromatography-mass spectra (GC-MS). Toxicity of the irradiated samples was measured using the luminescence of bacteria Vibrio fischeri after 30 min of incubation and the results showed more toxicity than the parent compound. Catalyst reusability studies revealed that the fabricated thin films could be repeatedly used for up to ten times without affecting the photocatalytic activity of the films. The findings of the present study are very useful for the treatment of wastewaters contaminated with pesticides.
采用层层（LbL）法制备的 TiO2/聚合物薄膜在紫外光照射下对乐果的降解进行了研究。将薄膜制备在载玻片上，并使用 X 射线衍射（XRD）、扫描电子显微镜（SEM）和原子力显微镜（AFM）对薄膜的表面形貌和粗糙度进行了表征。系统研究了灯强度、层中催化剂负载量、双层数、pH 值和初始乐果浓度对乐果降解的影响。使用高效液相色谱（HPLC）分析和总有机碳（TOC）测量作为辐照时间的函数来监测降解，分别观察乐果浓度和矿化的变化。在 TiO2 最佳负载量为 4 g/L 和 UV 照射时间为 180 min 的条件下，乐果可完全降解。增加灯强度、催化剂负载量和双层数均可提高降解速率。在 pH 值为 4.62 时，可观察到乐果的完全降解。初始乐果浓度的增加会降低降解效率。通过气相色谱-质谱（GC-MS）对降解产物进行了分析和确认。通过发光细菌发光(Vibrio fischeri)在 30 分钟的孵育后测量辐照样品的毒性，结果表明其毒性比母体化合物更高。催化剂的可重复使用性研究表明，所制备的薄膜可重复使用十次以上，而不会影响薄膜的光催化活性。本研究的结果对于处理受农药污染的废水非常有用。
