干燥温度对锰氧化物结构及催化氨氮性能的影响

Effects of Drying Temperature on the Structure of Manganese Oxides and Catalytic Performance of Ammonium

锰氧化物催化氧化法因高效、受季节和温度影响小等优点近年来开始应用于去除饮用水水源中的氨氮。但具有催化性能的活性锰氧化物(MnO_(x))难以可靠形成,这限制了该方法的推广应用。本研究以高锰酸钾为氧化剂,乙酸锰为还原剂,在实验室条件下进行了MnO_(x)的制备并考察了干燥温度对MnO_(x)结构与氨氮催化性能的影响。实验结果表明,未经干燥的湿润样品具有最高的NH_(4)^(+)催化活性,而随着干燥温度从30℃升高至120℃,MnO_(x)催化活性逐步降低并最终丧失。通过SEM、XRD、FTIR和XPS表征发现,干燥处理后,氧化物由合成初期的buserite锰矿最终转变为binessite锰矿,其表面羟基含量下降,且Mn(Ⅲ)向Mn(Ⅳ)大量转变,这可能是导致其氨氮催化活性丧失的重要原因。研究结果将为MnO_(x)催化剂制备方法的建立提供支撑。

In recent years,manganese oxides(MnO_(x))have been used to remove ammonium from drinking water sources by catalytic oxidation,due to the high removal efficiency and little influence by season and temperature.However,it is difficult to reliably form the active MnO_(x)with catalytic capability,which limits the application of this method.In this study,MnO_(x)was prepared under laboratory conditions using potassium permanganate as oxidant and manganese acetate as reductant.The effects of drying temperature on the structure and ammonium catalytic performance of MnO_(x)were investigated.The results showed that the wet samples without drying had the highest NH_(4)^(+) catalytic activity,but with the increase of drying temperature from 30℃to 120℃,the MnO_(x)catalytic activity decreased gradually and finally lost.Through the characterization of SEM,XRD,FTIR and XPS,after drying,the oxide was finally transformed from buserite into binessite,the content of surface hydroxyl decreased,and a large amount of Mn(Ⅲ)changed into Mn(Ⅳ),which might be important reasons for the loss of catalytic activity for ammonium.The results will provide support for the establishment of the preparation method of MnO_(x)catalyst.