Photocatalytic activity of La-doped ZnO for the degradation of monocrotophos in aqueous suspension

La-doped ZnO nanoparticles with different La contents were synthesized and characterized by various sophisticated techniques such as XRD, UV-vis, AFM, XPS, and HR-SEM. The XRD results revealed that La3+ is uniformly dispersed on ZnO nanoparticles in the form of small La2O3 cluster. It was found that the particle size of La-doped ZnO is much smaller as compared to that of pure ZnO and decreases with increasing La loading. Rough and high porous surface of La-doped ZnO was observed by AFM, which is critical for enhancing the photocatalytic activity. The photocatalytic activity of La-doped ZnO in the degradation of monocrotophos (MCP) was studied. The effects of the adsorption of MCP, lights of wavelength, and the solution pH on the photocatalytic activity of La-doped ZnO with different La loading were studied and the results were compared with pure ZnO and pure TiO2. It was observed that the rate of degradation of MCP over La-doped ZnO increases with increasing La loading up to 0.8 wt% and then decreases. It was found that the doping of La in ZnO helps to achieve complete mineralization of MCP within a short irradiation time. Among the catalyst studied, the 0.8 wt% La-doped ZnO was the most active, showing high relative photonic efficiencies and high photocatalytic activity for the degradation of MCP. (c) 2006 Elsevier B.V. All rights reserved.