改性高岭土的制备、表征及其光催化性能

摘要

通过焙烧和H2SO4浸渍制备了改性高岭土.利用热重-差热(TG-DTA)、扫描电镜(SEM)结合能谱(EDS)、X射线衍射(XRD)、紫外-可见光吸收光谱(UV-Vis)及BET比表面积测定等手段对所获得样品进行了表征.以甲基橙为模型反应物,评价了样品的光催化活性.同未经酸改性的焙烧高岭土相比,改性高岭土的UV-Vis光谱吸收边带产生明显红移.样品具有更高的光吸收效率,促进了其光催化活性.吡啶吸附红外光谱(Py-IR)分析显示,改性高岭土表面具有酸性.当酸浸过程的H2SO4溶液浓度高于30％时,得到的样品同时具有Brφnsted和Lewis酸位.光谱分析结果结合光催化评价结果表明,样品的酸性是影响其光催化性能的主要因素.%In order to develop the cheap and efficient photocatalysts, kaolins were modified through calcination and acid leaching. In succession, the prepared samples were characterized using thermal gravimetric-differential thermal analysis (TG-DTA) , scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis) and BET specific surface area measurements (BET). Methyl orange, used as a model reactant, was degraded under UV light irradiation to evaluate the photocatalytic activities of the prepared samples. From UV-Vis spectroscopy analyses, an obvious increase in the red shift of the absorption edge was observed for the samples treated with acid The acid sites generated during the modification of kaolin were determined through adsorbed pyridine analysis using infrared spectroscopy (Py-IR). Kaolins modified using over 30% H2SO4 contained both Bronsted and Lewis acid sites. Combining the results of photocatalytic experiment with the conclusions of Py-IR and XRD, the acid properties of the prepared samples were the main factors that affected their catalytic activity.