二氧化锰的晶型控制及其对罗丹明B的降解研究

Study on the crystal form control of manganese dioxide and its degradation for rhodamine B

以高锰酸钾、四水氯化锰和少量浓盐酸为原料,利用水热法实现了MnO_(2)由α晶型向γ晶型再向β晶型的转变,采用X射线衍射(XRD)、X射线光电子能谱(XPS)和扫描电镜(SEM)等表征方法分析了MnO_(2)的晶型转化机理。利用高级氧化法以制备的MnO_(2)为催化剂对罗丹明B(RhB)进行了催化降解研究,探寻了催化效果最好的MnO_(2)晶型并推理出RhB的降解路径。结果表明:随着水热反应时间的延长,α-MnO_(2)逐渐向具有较小隧道尺寸的γ-MnO_(2)、β-MnO_(2)转变;3种晶型的MnO_(2)活化PMS对RhB均具有显著的降解效果,降解效率为α-MnO_(2)>γ-MnO_(2)>β-MnO_(2);紫外-可见吸收光谱分析说明MnO_(2)活化PMS降解RhB的路径为RhB先经过逐步脱乙基化转变成罗丹明、再生成其他有机小分子、CO_(2)和H2O。

The transformation of MnO_(2) fromαform toγform and then toβform was realized by hydrothermal method with potassium permanganate,manganese chloride tetrachloride and a small amount of concentrated hydrochloric acid as the main raw materials.XRD,XPS and SEM methods were used to analyze the crystal transformation of MnO_(2).The catalytic degradation of Rhodamine B(RhB)was studied by advanced oxidation method with the prepared MnO_(2) as catalyst.The MnO_(2) crystal form with best catalytic effect was explored and the degradation mechanism of RhB was deduced.The results showed that with the extension of hydrothermal reaction time,α-MnO_(2) gradually transformed toγ-MnO_(2) andβ-MnO_(2) with smaller tunnel sizes.The three types of MnO_(2)-activated PMS exhibited significant degradation effects on RhB,and the degradation efficiency wasα-MnO_(2)>γ-MnO_(2)>β-MnO_(2).According to UV-visible absorption spectrum analysis,the degradation pathway of RhB by MnO_(2)-activated PMS was that RhB was firstly deethylated to convert into rhodamine,and then transformed into other small molecules,CO_(2) and H 2O.